Author name code: hanslmeier
ADS astronomy entries on 2022-09-14
author:"Hanslmeier, Arnold"
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Title: Variation in solar differential rotation and activity in the
period 1964-2016 determined by the Kanzelhöhe data set
Authors: Poljančić Beljan, I.; Jurdana-Šepić, R.; Jurkić, T.;
Brajša, R.; Skokić, I.; Sudar, D.; Ruždjak, D.; Hržina, D.;
Pötzi, W.; Hanslmeier, A.; Veronig, A. M.
Bibcode: 2022A&A...663A..24P
Altcode: 2022arXiv220407396P
Aims: Theoretical calculations predict an increased equatorial
rotation and more pronounced differential rotation (DR) during
the minimum of solar magnetic activity. However, the results of
observational studies vary, some showing less and some more pronounced
DR during the minimum of solar magnetic activity. Our study aims to gain
more insight into these discrepancies.
Methods: We determined
the DR parameters A and B (corresponding to the equatorial rotation
velocity and the gradient of the solar DR, respectively) by tracing
sunspot groups in sunspot drawings of the Kanzelhöhe Observatory
for Solar and Environmental Research (KSO; 1964-2008, for solar
cycles 20-23) and KSO white-light images (2009-2016, for solar cycle
24). We used different statistical methods and approaches to analyse
variations in DR parameters related to the cycle and to the phase of
the solar cycle, together with long-term related variations.
Results: The comparison of the DR parameters for individual cycles
obtained from the KSO and from other sources yield statistically
insignificant differences for the years after 1980, meaning that the
KSO sunspot group data set is well suited for long-term cycle to cycle
studies. The DR parameters A and B show statistically significant
periodic variability. The periodicity corresponds to the solar cycle
and is correlated with the solar activity. The changes in A related
to solar cycle phase are in accordance with previously reported
theoretical and experimental results (higher A during solar minimum,
lower A during the maximum of activity), while changes in B differ
from the theoretical predictions as we observe more negative values
of B, that is, a more pronounced differential rotation during activity
maximum. The main result of this paper for the long-term variations in
A is the detection of a phase shift between the activity flip (in the
1970s) and the equatorial rotation velocity flip (in the early 1990s),
during which both A and activity show a secular decreasing trend. This
indicates that the two quantities are correlated in between 1970 and
1990. Therefore, the theoretical model fails in the phase-shift time
period that occurs after the modern Gleissberg maximum, while in the
time period thereafter (after the 1990s), theoretical and experimental
results are consistent. The long-term variations in B in general yield
an anticorrelation of B and activity, as a rise of B is observed during
the entire time period (1964-2016) we analysed, during which activity
decreased, with the exception of the end of solar cycle 22 and the
beginning of solar cycle 23.
Conclusions: We study for the first
time the variation in solar DR and activity based on 53 years of KSO
data. Our results agree well with the results related to the solar cycle
phase from corona observations. The disagreement of the observational
results for B and theoretical studies may be due to the fact that we
analysed the period immediately after the modern Gleissberg maximum,
where for the phase-shift period, A versus activity also entails a
result that differs from theoretical predictions. Therefore, studies
of rotation versus activity with data sets encompassing the Gleissberg
extremes should include separate analyses of the parts of the data set
in between different flips (e.g., before the activity flip, between
the activity and the rotation flip, and after the rotation flip).
Title: The Solar Activity Monitor Network - SAMNet
Authors: Erdélyi, Robertus; Korsós, Marianna B.; Huang, Xin; Yang,
Yong; Pizzey, Danielle; Wrathmall, Steven A.; Hughes, Ifan G.;
Dyer, Martin J.; Dhillon, Vikram S.; Belucz, Bernadett; Brajša,
Roman; Chatterjee, Piyali; Cheng, Xuewu; Deng, Yuanyong; Domínguez,
Santiago Vargas; Joya, Raúl; Gömöry, Peter; Gyenge, Norbert G.;
Hanslmeier, Arnold; Kucera, Ales; Kuridze, David; Li, Faquan; Liu,
Zhong; Xu, Long; Mathioudakis, Mihalis; Matthews, Sarah; McAteer,
James R. T.; Pevtsov, Alexei A.; Pötzi, Werner; Romano, Paolo; Shen,
Jinhua; Temesváry, János; Tlatov, Andrey G.; Triana, Charles; Utz,
Dominik; Veronig, Astrid M.; Wang, Yuming; Yan, Yihua; Zaqarashvili,
Teimuraz; Zuccarello, Francesca
Bibcode: 2022JSWSC..12....2E
Altcode:
The Solar Activity Magnetic Monitor (SAMM) Network (SAMNet) is a
future UK-led international network of ground-based solar telescope
stations. SAMNet, at its full capacity, will continuously monitor
the Sun's intensity, magnetic, and Doppler velocity fields at
multiple heights in the solar atmosphere (from photosphere to upper
chromosphere). Each SAMM sentinel will be equipped with a cluster of
identical telescopes each with a different magneto-optical filter (MOFs)
to take observations in K I, Na D, and Ca I spectral bands. A subset
of SAMM stations will have white-light coronagraphs and emission line
coronal spectropolarimeters. The objectives of SAMNet are to provide
observational data for space weather research and forecast. The goal
is to achieve an operationally sufficient lead time of e.g., flare
warning of 2-8 h and provide many sought-after continuous synoptic
maps (e.g., LoS magnetic and velocity fields, intensity) of the lower
solar atmosphere with a spatial resolution limited only by seeing or
diffraction limit, and with a cadence of 10 min. The individual SAMM
sentinels will be connected to their master HQ hub where data received
from all the slave stations will be automatically processed and flare
warning issued up to 26 h in advance.
Title: A prediction for the 25th solar cycle maximum amplitude
Authors: Brajša, Roman; Verbanac, Giuli; Bandić, Mario; Hanslmeier,
Arnold; Skokić, Ivica; Sudar, Davor
Bibcode: 2022AN....34313960B
Altcode: 2022arXiv220311293B
The minimum-maximum method, belonging to the precursor class of the
solar activity forecasting methods, is based on a linear relationship
between relative sunspot number in the minimum and maximum epochs of
solar cycles. In the present analysis, we apply a modified version of
this method using data not only from the minimum year, but also from
a couple of years before and after the minimum. The revised 13-month
smoothed monthly total sunspot number data set from Sunspot Index and
Long-term Solar Observations/SIDC is used. Using data for solar cycle
nos. 1-24 the largest correlation coefficient (CC) is obtained when
correlating activity level 3 years before solar cycle minimum with the
subsequent maximum (CC=0.82), independent of inclusion or exclusion
of the solar cycle no. 19. For the next solar maximum of the cycle
no. 25, we predict: Rmax=121±33. Our results indicate that the next
solar maximum (of the cycle no. 25) will be of the similar amplitude
as the previous one, or even something lower. This is in accordance
with the general middle-term lowering of the solar activity after the
secular maximum in the 20th century and consistent with the Gleissberg
period of the solar activity. The reliability of the "3 years before
the minimum" predictor is experimentally justified by the largest CC
and verified with the Student t-test. It is satisfactorily explained
with the two empirical well-known findings: the extended solar cycle
and the Waldmeier effect. Finally, we successfully reproduced the
maxima of the last four solar cycles, nos. 21-25, using the 3 years
before the minimum method.
Title: Prominence instability and CMEs triggered by massive coronal
rain in the solar atmosphere
Authors: Vashalomidze, Z.; Zaqarashvili, T. V.; Kukhianidze, V.;
Ramishvili, G.; Hanslmeier, A.; Gömöry, P.
Bibcode: 2022A&A...658A..18V
Altcode: 2021arXiv211001287V
Context. The triggering process for prominence instability
and consequent coronal mass ejections (CMEs) is not fully
understood. Prominences are maintained by the Lorentz force against
the gravity; therefore, reduction of the prominence mass due to the
coronal rain may cause the change of the force balance and hence
destabilisation of the structures.
Aims: We aim to study the
observational evidence of the influence of coronal rain on the stability
of prominence and subsequent eruption of CMEs.
Methods: We used
the simultaneous observations from the Atmospheric Imaging Assembly
(AIA) of Solar Dynamics Observatory (SDO) and Sun Earth Connection
Coronal and Heliospheric Investigation (SECHHI) of Solar Terrestrial
Relations Observatory (STEREO) spacecrafts from different angles to
follow the dynamics of prominence and to study the role of coronal rain
in their destabilisation.
Results: Three different prominences
observed during the years 2011-2012 were analysed using observations
acquired by SDO and STEREO. In all three cases, massive coronal rain
from the prominence body led to the destabilisation of prominence and
subsequently to the eruption of CMEs. The upward rising of prominences
consisted of the slow and fast rise phases. The coronal rain triggered
the initial slow rise of prominences, which led to the final instability
(the fast rise phase) after 18-28 h in all cases. The estimated mass
flux carried by coronal rain blobs showed that the prominences became
unstable after 40% of mass loss.
Conclusions: We suggest that
the initial slow rise phase was triggered by the mass loss of prominence
due to massive coronal rain, while the fast rise phase (the consequent
instability of prominences) was caused by the torus instability and/or
magnetic reconnection with the overlying coronal field. Therefore, the
coronal rain triggered the instability of prominences and consequent
CMEs. If this is the case, then the coronal rain can be used to predict
the CMEs and hence to improve the space weather predictions.
Title: Revealing the structure of the lensed quasar Q
0957+561. I. Accretion disk size
Authors: Fian, C.; Mediavilla, E.; Jiménez-Vicente, J.; Motta,
V.; Muñoz, J. A.; Chelouche, D.; Goméz-Alvarez, P.; Rojas, K.;
Hanslmeier, A.
Bibcode: 2021A&A...654A..70F
Altcode: 2021arXiv210805212F
Aims: We aim to use signatures of microlensing induced by stars
in the foreground lens galaxy to infer the size of the accretion disk in
the gravitationally lensed quasar Q 0957+561. The long-term photometric
monitoring of this system (which so far has provided the longest
available light curves of a gravitational lens system) permits us to
evaluate the impact of uncertainties on our recently developed method
(controlled by the distance between the modeled and the experimental
magnitude difference histograms between two lensed images), and thus
to test the robustness of microlensing-based disk-size estimates.
Methods: We analyzed the well-sampled 21-year GLENDAMA optical
light curves of the double-lensed quasar and studied the intrinsic
and extrinsic continuum variations. Using accurate measurements for
the time delay between the images A and B, we modeled and removed the
intrinsic quasar variability, and from the statistics of microlensing
magnifications we used a Bayesian method to derive the size of the
region emitting the continuum at λrest = 2558 Å.
Results: Analysis of the Q 0957+561 R-band light curves show a slow
but systematic increase in the brightness of the B relative to the A
component during the past ten years. The relatively low strength of
the magnitude differences between the images indicates that the quasar
has an unusually big optical accretion disk of half-light radius:
R1/2 = 17.6±6.1 √(M/0.3 M⊙) lt-days.
Title: Microlensing of the broad emission lines in 27 gravitationally
lensed quasars. Broad line region structure and kinematics
Authors: Fian, C.; Mediavilla, E.; Motta, V.; Jiménez-Vicente, J.;
Muñoz, J. A.; Chelouche, D.; Hanslmeier, A.
Bibcode: 2021A&A...653A.109F
Altcode: 2021arXiv210706227F
Aims: We aim to study the structure and kinematics of the broad
line region (BLR) of a sample of 27 gravitationally lensed quasars with
up to five different epochs of observation. This sample is composed of
∼100 spectra from the literature plus 22 unpublished spectra of 11
systems.
Methods: We measure the magnitude differences in the
broad emission line (BEL) wings and statistically model the distribution
of microlensing magnifications to determine a maximum likelihood
estimate for the sizes of the C IV, C III], and Mg II emitting
regions.
Results: The BELs in lensed quasars are expected to be
magnified differently owing to the different sizes of the regions from
which they originate. Focusing on the most common BELs in our spectra
(C IV, C III], and Mg II), we find that the low-ionization line Mg II is
only weakly affected by microlensing. In contrast, the high-ionization
line C IV shows strong microlensing in some cases, indicating that
its emission region is more compact. Thus, the BEL profiles are
deformed differently depending on the geometry and kinematics of the
corresponding emitting region. We detect microlensing in either the
blue or the red wing (or in both wings with different amplitudes) of C
IV in more than 50% of the systems and find outstanding asymmetries in
the wings of QSO 0957+561, SDSS J1004+4112, SDSS J1206+4332, and SDSS
J1339+1310. This observation indicates that the BLR is, in general,
not spherically symmetric and supports the existence of two regions in
the BLR, one insensitive to microlensing and another that only shows
up when it is magnified by microlensing. Disregarding the existence
of these two regions, our estimate for Mg II, R1/2 =
67.3−15.7+3.8 √(M/M⊙) light-days,
is in good agreement with previous results from smaller samples, while
we obtain smaller sizes for the C III] and CIV lines, R1/2
= 31.0−4.0+1.9 √(M/M⊙)
light-days and R1/2 = 15.5−3.9+0.8
√(M/M⊙) light-days, respectively.
Title: Revealing the structure of the lensed quasar Q 0957+561:
III. SMBH mass via gravitational redshift
Authors: Fian, C.; Mediavilla, E.; Jiménez-Vicente, J.; Motta, V.;
Muñoz, J. A.; Chelouche, D.; Hanslmeier, A.
Bibcode: 2021arXiv210711791F
Altcode:
We intend to use the impact of microlensing on the Fe III emission line
blend along with a measure of its gravitational redshift to estimate the
mass of the quasar's central supermassive black hole (SMBH). We fit the
Fe III feature in multiple spectroscopic observations between 2008 and
2016 of the gravitationally lensed quasar Q 0957+561 with relatively
high signal-to-noise ratios (at the adequate wavelength). Based on the
statistics of microlensing magnifications, we used a Bayesian method
to derive the size of its emitting region. The Fe III spectral feature
appears systematically redshifted in all epochs of observation by a
value of 17 angstroms on average. We find clear differences in the
shape of the Fe III line blend between images A and B. Measuring the
strength of those magnitude differences, we conclude that this blend
may arise from a region of half-light radius of 15 lt-days, which is in
good agreement with the accretion disk dimensions for this system. We
obtain a mass for the central SMBH of (1.5 +/- 0.5) x 10^9 solar masses,
consistent within uncertainties with previous mass estimates based on
the virial theorem. The relatively small uncertainties in the mass
determination (< 35%) make this method a compelling alternative
to other existing techniques (e.g., the virial plus reverberation
mapping based size) for measuring black hole masses. Combining the Fe
III redshift-based method with the virial, we estimate a virial factor
in the 1.2 to 1.7 range for this system.
Title: Kink instability of triangular jets in the solar atmosphere
Authors: Zaqarashvili, T. V.; Lomineishvili, S.; Leitner, P.;
Hanslmeier, A.; Gömöry, P.; Roth, M.
Bibcode: 2021A&A...649A.179Z
Altcode: 2021arXiv210209952Z
Context. It is known that hydrodynamic triangular jets (i.e. the
jet with maximal velocity at its axis, which linearly decreases at
both sides) are unstable to anti-symmetric kink perturbations. The
inclusion of the magnetic field may lead to the stabilisation of the
jets. Jets and complex magnetic fields are ubiquitous in the solar
atmosphere, which suggests the possibility of the kink instability in
certain cases.
Aims: The aim of the paper is to study the kink
instability of triangular jets sandwiched between magnetic tubes (or
slabs) and its possible connection to observed properties of the jets in
the solar atmosphere.
Methods: A dispersion equation governing
the kink perturbations is obtained through matching of analytical
solutions at the jet boundaries. The equation is solved analytically
and numerically for different parameters of jets and surrounding
plasma. The analytical solution is accompanied by a numerical simulation
of fully non-linear magnetohydrodynamic (MHD) equations for a particular
situation of solar type II spicules.
Results: Magnetohydrodynamic
triangular jets are unstable to the dynamic kink instability depending
on the Alfvén Mach number (the ratio of flow to Alfvén speeds) and
the ratio of internal and external densities. When the jet has the
same density as the surrounding plasma, only super-Alfvénic flows are
unstable. However, denser jets are also unstable in a sub-Alfvénic
regime. Jets with an angle to the ambient magnetic field have much
lower thresholds of instability than field-aligned flows. Growth
times of the kink instability are estimated to be 6−15 min for type
I spicules and 5−60 s for type II spicules matching with their
observed lifetimes. The numerical simulation of full non-linear
equations shows that the transverse kink pulse locally destroys
the jet in less than a minute in type II spicule conditions.
Conclusions: Dynamic kink instability may lead to the full breakdown
of MHD flows and consequently to an observed disappearance of
spicules. Movies associated to Fig. 9 are available at https://www.aanda.org
Title: The impact of stellar flares and superflares on life: first
experiments to reveal the UV surface habitability of exoplanets
Authors: Abrevaya, X.; Oppezzo, O. J.; Odert, P.; Leitzinger, M.;
Patel, M.; Luna, G. J. M.; Forte Giacobone, A. F.; Hanslmeier, A.
Bibcode: 2021BAAS...53c1219A
Altcode:
The increasing discovery of exoplanets in the last decades has boosted
the search for life in the universe, and particularly the studies for
the characterization of planetary habitability. Stellar radiation is one
of the fundamental factors to be studied in this context, as it can have
an influence on the planetary environment and can be a constraint for
life through direct or indirect effects. Depending on the atmospheric
composition and pressure, UV radiation wavelengths (200-400 nm) can
reach the surface of the planets and could be harmful to life. Moreover,
it is unknown if UV fluxes from very energetic events as flares and
superflares could limit the surface habitability of a planet. Previous
studies have analyzed the UV surface environments on exoplanets to
study the impact of UV radiation on life, however, this has only been
approached partially from a theoretical point of view (i.e. modeling
of the biological impact of UV). In a recent interdisciplinary study,
we experimentally determined through laboratory experiments and for
the first time, the impact that flares and superflares could have on
microorganisms. We found out that previous studies underestimated the
chances of "life as we know it" to thrive under these conditions. In
this talk, I will describe the drawbacks of methodologies used in
previous studies, and I will present our latest results about the impact
of flares and superflares on potential microbial life in exoplanets
aimed to study UV surface habitability. These efforts are part of the
EXO-UV program, an international interdisciplinary collaboration that
seeks to expand the characterization of UV radiation environments
through experimental approaches.
Title: Upper limits on the CME frequency of solar-like stars
Authors: Leitzinger, Martin; Odert, Petra; Greimel, Robert; Vida,
Krisztian; Kriskovics, Levente; Guenther, Eike W.; Korhonen, Heidi;
Koller, Florian; Kövari, Zsolt; Hanslmeier, Arnold; Lammer, Helmut
Bibcode: 2021csss.confE..93L
Altcode:
In the last years efforts have been made to determine parameters
of stellar coronal mass ejections (CMEs), on the one hand via
acquiring dedicated observing time at telescopes and on the other
hand via searching data archives. Here we present a search for CMEs on
solar-like stars using optical spectroscopic data from the Polarbase
and ESO HARPS Phase 3 archives. For detecting stellar CMEs we use
the signature of filaments/prominences being ejected from a star,
which is Doppler-shifted emission/absorption occurring on the blue
side of Balmer lines, as filaments/prominences are very pronounced
in Balmer lines. Using more than 3700 hours of on-source time of 425
stars we aim for a statistical determination of CME parameters, such
as projected velocity, occurrence frequency, and mass. The target
stars are nearby objects and consist of F-K main-sequence stars of
various ages. We find no signature of CME activity and a very low
level of flaring activity (10 out of 425 stars). Comparing this to
results from the Kepler mission, the fraction of flaring stars is
more or less consistent. Comparing extrapolated Hα flare rates to
the sparse detection of flares reveals that we could have detected
more flares. We therefore determined the full-disk Hα signal of one
of the strongest solar flares in the last solar cycles. This showed
that we would have needed data with higher S/N to detect such a flare
in our data. Finally, we compared the observed upper limits of CME
rates of our target stars to modelled CME rates. The modelled CME
rates are mostly below the observationally determined upper limits,
indicating that most on-source times per star were too short to detect
stellar CMEs with this method. The sparse detection of flares and the
non-detection of CMEs may be explained by biases naturally introduced
by using archival data, as well as a a low level of activity of the
target stars. We conclude with a short report on ongoing and future
activities of the search for stellar CMEs.
Title: Revealing peculiar exoplanetary shadows from transit light
curves
Authors: Arkhypov, O. V.; Khodachenko, M. L.; Hanslmeier, A.
Bibcode: 2021A&A...646A.136A
Altcode:
Context. Until now the search of peculiar exoplanetary shadows,
particularly those caused by exorings, was focused on the detection of
a second-order photometric difference between the ringed and ringless
(circular) transiting shadows. Both scenarios involved the parameter
fitting to approximate the corresponding transit light curves (TLCs). As
a result, the searched difference was extremely difficult to detect
in the noise of the real transit photometry signals.
Aims: In
this work, we look for photometric manifestations of a non-spherical
obscuring matter (e.g., exorings) around different exoplanets, mainly
hot Jupiters, using a principally new approach.
Methods: We
used the transit parameters provided in Kepler database from the NASA
Exoplanet Archive, where the fitting of the TLCs gives consistent sets
of parameters for the transiting objects, assuming their spherical
shape. At the same time, the semimajor axes, expressed in units of the
stellar radii (initially, also a subject of the fitting), finally appear
to be replaced by the calculated values according the Kepler's third law
and known stellar radii and surface gravity that have been determined
through other methods. In the most typical case of a spherical
transiting planet, such a replacement does not break the consistency
of the whole parameter set. However, in the case of a non-spherical
transiter and its non-circular shadow, the real (i.e., calculated
according physics) value of the orbital semimajor axis could become
inconsistent with the rest of the transit parameter set defined with
the standard fitting procedure. The search for such inconsistencies,
manifested as the difference between the simulated and observed transit
duration, constitutes one of the main goals of this work. Moreover,
we elaborate on a particular technique to gain information about the
shape of planetary shadow, using the derivatives of the TLC during the
ingress and egress phases.
Results: We checked the TLCs of 21
hot Jupiters and 2 hot Neptunes. The consistent transit parameters and
quasi-circular shadows were found for 11 objects. The analysis of the
TLCs of five of the objects is complicated due to the noise problems,
leading to the instability of solutions and deformation of shadows
due to the low resolution of the derivatives. The remaining seven
objects were formally qualified as peculiar outliers and among them,
the planets Kepler-45b and Kepler-840b appear to be the most intriguing
targets, with the most significant inconsistency of the parameter sets
and the shadows elongated along their orbital path.
Conclusions:
We propose a new method for probing of planetary shape that confirms
the circular transiting shadows for the majority of objects on
the considered list. However, several objects exhibiting peculiar
shadows have been discovered. These finds could be interpreted in
terms of planetary dusty envelopes or exorings. The obtained results
and elaborated methodology are relevant in the context of today's
photometry space missions, such as TESS, CHEOPS, and others.
Title: Variability of transit light curves of Kepler objects of
interest
Authors: Arkhypov, O. V.; Khodachenko, M. L.; Hanslmeier, A.
Bibcode: 2020A&A...638A.143A
Altcode:
Context. Hitherto, the study of exoplanetary transit timing and
duration variability has supposed transit light curves (TLCs) to be
symmetric, suggesting a priori a spherical shape for the transiting
object, for example, an exoplanet. As a result, the independent
positions of transit borders are unknown. However, the borders of
TLCs are most sensitive to the presence of exo-rings and/or dust
formations of great interest.
Aims: For the first time we
check for a timing variability of independently treated borders
of transits of different types of exoplanets.
Methods: Using
quadratic approximation for the start-, end-, and minimum parts of the
long-cadence TLCs from the Kepler mission archive after their whitening
and phase folding, we find the corresponding transit border timings:
Δts, Δte, respectively, and the TLC minimum time
Δtm. These parameters were found separately for each folded
TLC constructed in the consequent non-overlapping time-windows with the
respective medium time tw. Temporal and cross-correlation
analysis of the obtained series of Δts(tw),
Δte(tw), and Δtm(tw)
were applied for the detection and diagnostics of variability of transit
borders and TLC asymmetry.
Results: Among the considered TLCs of
98 Kepler objects of interest (KOIs), 15 confirmed giant exoplanets
and 5 objects with still debatable status (probably non-planets)
show variations in their transit timing parameters at timescales from
≈400 to ≳1500 days. These variations are especially well manifested
as an anti-correlation between Δts and Δte,
indicating variability in the dimensions of transiting shadows,
especially along their trajectories. There are also objects with well
pronounced oscillations of transit border timing and asymmetry.
Conclusions: The discovered variability of transit timing is
important as an indicator of large-scale non-stationary processes
in the atmospheres of KOIs, as well as dust and aerosol generation
in their upper layers and in their close vicinity. These findings
highlight the need for a dedicated and detailed study.
Title: The UV surface habitability of Proxima b: first experiments
revealing probable life survival to stellar flares
Authors: Abrevaya, X. C.; Leitzinger, M.; Oppezzo, O. J.; Odert, P.;
Patel, M. R.; Luna, G. J. M.; Forte Giacobone, A. F.; Hanslmeier, A.
Bibcode: 2020MNRAS.494L..69A
Altcode: 2020arXiv200300984A; 2020MNRAS.tmpL..36A
We use a new interdisciplinary approach to study the UV surface
habitability of Proxima b under quiescent and flaring stellar
conditions. We assumed planetary atmospheric compositions based on
CO2 and N2 and surface pressures from 100 to
5000 mbar. Our results show that the combination of these atmospheric
compositions and pressures provide enough shielding from the most
damaging UV wavelengths, expanding the `UV-protective' planetary
atmospheric compositions beyond ozone. Additionally, we show that
the UV radiation reaching the surface of Proxima b during quiescent
conditions would be negligible from the biological point of view,
even without an atmosphere. Given that high UV fluxes could challenge
the existence of life, then, we experimentally tested the effect
that flares would have on microorganisms in a `worst case scenario'
(no UV-shielding). Our results show the impact that a typical flare
and a superflare would have on life: when microorganisms receive very
high fluences of UVC, such as those expected to reach the surface of
Proxima b after a typical flare or a superflare, a fraction of the
population is able to survive. Our study suggests that life could cope
with highly UV irradiated environments in exoplanets under conditions
that cannot be found on Earth.
Title: A census of coronal mass ejections on solar-like stars
Authors: Leitzinger, M.; Odert, P.; Greimel, R.; Vida, K.; Kriskovics,
L.; Guenther, E. W.; Korhonen, H.; Koller, F.; Hanslmeier, A.;
Kővári, Zs; Lammer, H.
Bibcode: 2020MNRAS.493.4570L
Altcode: 2020MNRAS.tmp..472L; 2020arXiv200204430L
Coronal mass ejections (CMEs) may have major importance for planetary
and stellar evolution. Stellar CME parameters, such as mass and
velocity, have yet not been determined statistically. So far only a
handful of stellar CMEs has been detected mainly on dMe stars using
spectroscopic observations. We therefore aim for a statistical
determination of CMEs of solar-like stars by using spectroscopic
data from the ESO phase 3 and Polarbase archives. To identify
stellar CMEs, we use the Doppler signal in optical spectral lines
being a signature of erupting filaments that are closely correlated
to CMEs. We investigate more than 3700 h of on-source time of in
total 425 dF-dK stars. We find no signatures of CMEs and only few
flares. To explain this low level of activity, we derive upper limits
for the non-detections of CMEs and compare those with empirically
modelled CME rates. To explain the low number of detected flares,
we adapt a flare power law derived from EUV data to the H α regime,
yielding more realistic results for H α observations. In addition,
we examine the detectability of flares from the stars by extracting
Sun-as-a-star H α light curves. The extrapolated maximum numbers of
observable CMEs are below the observationally determined upper limits,
which indicates that the on-source times were mostly too short to
detect stellar CMEs in H α. We conclude that these non-detections
are related to observational biases in conjunction with a low level
of activity of the investigated dF-dK stars.
Title: Observed versus modelled stellar CME rates
Authors: Leitzinger, Martin; Odert, Petra; Vida, Krisztian;
Kriskovics, Levente; Guenther, Eike W.; Korhonen, Heidi; Greimel,
Robert; Hanslmeier, Arnold; Lammer, Helmut
Bibcode: 2020IAUS..345..246L
Altcode:
Stellar coronal mass ejections (CMEs) may play an important role in
stellar and planetary evolution, therefore the knowledge on parameter
distributions of this energetic activity phenomenon is highly
relevant. During the last years several attempts have been made to
detect stellar CMEs of late-type main-sequence and pre main-sequence
stars from dedicated optical spectroscopic observations. Up to now
only a handful of distinct stellar CME detections are known which
contradicts the results from stellar CME modelling, which predict higher
CME rates. We report on dedicated ongoing and future observational
attempts to detect stellar CMEs and discuss the observational results
with respect to the results from stellar CME modelling.
Title: What Is Chaos?
Authors: Hanslmeier, Arnold
Bibcode: 2020csc..book....1H
Altcode:
No abstract at ADS
Title: The Chaotic Solar Cycle
Authors: Hanslmeier, Arnold
Bibcode: 2020csc..book.....H
Altcode:
No abstract at ADS
Title: The BRITE-SONG of Aldebaran - stellar music in three voices
Authors: Beck, P. G.; Kuschnig, R.; Houdek, G.; Kallinger, T.;
Weiss, W. W.; Palle, P. L.; Grundahl, F.; Hatzes, A.; Parviainen, H.;
Allende Prieto, C.; Deeg, H. J.; Jiménez, A.; Mathur, S.; Garcia,
R. A.; White, T. R.; Bedding, T. R.; Grossmann, D. H.; Janisch, S.;
Zaqarashvili, T.; Hanslmeier, A.; Zwintz, K.
Bibcode: 2020svos.conf...75B
Altcode: 2020arXiv200104912B
Solar-like oscillations in red-giant stars are now commonly detected
in thousands of stars with space telescopes such as Kepler. Parallel
radial-velocity and photometric measurements would help us understand
better the physics governing the amplitudes of solar-like oscillators,
but most stars targetted for space photometry are too faint for
light-demanding ground-based spectroscopy. The BRITE-Constellation
provides a unique opportunity of monitoring in two colours the flux
variations of bright luminous red giants. Those stars are also bright
enough to be monitored with high-resolution spectrographs on small
telescopes, such as the SONG Network. This contribution provided a
first overview of our comprehensive, multi-year campaign to use both
BRITE and SONG to characterize Aldebaran (one of the brightest red
giants in the sky) seismically. Because luminous red giants can be
seen at large distances, when characterized well they will serve as
valuable benchmark stars for Galactic archeology.
Title: KIC 9163796 - a benchmark binary for age determination
Authors: Grossmann, D. H.; Beck, P. G.; Hanslmeier, A.
Bibcode: 2020svos.conf..351G
Altcode:
Binary systems constitute a valuable tool in astrophysics for gaining
a deeper understanding of stellar evolution and determining stellar
ages. That is particularly true for the double-lined binary KIC 9163796,
which has a mass ratio of almost unity but varies significantly in
temperature, luminosity and Lithium abundance. This paper outlined our
approach to generate a combined stellar model for it using the MESA
stellar-evolution code. By combining the available observational data
with the models we derived, we aimed to find the best-fitting models
for both components and to extrapolate the system's age from them.
Title: Towards astrobiological experimental approaches to study
planetary UV surface environments
Authors: Abrevaya, Ximena C.; Leitzinger, Martin; Oppezzo, Oscar
J.; Odert, Petra; Luna, G. Juan M.; Patel, Manish; Forte-Giacobone,
Ana F.; Hanslmeier, Arnold
Bibcode: 2020IAUS..345..222A
Altcode:
The stellar ultraviolet radiation (UVR) has been studied in
the last decade and has been found to be an important factor to
determine the habitability of planetary surfaces. It is known that
UVR can be a constraint for life. However, most of the studies
of UVR and habitability have missed some fundamental aspects: i)
Accurate estimation of the planetary atmospheric attenuation, ii) The
biological inferences used to represent the impact of the stellar UVR
on life are theoretical and based on the action spectrum (for DNA or
microorganisms) or considering parameters as the "lethal dose" obtained
from non-astrobiological experiments. Therefore, the conclusions reached
by previous studies about the UVR habitability of planetary bodies may
be inaccurate. In this work, we propose how to address these studies
in a more accurate way through an interdisciplinary approach that
combines astrophysics, microbiology, and photobiology and by the use
of specially designed laboratory experiments.
Title: Einführung in Astronomie und Astrophysik
Authors: Hanslmeier, Arnold
Bibcode: 2020eiaa.book.....H
Altcode:
No abstract at ADS
Title: Dusty phenomena in the vicinity of giant exoplanets
Authors: Arkhypov, O. V.; Khodachenko, M. L.; Hanslmeier, A.
Bibcode: 2019A&A...631A.152A
Altcode:
Context. Hitherto, searches for exoplanetary dust have focused on
the tails of decaying rocky or approaching icy bodies only at short
circumstellar distances. At the same time, dust has been detected
in the upper atmospheric layers of hot jupiters, which are subject
to intensive mass loss. The erosion and/or tidal decay of hypothetic
moonlets might be another possible source of dust around giant gaseous
exoplanets. Moreover, volcanic activity and exozodiacal dust background
may additionally contribute to exoplanetary dusty environments.
Aims: In the present study, we look for photometric manifestations
of dust around different kinds of exoplanets (mainly giants).
Methods: We used linear approximation of pre- and post-transit parts
of the long-cadence transit light curves (TLCs) of 118 Kepler objects
of interest after their preliminary whitening and phase-folding. We
then determined the corresponding flux gradients G1 and
G2, respectively. These gradients were defined before
and after the transit border for two different time intervals:
(a) from 0.03 to 0.16 days and (b) from 0.01 to 0.05 days,
which correspond to the distant and adjoining regions near the
transiting object, respectively. Statistical analysis of gradients
G1 and G2 was used for detection of possible dust
manifestation.
Results: It was found that gradients G1
and G2 in the distant region are clustered around zero,
demonstrating the absence of artifacts generated during the light curve
processing. However, in the adjoining region, 17 cases of hot jupiters
show significantly negative gradients, G1, whereas the
corresponding values of G2 remain around zero. The analysis
of individual TLCs reveals the localized pre-transit decrease of flux,
which systematically decreases G1. This effect was reproduced
with the models using a stochastic obscuring precursor ahead of the
planet.
Conclusions: Since only a few TLCs show the presence
of such pre-transit anomalies with no analogous systematic effect
in the post-transit phase, we conclude that the detected pre-transit
obscuration is a real planet-related phenomenon. Such phenomena may
be caused by dusty atmospheric outflows or background circumstellar
dust compressed in front of the mass-losing exoplanet, the study of
which requires dedicated physical modeling and numeric simulations. Of
certain importance may be the retarding of exozodiacal dust relative to
the planet by the Poynting-Robertson effect leading to dust accumulation
in electrostatic or magnetic traps in front of the planet.
Title: Stellar CMEs from an observational point of view
Authors: Leitzinger, Martin; Odert, Petra; Vida, Krisztian; Koller,
Florian; Veronig, Astrid; Korhonen, Heidi; Guenther, Eike; Hanslmeier,
Arnold; Temmer, Manuela; Dissauer, Karin; Greimel, Robert; Kriskovics,
Levente; Lammer, Helmut
Bibcode: 2019EGUGA..21.6786L
Altcode:
Stellar activity is mainly characterized by the high energy phenomena
such as outbreaks of radiation (flares) and sporadic expulsions
of particles into the astrosphere termed coronal mass ejections
(CMEs). Both phenomena are known to cause space weather in our solar
system. On stars, flares and their parameters are well determined,
in contrast to CMEs; their parameters are still not determined
statistically. Both phenomena may have severe effects on planetary
atmospheres and, in addition, stellar CMEs may play an important
role in stellar mass and angular momentum loss and therefore in
stellar evolution. Flares are directly detectable from photometric
observations, whereas the detection of CMEs requires different
observational methods. CMEs have different signatures in different
wavelength regimes. Most of the stellar CMEs were detected so far
using the method of Doppler-shifted Balmer flux which is accessible via
spectroscopic measurements. Several observational programs have been
carried out and are planned for the future, including new observations
and archival data. Also several attempts to detect stellar CMEs via
radio emission have been carried out in the past decades. Finally,
the X-ray regime may provide a valuable data pool to look for so-called
dimmings, well-known from the Sun, which are closely related to CMEs and
which are detectable in X-ray light curves. So far stellar CMEs have
been detected rarely and only a handful of distinct events is known,
mainly for dMe stars. We report on past, ongoing and future campaigns
of stellar CMEs on F-, G-, K-, and M-type pre- and main-sequence stars.
Title: Mapping the Magnetic Field of Flare Coronal Loops
Authors: Kuridze, D.; Mathioudakis, M.; Morgan, H.; Oliver, R.; Kleint,
L.; Zaqarashvili, T. V.; Reid, A.; Koza, J.; Löfdahl, M. G.; Hillberg,
T.; Kukhianidze, V.; Hanslmeier, A.
Bibcode: 2019ApJ...874..126K
Altcode: 2019arXiv190207514K
Here, we report on the unique observation of flaring coronal loops at
the solar limb using high-resolution imaging spectropolarimetry from
the Swedish 1 m Solar Telescope. The vantage position, orientation,
and nature of the chromospheric material that filled the flare loops
allowed us to determine their magnetic field with unprecedented accuracy
using the weak-field approximation method. Our analysis reveals coronal
magnetic field strengths as high as 350 G at heights up to 25 Mm above
the solar limb. These measurements are substantially higher than a
number of previous estimates and may have considerable implications
for our current understanding of the extended solar atmosphere.
Title: Coronal mass ejections on young G, K, and M stars
Authors: Odert, Petra; Leitzinger, Martin; Hanslmeier, Arnold;
Lammer, Helmut
Bibcode: 2019EGUGA..21.6870O
Altcode:
Young and magnetically active G, K, and M dwarfs exhibit high rates of
flares, including ones that are orders of magnitude more energetic than
known from the Sun, so-called superflares. On the Sun, strong flares
are almost always accompanied by coronal mass ejections (CMEs). This
raises the question if young active stars have correspondingly large
CME rates. This could be an important contribution to stellar mass-
and angular momentum loss. Moreover, frequent CME impacts could
then lead to efficient erosion of planetary atmospheres. However,
in contrast to flares, observations of stellar CMEs are rare and
often the observational methods do not allow for an unambiguous
identification. We present results from a model which combines stellar
flare rates with solar flare-CME relationships to estimate the possible
CME occurrence rates and the associated mass-loss from active G, K,
and M stars. Comparison with stellar mass-loss measurements shows that
for the most active stars, the mass-loss rates from CMEs tend to be
overestimated, which could be due to increased confinement by their
strong magnetic fields.
Title: Estimate of the Accretion Disk Size in the Gravitationally
Lensed Quasar HE 0435-1223 Using Microlensing Magnification Statistics
Authors: Fian, C.; Mediavilla, E.; Jiménez-Vicente, J.; Muñoz,
J. A.; Hanslmeier, A.
Bibcode: 2018ApJ...869..132F
Altcode: 2018arXiv181103312F
We present a measurement of the accretion disk size of the quadruple
lensed quasar HE 0435-1223 from well-sampled 13-year COSMOGRAIL
optical light curves. Using accurate time delays for the images A, B,
C, and D, we modeled and removed the intrinsic quasar variability,
and found microlensing events of amplitude up to 0.6, 0.4, and 0.5
mag in the images A, C, and D, respectively. From the statistics of
microlensing magnifications in these images we use Bayesian methods to
estimate the size of the quasar accretion disk. We have inferred the
half-light radius for the accretion disk using two different methods,
{R}1/2={7.6}-1.1+12.0\sqrt{M/0.3
{M}⊙ } lt-days (histogram product) and
{R}1/2={7.7}-1.2+7.0\sqrt{M/0.3
{M}⊙ } lt-days (χ 2 criterion). The results
are self-consistent and in good agreement with the continuum size
predicted by single-epoch spectroscopy and previous studies making
use of narrowband photometry of HE 0435-1223.
Title: Planetary Habitability and Stellar Activity
Authors: Hanslmeier, Arnold
Bibcode: 2018phsa.book.....H
Altcode:
No abstract at ADS
Title: Does the solar granulation change with the activity cycle?
Authors: Muller, R.; Hanslmeier, A.; Utz, D.; Ichimoto, K.
Bibcode: 2018A&A...616A..87M
Altcode:
Context. Knowledge of the variation of the solar granulation properties
(contrast and scale) with the 11-yr activity cycle is useful for a
better understanding of the interaction between magnetic field and
convection at global or local scales. A varying granulation may also
contribute to irradiance variations and affect the p-mode damping
rates and lifetimes.
Aims: HINODE/SOT blue continuum images
taken in the frame of the synoptic program at the disk center on a
daily basis between November 2006 and February 2016 are used. This
period covers the minimum of activity between cycles 23 and 24 and the
maximum of cycle 24.
Methods: The sharpness of a significant
number of images was reduced because of instrumental aberrations or
inaccurate focusing. Only the sharpest images were selected for this
investigation.
Results: To be detectable with HINODE/SOT images,
the variation of the granulation contrast and of the granulation scale
at the disk center should have been larger than 3%. As it is not the
case, it is concluded that they varied by less than 3% through the
weak cycle 24.
Title: Numerical Simulation of Coronal Waves Interacting with Coronal
Holes. III. Dependence on Initial Amplitude of the Incoming Wave
Authors: Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold;
Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović,
Jaša
Bibcode: 2018ApJ...860...24P
Altcode: 2018arXiv181112735P
We performed 2.5D magnetohydrodynamic (MHD) simulations showing the
propagation of fast-mode MHD waves of different initial amplitudes and
their interaction with a coronal hole (CH), using our newly developed
numerical code. We find that this interaction results in, first, the
formation of reflected, traversing, and transmitted waves (collectively,
secondary waves) and, second, in the appearance of stationary features
at the CH boundary. Moreover, we observe a density depletion that
is moving in the opposite direction of the incoming wave. We find a
correlation between the initial amplitude of the incoming wave and
the amplitudes of the secondary waves as well as the peak values of
the stationary features. Additionally, we compare the phase speed of
the secondary waves and the lifetime of the stationary features to
observations. Both effects obtained in the simulation, the evolution
of secondary waves, as well as the formation of stationary fronts at
the CH boundary, strongly support the theory that coronal waves are
fast-mode MHD waves.
Title: Microlensing and Intrinsic Variability of the Broad Emission
Lines of Lensed Quasars
Authors: Fian, C.; Guerras, Eduardo; Mediavilla, E.; Jiménez-Vicente,
J.; Muñoz, J. A.; Falco, E. E.; Motta, V.; Hanslmeier, A.
Bibcode: 2018ApJ...859...50F
Altcode: 2018arXiv180509619F
We study the broad emission lines in a sample of 11 gravitationally
lensed quasars with at least two epochs of observation to identify
intrinsic variability and to disentangle it from microlensing. To
improve our statistical significance and emphasize trends, we also
include 15 lens systems with single-epoch spectra. Mg II and C III]
emission lines are only weakly affected by microlensing, but C IV
shows strong microlensing in some cases, even for regions of the line
core, presumably associated with small projected velocities. However,
excluding the strongly microlensed cases, there is a strikingly good
match, on average, between the red wings of the C IV and C III]
profiles. Analysis of these results supports the existence of two
regions in the broad-line region (BLR), one that is insensitive
to microlensing (of size ≳50 lt-day and kinematics not confined
to a plane) and another that shows up only when it is magnified by
microlensing (of size of a few light-days, comparable to the accretion
disk). Both regions can contribute in different proportions to the
emission lines of different species and, within each line profile,
to different velocity bins, all of which complicates detailed studies
of the BLR based on microlensing size estimates. The strength of the
microlensing indicates that some spectral features that make up the
pseudo-continuum, such as the shelf-like feature at λ1610 or several
Fe III blends, may in part arise from an inner region of the accretion
disk. In the case of Fe II, microlensing is strong in some blends
but not in others. This opens up interesting possibilities to study
quasar accretion disk kinematics. Intrinsic variability seems to affect
the same features prone to microlensing, with similar frequency and
amplitude, but does not induce outstanding profile asymmetries. We
measure intrinsic variability (≲20%) of the wings with respect
to the cores in the C IV, C III], and Mg II lines consistent with
reverberation mapping studies.
Title: Meridional Motions and Reynolds Stress Determined by Using
Kanzelhöhe Drawings and White Light Solar Images from 1964 to 2016
Authors: Ruždjak, Domagoj; Sudar, Davor; Brajša, Roman; Skokić,
Ivica; Poljančić Beljan, Ivana; Jurdana-Šepić, Rajka; Hanslmeier,
Arnold; Veronig, Astrid; Pötzi, Werner
Bibcode: 2018SoPh..293...59R
Altcode: 2018arXiv180401344R
Sunspot position data obtained from Kanzelhöhe Observatory for
Solar and Environmental Research (KSO) sunspot drawings and white
light images in the period 1964 to 2016 were used to calculate the
rotational and meridional velocities of the solar plasma. Velocities
were calculated from daily shifts of sunspot groups and an iterative
process of calculation of the differential rotation profiles was used
to discard outliers. We found a differential rotation profile and
meridional motions in agreement with previous studies using sunspots as
tracers and conclude that the quality of the KSO data is appropriate
for analysis of solar velocity patterns. By analyzing the correlation
and covariance of meridional velocities and rotation rate residuals
we found that the angular momentum is transported towards the solar
equator. The magnitude and latitudinal dependence of the horizontal
component of the Reynolds stress tensor calculated is sufficient to
maintain the observed solar differential rotation profile. Therefore,
our results confirm that the Reynolds stress is the dominant mechanism
responsible for transport of angular momentum towards the solar equator.
Title: Numerical Simulation of Coronal Waves Interacting with Coronal
Holes. II. Dependence on Alfvén Speed Inside the Coronal Hole
Authors: Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold;
Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović,
Jaša
Bibcode: 2018ApJ...857..130P
Altcode: 2018arXiv181112726P
We used our newly developed magnetohydrodynamic (MHD) code to perform
2.5D simulations of a fast-mode MHD wave interacting with coronal holes
(CHs) of varying Alfvén speed that result from assuming different
CH densities. We find that this interaction leads to effects like
reflection, transmission, stationary fronts at the CH boundary,
and the formation of a density depletion that moves in the opposite
direction to the incoming wave. We compare these effects with regard
to the different CH densities and present a comprehensive analysis of
morphology and kinematics of the associated secondary waves. We find
that the density value inside the CH influences the phase speed and
the amplitude values of density and magnetic field for all different
secondary waves. Moreover, we observe a correlation between the
CH density and the peak values of the stationary fronts at the CH
boundary. The findings of reflection and transmission on the one hand
and the formation of stationary fronts caused by the interaction of
MHD waves with CHs on the other hand strongly support the theory that
large-scale disturbances in the corona are fast-mode MHD waves.
Title: PyTranSpot: A tool for multiband light curve modeling of
planetary transits and stellar spots
Authors: Juvan, Ines G.; Lendl, M.; Cubillos, P. E.; Fossati, L.;
Tregloan-Reed, J.; Lammer, H.; Guenther, E. W.; Hanslmeier, A.
Bibcode: 2018A&A...610A..15J
Altcode: 2017arXiv171011209J
Several studies have shown that stellar activity features, such as
occulted and non-occulted starspots, can affect the measurement of
transit parameters biasing studies of transit timing variations and
transmission spectra. We present PyTranSpot, which we designed to
model multiband transit light curves showing starspot anomalies,
inferring both transit and spot parameters. The code follows a
pixellation approach to model the star with its corresponding limb
darkening, spots, and transiting planet on a two dimensional Cartesian
coordinate grid. We combine PyTranSpot with a Markov chain Monte
Carlo framework to study and derive exoplanet transmission spectra,
which provides statistically robust values for the physical properties
and uncertainties of a transiting star-planet system. We validate
PyTranSpot's performance by analyzing eleven synthetic light curves
of four different star-planet systems and 20 transit light curves
of the well-studied WASP-41b system. We also investigate the impact
of starspots on transit parameters and derive wavelength dependent
transit depth values for WASP-41b covering a range of 6200-9200 Å,
indicating a flat transmission spectrum.
Title: Numerical Simulations of Kelvin-Helmholtz Instabilities in
a two-fluid regime
Authors: Piantschitsch, I.; Hanslmeier, A.; Roth, M.; Zaqarashvili,
T. V.
Bibcode: 2018CEAB...42...10P
Altcode:
The role of photospheric and chromospheric jets in heating the upper
solar atmosphere is not yet fully understood. Recent observational and
theoretical results have shown that Kelvin-Helmholtz Instabilities
(KHIs) occur in certain EUV jets with specific plasma density and
magnetic field parameters. KHIs have the potential to heat the
surrounding plasma and therefore may contribute to chromospheric
and coronal heating. Up to now, KHIs in the solar atmosphere have
been simulated mostly by using magnetohydrodynamic (MHD) models. We
show that simulations which are based on a two-fluid approach,
including collisional effects between neutral and ionized particles,
can lead to higher temperatures in the vortice-like structures along
the boundary layers of jets. Hence, the classical MHD approach may
have underestimated the role of KHIs in chromospheric and coronal
heating. Therefore, we suggest to include a two-fluid approach in
future simulations of KHIs in the upper layers of the solar atmosphere.
Title: Stellar coronal mass ejections - I. Estimating occurrence
frequencies and mass-loss rates
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.
Bibcode: 2017MNRAS.472..876O
Altcode: 2017arXiv170702165O
Stellar coronal mass ejections (CMEs) may play an important role in
mass- and angular momentum loss of young Sun-like stars. If occurring
frequently, they may also have a strong effect on planetary evolution
by increasing atmospheric erosion. So far it has not been possible to
infer the occurrence frequency of stellar CMEs from observations. Based
on their close relation with flares on the Sun, we develop an empirical
model combining solar flare-CME relationships with stellar flare
rates to estimate the CME activity of young Sun-like and late-type
main-sequence stars. By comparison of the obtained CME mass-loss rates
with observations of total mass-loss rates, we find that our modelled
rates may exceed those from observations by orders of magnitude for the
most active stars. This reveals a possible limit to the extrapolation
of such models to the youngest stars. We find that the most uncertain
component in the model is the flare-CME association rate adopted from
the Sun, which does not properly account for the likely stronger coronal
confinement in active stars. Simple estimates of this effect reveal a
possible suppression of CME rates by several orders of magnitude for
young stars, indicating that this issue should be addressed in more
detail in the future.
Title: A Numerical Simulation of Coronal Waves Interacting with
Coronal Holes. I. Basic Features
Authors: Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold;
Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović,
Jaša; Žic, Tomislav
Bibcode: 2017ApJ...850...88P
Altcode: 2018arXiv181112073P
We have developed a new numerical code that is able to perform 2.5D
simulations of a magnetohydrodynamic (MHD) wave propagation in the
corona, and its interaction with a low-density region, such as a
coronal hole (CH). We show that the impact of the wave on the CH
leads to different effects, such as reflection and transmission of the
incoming wave, stationary features at the CH boundary, or formation
of a density depletion. We present a comprehensive analysis of the
morphology and kinematics of primary and secondary waves, I.e.,
we describe in detail the temporal evolution of density, magnetic
field, plasma flow velocity, phase speed, and position of the wave
amplitude. Effects like reflection, refraction, and transmission of
the wave strongly support the theory that large-scale disturbances
in the corona are fast MHD waves and distinguish that theory from the
competing pseudo-wave theory. The formation of stationary bright fronts
was one of the main reasons for the development of pseudo-waves. Here,
we show that stationary bright fronts can be produced by interactions
of an MHD wave with a CH. We find secondary waves that are traversing
through the CH and we show that one part of these traversing waves
leaves the CH again, while another part is being reflected at the CH
boundary inside the CH. We observe a density depletion that is moving
in the opposite direction of the primary wave propagation. We show
that the primary wave pushes the CH boundary to the right, caused by
the wave front exerting dynamic pressure on the CH.
Title: Solar differential rotation in the period 1964-2016 determined
by the Kanzelhöhe data set
Authors: Poljančić Beljan, I.; Jurdana-Šepić, R.; Brajša, R.;
Sudar, D.; Ruždjak, D.; Hržina, D.; Pötzi, W.; Hanslmeier, A.;
Veronig, A.; Skokić, I.; Wöhl, H.
Bibcode: 2017A&A...606A..72P
Altcode:
Context. Kanzelhöhe Observatory for Solar and Environmental Research
(KSO) provides daily multispectral synoptic observations of the Sun
using several telescopes. In this work we made use of sunspot drawings
and full disk white light CCD images.
Aims: The main aim of
this work is to determine the solar differential rotation by tracing
sunspot groups during the period 1964-2016, using the KSO sunspot
drawings and white light images. We also compare the differential
rotation parameters derived in this paper from the KSO with those
collected fromf other data sets and present an investigation of the
north - south rotational asymmetry.
Methods: Two procedures
for the determination of the heliographic positions were applied: an
interactive procedure on the KSO sunspot drawings (1964-2008, solar
cycles Nos. 20-23) and an automatic procedure on the KSO white light
images (2009-2016, solar cycle No. 24). For the determination of the
synodic angular rotation velocities two different methods have been
used: a daily shift (DS) method and a robust linear least-squares fit
(rLSQ) method. Afterwards, the rotation velocities had to be converted
from synodic to sidereal, which were then used in the least-squares
fitting for the solar differential rotation law. A comparison of
the interactive and automatic procedures was performed for the
year 2014.
Results: The interactive procedure of position
determination is fairly accurate but time consuming. In the case
of the much faster automatic procedure for position determination,
we found the rLSQ method for calculating rotational velocities to
be more reliable than the DS method. For the test data from 2014,
the rLSQ method gives a relative standard error for the differential
rotation parameter B that is three times smaller than the corresponding
relative standard error derived for the DS method. The best fit solar
differential rotation profile for the whole time period is ω(b) =
(14.47 ± 0.01)-(2.66 ± 0.10)sin2b (deg/day) for the DS
method and ω(b) = (14.50 ± 0.01)-(2.87 ± 0.12)sin2b
(deg/day) for the rLSQ method. A barely noticeable north - south
asymmetry is observed for the whole time period 1964-2016 in the
present paper. Rotation profiles, using different data sets, presented
by other authors for the same time periods and the same tracer types,
are in good agreement with our results.
Conclusions: The KSO
data set used in this paper is in good agreement with the Debrecen
Photoheliographic Data and Greenwich Photoheliographic Results and is
suitable for the investigation of the long-term variabilities in the
solar rotation profile. Also, the quality of the KSO sunspot drawings
has gradually increased during the last 50 yr.
Title: Structure of the solar photosphere studied from the radiation
hydrodynamics code ANTARES
Authors: Leitner, P.; Lemmerer, B.; Hanslmeier, A.; Zaqarashvili,
T.; Veronig, A.; Grimm-Strele, H.; Muthsam, H. J.
Bibcode: 2017Ap&SS.362..181L
Altcode: 2017arXiv170801156L
The ANTARES radiation hydrodynamics code is capable of simulating
the solar granulation in detail unequaled by direct observation. We
introduce a state-of-the-art numerical tool to the solar physics
community and demonstrate its applicability to model the solar
granulation. The code is based on the weighted essentially
non-oscillatory finite volume method and by its implementation
of local mesh refinement is also capable of simulating turbulent
fluids. While the ANTARES code already provides promising insights
into small-scale dynamical processes occurring in the quiet-Sun
photosphere, it will soon be capable of modeling the latter in the
scope of radiation magnetohydrodynamics. In this first preliminary
study we focus on the vertical photospheric stratification by examining
a 3-D model photosphere with an evolution time much larger than the
dynamical timescales of the solar granulation and of particular large
horizontal extent corresponding to 25''×25'' on the solar surface to
smooth out horizontal spatial inhomogeneities separately for up- and
downflows. The highly resolved Cartesian grid thereby covers ∼4 Mm
of the upper convection zone and the adjacent photosphere. Correlation
analysis, both local and two-point, provides a suitable means to probe
the photospheric structure and thereby to identify several layers
of characteristic dynamics: The thermal convection zone is found to
reach some ten kilometers above the solar surface, while convectively
overshooting gas penetrates even higher into the low photosphere. An
≈145 km wide transition layer separates the convective from the
oscillatory layers in the higher photosphere.
Title: Spectroscopic Inversions of the Ca II 8542 Å Line in a
C-class Solar Flare
Authors: Kuridze, D.; Henriques, V.; Mathioudakis, M.; Koza, J.;
Zaqarashvili, T. V.; Rybák, J.; Hanslmeier, A.; Keenan, F. P.
Bibcode: 2017ApJ...846....9K
Altcode: 2017arXiv170800472K
We study the C8.4-class solar flare SOL2016-05-14T11:34 UT using
high-resolution spectral imaging in the Ca II 8542 Å line obtained
with the CRISP imaging spectropolarimeter on the Swedish 1 m Solar
Telescope. Spectroscopic inversions of the Ca II 8542 Å line using
the non-LTE code NICOLE are used to investigate the evolution of
the temperature and velocity structure in the flaring chromosphere. A
comparison of the temperature stratification in flaring and non-flaring
areas reveals strong footpoint heating during the flare peak in the
lower atmosphere. The temperature of the flaring footpoints between
{log} {τ }500 ≈ -2.5 {and} -3.5, where τ 500
is the continuum optical depth at 500 nm, is ∼ 5{--}6.5 {kK} close
to the flare peak, reducing gradually to ∼ 5 {kK}. The temperature in
the middle and upper chromosphere, between {log} {τ }500≈
-3.5 and -5.5, is estimated to be ∼6.5-20 kK, decreasing to preflare
temperatures, ∼5-10 kK, after approximately 15 minutes. However, the
temperature stratification of the non-flaring areas is unchanged. The
inverted velocity fields show that the flaring chromosphere is dominated
by weak downflowing condensations at the formation height of Ca II
8542 Å.
Title: Solar differential rotation in the period 1964 - 2016
determined by the Kanzelhöhe data set
Authors: Poljančić Beljan, I.; Jurdana-Šepić, R.; Brajša, R.;
Sudar, D.; Ruždjak, D.; Hržina, D.; Pötzi, W.; Hanslmeier, A.;
Veronig, A.; Skokić, I.; Wöhl, H.
Bibcode: 2017arXiv170707886P
Altcode:
The main aim of this work is to determine the solar differential
rotation by tracing sunspot groups during the period 1964-2016, using
the Kanzelhöhe Observatory for Solar and Environmental Research
(KSO) sunspot drawings and white light images. Two procedures for
the determination of the heliographic positions were applied: an
interactive procedure on the KSO sunspot drawings (1964 - 2008, solar
cycles nos. 20 - 23) and an automatic procedure on the KSO white light
images (2009 - 2016, solar cycle no. 24). For the determination of the
synodic angular rotation velocities two different methods have been
used: a daily shift (DS) method and a robust linear least-squares fit
(rLSQ) method. Afterwards, the rotation velocities had to be converted
from synodic to sidereal, which were then used in the least-squares
fitting for the solar differential rotation law. For the test
data from 2014, we found the rLSQ method for calculating rotational
velocities to be more reliable than the DS method. The best fit solar
differential rotation profile for the whole time period is $\omega(b)$
= (14.47 $\pm$ 0.01) - (2.66 $\pm$ 0.10) $\sin^2b$ (deg/day) for the
DS method and $\omega(b)$ = (14.50 $\pm$ 0.01) - (2.87 $\pm$ 0.12)
$\sin^2b$ (deg/day) for the rLSQ method. A barely noticeable north -
south asymmetry is observed for the whole time period 1964 - 2016
in the present paper. Rotation profiles, using different data sets
(e.g. Debrecen Photoheliographic Data, Greenwich Photoheliographic
Results), presented by other authors for the same time periods and the
same tracer types, are in good agreement with our results. Therefore,
the KSO data set is suitable for the investigation of the long-term
variabilities in the solar rotation profile.
Title: Flare-induced changes of the photospheric magnetic field in
a δ-spot deduced from ground-based observations
Authors: Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.;
Veronig, A. M.; González Manrique, S. J.; Kučera, A.; Schwartz,
P.; Hanslmeier, A.
Bibcode: 2017A&A...602A..60G
Altcode: 2017arXiv170406089G
Aims: Changes of the magnetic field and the line-of-sight
velocities in the photosphere are being reported for an M-class
flare that originated at a δ-spot belonging to active region NOAA
11865.
Methods: High-resolution ground-based near-infrared
spectropolarimetric observations were acquired simultaneously in
two photospheric spectral lines, Fe I 10783 Å and Si I 10786 Å,
with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope
(VTT) in Tenerife on 2013 October 15. The observations covered several
stages of the M-class flare. Inversions of the full-Stokes vector of
both lines were carried out and the results were put into context using
(extreme)-ultraviolet filtergrams from the Solar Dynamics Observatory
(SDO).
Results: The active region showed high flaring activity
during the whole observing period. After the M-class flare, the
longitudinal magnetic field did not show significant changes along
the polarity inversion line (PIL). However, an enhancement of the
transverse magnetic field of approximately 550 G was found that
bridges the PIL and connects umbrae of opposite polarities in the
δ-spot. At the same time, a newly formed system of loops appeared
co-spatially in the corona as seen in 171 Å filtergrams of the
Atmospheric Imaging Assembly (AIA) on board SDO. However, we cannot
exclude that the magnetic connection between the umbrae already existed
in the upper atmosphere before the M-class flare and became visible
only later when it was filled with hot plasma. The photospheric
Doppler velocities show a persistent upflow pattern along the PIL
without significant changes due to the flare.
Conclusions:
The increase of the transverse component of the magnetic field after
the flare together with the newly formed loop system in the corona
support recent predictions of flare models and flare observations. The movie associated to Figs. 4 and 5 is available at http://www.aanda.org
Title: Oscillation of solar radio emission at coronal acoustic
cut-off frequency
Authors: Pylaev, O. S.; Zaqarashvili, T. V.; Brazhenko, A. I.; Melnik,
V. N.; Hanslmeier, A.; Panchenko, M.
Bibcode: 2017A&A...601A..42P
Altcode: 2017arXiv170309929P
Recent SECCHI COR2 observations on board STEREO-A spacecraft have
detected density structures at a distance of 2.5-15 R0
propagating with periodicity of about 90 min. The observations show that
the density structures probably formed in the lower corona. We used
the large Ukrainian radio telescope URAN-2 to observe type IV radio
bursts in the frequency range of 8-32 MHz during the time interval
of 08:15-11:00 UT on August 1, 2011. Radio emission in this frequency
range originated at the distance of 1.5-2.5 R0 according to
the Baumbach-Allen density model of the solar corona. Morlet wavelet
analysis showed the periodicity of 80 min in radio emission intensity
at all frequencies, which demonstrates that there are quasi-periodic
variations of coronal density at all heights. The observed periodicity
corresponds to the acoustic cut-off frequency of stratified corona
at a temperature of 1 MK. We suggest that continuous perturbations of
the coronal base in the form of jets/explosive events generate acoustic
pulses, which propagate upwards and leave the wake behind oscillating at
the coronal cut-off frequency. This wake may transform into recurrent
shocks due to the density decrease with height, which leads to the
observed periodicity in the radio emission. The recurrent shocks may
trigger quasi-periodic magnetic reconnection in helmet streamers,
where the opposite field lines merge and consequently may generate
periodic density structures observed in the solar wind.
Title: Latitude dependence of the solar granulation during the
minimum of activity in 2009
Authors: Muller, R.; Hanslmeier, A.; Utz, D.
Bibcode: 2017A&A...598A...6M
Altcode:
Context. Knowledge of the latitude variation of the solar granulation
properties (contrast and scale) is useful to better understand
interactions between magnetic field, convection, differential rotation,
and meridional circulation in the solar atmosphere.
Aims: We
investigated the latitude dependence of the contrast and scale of the
solar granulation, with the help of HINODE/SOT blue continuum images
taken in the frame of the HOP 79 program, along the central meridian
and along the equator on a monthly basis in 2009 during the last solar
minimum of activity.
Methods: We selected the sharpest images
in latitude and longitude intervals. The selected images in all the N-S
and E-W scans taken in 2009 were combined to get statistically reliable
results.
Results: The contrast of the solar granulation decreases
towards the poles and the scale increases, but not regularly since a
perturbation occurs at around 60° where both quantities return close
to their values at the disk center.
Conclusions: Such a latitude
variation in a period of minimum of activity (2009), is probably not
due to magnetic field, neither the quiet magnetic field at the surface,
nor the strong magnetic flux tubes associated with active regions,
which could be embedded more or less deeply in the convection zone
before they reach the surface. The decrease in contrast and increase in
scale towards the pole seem to be related to the differential rotation
and the perturbation around 60° to the meridional circulation.
Title: Dynamics of small-scale convective motions
Authors: Lemmerer, B.; Hanslmeier, A.; Muthsam, H.; Piantschitsch, I.
Bibcode: 2017A&A...598A.126L
Altcode: 2016arXiv161106786L
Context. Previous studies have discovered a population of small granules
with diameters less than 800 km located in the intergranular lanes
showing differing physical properties. High resolution simulations
and observations of the solar granulation, in combination with
automated segmentation and temporal tracking algorithms, allow us
to study the evolution of the structural and physical properties of
these granules and surrounding vortex motions with high temporal and
spatial accuracy.
Aims: We focus on the dynamics of granules,
that is, the lifetime of granular cells, the fragmentation behavior, the
variation of size, position, emergent intensity and vertical velocity
over time and the influence of strong vortex motions. Of special
interest are the dynamics of small granules compared to regular-sized
granules.
Methods: We developed a temporal tracking algorithm
based on our previously developed segmentation algorithm for solar
granulation. This was applied to radiation hydrodynamics simulations
and high resolution observations of the quiet Sun by SUNRISE/IMaX.
Results: The dynamics of small granules differ in regard to their
diameter, intensity and depth evolution compared to the population
of regular granules. The tracked granules in the simulation and
observations reveal similar dynamics regarding their lifetime, evolution
of size, vertical velocity and intensity. The fragmentation analysis
shows that the majority of granules in the simulations do not fragment,
while the opposite was found in the observations. Strong horizontal
and vertical vortex motions were detected at the location of small
granules. Compared to granules, regions of strong vertical vorticity
show higher intensities and higher downflow velocities, and live up
to several minutes.
Conclusions: The analysis of granules
separated according to their diameter in different groups reveals
strongly differing behaviors. The largest discrepancies can be found
within the groups of small, medium-sized and large granules. Therefore,
these groups have to be analyzed independently. The predominant location
of vortex motions on and close to small granules indicates a strong
influence on the dynamics of granules.
Title: Supernovae, Our Solar System, and Life on Earth
Authors: Hanslmeier, Arnold
Bibcode: 2017hsn..book.2489H
Altcode:
Supernovae in the solar neighborhood can have influence on the
dynamics of small solar system bodies as well as on the atmospheres
of planets. During a supernova outburst enhanced particle emissions
as well as enhanced short wavelength radiation occur. We give an
overview of the interaction of nearby supernovae to the outer parts
of the solar system, the Oort cloud, and then on the heliosphere
which deflects charged particles and provides a shielding. Finally,
the influence of supernova radiation and short wavelength radiation
on the Earth's atmosphere is discussed. Enhanced cosmic ray particles
from supernovae may also act as condensation nuclei and therefore
trigger cloud formation in the Earth's atmosphere.
Title: Das helle und das dunkle Universum
Authors: Hanslmeier, Arnold
Bibcode: 2017hdu..book.....H
Altcode:
No abstract at ADS
Title: Probing the lower solar atmosphere with CRSIP-SST Data
Authors: Hanslmeier, Arnold; Zaqarashvili, Teimuraz; Koza, Julius;
Rybak, Jan
Bibcode: 2017psio.confE.113H
Altcode:
No abstract at ADS
Title: High-resolution modeling of the solar photosphere with the
ANTARES RHD code
Authors: Leitner, P.; Lemmerer, B.; Hanslmeier, A.; Zaqarashvili,
T.; Veronig, A.; Muthsam, H.
Bibcode: 2017psio.confE.110L
Altcode:
No abstract at ADS
Title: Flare induced changes of the photospheric magnetic field in
a delta-spot deduced from ground-based observations
Authors: Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.;
Kuĉera, A.; González Manrique, S. J.; Schwartz, P.; Veronig, A. M.;
Hanslmeier, A.
Bibcode: 2017psio.confE.107G
Altcode:
No abstract at ADS
Title: Science with a 1 Meter Telescope
Authors: Hanslmeier, A.
Bibcode: 2017CEAB...41...13H
Altcode:
We will give a short overview on the possibilities and limitations of
modern 1-meter class telescopes and also mention some examples.
Title: Extreme Space Weather in Extra-Solar Systems - a Flare
Alert Program
Authors: Hanslmeier, A.; Leitzinger, M.; Greimel, R.; Odert, P.;
Ratzka, T.; Brajša, R.; Guenther, E. W.; Korhonen, H.; Pribulla, T.;
Šlechta, M.; Vida, K.; Güdel, M.; Heinzel, P.; Lammer, H.; Ribas, I.
Bibcode: 2017CEAB...41...67H
Altcode:
Highly energetic stellar activity phenomena, such as outbreaks of
radiations (flares) and mass expulsions into the helio-/astro-sphere
(coronal mass ejections/CMEs), may have a severe impact on
the atmospheric evolution of planets. Stellar flare have been
studied for decades now and their typical parameters are determined
statistically. However, observations of stellar CMEs are rare, yielding
only a handful of detections so far. The detection of CMEs on stars
demands more observational effort than the detection flares, because
the circumstellar environment cannot be spatially resolved like in the
Solar System. The most convincing detections up to now were found as
Doppler-shifted Balmer line extra-emission/absorption features emerging
close to flare events, indicating the rise end ejection of prominence
material embedded in the CME core. Dedicated programs aiming for a
statistical determination of occurrence rates and the parameters of
stellar CMEs are still lacking. Therefore, we propose an innovative
and efficient observational approach to search for and characterize
CMEs on Sun-like and late-type pre-main sequence and main sequence
stars to determine stellar CME parameters and their occurrence rates
as a function of stellar spectral type and age, as well as establish
a stellar flare/CME association rate, for the first time ever.
Title: Indications of stellar prominence oscillations on fast rotating
stars: the cases of HK Aqr and PZ Tel
Authors: Leitzinger, M.; Odert, P.; Zaqarashvili, T. V.; Greimel,
R.; Hanslmeier, A.; Lammer, H.
Bibcode: 2016MNRAS.463..965L
Altcode: 2016MNRAS.tmp.1048L; 2016arXiv160800453L
We present the analysis of six nights of spectroscopic monitoring of
two young and fast rotating late-type stars, namely the dMe star HK
Aqr and the dG/dK star PZ Tel. On both stars, we detect absorption
features reminiscent of signatures of corotating cool clouds or
prominences visible in Hα. Several prominences on HK Aqr show periodic
variability in the prominence tracks which follow a sinusoidal motion
(indication of prominence oscillations). On PZ Tel, we could not
find any periodic variability in the prominence tracks. By fitting
sinusoidal functions to the prominence tracks, we derive amplitudes
and periods which are similar to those of large-amplitude oscillations
seen in solar prominences. In one specific event, we also derive a
periodic variation of the prominence track in the Hβ spectral line
which shows an anti-phase variation with the one derived for the Hα
spectral line. Using these parameters and estimated mass density of a
prominence on HK Aqr, we derive a minimum magnetic field strength of
∼2 G. The relatively low strength of the magnetic field is explained
by the large height of this stellar prominence (≥ 0.67 stellar radii
above the surface).
Title: Size of the Accretion Disk in the Graviationally Lensed Quasar
SDSS J1004+4112 from the Statistics of Microlensing Magnifications
Authors: Fian, C.; Mediavilla, E.; Hanslmeier, A.; Oscoz, A.;
Serra-Ricart, M.; Muñoz, J. A.; Jiménez-Vicente, J.
Bibcode: 2016ApJ...830..149F
Altcode: 2016arXiv160803831F
We present eight monitoring seasons of the four brightest images of
the gravitational lens SDSS J1004+4112 observed between 2003 December
and 2010 October. Using measured time delays for the images A, B,
and C and the model predicted time delay for image D we have removed
the intrinsic quasar variability, finding microlensing events of
about 0.5 and 0.7 mag of amplitude in the images C and D. From the
statistics of microlensing amplitudes in images A, C, and D, we
have inferred the half-light radius (at {λ }{rest}=2407
\mathringA ) for the accretion disk using two different methods,
{R}1/2={8.7}-5.5+18.5\sqrt{M/0.3{M}⊙
} (histogram product) and
{R}1/2={4.2}-2.2+3.2\sqrt{M/0.3{M}⊙
} lt-days ({χ }2). The results are in agreement
within uncertainties with the size predicted from the black hole mass
in SDSS J1004+4112 using thin disk theory.
Title: Kelvin-Helmholtz Instability in Solar Chromospheric Jets:
Theory and Observation
Authors: Kuridze, D.; Zaqarashvili, T. V.; Henriques, V.; Mathioudakis,
M.; Keenan, F. P.; Hanslmeier, A.
Bibcode: 2016ApJ...830..133K
Altcode: 2016arXiv160801497K
Using data obtained by the high-resolution CRisp Imaging
SpectroPolarimeter instrument on the Swedish 1 m Solar Telescope,
we investigate the dynamics and stability of quiet-Sun chromospheric
jets observed at the disk center. Small-scale features, such as rapid
redshifted and blueshifted excursions, appearing as high-speed jets
in the wings of the Hα line, are characterized by short lifetimes and
rapid fading without any descending behavior. To study the theoretical
aspects of their stability without considering their formation
mechanism, we model chromospheric jets as twisted magnetic flux tubes
moving along their axis, and use the ideal linear incompressible
magnetohydrodynamic approximation to derive the governing dispersion
equation. Analytical solutions of the dispersion equation indicate
that this type of jet is unstable to Kelvin-Helmholtz instability
(KHI), with a very short (few seconds) instability growth time at
high upflow speeds. The generated vortices and unresolved turbulent
flows associated with the KHI could be observed as a broadening of
chromospheric spectral lines. Analysis of the Hα line profiles shows
that the detected structures have enhanced line widths with respect to
the background. We also investigate the stability of a larger-scale Hα
jet that was ejected along the line of sight. Vortex-like features,
rapidly developing around the jet’s boundary, are considered as
evidence of the KHI. The analysis of the energy equation in the
partially ionized plasma shows that ion-neutral collisions may lead
to fast heating of the KH vortices over timescales comparable to the
lifetime of chromospheric jets.
Title: Rieger-type Periodicity during Solar Cycles 14-24: Estimation
of Dynamo Magnetic Field Strength in the Solar Interior
Authors: Gurgenashvili, Eka; Zaqarashvili, Teimuraz V.; Kukhianidze,
Vasil; Oliver, Ramon; Ballester, Jose Luis; Ramishvili, Giorgi;
Shergelashvili, Bidzina; Hanslmeier, Arnold; Poedts, Stefaan
Bibcode: 2016ApJ...826...55G
Altcode: 2016arXiv160504162G
Solar activity undergoes a variation over timescales of several months
known as Rieger-type periodicity, which usually occurs near maxima
of sunspot cycles. An early analysis showed that the periodicity
appears only in some cycles and is absent in other cycles. But the
appearance/absence during different cycles has not been explained. We
performed a wavelet analysis of sunspot data from the Greenwich Royal
Observatory and the Royal Observatory of Belgium during cycles 14-24. We
found that the Rieger-type periods occur in all cycles, but they are
cycle dependent: shorter periods occur during stronger cycles. Our
analysis revealed a periodicity of 185-195 days during the weak cycles
14-15 and 24 and a periodicity of 155-165 days during the stronger
cycles 16-23. We derived the dispersion relation of the spherical
harmonics of the magnetic Rossby waves in the presence of differential
rotation and a toroidal magnetic field in the dynamo layer near the
base of the convection zone. This showed that the harmonics of fast
Rossby waves with m = 1 and n = 4, where m (n) indicates the toroidal
(poloidal) wavenumbers, perfectly fit with the observed periodicity. The
variation of the toroidal field strength from weaker to stronger cycles
may lead to the different periods found in those cycles, which explains
the observed enigmatic feature of the Rieger-type periodicity. Finally,
we used the observed periodicity to estimate the dynamo field strength
during cycles 14-24. Our estimations suggest a field strength of ∼40
kG for the stronger cycles and ∼20 kG for the weaker cycles.
Title: Rotating plasma jets in the photospheric intergranular lanes
Authors: Lemmerer, Birgit; Hanslmeier, Arnold; Muthsam, Herbert;
Piantschitsch, Isabell; Zaqarashvili, Teimuraz
Bibcode: 2016cosp...41E1136L
Altcode:
High resolution simulations and observations of the solar photosphere
reveal the population of small granular cells with diameters less than
600 km. However, the underlying mechanisms of their generation are
still unclear. Simulations show that the majority of small granules
may not result from fragmentation of larger granular cells but instead
evolve and dissolve in the intergranular lanes. We study the dynamics
of these granular cells in high resolution simulations. We found that
the small granules show a jet-like behavior with strong horizontal
and vertical vortex motions. A newly developed algorithm that tracks
the evolution of the 3D plasma cells in the convection zone and lower
photosphere shows strong vertical vorticity within the small granular
cells. The rotating plasma jets, which are visible as small granules,
may generate magnetized vortex flows and torsional Alfvén waves
observed at upper layers and hence can play a distinct role in the
energy supply to the chromosphere and corona.
Title: Long-term trends of magnetic bright points. I. Number of
magnetic bright points at disc centre
Authors: Utz, D.; Muller, R.; Thonhofer, S.; Veronig, A.; Hanslmeier,
A.; Bodnárová, M.; Bárta, M.; del Toro Iniesta, J. C.
Bibcode: 2016A&A...585A..39U
Altcode: 2015arXiv151107767U
Context. The Sun shows an activity cycle that is caused by its varying
global magnetic field. During a solar cycle, sunspots, I.e. extended
regions of strong magnetic fields, occur in activity belts that are
slowly migrating from middle to lower latitudes, finally arriving
close to the equator during the cycle maximum phase. While this
and other facts about the strong extended magnetic fields have been
well known for centuries, much less is known about the solar cycle
evolution of small-scale magnetic fields. Thus the question arises
if similar principles exist for small-scale magnetic fields.
Aims: To address this question, we study magnetic bright points (MBPs)
as proxies for such small-scale, kG solar magnetic fields. This study is
based on a homogeneous data set that covers a period of eight years. The
number of detected MBPs versus time is analysed to find out if there
is an activity cycle for these magnetic features too and, if so, how
it is related to the sunspot cycle.
Methods: An automated MBP
identification algorithm was applied to the synoptic Hinode/SOT G-band
data over the period November 2006 to August 2014, I.e. covering the
decreasing phase of Cycle 23 and the rise, maximum, and early decrease
of Cycle 24. This data set includes, at the moment of investigation, a
total of 4162 images, with about 2.9 million single MBP detections.
Results: After a careful preselection and monthly median filtering
of the data, the investigation revealed that the number of MBPs close
to the equator is coupled to the global solar cycle but shifted in time
by about 2.5 yr. Furthermore, the instantaneous number of detected MBPs
depends on the hemisphere, with one hemisphere being more prominent,
I.e. showing a higher number of MBPs. After the end of Cycle 23 and at
the starting point of Cycle 24, the more active hemisphere changed from
south to north. Clear peaks in the detected number of MBPs are found
at latitudes of about ±7°, in congruence with the positions of the
sunspot belts at the end of the solar cycle.
Conclusions: These
findings suggest that there is indeed a coupling between the activity of
MBPs close to the equator with the global magnetic field. The results
also indicate that a significant fraction of the magnetic flux that
is visible as MBPs close to the equator originates from the sunspot
activity belts. However, even during the minimum of MBP activity,
a percentage as large as 60% of the maximum number of detected MBPs
has been observed, which may be related to solar surface dynamo action.
Title: Faszination Astronomie: Ein topaktueller Einstieg für alle
naturwissenschaftlich Interessierten
Authors: Hanslmeier, Arnold
Bibcode: 2016faas.book.....H
Altcode:
No abstract at ADS
Title: SSALMON - The Solar Simulations for the Atacama Large
Millimeter Observatory Network
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Barta, M.; Hudson,
H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; De Pontieu,
B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J. H.;
Antolin, P.; Gunár, S.; Labrosse, N.; Benz, A. O.; Nindos, A.;
Steffen, M.; Scullion, E.; Doyle, J. G.; Zaqarashvili, T.; Hanslmeier,
A.; Nakariakov, V. M.; Heinzel, P.; Ayres, T.; Karlicky, M.
Bibcode: 2015AdSpR..56.2679W
Altcode: 2015arXiv150205601W
The Solar Simulations for the Atacama Large Millimeter Observatory
Network (SSALMON) was initiated in 2014 in connection with two ALMA
development studies. The Atacama Large Millimeter/submillimeter Array
(ALMA) is a powerful new tool, which can also observe the Sun at
high spatial, temporal, and spectral resolution. The international
SSALMONetwork aims at co-ordinating the further development of solar
observing modes for ALMA and at promoting scientific opportunities
for solar physics with particular focus on numerical simulations,
which can provide important constraints for the observing modes and
can aid the interpretation of future observations. The radiation
detected by ALMA originates mostly in the solar chromosphere - a
complex and dynamic layer between the photosphere and corona, which
plays an important role in the transport of energy and matter and the
heating of the outer layers of the solar atmosphere. Potential targets
include active regions, prominences, quiet Sun regions, flares. Here,
we give a brief overview over the network and potential science cases
for future solar observations with ALMA.
Title: Parallelization of the SIR code for the investigation of
small-scale features in the solar photosphere
Authors: Thonhofer, Stefan; Bellot Rubio, Luis R.; Utz, Dominik;
Hanslmeier, Arnold; Jurçák, Jan
Bibcode: 2015IAUS..305..251T
Altcode: 2015arXiv150303710T
Magnetic fields are one of the most important drivers of the highly
dynamic processes that occur in the lower solar atmosphere. They span a
broad range of sizes, from large- and intermediate-scale structures such
as sunspots, pores and magnetic knots, down to the smallest magnetic
elements observable with current telescopes. On small scales, magnetic
flux tubes are often visible as Magnetic Bright Points (MBPs). Apart
from simple V/I magnetograms, the most common method to deduce their
magnetic properties is the inversion of spectropolarimetric data. Here
we employ the SIR code for that purpose. SIR is a well-established
tool that can derive not only the magnetic field vector and other
atmospheric parameters (e.g., temperature, line-of-sight velocity),
but also their stratifications with height, effectively producing
3-dimensional models of the lower solar atmosphere. In order to enhance
the runtime performance and the usability of SIR we parallelized the
existing code and standardized the input and output formats. This and
other improvements make it feasible to invert extensive high-resolution
data sets within a reasonable amount of computing time. An evaluation
of the speedup of the parallel SIR code shows a substantial improvement
in runtime.
Title: 3D Tracking of small-scale convective upflows
Authors: Lemmerer, Birgit; Hanslmeier, Arnold; Veronig, Astrid;
Muthsam, Herbert; Piantschitsch, Isabell
Bibcode: 2015IAUGA..2247142L
Altcode:
High resolution simulations and observations of the solar photosphere
and convection zone show a new population of small granules with
diameters less than 800 km. The mechanism of formation and dissipation
is still unclear. We developed automated detection and tracking
algorithms to study their evolution as well as their physical and
statistical properties in 2D. We found that small granules may not
result from the fragmentation of larger granules because they show a
small variation in size from the point of appearance at the photosphere
until their dissolution. In this study we present a newly developed 3D
segmentation and tracking algorithm for the analysis of small-scale
convective cells in high resolution simulations. We study the 3D
topology and evolution of convective upflows and their interaction
with strong vortex motions and magnetic flux tubes. We show that the
evolution of small-scale convective upflows in the convection zone is
mainly governed by strong vortex motions within downdrafts rather than
by strong magnetic fields.
Title: Two-fluid 2.5D code for simulations of small scale magnetic
fields in the lower solar atmosphere
Authors: Piantschitsch, Isabell; Amerstorfer, Ute; Thalmann, Julia
Katharina; Hanslmeier, Arnold; Lemmerer, Birgit
Bibcode: 2015IAUGA..2250036P
Altcode:
Our aim is to investigate magnetic reconnection as a result of the
time evolution of magnetic flux tubes in the solar chromosphere. A
new numerical two-fluid code was developed, which will perform a
2.5D simulation of the dynamics from the upper convection zone up
to the transition region. The code is based on the Total Variation
Diminishing Lax-Friedrichs method and includes the effects of
ion-neutral collisions, ionisation/recombination, thermal/resistive
diffusivity as well as collisional/resistive heating. What is innovative
about our newly developed code is the inclusion of a two-fluid model
in combination with the use of analytically constructed vertically
open magnetic flux tubes, which are used as initial conditions for
our simulation. First magnetohydrodynamic (MHD) tests have already
shown good agreement with known results of numerical MHD test problems
like e.g. the Orszag-Tang vortex test, the Current Sheet test or the
Spherical Blast Wave test. Furthermore, the single-fluid approach will
also be applied to the initial conditions, in order to compare the
different rates of magnetic reconnection in both codes, the two-fluid
code and the single-fluid one.
Title: Long-term variation in the Sun's activity caused by magnetic
Rossby waves in the tachocline
Authors: Zaqarashvili, Teimuraz V.; Oliver, Ramon; Hanslmeier, Arnold;
Carbonell, Marc; Ballester, Jose Luis; Gachechiladze, Tamar; Usoskin,
Ilya G.
Bibcode: 2015ApJ...805L..14Z
Altcode: 2015arXiv150502652Z
Long-term records of sunspot number and concentrations of cosmogenic
radionuclides (10Be and 14C) on the Earth reveal the variation of
the Sun's magnetic activity over hundreds and thousands of years. We
identify several clear periods in sunspot, 10Be, and 14C data as
1000, 500, 350, 200, and 100 years. We found that the periods of the
first five spherical harmonics of the slow magnetic Rossby mode in
the presence of a steady toroidal magnetic field of 1200-1300 G in
the lower tachocline are in perfect agreement with the timescales of
observed variations. The steady toroidal magnetic field can be generated
in the lower tachocline either due to the steady dynamo magnetic field
for low magnetic diffusivity or due to the action of the latitudinal
differential rotation on the weak poloidal primordial magnetic field,
which penetrates from the radiative interior. The slow magnetic Rossby
waves lead to variations of the steady toroidal magnetic field in
the lower tachocline, which modulate the dynamo magnetic field and
consequently the solar cycle strength. This result constitutes a key
point for long-term prediction of the cycle strength. According to our
model, the next deep minimum in solar activity is expected during the
first half of this century.
Title: A comparison between the observed and predicted amplitude of
the 24th solar cycle
Authors: Brajša, R.; Verbanac, G.; Sudar, D.; Skokić, I.; Žic,
T.; Hanslmeier, A.; Wöhl, H.; Roth, M.; Mursula, K.; Zhang, L.
Bibcode: 2015CEAB...39..135B
Altcode:
In present work we compared the measured and predicted amplitudes of
the 24th solar cycle. The modified minimum--maximum method,
belonging to the precursor class of methods, was applied to the smoothed
monthly sunspot number values (the ``old'' data set, used before the
change introduced on July 1st, 2015). The maximum of the
24th solar cycle occurred in April 2014 with an amplitude of
R=82 and this observed value is very close to our mean predicted value
R=83. The maximum was significantly weaker than in several previous
cycles. Additionally, a curious solar activity minimum of 2008,
between the solar cycles no.~23 and no.~24 was analysed, as well as
the shape of the maximum profile. The maximum of the 24th
solar cycle had a double-peak, the second one being higher than the
first one. The obtained results represent a strong indication that
the minimum--maximum method is a reliable tool for the solar cycle
prediction, using data available already 3 years before the preceding
minimum of solar activity.
Title: Long time variations of Magnetic Bright Points observed
by Hinode/SOT
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot-Rubio, L.;
Bodnárová, M.; Muller, R.; Bárta, M.; Thonhofer, S.; Hanslmeier, A.
Bibcode: 2015CEAB...39...91U
Altcode:
Magnetic bright points (MBPs) are manifestations of small-scale solar
magnetic flux concentrations, best observable due to their high contrast
in molecular bands like the G-band. Moreover, they are among the most
interesting magnetic features to be studied in high spatial and temporal
resolution in the solar photosphere. Their relevance for solar physics
is not only given by their contribution to fundamental solar plasma
physics on small scales but in addition due to their involvement in
processes like the solar atmospheric heating problem (chromosphere
and corona), their influence on granulation and hence the convective
energy transport, as well as their contribution to the variations in
total solar irradiance caused by their higher relative intensity. In
this ongoing study we focus on the long-time evolution of statistical
parameters of MBPs over the solar cycle. Are parameters like the mean
intensity, average size/diameter, and number of MBPs per unit surface
element variable with time? If so, how do these parameters vary and is
there a relationship to the solar cycle? In the actual contribution
we will discuss preliminary results regarding the variation of the
number of MBPs with time. We saw a decrease in the number of MBPs for
the first years of observation (2006 until 2011) with two distinct
local minima in the years 2009 and 2011. After 2011 the number of MBPs
is increasing again along with an increase in general solar activity
(as seen by the number of sunspots, flares, and CMEs).
Title: The Exo-UV project : habitable stars and the characterization
og UV radiation environment of extrasolar planets
Authors: Abrevaya, Ximena C.; Leitzinger, Martin; Nunez Polcher,
Pablo; Odert, Petra; Lammer, Helmut; Hanslmeier, Arnold
Bibcode: 2014spih.confE..35A
Altcode:
No abstract at ADS
Title: The BIOSUN project: an astrobiological approach to study the
origin of life
Authors: Abrevaya, X. C.; Hanslmeier, A.; Leitzinger, M.; Odert, P.;
Horvath, J. E.; Ribas, I.; Galante, D.; Porto de Mello, G. F.
Bibcode: 2014RMxAC..44..144A
Altcode:
During the early ages of the Earth the magnetic activity of the young
Sun was much stronger than that of the present Sun, in particular for
radiation emitted below 1700 Å. Such enhanced radiation fluxes could
play a role in the evolution of planetary atmospheres, their surface
conditions and in the origin and evolution of life. Solar stellar
analogs could provide information about the characteristics of the
young Sun, and therefore this radiation environment. The objective
of this project is to focus on the radiation emission features of the
young Sun through solar stellar analogs to 1) Characterize the radiation
environment of the early Earth and other planetary bodies of the Solar
System that are or could have been suitable for life. 2)Reproduce this
radiation environment under laboratory simulated conditions to explore:
Whether cells could survive at that level of radiation on the early
Earth confronting that with the microbial fossil record. Early Mars
and Europa will be also tested; b) The possibility of ``transfer"
of microorganisms between Mars-Earth or Venus-Earth at that time. For
Mars studies we consider as a model the Nakhla meteorite and halites;
c) The formation, inflow and outflow of some prebiotic molecules in
the early planetary conditions. Finally, the experimental approach will
be carried out exposing microorganisms/molecules to this environments
under laboratory simulated conditions, according to the data obtained
previously.
Title: Origin and Stability of Exomoon Atmospheres: Implications
for Habitability
Authors: Lammer, Helmut; Schiefer, Sonja-Charlotte; Juvan, Ines; Odert,
Petra; Erkaev, Nikolai V.; Weber, Christof; Kislyakova, Kristina G.;
Güdel, Manuel; Kirchengast, Gottfried; Hanslmeier, Arnold
Bibcode: 2014OLEB...44..239L
Altcode: 2014OLEB..tmp...23L; 2015arXiv150606529L
We study the origin and escape of catastrophically outgassed volatiles
(H2O, CO2) from exomoons with Earth-like
densities and masses of 0.1, 0.5 and 1 M ⊕ orbiting an
extra-solar gas giant inside the habitable zone of a young active
solar-like star. We apply a radiation absorption and hydrodynamic
upper atmosphere model to the three studied exomoon cases. We model
the escape of hydrogen and dragged dissociation products O and C during
the activity saturation phase of the young host star. Because the soft
X-ray and EUV radiation of the young host star may be up to ~100 times
higher compared to today's solar value during the first 100 Myr after
the system's origin, an exomoon with a mass < 0.25 M ⊕
located in the HZ may not be able to keep an atmosphere because of
its low gravity. Depending on the spectral type and XUV activity
evolution of the host star, exomoons with masses between ~0.25 and
0.5 M ⊕ may evolve to Mars-like habitats. More massive
bodies with masses >0.5 M ⊕, however, may evolve to
habitats that are a mixture of Mars-like and Earth-analogue habitats,
so that life may originate and evolve at the exomoon's surface.
Title: A search for flares and mass ejections on young late-type
stars in the open cluster Blanco-1
Authors: Leitzinger, M.; Odert, P.; Greimel, R.; Korhonen, H.;
Guenther, E. W.; Hanslmeier, A.; Lammer, H.; Khodachenko, M. L.
Bibcode: 2014MNRAS.443..898L
Altcode: 2014arXiv1406.2734L
We present a search for stellar activity (flares and mass ejections)
in a sample of 28 stars in the young open cluster Blanco-1. We use
optical spectra obtained with European Southern Observatory's Visible
Multi-Object Spectrograph installed on the Very Large Telescope. From
the total observing time of ∼5 h, we find four Hα flares but no
distinct indication of coronal mass ejections (CMEs) on the investigated
dK-dM stars. Two flares show `dips' in their light curves right before
their impulsive phases which are similar to previous discoveries in
photometric light curves of active dMe stars. We estimate an upper
limit of <4 CMEs per day per star and discuss this result with
respect to a empirical estimation of the CME rate of main-sequence
stars. We find that we should have detected at least one CME per star
with a mass of ≤ 3 × 1017 g depending on the star's X-ray
luminosity, but the estimated Hα fluxes associated with these masses
are below the detection limit of our observations. We conclude that
the parameter which mainly influences the detection of stellar CMEs
using the method of Doppler-shifted emission caused by moving plasma
is not the spectral resolution/velocity but the flux/mass of the CME.
Title: Future mmVLBI Research with ALMA: A European vision
Authors: Tilanus, R. P. J.; Krichbaum, T. P.; Zensus, J. A.; Baudry,
A.; Bremer, M.; Falcke, H.; Giovannini, G.; Laing, R.; van Langevelde,
H. J.; Vlemmings, W.; Abraham, Z.; Afonso, J.; Agudo, I.; Alberdi,
A.; Alcolea, J.; Altamirano, D.; Asadi, S.; Assaf, K.; Augusto, P.;
Baczko, A-K.; Boeck, M.; Boller, T.; Bondi, M.; Boone, F.; Bourda,
G.; Brajsa, R.; Brand, J.; Britzen, S.; Bujarrabal, V.; Cales, S.;
Casadio, C.; Casasola, V.; Castangia, P.; Cernicharo, J.; Charlot,
P.; Chemin, L.; Clenet, Y.; Colomer, F.; Combes, F.; Cordes, J.;
Coriat, M.; Cross, N.; D'Ammando, F.; Dallacasa, D.; Desmurs, J-F.;
Eatough, R.; Eckart, A.; Eisenacher, D.; Etoka, S.; Felix, M.; Fender,
R.; Ferreira, M.; Freeland, E.; Frey, S.; Fromm, C.; Fuhrmann, L.;
Gabanyi, K.; Galvan-Madrid, R.; Giroletti, M.; Goddi, C.; Gomez, J.;
Gourgoulhon, E.; Gray, M.; di Gregorio, I.; Greimel, R.; Grosso, N.;
Guirado, J.; Hada, K.; Hanslmeier, A.; Henkel, C.; Herpin, F.; Hess,
P.; Hodgson, J.; Horns, D.; Humphreys, E.; Hutawarakorn Kramer, B.;
Ilyushin, V.; Impellizzeri, V.; Ivanov, V.; Julião, M.; Kadler, M.;
Kerins, E.; Klaassen, P.; van 't Klooster, K.; Kording, E.; Kozlov,
M.; Kramer, M.; Kreikenbohm, A.; Kurtanidze, O.; Lazio, J.; Leite,
A.; Leitzinger, M.; Lepine, J.; Levshakov, S.; Lico, R.; Lindqvist,
M.; Liuzzo, E.; Lobanov, A.; Lucas, P.; Mannheim, K.; Marcaide, J.;
Markoff, S.; Martí-Vidal, I.; Martins, C.; Masetti, N.; Massardi,
M.; Menten, K.; Messias, H.; Migliari, S.; Mignano, A.; Miller-Jones,
J.; Minniti, D.; Molaro, P.; Molina, S.; Monteiro, A.; Moscadelli,
L.; Mueller, C.; Müller, A.; Muller, S.; Niederhofer, F.; Odert,
P.; Olofsson, H.; Orienti, M.; Paladino, R.; Panessa, F.; Paragi,
Z.; Paumard, T.; Pedrosa, P.; Pérez-Torres, M.; Perrin, G.; Perucho,
M.; Porquet, D.; Prandoni, I.; Ransom, S.; Reimers, D.; Rejkuba, M.;
Rezzolla, L.; Richards, A.; Ros, E.; Roy, A.; Rushton, A.; Savolainen,
T.; Schulz, R.; Silva, M.; Sivakoff, G.; Soria-Ruiz, R.; Soria, R.;
Spaans, M.; Spencer, R.; Stappers, B.; Surcis, G.; Tarchi, A.; Temmer,
M.; Thompson, M.; Torrelles, J.; Truestedt, J.; Tudose, V.; Venturi,
T.; Verbiest, J.; Vieira, J.; Vielzeuf, P.; Vincent, F.; Wex, N.;
Wiik, K.; Wiklind, T.; Wilms, J.; Zackrisson, E.; Zechlin, H.
Bibcode: 2014arXiv1406.4650T
Altcode:
Very long baseline interferometry at millimetre/submillimetre
wavelengths (mmVLBI) offers the highest achievable spatial
resolution at any wavelength in astronomy. The anticipated inclusion
of ALMA as a phased array into a global VLBI network will bring
unprecedented sensitivity and a transformational leap in capabilities
for mmVLBI. Building on years of pioneering efforts in the US and
Europe the ongoing ALMA Phasing Project (APP), a US-led international
collaboration with MPIfR-led European contributions, is expected to
deliver a beamformer and VLBI capability to ALMA by the end of 2014
(APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on
the future use of mmVLBI by the international users community from
a European viewpoint. Firstly, it highlights the intense science
interest in Europe in future mmVLBI observations as compiled from
the responses to a general call to the European community for future
research projects. A wide range of research is presented that includes,
amongst others: - Imaging the event horizon of the black hole at the
centre of the Galaxy - Testing the theory of General Relativity an/or
searching for alternative theories - Studying the origin of AGN jets
and jet formation - Cosmological evolution of galaxies and BHs, AGN
feedback - Masers in the Milky Way (in stars and star-forming regions) -
Extragalactic emission lines and astro-chemistry - Redshifted absorption
lines in distant galaxies and study of the ISM and circumnuclear gas -
Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing
fundamental physical constants
Title: Two-dimensional segmentation of small convective patterns in
radiation hydrodynamics simulations
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.; Thonhofer,
S.; Grimm-Strele, H.; Kariyappa, R.
Bibcode: 2014A&A...563A.107L
Altcode: 2015arXiv150500325L
Context. Recent results from high-resolution solar granulation
observations indicate the existence of a population of small granular
cells that are smaller than 600 km in diameter. These small convective
cells strongly contribute to the total area of granules and are located
in the intergranular lanes, where they form clusters and chains.
Aims: We study high-resolution radiation hydrodynamics simulations of
the upper convection zone and photosphere to detect small granular
cells, define their spatial alignment, and analyze their physical
properties.
Methods: We developed an automated image-segmentation
algorithm specifically adapted to high-resolution simulations to
identify granules. The resulting segmentation masks were applied to
physical quantities, such as intensity and vertical velocity profiles,
provided by the simulation. A new clustering algorithm was developed
to study the alignment of small granular cells.
Results:
Small granules make a distinct contribution to the total area of
granules and form clusters of chain-like alignments. The simulation
profiles demonstrate a different nature for small granular cells
because they exhibit on average lower intensities, lower horizontal
velocities, and are located deeper inside of convective layers than
regular granules. Their intensity distribution deviates from a normal
distribution as known for larger granules, and follows a Weibull
distribution.
Title: An analysis of the solar differential rotation from the
Kanzelhöhe sunspot drawings
Authors: Poljančić Beljan, I.; Jurdana-Šepić, R.; Čargonja, M.;
Brajša, R.; Hržina, D.; Pötzi, W.; Hanslmeier, A.
Bibcode: 2014CEAB...38...87P
Altcode:
We present here the results of the behaviour of the solar differential
rotation during solar cycles no. 20 and no. 22, derived from Kanzelhöhe
sunspot drawings (Kanzelhöhe Observatory for Solar and Environmental
Research, University of Graz, Austria). The positions of sunspot groups
were determined using a special software Sungrabber. Sunspot groups were
identified with the help of the Greenwich Photoheliographic Results
(GPR) and Debrecen Photoheliographic Data (DPD) databases, covering
solar cycles no. 20 and no. 22, respectively. In order to calculate
the sidereal angular rotation rate ω and subsequently solar rotation
parameters A and B we used two procedures: a) daily motion of sunspot
groups and b) linear least-square fit from the function CMD(t) for each
tracer, where CMD denotes the Central Meridian Distance. The sample
was limited to ±58° in CMD in order to avoid solar limb effects. We
mainly investigated velocity patterns depending on the solar cycle
phase and latitude.
Title: Fractal Dimension Analysis of Solar Granulation- Boxcounting
dimension
Authors: Hanslmeier, A.; Lemmerer, B.; Utz, D.; Muller, R.; Muthsam, H.
Bibcode: 2014CEAB...38...11H
Altcode:
The fractal dimension of high resolution Hinode solar granulation
observations and numerical simulations is studied and the results are
compared. These observations are not influenced by atmospheric seeing
conditions and therefore allow a more realistic estimate of the fractal
dimension than in previous works. Though arriving at similar results for
observations and simulation data, non integer fractal dimension <2,
some differences in the numerical values occur, and these are discussed.
Title: Detection of small convective patterns in observations and
simulations
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.;
Grimm-Strele, H.; Thonhofer, S.; Piantschitsch, I.
Bibcode: 2014CEAB...38...19L
Altcode:
Recent results from high resolution solar granulation observations
indicate the existence of a population of small granular cells on
scales below 600 km in diameter, located in the intergranular lanes. We
studied a set of Hinode SOT images and high resolution radiation
hydrodynamics simulations in order to analyze small granular cells and
to study their physical properties. An automated image segmentation
algorithm specifically adapted to high resolution simulations for the
identification of granules was developed. The algorithm was also used
to analyze and compare physical quantities provided by the simulation
and the observations. We found that small granules make a distinct
contribution to the total area of granules. Both in observations and
simulations, small granular cells exhibit on average lower intensities
and vertical velocities.
Title: Solar Ca II K plage regions as proxies for magnetic fields
of solar like stars
Authors: Guttenbrunner, S.; Hanslmeier, A.; Utz, D.; Lemmerer, B.;
Piantschitsch, I.; Thonhofer, S.
Bibcode: 2014CEAB...38...81G
Altcode:
Solar plage regions can be observed directly, whereas plage regions as
well as star-spots on solar like stars, can only be detected via their
contribution to spectral irradiances of these stars. Such a spectral
irradiance can be modelled by fractions belonging to the quiet star,
the plage regions, and the star-spots. The idea is, to measure these
fractions as well as the intensity enhancement due to plage regions
on our Sun and then use this information to be able to model solar
like stars. We verify the close connection between the size of the
plage regions and the luminosity of the Sun, given by a correlation
coefficient of 0.822. The size of the plage regions varies from 0%,
when the Sun is very quiet, up to 2.7% for a more active Sun (a complete
solar cycle is not yet analysed and hence our study does not contain an
activity maximum). The used data sets are full-disc images taken by the
RISE/PSPT instrument during the period from 2005 to 2012, at the MLSO.
Title: Two-Fluid 2.5D MHD-Code for Simulations in the Solar Atmosphere
Authors: Piantschitsch, I.; Amerstorfer, U.; Thalmann, J.; Utz, D.;
Hanslmeier, A.; Bárta, M.; Thonhofer, S.; Lemmerer, B.
Bibcode: 2014CEAB...38...59P
Altcode:
We investigate magnetic reconnection due to the evolution of magnetic
flux tubes in the solar chromosphere. We developed a new numerical
two-fluid magnetohydrodynamic (MHD) code which will perform a 2.5D
simulation of the dynamics from the upper convection zone up to the
transition region. Our code is based on the Total Variation Diminishing
Lax-Friedrichs scheme and makes use of an alternating-direction implicit
method, in order to accommodate the two spatial dimensions. Since we
apply a two-fluid model for our simulations, the effects of ion-neutral
collisions, ionization/recombination, thermal/resistive diffusivity
and collisional/resistive heating are included in the code. As initial
conditions for the code we use analytically constructed vertically open
magnetic flux tubes within a realistic stratified atmosphere. Initial
MHD tests have already shown good agreement with known results of
numerical MHD test problems like e.g. the Orszag-Tang vortex test.
Title: New insights into the evolution of magnetic bright point
plasma parameters
Authors: Utz, Dominik; Hanslmeier, Arnold; Bellot Rubio, L. R.;
Del Toro Iniesta, Jose Carlos; Jurcak, Jan
Bibcode: 2014cosp...40E3448U
Altcode:
The dynamics within the solar atmosphere are governed by the Suńs
magnetic fields. In the recent years the resolution limits were steadily
driven up by better and better instruments and telescopes (like Hinode,
Sunrise, NST, Gregor, ..) leading to higher resolved data. Therefore
the interest in ever smaller magnetic field structures within the solar
atmosphere rises. Among the smallest yet identified structures are
so-called magnetic bright points (MBPs). These features are thought to
be made up of single flux tubes and they have been studied exhaustively
in the Fraunhofer G-band since the 70´s of the last century. They are
important features not only due to their small scale (about 200 km in
diameter) and hence used as proxies for the smallest solar magnetic
field physics and processes, but also because they are involved in
topics like the chromospheric/coronal heating problem or the total
solar irradiance variation. In the current contribution we want to
study the evolution of important plasma parameters of MBPs, such
as temperature, magnetic field strength and line of sight velocity,
to get a deeper understanding of the involved physics and occuring
processes. Among the used data will be G-band filtergam data from
Hinode/SOT and spectro-polarimetric data from the IMaX instrument
onboard the Sunrise mission.
Title: New insights into the temporal evolution of MBPs
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.;
Jurčak, J.; Thonhofer, S.; Bodnárová, M.; Hanslmeier, A.; Lemmerer,
B.; Piantschitsch, I.; Guttenbrunner, S.
Bibcode: 2014CEAB...38...73U
Altcode:
Magnetic bright points (MBPs) are among the most fascinating and
interesting manifestations of small-scale solar magnetic fields. In the
present work the temporal evolution of MBPs is followed in data sets
taken by the Hinode satellite. The analysed data and obtained results
confirm a recently presented study done with Sunrise/IMaX data, namely
that MBPs are features undergoing fast evolution with magnetic fields
starting around the equipartition field strength, then showing strong
downflows (between 2 to 4 km/s) causing the magnetic field to amplify
into the kG range (700 to 1500 G) before dissolving again. Furthermore
the initial field inclinations depend on the initial magnetic field
strengths and show an evolution with more vertical angles at some
point during the evolution.
Title: Parallelization of the SIR code
Authors: Thonhofer, S.; Bellot Rubio, L. R.; Utz, D.; Jurčak, J.;
Hanslmeier, A.; Piantschitsch, I.; Pauritsch, J.; Lemmerer, B.;
Guttenbrunner, S.
Bibcode: 2014CEAB...38...31T
Altcode:
A high-resolution 3-dimensional model of the photospheric magnetic
field is essential for the investigation of small-scale solar magnetic
phenomena. The SIR code is an advanced Stokes-inversion code that
deduces physical quantities, e.g. magnetic field vector, temperature,
and LOS velocity, from spectropolarimetric data. We extended this code
by the capability of directly using large data sets and inverting the
pixels in parallel. Due to this parallelization it is now feasible to
apply the code directly on extensive data sets. Besides, we included
the possibility to use different initial model atmospheres for the
inversion, which enhances the quality of the results.
Title: XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres
of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape
Authors: Kislyakova, Kristina G.; Lammer, Helmut; Holmström, Mats;
Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger,
Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Güdel, Manuel;
Hanslmeier, Arnold
Bibcode: 2013AsBio..13.1030K
Altcode: 2012arXiv1212.4710K
We study the interactions between the stellar wind plasma flow of a
typical M star, such as GJ 436, and hydrogen-rich upper atmospheres of
an Earth-like planet and a "super-Earth" with the radius of 2 R_Earth
and a mass of 10 M_Earth, located within the habitable zone at ~0.24
AU. We investigate the formation of extended atomic hydrogen coronae
under the influences of the stellar XUV flux (soft X-rays and EUV),
stellar wind density and velocity, shape of a planetary obstacle (e.g.,
magnetosphere, ionopause), and the loss of planetary pick-up ions on
the evolution of hydrogen-dominated upper atmospheres. Stellar XUV
fluxes which are 1, 10, 50 and 100 times higher compared to that of the
present-day Sun are considered and the formation of high-energy neutral
hydrogen clouds around the planets due to the charge-exchange reaction
under various stellar conditions have been modeled. Charge-exchange
between stellar wind protons with planetary hydrogen atoms, and
photoionization, leads to the production of initially cold ions of
planetary origin. We found that the ion production rates for the
studied planets can vary over a wide range, from ~1.0x10^{25} s^{-1}
to ~5.3x10^{30} s^{-1}, depending on the stellar wind conditions and
the assumed XUV exposure of the upper atmosphere. Our findings indicate
that most likely the majority of these planetary ions are picked up
by the stellar wind and lost from the planet. Finally, we estimate
the long-time non-thermal ion pick-up escape for the studied planets
and compare them with the thermal escape. According to our estimates,
non-thermal escape of picked up ionized hydrogen atoms over a planet's
lifetime varies between ~0.4 Earth ocean equivalent amounts of hydrogen
(EO_H) to <3 EO_H and usually is several times smaller in comparison
to the thermal atmospheric escape rates.
Title: XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of
Terrestrial Planets. Part I: Atmospheric Expansion and Thermal Escape
Authors: Erkaev, Nikolai V.; Lammer, Helmut; Odert, Petra; Kulikov,
Yuri N.; Kislyakova, Kristina G.; Khodachenko, Maxim L.; Güdel,
Manuel; Hanslmeier, Arnold; Biernat, Helfried
Bibcode: 2013AsBio..13.1011E
Altcode: 2012arXiv1212.4982E
The recently discovered low-density "super-Earths" Kepler-11b,
Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b
represent most likely planets which are surrounded by dense H/He
envelopes or contain deep H2O oceans also surrounded by dense hydrogen
envelopes. Although these "super-Earths" are orbiting relatively close
to their host stars, they have not lost their captured nebula-based
hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus it
is interesting to estimate the maximum possible amount of atmospheric
hydrogen loss from a terrestrial planet orbiting within the habitable
zone of late main sequence host stars. For studying the thermosphere
structure and escape we apply a 1-D hydrodynamic upper atmosphere model
which solves the equations of mass, momentum and energy conservation
for a planet with the mass and size of the Earth and for a "super-Earth"
with a size of 2 R_Earth and a mass of 10 M_Earth. We calculate volume
heating rates by the stellar soft X-ray and EUV radiation and expansion
of the upper atmosphere, its temperature, density and velocity structure
and related thermal escape rates during planet's life time. Moreover,
we investigate under which conditions both planets enter the blow-off
escape regime and may therefore experience loss rates which are close
to the energy-limited escape. Finally we discuss the results in the
context of atmospheric evolution and implications for habitability of
terrestrial planets in general.
Title: Variations of Magnetic Bright Point Properties with Longitude
and Latitude as Observed by Hinode/SOT G-band Data
Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Kühner, O.; Muller,
R.; Jurčák, J.; Lemmerer, B.
Bibcode: 2013SoPh..284..363U
Altcode: 2012arXiv1212.1310U
Small-scale magnetic fields can be observed on the Sun in
high-resolution G-band filtergrams as magnetic bright points (MBPs). We
study Hinode/Solar Optical Telescope (SOT) longitude and latitude scans
of the quiet solar surface taken in the G-band in order to characterise
the centre-to-limb dependence of MBP properties (size and intensity). We
find that the MBP's sizes increase and their intensities decrease
from the solar centre towards the limb. The size distribution can be
fitted using a log-normal function. The natural logarithm of the mean
(μ parameter) of this function follows a second-order polynomial
and the generalised standard deviation (σ parameter) follows a
fourth-order polynomial or equally well (within statistical errors)
a sine function. The brightness decrease of the features is smaller
than one would expect from the normal solar centre-to-limb variation;
that is to say, the ratio of a MBP's brightness to the mean intensity
of the image increases towards the limb. The centre-to-limb variations
of the intensities of the MBPs and the quiet-Sun field can be fitted by
a second-order polynomial. The detailed physical process that results
in an increase of a MBP's brightness and size from Sun centre to the
limb is not yet understood and has to be studied in more detail in
the future.
Title: Magnetic field strength distribution of magnetic bright points
inferred from filtergrams and spectro-polarimetric data
Authors: Utz, D.; Jurčák, J.; Hanslmeier, A.; Muller, R.; Veronig,
A.; Kühner, O.
Bibcode: 2013A&A...554A..65U
Altcode: 2013arXiv1304.5508U
Context. Small scale magnetic fields can be observed on the Sun in
G-band filtergrams as magnetic bright points (MBPs) or identified in
spectro-polarimetric measurements due to enhanced signals of Stokes
profiles. These magnetic fields and their dynamics play a crucial role
in understanding the coronal heating problem and also in surface dynamo
models. MBPs can theoretically be described to evolve out of a patch of
a solar photospheric magnetic field with values below the equipartition
field strength by the so-called convective collapse model. After the
collapse, the magnetic field of MBPs reaches a higher stable magnetic
field level.
Aims: The magnetic field strength distribution of
small scale magnetic fields as seen by MBPs is inferred. Furthermore,
we want to test the model of convective collapse and the theoretically
predicted stable value of about 1300 G.
Methods: We used four
different data sets of high-resolution Hinode/SOT observations that were
recorded simultaneously with the broadband filter device (G-band, Ca
II-H) and the spectro-polarimeter. To derive the magnetic field strength
distribution of these small scale features, the spectropolarimeter
(SP) data sets were treated by the Merlin inversion code. The four data
sets comprise different solar surface types: active regions (a sunspot
group and a region with pores), as well as quiet Sun.
Results:
In all four cases the obtained magnetic field strength distribution of
MBPs is similar and shows peaks around 1300 G. This agrees well with the
theoretical prediction of the convective collapse model. The resulting
magnetic field strength distribution can be fitted in each case by a
model consisting of log-normal components. The important parameters,
such as geometrical mean value and multiplicative standard deviation,
are similar in all data sets, so only the relative weighting of the
components is different.
Title: Observations and Modeling of the Emerging Extreme-ultraviolet
Loops in the Quiet Sun as Seen with the Solar Dynamics Observatory
Authors: Chitta, L. P.; Kariyappa, R.; van Ballegooijen, A. A.;
DeLuca, E. E.; Hasan, S. S.; Hanslmeier, A.
Bibcode: 2013ApJ...768...32C
Altcode: 2013arXiv1303.3426C
We used data from the Helioseismic and Magnetic Imager (HMI) and the
Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory
(SDO) to study coronal loops at small scales, emerging in the quiet
Sun. With HMI line-of-sight magnetograms, we derive the integrated
and unsigned photospheric magnetic flux at the loop footpoints in the
photosphere. These loops are bright in the EUV channels of AIA. Using
the six AIA EUV filters, we construct the differential emission measure
(DEM) in the temperature range 5.7-6.5 in log T (K) for several hours
of observations. The observed DEMs have a peak distribution around
log T ≈ 6.3, falling rapidly at higher temperatures. For log T <
6.3, DEMs are comparable to their peak values within an order of
magnitude. The emission-weighted temperature is calculated, and its
time variations are compared with those of magnetic flux. We present
two possibilities for explaining the observed DEMs and temperatures
variations. (1) Assuming that the observed loops are composed of
a hundred thin strands with certain radius and length, we tested
three time-dependent heating models and compared the resulting DEMs
and temperatures with the observed quantities. This modeling used
enthalpy-based thermal evolution of loops (EBTEL), a zero-dimensional
(0D) hydrodynamic code. The comparisons suggest that a medium-frequency
heating model with a population of different heating amplitudes can
roughly reproduce the observations. (2) We also consider a loop model
with steady heating and non-uniform cross-section of the loop along
its length, and find that this model can also reproduce the observed
DEMs, provided the loop expansion factor γ ~ 5-10. More observational
constraints are required to better understand the nature of coronal
heating in the short emerging loops on the quiet Sun.
Title: The chaotic solar cycle. II. Analysis of cosmogenic
10Be data
Authors: Hanslmeier, A.; Brajša, R.; Čalogović, J.; Vršnak,
B.; Ruždjak, D.; Steinhilber, F.; MacLeod, C. L.; Ivezić, Ž.;
Skokić, I.
Bibcode: 2013A&A...550A...6H
Altcode: 2014arXiv1402.2776H
Context. The variations of solar activity over long time intervals using
a solar activity reconstruction based on the cosmogenic radionuclide
10Be measured in polar ice cores are studied.
Aims:
The periodicity of the solar activity cycle is studied. The solar
activity cycle is governed by a complex dynamo mechanism. Methods
of nonlinear dynamics enable us to learn more about the regular
and chaotic behavior of solar activity. In this work we compare
our earlier findings based on 14C data with the results
obtained using 10Be data.
Methods: By applying
methods of nonlinear dynamics, the solar activity cycle is studied
using solar activity proxies that have been reaching into the past
for over 9300 years. The complexity of the system is expressed by
several parameters of nonlinear dynamics, such as embedding dimension
or false nearest neighbors, and the method of delay coordinates is
applied to the time series. We also fit a damped random walk model,
which accurately describes the variability of quasars, to the solar
10Be data and investigate the corresponding power spectral
distribution. The periods in the data series were searched by the
Fourier and wavelet analyses.
Results: The solar activity on the
long-term scale is found to be on the edge of chaotic behavior. This
can explain the observed intermittent period of longer lasting solar
activity minima. Filtering the data by eliminating variations below
a certain period (the periods of 380 yr and 57 yr were used) yields a
far more regular behavior of solar activity. A comparison between the
results for the 10Be data with the 14C data shows
many similarities. Both cosmogenic isotopes are strongly correlated
mutually and with solar activity. Finally, we find that a series of
damped random walk models provides a good fit to the 10Be
data with a fixed characteristic time scale of 1000 years, which is
roughly consistent with the quasi-periods found by the Fourier and
wavelet analyses.
Conclusions: The time series of solar activity
proxies used here clearly shows that solar activity behaves differently
from random data. The unfiltered data exhibit a complex dynamics that
becomes more regular when filtering the data. The results indicate
that solar activity proxies are also influenced by other than solar
variations and reflect solar activity only on longer time scales.
Title: UV Radiation of the Young Sun and its Implications for Life
in the Solar System
Authors: Abrevaya, X. C.; Hanslmeier, A.; Leitzinger, M.; Odert, P.;
Mauas, P. J. D.; Buccino, A. P.
Bibcode: 2013CEAB...37..649A
Altcode:
UV radiation is thought to have played an important role in the
origin of life on Earth. To estimate these levels of UV radiation,
we computed the UVC fluxes from HST/STIS and IUE spectra of the young
solar analogs κ^1 Cet and χ^1 Ori. In the future experiments with
extremophilic microorganisms we will use these resulting UVC-levels
to test the probability of the survival, and therefore, the existence
of this kind of life at Early Earth, Early Mars and Early Europa.
Title: Creating 3-dimensional Models of the Photosphere using the
SIR Code
Authors: Thonhofer, S.; Utz, D.; Jurčák, J.; Pauritsch, J.;
Hanslmeier, A.; Lemmerer, B.
Bibcode: 2013CEAB...37..471T
Altcode:
A high-resolution 3-dimensional model of the photospheric magnetic
field is essential for the investigation of magnetic features such
as sunspots, pores or smaller elements like single flux tubes seen
as magnetic bright points. The SIR code is an advanced inversion code
that retrieves physical quantities, e.g. magnetic field, from Stokes
profiles. Based on this code, we developed a program for automated
inversion of Hinode SOT/SP data and for storing these results in
3-dimensional data cubes in the form of fits files. We obtained models
of the temperature, magnetic field strength, magnetic field angles
and LOS-velocity in a region of the quiet sun. We will give a first
discussion of those parameters in regards of small scale magnetic
fields and what we can obtain and learn in the future.
Title: A Magnetic Bright Point Case Study
Authors: Utz, D.; Jurčák, J.; Bellot-Rubio, L.; del Toro Iniesta,
J. C.; Thonhofer, S.; Hanslmeier, A.; Veronig, A.; Muller, R.;
Lemmerer, B.
Bibcode: 2013CEAB...37..459U
Altcode:
Due to its magnetic fields our host star - the Sun - becomes the
interesting object for research as we know it. The magnetic fields
themselves cover different spatial, lifetime and strength scales and
reach down from enormous flux concentrations like active sunspot
groups to single isolated magnetic flux tubes and even weaker,
predominantly inclined intranetwork structures. Flux tubes can be seen
in filtergram observations as magnetic bright points (MBPs). They are
of interest for research not only due to their sheer existence but
due to their important role in atmospheric heating (wave heating as
well as reconnection processes), to their role in the understanding
of creation and annihilation of magnetic fields as well as to their
influence on the total solar irradiance variation. In this study we
present a close look onto an evolutionary track of an MBP from its
formation to its disintegration. Physical quantities of MBPs like
their magnetic field strength and inclination, their line-of-sight
velocity, and their temperature at different heights are inferred
from the inversion of spectropolarimetric data. Original data are
taken from the Sunrise/IMaX instrument and constitute a time series
of some 60 min. The presented case resembles the convective collapse
model and is in agreement with previous studies.
Title: Faszination Astronomie
Authors: Hanslmeier, Arnold
Bibcode: 2013fate.book.....H
Altcode:
No abstract at ADS
Title: 3D Image Segmentation Applied to Solar RHD Simulations
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.;
Grimm-Strele, H.; Thonhofer, S.; Muthsam, H.
Bibcode: 2013CEAB...37..477L
Altcode:
3D simulation models based on Magneto-hydrodynamics (MHD) and
Radiation-hydrodynamics (RHD) equations give insight into the evolution
of magnetic fields and convective motions in the solar atmosphere. The
analysis of huge amount of data require the development of automated
segmentation algorithms. A newly developed 3D segmentation algorithm
will be introduced in order to extract and trace convective downflows
and is applied to the numerical simulation code ANTARES. The algorithm
segments strong downflow velocities resulting in tube-like structures
which enables us to analyze the motions with respect to variations
of physical parameters over height as well as their evolution with
time. Analysis of the segmented structures shows that narrower parts
tend to have higher velocities. High temporal variations in the lower
model photosphere indicate less stable structures over time in this
layer. The mean temperature within the downflow is cooler than in the
horizontally averaged simulation box. The analysis of the behavior of
vortex flows demonstrates a constant high vorticity within the segment
and a linear dependency to the vertical velocity. It appears that
vortex flows are strongly present within dominant convective downflows.
Title: The Solar Convection over a Solar Cycle
Authors: Hanslmeier, A.; Muller, R.; Utz, D.
Bibcode: 2012ASPC..463..115H
Altcode:
We study the variation of granular size and contrast over a solar
activity cycle. Two different homogeneous data samples were used, from
Pic du Midi and from Hinode. The results do not confirm previous values
cited in the literature. From the Hinode data the granulation seems to
be constant, the trend found may be of instrumental degradation. We
try to explain the result by other observations like the total solar
irradiance variation. This variation was small over the past five
years and may explain why in the case of Hinode data no significant
variations were found.
Title: The Dwarf project: Eclipsing binaries - precise clocks to
discover exoplanets
Authors: Pribulla , T.; Vaňko, M.; Ammler-von Eiff, M.; Andreev,
M.; Aslantürk, A.; Awadalla, N.; Baluďanský, D.; Bonanno,
A.; Božić, H.; Catanzaro, G.; Çelik, L.; Christopoulou, P. E.;
Covino, E.; Cusano, F.; Dimitrov, D.; Dubovský, P.; Eigmueller, P.;
Esmer, E. M.; Frasca, A.; Hambálek, Ľ.; Hanna, M.; Hanslmeier,
A.; Kalomeni, B.; Kjurkchieva, D. P.; Krushevska, V.; Kudzej, I.;
Kundra, E.; Kuznyetsova, Yu.; Lee, J. W.; Leitzinger, M.; Maciejewski,
G.; Moldovan, D.; Morais, M. H. M.; Mugrauer, M.; Neuhäuser, R.;
Niedzielski, A.; Odert, P.; Ohlert, J.; Özavcı, İ.; Papageorgiou,
A.; Parimucha, Š.; Poddaný, S.; Pop, A.; Raetz, M.; Raetz, S.;
Romanyuk, Ya.; Ruždjak, D.; Schulz, J.; Şenavcı, H. V.; Srdoc, G.;
Szalai, T.; Székely, P.; Sudar, D.; Tezcan, C. T.; Törün, M. E.;
Turcu, V.; Vince, O.; Zejda, M.
Bibcode: 2012AN....333..754P
Altcode: 2012arXiv1206.6709P
\footnotesize We present a new observational campaign, Dwarf, aimed
at detection of circumbinary extrasolar planets using the timing of
the minima of low-mass eclipsing binaries. The observations will
be performed within an extensive network of relatively small to
medium-size telescopes with apertures of ∼20-200 cm. The starting
sample of the objects to be monitored contains (i) low-mass eclipsing
binaries with M and K components, (ii) short-period binaries with a sdB
or sdO component, and (iii) post-common-envelope systems containing a
WD, which enable to determine minima with high precision. Since the
amplitude of the timing signal increases with the orbital period of
an invisible third component, the timescale of the project is long,
at least 5-10 years. The paper gives simple formulas to estimate the
suitability of individual eclipsing binaries for the circumbinary planet
detection. Intrinsic variability of the binaries (photospheric spots,
flares, pulsation etc.) limiting the accuracy of the minima timing
is also discussed. The manuscript also describes the best observing
strategy and methods to detect cyclic timing variability in the minima
times indicating the presence of circumbinary planets. First test
observations of the selected targets are presented.
Title: Escape of protoatmospheres and their role in atmosphere
evolution
Authors: Lammer, H.; Kislyakova, K. G.; Erkaev, N. V.; Odert, P.;
Kulikov, Y. N.; Hanslmeier, A.
Bibcode: 2012epsc.conf..564L
Altcode: 2012espc.conf..564L
We discuss the origin and evolution of the atmosphere of early Venus,
Earth, Mars and super- Earths. It will be shown that the formation age
of a terrestrial planet, its mass and size, as well as the planet's
lifetime in the EUV-saturated early phase of its host star play a
significant role in the escape of the planet's protoatmosphere and
related atmosphere evolution.
Title: Dependence of Velocity Distributions of Small-Scale Magnetic
Fields Derived from Hinode/SOT G-band Filtergrams on the Temporal
Resolution of the Used Data Sets
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Rybák,
J.; Muthsam, H.
Bibcode: 2012ASPC..454...55U
Altcode:
The dynamics of isolated small-scale fields in terms of velocities of
magnetic bright points (MBPs) is addressed in this contribution. The
empirically determined linear relation between the observed width
parameter for the Rayleigh velocity distribution of MBPs versus the
temporal cadence of the acquired data is studied by simulations and a
simple analytical model. The results of the model and the simulation
agree with the found relation for the observations. The conclusion we
draw from the model is that there may be no characteristic velocity
for MBPs at all.
Title: Keynote: Pathways to Earth-Like Nitrogen Atmospheres:
Implications for the Search for Exo-Earth
Authors: Lammer, H.; Kislyakova, K. G.; Odert, P.; Leitzinger, M.;
Schwarz, R.; Pilat-Lohinger, E.; Güdel, M.; Khodachenko, M. L.;
Kulikov, Yu. N.; Hanslmeier, A.
Bibcode: 2012elbe.confE...3L
Altcode:
We discuss the evolution of the atmosphere of early Earth and of
terrestrial exoplanets which may be capable of sustaining liquid water
oceans and continents where life may originate. The formation age
of a terrestrial planet, its mass and size, as well as the lifetime
in the EUV-saturated early phase of its host star play a significant
role in its atmosphere evolution. We show that planets even in orbits
within the habitable zone of their host stars might not lose nebular-
or catastrophically outgassed initial protoatmospheres completely and
could end up as water worlds with CO2 and hydrogen- or oxygen-rich
upper atmospheres. If an atmosphere of a terrestrial planet evolves to
an N2-rich atmosphere too early in its lifetime, the atmosphere may
be lost. We show that the initial conditions set up by the formation
of a terrestrial planet and by the evolution of the host star's EUV
and plasma environment are very important factors owing to which a
planet may evolve to a habitable world as shown in Lammer et al. 2011.
Title: The Role of Stellar Plasma Interaction in the Evolution of
Earth-Like Habitats
Authors: Kislyakova, Kristina; Lammer, H.; Holmström, M.; Erkaev,
N. V.; Odert, P.; Gröller, H. 1; Khodachenko, M. L. 1; Kulikov,
Yu. N. 6; Hanslmeier, A. 2
Bibcode: 2012elbe.workE...2K
Altcode:
The detection of EUV heated extended and non-hydrostatic upper
atmospheres around Earth-like exoplanets would provide important
insights into the evolution of terrestrial planetary atmospheres and
their possible magnetic environments. Different scenarios where one can
expect that Earth-like planets should experience non-hydrostatic upper
atmosphere conditions so that dynamically outward flowing neutral atoms
can interact with the stellar plasma flow and huge hydrogen coronae can
be produced will be discussed. By observing the size of the extended
upper atmospheres and related hydrogen-clouds and by determining the
velocities of the surrounding hydrogen atoms, conclusions can be drawn
in respect to the origin of the main atmosphere species. We show that
the low size and mass of M-type stars makes them preferable targets to
observe extended hydrogen clouds around terrestrial exoplanets. Transit
follow-up observations in the UV-range of Earth-like exoplanets
around M-type stars with space observatories such as the World Space
Observatory-UV (WSO-UV) would provide a unique opportunity to shed
more light on the early evolution of habitable Earth-like planets,
including those of our own Solar System.
Title: Nebula-based Primordial Atmospheres of Planets Around
Solar-Like Stars Revised
Authors: Scherf, Manuel; Lammer, H.; Leitzinger, M.; Odert, P.;
Güdel, M.; Hanslmeier, A.
Bibcode: 2012elbe.workE..34S
Altcode:
At the beginning of a planetary system, in the stage of the stellar
nebula and the growing-phase of the planets, planetesimals and
Earth-like proto-planets accumulate a remarkable amount of gas, mainly
consisting of hydrogen and helium. The mass of such a primordial
atmosphere was first estimated for the proto-Earth by Hayashi et
al. (1979), with up to 1026 g accumulated within 106 years. Furthermore
it is commonly expected that these primordial atmospheres will be
completely dissipated due to irradiation of the stellar EUV-flux
during the first 108 years. Recent observations of young solar-like
stars indicate that the efficiency and effect of the EUV-flux after the
nebula disappeared, was highly overestimated by previous studies. We
show that parts of these dense hydrogen/helium-gas envelopes may
sustain this early active stage of a young star. Implications on the
habitability are also discussed.
Title: Pathways to Earth-Like Nitrogen Atmospheres: Implications
for the Search for Exo-Earth
Authors: Lammer, Helmut; Kislyakova, K. G.; Odert, P.; Leitzinger,
M.; Schwarz, R.; Pilat-Lohinger, E.; Güdel, M.; Khodachenko, M. L.;
Kulikov, Yu. N.; Hanslmeier, A.
Bibcode: 2012elbe.workE...1L
Altcode:
We discuss the evolution of the atmosphere of early Earth and of
terrestrial exoplanets which may be capable of sustaining liquid water
oceans and continents where life may originate. The formation age
of a terrestrial planet, its mass and size, as well as the lifetime
in the EUV-saturated early phase of its host star play a significant
role in its atmosphere evolution. We show that planets even in orbits
within the habitable zone of their host stars might not lose nebular-
or catastrophically outgassed initial protoatmospheres completely and
could end up as water worlds with CO2 and hydrogen- or oxygen-rich
upper atmospheres. If an atmosphere of a terrestrial planet evolves to
an N2-rich atmosphere too early in its lifetime, the atmosphere may
be lost. We show that the initial conditions set up by the formation
of a terrestrial planet and by the evolution of the host star's EUV
and plasma environment are very important factors owing to which a
planet may evolve to a habitable world.
Title: Exoplanet Upper Atmosphere Environment Characterization
Authors: Lammer, Helmut; Kislyakova, Kristina G.; Odert, Petra;
Leitzinger, Martin; Khodachenko, Maxim L.; Holmström, Mats;
Hanslmeier, Arnold
Bibcode: 2012IAUS..282..525L
Altcode:
The intense stellar SXR and EUV radiation exposure at ``Hot
Jupiters'' causes profound responses to their upper atmosphere
structures. Thermospheric temperatures can reach several thousands
of Kelvins, which result in dissociation of H2 to H and
ionization of H to H+. Depending on the density and orbit
location of the exoplanet, as a result of these high temperatures the
thermosphere expands dynamically up to the Roche lobe, so that geometric
blow-off with large mass loss rates and intense interaction with the
stellar wind plasma can occur. UV transit observations together with
advanced numerical models can be used to gain knowledge on stellar
plasma and the planet's magnetic properties, as well as the upper
atmosphere.
Title: Erratum to "Could CoRoT-7b and Kepler-10b be remnants of
evaporated gas or ice giants?". [Planetary and Space Science 59
(2011) 1472-1481]
Authors: Leitzinger, M.; Odert, P.; Kulikov, Yu. N.; Lammer, H.;
Wuchterl, G.; Penz, T.; Guarcello, M. G.; Micela, G.; Khodachenko,
M. L.; Weingrill, J.; Hanslmeier, A.; Biernat, H. K.; Schneider, J.
Bibcode: 2012P&SS...62..160L
Altcode:
The authors regret that a graphical error (wrong y-axis labeling)
in the lower right panel of Fig. 3 has occurred. The caption of
Fig. 3 had to be corrected too, according to the arrangement of the
panels. Furthermore the panels of Fig. 1 needed to be switched to
ensure that the description in the text and in the caption of Fig. 1
corresponds to the correct panel. The corrected Figs. 1 and 3 together
with their captions are shown below.
Title: Variability of solar/stellar activity and magnetic field and
its influence on planetary atmosphere evolution
Authors: Lammer, Helmut; Güdel, Manuel; Kulikov, Yuri; Ribas,
Ignasi; Zaqarashvili, Teimuraz V.; Khodachenko, Maxim L.; Kislyakova,
Kristina G.; Gröller, Hannes; Odert, Petra; Leitzinger, Martin;
Fichtinger, Bibiana; Krauss, Sandro; Hausleitner, Walter; Holmström,
Mats; Sanz-Forcada, Jorge; Lichtenegger, Herbert I. M.; Hanslmeier,
Arnold; Shematovich, Valery I.; Bisikalo, Dmitry; Rauer, Heike;
Fridlund, Malcolm
Bibcode: 2012EP&S...64..179L
Altcode:
It is shown that the evolution of planetary atmospheres can only be
understood if one recognizes the fact that the radiation and particle
environment of the Sun or a planet's host star were not always on the
same level as at present. New insights and the latest observations
and research regarding the evolution of the solar radiation,
plasma environment and solar/stellar magnetic field derived from the
observations of solar proxies with different ages will be given. We
show that the extreme radiation and plasma environments of the young
Sun/stars have important implications for the evolution of planetary
atmospheres and may be responsible for the fact that planets with low
gravity like early Mars most likely never build up a dense atmosphere
during the first few 100 Myr after their origin. Finally we present
an innovative new idea on how hydrogen clouds and energetic neutral
atom (ENA) observations around transiting Earth-like exoplanets by
space observatories such as the WSO-UV, can be used for validating
the addressed atmospheric evolution studies. Such observations would
enhance our understanding on the impact on the activity of the young
Sun on the early atmospheres of Venus, Earth, Mars and other Solar
System bodies as well as exoplanets.
Title: Automated image inversion using SIR compared to MERLIN Code
Authors: Thonhofer, S.; Utz, D.; Pauritsch, J.; Hanslmeier, A.;
Jurčak, J.; Lemmerer, B.; Kühner, O.
Bibcode: 2012CEAB...36...35T
Altcode:
The SIR code retrieves magnetic and thermodynamic parameters of the
solar atmosphere from the Stokes profiles. By means of this tool,
the stratification of physical quantities from spectropolarimetric
data is obtained and a complete model of the solar photosphere is
constructed. Automated SIR inversions of a HINODE data set were
performed and the output is compared to results of the MERLIN code,
another widespread inversion code in solar physics.
Title: Solar Hα and white light telescope at Hvar Observatory
Authors: Čalogović, J.; Dumbović, M.; Novak, N.; Vršnak, B.;
Brajša, R.; Pötzi, W.; Hirtenfellner-Polanec, W.; Veronig, A.;
Hanslmeier$, A.; Klvaňa, M.; Ambrož, P.
Bibcode: 2012CEAB...36...83C
Altcode:
Recently, the double solar telescope at Hvar Observatory was equipped
with the fourth generation of acquisition hardware and software. It
provides a valuable instrument to study rapid changes of chromospheric
and photospheric features in great detail. The telescope consists of
two Carl Zeiss refractors (photosphere d=217mm, chromosphere d=130mm)
mounted as one unit on a German parallax mounting. Using a field
of view of about 7 and 11 arcmin, it aims to produce high-resolution
high-cadence imaging of active regions on the Sun. New Pulnix TM-4200GE
12-bit CCD cameras allow to obtain time series with a cadence up to
30 images per minute.
Title: Life on Earth and other Planetary Bodies
Authors: Hanslmeier, Arnold; Kempe, Stephan; Seckbach, Joseph
Bibcode: 2012leop.book.....H
Altcode:
No abstract at ADS
Title: Centre to limb intensity variation of magnetic bright points
Authors: Utz, D.; Kühner, O.; Hanslmeier, A.; Veronig, A.; Muller,
R.; Lemmerer, B.; Pauritsch, J.; Thonhofer, S.
Bibcode: 2012CEAB...36...17U
Altcode:
The solar activity cycle is strongly related and rooted to photospheric
magnetic fields. Up to the present, it was mostly or even solely
studied by extended fields such as sunspots, sunspot groups or active
regions. Interestingly, the domain of magnetic fields on the Sun is
not only limited to extended and strong magnetic fields but reaches
down to small elements like single flux tubes. These flux elements
can be identified in G-band filtergrams as so called magnetic bright
points (MBPs). In this study we want to investigate the centre limb
variation of the mean MBP intensity for the period of the recent
solar minimum up to present (10/2008 - 10/2011). We found that a
4th order polynomial describes the centre limb variation fairly
well. Furthermore we established for the symmetrized and normalized
centre limb variation (for which the 1st and 3rd order parameter of
the polynomial is fixed to zero) a relationship between the 2nd and
4th order fit parameter. Hence it is possible to derive a description
with only one free parameter. Finally, we studied the variation with
time of this parameter for the period of October 2008 to present,
showing a slight increase and a weak correlation to solar activity as
given by the relative sunspot number.
Title: Habitability and Cosmic Catastrophes
Authors: Hanslmeier, Arnold
Bibcode: 2012leop.book..139H
Altcode:
No abstract at ADS
Title: Segmentation of Data from Simulations and Observations -
Evaluation and Outlook
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Kühner, O.;
Grimm-Strele, H.; Pauritsch, J.; Thonhofer, S.; Muthsam, H.
Bibcode: 2012CEAB...36...29L
Altcode:
3D simulation models based on Magneto-hydrodynamics (MHD) and Radiation
hydrodynamics (RHD) equations give an insight into the evolution
of magnetic field lines and convective motions. A 2D segmentation
algorithm was applied to data of the Japanese/US/European space
mission Hinode and its solar optical telescope (SOT) as well as on
3D models of the numerical simulation code ANTARES in order to study
the solar granulation and evaluate the algorithm. As a next research
step, the development of a 3D segmentation algorithm, adapted to the
simulation models, is required for the purpose of extracting magnetic
and convective phenomena, which furthermore enable an exact tracing
of their evolution.
Title: Pathways to Earth-Like Atmospheres. Extreme Ultraviolet
(EUV)-Powered Escape of Hydrogen-Rich Protoatmospheres
Authors: Lammer, Helmut; Kislyakova, K. G.; Odert, P.; Leitzinger,
M.; Schwarz, R.; Pilat-Lohinger, E.; Kulikov, Yu. N.; Khodachenko,
M. L.; Güdel, M.; Hanslmeier, A.
Bibcode: 2011OLEB...41..503L
Altcode: 2012OLEB..tmp....3L
We discuss the evolution of the atmosphere of early Earth and of
terrestrial exoplanets which may be capable of sustaining liquid water
oceans and continents where life may originate. The formation age
of a terrestrial planet, its mass and size, as well as the lifetime
in the EUV-saturated early phase of its host star play a significant
role in its atmosphere evolution. We show that planets even in orbits
within the habitable zone of their host stars might not lose nebular-
or catastrophically outgassed initial protoatmospheres completely
and could end up as water worlds with CO2 and hydrogen- or
oxygen-rich upper atmospheres. If an atmosphere of a terrestrial planet
evolves to an N2-rich atmosphere too early in its lifetime,
the atmosphere may be lost. We show that the initial conditions set up
by the formation of a terrestrial planet and by the evolution of the
host star's EUV and plasma environment are very important factors owing
to which a planet may evolve to a habitable world. Finally we present
a method for studying the discussed atmosphere evolution hypotheses
by future UV transit observations of terrestrial exoplanets.
Title: Non-Varying Granulation and Photospheric Network During the
Extended 2007 - 2009 Solar Minimum
Authors: Muller, R.; Utz, D.; Hanslmeier, A.
Bibcode: 2011SoPh..274...87M
Altcode:
We have analysed the wide band images taken by Hinode/SOT, in a blue
continuum window and in the G-band, more or less on a daily basis in
the frame of the synoptic program, to investigate the variation of the
solar granulation and of the photospheric network with the activity
cycle. A particular attention has been given to disentangle solar
effects from instrumental ones. It appears that a substantial fraction
of the images are more or less blurred and/or defocussed. During the
analysed period November 2006 - July 2010, the granulation contrast
of the sharpest selected images decreased steadily, the granulation
scale increased and the number of MBPs decreased (they are the Bright
Points of Magnetic origin which form the photospheric network in G-band
images). These trends are likely of instrumental origin. Consequently,
the granulation and the photospheric network have most probably not
changed during the extended solar minimum 2007 - 2009.
Title: Search for indications of stellar mass ejections using
FUV spectra
Authors: Leitzinger, M.; Odert, P.; Ribas, I.; Hanslmeier, A.; Lammer,
H.; Khodachenko, M. L.; Zaqarashvili, T. V.; Rucker, H. O.
Bibcode: 2011A&A...536A..62L
Altcode:
Aims: We search for highly energetic activity phenomena in a
small sample of late-type main-sequence stars in the far ultraviolet
(FUV) using data from the Far Ultraviolet Spectroscopic Explorer
(FUSE).
Methods: Because FUSE allows a simultaneous photometric
and spectroscopic analysis, we are able to analyze variations in the
light curves (flares) and possible, activity-related signatures (line
asymmetries, enhancements, and shifts) in the spectra. Furthermore, the
computation of the well-known density-sensitive line ratio C iii(λ1176
Å)/C iii(λ977 Å) is also possible, and allows the investigation of
its dependence on stellar activity.
Results: Three late-type
main-sequence stars found in the FUSE archive (HD 36705, HD 197481, and
Gl 388) show flares in their light curves. We find no obvious Doppler
shifts in the brightest lines of these stars, but the O vi(λ1032 Å)
transition region line of AD Leo shows a blue wing enhancement one
spectrum after a flare event. This emission feature is shifted by ~-84
km s-1 from the line core. We can exclude that the spectral
feature was caused by a gas cloud co-rotating with the star and favor
an interpretation of a mass ejection. In addition we find an increase
of the C iii(λ1176 Å)/C iii(λ977 Å) line ratio during all detected
flares. We compare this finding to the Sun using solar full-disk
spectra from the Thermosphere Ionosphere Mesosphere Energetics and
Dynamics (TIMED) and SOlar Radiation and Climate Experiment (SORCE)
missions, and find that powerful flare events also show an increased
C iii(λ1176 Å)/C iii(λ977 Å) line ratio but this result is of low
statistical significance. Owing to a lack of perfectly temporally
coinciding TIMED/SORCE spectra and a low temporal resolution (~15
spectra per day) it is not possible to distinguish clearly if this
increase is caused by the flares or by the related mass ejections.
Title: The LSO/KSO Hα prominence catalogue: cross-calibration of data
Authors: Rybák, J.; Gömöry, P.; Mačura, R.; Kučera, A.; Rušin,
V.; Pötzi, W.; Baumgartner, D.; Hanslmeier, A.; Veronig, A.;
Temmer, M.
Bibcode: 2011CoSka..41..133R
Altcode:
We present work on the extension of the homogeneous prominence
catalogue created for the epoch 1967 — 2009 at the Lomnicky Peak
Observatory (LSO) by incorporating new data acquired at the Kanzelhöhe
Observatory for Solar and Environmental Research (KSO). We use data of
20 Hα prominences observed almost simultaneously at both observatories
during four days in August/September 2009 to analyze the significance
of differences of the determined parameters used in the Hα prominence
catalogue. A reduction of the data from KSO and adaptation of the
resulting parameters to fit the parameters of the LSO catalogue confirm
that no special homogenization is needed to create a common catalogue
data set. Thus, we justified that the LSO catalogue could be extended
onward in the future using a more comprehensive database of observations
from KSO.
Title: Could CoRoT-7b and Kepler-10b be remnants of evaporated gas
or ice giants?
Authors: Leitzinger, M.; Odert, P.; Kulikov, Yu. N.; Lammer, H.;
Wuchterl, G.; Penz, T.; Guarcello, M. G.; Micela, G.; Khodachenko,
M. L.; Weingrill, J.; Hanslmeier, A.; Biernat, H. K.; Schneider, J.
Bibcode: 2011P&SS...59.1472L
Altcode:
We present thermal mass loss calculations over evolutionary time
scales for the investigation if the smallest transiting rocky
exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b
(∼1.416REarth) could be remnants of an initially more
massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We
apply a thermal mass loss formula which yields results that are
comparable to hydrodynamic loss models. Our approach considers the
effect of the Roche lobe, realistic heating efficiencies and a radius
scaling law derived from observations of hot Jupiters. We study the
influence of the mean planetary density on the thermal mass loss by
placing hypothetical exoplanets with the characteristics of Jupiter,
Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017
AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit
a K- or G-type host star. Our findings indicate that hydrogen-rich gas
giants within the mass domain of Saturn or Jupiter cannot thermally lose
such an amount of mass that CoRoT-7b and Kepler-10b would result in a
rocky residue. Moreover, our calculations show that the present time
mass of both rocky exoplanets can be neither a result of evaporation of
a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class
object. Depending on the initial density and mass, these planets most
likely were always rocky planets which could lose a thin hydrogen
envelope, but not cores of thermally evaporated initially much more
massive and larger objects.
Title: A relationship between the solar rotation and activity in the
period 1998-2006 analysed by tracing small bright coronal structures
in SOHO-EIT images
Authors: Jurdana-Šepić, R.; Brajša, R.; Wöhl, H.; Hanslmeier,
A.; Poljančić, I.; Svalgaard, L.; Gissot, S. F.
Bibcode: 2011A&A...534A..17J
Altcode:
Aims: The study aims to find a relationship between the rotation
of the small bright coronal structures (SBCS) described by the solar
rotation parameters and indices of solar activity on monthly and yearly
temporal scales.
Methods: We analyse precise measurements of
the solar differential rotation determined by tracing SBCS in SOHO-EIT
images and compare the derived solar rotation parameters with the
status of solar activity in the period 1998 - 2006. Full-disc solar
images obtained with the Extreme ultraviolet Imaging Telescope (EIT)
on board the Solar and Heliospheric Observatory (SOHO) were used to
analyse solar differential rotation determined by tracing SBCS. An
automatic method to identify and track the SBCS in EIT full-disc images
with a six hour cadence is applied. We performed a statistical analysis
of the monthly and yearly values of solar sidereal rotation velocity
parameters A and B (corresponding to the equatorial rotation velocity
and the gradient of the solar differential rotation, respectively)
as a function of various solar activity indices.
Results:
The dependence of the solar rotation on the phase of the solar cycle
was found. It is clearly visible for the solar rotation parameter A,
whilst the results are not conclusive for parameter B. The relationship
between the solar rotation and activity, expressed by the monthly
relative sunspot number, the smoothed monthly relative sunspot number,
the yearly relative sunspot number, and the interdiurnal variability
(IDV) index was investigated. The statistically significant correlation
was found for the solar rotation parameter A, whilst a very low and
insignificant correlation was obtained for the rotation parameter
B.
Conclusions: During the maximum of the solar cycle 23 and
just after it, the equatorial solar rotation velocity was lower than
in other phases of the cycle, when there was less activity. This is
consistent with other observational findings, obtained by different
tracers and methods.
Title: Are Active Stars Hiding Transiting Exoplanets?
Authors: Weingrill, J.; Hanslmeier, A.; Lammer, H.
Bibcode: 2011epsc.conf..481W
Altcode: 2011DPS....43..481W
We discuss the results from the observations of CoRoT, especially the
long runs like LRa01. These runs are an ideal test-bed for probing
photometry on the level of stellar activity by the means of rotation,
oscillation, stellar spots and flares. We discuss methods for analysing
and filtering periodic and aperiodic stellar variability down to the
level of mmag, where we expect the transit signals of an exo-Earth.
Title: Ion escape and energetic neutral atom production around EUV
exposed, expanded hydrogen-rich upper atmospheres of Earth-like
exoplanets
Authors: Kislyakova, K. G.; Lammer, H.; Holmström, M.; Khodachenko,
M. L.; Oder, P.; Leitzinger, M.; Kulikov, Y. N.; Hanslmeier, A.
Bibcode: 2011epsc.conf..130K
Altcode: 2011DPS....43..130K
Different scenarios of the early Earth-type hydrogenrich upper
atmospheres and their expected evolution are discussed. Due to the
higher EUV flux of the young Sun/stars exoplanets should experience
nonhydrostatic states which manifest in an expansion of the dynamically
outward flowing upper atmosphere. Outward flowing neutral atoms can
interact with the stellar plasma flow. We show that extended hydrogen
coronae and/or energetic neutral atoms (ENA) will be produced via
charge exchange processes with the stellar wind. Finally we estimate
the non-thermal ion loss rate and stellar wind erosion of the hydrogen
envelopes.
Title: Stellar activity and its influence on planetary atmosphere
evolution
Authors: Lammer, H.; Khodachenko, M. L.; Kislyakova, K. G.; Weingrill,
J.; Kulikov, Y. N.; Holmström, M.; Zaqarshvili, T. V.; Odert, P.;
Leitzinger, M.; Fichtinger, B.; Güdel, M.; Ribas, I.; Hanslmeier,
A.; Shematovich, V. I.; Bisikalo, D.
Bibcode: 2011epsc.conf..128L
Altcode: 2011DPS....43..128L
The evolution of planetary atmospheres can only be understood if one
recognizes the fact that the radiation and particle environment of
the Sun or a planet's host star were not always on the same activity
level. New insights, the latest observations and research regarding the
evolution of the solar radiation, plasma environment and solar/stellar
magnetic field from the observations of solar proxies and their impact
on planetary atmospheres with different ages will be given. We present
also a new innovative idea how hydrogen coronae and energetic neutral
atom (ENA) observations around transiting Earth-like exoplanets by
space observatories such as the WSO-UV, can be used for testing the
addressed atmospheric evolution studies.
Title: Multiversum Graz: A planetarium project
Authors: Stöckler, R.; Khodachenko, M.; Topf, F.; Reiss, M.; Sünkel,
H.; Hanslmeier, A.; Stumptner, W.; Holler, G.; Rath, G.
Bibcode: 2011epsc.conf..324S
Altcode: 2011DPS....43..324S
The core-team of the Multiversum Graz project is promoting the planning,
concept, creation and maintenance of a state-of-the-art planetarium
residing in Graz since the beginning of 2009. This contribution is
aimed at fostering synergies within the European planetaria community
and groups concerned with related projects such as building planetaria,
public outreach and communication, involving pupils and students in
scientific projects and making science more popular in general. This
presentation emphasizes the concepts of a modern technology planetarium
and the environmental, educational and cultural benefits to its region.
Title: UV transit observations of EUV-heated expanded thermospheres
of Earth-like exoplanets around M-stars: testing atmosphere evolution
scenarios
Authors: Lammer, H.; Eybl, V.; Kislyakova, K. G.; Weingrill, J.;
Holmström, M.; Khodachenko, M. L.; Kulikov, Yu. N.; Reiners, A.;
Leitzinger, M.; Odert, P.; Xiang Grüß, M.; Dorner, B.; Güdel, M.;
Hanslmeier, A.
Bibcode: 2011Ap&SS.335...39L
Altcode: 2011Ap&SS.tmp..278L; 2011Ap&SS.tmp..398L
The detection and investigation of EUV heated, extended and
non-hydrostatic upper atmospheres around terrestrial exoplanets would
provide important insights into the interaction of the host stars
plasma environment as well as the evolution of Earth-type planets
their atmospheres and possible magnetic environments. We discuss
different scenarios where one can expect that Earth-like planets
should experience non-hydrostatic upper atmosphere conditions so that
dynamically outward flowing neutral atoms can interact with the stellar
plasma flow so that huge hydrogen coronae and energetic neutral atoms
(ENA) can be produced via charge exchange. By observing the size of the
extended upper atmospheres and related ENA-clouds and by determining the
velocities of the surrounding hydrogen atoms, conclusions can be drawn
in respect to the origin of these features. Due to the large number
of M-type stars in our neighbourhood and their long periods of strong
and moderate stellar activity in comparison to G-stars, we expect that
M-type stars represent the most promising candidates for the detection
of hydrogen ENA-clouds and the subsequent study of the interaction
between the host star and the planets' upper atmosphere. We show that
the low mass of M-type stars also makes them preferable targets to
observe extended hydrogen clouds around terrestrial exoplanets with
a mass as low as one Earth mass. Transit follow-up observations in
the UV-range of terrestrial exoplanets around M-type stars with space
observatories such as the World Space Observatory-UV (WSO-UV) would
provide a unique opportunity to shed more light on the early evolution
of Earth-like planets, including those of our own Solar System.
Title: Water in the Universe
Authors: Hanslmeier, Arnold
Bibcode: 2011ASSL..368.....H
Altcode:
Due to its specific chemical and physical properties, water is essential
for life on Earth. And it is assumed that this would be the case for
extraterrestrial life as well. Therefore it is important to investigate
where water can be found in the Universe. Although there are places that
are completely dry, places where the last rainfall happened probably
several 100 million years ago, surprisingly this substance is quite
omnipresent. In the outer solar system the large satellites of Jupiter
and Saturn are covered by a thick layer of ice that could be hiding a
liquid ocean below. This of course brings up the question of whether
the recently detected extrasolar planets could have some water on their
surfaces and how we can detect this. Water molecules are also found in
interstellar gas and dust clouds. This book begins with an introductory
chapter reviewing the physical and chemical properties of water. Then
it illuminates the apparent connection between water and life. This
is followed by chapters dealing with our current knowledge of water
in the solar system, followed by a discussion concerning the potential
presence and possible detection of water on exoplanets. The signature
of water in interstellar space and stars are reviewed before the origin
of water in the Universe is finally discussed. The book ends with an
appendix on detection methods, satellite missions and astrophysical
concepts touched upon in the main parts of the book. The search for
water in the Universe is related to the search for extraterrestrial
life and is of fundamental importance for astrophysics, astrobiology
and other related topics. This book therefore addresses students and
researchers in these fields.
Title: Implementation of a Calcium telescope at Kanzelhöhe
Observatory (KSO)
Authors: Hirtenfellner-Polanec, W.; Temmer, M.; Pötzi, W.; Freislich,
H.; Veronig, A. M.; Hanslmeier, A.
Bibcode: 2011CEAB...35..205H
Altcode:
A new telescope is implemented at Kanzelhöhe Observatory in order to
observe the chromosphere in the Ca II K line at 393.4 nm (FWHM 0.3
nm). The design of the new Ca camera system is very similar to the
well established Kanzelhöhe Photosphere Digital Camera and the Hα
system and allows obtaining automatically full disc Ca~II~K 2k×2k
images time series with a cadence of a few seconds. The main purpose
of this new instrument is a high precision full disc imaging of the
chromosphere in order to observe flares, plages and the chromospheric
network. The Ca emission is also an indicator for magnetic activity
on the sun. Therefore the Ca data will be taken for analysing the
variations in the structures of the magnetic field.
Title: Exoplanet Magnetic Field Estimation via Energetic Neutral Atoms
(ENAs) and Hydrogen Cloud Observations and Modelling
Authors: Lammer, H.; Kislyakova, K. G.; Holmström, M.; Khodachenko,
M. L.; Grießmeier, J. -M.; Wurz, P.; Selsis, F.; Hanslmeier, A.
Bibcode: 2011pre7.conf..303L
Altcode:
The discovery of more than 500 exoplanets during the past 15 years
has enabled us to characterize the upper atmosphere structure of some
exosolar gas giants and to compare observational and modelling results
to the known planets in the Solar System. It is of great interest to
understand if these exosolar "Hot Jupiters" share similar physical
processes compared to the giant planets (Jupiter and Saturn)
in the Solar System with regard to their magnetic dynamos and
the corresponding expected magnetic field strengths. In this work
we discuss how observations of stellar Lyman-alpha absorption by
so-called Energetic Neutral Atoms (ENAs) around transiting exoplanets
together with theoretical modelling efforts can be used as a tool
for estimating magnetic obstacle sizes and the corresponding magnetic
field strength. For demonstrating this method we model the production
of stellar wind related planetary hydrogen and ENA populations around
the exosolar gas giant HD 209458b and show how a detailed analysis
of attenuation spectra obtained during transits can be used for the
estimation of the planet's magnetic obstacle size and hence its dynamo
field strength. Our study indicates that the magnetic field strength
of HD 209458b which is able to balance the stellar wind plasma flow by
a magnetic obstacle around the planet which can explain the observed
Lyman-alpha line profiles observed before and during the transits by
HST corresponds to a magnetic dipole moment which is about 40 percent
of Jupiters value.
Title: Differences in heliographic positions and rotation velocities
of sunspot groups from various observatories
Authors: Poljančić, I.; Brajša, R.; Hržina, D.; Wöhl, H.;
Hanslmeier, A.; Pötzi, W.; Baranyi, T.; Özgüç, A.; Singh, J.;
Ruždjak, V.
Bibcode: 2011CEAB...35...59P
Altcode:
Measured positions of sunspot groups that differ in format, precision
and observing procedure are collected from various data sets:
GPR (Greenwich Photoheliographic Results), SOON/USAF/NOAA (Solar
Optical Observing Network/United States Air Force/National Oceanic and
Atmospheric Administration), as well as from the Kodaikanal and Debrecen
observatories. Kanzelh&{uml;o}he and Kandilli Observatory currently
provide the digitized sunspot drawings, from which the positions
of selected sunspot groups are determined with a special software
Sungrabber. The rotation velocities are calculated from the position
data. The aim of this work is to compare and to check the precision
of the mentioned data sets using the Kanzelh&{uml;o}he Observatory
data set as the reference basis of sunspot position measurements. The
selected groups (about 40% consist of single sunspots Z&{uml;u}rich
types H and J) are from the years 1972 and 1993 belonging to similar
declining phases of two solar activity cycles. The occurrence of some
systematic differences of the sunspot group positions and rotation
velocities suggests the need for a more detailed analysis of the data
accumulation procedures.
Title: Multiwavelength Investigations of Magnetic Bright Points
Authors: Kühner, O.; Utz, D.; Hanslmeier, A.; Veronig, A.; Roudier,
T.; Muller, R.; Muthsam, H.
Bibcode: 2011CEAB...35...29K
Altcode:
In this contribution we present our results regarding the study
of small scale magnetic fields as seen by magnetic bright points
(MBPs) in different wavelengths and hence different heights. By the
determination of the size distribution of these features we are able
to derive the value of the scale height parameter for the photosphere:
107 km ± 18.5 km. For the Fe I line at 630.25 nm we derived a formation
height of 225 km.
Title: Magnetic energy estimation for small scale magnetic fields
Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Kühner, O.; Muller,
R.; Muthsam, H.
Bibcode: 2011CEAB...35...19U
Altcode:
In this paper we derive an estimate of the energy content of small scale
magnetic fields as observed by magnetic bright points (MBPs). For
our estimations we use as inputs the size, lifetime, magnetic field
strength of MBPs and the average number density of those features in the
quiet Sun. Furthermore we introduce an evolutionary model for MBPs. Our
results suggest that there is enough magnetic field energy stored in kG
fields as seen by MBPs to heat the chromosphere and corona. The actual
heating mechanism and process has to be investigated in the future.
Title: Dynamika fotosférických jasných bodov v G-páse odvodená
použitím dvoch plne automatických algoritmov Title: Dynamika
fotosférických jasných bodov v G-páse odvodená použitím dvoch
plne automatických algoritmov Title: Dynamics of photospheric bright
points in G-band derived from two fully automated algorithms.
Authors: Bodnárová, M.; Rybák, J.; Hanslmeier, A.; Utz, D.
Bibcode: 2010nspm.conf...25B
Altcode:
Concentrations of small-scale magnetic field in the solar photosphere
can be identified in the G-band of the solar spectrum as bright
points. Studying the dynamics of the bright points in the G-band
(BPGBs) can also help in addressing many issues related to the
problem of the solar corona heating. In this work, we have used
a set of 142 specled images in the G-band taken by the Dutch Open
Telescope (DOT) on 19 October 2005 to make a comparison of two fully
automated algorithms identifying BPGBs: an algorithm developed by Utz
et al. (2009, 2010), and an algorithm developed following the work
of Berger et al. (1995, 1998). We then followed in time and space
motion of the BPGBs identified by both algorithms and constructed the
distributions of their lifetimes, sizes and speeds. The results show
that both algorithms give very similar results for the BPGB lifetimes
and speeds, but their results vary significantly for the sizes of the
identified BPGBs. This difference is due to the fact that in the case of
the Berger et al. identification algorithm no additional criteria were
applied to constrain the allowed BPGB sizes. As a result in further
studies of the BPGB dynamics we will prefer to use the Utz algorithm
to identify and track BPGBs.
Title: Detection of Transiting Super-Earths around Active Stars
Authors: Weingrill, J.; Lammer, H.; Khodachenko, M. L.; Hanslmeier, A.
Bibcode: 2010ASPC..430..556W
Altcode:
We studied the influence of stellar activity by G-, K- and M-type stars
on the detection of transiting planets in the size range of Neptunes
down to super-Earths. The main goal is to improve transit detection
algorithms by analyzing the stellar activity like stellar spots or
flares. We analyzed measurements of space-based missions like CoRoT as
well as ground-based observations of solar-like stars with extrasolar
planet candidates. We realized that ground based observations have
limited capability to detect short-term stellar variations due to
atmospheric effects. Otherwise space-based observations tend to
measure higher activity of solar like stars than usual. We present
some filtering methods to increase the signal to noise ratio for the
detection of Neptune- to super-Earth-class planets.
Title: Stellar Activity Characteristics at FUV and Radio Wavelengths
Authors: Leitzinger, M.; Odert, P.; Hanslmeier, A.; Ribas, I.;
Konovalenko, A. A.; Vanko, M.; Khodachenko, M. L.; Lammer, H.; Rucker,
H. O.
Bibcode: 2010ASPC..430..483L
Altcode:
Since stellar activity can affect atmospheres of close-in habitable
exoplanets, knowledge of a star’s activity level is crucial. Different
wavelength ranges yield different possibilities on investigating
stellar activity phenomena such as flares and coronal mass ejections
(CMEs). In this context we present two approaches to this topic using
observations from the far-ultraviolet (FUV) and radio domains. The
FUV provides density sensitive line ratios, which show enhancements
during stellar flaring. The question if these could be correlated to
mass expulsions is investigated by analyzing time series of solar UV
full-disk measurements using data from the SORCE and TIMED missions. The
second approach is dedicated to the decameter wavelength domain, where
we use the known correlation between radio decameter type II bursts and
CMEs on the Sun. We present the detection of promising events on the
active M-dwarf AD Leo which have a high probability of being of stellar
origin. These bursts have parameters similar to solar decameter type
III bursts which are fast drifting bursts usually correlated with flares
on the Sun. Both approaches are discussed and results are presented.
Title: M-Type Stars as Hosts for Habitable Planets
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. L.; Ribas, I.
Bibcode: 2010ASPC..430..515O
Altcode:
Several planets orbiting M dwarfs have been discovered during the last
years. However, it is still a matter of debate if these numerous,
low-mass stars could be suitable hosts for habitable planets. Many
M stars exhibit high levels of activity (high XUV fluxes, powerful
flares etc.) during extended periods of time that could be harmful to
the evolution of life. To address this topic we are compiling a catalog
of nearby M dwarfs that could be suitable targets for habitable planet
searches. It will include all data necessary to characterize the stars
and to derive their fundamental properties. Special attention is turned
towards data related to their activity (e.g., X-ray/EUV emission,
and associated data like rotation periods). These data allow us to
estimate important stellar characteristics (e.g., ages, flare rates,
mass-loss rates) that could have a major impact on planets inside the
habitable zone. Here we summarize the current status of this work.
Title: Spectral line enhancements as signatures for stellar activity:
AD Leonis - an example
Authors: Leitzinger, M.; Odert, P.; Hanslmeier, A.; Ribas, I.;
Konovalenko, A. A.; Vanko, M.; Lammer, H.; Khodachenko, M. L.; Rucker,
H. O.
Bibcode: 2010IJAsB...9..235L
Altcode:
A high level of stellar activity in the form of frequent flaring and
frequent mass ejections can lead to the total loss of exoplanetary
atmospheres due to evaporation and erosion. Simulations have shown
such scenarii for close-in exoplanets orbiting M-stars. Information on
stellar flaring activity is accessible more easily than information on
stellar mass ejections, simply due to the difference in detection. In
the National Aeronautics and Space Administration/Far Ultraviolet
Spectroscopic Explorer spectra of the dM star AD Leonis we find an
interesting event lasting for only one spectrum. The first component
of the OVI (103.19 nm, 103.76 nm) duplet shows an enhancement of the
blue wing, shifted by about 90 km s-1. This event occurred
one spectrum after a flare. We discuss several solar/stellar phenomena
that might produce such a spectral feature and could therefore explain
this event.
Title: Implications of stellar activity for exoplanetary atmospheres
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. L.; Ribas, I.
Bibcode: 2010IJAsB...9..239O
Altcode:
Stellar X-ray and extreme ultraviolet (XUV) radiation is an important
driver of the escape of planetary atmospheres. Young stars emit high
XUV fluxes that decrease as they age. Since the XUV emission of a young
star can be orders of magnitude higher compared to an older one, this
evolution has to be taken into account when studying the mass-loss
history of a planet. The temporal decrease of activity is closely
related to the operating magnetic dynamo, which depends on rotation
and convection in Sun-like stars. Using a sample of nearby M dwarfs,
we study the relations between age, rotation and activity and discuss
the influence on planets orbiting these low-mass stars.
Title: Thermal mass-loss of exoplanets in close orbits
Authors: Odert, P.; Leitzinger, M.; Lammer, H.; Kulikov, Yu. N.;
Khodachenko, M. L.; Hanslmeier, A.
Bibcode: 2010epsc.conf..582O
Altcode:
No abstract at ADS
Title: Planetarium GRAZ: Project Phases and Experiences
Authors: Stöckler, R.; Khodachenko, M.; Topf, F.; Reiss, M.; Sünkel,
H.; Hanslmeier, A.; Stumptner, W.; Holler, G.; Rath, G.
Bibcode: 2010epsc.conf..109S
Altcode:
No abstract at ADS
Title: Planetarium GRAZ - Star Theatre and Science Multimedia Centre
for Public Education and Entertainment
Authors: Khodachenko, M.; Topf, F.; Stöckler, R.; Reiss, M.; Sünkel,
H.; Hanslmeier, A.; Stumptner, W.; Holler, G.; Rath, G.
Bibcode: 2010epsc.conf...86K
Altcode:
No abstract at ADS
Title: A precise measurement of the solar differential rotation by
tracing small bright coronal structures in SOHO-EIT images. Results
and comparisons for the period 1998-2006
Authors: Wöhl, H.; Brajša, R.; Hanslmeier, A.; Gissot, S. F.
Bibcode: 2010A&A...520A..29W
Altcode:
Aims: We precisely determine the solar rotation velocity during
most of the 23rd solar cycle, in the years 1998-2006. We measure the
solar differential rotation by tracing small bright coronal structures
(SBCS) in SOHO-EIT images.
Methods: The 28.4 nm EIT channel was
used and positions of more than 55 000 structures were measured applying
an interactive and improved automatic method of data reduction.
Results: We achieve the closest representation of the observational
data when all three solar differential rotation parameters are used
and obtain the formula ω (b) = 14.499 (±0.006) - 2.54 (±0.06)
sin2 b - 0.77 (±0.09) sin4b. This result
represents the sidereal rotation velocity in deg day-1
and is produced by the automatic method applied in 1998-2006. A
north-south rotational asymmetry and a rigid component of the solar
rotation at high latitudes were found.
Conclusions: A more
differential rotation profile of SBCS than of sunspots and sunspot
groups was found. The rotation velocity of SBCS is very similar
to those obtained by small photospheric magnetic features. The
north-south rotational asymmetry of SBCS was interpreted with a model
of the relationship between solar rotation and activity. The rigid
component of the solar rotation at high latitudes, identifiable only
from the results of the automatic method, was related to larger
structures mostly identified by that method, in contrast to the
interactive method, which detected smaller structures. Tables
3-11 and Figs. 4, 5 are only available in electronic form at http://www.aanda.org
Title: Exoplanet status report: Observation, characterization and
evolution of exoplanets and their host stars
Authors: Lammer, H.; Hanslmeier, A.; Schneider, J.; Stateva, I. K.;
Barthelemy, M.; Belu, A.; Bisikalo, D.; Bonavita, M.; Eybl, V.; Coudé
du Foresto, V.; Fridlund, M.; Dvorak, R.; Eggl, S.; Grießmeier,
J. -M.; Güdel, M.; Günther, E.; Hausleitner, W.; Holmström,
M.; Kallio, E.; Khodachenko, M. L.; Konovalenko, A. A.; Krauss, S.;
Ksanfomality, L. V.; Kulikov, Yu. N.; Kyslyakova, K.; Leitzinger, M.;
Liseau, R.; Lohinger, E.; Odert, P.; Palle, E.; Reiners, A.; Ribas, I.;
Rucker, H. O.; Sarda, N.; Seckbach, J.; Shematovich, V. I.; Sozzetti,
A.; Tavrov, A.; Xiang-Grüß, M.
Bibcode: 2010SoSyR..44..290L
Altcode:
After the discovery of more than 400 planets beyond our Solar System,
the characterization of exoplanets as well as their host stars can
be considered as one of the fastest growing fields in space science
during the past decade. The characterization of exoplanets can only be
carried out in a well coordinated interdisciplinary way which connects
planetary science, solar/stellar physics and astrophysics. We present
a status report on the characterization of exoplanets and their host
stars by reviewing the relevant space- and ground-based projects. One
finds that the previous strategy changed from space mission concepts
which were designed to search, find and characterize Earth-like rocky
exoplanets to: A statistical study of planetary objects in order to get
information about their abundance, an identification of potential target
and finally its analysis. Spectral analysis of exoplanets is mandatory,
particularly to identify bio-signatures on Earth-like planets. Direct
characterization of exoplanets should be done by spectroscopy, both
in the visible and in the infrared spectral range. The way leading to
the direct detection and characterization of exoplanets is then paved
by several questions, either concerning the pre-required science or
the associated observational strategy.
Title: Dynamics of isolated magnetic bright points derived from
Hinode/SOT G-band observations
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Rybák,
J.; Muthsam, H.
Bibcode: 2010A&A...511A..39U
Altcode: 2009arXiv0912.1965U
Context. Small-scale magnetic fields in the solar photosphere can
be identified in high-resolution magnetograms or in the G-band as
magnetic bright points (MBPs). Rapid motions of these fields can
cause magneto-hydrodynamical waves and can also lead to nanoflares by
magnetic field braiding and twisting. The MBP velocity distribution is
a crucial parameter for estimating the amplitudes of those waves and
the amount of energy they can contribute to coronal heating.
Aims: The velocity and lifetime distributions of MBPs are derived from
solar G-band images of a quiet sun region acquired by the Hinode/SOT
instrument with different temporal and spatial sampling rates.
Methods: We developed an automatic segmentation, identification
and tracking algorithm to analyse G-Band image sequences to obtain
the lifetime and velocity distributions of MBPs. The influence of
temporal/spatial sampling rates on these distributions is studied and
used to correct the obtained lifetimes and velocity distributions for
these digitalisation effects.
Results: After the correction of
algorithm effects, we obtained a mean MBP lifetime of (2.50 ± 0.05)
min and mean MBP velocities, depending on smoothing processes, in
the range of (1-2) km~s-1. Corrected for temporal sampling
effects, we obtained for the effective velocity distribution a Rayleigh
function with a coefficient of (1.62 ± 0.05) km~s-1. The
x- and y-components of the velocity distributions are Gaussians. The
lifetime distribution can be fitted by an exponential function.
Title: Stellar Aspects of Habitability - Characterizing Target Stars
for Terrestrial Planet-Finding Missions
Authors: Kaltenegger, Lisa; Eiroa, Carlos; Ribas, Ignasi; Paresce,
Francesco; Leitzinger, Martin; Odert, Petra; Hanslmeier, Arnold;
Fridlund, Malcolm; Lammer, Helmut; Beichman, Charles; Danchi, William;
Henning, Thomas; Herbst, Tom; Léger, Alain; Liseau, René; Lunine,
Jonathan; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub;
Selsis, Frank; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna;
White, Glenn J.
Bibcode: 2010AsBio..10..103K
Altcode: 2009arXiv0906.0378K
We present and discuss the criteria for selecting potential target
stars suitable for the search for Earth-like planets, with a special
emphasis on the stellar aspects of habitability. Missions that search
for terrestrial exoplanets will explore the presence and habitability
of Earth-like exoplanets around several hundred nearby stars, mainly
F, G, K, and M stars. The evaluation of the list of potential target
systems is essential in order to develop mission concepts for a search
for terrestrial exoplanets. Using the Darwin All Sky Star Catalogue
(DASSC), we discuss the selection criteria, configuration-dependent
subcatalogues, and the implication of stellar activity for habitability.
Title: The chaotic solar cycle. I. Analysis of cosmogenic
14C-data
Authors: Hanslmeier, A.; Brajša, R.
Bibcode: 2010A&A...509A...5H
Altcode:
Context. The study of solar activity over long time intervals using
proxies.
Aims: The periodicity of the solar activity cycle
is studied. The solar activity cycle is governed by a complex dynamo
mechanism. Methods of nonlinear dynamics enable us to learn more about
the regular and chaotic behavior of solar activity.
Methods:
By applying methods of nonlinear dynamics, the solar activity cycle is
studied by using solar activity proxies that have been reaching into the
past for over 10 000 years. The complexity of the system is expressed by
several parameters of nonlinear dynamics, such as embedding dimension or
false nearest neighbors, and the method of delay coordinates is applied
to the time series.
Results: The solar activity cycle is found
to be on the edge of chaotic behavior. This can explain the observed
intermittent period of longer lasting solar activity minima. Filtering
the data by eliminating variations below a certain period (the periods
380 yr and 57 yr were used) yields a far more regular behavior of
solar activity.
Conclusions: The solar time series of solar
activity proxies used here clearly shows that solar activity behaves
differently from random data. The unfiltered data exhibit a complex
dynamics requiring an embedding dimension >15. The variations become
more regular when filtering the data. The results also indicate that
solar activity proxies are influenced by other than solar variations
and reflect solar activity only on longer time scales.
Title: Stellar activity at FUV/Radio wavelengths
Authors: Leitzinger, M.; Odert, P.; Hanslmeier, A.; Ribas, I.;
Konovalenko, A. A.; Vanko, M.; Lammer, H.; Khodachenko, M. L.; Rucker,
H. O.
Bibcode: 2010CEAB...34..123L
Altcode:
Since stellar activity affects atmospheres of close-in habitable
exoplanets, knowledge of a star's activity level is crucial. Different
wavelength ranges yield different possibilities on investigating stellar
activity phenomena such as flares and CMEs. We present two approaches to
this topic using observations from the FUV and Radio domains. The FUV
provides density sensitive line ratios, which show enhancements during
stellar flaring. The second approach is dedicated to the decameter
wavelength domain, where we use the known correlation between radio
decameter type II bursts and CMEs on the Sun. We present promising
events on the active M-dwarf AD Leo which show a high probability
of being of stellar origin concerning the applied criteria for
discriminating between stellar and artificial emission. The detected
bursts have parameters similar to solar decameter type III bursts. We
present and discuss results of both approaches.
Title: The Sun and Space Weather
Authors: Hanslmeier, Arnold
Bibcode: 2010ASSP...18..233H
Altcode: 2010hepr.book..233H
In this chapter we will briefly review the basic interactions between
particles and magnetic fields, the processes that occur on the Sun which
are relevant for space weather as well as their influences on Earth
and the space environment of Earth. The strong societal impact of space
weather to our complex world of telecommunication will be stressed.
Title: M-type stars as hosts for habitable planets: ages of nearby
M dwarfs
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. L.; Ribas, I.
Bibcode: 2010CEAB...34..129O
Altcode:
During the last years, several exoplanets orbiting M dwarfs have
been discovered. However, it is still debated whether these stars
could be suitable hosts for habitable planets. The main concern is
their long-enduring high level of activity, which includes high XUV
fluxes, powerful flares and possibly also strong winds and coronal
mass ejections, to which the planets are exposed. In order to gain
more knowledge on M star activity, its evolution with time and impact
on nearby planets, we compiled a catalogue of nearby M dwarfs. It
includes basic properties and activity-related data that allow us to
study these diverse objects in more detail. Here, we use data from
this catalogue to derive ages for a part of our sample.
Title: Investigating the Variation of the Solar Granulation with
HINODE Synoptic images
Authors: Muller, R.; Hanslmeier, A.; Utz, D.
Bibcode: 2010CEAB...34...89M
Altcode:
We have analysed the wide band images taken by HINODE/SOT on a daily
basis in the frame of the synoptic program, to investigate the variation
of the solar granulation with the activity cycle. A particular attention
has been given to disentangle solar from instrumental effects. It
appears that a substantial fraction of the images are more or less
blurred and/or defocused. The granulation contrast decrease and scale
increase of the sharpest images, observed during the period November
2006 - January 2009, is probably not of solar origin.
Title: Multiwavelength alignment of Hinode/SOT Data
Authors: Kuehner, O.; Utz, D.; Hanslmeier, A.; Veronig, A.; Roudier,
T.; Muller, R.; Muthsam, H.
Bibcode: 2010CEAB...34...31K
Altcode:
First results regarding the spatial alignment of observations taken at
different wavelengths are presented. An exceptionally long time series
(48 hours) of data, obtained by the Solar Optical Telescope (SOT)
of the Hinode satellite, has been analysed. Hinode delivers (among
other data) high resolution seeing free filtergrams in the magnetic
sensitive G-band, blue continuum, chromospheric Ca II H line and Fe I
line. For the study of the position and dynamics of small scale fields
(MBPs; Magnetic Bright Points) at different wavelengths (at different
heights in the photosphere and chromosphere) the alignment of these
data at pixel and subpixel level will be essential. Results concerning
the height dependence of MBPs will also be of vital importance for
questions regarding the coronal heating.
Title: G-band to Blue-Continuum Excess as quasi total field strength
magnetogram
Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Rybák, J.; Muller,
R.; Muthsam, H.
Bibcode: 2010CEAB...34...13U
Altcode:
The dynamics of the solar plasma is driven by strong localized magnetic
fields. It is well known that activity like flares and CMEs are related
to the dissipation and reconnection of these magnetic fields. These
energetic releases influence and make up the so called space weather. It
is therefore of vital importance to get a deeper understanding of the
magnetic fields of the Sun. To get this insights, it is crucial to
obtain information on the magnetic fields with spatial and temporal
resolutions as high as possible. In this paper we outline an easy to
apply method to obtain quasi total magnetic field strength magnetograms
out of two simple filtergrams (blue continuum and G-band). We will
present our simple approach and the first results of this method and
give finally an outlook what has to be done in the future.
Title: Solar activity proxies - geomagnetic variations
Authors: Hanslmeier, A.; Brajša, R.
Bibcode: 2010CEAB...34..109H
Altcode:
Solar activity proxies are needed for studies of the long term
behaviour of the solar activity cycles. Cosmogenic isotopes like
^{14}C are influenced also by geomagnetic field variations. We study
the influence of such variations on the global behaviour of solar
activity measured by methods of non linear dynamics.
Title: Hinode - Synoptic observations of convection dynamics
Authors: Hanslmeier, A.; Muller, R.; Utz, D.; Roudier, T.
Bibcode: 2010CEAB...34...81H
Altcode:
The variation of solar convection over the solar activity cycle is
still discussed with controversial results. In this paper we study
the solar granulation and its variation over the unusual long lasting
solar minimum between cycle 23 and 24. Spatially highly resolved Hinode
images were segmented and the mean value of the segmented granules as
well as their number was found to be practically constant.
Title: Magnetic field strength distribution of MBPs infered from
Hinode/SOT filtergram and spectro-polarimetric data
Authors: Utz, Dominik; Veronig, Astrid; Hanslmeier, Arnold; Muller,
Richard; Muthsam, Herbert
Bibcode: 2010cosp...38.2944U
Altcode: 2010cosp.meet.2944U
Small scale magnetic fields can be observed on the Sun in G-band
filtergrams as magnetic bright points (MBPs), or by inversions
of spectro-polarimetric data. In this study we used three
different data sets of Hinode/SOT observations which were recorded
simultaneously with the broadband filter device (G-band, Ca II-H) and
the spectro-polarimeter. The spectro-polarimetric data were already
prepared as magnetograms (level 2 data). For the identification of the
MBPs we used an automated identification algorithm. The three data sets
comprise active regions (a sunspot group and a small sunspot in the
other case) as well as quiet Sun. The obtained magnetic field strength
distribution of MBPs is in all three cases similar and shows a peaked
maximum at 1250 G, which agrees well with theoretical predictions of
the convectice collapse model.
Title: Brightness profiles and size distributions of MBPs observed
in different heights by HINODE/SOT data
Authors: Kühner, Otmar; Veronig, Astrid; Utz, Dominik; Hanslmeier,
Arnold; Muthsam, Herbert; Muller, Richard; Roudier, Thierry
Bibcode: 2010cosp...38.2948K
Altcode: 2010cosp.meet.2948K
We study the characteristics of Magnetic Bright Points (MBPs)
observed at different wave-lenghts and hence different heights of
the photosphere and chromosphere. The data sets were obtained with
the Solar Optical Telescope (SOT) of the Hinode satellite. Hinode
delivers (among other data) high resolution seeing free filtergrams in
the blue continuum, the Fe I line, the magnetic sensitive G-band and
the chromospheric Ca II H line. Due to the small scale structure of
MBPs it was essential for our study to develop an algorithm for the
image co-alignment at subpixel level for the images taken at these
four wavelenghts. We studied an exceptionally long time series (48h)
and analyzed the brightness profiles and size distributions of MBPs
at different heights. The mean size of the features increases with
increasing height and shows an exponential behavior. We obtained the
scale height parameter of the photosphere to be 110 km.
Title: Geophysical and Atmospheric Evolution of Habitable Planets
Authors: Lammer, Helmut; Selsis, Frank; Chassefière, Eric; Breuer,
Doris; Grießmeier, Jean-Mathias; Kulikov, Yuri N.; Erkaev, Nikolai
V.; Khodachenko, Maxim L.; Biernat, Helfried K.; Leblanc, Francois;
Kallio, Esa; Lundin, Richard; Westall, Frances; Bauer, Siegfried J.;
Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm;
Gröller, Hannes; Hanslmeier, Arnold; Hausleitner, Walter; Henning,
Thomas; Herbst, Tom; Kaltenegger, Lisa; Léger, Alain; Leitzinger,
Martin; Lichtenegger, Herbert I. M.; Liseau, René; Lunine, Jonathan;
Motschmann, Uwe; Odert, Petra; Paresce, Francesco; Parnell, John;
Penny, Alan; Quirrenbach, Andreas; Rauer, Heike; Röttgering, Huub;
Schneider, Jean; Spohn, Tilman; Stadelmann, Anja; Stangl, Günter;
Stam, Daphne; Tinetti, Giovanna; White, Glenn J.
Bibcode: 2010AsBio..10...45L
Altcode:
The evolution of Earth-like habitable planets is a complex process that
depends on the geodynamical and geophysical environments. In particular,
it is necessary that plate tectonics remain active over billions of
years. These geophysically active environments are strongly coupled to
a planet's host star parameters, such as mass, luminosity and activity,
orbit location of the habitable zone, and the planet's initial water
inventory. Depending on the host star's radiation and particle flux
evolution, the composition in the thermosphere, and the availability
of an active magnetic dynamo, the atmospheres of Earth-like planets
within their habitable zones are differently affected due to thermal
and nonthermal escape processes. For some planets, strong atmospheric
escape could even effect the stability of the atmosphere.
Title: Dynamics of G-band bright points derived using two fully
automated algorithms
Authors: Bodnárová, M.; Utz, D.; Rybák, J.; Hanslmeier, A.
Bibcode: 2010CEAB...34...25B
Altcode:
Small-scale magnetic field concentrations (∼ 1 kG) in the solar
photosphere can be identified in the G-band of the solar spectrum
as bright points. Study of the G-band bright points (GBPs) dynamics
can help us in solving several questions related also to the coronal
heating problem. Here a set of 142 G-band speckled images obtained
using the Dutch Open Telescope (DOT) on October 19, 2005 are used to
compare identification of the GBPs by two different fully automated
identification algorithms: an algorithm developed by Utz et al. (2009a,
2009b) and an algorithm developed according to papers of Berger et
al. (1995, 1998). Temporal and spatial tracking of the GBPs identified
by both algorithms was performed resulting in distributions of
lifetimes, sizes and velocities of the GBPs. The obtained results show
that both algorithms give very similar values in the case of lifetime
and velocity estimation of the GBPs, but they differ significantly
in case of estimation of the GBPs sizes. This difference is caused
by the fact that we have applied no additional exclusive criteria on
the GBPs identified by the algorithm based on the work of Berger et
al. (1995, 1998). Therefore we conclude that in a future study of the
GBPs dynamics we will prefer to use the Utz's algorithm to perform
identification and tracking of the GBPs in G-band images.
Title: Correlation of photospheric quantities in the ANTARES model
Authors: Lemmerer, B.; Hanslmeier, A.; Muthsam, H.; Leitner, P.
Bibcode: 2010CEAB...34...39L
Altcode:
In order to analyse in-depth stellar thermodynamic quantities
which otherwise would require much more complex and time consuming
observations and measurements numeric models have been developed. The
present work is based on data retrieved from the ANTARES model,
a 3D radiation hydrodynamics Fortran90-code modelling solar surface
convection. The main focus in this paper lies on the determination
of the structure of the photosphere. Results have been obtained
by calculating and comparing correlation height-functions. These
calculations were performed with a model data set with an extended time
domain compared to former research carried out by Leitner (2009). As a
verification, results were compared to the former mentioned correlations
and observational findings. The correlations showed no significant
deviation from data sets with extended time domain and support the
mentioned observational results.
Title: Determining the mass loss limit for close-in exoplanets:
what can we learn from transit observations?
Authors: Lammer, H.; Odert, P.; Leitzinger, M.; Khodachenko, M. L.;
Panchenko, M.; Kulikov, Yu. N.; Zhang, T. L.; Lichtenegger, H. I. M.;
Erkaev, N. V.; Wuchterl, G.; Micela, G.; Penz, T.; Biernat, H. K.;
Weingrill, J.; Steller, M.; Ottacher, H.; Hasiba, J.; Hanslmeier, A.
Bibcode: 2009A&A...506..399L
Altcode:
Aims: We study the possible atmospheric mass loss from 57 known
transiting exoplanets around F, G, K, and M-type stars over evolutionary
timescales. For stellar wind induced mass loss studies, we estimate the
position of the pressure balance boundary between Coronal Mass Ejection
(CME) and stellar wind ram pressures and the planetary ionosphere
pressure for non- or weakly magnetized gas giants at close orbits.
Methods: The thermal mass loss of atomic hydrogen is calculated by
a mass loss equation where we consider a realistic heating efficiency,
a radius-scaling law and a mass loss enhancement factor due to stellar
tidal forces. The model takes into account the temporal evolution of
the stellar EUV flux by applying power laws for F, G, K, and M-type
stars. The planetary ionopause obstacle, which is an important factor
for ion pick-up escape from non- or weakly magnetized gas giants
is estimated by applying empirical power-laws.
Results: By
assuming a realistic heating efficiency of about 10-25% we found that
WASP-12b may have lost about 6-12% of its mass during its lifetime. A
few transiting low density gas giants at similar orbital location,
like WASP-13b, WASP-15b, CoRoT-1b or CoRoT-5b may have lost up to 1-4%
of their initial mass. All other transiting exoplanets in our sample
experience negligible thermal loss (≤1%) during their lifetime. We
found that the ionospheric pressure can balance the impinging dense
stellar wind and average CME plasma flows at distances which are above
the visual radius of “Hot Jupiters”, resulting in mass losses <2%
over evolutionary timescales. The ram pressure of fast CMEs cannot
be balanced by the ionospheric plasma pressure for orbital distances
between 0.02-0.1 AU. Therefore, collisions of fast CMEs with hot gas
giants should result in large atmospheric losses which may influence
the mass evolution of gas giants with masses <M_Jup. Depending on the
stellar luminosity spectral type, planetary density, heating efficiency,
orbital distance, and the related Roche lobe effect, we expect that at
distances between 0.015-0.02 AU, Jupiter-class and sub-Jupiter-class
exoplanets can lose several percent of their initial mass. At orbital
distances ≤0.015 AU, low density hot gas giants in orbits around
solar type stars may even evaporate down to their coresize, while low
density Neptune-class objects can lose their hydrogen envelopes at
orbital distances ≤0.02 AU.
Title: Atmospheric Loss of Sub-Neptune's and Implications for Liquid
Phases of Different Solvents on Their Surfaces
Authors: Leitner, J. J.; Lammer, H.; Odert, P.; Leitzinger, M.;
Firneis, M. G.; Hanslmeier, A.
Bibcode: 2009epsc.conf..542L
Altcode:
No abstract at ADS
Title: The size distribution of magnetic bright points derived from
Hinode/SOT observations
Authors: Utz, D.; Hanslmeier, A.; Möstl, C.; Muller, R.; Veronig,
A.; Muthsam, H.
Bibcode: 2009A&A...498..289U
Altcode: 2009arXiv0912.2637U
Context: Magnetic bright points (MBPs) are small-scale magnetic features
in the solar photosphere. They may be a possible source of coronal
heating by rapid footpoint motions that cause magnetohydrodynamical
waves. The number and size distribution are of vital importance in
estimating the small scale-magnetic-field energy.
Aims: The
size distribution of MBPs is derived for G-band images acquired by the
Hinode/SOT instrument.
Methods: For identification purposes, a new
automated segmentation and identification algorithm was developed.
Results: For a sampling of 0.108 arcsec/pixel, we derived a mean
diameter of (218 ± 48) km for the MBPs. For the full resolved data set
with a sampling of 0.054 arcsec/pixel, the size distribution shifted
to a mean diameter of (166 ± 31) km. The determined diameters are
consistent with earlier published values. The shift is most probably
due to the different spatial sampling.
Conclusions: We conclude
that the smallest magnetic elements in the solar photosphere cannot
yet be resolved by G-band observations. The influence of discretisation
effects (sampling) has also not yet been investigated sufficiently.
Title: On solar cycle predictions and reconstructions
Authors: Brajša, R.; Wöhl, H.; Hanslmeier, A.; Verbanac, G.;
Ruždjak, D.; Cliver, E.; Svalgaard, L.; Roth, M.
Bibcode: 2009A&A...496..855B
Altcode:
Context: Generally, there are two procedures for solar cycle
predictions: the empirical methods - statistical methods based on
extrapolations and precursor methods - and methods based on dynamo
models.
Aims: The goal of the present analysis is to forecast
the strength and epochs of the next solar cycle, to investigate proxies
for grand solar minima and to reconstruct the relative sunspot number
in the Maunder minimum.
Methods: We calculate the asymmetry of
the ascending and descending solar cycle phases (Method 1) and use this
parameter as a proxy for solar activity on longer time scales. Further,
we correlate the relative sunspot numbers in the epochs of solar
activity minima and maxima (Method 2) and estimate the parameters of
an autoregressive moving average model (ARMA, Method 3). Finally,
the power spectrum of data obtained with the Method 1 is analysed
and the Methods 1 and 3 are combined.
Results: Signatures of
the Maunder, Dalton and Gleissberg minima were found with Method 1. A
period of about 70 years, somewhat shorter than the Gleissberg period
was identified in the asymmetry data. The maximal smoothed monthly
sunspot number during the Maunder minimum was reconstructed and found
to be in the range 0-35 (Method 1). The estimated Wolf number (also
called the relative sunspot number) of the next solar maximum is in
the range 88-102 (Method 2). Method 3 predicts the next solar maximum
between 2011 and 2012 and the next solar minimum for 2017. Also, it
forecasts the relative sunspot number in the next maximum to be 90
± 27. A combination of the Methods 1 and 3 gives for the next solar
maximum relative sunspot numbers between 78 and 99.
Conclusions:
The asymmetry parameter provided by Method 1 is a good proxy for solar
activity in the past, also in the periods for which no relative sunspot
numbers are available. Our prediction for the next solar cycle No. 24
is that it will be weaker than the last cycle, No. 23. This prediction
is based on various independent methods.
Title: A catalogue of nearby M stars
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. L.; Ribas, I.; Vanko, M.; Konovalenko, A. A.; Rucker,
H. O.
Bibcode: 2009AIPC.1094..947O
Altcode: 2009csss...15..947O
The discovery of several planets around M dwarfs during the last
years has renewed the interest in the possible habitability of
these stars. Extreme stellar activity, such as observed on many of
the younger M stars, could be harmful to the evolution of life. To
address this topic we are working on the compilation of a catalogue of
nearby M stars, which will include basic stellar properties as well
as activity-related data. The current status and preliminary results
of this work are presented.
Title: Decametric observations of active M-dwarfs
Authors: Leitzinger, M.; Odert, P.; Hanslmeier, A.; Konovalenko,
A. A.; Vanko, M.; Khodachenko, M. L.; Lammer, H.; Rucker, H. O.
Bibcode: 2009AIPC.1094..680L
Altcode: 2009csss...15..680L
We present first-time observations of M dwarfs AD Leonis and EV
Lacertae in the decametric range using digital multichannel devices
as back-end facilities on World's largest decameter array, the UTR-2
near Kharkov of the Ukrainian Academy of Sciences. Our aim is to find
radio signatures of high activity phenomena, such as flares and CMEs. As
known from the sun these phenomena cause particle beams and shock waves,
which show up as bursts in dynamic radio spectra. Both stars are known
to be young and active, and both show, besides others, structures in
their spectra which are similar to solar decameter type II and III
bursts. Several criteria are applied to discriminate between stellar
and artificial emission, showing that some of the detected structures
have a high probability of being of stellar origin. Averaging of the
spectra in time and frequency is also applied to make possible bursts
visible. Both radio campaigns were accompanied by coordinated optical
photometry for a possible correlation of optical flares and decameter
radio bursts.
Title: Structure Analysis of a Model Solar Photosphere
Authors: Leitner, P.; Hanslmeier, A.; Muthsam, H. J.; Veronig, A.;
Löw-Baselli, B.; Obertscheider, C.
Bibcode: 2009CEAB...33...69L
Altcode:
The structure of the solar photosphere has been studied by means of
correlation analysis. The data analysis is based on a 3D radiation
hydrodynamics-code modelling solar surface convection with high
resolution in both, space and time. The variation of thermodynamic
quantities with depth have been evaluated as well as the dependencies
among those quantities as a function of depth. This gives an insight
into the structure of the convective-radiative transition layer. We
determined height levels for regions of thermal convection, convective
overshoot, and for the near-surface layer up from where radiation
takes over the role of the outward energy transport.
Title: Triangulation of CME Source Region Locations on the Sun and
Dependence on Spacecraft Observation Angles
Authors: Preiss, S.; Temmer, M.; Hanslmeier, A.
Bibcode: 2009CEAB...33..125P
Altcode:
STEREO-A, STEREO-B, and LASCO/SOHO observe coronal mass ejections
(CMEs) from three different vantage points. On the basis of the radial
plane-of-sky (POS) measurements of a CME in these three projection
planes, the CME source region (SR) location was determined using the
triangulation method of Temmeretal2009. As this triangulation method
needs distance-time measurements in one POS as reference input, the
determined SR varies with the change of the reference system. In the
present study we vary the reference system, which shows the dependence
of the resulting SR location of a CME on the spacecraft observation
angles, and also reveals the limitation of the radial POS measurements.
Title: A Prediction for the 24th Solar Cycle
Authors: Brajša, R.; Wöhl, H.; Hanslmeier, A.; Verbanac, G.;
Ruždjak, D.; Cliver, E.; Svalgaard, L.; Roth, M.
Bibcode: 2009CEAB...33...95B
Altcode:
The aim of the present analysis is to forecast the strength of the
next solar maximum of the 24th cycle. We correlate the
relative sunspot numbers in the epochs of solar activity minima and
maxima. Using this method, the estimated relative sunspot number (also
called the Wolf number) of the next solar maximum is in the range 67-81,
i.e., about 40 % below the peak sunspot number of 121 for cycle No. 23.
Title: Habitability and Cosmic Catastrophes
Authors: Hanslmeier, Arnold
Bibcode: 2009hcc..book.....H
Altcode:
No abstract at ADS
Title: Discretization Effects on the Size Distribution of Magnetic
Bright Points
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Muthsam,
H.; Möstl, C.
Bibcode: 2009CEAB...33...29U
Altcode:
We developed an automated identification algorithm for magnetic bright
points to derive the size distribution of MBPs in a quiet region near
solar disc centre. For this purpose two different data sets from the
Hinode/SOT mission were used. The first data set had a pixel spatial
sampling of 0.108 arcsec/pixel, whereas the second data set had the full
achievable spatial sampling of 0.54 arcsec/pixel. We found, that the
size distribution shifted from a mean value of 218 km in diameter to
a smaller value of about 166 km in diameter when the spatial sampling
was higher. Therefore, we suggest that discretization effects play a
crucial role for the study of small scale features. How the shift of
the two distributions could be explained, and how a deeper insight
into the discretization problem could be gained, is discussed.
Title: Solar Convection Dynamics Derived from Long Time Series
Observations
Authors: Hanslmeier, A.; Roudier, Th.; Rieutord, M.; Muller, R.
Bibcode: 2009CEAB...33...39H
Altcode:
Long time series of solar granulation are extremely difficult to
be obtained from ground based observations because of the unstable
Earth's atmosphere. The Hinode-SOT instrument provided long term
stable time series of solar granulation at different wavelengths in
the visible. After appropriate calibration, these data can be used
for studies of long time series of several hours. In this study we
concentrate on the question of whether granulation can be considered
as an ergodic phenomenon. The answer to such question is very important
when comparing observational results with theoretical models since these
models are limited either in time or in the extension of the spatial
grid. We have analysed a series of 8 h of Hinode-SOT blue continuum
images, the average separation between the successive images was at
maximum about 50 sec. The images were aligned in order to minimize
tracking problems. A quiet region located near the solar disc centre at
the beginning of the observations was selected. The analysis shows that
it seems to be that solar granulation is at least near the behaviour
of ergodicity. That means, that the behaviour along the time axis and
along a spatial coordinate become similar on a long interval. From
sufficient spatial sampling the time behaviour could be derived.
Title: Solar Convection and Oscillation Interaction
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.;
Gömöry, P.
Bibcode: 2009CEAB...33...51H
Altcode:
In this paper we investigate bisectors of solar photospheric lines. The
bisectors reflect vertical velocity gradients over the height of line
formation and therefore reveal important information about the dynamics
in these layers. Their shape and shift is influenced by (a) convective
motions, (b) oscillatory motions that can act differently at different
photospheric heights. The bisectors are selected from different
locations that show mainly a granular evolution or an intergranular
evolution. Two selection criteria were applied: continuum intensity
(enhanced for granular bisectors, reduced for intergranular bisectors),
and full width at half maximum values (enhanced for intergranular
bisectors). The results demonstrate how oscillatory motions influence
the bisectors as a whole. In the example given a smaller amplitude of
oscillations over intergranular areas is indicated.
Title: Observational Evidence for Shocks in the Solar Photosphere -
New TESOS/VTT Results
Authors: Rybak, J.; Kucera, A.; Hanslmeier, A.; Woehl, H.;
Wedemeyer-Boehm, S.; Steiner, O.
Bibcode: 2008ESPM...12.2.36R
Altcode:
High-resolution spectroscopic observations recently acquired with the
TESOS spectrometer at the Vacuum Tower Telescope (VTT, Observatorio
del Teide, Tenerife) are used to test predictions regarding strongly
dynamic events in the photosphere as obtained from three-dimensional
numerical simulations with the CO5BOLD-code. Time series of
two-dimensional maps of the Fe I 543.4 nm spectral line profile at
different centre-to-limb positions are investigated in a statistical
sense by comparing the distributions of individual spectral parameters
derived from observations with the corresponding distributions
from synthesized spectra calculated with the LINFOR3D code from
the simulations. Appropriate degradation of the synthesized spectra
was applied in order to take the limited spatial resolution of the
telescope, seeing effects, and the scattered instrumental light into
account. At the actual spatial resolution of 0.5 arc sec, the
statistics show that signatures of the photospheric dynamics, including
the most dynamical events like occasional supersonic flows of plasma in
the nearly horizontal direction, are very similar in both observations
and simulations. Discrepancies are found only for those spectral
parameters (residual line intensity, Doppler line core shifts), which
are affected by non-LTE effects, since non-LTE effects are not taken
into account in the synthesis of the Fe I 543.4nm spectral line.
Title: On the Solar Rotation and Activity in the Years 1998 - 2003
Authors: Brajsa, R.; Woehl, H.; Hanslmeier, A.; Gissot, S. F.
Bibcode: 2008ESPM...122.114B
Altcode:
Full-disc full-resolution solar images obtained by the Extreme
Ultraviolet Imaging Telescope on board the Solar and Heliospheric
Observatory are used to analyse solar differential rotation by tracing
coronal bright points. We applied an interactive and an improved
automatic method of data reduction to process data obtained during
the period 1998 - 2003 with the Fe XV filter (28.4 nm). Using the
interactive method, the data obtained during 8 months of observation
were reduced, while the automatic method was applied to analyse the
whole 57-month period of observations, since the interactive method is
much more time consuming than the automatic one. In the present work we
especially focus on a possible relationship between the solar rotation
(57 monthly values of the solar rotation parameters determined with
the automatic method) and activity (relative sunspot numbers for the
same months) during the maximum phase of the solar cycle 23.
Title: The Size Distribution of Magnetic Bright Points derived from
Hinode/SOT Observations
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Astrid, V.; Muthsam,
H.; Möstl, Ch.
Bibcode: 2008ESPM...12.2.50U
Altcode:
In our poster we will present our results regarding the size
distribution of Magnetic Bright Points (MBPs) in the solar
photosphere. The data sets were obtained through the Solar Optical
Telescope (SOT) of the recent Hinode satellite. Hinode was launched
in autumn 2006 and delivers (among other data) high resolution seeing
free filtergrams in the magnetic sensitive G-Band. We analyzed two
different data sets (with different pixel resolutions) near disk
center in a network region of the quiet sun. The interesting outcome
is that the derived size distribution depends on the used pixel
resolution. Discretisation effects and physical implications on the
derived size distributions will be discussed.
Title: Observation of Turbulence in Solar Surface Convection:
I. Line Parameter Correlations
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2008SoPh..249..293H
Altcode: 2008SoPh..tmp...88H
By using slit observations of solar photospheric lines shifted by 0.4
arcsec, a 2D field on the Sun was scanned to obtain a 16-minute time
series of 2D line-parameter variations. The aim was to investigate in
detail the occurrence of turbulence that can be measured by line-width
variations extracted from the line profiles. The continuum-intensity
variation served as a proxy for granular (bright) and intergranular
(dark) areas. The results show that turbulence is not limited to
the intergranular space but is also produced by horizontal motions
that may become supersonic, leading to turbulence. These motions
lead to brightenings, as predicted by theoretical models. Thus,
enhanced line-width variations are found to occur in both bright and
dark areas. A Sobel filter served to detect the areas where strong
gradients in the line parameters occur. By applying this filter to the
different line-parameter variations over the 2D field observed, we can
determine whether there exists a similarity of these strong-gradient
patterns with other parameters that characterize granular motions such
as intensity variations or velocity fluctuations.
Title: Analysis of a Moreton Wave Associated with the X17.2/4B
Flare/CME of 28-10-2003
Authors: Muhr, M.; Temmer, M.; Veronig, A.; Vršnak, B.; Hanslmeier, A.
Bibcode: 2008CEAB...32...79M
Altcode:
The fast Moreton wave of 28-Oct-2003 associated with the extreme X17.2
solar flare/CME event is studied. It can be followed in four sectors,
spanning almost over 360° on the visible solar disc. The mean wave
velocity lies in the range of v∼900-1000 km s^{-1}. We find two
wave ignition centres on opposite edges of the source region, which
may indicate that the wave is driven by the CME expanding flanks.
Title: Proper Motions of Coronal Bright Points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.; Verbanac, G.; Skokić, I.; Hanslmeier, A.
Bibcode: 2008CEAB...32..165B
Altcode:
Full-field full-resolution solar images obtained by the Extreme
Ultraviolet Imaging Telescope on board the Solar and Heliospheric
Observatory are used to analyse proper motions, velocity distributions,
lifetimes, and diffusion coefficient of coronal bright points. The
results obtained by the interactive method for three tracer subtypes
(point-like structures, small loops, and small active regions)
of coronal bright points for the period 4 June 1998 to 22 May 1999
are presented and compared. Distributions of meridional velocities,
residual azimuthal velocities and velocities of proper motions are
presented for the three tracer subtypes. Lifetimes up to 54 hours
are found for 98% of all observed coronal bright points. Small active
regions last on the average longer than point-like structures and small
loops. The correlation between the absolute velocity of proper motion
and lifetime is investigated and the mean free path (in the range from
3000 km to 15000 km) and the diffusion coefficient (approximately 200
km2/s) of coronal bright points are estimated. Finally,
characteristics of the random walk process associated to the motions
of coronal bright points are discussed in the Appendix.
Title: Kanzelhöhe Photosphere Telescope (KPT)
Authors: Otruba, W.; Freislich, H.; Hanslmeier, A.
Bibcode: 2008CEAB...32....1O
Altcode:
The Kanzelhöhe Photoheliograph (PhoKa) was in operation since 1989
to obtain full disc photoheliograms in continuum (on film) for the
derivation of sunspot positions with high precision. Recently the
instrument was reconstructed completely to adapt for the application
of a high resolution CCD cam as the image acquisition device instead
of film plates. The design of the new Kanzelhöhe Photosphere Digital
Camera (KPDC) is very similar to the established Kanzelhöhe Hα
high cadence imaging system and allows to obtain automatically full
disc continuum images time series with 2kx2k spatial and down to a
few seconds temporal resolution. The evaluation of the geometric and
photometric precision is presently in progress.
Title: Habitability of M-type Stars - a Catalogue of Nearby M Dwarfs
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. I.; Ribas, I.; Vanko, M.; Konovalenko, A. A.; Rucker,
H. O.
Bibcode: 2008CEAB...32..149O
Altcode:
Since the discovery of a Super-Earth in the habitable zone of a nearby
M star the question if M stars are suitable hosts for habitable worlds
is more interesting than ever. In earlier times these objects have
often been ruled out in this context because of the extreme activity
levels which they exhibit during the first few billion years of their
life on the main-sequence. Future missions dedicated to the search for
extrasolar planets will probably discover more Earth-like planets in
the vicinity of these cool stars, therefore a profound knowledge of
the radiation and particle environment of these stars and the impact
on planetary atmospheres is desirable. To address this topic we are
working on the compilation of a catalogue of nearby M stars. This
database will include all relevant data to categorize these diverse
objects and will therefore be a useful tool for the generation of
target lists for observations as well as for deriving input parameters
for theoretical models.
Title: Defects in Some RISE/PSPT Full Disk Solar Images from Mauna
Loa Solar Observatory
Authors: Vogler, F.; Brandt, P.; Otruba, W.; Pötzi, W.; Hanslmeier, A.
Bibcode: 2008CEAB...32..141V
Altcode:
RISE/PSPT 2k x 2k full disk solar images in Ca IIK, blue and red
continua from MAUNA LOA Solar Observatory, from the period May 28 until
July 31, 1999, are used to analyse the contrast of solar faculae and
of sunspots and pores for modelling solar irradiance variations. The
data exist in two versions: in a 1999 processed version and in a
2005 reprocessed version. By changing over from the first to the
reprocessed version, a set of more than 15 dark specks, ranging
from 77 to a few pixels in area and from -0.74 to -0.05 in contrast,
were detected in all images. These specks are located at exactly the
same solar coordinates in the images taken in one wavelength band,
but exhibit slight changes in the solar coordinates between the 3
wavelength bands. For all images of the 2005 reprocessed version the
locations of the specks are identified as originating from fixed CCD
pixel coordinates. The specks lead to strong erroneous signals in the
analysis of pore-like solar structures. They may be caused by wrong
flat-fielding in the 2005 reprocessing procedure.
Title: Coronal Bright Points as Tracers for Solar Rotation in
October-November 1999
Authors: Brajša, R.; Mulec, M.; Hanslmeier, A.; Wöhl, H.; Ruždjak,
V.; Hochedez, J. -F.
Bibcode: 2008CEAB...32..117B
Altcode:
Whole-disc full-resolution solar images taken in the extreme ultraviolet
part of the spectrum (Fe XV line at 28.4 nm) with the EIT instrument
on board the SOHO spacecraft were used to visually identify coronal
bright points appropriate for solar rotation determination. From the
time differences in successive tracer positions amounting to six hours
the solar rotation velocity was determined tracing coronal bright
points in images obtained in October and November 1999. The resulting
parameters and profiles of the solar rotation are presented.
Title: HINODE SOT Observations - First Preliminary Analysis
Authors: Hanslmeier, A.; Müller, R.; Roudier, Th.; Rieutord, M.
Bibcode: 2008CEAB...32...25H
Altcode:
In this paper we present some preliminary analysis of Hinode-SOT
data: time series as well as synoptic data. We show that the data
are influenced by periodic intensity variations as well as bad images
appear. This should be taken into account when analysing the data.
Title: RHESSI Microflares: I. X-Ray Properties and Multiwavelength
Characteristics
Authors: Stoiser, S.; Veronig, A. M.; Aurass, H.; Hanslmeier, A.
Bibcode: 2007SoPh..246..339S
Altcode:
We study the general X-ray and multiwavelength characteristics
of microflares of GOES class A0.7 to B7.4 (background subtracted)
detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI) on 26 September 2003 comparing them with the properties of
regular flares. All the events for which X-ray imaging was feasible
originated in one active region and were accumulated in areas with
intermixed magnetic polarities. During the events' rise and peak phase,
the RHESSI X-ray spectra show a steep nonthermal power-law component
(4≲γ≲10) for energies ≳ 10 keV. Further evidence for the
presence of electron beams is provided by the association with radio
type III bursts in 5 out of 11 events where AIP radio spectra were
available. The strongest event in our sample shows radio signatures
of a type II precursor. The thermally emitting flare plasma observed
by RHESSI is found to be hot, 11≲T≲15 MK, with small emission
measures, 1046≲EM≲1047 cm−3,
concentrated in the flare loop. In the EUV (TRACE 171 Å), the UV (TRACE
1600 Å) and Kanzelhöhe Solar Observatory Hα, impulsive brightenings
at both ends of the RHESSI 3 - 6 keV X-ray loop source are observed,
situated in opposite magnetic polarity fields. During the decay phase,
a postflare loop at the location of the RHESSI loop source is observed
in the TRACE 171 Å channel showing plasma that is cooled from ≳ 10
MK to ≈ 1 MK. Correlations between various thermal and nonthermal
parameters derived from the RHESSI microflare spectra compared to
the same correlations obtained for a set of small and large flares by
Battaglia et al. (Astron. Astrophys.439, 737, 2005) indicate that the
RHESSI instrument gives us a spectrally biased view since it detects
only hot (T≳10 MK) microflares, and thus the correlations between
RHESSI microflare parameters have to be interpreted with caution. The
thermal and nonthermal energies derived for the RHESSI microflares
are \bar{E}_{th}=7× 10^{27} ergs and \bar{E}_{nth}=2× 10^{29} ergs,
respectively. Possible reasons for the order-of-magnitude difference
between the thermal and nonthermal microflare energies, which was also
found in previous studies, are discussed. The determined event rate
of 3.7 h−1 together with the average microflare energies
indicate that the total energy in the observed RHESSI microflares is
far too small to account for the heating of the active region corona
in which they occur.
Title: Variations of the granulation related to the solar cycle and
with respect to its position on the solar disk
Authors: Muller, R.; Hanslmeier, A.; Saldaña-Muñoz, M.
Bibcode: 2007A&A...475..717M
Altcode:
Aims:We investigate variations in the scale and contrast of the
solar granulation related to the solar cycle during the period
1978-1993. Furthermore, as a by-product, we have detected a variation
with respect to the solar longitude, along the solar equator.
Methods: All images were taken on film with the 50 cm refractor of
the Pic du Midi Observatory, under excellent seeing conditions. Scale
and contrast were derived from power spectra computed with digitized
images. This simple and robust statistical method allowed us to get
reliable results, independent of any image-processing parameter.
Results: The contrast of the solar granulation varies nearly in phase
with the solar cycle, being smaller at the periods of solar maximum. But
we detected no corresponding variation in the scale; if there is one,
it must be of low amplitude and masked by a spatial variation in the
scale with respect to the position on the solar equator, which amounts
to 3% rms. The contrast also varies with the position on the equator,
in phase with the scale: where the scale is larger, the contrast is
higher too. The amplitude of this spatial variation in the granulation
scale is 9%; large photometric uncertainties did not allow us to
quantify the amplitude of the contrast variation.
Title: Activity of M-type stars and its influence on planetary
habitability
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M.; Ribas, I.; Vanko, M.; Konovalenko, A. A.; Rucker,
H. O.
Bibcode: 2007epsc.conf..759O
Altcode:
Since the discovery of a Super-Earth in the habitable zone of a nearby
M star the question if M stars are suitable hosts for habitable worlds
is more interesting than ever. In earlier times these objects have
often been ruled out in this context because of the extreme activity
levels which they exhibit during the first few billion years of their
life on the main-sequence. Future missions dedicated to the search of
extrasolar planets will probably discover more Earth-like planets in
the vicinity of these cool stars, therefore a profound knowledge of
the radiation and particle environment of these stars and the impact
on planetary atmospheres is desirable. To address this topic we are
working on the compilation of a catalogue of nearby M stars including
all relevant data to categorize these diverse objects. This catalogue
will be a useful tool for generating target lists for observations as
well as deriving input parameters for theoretical models.
Title: Radio decameter observations of AD Leonis
Authors: Leitzinger, M.; Odert, P.; Hanslmeier, A.; Konovalenko,
A. A.; Vanko, M.; Khodachenko, M.; Lammer, H.; Rucker, H. O.
Bibcode: 2007epsc.conf..693L
Altcode:
AD Leonis is known to be an active flaring star of spectral type M4.5
Ve. The world's largest decamter array, the UTR-2 near Kharkov/Ukraine
of the Ukrainian Academy of Scienecs, was monitoring this star for ten
nights during February of this year. A Digital Spectro Polarimeter (DSP)
was used as back-end facility giving the possibility of investigating
dynamic spectra. These spectra are very useful when searching for
decameter radio type II bursts, which show a slow frequency drift
with time and are known to be correlated with Coronal Mass Ejections
(CMEs) on the sun. Since the drift in frequency is correlated with
the density of the material through which the shock wave propagates,
we can use this also as a proxy for e.g. density changes for
stellar wind investigations. We are able to discriminate between
stellar and artificial emission using the instrument's multibeam
capability. Also averaging techniques are applied to make possible
bursts detectable. The main intention is the search for stellar
analogues of the solar type II bursts as signatures of CMEs, but also
for periodic structures. Preliminary results are presented.
Title: Mass-loss of M-type stars - impact on planetary atmospheres
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. L.; Ribas, I.; Vanko, M.; Konovalenko, A. A.; Rucker,
H. O.
Bibcode: 2007epsc.conf..772O
Altcode:
Stars lose fractions of their mass via steady winds and discrete
ejections. Stellar massloss is thought to have important consequences
for the atmospheres of nearby planets. If exposed to dense particle
streams during long timescales, planets might even lose their whole
atmospheres, especially if their magnetic field protection is weak
due to tidal locking. For our Sun, these mass outflows can be probed
directly, and a variety of methods exists to study dense stellar
winds. However, mass-loss rates of stars in the order of the solar
value are too tenuous to produce any detectable emission. Several
attempts have been made to estimate the mass-loss rates of late-type
stars, but the results show large scatter and depend strongly on the
model assumptions needed for the particular technique used. Since it
is assumed that active M∼dwarfs which exhibit powerful flares and
XUV emission should also have enhanced mass-loss rates, observational
evidence for this assumption is needed to optimize theoretical models
addressing the habitability of planets around M dwarfs.
Title: The Sun and Space Weather
Authors: Hanslmeier, Arnold
Bibcode: 2007ASSL..347.....H
Altcode:
This second edition is a great enhancement of literature which
will help the reader get deeper into the specific topics. There
are new sections included such as space weather data sources and
examples, new satellite missions, and the latest results. At the end
a comprehensive index is given which will allow the reader to quickly
find his topics of interest. The Sun and Space weather are two
rapidly evolving topics. The importance of the Sun for the Earth,
life on Earth, climate and weather processes was recognized long
ago by the ancients. Now, for the first time there is a continuous
surveillance of solar activity at nearly all wavelengths. These data
can be used to improve our understanding of the complex Sun-Earth
interaction. The first chapters of the book deal with the Sun
as a star and its activity phenomena as well as its activity cycle in
order to understand the complex physics of the Sun-Earth system. The
reader will see that there are many phenomena but still no definite
explanations and models exist for many of them. Other topics are the
influences on the Earth's atmosphere, long and short term climate
variations. The last chapters discuss the protection against enhanced
radiation environment in view of upcoming manned missions to the
Moon and Mars, and the threat from space debris, asteroids and
meteoroids. Since the field is quite interdisciplinary, the
book will be of interest to scientists working in different fields
such as solar physics, geophysics, and space physics. Link: http://www.springer.com/west/home/generic/search/results?SGWID=4-40109-22-173699408-0
Title: Solar Variations and Climate on Planets
Authors: Hanslmeier, A.
Bibcode: 2007ASPC..370...30H
Altcode:
The Sun is a variable star on different time scales. During its
evolution it considerably changed its luminosity and activity. The
early Sun was faint but very active and this had important consequences
for the evolution of the early planetary atmospheres. The importance
of enhanced early solar activity at those evolutionary phases will be
demonstrated by a short analysis of two recently observed solar enhanced
activity events. From these events one can infer the importance of
sunspots as indicator of solar activity and the solar variation in
UV during times of enhanced sunspot activity was measured. The
solar input is the driver for climate on planets. It is extremely
important to have accurate estimates of a variation of this input. At
present, the variations are low in the visible but still high in the
UV influencing e.g. higher layers in the Earth's atmosphere.
Title: Coronal Mass Ejection (CME) Activity of Low Mass M
Stars as An Important Factor for The Habitability of Terrestrial
Exoplanets. I. CME Impact on Expected Magnetospheres of Earth-Like
Exoplanets in Close-In Habitable Zones
Authors: Khodachenko, Maxim L.; Ribas, Ignasi; Lammer, Helmut;
Grießmeier, Jean-Mathias; Leitner, Martin; Selsis, Franck; Eiroa,
Carlos; Hanslmeier, Arnold; Biernat, Helfried K.; Farrugia, Charles
J.; Rucker, Helmut O.
Bibcode: 2007AsBio...7..167K
Altcode:
Low mass M- and K-type stars are much more numerous in the solar
neighborhood than solar-like G-type stars. Therefore, some of them
may appear as interesting candidates for the target star lists of
terrestrial exoplanet (i.e., planets with mass, radius, and internal
parameters identical to Earth) search programs like Darwin (ESA) or
the Terrestrial Planet Finder Coronagraph/Inferometer (NASA). The
higher level of stellar activity of low mass M stars, as compared
to solar-like G stars, as well as the closer orbital distances of
their habitable zones (HZs), means that terrestrial-type exoplanets
within HZs of these stars are more influenced by stellar activity than
one would expect for a planet in an HZ of a solar-like star. Here we
examine the influences of stellar coronal mass ejection (CME) activity
on planetary environments and the role CMEs may play in the definition
of habitability criterion for the terrestrial type exoplanets near M
stars. We pay attention to the fact that exoplanets within HZs that
are in close proximity to low mass M stars may become tidally locked,
which, in turn, can result in relatively weak intrinsic planetary
magnetic moments. Taking into account existing observational data
and models that involve the Sun and related hypothetical parameters
of extrasolar CMEs (density, velocity, size, and occurrence rate), we
show that Earth-like exoplanets within close-in HZs should experience a
continuous CME exposure over long periods of time. This fact, together
with small magnetic moments of tidally locked exoplanets, may result in
little or no magnetospheric protection of planetary atmospheres from a
dense flow of CME plasma. Magnetospheric standoff distances of weakly
magnetized Earth-like exoplanets at orbital distances <=0.1 AU can
be shrunk, under the action of CMEs, to altitudes of about 1,000 km
above the planetary surface. Such compressed magnetospheres may have
crucial consequences for atmospheric erosion processes. Key Words: M
stars-Stellar activity-Coronal mass ejections-Habitability-Terrestrial
exoplanets-Planetary magnetospheres-Terrestrial planet finding
missions. Astrobiology 7(1), 167-184.
Title: Observational Characteristics of Magnetic Reconnection in a
Two-Ribbon Flare
Authors: Miklenic, C. H.; Veronig, A. M.; Vršnak, B.; Hanslmeier, A.
Bibcode: 2007CEAB...31...39M
Altcode:
A well-observed GOES M3.9 two-ribbon flare was analysed in order
to derive the local reconnection rate (coronal electric field) and
the global reconnection rate (magnetic flux change rate), as well
as the energy release rate (Poynting flux) in a two-ribbon flare
from chromospheric/photospheric observations, using TRACE 1600 Å,
Kanzelhöhe Hα, SOHO/MDI, and RHESSI hard X-ray (HXR) data. We found
good temporal correlations between the derived time profiles and
observed HXR flux. Furthermore, it was confirmed that equal shares of
positive and negative magnetic flux participated in the reconnection
process. The findings indicate that the 2D reconnection model is
applicable to the analysed flare.
Title: The Joint Information System - Résumé after One Year
Authors: Kienreich, I.; Hanslmeier, A.; Sosa, A.
Bibcode: 2007CEAB...31..309K
Altcode:
The Joint Information System (JIS) is a fully operable computing
tool, which is a combination of a database and interactive web pages,
reachable under the web address http://www.solarJIS.com. It is the
first-rate aim of this tool to be a platform for all European solar
physicists as well as for all other interested ones, which facilitates
the access to information about institutes, groups and physicists which
work in the field of solar physics. Now, one year after the start of
JIS we want to give a brief summary of the success of this tool and
discuss possible future plans.
Title: Analysis of the Flare Wave Associated with the 3B/X3.8 Flare
of January 17, 2005
Authors: Thalmann, J. K.; Veronig, A. M.; Temmer, M.; Vršnak, B.;
Hanslmeier, A.
Bibcode: 2007CEAB...31..187T
Altcode:
The flare wave associated with the 3B/X3.8 flare and coronal mass
ejection (CME) of January 17, 2005 are studied using imaging data
in the Hα and EUV spectral channels. Due to the high-cadence Hα
observations from Kanzelhöhe Solar Observatory (KSO), a distinct
Moreton wave can be identified in ∼40 Hα frames over a period
of ∼7 minutes. The associated coronal EIT wave is identifiable in
only one EUV frame and appears close to the simultaneously observed
Moreton wave front, indicating that they are closely associated
phenomena. Beside the morphology of the wave across the solar disc
(covering an angular extend of ∼130°), the evolution in different
directions is studied to analyse the influence of a coronal hole (CH)
on the wave propagation. The Moreton wave shows a decelerating character
which can be interpreted in terms of a freely propagating fast-mode MHD
shock. The parts of the wave front moving towards the CH show a lower
initial and mean speed, and a greater amount of deceleration than the
segments moving into the undisturbed direction. This is interpreted
as the tendency of high Alfvén velocity regions to influence the
propagation of wave packets.
Title: Solar Rotation Velocity Determined by Coronal Bright Points -
New Data and Analysis
Authors: Mulec, M.; Brajša, R.; Wöhl, H.; Hanslmeier, A.; Vršnak,
B.; Ruždjak, V.; Hochedez, J. -F.; Engler, J.
Bibcode: 2007CEAB...31....1M
Altcode:
Full-disc solar images obtained with the Extreme Ultraviolet Imaging
Telescope on board the Solar and Heliospheric Observatory were used
to analyse solar differential rotation determined by tracing coronal
bright points. Rotation velocity residuals, meridional motions and
their relationship are investigated for a new data set from October
1, 1999 to March 31, 2000. Further we take care for the evolution
of the single structures, dividing them into Point-Like-Structures,
Small Loops and Small Active Regions and analysing their variation in
intensity and size.
Title: Sungrabber - Software for Measurements on Solar Synoptic Images
Authors: Hržina, D.; Roša, D.; Hanslmeier, A.; Ruždjak, V.;
Brajša, R.
Bibcode: 2007CEAB...31..273H
Altcode:
Measurement of positions of the tracers on synoptic solar images and
conversion to heliographic coordinates is a time-consuming procedure
with different sources of errors. To make measurements faster and
easier, the application "Sungrabber" was developed. The data of the
measured heliographic coordinates are stored in text files which are
linked to the related solar images, which allows also a fast and simple
comparison of the measurements from different sources. Extension of
the software is possible and therefore Sungrabber can be used for
different purposes (e.g. determining the solar rotation rate, proper
motions of the tracers on the Sun, etc.).
Title: Cosmic Ray Variation
Authors: Hanslmeier, A.
Bibcode: 2007CEAB...31..245H
Altcode:
In recent years space weather and space climate became very
important topics not only for pure astrophysical interest but also
for societal ones. In that context cosmic rays play an important role
and we will overview their general properties, their origin and give
some applications of how they influence the dynamics of the Earth's
atmosphere. We give examples of two selected events and show the
correlation between neutron flux measurements and the flare index.
Title: Space and time variation of the solar granulation .
Authors: Muller, R.; Hanslmeier, A.; Saldaña-Muñoz, M.
Bibcode: 2007MmSAI..78...71M
Altcode:
Granulation images, taken on film with the 50 cm refractor of the Pic du
Midi Observatory between 1978 and 1993, have been analysed. The solar
granulation appears to vary, both in space, along the solar equator,
and in time, in phase with the activity cycle. Around the equator, the
granulation scale varies with an amplitude as large as 15%; the contrast
varies similarly: where the scale increases, the contrast increases
too. Concerning the time variation, only a variation of the contrast is
detected: it is smaller at periods of solar maxima. We cannot quantify
the amplitude of the variation because of photometic uncertainties. We
do not detect any variation of the scale of the granulation: it must
be of much lower amplitude than the contrast variation.
Title: Reconnection and energy release rates in a two-ribbon flare
Authors: Miklenic, C. H.; Veronig, A. M.; Vršnak, B.; Hanslmeier, A.
Bibcode: 2007A&A...461..697M
Altcode:
Aims:The aim of this study was to derive the local reconnection
rate (coronal electric field) and the global reconnection rate
(magnetic flux change rate), as well as the energy release rate
(Poynting flux), in a two-ribbon flare from chromospheric/photospheric
observations. Furthermore, we tested whether equal shares of positive
and negative magnetic flux are involved in the flare process.
Methods: A well-observed GOES M3.9 two-ribbon flare was analyzed. The
required observables (ribbon expansion velocity, newly brightened area,
and magnetic field strength at the ribbon front) were extracted from
the TRACE 1600 Å and Kanzelhöhe Hα image time series, and a SOHO
MDI magnetogram. Furthermore, the ratio of the converted positive
vs. negative magnetic flux was determined. Both RHESSI hard X-ray
20-60 keV full-disk time profiles and subregion time profiles derived
from a time series of RHESSI images in the same energy range were used
as independent, observable proxies for the energy release rate. The
RHESSI images were also used to localize the sites where the bulk
of the energy was deposited by fast electrons.
Results: We
found good temporal correlations between the derived time profiles
(local and global reconnection rate, Poynting flux) and observed
HXR flux. The local reconnection-rate peak values ranged from 2.7 {V
cm-1} to 11.8 {V cm-1}, whereas the positive
and the negative magnetic flux covered by the flare emission were
equal within 5-10%.
Conclusions: .The results indicate that
the local reconnection rate, the global reconnection rate, and the
energy release rate in a simple two-ribbon flare can be derived from
chromospheric/photospheric observations. Furthermore, it was confirmed
that equal shares of positive and negative magnetic flux participated
in the reconnection process.
Title: Dynamics of Magnetic Bright Points in an Active Region
Authors: Möstl, C.; Hanslmeier, A.; Sobotka, M.; Puschmann, K.;
Muthsam, H. J.
Bibcode: 2006SoPh..237...13M
Altcode: 2006SoPh..tmp....2M
A high-quality 80-minute time series of a part of a sunspots moat
(18 ″ × 23 ″) in the G-band (4308.64 Å) has been analysed
to measure the horizontal velocities of Magnetic Bright Points
(MBPs). The observations were carried out in June 2004 at the new
1-meter Swedish Solar Telescope in La Palma. Spatial resolution was
estimated to be 0.17 ″ or 125 km on the Sun, and images were taken
in a frame selection mode in a 20-seconds interval. Individual feature
tracking of MBPs with manual selection and automated tracking has been
performed. The intensity of MBPs increases with size. The mean value
in a MBP-velocity histogram was found to be 1.11 km s −1
and it shows good accordance with an abnormal granulation-velocity
histogram. MBP velocity histograms as presented here can be taken
as an input for coronal heating models in an active region. However,
MBPs move slower in an active region than in the network (presumably
because of the higher active region magnetic flux) and hence, a process
that includes dissipation of MHD waves through fast MBP motions (>2
km s −1) may not alone explain the observed properties
of the corona.
Title: Hemispheric sunspot numbers {Rn} and {Rs}
from 1945-2004: catalogue and N-S asymmetry analysis for solar
cycles 18-23
Authors: Temmer, M.; Rybák, J.; Bendík, P.; Veronig, A.; Vogler,
F.; Otruba, W.; Pötzi, W.; Hanslmeier, A.
Bibcode: 2006A&A...447..735T
Altcode:
From sunspot drawings provided by the Kanzelhöhe Solar Observatory,
Austria, and the Skalnaté Pleso Observatory, Slovak Republic, we
extracted a data catalogue of hemispheric Sunspot Numbers covering
the time span 1945-2004. The validated catalogue includes daily,
monthly-mean, and smoothed-monthly relative sunspot numbers
for the northern and southern hemispheres separately and is
available for scientific use. These data we then investigated with
respect to north-south asymmetries for almost 6 entire solar cycles
(Nos. 18-23). For all the cycles studied, we found that the asymmetry
based on the absolute asymmetry index is enhanced near the cycle
maximum, which contradicts to previous results that are based on the
normalized asymmetry index. Moreover, the weak magnetic interdependence
between the two solar hemispheres is confirmed by their self-contained
evolution during a cycle. For the time span 1945-2004, we found that
the cycle maxima and also the declining and increasing phases are
clearly shifted, whereas the minima seem to be in phase for both
hemispheres. The asymmetric behavior reveals no obvious connection
to either the sunspot cycle period of ~11- or the magnetic cycle of
~22-years. The most striking excess of activity is observed for the
northern hemisphere in cycles 19 and 20.
Title: Highly energetic activity phenomena of main-sequence stars
Authors: Leitzinger, M.; Odert, P.; Hanslmeier, A.; Ribas, I.;
Konovalenko, A. A.; Vanko, M.; Lammer, H.; Khodachenko, M. L.; Rucker,
H. O.
Bibcode: 2006epsc.conf..226L
Altcode:
Stellar activity can have major consequences for the habitability
of nearby terrestrial planets. In view of forthcoming habitable
planet finding missions like Darwin (ESA) and TPF (NASA), a detailed
knowledge of the activity characteristics of possible target stars
is essential for the design of these missions. We investigate the
CME- and Flaring- activity of nearby single main-sequence G, K,
and M stars, taking into account the association of decameter radio
type II bursts and CMEs on the Sun (1st approach) as well as the
fluxratio of the CIII 1176Å multiplet and the CIII 977Å singlet as
a diagnostic for electron density (2nd approach). Three observational
campaigns are planned in the near future for implementation of the 1st
approach. The radio observations will be carried out at the UTR-2 of
the Radioastronomical Institute of the Ukrainian Academy of Sciences
in Kharkov/Ukraine. Simultaneous observations in the optical range
(UBVRI photometry, optical spectroscopy) are also planned and will
be carried out at the Astronomical Institute of the Slovak Academy of
Sciences in Tatranská Lomnica/Slovakia and the Observatory Lustbühel
of the Institute of Physics/IGAM of the Karl-Franzens University in
Graz/Austria, respectively. The 2nd approach is implemented using
existing spectral timeseries of G, K, and M stars obtained by the
FUSE satellite.
Title: Hemispheric Sunspot Numbers 1945--2004: data merging from
two observatories
Authors: Temmer, M.; Rybák, J.; Bendík, P.; Veronig, A.; Vogler,
F.; Pötzi, W.; Otruba, W.; Hanslmeier, A.
Bibcode: 2006CEAB...30...65T
Altcode:
For the time span 1945--2004 from daily sunspot drawings northern
and southern relative sunspot numbers are extracted using drawings
provided by Kanzelhöhe Solar Observatory, Austria, and Skalnaté Pleso
Observatory, Slovak Republic. The derived data will be used to improve
and extend an already existing catalogue of hemispheric sunspot numbers
(Temmer et al., 2002). Since northern and southern solar hemispheres
do not evolve in phase during the cycle, hemispheric data are very
important for activity studies. In the present paper the compilation
of the data for the period 1945--2004 is described. Furthermore as a
quality check of the derived hemispheric data a regression analysis and
the comparison to the international hemispheric sunspot numbers from
the Sunspot Index Data Center for the time span 1992--2004 is presented.
Title: Activity of M-type stars - effects on planetary habitability
Authors: Odert, P.; Leitzinger, M.; Hanslmeier, A.; Lammer, H.;
Khodachenko, M. L.; Ribas, I.; Vanko, M.; Konovalenko, A. A.; Rucker,
H. O.
Bibcode: 2006epsc.conf..227O
Altcode:
M-type stars - effects on planetary habitability P. Odert (1),
M. Leitzinger (1), A. Hanslmeier (1), H. Lammer (2), M. L. Khodachenko
(2), I. Ribas (3), M. Vanko (4), A. A. Konovalenko (5), H. O. Rucker
(2) (1) Institute of Physics/IGAM, University of Graz, Austria, (2)
Space Research Institute, Austrian Academy of Sciences, Graz, Austria,
(3) Institut d'Estudis Espacials de Catalunya/CSIC, Bellaterra, Spain,
(4) Astronomical Institute, Slovak Academy of Sciences, Tatranská
Lomnica, Slovakia, (5) Institute of Radio Astronomy, Ukrainian Academy
of Sciences, Kharkov, Ukraine M-type stars have often been ruled out
as promising hosts for habitable planets. Unlike earlier assumptions,
several studies of the last decade have shown that M stars might not
be as hostile as previously expected. Nevertheless, their quality as
habitable planet hosts is still debated. One of the major issues is
their strong activity, which they exhibit particularly during the first
few Gyrs on the main sequence. Theoretical studies indicate that high
levels of short-wavelength (XUV) radiation, flares and coronal mass
ejections may lead to enhanced atmospheric losses on close planets. To
address this topic, we are currently working on the compilation of a
catalog of M-type stars, which will include all known M dwarfs within
25 pc of the Sun. Besides basic stellar properties, this catalog will
include in particular data on stellar activity and properties relevant
to planetary habitability. This catalog will then serve as a basis
for the general investigation of M star activity, as well as for the
estimation of a star's quality as a habitable planet host.
Title: 11-Year cyclic variation of the solar granulation
Authors: Muller, R.; Saldaña-Muñoz, M.; Hanslmeier, A.
Bibcode: 2006AdSpR..38..891M
Altcode:
A homogeneous (in terms of spatial resolution and optical set-up) set
of images of the solar granulation, obtained regularly between 1978 and
1991 with the 50-cm refractor of the Pic du Midi Observatory, has been
analyzed to seek for possible variations related with the solar activity
cycle. A simple, but reliable and objective, statistical analysis was
performed (autocorrelation and power spectrum), which provides results
unaffected by any processing parameter. The main uncertainties come from
the statistical variation of the granulation pattern in the analyzed
area (70″ × 70″), from the film calibration and from the noise
produced by film granularity. Despite these uncertainties, the solar
granulation appears to vary in phase with the solar cycle as follow:
the contrast decreases with increasing activity, while the horizontal
scale seems to increase. The uncertainty of the film calibrations
prevents us, at this point of our investigation, to quantity the
amplitude of the contrast variation.
Title: Theoretical and Observational Features of Magnetic Reconnection
Authors: Biernat, H. K.; Semenov, V. S.; Penz, T.; Miklenic, C.;
Veronig, A.; Hanslmeier, A.; Vršnak, B.; Heyn, M. F.; Ivanov, I. B.;
Ivanova, V. V.; Kiehas, S. A.; Langmayr, D.
Bibcode: 2006CEAB...30...75B
Altcode:
We present general solutions of the time--dependent Petschek--type
model of magnetic reconnection for a compressible plasma. The
disruption of a tangential discontinuity because of a localized
decrease of the resistivity leads to the generation of several
MHD wave modes. By solving the Riemann problem, the behavior of
these modes can be visualized. Additionally, disturbances of the
ambient plasma environment by the propagating shock structures
can be modeled. As an observational feature, the determination
of the reconnection rate in a two--ribbon flare is presented.
Title: Periodical patterns in major flare occurrence and their
relation to magnetically complex active regions
Authors: Temmer, M.; Veronig, A.; Rybák, J.; Brajša, R.; Hanslmeier,
A.
Bibcode: 2006AdSpR..38..886T
Altcode:
A periodical occurrence rate of major solar flares (observed in hard
X-rays) of ∼24 days (synodic) was first reported by Bai (1987)
[Bai, T. Distribution of flares on the sun superactive regions and
active zones of 1980 1985. ApJ 314, 795 807, 1987] for the years 1980
1985. Here, we report a significant relation between the appearance of
the 24-day period in major Hα flares and magnetically complex sunspot
groups (i.e., including a γ and/or δ configuration). From synoptic
maps of magnetograms (NSO/KP) patterns in the magnetic flux evolution
are traced which might be the cause of the 24-day period observed in
flare activity.
Title: Acoustic Flux and Turbulence in the Solar Photosphere
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2006CEAB...30...11H
Altcode:
Using slit scans of solar photospheric spectral lines originating in
the middle photosphere a 2-D field on the Sun was obtained and the
occurrence of acoustic flux is investigated. As proxies for acoustic
flux generation enhanced turbulence (measured by fwhm variations) as
well as large continuum intensity values are used. The results show
that acoustic flux is not limited to the intergranular space and is
also produced by horizontal motions that may become supersonic leading
to turbulence. These motions lead to brightenings as it was predicted
by theoretical models.
Title: On the mechanisms of MHD wave damping in the partially ionized
solar plasmas
Authors: Khodachenko, M. L.; Rucker, H. O.; Oliver, R.; Arber, T. D.;
Hanslmeier, A.
Bibcode: 2006AdSpR..37..447K
Altcode:
In order to conclude about the role of collisional friction,
viscous and thermal conductivity mechanisms of MHD wave damping
in the solar partially ionized plasmas, a quantitative comparative
study of efficiency of all these mechanisms in different parts of
the solar atmosphere is performed. All the important solar MHD modes
are considered: Alfvén wave, fast magnetoacoustic wave and slow
magnetoacoustic/acoustic wave. In general, the correct description of
MHD wave damping requires the consideration of all energy dissipation
mechanisms via the inclusion of the appropriate terms in the generalized
Ohm’s law, the momentum, energy and induction equations. Specific
forms of the generalized Ohm’s law and induction equation, suitable
for partially ionized regions of the solar atmosphere, are presented
and discussed.
Title: Dynamics of solar mesogranulation
Authors: Leitzinger, M.; Brandt, P. N.; Hanslmeier, A.; Pötzi, W.;
Hirzberger, J.
Bibcode: 2005A&A...444..245L
Altcode:
Using a 45.5-h time series of photospheric flow fields generated
from a set of high-resolution continuum images (SOHO/MDI) we analyze
the dynamics of solar mesogranule features. The series was prepared
applying a local correlation tracking algorithm with a 4.8´´ FWHM
window. By computing 1-h running means in time steps of 10 min we
generate 267 averaged divergence maps that are segmented to obtain
binary maps. A tracking algorithm determines lifetimes and barycenter
coordinates of regions of positive divergence defined as mesogranules
(MGs). If we analyze features of lifetimes ≥1 h and of areas ≥5
Mm{2 we find a mean drift velocity of 304 m s-1
(with ± 1σ variation of 180 m s-1), a mean travel distance
of 2.5 ± 1.8 Mm, a mean lifetime of 2.6 ± 1.8 h, and a 1/e decay time
of 1.6 h for a total of 2022 MGs. The advective motion of MGs within
supergranules is seen for 50 to 70% of the long-lived (≥4 h) MGs while
the short-lived ones move irregularly. If only the long-lived MGs are
further analyzed the drift velocities reduce to 207 m s-1
and the travel distances increase to 4.1 Mm on average, which is an
appreciable fraction of the supergranular radius. The results are
largely independent of the divergence segmentation level.
Title: Hemispheric Sunspot Numbers RN and RS from 1945-2004: Extended
and Improved Catalogue
Authors: Temmer, M.; Rybák, J.; Veronig, A.; Bendík, P.; Vogler,
F.; Pötzi, W.; Otruba, W.; Hanslmeier, A.
Bibcode: 2005ESASP.600E..52T
Altcode: 2005ESPM...11...52T; 2005dysu.confE..52T
No abstract at ADS
Title: Influence of the 5-min oscillations on solar photospheric
layers. I. Quiet region
Authors: Odert, P.; Hanslmeier, A.; Rybák, J.; Kučera, A.; Wöhl, H.
Bibcode: 2005A&A...444..257O
Altcode:
Time series of 1D spectrograms are used to study the influence of the
5-min oscillations on intensity and velocity fields of different layers
of the quiet solar photosphere. We study the continuum intensity field
along with intensity and corresponding velocity patterns of the mid and
upper photosphere, obtained from two Fe lines. Oscillations seem to
dominate the intensity and velocity fields of the higher atmospheric
layers. Our results confirm the fast decay of the granular intensity
structure with height. From correlations of temperature structures
at three different photospheric levels we conclude that there are
rapid changes of the structures in the lower photosphere, which are
valid for the duration of the time series, while for the upper levels
changes of the stuctures are fainter and show significant periodic
character. The velocity pattern, on the other hand, shows a periodic
propagation through the photosphere. The tests of the influence of
seeing conditions on the data are considered.
Title: Jis - the Joint Information System
Authors: Kienreich, I.; Hanslmeier, A.; Palle, P.; Sosa, A.
Bibcode: 2005ESASP.600E.159K
Altcode: 2005dysu.confE.159K; 2005ESPM...11..159K
No abstract at ADS
Title: Wave Phenomena Associated with the X3.8 Flare/cme of
17-JAN-2005
Authors: Temmer, M.; Veronig, A.; Vršnak, B.; Thalmann, J.;
Hanslmeier, A.
Bibcode: 2005ESASP.600E.144T
Altcode: 2005ESPM...11..144T; 2005dysu.confE.144T
No abstract at ADS
Title: Segmentation, Classification and Analysis of a Solar
Granulation Image Series
Authors: Saldaña Muñoz, M.; Muller, R.; Hanslmeier, A.
Bibcode: 2005ESASP.600E..69S
Altcode: 2005dysu.confE..69S; 2005ESPM...11...69S
No abstract at ADS
Title: Analysis of Selected Rhessi Microflares
Authors: Stoiser, S.; Veronig, A. M.; Brown, J. C.; McTiernan, J. M.;
Hanslmeier, A.
Bibcode: 2005ESASP.600E.142S
Altcode: 2005dysu.confE.142S; 2005ESPM...11..142S
No abstract at ADS
Title: Time series of high resolution photospheric spectra in a
quiet region of the Sun. II. Analysis of the variation of physical
quantities of granular structures
Authors: Puschmann, K. G.; Ruiz Cobo, B.; Vázquez, M.; Bonet, J. A.;
Hanslmeier, A.
Bibcode: 2005A&A...441.1157P
Altcode: 2012arXiv1205.1725P
From the inversion of a time series of high resolution slit spectrograms
obtained from the quiet sun, the spatial and temporal distribution
of the thermodynamical quantities and the vertical flow velocity is
derived as a function of optical depth (logτ) and geometrical height
(z). Spatial coherence and phase shift analyses between temperature
and vertical velocity depict the height variation of these physical
quantities for structures of different size. An average granular
cell model is presented, showing the granule-intergranular lane
stratification of temperature, vertical velocity, gas pressure and
density as a function of logτ and z. Studies of a specific small
and a specific large granular cell complement these results. A strong
decay of the temperature fluctuations with increasing height together
with a less efficient penetration of smaller cells is revealed. The
T-T coherence at all granular scales is broken already at logτ = -1
or z ~ 170 km. At the layers beyond, an inversion of the temperature
contrast at granular scales >1.5 arcsec is revealed, both in logτ
and z. At deeper layers the temperature sensitivity of the H-
opacity leeds to much smaller temperature fluctuations at equal logτ
than at equal z, in concordance with Stein & Nordlund (1998, ApJ,
499, 914). Vertical velocities are in phase throughout the photosphere
and penetrate into the highest layers under study. Velocities at the
largest granular scales (~ 4´´) are still found even at logτ ~ -2.8
or z ~ 370 km. Again a less efficient height penetration of smaller
cells concerning convective velocities is revealed, although still
at logτ ~ -2 or z ~ 280 km structures >1.4 arcsec are detected. A
similar size distribution of velocity and temperature structures with
height provides observational evidence for substantial overshoot into
the photosphere. At deep photospheric layers, the behaviour of the
vertical velocities reflected in simulations is for the first time
qualitatively reproduced by observations: intergranular velocities
are larger than the granular ones and, both reach extrema, where the
granular one is shifted towards higher layers.
Title: Photometry of umbral dots
Authors: Sobotka, M.; Hanslmeier, A.
Bibcode: 2005A&A...442..323S
Altcode:
Until now, the size of umbral dots has been considered to be below the
resolution limit of large solar telescopes. We analyze observations
of two sunspots and two pores, acquired in September 2003 with the
new 1-m Swedish Solar Telescope, La Palma. White-light images with a
resolution better than 0.15 arcsec were taken simultaneously in blue
(451 nm) and red (602 nm) wavelength bands. They were corrected for
scattered light and restored for the instrumental profile of the
telescope. Intensities, diameters and positions of umbral dots were
measured in aligned pairs of images in the blue and red wavelength
band. We find that observed intensities of umbral dots are correlated
with local intensities of umbral background. On average, UDs are by
about 1000 K hotter than the coolest area in the umbra and by 500-1000
K cooler than the undisturbed photosphere. Individual UDs may reach or
exceed the average photospheric brightness and temperature. Histograms
of observed diameters peak at 0.23 arcsec (170 km). This indicates
that the majority of umbral dots are spatially resolved with the 1-m
telescope. The mean nearest-neighbour distance between umbral dots is
0.4 arcsec and their average observed filling factor is 9%. The method
of two-colour photometry is discussed and applied to obtain average
"true" intensities and diameters. About 50% of umbral dots are brighter
than the quiet photosphere and the average "true" diameter of umbral
dots is 100 km. However, the latter results might be influenced by
systematic errors of the method.
Title: VizieR Online Data Catalog: Hemispheric Sunspot Numbers
1945-2004 (Temmer+, 2006)
Authors: Temmer, M.; Rybak, J.; Bendik, P.; Veronig, A.; Vogler, F.;
Otruba, W.; Poetzi, W.; Hanslmeier, A.
Bibcode: 2005yCat..34470735T
Altcode:
From sunspot drawings provided by the Kanzelhoehe Solar Observatory,
Austria, and the Skalnate Pleso Observatory, Slovak Republic,
a data catalogue of hemispheric Sunspot Numbers covering the time
span 1945-2004 is extracted. The validated catalogue includes daily,
monthly-mean and smoothed-monthly relative sunspot numbers for the
northern and southern hemispheres separately and is available for
scientific use. Based on this data set an analysis concerning the
North-South asymmetry is made within this paper. (2 data files).
Title: What causes the 24-day period observed in solar flares?
Authors: Temmer, M.; Rybák, J.; Veronig, A.; Hanslmeier, A.
Bibcode: 2005A&A...433..707T
Altcode:
Previous studies report a 24-day (synodic) period in the occurrence
rate of solar flares for each of the solar cycles studied, Nos. 19-22
(Bai 1987, ApJ, 314, 795; Temmer et al. 2004, Sol. Phys. 221,
325). Here we study the 24-day period in the solar flare occurrence
for solar cycles 21 and 22 by means of wavelet power spectra together
with the solar flare locations in synoptic magnetic maps. We find
that the 24-day peak revealed in the power spectra is just the
result of a particular statistical clumping of data points, most
probably caused by a characteristic longitudinal separation of about
+40circ to +50circ of activity complexes in
successive Carrington rotations. These complexes appear as parallel,
diverging or converging branches in the synoptic magnetic maps and
are particularly flare-productive.
Title: JIS - the Joint Information System
Authors: Hanslmeier, A.; Kienreich, I.; Palle, P.; Sosa, A.
Bibcode: 2005HvaOB..29..329H
Altcode:
The main aim of JIS (Joint Information System) is to overcome the
present lack of detailed knowledge amongst the European Solar Physics
community. This lack of knowledge occurs at several levels: groups of
researchers, institutions, scientific activities, running programs,
resources, new opportunities, observational campaigns etc. JIS
will not be data archives -- this is the aim of EGSO, but will provide
all information mentioned above collecting all possible data about the
institutes and scientists working in the field of solar physics. All
European solar physicists will be provided with this information
by means of an easy accessible webpage including different inquiry
modes (query by country, university, institute, scientist and area
of research). Until now such a system did not exist in Europe, but in
foreseeable future a user-friendly and logical structured webpage will
take on this task.
Title: The Two Complexes of Activity Observed in the Northern
Hemisphere during 1982 and the 24-Day Periodicity of Flare Occurrence
Authors: Ruždjak, V.; Ruždjak, D.; Brajša, R.; Temmer, M.;
Hanslmeier, A.
Bibcode: 2005HvaOB..29..117R
Altcode:
Daily numbers of solar Hα flares of importance classes ≥ 1 for
the northern solar hemisphere in 1982 are studied applying wavelet
power spectra (WPS). Special attention is paid to the occurrence of a
24-day period in the WPS. The wavelet power spectra method is combined
with synoptic maps of the magnetic fields. Separately, flare indices
of two activity complexes mainly contributing to flare occrrence in
this period are examined. It is found that the detected 24-day signal
in the WPS is mainly a consequence of the presence of the two flare
activity complexes separated by about 45° in longitude during several
succesive Carrington rotations.
Title: Dynamics of Solar Mesogranulation
Authors: Leitzinger, M.; Brandt, P. N.; Hanslmeier, A.; Pötzi, W.;
Hirzberger, J. K.
Bibcode: 2005HvaOB..29...49L
Altcode:
Using a 45.5-h time series of photospheric flow fields generated from
a set of high-resolution continuum images (SOHO/MDI) we analyse the
dynamics of solar mesogranule features. The series was prepared by
Shine et al. (2000) applying a local correlation tracking algorithm
with a 4.8 arcsec FWHM window. By computing 1-h running means in time
steps of 10 minutes we generate 267 averaged divergence maps which
are then segmented to obtain binary maps. A tracking algorithm then
determines lifetimes and barycentre coordinates of regions of positive
divergence defined as mesogranules (MGs). If we analyse features of
lifetimes ≥1 h and areas ≥5 Mm2 we find a mean drift velocity of
304 ms, a mean travel distance of 2.5 Mm, a mean lifetime of 2.6 h,
and a 1/e decay time of 1.6 h for a total of 2022 MGs. The advective
motion of MGs within supergranules, which was found by Muller et
al. (1992) and confirmed by Shine et al. (2000), is seen for half to
two-thirds of the long-lived (≥4 h) MGs while the short-lived ones
move irregularly. The results prove to be nearly independent of the
divergence segmentation level.
Title: The Faint Young Sun Problem
Authors: Hanslmeier, A.
Bibcode: 2005ASSL..320..267H
Altcode: 2005smp..conf..267H
No abstract at ADS
Title: Solar Irradiance Variations Modelled from Ca II K Excess and
Magnetic Field
Authors: Vogler, F. L.; Brandt, P. N.; Otruba, W.; Hanslmeier, A.
Bibcode: 2005HvaOB..29...79V
Altcode:
The facular contribution (Δ S(λ)/S(λ))_{f} to the variation of the
total solar irradiance Δ S(λ)/S(λ), for two continuum wavelengths
and for a period of 60 not consecutive days in 1999, is calculated
according to two different methods, namely via RISE/PSPT Ca II K
images and via magnetograms of the MDI instrument on board of the
SOHO spacecraft. The results are correlated with the values of the
total irradiance channel of the VIRGO instrument on board of SOHO. The
correlation coefficient for the first method (via Ca II K images) is
0.55, and 0.23 for the second method (via magnetograms). Particularly
with regard to faculae, Ca II K irradiance appears to be much more
representative than the line-of-sight magnetic field. For use of
the magnetograms the relationship between the Ca II K excess E_{k}
and the line-of-sight magnetic flux density |B| is analysed. E_{k} is
measured in dependence on the two variables μ and |B|. A multivariate
fit yields a compact presentation of this function and the exponent
β of the power law E_{k}=α\cdot|B|^{β} is determined; the values
0.48≤ β ≤ 0.57 agree with those found by Harvey and White (1999).
Title: Solar Magnetic Phenomena
Authors: Hanslmeier, Arnold; Veronig, Astrid; Messerotti, Mauro
Bibcode: 2005ASSL..320.....H
Altcode: 2005smp..conf.....H
This book contains the proceedings of the Summerschool and Workshop
"Solar Magnetic Phenomena" held from 25 August to 5 September 2003
at the Solar Observatory Kanzelhoehe, which belongs to the Institute
for Geophysics, Astrophysics and Meteorology of the University of
Graz, Austria. The book contains the contributions from six invited
lecturers, They give an overview on the following topics: observations
of the photosphere and chromosphere, solar flares observations and
theory, coronal mass ejections and the relevance of magnetic helicity,
high-energy radiation from the Sun, the physics of solar prominences
and highlights from the SOHO mission. The lectures contain about 25
to 30 pages each and provide a valuable introduction to the topics
mentioned above. The comprehensive lists of references at the end
of each contribution enable the interested reader to go into more
detail. The second part of the book contains contributed papers. These
papers were presented and discussed in the workshop sessions during
the afternoons. The sessions stimulated intensive discussions between
the participants and the lecturers.
Title: On the Relation Between the Coronal Free Energy and Solar
Flare Occurrence
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2005HvaOB..29..109T
Altcode:
A significant delay with a 22-year modulation in solar flare occurrence
was found by te{temmer03solph} with respect to the solar cycle defined
on the basis of the relative sunspot number. These observational results
were modelled by te{litvi03} through a time-dependent balance of the
magnetic free energy in the solar corona. The free magnetic energy is
assumed to be depleted mainly by flares and lags behind the variation
of the energy supply (emerging magnetic flux - proxy: relative sunspot
numbers) to this system. For solar cycles 21 and 23, in accordance with
the delay obtained for flare rates, the rate of sunspot group numbers
lags behind the solar cycle maximum. Theses findings suggest that
the energy supply itself is delayed, most prominent in odd numbered
solar cycles which subsequently causes the delay observed for flare
and sunspot group occurrences.
Title: On the 24- and 155-Day Periodicity Observed in Solar Hα Flares
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2005ASSL..320..211T
Altcode: 2005smp..conf..211T
No abstract at ADS
Title: UV Radiation in the Solar System
Authors: Hanslmeier, A.; Vázquez, M.
Bibcode: 2005HvaOB..29..237H
Altcode:
The source of UV radiation in the solar system is mainly the Sun. The
influence of its various compounds as well as the variability is
discussed here. It is summarized on which time scales the solar
UV radiation is variable and by which processes it influences the
atmospheres of planets. UV radiation on solar like stars that may
be surrounded by planets plays an important role in the extension of
habitable zones in these systems.
Title: Center-to-Limb Variation of Facular Contrast Derived from
MLSO RISE/PSPT Full Disk Images
Authors: Vogler, F. L.; Brandt, P. N.; Otruba, W.; Hanslmeier, A.
Bibcode: 2005ASSL..320..191V
Altcode: 2005smp..conf..191V
No abstract at ADS
Title: Two-dimensional spectroscopic time series of solar granulation
Authors: Hanslmeier, A.; Kucera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2004SoPh..223...13H
Altcode:
In this paper we investigate the dynamics of the solar granulation
by analyzing time series of 2D spatially highly resolved
spectrograms. These were obtained by spatial scans covering a field
of 12 8″ × 20″. The advantage of this method is a high spectral
resolution, however, the data are not taken simultaneously and to
cover the field described above 50 exposures taken sequentially in
time are necessary. Therefore, to obtain one map about 2 minutes are
required. Plots of the evolution of different line parameters are
given as well as the decay of correlation functions. The correlations
between the first map of line parameters and successive maps (which are
separated by about 2 minutes) were investigated showing a rapid decay
down to a correlation coefficient of 0.4 within 4 minutes, the velocity
pattern in the field observed varies on smaller time scales. The
temporal variation of correlation between the line parameters for the
different lines shows a periodic signal related to 5-min oscillations
which could not be totally filtered. The evolution of the correlation
functions between line parameters is analyzed which gives an error
estimate of all correlation values found in the literature. For
the first time it is explicitly shown how evolution in a selected
photospheric field influences the evolution of granular/intergranular
structures.
Title: Collisional and viscous damping of MHD waves in partially
ionized plasmas of the solar atmosphere
Authors: Khodachenko, M. L.; Arber, T. D.; Rucker, H. O.; Hanslmeier,
A.
Bibcode: 2004A&A...422.1073K
Altcode:
Magnetohydrodynamic (MHD) waves are widely considered as a possible
source of heating for various parts of the outer solar atmosphere. Among
the main energy dissipation mechanisms which convert the energy of
damped MHD waves into thermal energy are collisional dissipation
(resistivity) and viscosity. The presence of neutral atoms in the
partially ionized plasmas of the solar photosphere, chromosphere and
prominences enhances the efficiency of both these energy dissipation
mechanisms. A comparative study of the efficiency of MHD
wave damping in solar plasmas due to collisional and viscous energy
dissipation mechanisms is presented here. The damping rates are taken
from Braginskii \cite{Braginskii1965} and applied to the VAL C model
of the quiet Sun (Vernazza et al. \cite{Vernazza_etal1981}). These
estimations show which of the mechanisms are dominant in which
regions. In general the correct description of MHD wave damping requires
the consideration of all energy dissipation mechanisms via the inclusion
of the appropriate terms in the generalized Ohm's law, the momentum,
energy and induction equations. Specific forms of the generalized
Ohm's Law and induction equation are presented that are suitable for
regions of the solar atmosphere which are partially ionised.
Title: Indications of shock waves in the solar photosphere
Authors: Rybák, J.; Wöhl, H.; Kučera, A.; Hanslmeier, A.;
Steiner, O.
Bibcode: 2004A&A...420.1141R
Altcode:
High resolution observations of solar granulation near the solar limb
are used in a search for hydrodynamic shocks caused by an abrupt
braking of the fast (probably supersonic) horizontal flow of the
granular plasma towards the intergranular lane. Shock signatures in
the spectral line of Fe II 6456.38 Åof one particular observed shock
event are investigated in detail. Evolution, amplitude, and spatial
relation of the spectral line characteristics of the shock event are in
agreement with predictions from numerical simulations for such shock
phenomena in the solar photosphere. The dimensions and amplitudes of
the observed shock signatures are comparable to predicted values when
seeing and instrumental effects as well as a possible obliqueness of
the shock front with respect to the observer's line-of-sight are taken
into account. The temporal evolution of such an event is observed for
the first time. The stable and declining phase of the event were studied
for a time period of almost 2 min. A particular relationship was found
between the shock event and a nearby G-band bright point located 2''
from the shock event. It is suggestive that the observed shock is a
causal consequence of the magnetic flux concentration, traced by the
G-band bright point. Such a type of shock can appear outside the flux
concentrations as a consequence of a rapid flux-tube motion.
Title: On the 24-day period observed in solar flare occurrence
Authors: Temmer, M.; Veronig, A.; Rybák, J.; Brajša, R.; Hanslmeier,
A.
Bibcode: 2004SoPh..221..325T
Altcode:
Time series of daily numbers of solar Hα flares from 1955 to
1997 are studied by means of wavelet power spectra with regard to
predominant periods in the range of ∼ 24 days (synodic). A 24-day
period was first reported by Bai (1987) for the occurrence rate of
hard X-ray flares during 1980-1985. Considering the northern and
southern hemisphere separately, we find that the 24-day period is not
an isolated phenomenon but occurs in each of the four solar cycles
investigated (No. 19-22). The 24-day period can be established also
in the occurrence rate of subflares but occurs more prominently in
major flares (importance classes ≥ 1). A comparative analysis of
magnetically classified active regions subdivided into magnetically
complex (i.e., including a γ and/or δ configuration) and non-complex
(α, β) reveals a significant relation between the appearance of
the 24-day period in Hα flares and magnetically complex sunspot
groups, whereas it cannot be established for non-complex groups. It is
suggested that the 24-day period in solar flare occurrence is related
to a periodic emergence of new magnetic flux rather than to the surface
rotation of sunspots.
Title: A multiwavelength study of solar flare waves. II. Perturbation
characteristics and physical interpretation
Authors: Warmuth, A.; Vršnak, B.; Magdalenić, J.; Hanslmeier, A.;
Otruba, W.
Bibcode: 2004A&A...418.1117W
Altcode:
The study of solar flare waves - globally propagating wave-like
disturbances usually observed in Hα as Moreton waves - has recently
come back into focus prompted by the observation of coronal waves in
the EUV with the SOHO/EIT instrument (``EIT waves"), and in several
additional wavelength channels. We study 12 flare wave events in
order to determine their physical nature, using Hα, EUV, helium I,
SXR and radioheliographic data. In the companion Paper I, we have
presented the observational data and have discussed the morphology,
spatial characteristics and the kinematics of the different flare
wave signatures. The wavefronts observed in the various spectral bands
were found to follow kinematical curves that are closely associated,
implying that they are signatures of the same physical disturbance. In
the present paper, we continue the study with a close examination of
the evolution of the common perturbation that causes the different wave
signatures, and with a detailed analysis of the metric type II radio
bursts that were associated with all flare wave events. The basic
characteristics of the waves are deceleration, perturbation profile
broadening, and perturbation amplitude decrease. This behavior can
be interpreted in terms of a freely propagating fast-mode MHD shock
formed from a large-amplitude simple wave. It is shown that this
scenario can account for all observed properties of the flare waves
in the various spectral bands, as well as for the associated metric
type II radio bursts.
Title: A multiwavelength study of solar flare waves. I. Observations
and basic properties
Authors: Warmuth, A.; Vršnak, B.; Magdalenić, J.; Hanslmeier, A.;
Otruba, W.
Bibcode: 2004A&A...418.1101W
Altcode:
Propagating wave-like disturbances associated with solar flares -
commonly observed in the chromosphere as Moreton waves - have been
known for several decades. Recently, the phenomenon has come back into
focus prompted by the observation of coronal waves with the SOHO/EIT
instrument (``EIT waves"). It has been suggested that they represent
the anticipated coronal counterpart to Moreton waves, but due to some
pronounced differences, this interpretation is still being debated. We
study 12 flare wave events in order to determine their physical nature,
using Hα, EUV, He I 10 830 Å, SXR and radioheliographic data. The
flare wave signatures in the various spectral bands are found to
lie on closely associated kinematical curves, implying that they are
signatures of the same physical disturbance. In all events, and at
all wavelengths, the flare waves are decelerating, which explains
the apparent ``velocity discrepancy" between Moreton and EIT waves
which has been reported by various authors. In this paper, the focus
of the study is on the morphology, the spatial characteristics and the
kinematics of the waves. The characteristics of the common perturbation
which causes the wave signatures, as well as the associated type II
radio bursts, will be studied in companion Paper II, and a consistent
physical interpretation of flare waves will be given.
Title: Merging two data sets of hemispheric Sunspot Numbers
Authors: Rybák, J.; Bendík, P.; Temmer, M.; Veronig, A.; Hanslmeier,
A.
Bibcode: 2004HvaOB..28...63R
Altcode:
First results on merging two data sets of hemispheric sunspot numbers
-- from the Kanzelhöhe Solar Observatory and the Skalnaté Pleso
Observatory -- for the time span 1977 -- 1978 are presented. A total
coverage of 86% was reached for the merged data set. In order to have
a homogeneous time series, the daily sunspot numbers for the full disk
from both observing stations were normalized to the international
relative sunspot number of the day. The derived hemispheric sunspot
numbers from Kanzelhöhe and Skalnaté Pleso Observatory %compared
for 290 common observing show very high correlations (r ≳ 0.95), and
the estimated data noise yields significant differences only for small
values of sunspot numbers. These outcomes demonstrate the high potential
of the applied merging procedure, and are the basis for an ongoing
project to derive hemispheric sunspot numbers back to the year 1945
using sunspot drawings from Kanzelhöhe and Skalnaté Pleso Observatory.
Title: Variation of the solar granulation structure with the solar
activity cycle
Authors: Saldaña-Muñoz, M.; Muller, R.; Hanslmeier, A.
Bibcode: 2004HvaOB..28....9S
Altcode:
Digital image processing of time series of solar granulation images
in the optical range, is used here to detect a possible solar cycle
variation of solar granulation. All images were taken with the same
instrument and setup, from 1978 and 1990 under excellent seeing
conditions. It was necessary to correct some of the images due to
the presence of data gaps in form of vertical dark lines over the
film. For this task, a particular method based on the singular value
decomposition of a matrix was developed. No other kind of filter was
applied to the images. The granular size was investigated by means
of power spectrum analysis. Some size ranges show a smooth variation
following the solar cycle with about 10% of amplitude.
Title: Importance of magnetically complex active regions on solar
flare occurrence
Authors: Temmer, M.; Veronig, A.; Rybák, J.; Brajša, R.; Hanslmeier,
A.
Bibcode: 2004HvaOB..28...95T
Altcode:
Daily numbers of solar Hα flares from 1955 to 1997 and daily numbers
of magnetically classified active regions for the time span 1964--1997
are studied applying wavelet power spectra. The occurrence of dominant
periods in the range of ∼24 days (synodic) is investigated considering
the northern and southern hemisphere separately. From the flare events
it is revealed that the 24-day period occurs in each of the four solar
cycles investigated (no. 19--22). The 24-day period can be established
also in the occurrence rate of subflares but occurs more prominently
in major flares (importance classes ≥1). Magnetically complex active
regions, i.e. including a γ and/or δ configuration, show the 24-day
period closely related to those found for major Hα flares, whereas
it cannot be established for non-complex α, β groups.
Title: Velocity field in the intergranular atmosphere
Authors: Kučera, A.; Koza, J.; Bellot Rubio, L. R.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
Bibcode: 2004HvaOB..28...19K
Altcode:
The line-of-sight velocity ľand macroturbulent velocity are studied
in the centre of the intergranular space in the solar photosphere. An
inversion method is applied to a 4-min time sequence of Stokes
I spectra of the 5, 6 and 7 lines observed with high spatial and
temporal resolutions at solar disk centre. The results are presented
in the form of the functional dependence of ľ(logτ5,t)
and (t) on the continuum optical depth τ5 at 500 nm and
time t. A ľof several hundreds of meters per second was found in the
upper photosphere (logτ5≤-1.5), where the plasma flows
away from the observer. On the contrary, upflows directed toward the
observer were found in deeper layers (logτ5>-1.5). The
typical value of in the centre of the intergranular space is found to be
∼1.7 kms, which is about 0.5 kms greater than in the adjacent granule.
Title: One-dimensional spectroscopy of the solar photosphere
Authors: Odert, P.; Hanslmeier, A.; Rybák, J.; Kučera, A.; Wöhl, H.
Bibcode: 2004HvaOB..28...37O
Altcode:
Data from a time series of spectrograms were used to study
correlative relationships between intensity and velocity in the solar
photosphere. The variations along the slit of the line parameters from
two Fe lines lying in the visible range of the spectrum were used. The
formation height difference of these lines is over 300 km. The temporal
variations of the correlation coefficients were studied, they showed
a strong influence of the 5 min-oscillations.
Title: A brief history of the solar radiation and particle flux
evolution
Authors: Lammer, H.; Ribas, I.; Grießmeier, J. -M.; Penz, T.;
Hanslmeier, A.; Biernat, H. K.
Bibcode: 2004HvaOB..28..139L
Altcode:
Many evolutionary processes in solar-planetary relations and the
evolution of planetary atmospheres can only be understood if one
recognizes the fact that the radiation and particle environment of
the Sun was not always in the same order than at present. We review
and summarize the latest research regarding the evolution of the
solar radiation and particle environment from the observations of
solar proxies - Sun-like stars - with different ages. Observations
by various satellites and studies on solar proxies show that the
early Sun was rotating more than 10 times its present rate and had
correspondingly strong dynamo-driven high energetic emissions. It can
be inferred that the early Sun may have had strong X-ray and extreme
ultraviolet (XUV) emissions up to several 100 times stronger than the
present Sun. Further, evidence of a much denser early solar wind and
the mass loss rate of the early Sun can be determined from collision
of ionized stellar winds of solar-like stars with different ages,
with the partially ionized gas in the interstellar medium. This
collision creates a population of hot decelerated neutral hydrogen
atoms, whose blue-shifted absorption component can be observed in the
Lyman-α emission line by the Hubble Space Telescope (HST). Empirical
correlations of stellar mass loss rates with X-ray surface flux values
allow one to estimate the solar wind mass flux at earlier times, when
the solar wind may have been over 1000 times more massive. We mention
also briefly some important implications for the history of planetary
atmospheres in our solar system and newly discovered exoplanets.
Title: On the mechanisms of MHD wave damping in the partially ionized
solar plasmas
Authors: Khodachenko, M. L.; Rucker, H. O.; Arber, T. D.; Hanslmeier,
A.
Bibcode: 2004cosp...35..975K
Altcode: 2004cosp.meet..975K
There exist many cases when parameters of the solar plasma are so,
that it can not be considered as a fully ionized medium. Even a small
presence of neutral atoms in plasma sometimes plays a crucial role
for dynamical and energetic processes in it. This, first of all,
concerns the processes in the solar photosphere and chromosphere and
prominences. Different interaction of electrons, ions and neutral
atoms with a magnetic field and each other causes the main specifics
of the partially ionized plasma MHD, which differs significantly from
the fully ionized case. The key point in the modelling of dynamical
processes in the partially ionized plasmas consists in inclusion into
the MHD equations set of an adequate form of the generalized Ohm's
law and corresponding magnetic induction equation, as well as in the
appropriate modification of the momentum and energy equations. These
ideas are applied for comparative study of damping of MHD waves
(Alfvén wave; fast magnetoacoustic and slow/acoustic modes) due to
collisional friction and viscosity in the partially ionized plasmas
of the low solar atmosphere and prominences. The performed analysis
indicates domination of the collisional friction damping mechanisms in
the photosphere and low chromosphere as well as in the majority of cases
with prominences. Whereas in the upper solar chromosphere collisional
and viscous damping of MHD waves are of the same order of magnitude
and should be both taken into account in the models. Specific forms
of the generalized Ohm's Law and induction equation are presented and
discussed that are suitable for regions of the solar atmosphere which
are partially ionised.
Title: 11-year cyclic variation of the solar granulation
Authors: Muller, R.; Saldana-Munoz, M.; Hanslmeier, A.
Bibcode: 2004cosp...35.1944M
Altcode: 2004cosp.meet.1944M
A homogeneous (spatial resolution and optical set-up) set of images of
the solar granulation, obtained regularly between 1978 and 1991 with
the 50-cm refractor of the Pic du Midi Observatory, has been analysed
to seek for possible variations. A simple, but reliable and objective,
statistical analysis of the images was made (autocorrelation and
power spectra), which provides results unaffected by any processing
parameters. The main noise comes from the statistical variation of
the granulation pattern in the analysed area (70" x 70"); but the
amplitude of the observed cyclic variations are largely above the
noise, and thus appear to be really of solar origin. Statistically,
the granulation is found to vary as follow: the power, in the power
spectra, decreases at all spatial frequencies, from minimum to maximum
of activity, but much more in the high frequencies range; there is no
frequency shift of the power spectrum; the width of the autocorrelation
function increases from minimum to maximum, as a result of the large
decrease of power observed for the small granular features rather than
to a general increase of the scale of the granulation; the contrast of
the granulation decreases. The variation of the granulation over the
solar cycle, probably reflects a variation of the physical properties
at the top of the convection zone.
Title: Periodical patterns in major flare occurrence and their
relation to magnetically complex active regions
Authors: Temmer, M.; Veronig, A.; Rybak, J.; Brajsa, R.; Hanslmeier, A.
Bibcode: 2004cosp...35.1395T
Altcode: 2004cosp.meet.1395T
A periodical occurrence rate of solar major flares (observed in
hard X-rays) of about 24 days (synodic) was first reported by Bai
(1987) for the years 1980--1985. Its origin is still far from being
understood. Applying wavelet analyses for daily numbers of Hα flare
events covering almost four entire solar cycles (no. 19--22) reveals a
24-day period in each of the cycles studied. This can be established
primarily in the occurrence rate of major flares but is also seen
in subflares. Since large flares occur preferentially in association
with active regions of complex magnetic configuration a comparative
study of magnetically classified active regions, subdivided into
magnetically complex (i.e. including a γ and/or δ configuration)
and non-complex (α, β) was performed. A significant relation
between the appearance of the 24-day period in major Hα flares and
magnetically complex sunspot groups is found, whereas it cannot be
established for non-complex groups. From solar rotation studies based
on tracing sunspots practically no siderial rotation velocities as high
as 16 deg/day (which corresponds to a synodic period of ∼24 days)
are reported. Thus the cause of the 24-day period is very likely not
related to solar surface rotation. Alternatively it might be due to
periodical patterns in magnetic flux emergence which is an important
driver of flare eruptions. We test this hypothesis by investigating
synoptic maps of magnetograms (National Solar Observatory/Kitt Peak)
for selected time ranges in which the 24-day period is revealed for
both flares and magnetically complex active regions.
Title: The solar soft X-ray background flux and its relation to
flare occurrence
Authors: Veronig, Astrid M.; Temmer, Manuela; Hanslmeier, Arnold
Bibcode: 2004SoPh..219..125V
Altcode:
The soft X-ray background flux (XBF) based on GOES 1-8 Å measurements
for the period 1975-2003 is studied. There is strong evidence that
in the XBF the flare contribution is not eliminated but the XBF is
dominated by flare and post-flare emission of intense events. The
significant delay (∼ 2 years) of the peak of the X-ray background
flux with regard to sunspot numbers reported for cycle 21 recurs in
the present cycle 23. The relation between monthly XBF and sunspot
numbers can be well represented by a power law. For cycles 21 and 23
the derived fit values are the same within the uncertainties, whereas
the values for cycle 22 are significantly different. It is suggested
that the lag of the XBF in cycles 21 and 23 is a secondary effect
related to the substantial contribution of energetic flares which is
not fully subtracted out by the actual XBF definition.
Title: Comparative analysis of collisional and viscous damping of
MHD waves in partially ionized solar plasmas
Authors: Khodachenko, M. L.; Arber, T. D.; Hanslmeier, A.; Rucker,
H. O.
Bibcode: 2004HvaOB..28..115K
Altcode:
A comparative study of the efficiency of MHD wave damping in solar
plasmas due to collisional and viscous energy dissipation mechanisms
is presented here. The performed estimations allow to conclude which
damping mechanism is dominant in which regions. In general the correct
description of MHD wave damping requires the consideration of all
energy dissipation mechanisms via the inclusion of the appropriate
terms in the generalized Ohm's law, the momentum, energy and induction
equations. Specific forms of the generalized Ohm's Law and induction
equation are presented that are suitable for partially ionized regions
of the solar atmosphere.
Title: On rotational patterns of the solar magnetic field
Authors: Temmer, M.; Veronig, A.; Rybák, J.; Hanslmeier, A.
Bibcode: 2003ESASP.535..157T
Altcode: 2003iscs.symp..157T
Solar magnetic field variations (NSO/Kitt Peak data) through solar cycle
23 with respect to rotational modulations are analyzed. A comparative
study to solar cycles 21 and 22 is performed. The results are compared
to the rotational behavior of activity tracers like sunspots and solar
Hα flares. Periodical occurrences of flares often match the 27-day
solar rotation due to recurrent stable sunspot groups and complexes
of activity which likely produce more flare events than short-living
small sunspots. However, periods with strong deviations from the 27-day
period are obtained for higher energetic flares. The solar magnetic
field is found to vary on similar time scales, which suggests a close
relation to the occurrence of strong flare events.
Title: Solar cycle variations of the soft X-ray background flux and
its relation to flare occurrence
Authors: Veronig, A.; Temmer, M.; Hanslmeier, A.
Bibcode: 2003ESASP.535..259V
Altcode: 2003iscs.symp..259V
The X-ray background flux (XBF) based on GOES 1-8 Å measurements for
the period 1975-2000 is studied. We come to the conclusion that in the
XBF the flare contribution is not eliminated but the XBF is dominated
by flare and post-flare emission of intense events. Furthermore, we
suggest that the characteristic lag of the X-ray background flux with
regard to Sunspot Numbers reported for cycle 21 is a secondary effect
related to the substantial contribution of large flares to the XBF.
Title: New Hα instrumentation at the Kanzelhöhe Solar Observatory
Authors: Hanslmeier, A.; Otruba, W.; Poetzi, W.
Bibcode: 2003ESASP.535..729H
Altcode: 2003iscs.symp..729H
We present a short overview over new instrumentation developed at the
Kanzelhöhe Solar Observatory. The main advantages of this observatory
is a permanent staff which permits continuous solar monitoring. Due
to the high quality of data (especially Hα) and the incorporation of
the observatory into several international solar observing campaigns
new developments are done continuously. Observing in the wings of Hα
provides the possibility to study different phenomena such as waves
and oscillation propagation.
Title: Time series of high resolution photospheric spectra in a quiet
region of the sun. I. Analysis of global and spatial variations of
line parameters
Authors: Puschmann, K.; Vázquez, M.; Bonet, J. A.; Ruiz Cobo, B.;
Hanslmeier, A.
Bibcode: 2003A&A...408..363P
Altcode: 2012arXiv1205.1723P
A 50 min time series of one-dimensional slit-spectrograms, taken in
quiet sun at disk centre, observed at the German Vacuum Tower Telescope
(Observatorio del Teide), was used to study the global and spatial
variations of different line parameters. In order to determine the
vertical structure of the photosphere two lines with well separated
formation heights have been considered. The data have been filtered of
p-modes to isolate the pure convective phenomenon. From our studies
of global correlation coefficients and coherence and phase shift
analyses between the several line parameters, the following results
can be reported. The convective velocity pattern preserves structures
larger than 1.0 arcs to the highest layers of the photosphere (
~ 435 km). However, at these layers, in the intensity pattern only
structures larger than 2.0 arcs are still connected with those at the
continuum level although showing inverted brightness contrast. This
confirms an inversion of temperature that we have found at a height
of ~ 140 km. A possible evidence of gravity waves superimposed to
the convective motions is derived from the phase shift analysis. We
interprete the behaviour of the full width at half maximum and the
equivalent width as a function of the distance to the granular borders,
as a consequence of enhanced turbulence and/or strong velocity gradients
in the intergranular lanes.
Title: Does solar flare activity lag behind sunspot activity?
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2003SoPh..215..111T
Altcode:
Recently, Wheatland and Litvinenko (2001) have suggested that over the
solar cycle both the flaring rate and the magnetic free energy in the
corona lag behind the energy supply to the system. To test this model
result, we analyzed the evolution of solar flare occurrence with regard
to sunspot numbers (as well as sunspot areas), using Hα flare data
available for the period 1955-2002, and soft X-ray flare data (GOES
1-8 Å) for the period 1976-2002. For solar cycles 19, 21, and 23,
we find a characteristic time lag between flare activity and sunspot
activity in the range 10≲τ≲15 months, consistent with the model
predictions by Wheatland and Litvinenko (2001). The phenomenon turns
out to be more prominent for highly energetic flares. The investigation
of solar activity separately for the northern and southern hemisphere
allows us to exclude any bias due to overlapping effects from the
activity of both hemispheres and confirms the dynamic relevance of the
delay phenomenon. Yet, no characteristic time lag τ>0 is found for
solar cycles 20 and 22. The finding that in odd-numbered cycles flare
activity is statistically delayed with respect to sunspot activity,
while in even-numbered cycles it is not, suggests a connection to the
22-year magnetic cycle of the Sun. Further insight into the connection
to the 22-year magnetic cycle could possibly be gained when a 22-year
variation in the energy supply rate is taken into account in the
Wheatland and Litvinenko (2001) model. The existence of a 22-year
modulation in the energy supply rate is suggested by the empirical
Gnevyshev - Ohl rule, and might be caused by a relic solar field.
Title: Deriving effective sunspot temperatures from SOHO/VIRGO
irradiance measurements. A starspot modelling approach
Authors: Eker, Z.; Brandt, P. N.; Hanslmeier, A.; Otruba, W.;
Wehrli, C.
Bibcode: 2003A&A...404.1107E
Altcode:
A method is developed to obtain mean effective sunspot temperatures
from satellite irradiance deficits. Using a formalism derived from
a star spot modelling approach, this method only requires accurate
positions and areas of sunspots - but not intensities. The method
is applied to SOHO/VIRGO spectral solar irradiance (SSI) at 402,
500, and 862 nm as well as total solar irradiance (TSI) measured
during the period 16 July to 17 August 1996, the disk passage of
active region NOAA 7981. MDI full disk white-light images are used
to extract sunspot positions and areas. First, using the spot pixels,
which are identified on MDI images as Is < 0.92, we find
the mean effective temperature of NOAA 7981 to be =~ 300 K less than
the local photospheric temperature. Because the area is dominated by
penumbral pixels, the temperature is close to a value representing the
penumbra. Second, separating umbral and penumbral pixels, we obtain a
temperature difference of =~ 850 K for the umbra and of =~ 200 K for the
penumbra. Finally, if a 5% binning of the spot intensities is applied,
a temperature deficit of =~ 1000 K is found for the darkest regions
of the spot. Appendixes A, B are only available in electronic
form at http://www.edpsciences.org
Title: Full-disk magnetic oscillations in the solar photosphere
Authors: Moretti, P. F.; Cacciani, A.; Hanslmeier, A.; Messerotti,
M.; Otruba, W.; Warmuth, A.
Bibcode: 2003A&A...403..297M
Altcode:
Photospheric observations of the magnetic oscillations have been carried
out to research magneto-acoustic waves in spots. The coupling between
the magnetic field and the p-modes has been studied using reduced areas
on the solar disk, but a global scenario is still missing. Four hour
full-disk magnetograms (at 4 arcsec/pix spatial resolution) obtained in
the sodium D-lines were analysed pixel-by-pixel (locally) and using the
spherical harmonics decomposition (globally). Magnetic oscillations
were detected at different frequencies and identified on the solar
disk. The global properties of the magnetic oscillations, shown via
the l -nu diagrams, are for the first time presented and discussed.
Title: Evolution of Titan's atmosphere
Authors: Lammer, H.; Povoden, G.; Selsis, F.; Ribas, I.; Tehrany,
M. G.; Guinan, E. F.; Hanslmeier, A.; Bauer, S. J.
Bibcode: 2003EAEJA....12803L
Altcode:
We show that anomalies of heavy isotopes in Titan's atmosphere can be
explained by using observational data of the radiation and particle
environment of solar proxies. These observations indicate a larger solar
wind flux and high solar EUV radiation of the early Sun during the first
billion years are responsible for a fractionated atmospheric loss. For
studying the evolution of the thermal escape of Titan's atmosphere we
use a scaling law based on an approximate solution of the heat balance
equation in the exosphere. Further, isotope fractionation by non-thermal
atmospheric escape processes like dissociative recombination, impact
dissociation, atmospheric sputtering and ion pick-up processes. We
show that Titan lost an atmospheric mass We discuss also possible
chemical reactions of methane and other out-gassing substances due
to the high solar EUV fluxes powered thermospheric temperature 4 Gyr
ago. This could have lead to molecules of higher mass like ethane and
other organic compounds. The efficient production of such molecules
was reduced by the decrease of the solar activity resulting in a kind
of frozen state. At present only high energy processes like lightning
discharges may give similar reactions.
Title: Dynamics and turbulence of the chromospheric layers of a
flaring atmosphere
Authors: Brčeková, K.; Kučera, A.; Hanslmeier, A.; Rybák, J.;
Wöhl, H.
Bibcode: 2003AN....324..366B
Altcode:
No abstract at ADS
Title: Infrared photometry of a sunspot near the disk center
Authors: Stangl, S.; Sobotka, M.; Bonet, J. A.; Vázquez, M.;
Hanslmeier, A.
Bibcode: 2003AN....324..376S
Altcode:
A time series of broadband images of a sunspot near the disk center
was obtained simultaneously in two wavelength bands at 0.56 mu m and
1.55 mu m at the German VTT on June 17, 1998. We computed intensity
difference images of the best frame pairs which reveal information
about the facular distribution in the present field of view. Faculae
are found around pores, in the quiet granulation and as well around
the sunspot penumbra.
Title: Space Weather - Effects of radiation on manned space missions
Authors: Hanslmeier, A.
Bibcode: 2003HvaOB..27..159H
Altcode:
This contribution is a short review about the radiation environment
in space which is mainly modulated by the solar activity. Radiation
exposure limits are discussed and compared with measured radiation
dose that Astronauts were exposed during the Apollo missions. From
these data some conclusions about long term space missions such as
manned flight to Mars are made.
Title: Evolution of temperature in granule and intergranular space
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
Bibcode: 2003AN....324..349K
Altcode:
The temporal evolution of temperature in a dissolving granule and
in an adjacent intergranular space is presented. The semi-empirical
evolutionary models have been calculated using an inversion method
applied to 4-min time series of Stokes I spectral line profiles. The
models are presented in the form of the functional dependence of
temperature T(log tau_5 ,t) on optical depth tau_5 at 500 nm and time
t. The observed disappearance of the granule is accompanied with overall
cooling of the granular photosphere. Temperature changes greater than
100 K have been found in deeper (log tau_5 >=0) and upper layers
(log tau_5 <=-2) whereas the intermediate layers are thermally
stable. The intergranular space, which is 2 arcsec off the granule,
keeps the temperature structure of the layers from log tau_5 =0.5 to
log tau_5 =-2 without global evolutionary changes except short-term
and spatially confined heating. Finally, the significant temperature
changes in the upper layers (log tau_5 <=-2.5) observed during the
time interval of 4 min are found to be typical for the granular and
intergranular photosphere.
Title: Observational evidence for a shock event in the solar
granulation
Authors: Kučera, A.; Rybák, J.; Hanslmeier, A.; Wöhl, H.
Bibcode: 2003HvaOB..27...25K
Altcode:
High resolution spectra of Fe II 6456.39 Å line are used to investigate
a shock in the solar granulation. The changes of the main spectral
characteristics measured in the shock area are in a good agreement with
the characteristics predicted with theory. The analysis of the shock,
made in the past by several authors was extended in this work to the
analysis of a temporal development of the shock event. The 2 minutes
duration of a stable and declining phases of the event was studied. We
conclude that the observed shock belonged to the particular type of
shock generated as a consequence of the swaying motion of the magnetic
flux tube concentrated in the intergranular lane. Such type of shock
was proposed by numerical simulations made by Steiner et al. 1998.
Title: Models of a mean granular cell
Authors: Puschmann, K.; Ruiz Cobo, B.; Vázquez, M.; Bonet, J. A.;
Hanslmeier, A.
Bibcode: 2003AN....324..352P
Altcode:
From inversion of a time series of slit spectra, observed in a quiet
region of the solar photosphere, averaged models of a granular cell
have been obtained showing the stratification of physical quantities
versus optical depth and geometrical height. Furthermore a semi-empiric
dynamic model of a mean granular cell has been derived and the results
are presented.
Title: Flare waves revisited
Authors: Warmuth, A.; Vršnak, B.; Hanslmeier, A.
Bibcode: 2003HvaOB..27..139W
Altcode:
Recently, the flare wave phenomenon has come back into focus prompted
by the observation of coronal waves with the SOHO/EIT instrument
(EIT waves). It has been suggested that they represent the coronal
counterpart to the chromospheric Moreton waves, but this interpretation
has remained a matter of debate. In order to make inferences on the
physical nature of the phenomenon, 12 flare wave events are studied
using Hα, EUV, Helium I, SXR and radio data. The wavefronts in
the various spectral ranges are following very similar kinematical
curves, which suggests that they are caused by the same physical
disturbance. The characteristics of this disturbance -- deceleration,
perturbation profile broadening, and perturbation amplitude decrease
-- can be interpreted in terms of a freely propagating fast-mode MHD
shock which decays to an ordinary fast-mode wave. This scenario also
accounts for the associated metric type II radio bursts.
Title: Variation of granular evolution at meso-scales
Authors: Pötzi, W.; Brandt, P. N.; Hanslmeier, A.
Bibcode: 2003HvaOB..27...39P
Altcode:
An 8.5 h series of solar granulation images obtained at the Swedish
SVST (La Palma) was investigated for the divergence pattern and its
relation to granular evolution types. The velocities for the divergence
fields were calculated by local correlation techniques. Granular
evolution types were detected automatically by a granulation tracking
algorithm. We find a strong preference of fragmenting, merging, and
ring-like granules in regions of positive divergence, whereas fading
granules occur preferentially in regions of negative divergence.
Title: Rotational modulation of northern and southern activity tracers
Authors: Temmer, M.; Veronig, A.; Rybák, J.; Hanslmeier, A.
Bibcode: 2003HvaOB..27...59T
Altcode:
We study solar activity phenomena, Hα flares and sunspots, with respect
to their periodical occurrence related to the solar rotation. The
analysis is carried out separately for the northern and the southern
hemisphere. Furthermore, flare occurrences are studied with respect
to different importance classes, and the results are compared to
the predominant periods derived from Sunspot Numbers. Significant
asymmetries are obtained between the northern and southern activity for
both Sunspot Numbers and flare occurrences. Differences between Sunspot
Numbers and flares result particularly when only higher energetic
flares are considered. A 24-day period is found for large flare events
in both hemispheres which is not detected in Sunspot Numbers.
Title: Dynamics of Small Scale Motions in the Solar Photosphere
(With 4 Figures)
Authors: Hanslmeier, Arnold
Bibcode: 2003RvMA...16...55H
Altcode:
No abstract at ADS
Title: The particle and radiation environment of the early Sun
Authors: Tehrany, M. G.; Lammer, H.; Selsis, F.; Ribas, I.; Guinan,
E. F.; Hanslmeier, A.
Bibcode: 2002ESASP.506..209T
Altcode: 2002ESPM...10..209T; 2002svco.conf..209T
Multi-wavelength studies of solar-like G-type stars at several stages
of their main sequence evolution indicate that our early Sun must
have undergone a highly active phase in its particle and radiation
environment 3.5-4.5 Gyr ago. An overview of that problem can be
found e.g. in Guinan and Ribas (2002) and Hanslmeier (2002). Detailed
observations of such stars by the ROSAT and ASCA X-ray satellites show
that the X-ray luminosity may have been several hundred times higher
than today. We investigate in our study how these high X-ray fluxes
could be connected to the mass loss and particle outflow of these
stars and how such an enhanced particle and radiation environment has
influenced the evolution of planetary bodies in our solar system at
least up to 3.0 Gyr ago.
Title: Line intensities of chromospheric and photospheric spectra
of a flare
Authors: Brčeková, K.; Kučera, A.; Hanslmeier, A.; Rybák, J.;
Wöhl, H.
Bibcode: 2002ESASP.506..557B
Altcode: 2002ESPM...10..557B; 2002svco.conf..557B
In this work we present the intensities of spectral lines determined
from the time series of high resolution spectra obtained during
the relaxing phase of subflare. The spectra were taken in the core
of chromospheric Ca II K line and in two photospheric Fe I 522.5 nm
and Fe I 557.6 nm lines. It is shown, that the energy of the flaring
chromosphere slightly affects the underlying photospheric layers by
heating a small area right under the core of the subflare.
Title: Infrared photometric results of a sunspot
Authors: Stangl, S.; Hanslmeier, A.; Sobotka, M.; Bonet, J. A.;
Vázquez, M.
Bibcode: 2002ESASP.506..473S
Altcode: 2002ESPM...10..473S; 2002svco.conf..473S
We obtained simultaneously recorded time series of broadband
images of a sunspot close to the disk center at the German Vacuum
Tower Telescope, Tenerife, in two wavelength bands at 0.56 μm and
1.55 μm. Maps of brightness difference images Tb(1.55
μm) and Tb(0.56 μm) were computed for the best image
pairs. Furthermore, a scatter plot of the brightness temperatures
was made where five different magnetic and nonmagnetic regions -
quiet region (QR), faculae, pores, penumbra, and umbra - in the
field of view can be clearly distinguished. Pores as well as the
penumbra are surrounded by the facular regions consisting of several
single facular elements. However, facular regions are also found in
non-magnetic vicinity.
Title: Two-dimensional spectroscopic time series of solar granulation:
evolution of individual granules
Authors: Hanslmeier, Arnold; Kučera, Ales; Rybák, Jan; Wöhl,
Hubertus
Bibcode: 2002ESASP.506..633H
Altcode: 2002svco.conf..633H; 2002ESPM...10..633H
In this paper we investigate the dynamics of the solar granulation by
analyzing time series of 2-D spatially highly resolved spectrograms. The
high quality of the data permitted us to follow the evolution of
individual granular and intergranular areas. We used scans over the
solar surface in order to obtain a 2-D information. This has the
advantage of achieving high spectral and spatial resolution, however
one scan lasted for about 2 min.
Title: Catalogue of hemispheric sunspot numbers RN and
RS: 1975 - 2000
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2002ESASP.506..855T
Altcode: 2002svco.conf..855T; 2002ESPM...10..855T
Sunspot drawings are provided on a regular basis at the Kanzelhöhe
Solar Obseratory, Austria, and the derived relative sunspot numbers
are reported to the Sunspot Index Data Center in Brussels. From the
daily sunspot drawings, we derived the northern, Rn,
and southern, Rs, relative sunspot numbers for the
time span 1975-2000. In order to accord with the International
Sunspot Numbers Ri, the Rn and Rs
have been normalized to the Ri, which ensures that the
relation Rn+Rs = Ri is complied. For
validation, the derived Rn and Rs are compared
to the international northern and southern relative sunspot numbers,
which are available since 1992. The regression analysis performed for
the period 1992-2000 reveals good agreement with the International
hemispheric Sunspot Numbers. The monthly mean and the smoothed monthly
mean hemispheric Sunspot Numbers are compiled to a catalogue. In
addition, the daily hemispheric Sunspot Numbers are made available
via Internet.
Title: Solar cycle dependent variation of solar granulation
Authors: Hanslmeier, Arnold; Muller, Richard
Bibcode: 2002ESASP.506..843H
Altcode: 2002ESPM...10..843H; 2002svco.conf..843H
In this paper we study the problem of the variation of solar granulation
with the solar activity cycle. For that purpose a homogeneous dataset
consisting of photographically taken white light images was used. The
data were all obtained with the same instrument at the same observatory
(Pic du Midi). Since the variations are expected to be small, a careful
study was done to measure the influence of seeing, selection of a
specific area and evolution of the granular structure on the results.
Title: Cycle dependence of hemispheric activity
Authors: Temmer, M.; Veronig, A.; Rybák, J.; Hanslmeier, A.
Bibcode: 2002ESASP.506..859T
Altcode: 2002ESPM...10..859T; 2002svco.conf..859T
Data of daily hemispheric Sunspot Numbers are analyzed including the
time span 1975-2001. The study of north-south asymmetries concerning
solar activity and rotational behaviors is in particular relevant,
as it is related to the solar dynamo and the generation of magnetic
fields. As diagnostic tools we use wavelets and autocorrelation
functions in combination with statistical significance tests that are
applied separately to the northern and southern hemisphere. Pronounced
differences between the northern and southern rotational periods
are obtained. The northern hemisphere shows a rigid rotation of ~27
days which can be followed up to ~15 periods in the autocorrelation
function. The signal of the southern hemisphere is strongly attenuated
after 3 recurrences showing variable periods in the range ~26-28.5
days. The presence of these periods is not permanent during a cycle
suggesting activity pulses in each hemisphere. For the northern
hemisphere strong relations to the motions of deeper lying convective
structures building up long-living 'active zones' are suggested.
Title: Line-of-sight velocity in a semiempirical model of a
disappearing granule
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
Bibcode: 2002ESASP.506..443K
Altcode: 2002svco.conf..443K; 2002ESPM...10..443K
The behaviour of the line-of-sight velocity in the centre of a
disappearing granule is analyzed using an inversion method applied
to a time-series of spectra containing the Fe I 522.5 nm, 557.6
nm and 557.7 nm lines. The temporal evolution of the line-of-sight
velocity vLOS is presented in the form of the functional
dependence of vLOS(logτ5, t) on the optical
depth τ5 at 500 nm and time t. An oscillatory behaviour
is found in the velocity stratification with nearly constant phase
through the photosphere. The amplitude of variations increases from
logτ5 = -0.3 to logτ5 = -2.5 reaching a maximum
of ~1.2 km s-1. A zero velocity layer is detected in every
instantaneous model of the velocity stratification. The results suggest,
that the zero velocity may occur in a considerable range of the optical
depths from logτ5 ~ -2 to logτ5 ~ -3.5.
Title: The Neupert effect and the electron-beam-driven evaporation
model
Authors: Veronig, A.; Vršnak, B.; Dennis, B. R.; Temmer, M.;
Hanslmeier, A.; Magdalenić, J.
Bibcode: 2002ESASP.506..367V
Altcode: 2002svco.conf..367V; 2002ESPM...10..367V
Based on a sample of ~1100 solar flares observed simultaneously in
hard and soft X-rays, we performed a statistical analysis of the
Neupert effect. For a subset of ~500 events, supplementary Hα flare
data were considered. The timing behavior of >50% of the events
is consistent with the Neupert effect. A high correlation between
the soft X-ray peak flux and the hard X-ray fluence is obtained,
being indicative of electron-beam-driven evaporation. However, about
one fourth of the events (predominantly weak flares) reveal strong
deviations from the predicted timing, with a prolonged increase of
the thermal emission beyond the end of the hard X-rays. These findings
suggest that electron-beam-driven evaporation plays an important role
in solar flares. Yet, in a significant fraction of events there is also
evidence for an additional energy transport mechanism from the energy
release site other than electron beams, presumably thermal conduction.
Title: DARWIN: a nulling space interferometer
Authors: Kaltenegger, L.; Karlsson, A.; Hanslmeier, A.
Bibcode: 2002ESASP.518..519K
Altcode: 2002eab..conf..519K
No abstract at ADS
Title: Simulating the early solar radiation environment: X-ray
radiation damage experiments
Authors: Lammer, H.; Hickel, A.; Tehran, M. G.; Hanslmeier, A.; Ribas,
I.; Guinan, E. F.
Bibcode: 2002ESASP.518..469L
Altcode: 2002eab..conf..469L
No abstract at ADS
Title: Precise reduction of solar spectra obtained with large
CCD arrays
Authors: Wöhl, H.; Kučera, A.; Rybák, J.; Hanslmeier, A.
Bibcode: 2002A&A...394.1077W
Altcode:
A precise procedure suitable for the reduction of solar spectra
taken with large CCD arrays and the retrieval of correct spectral
characteristics is presented. Various effects, which one should take
into account, are considered and several improvements of the standard
reduction are introduced. A special flat-field procedure is suggested
for the reduction of spectra registered in different flat-field
conditions than those when the flat-field matrix was taken. The original
flat-field matrix is split into several components to eliminate the
influence of the drift of the spectrograph and temporal changes of
the flat-field conditions on the reduced spectrum. The importance
of every flat-field matrix component is tested and discussed and the
noise propagation through data reduction is analyzed. It is documented
that the errors of the basic spectral line characteristics, continuum
intensity, line centre intensity and full width at the half maxima
of the line have variations between 0.5% and 15% and the errors of
the line centre Doppler velocity and bisectors fluctuate by up to 200
m s-1, if derived from imprecise reductions, compared to
precise ones.
Title: An interpretation of the I-V phase background based on observed
plasma jets
Authors: Moretti, P. F.; Cacciani, A.; Hanslmeier, A.; Messerotti,
M.; Otruba, W.; Pddoto tzi, W.; Warmuth, A.
Bibcode: 2002A&A...395..293M
Altcode:
The presence of a solar background in the phase difference between the
intensity and velocity (I-V) p-mode oscillation signals recently has
been interpreted in terms of downflows due to convection (Skartlien
& Rast \cite{Skartlien00}) or due to chromospheric explosive
events (Moretti et al. \cite{Moretti01}a). In support of the latter,
we present I and V characteristics of impulsive brightenings observed
in the NaI D lines, show that these reproduce the frequency dependence
of the I-V modulation background, and show that explanations invoking
more frequently occurring phenomena such as seismic events are not
likely in low-l modulation data.
Title: Radiation and particle exposure of the Martian paleoatmosphere:
implications for the loss of water
Authors: Selsis, F.; Lammer, H.; Ribas, I.; Guinan, E. F.;
Lichtenegger, H. I. M.; Lara, L. -M.; Tehrany, M. G.; Hanslmeier, A.
Bibcode: 2002ESASP.518..553S
Altcode: 2002eab..conf..553S
No abstract at ADS
Title: Solar energetic phenomena and radiation hazards to biological
systems
Authors: Hanslmeier, Arnold
Bibcode: 2002ESASP.518..275H
Altcode: 2002eab..conf..275H
This paper will treat energetic processes on the Sun that are
relevant for biological systems in the near Earth space. During these
violent explosions hazardous short wavelength radiation is released
which is several orders of magnitudes higher than in the case for a
quiet Sun. With a delay of several hours to days also high energetic
particles hit the Earth. In the paper we described the main processes
on the Sun that are responsible for these eruptions and discuss the
possibilities to predict these. Several examples of dangerous quantities
of radiation and high energetic particles that occured during the past
are discussed as well as shielding mechanisms and the effect on living
organisms. Radiation exposures to manned space missions such as the
Apollo missions are further discussed.
Title: The Neupert effect in solar flares and implications for
coronal heating
Authors: Veronig, A.; Vrsnak, B.; Dennis, B. R.; Temmer, M.;
Hanslmeier, A.; Magdalenić, J.
Bibcode: 2002ESASP.505..599V
Altcode: 2002solm.conf..599V; 2002IAUCo.188..599V; 2002astro.ph..8089V
Based on simultaneous observations of solar flares in hard and soft
X-rays we studied several aspects of the Neupert effect. About half of
1114 analyzed events show a timing behavior consistent with the Neupert
effect. For these events, a high correlation between the soft X-ray
peak flux and the hard X-ray fluence is obtained, being indicative of
electron-beam-driven evaporation. However, for about one fourth of the
events there is strong evidence for an additional heating agent other
than electron beams. We discuss the relevance of these findings with
respect to Parker's idea of coronal heating by nanoflares.
Title: Flare waves observed in Helium I 10 830 Å. A link between
Hα Moreton and EIT waves
Authors: Vršnak, B.; Warmuth, A.; Brajša, R.; Hanslmeier, A.
Bibcode: 2002A&A...394..299V
Altcode:
Three traveling disturbances recorded in the absorption line of
Helium I at 10 830 Å, (He I), analogous to Hα Moreton waves,
are analyzed. The morphology and kinematics of the wavefronts are
described in detail. The He I wave appears as an expanding arc of
increased absorption roughly corresponding to the Hα disturbance,
although not as sharply defined. He I perturbations consist of a
relatively uniform diffuse component and a patchy one that appears as
enhanced absorption in He I mottles. It leads the Hα front by some
20 Mm and can be followed to considerably larger distances than in
Hα observations. Behind the front stationary areas of reduced He I
absorption develop, resembling EUV coronal dimming. The observed He I
as well as the Hα disturbances show a deceleration of the order of
100-1000 m s-2. Moreover, in the event where Hα , He I,
and EUV wavefronts are observed, all of them follow closely related
kinematical curves, indicating that they are a consequence of a common
disturbance. The analysis of spatial perturbation profiles indicates
that He I disturbances consist of a forerunner and a main dip, the
latter being cospatial with the Hα disturbance. The properties and
behavior of the wavefronts can be comprehended as a consequence of a
fast-mode MHD coronal shock whose front is weakly inclined to the solar
surface. The Hα disturbance and the main He I dip are a consequence
of the pressure jump in the corona behind the shock front. The He I
forerunner might be caused by thermal conduction from the oblique shock
segments ahead of the shock-chromosphere intersection, or by electron
beams accelerated in the quasi-perpendicular section of the shock.
Title: Temporal evolution of physical parameters in granule
Authors: Koza, J.; Kucera, A.; Hanslmeier, A.; Rybák, J.; Wöhl, H.
Bibcode: 2002ESASP.505..457K
Altcode: 2002solm.conf..457K; 2002IAUCo.188..457K
The temporal evolution of the physical parameters inside a granule
is presented. This is a step towards a more realistic 1D modeling
of the solar granulation, avoiding the temporal averaging used up
to now. The granulation is treated as a dynamical phenomenon and our
model has been calculated using an inversion method applied to time
series of spectra. The granular evolutionary model is presented in
the form of the functional dependence of temperature T(log τ, t) and
line-of-sight velocity vLOS(log τ, t) on optical depth τ
and time t. The observed disappearance of the granule is accompanied
with significant temperature changes greater than ~300K in deeper layers
(log τ5 > 0) and upper layers (log τ5 <
-2.5). In contrary, the layers from log τ5 ~= -0.5 to log
τ5 ~= -1.5 are more stable in the sense of temperature
variations, which are less than ~150K. An oscillatory behavior is
found in the line-of-sight velocity stratification from log τ5 ~= 0
upwards with increasing amplitude reaching up to ~= 2 km s-1
in upper layers.
Title: Dynamic coupling of the chromospheric and photospheric
flaring plasma
Authors: Brceková, K.; Kucera, A.; Hanslmeier, A.; Rybák, J.;
Wöhl, H.
Bibcode: 2002ESASP.505..357B
Altcode: 2002solm.conf..357B; 2002IAUCo.188..357B
The relaxing phase of the subflare observed in the core of chromospheric
Ca II K line and in two photospheric Fe I 522.5 nm and Fe I 557.6 nm
lines was investigated. The temporal evolution of asymmetry in Ca II
K line and the mean bisectors positions of the Fe I line profiles as
well as their correlations are presented. It is documented that the
chromospheric down-flow caused by the subflare strongly affects the
upper layers of the photosphere. As a consequence of relaxation of
the photospheric layers strong down-flows and up-flows were measured
at the end of the subflare relaxing phase.
Title: Hemispheric asymmetry of solar activity phenomena: north-south
excesses rotational periods and their links to the magnetic field
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2002ESASP.505..587T
Altcode: 2002solm.conf..587T; 2002IAUCo.188..587T
We present a cycle dependent analysis of various solar activity
phenomena, namely Sunspot Numbers and Hα flares, including the
time range 1975-2000. The data are studied on a statistical basis
with relation to their spatial distribution, significance of the
north-south asymmetry and rotational periods. For the considered time
span we obtain significant values of north-south asymmetries. For the
northern hemisphere the significant excesses are revealed during the
increasing and maximum phase of a solar cycle whereas a southern excess
dominates near the end of a cycle. Furthermore, we obtain differences
in rotational periods and activity gaps between both hemispheres that
suggest an independent evolution in hemispheric activity for these
indices. Hence, a weak interdependence of the magnetic field system
originating in the two hemispheres is suggested. Additionally we find
differences in the dominant rotational periods of photospheric and
chromospheric tracers.
Title: High-resolution CCD spectra reduction: temporal changes of
the flat-field compensation
Authors: Kučera, Aleš; Hanslmeier, Arnold; Rybák, Ján; Wohl,
Hubertus
Bibcode: 2002NCimC..25..703K
Altcode:
A new method suitable for long-time series of high-resolution CCD
spectra reduction is presented. The method allows to compensate the
temporal changes of the instrument conditions which leads to temporal
changes of the flat-field matrix. Sometimes it is impossible to make
the flat-field measurements during long simultaneous observations with
satellites (SOHO, TRACE). The method splits the flat-field matrix into
two components. The first one, connected with CCD camera is stable in
time and is correct for all spectra. The second one varies and reflects
temporal changes of the conditions in the spectrograph. Description
of the method and its application to real high-resolution CCD spectra
is presented and discussed.
Title: Investigation of the Neupert effect in solar
flares. I. Statistical properties and the evaporation model
Authors: Veronig, A.; Vršnak, B.; Dennis, B. R.; Temmer, M.;
Hanslmeier, A.; Magdalenić, J.
Bibcode: 2002A&A...392..699V
Altcode: 2002astro.ph..7217V
Based on a sample of 1114 flares observed simultaneously in hard X-rays
(HXR) by the BATSE instrument and in soft X-rays (SXR) by GOES, we
studied several aspects of the Neupert effect and its interpretation
in the frame of the electron-beam-driven evaporation model. In
particular, we investigated the time differences (Delta t) between
the maximum of the SXR emission and the end of the HXR emission,
which are expected to occur at almost the same time. Furthermore,
we performed a detailed analysis of the SXR peak flux - HXR fluence
relationship for the complete set of events, as well as separately for
subsets of events which are likely compatible/incompatible with the
timing expectations of the Neupert effect. The distribution of the time
differences reveals a pronounced peak at Delta t = 0. About half of the
events show a timing behavior which can be considered to be consistent
with the expectations from the Neupert effect. For these events, a high
correlation between the SXR peak flux and the HXR fluence is obtained,
indicative of electron-beam-driven evaporation. However, there is also
a significant fraction of flares (about one fourth), which show strong
deviations from Delta t = 0, with a prolonged increase of the SXR
emission distinctly beyond the end of the HXR emission. These results
suggest that electron-beam-driven evaporation plays an important role
in solar flares. Yet, in a significant fraction of events, there is
also clear evidence for the presence of an additional energy transport
mechanism other than nonthermal electron beams, where the relative
contribution is found to vary with the flare importance.
Title: Hemispheric Sunspot Numbers Rn and Rs:
Catalogue and N-S asymmetry analysis
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2002A&A...390..707T
Altcode: 2002astro.ph..8436T
Sunspot drawings are provided on a regular basis at the Kanzelhöhe
Solar Observatory, Austria, and the derived relative sunspot numbers
are reported to the Sunspot Index Data Center in Brussels. From the
daily sunspot drawings, we derived the northern, Rn,
and southern, Rs, relative sunspot numbers for the
time span 1975-2000. In order to accord with the International
Sunspot Numbers Ri, the Rn and Rs
have been normalized to the Ri, which ensures that the
relation Rn+Rs=Ri is fulfilled. For
validation, the derived Rn and Rs are compared
to the international northern and southern relative sunspot numbers,
which are available from 1992. The regression analysis performed for
the period 1992-2000 reveals good agreement with the International
hemispheric Sunspot Numbers. The monthly mean and the smoothed
monthly mean hemispheric Sunspot Numbers are compiled into a
catalogue. Based on the derived hemispheric Sunspot Numbers,
we study the significance of N-S asymmetries and the rotational
behavior separately for both hemispheres. We obtain that ~ 60% of the
monthly N-S asymmetries are significant at a 95% level, whereas the
relative contributions of the northern and southern hemisphere are
different for different cycles. From the analysis of power spectra
and autocorrelation functions, we derive a rigid rotation with ~
27 days for the northern hemisphere, which can be followed for up
to 15 periods. Contrary to that, the southern hemisphere reveals a
dominant period of ~ 28 days, whereas the autocorrelation is strongly
attenuated after 3 periods. These findings suggest that the activity
of the northern hemisphere is dominated by an active zone, whereas
the southern activity is mainly dominated by individual long-lived
sunspot groups. The catalogue is available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/390/707
Title: Relative timing of solar flares observed at different
wavelengths
Authors: Veronig, A.; Vršnak, B.; Temmer, M.; Hanslmeier, A.
Bibcode: 2002SoPh..208..297V
Altcode: 2002astro.ph..8088V
The timing of 503 solar flares observed simultaneously in hard X-rays,
soft X-rays and Hα is analyzed. We investigated the start and the peak
time differences in different wavelengths, as well as the differences
between the end of the hard X-ray emission and the maximum of the
soft X-ray and Hα emission. In more than 90% of the analyzed events,
a thermal pre-heating seen in soft X-rays is present prior to the
impulsive flare phase. On average, the soft X-ray emission starts 3 min
before the hard X-ray and the Hα emission. No correlation between the
duration of the pre-heating phase and the importance of the subsequent
flare is found. Furthermore, the duration of the pre-heating phase
does not differ for impulsive and gradual flares. For at least half of
the events, the end of the non-thermal emission coincides well with
the maximum of the thermal emission, consistent with the beam-driven
evaporation model. On the other hand, for ∼ 25% of the events there
is strong evidence for prolonged evaporation beyond the end of the
hard X-rays. For these events, the presence of an additional energy
transport mechanism, most probably thermal conduction, seems to play
an important role.
Title: The Sun and Space Weather
Authors: Hanslmeier, Arnold
Bibcode: 2002ASSL..277.....H
Altcode: 2002ssw..book.....H
What are the terrestrial effects of solar activity and the solar
activity cycle? The modern term used for solar terrestrial relations
is `Space Weather'. This term describes all external effects on the
space environment of the Earth and the Earth's atmosphere. The main
driver for space weather is our Sun. Explosive events on the Sun that
are modulated by the solar activity cycle lead to enhanced particle
emission and short wavelength radiation. This affects satellites: for
example surface charging and enhanced drag forces on satellites in
low Earth orbit can cause satellite crashes etc. Enhanced radiation
also poses a problem for astronauts, especially for extravehicular
activities. Another source of space weather effects is space debris
and micrometeoroids. Since the Sun is the main source of space weather
effects, the first part of the book is devoted to a general introduction
to the physics of the Sun. A better understanding of the phenomena
underlying solar activity is also important for prediction of solar
outbursts and thus for establishing alert systems for space missions
and telecommunication systems. The book contains the following topics:
* possible influence of the Sun on the Earth's climate; * the effects
of radiation on humans in space and the expected radiation dose from
various solar events; * disturbances of the Earth's ionosphere and the
implications of radio communication at different wavelength ranges;
* possible hazardous asteroids and meteoroids and their detection;
and * space debris and special shielding of spacecraft. In the cited
literature the reader can find more detailed information about the
topics. This book provides an introduction and overview of modern
solar-terrestrial physics for students as well as for researchers
in the field of astrophysics, solar physics, geophysics, and climate
research. Link: http://www.wkap.nl/prod/b/1-4020-0684-5
Title: VizieR Online Data Catalog: Hemispheric Sunspot Numbers
1975-2000 (Temmer+, 2002)
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.
Bibcode: 2002yCat..33900707T
Altcode:
Hemispheric sunspot numbers including the time span from 1975-2000 are
presented. The Sunspot Numbers are calculated from sunspot drawings
made at the Kanzelhoehe Solar Observatory (KSO), Austria. The counted
northern and southern Sunspot Numbers are normalized and multiplied
with the International Sunspot Numbers taken from SIDC for matching
days in order to provide the data within an international usage. Days
without observation by KSO (about 27 percent) were reconstructed
applying a linear interpolation method. As validation of the data,
regression methods and a cross-correlation analysis are made with
hemispheric Sunspot Numbers from SIDC for the available time span
1992-2000 obtaining very good agreements. The results are given in
monthly mean and smoothed monthly mean Sunspot Numbers. Based on this
data set an analysis concerning the North-South asymmetry is made in
the paper. (1 data file).
Title: Book Review: The Dynamic sun / Kluwer, 2001
Authors: Hanslmeier, A.; Messerotti, M.; Veronig, A.
Bibcode: 2002Obs...122..115H
Altcode:
No abstract at ADS
Title: Moreton waves and their relation with EIT waves
Authors: Warmuth, Alexander; Vršnak, Bojan; Aurass, Henry; Hanslmeier,
Arnold
Bibcode: 2002ESASP.477..195W
Altcode: 2002scsw.conf..195W
Moreton waves, observed in Hα, and the recently discovered coronal
transients known as "EIT waves" have remained fairly poorly understood
phenomena. In particular, the issues of their mutual association and of
the nature of their driver are not resolved. We discuss seven Moreton
waves observed in Hα and derive their basic characteristics. Four of
these events were observed simultaneously in Hα and EUV. A deceleration
of the disturbances is found in all cases. In the 2 May 1998 event,
the cospatiality of Moreton and EIT wave fronts is established and
a detailed analysis of the evolution of the Hα wave, its kinematics
and perturbation profile is carried out. The results - deceleration,
broadening, and decrease of intensity of the profiles - favor the
fast-mode shock ("blast wave") scenario over the CME-associated magnetic
field evolution hypothesis.
Title: Simultaneous Hα and sodium observations at the Kanzelhöhe
Solar Observatory
Authors: Moretti, Pier F.; Andretta, V.; Cacciani, A.; Hanslmeier,
A.; Messerotti, M.; Otruba, W.; Warmuth, A.
Bibcode: 2002ESASP.477..147M
Altcode: 2002scsw.conf..147M
At the Kanzelhöhe Solar Observatory, Hα images are currently
obtained simultaneously with sets of intensity, velocity and
longitudinal magnetic images in the sodium D lines. Many flares
have been detected. The preliminary results of the analysis suggest
the events to occur at heights in the solar atmosphere below 1100
km, where the canopy magnetic lines stressed by the photospheric
motions can reconnect. The penetration of the downflowing plasma
jets is investigated in order to justify the solar background in the
photospheric intensity-velocity phase spectrum.
Title: Soft X-ray flares for the period 1975-2000
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.; Otruba, W.;
Messerotti, M.
Bibcode: 2002ESASP.477..175T
Altcode: 2002scsw.conf..175T
Statistical aspects of solar soft X-ray (SXR) flares for the period
September 1975 to December 2000 are investigated. In particular,
we analyzed the spatial distribution of SXR flares with regard to
the solar hemispheres, i.e. N-S and E-W asymmetries, as well as the
occurrence of SXR flares in the course of the solar cycle. We obtain
that the occurrence rate of SXR flares is delayed in relation to the
Sunspot Numbers which can be interpreted as an interaction between
the northern and southern hemisphere activity.
Title: Temporal characteristics of solar soft X-ray and Hα flares
Authors: Veronig, A.; Temmer, M.; Hanslmeier, A.; Messerotti, M.;
Otruba, W.; Moretti, P. F.
Bibcode: 2002ESASP.477..187V
Altcode: 2002scsw.conf..187V
Temporal aspects of solar soft X-ray and Hα flares for the period
1997-2000 are investigated. For the considered time span about 8400
SXR and 11400 Hα flares are reported in the SGD. Related flares
observed in Hα as well as in SXR are identified amounting to about
2100 events. Correlations among corresponding SXR and Hα events are
analyzed and their relative timing is investigated. From the timing
analysis we infer that for most of the events (84%) the start of the
Hα emission is delayed with respect to the SXR emission. On average,
the Hα flare starts 3 minutes after the SXR flare. The peaks occur
preferentially simultaneously with a slight tendency that the Hα peak
precedes the SXR peak.
Title: Temporal aspects and frequency distributions of solar soft
X-ray flares
Authors: Veronig, A.; Temmer, M.; Hanslmeier, A.; Otruba, W.;
Messerotti, M.
Bibcode: 2002A&A...382.1070V
Altcode: 2002astro.ph..7234V
A statistical analysis of almost 50 000 soft X-ray (SXR) flares observed
by GOES during the period 1976-2000 is presented. On the basis of
this extensive data set, statistics on temporal properties of soft
X-ray flares, such as duration, rise and decay times with regard to
the SXR flare classes is presented. Correlations among distinct flare
parameters, i.e. SXR peak flux, fluence and characteristic times,
and frequency distributions of flare occurrence as function of the
peak flux, the fluence and the duration are derived. We discuss the
results of the analysis with respect to statistical flare models, the
idea of coronal heating by nanoflares, and elaborate on implications
of the obtained results on the Neupert effect in solar flares.
Title: Cork Map and Divergence Map of an Active Region
Authors: Stangl, S.; Hanslmeier, A.
Bibcode: 2002HvaOB..26....1S
Altcode:
The horizontal motion and the velocity field in the solar photosphere
in the presence of a sunspot and associated pores is studied by means
of a local correlation tracking algorithm (LCT) of a 40 minute time
series of broadband images. The observation took place on June, 17
1998 at the VTT, Tenerife and the wavelength band used was centered
at the non-magnetic Fe I line at 5576 Å. A cork map and a divergence
map are presented which give information about the horizontal motion
and sources and sinks of this plasma motion.
Title: Proceedings, annual meeting of Austrian astronomers, 3-4 May
2002, Graz
Authors: Hanslmeier, A.
Bibcode: 2002HvaOB..26.....H
Altcode:
No abstract at ADS
Title: Fine structure and dynamics in a light bridge inside a
solar pore
Authors: Hirzberger, J.; Bonet, J. A.; Sobotka, M.; Vázquez, M.;
Hanslmeier, A.
Bibcode: 2002A&A...383..275H
Altcode:
A photometric analysis of the sub-structure of a granular light
bridge in a large solar pore is performed. The data consist of a
66 min time series of white light images (lambda = 5425 Å,+/- 50
Å) of an active region NOAA 7886 obtained at the Swedish Vacuum
Solar Telescope on La Palma, Canary Islands. The light bridge can
be resolved into an assembly of small grains embedded in a diffuse
background with an intensity of about 85% of the mean photospheric
intensity (Iphot). Following the temporal evolution of these
sub-structures in their irregular motions inside the light bridge,
proper motions with velocities up to 1.5 km s-1 can be
detected. Their lifetime distribution shows a maximum at 5 min and a
second peak at approximately 20 min. The origin and the decay of these
sub-structures is very similar to those of granules, i.e. fragmentation,
merging and spontaneous origination from, and dissolution into, the
background can be observed. Some of them are able to escape from the
light bridge into the umbra where they cannot be distinguished from
adjacent umbral dots. Generally, this study presents evidence that
the observed phenomenon represents convective motions.
Title: Frequency Distributions of solar Flares
Authors: Veronig, A.; Temmer, M.; Hanslmeier, A.
Bibcode: 2002HvaOB..26....7V
Altcode:
Flare frequency distributions as function of the soft X-ray peak flux
and fluence are investigated. We analyse GOES 1--8 Å data for the
period 1986--2000. The results are discussed with respect to avalanche
flare models and the hypothesis of coronal heating by nanoflares.
Title: Erosion and Sublimation Effects On Mercury`s Surface: Past
and Present
Authors: Tehrany, M. G.; Lammer, H.; Hanslmeier, A.; Ribas, I.;
Guinan, E. F.; Kolb, C.
Bibcode: 2002EGSGA..27.1903T
Altcode:
Ground-based observations of heavy constituents like Na, K and O
in Mercury`s present exosphere indicate a strong exosphere-surface
interaction related to the par- ticle and radiation environment of the
close Sun. Recent studies of isotope anomalies in planetary atmospheres
and meteorites suggest that our early Sun underwent a highly active
phase after its origin that included continuous flare events and had
a particle and radiation environment several hundred times stronger
than today. Since Mercury is the closest planet to the Sun, its
surface was more heavily exposed to the enhanced solar wind particle
and radiation fluxes than those of any of the other Solar System bod-
ies. To evaluate how such effects may have influenced Mercury`s surface,
we study its surface erosion and sublimation during the planet history
by using solar analogue G-type stars. The astrophysical parameters
of these Sun-like stars were studied within the broader "Sun in Time"
program. We use for our study three models for the young Sun: one model
with an initial solar mass of 2, where the mass loss rate and luminos-
ity decreases exponentially with e-folding times of a few 10E8 years;
a second model, which can be compared to solar analogue observations,
including large flare events during the first hundred million years; and
a third model, which is the standard model. The results of the analysis
of these three models are used to estimate and compare the sputter
erosion and sublimation rates of Mercury`s surface during its history.
Title: JOSO national report 1999-2001 - Austria
Authors: Hanslmeier, A.
Bibcode: 2002joso.book...22H
Altcode:
We give the report of the activities of Austria in the period 1999 to
end of 2001.
Title: Einführung in Astronomie und Astrophysik
Authors: Hanslmeier, Arnold
Bibcode: 2002eaua.book.....H
Altcode:
Astronomie und Astrophysik sind älteste und modernste Wissenschaft
in einem - sie vereinigen lange Beobachtungstradition und zugleich
aktuellste Theorie und Technik. In 15 Kapiteln vermittelt dieses
Einführungslehrbuch für Physik-und Astronomiestudierende das
Grundwissen über theoretische und praktische Methoden, Fakten über
die vielfältigen Objekte zwischen Erde und dem Rand des Universums
sowie Anwendungen für die beobachtende oder theoretische Forschung bis
hin zur Computerastronomie. Contents: 1) Sphärische Astronomie. 2)
Geschichte der Astronomie. 3) Himmelsmechanik. 4) Astronomische
Instrumente. 5) Physik der Körper des Sonnensystems. 6) Die Sonne. 7)
Zustandsgrößen der Sterne. 8) Sternatmosphären. 9) Sternaufbau. 10)
Sternentwicklung. 11) Interstellare Materie. 12) Die Galaxis 13)
Extragalaktische Systeme. 14) Kosmologie. 15) Anhang.
Title: Earthshine: A Proposal To Build An Automatic System For
Observing Terrestrial Albedo.
Authors: Thejll, P.; Ulla, A.; Hanslmeier, A.; Chou, D. -Y.; Goode,
P.; Vazquez, M.; Belmonte, J. A.
Bibcode: 2002EGSGA..27.4058T
Altcode:
Terrestrial albedo data are important for climate model studies
because of the impor- tance albedo has on the net radiation budget
of the Earth. Direct measurements of the albedo are not common, and
there is no dataset with global coverage that offers an alternative
to data from satellite measurements. The satellite data, however, are
often from weather satellites that were not specifically designed to
guarantee long-term sen- sitivity stability in the imaging data, and
thus in the albedo data that can be derived from these. Therefore,
absolute calibration of terrestrial satellite albedo data is not
possible. The Earth reflects light onto the Moon proportional to
the albedo, and it is possible to measure from the Earth the so called
'earthshine' on the Moon, so accurately that a cost-effective system
for mean-terrestrial albedo monitoring can be built on the basis of
small robotic telescopes. We present a system for observation and
data-handling, that could provide data for albedo studies. The system
is intrinsically stable and would be able to produce data of long-term
stability so that questions related to the drift in satellite data
could be investigated in the future.
Title: Evolution of Two EIT/Hα Moreton Waves
Authors: Warmuth, A.; Vršnak, B.; Aurass, H.; Hanslmeier, A.
Bibcode: 2001ApJ...560L.105W
Altcode:
Since the discovery of EIT waves, questions have remained about
the driver of these disturbances and their association with the
chromospheric Moreton waves. In order to resolve some of these issues,
two flare-associated transient events (1997 November 3 and 1998 May 2)
observed simultaneously in Hα and EIT are analyzed. The cospatiality
of Moreton and EIT wave fronts is established, and a deceleration of
the disturbances is found in both events. In the case of 1998 May 2, a
detailed analysis of the evolution of the Moreton wave, its kinematics,
and perturbation profile is carried out. The results-deceleration,
broadening, and decrease of intensity of the profiles-favor the
fast-mode shock (``blast wave'') scenario over the coronal mass
ejection-associated magnetic field evolution hypothesis.
Title: Statistical analysis of solar Hα flares
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.; Otruba, W.;
Messerotti, M.
Bibcode: 2001A&A...375.1049T
Altcode: 2002astro.ph..7239T
A statistical analysis of a large data set of Hα flares comprising
almost 100 000 single events that occurred during the period
January 1975 to December 1999 is presented. We analyzed the flares
evolution steps, i.e. duration, rise times, decay times and event
asymmetries. Moreover, these parameters characterizing the temporal
behavior of flares, as well as the spatial distribution on the solar
disk, i.e. N-S and E-W asymmetries, are analyzed in terms of their
dependency on the solar cycle. The main results are: 1) The duration,
rise and decay times increase with increasing importance class. The
increase is more pronounced for the decay times than for the rise
times. The same relation is valid with regard to the brightness
classes but in a weaker manner. 2) The event asymmetry indices,
which characterize the proportion of the decay to the rise time of
an event, are predominantly positive (~90%). For about 50% of the
events the decay time is even more than 4 times as long as the rise
time. 3) The event asymmetries increase with the importance class. 4)
The flare duration and decay times vary in phase with the solar cycle;
the rise times do not. 5) The event asymmetries do not reveal a distinct
correlation with the solar cycle. However, they drop during times of
solar minima, which can be explained by the shorter decay times found
during minimum activity. 6) There exists a significant N-S asymmetry
over longer periods, and the dominance of one hemisphere over the
other can persist for more than one cycle. 7) For certain cycles there
may be evidence that the N-S asymmetry evolves with the solar cycle,
but in general this is not the case. 8) There exists a slight but
significant E-W asymmetry with a prolonged eastern excess.
Title: The source of the solar oscillations: Convective or magnetic?
Authors: Moretti, P. F.; Cacciani, A.; Hanslmeier, A.; Messerotti,
M.; Oliviero, M.; Otruba, W.; Severino, G.; Warmuth, A.
Bibcode: 2001A&A...372.1038M
Altcode:
The origin of solar oscillations has not yet been clearly
determined. The downflows due to convective rapid cooling at the surface
have been invoked as a possible source. In this paper we investigate
the properties of the source as inferred from the local analysis of
the intensity-velocity phase differences. The same spatial and temporal
characteristics of other observed events and their correlation with the
Hα bright points suggests downward plasma jets related to explosive
chromospheric evaporation to be another possible candidate.
Title: Observations of NOAA 8210 Using MOF and DHC of Kanzelhöhe
Solar Observatory
Authors: Warmuth, A.; Hanslmeier, A.; Messerotti, M.; Cacciani, A.;
Moretti, P. F.; Otruba, W.
Bibcode: 2001ASSL..259..259W
Altcode: 2001dysu.conf..259W
Two new instruments have recently been introduced at Kanzelhöhe
Solar Observatory: the Magneto-Optical Filter (MOF), a compact imaging
Doppler-magnetograph and the Digital Hα Camera (DHC). In 1998, these
instruments were first used in high-cadence mode to support a SOHO/UVCS
campaign. During this campaign, NOAA 8210 rotated onto the disk, evolved
rapidly and produced several major flares. Furthermore, we point out
the perspectives for our planned Flare Monitoring and Alerting System,
since the two new instruments are crucial components for this program.
Title: The Location of Solar Oscillations in the Photosphere
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2001ASSL..259..267H
Altcode: 2001dysu.conf..267H
Applying a correlation analysis to time series of granulation it has
been shown that due to the influence of enhanced turbulent motions
near the downflow regions in the intergranular lanes the turbulent
motions predominate.
Title: Coincidences between Magnetic Oscillations and Hα Bright
Points
Authors: Moretti, P. F.; Cacciani, A.; Messerotti, M.; Hanslmeier,
A.; Otruba, W.
Bibcode: 2001ASSL..259..243M
Altcode: 2001dysu.conf..243M
The origin of the solar oscillations and the interaction with the
magnetic field are usually considered as two distinct problems. Four
hours of 1 minute cadence full-disk dopplergrams, longitudinal
magnetograms and intensity images, taken in the sodium D lines at
Kanzelhöhe Solar Observatory, have been analyzed to investigate
possible spatial correlations between the magnetic oscillations and
the Hα bright points. The phase relation between the velocity and
intensity images is used to enhance the magnetic signatures in the
low spatial resolution images. The coincidences between the magnetic
oscillations locations and the Hα bright points suggest to investigate
the magnetic reconnections as a possible source of solar oscillations.
Title: The Dynamic Sun
Authors: Hanslmeier, Arnold; Messerotti, Mauro; Veronig, Astrid
Bibcode: 2001ASSL..259.....H
Altcode: 2001dysu.conf.....H
This book contains the proceedings of the Summerschool and Workshop
"The Dynamic Sun" held from August 30th to September 10th, 1999, at
the Solar Observatory Kanzelhoehe, which belongs to the Institute
of Geophysics, Astrophysics and Meteorology of the University of
Graz, Austria. This type of conference was the second one held at
Kanzelhoehe and was again very successful in bringing together experts
from specialized topics in solar physics and young scientists and
students from different countries. Seven series of lectures were given
by invited lecturers, experts in the relevant fields and twenty-seven
constributions were presented at the workshop by the participants. The
scientific topics addressed covered a wide range of subjects, from solar
magnetohydrodynamics to the physics of the outer solar atmosphere and
from a detailed description of the SOHO mission to space weather.
Title: Comparison of Local and Global Fractal Dimension Determination
Methods
Authors: Veronig, A.; Hanslmeier, A.; Messerotti, M.
Bibcode: 2001ASSL..259..315V
Altcode: 2001dysu.conf..315V
Local and global methods for the determination of fractal dimensions are
applied to astrophysical time series. The analysis reveals that local
dimension methods are better suitable for such kind of time series,
which are non-stationary and which represent real-world systems. It
is shown that local dimension methods can provide physical insights
into the system even in cases in which pure determinism cannot be
established.
Title: High Resolution Observations of a Photospheric Light Bridge
Authors: Hirzberger, J.; Hanslmeier, A.; Bonet, J. A.; Vázquez, M.
Bibcode: 2001ASSL..259..271H
Altcode: 2001dysu.conf..271H
We analyzed a 66 min time series of spatially highly resolved white
light images to study the dynamics of photospheric light bridges
which we assumed to be a restoration of the quiet surface inside
sunspots. Similar decaying mechanisms were found as for normal
photospheric dynamics for granulation.
Title: Modeling VIRGO Spectral and Bolometric Irradiances with
MDI Data
Authors: Steinegger, M.; Hanslmeier, A.; Otruba, W.; Brandt, P. N.;
Eker, Z.; Wehrli, C.; Finsterle, W.
Bibcode: 2001ASSL..259..283S
Altcode: 2001dysu.conf..283S
The last solar activity minimum in 1996 was characterized by
several periods without any sunspots or faculae visible on the solar
disk. Between these extremely quiet intervals, from time to time
a single active region emerged and developed. The passage of these
individual active regions across the visible solar hemisphere was
accompanied by a pronounced variation in the solar irradiance as
observed by VIRGO onboard SOHO. Making use of photometric full-disk
observations of the Sun obtained by MDI we try to reconstruct the
temporal behaviour of the three spectral and the total irradiance
channels measured by VIRGO by applying starspot modeling techniques. In
this paper we mainly discuss possible error sources.
Title: Deconvolutions and Power Spectra of Solar Granulation
Authors: Pikalov, K. N.; Hanslmeier, A.
Bibcode: 2001ASSL..259..219P
Altcode: 2001dysu.conf..219P
An accurate estimation of power spectra from 2-D white light images
suggests the solving of an ill-posed problem (deconvolution) in
order to restore high-frequency spectra components depressed by the
optical system of telescope and atmosphere. In this paper we address
the question what are the influences of deconvolution methods to
the features of restored power spectra. Two kinds of deconvolution
techniques have been used in order to make this question clear.
Title: Solar Activity Monitoring and Flare Alerting at Kanzelhöhe
Solar Observatory
Authors: Steinegger, M.; Veronig, A.; Hanslmeier, A.; Messerotti,
M.; Otruba, W.
Bibcode: 2001ASSL..259..227S
Altcode: 2001dysu.conf..227S
At the Kanzelhöhe Solar Observatory a solar activity monitoring and
flare alerting system is under development, which will be based on
the parametrization of solar flaring activity using photometric and
magnetic full-disk images of the Sun obtained simultaneously with high
time cadence. This system will rely on Artificial Neural Networks
for pattern recognition, image segmentation, parameterization, and
forecasting. In particular, relevant activity indices and indicators
will be derived to be used as reliable precursors for flaring activity.
Title: Computational Methods concerning the Solar Granulation
Authors: Pötzi, W.; Hanslmeier, A.; Brandt, P. N.
Bibcode: 2001ASSL..259..223P
Altcode: 2001dysu.conf..223P
In this paper an overview is given concerning the automatic detection
of granules in long time series and the derivation of characteristic
parameters.
Title: The new global high-resolution Hα network: preliminary
results on the chromospheric differential rotation
Authors: Steinegger, M.; Denker, C.; Goode, P. R.; Marquette, W. H.;
Varsik, J.; Wang, H.; Otruba, W.; Freislich, H.; Hanslmeier, A.; Luo,
G.; Chen, D.; Zhang, Q.
Bibcode: 2001ESASP.464..315S
Altcode: 2001soho...10..315S
A new global network for high-resolution Hα full-disk observations of
the sun has been established at the Big Bear Solar Observatory (U.S.A.),
the Kanzelhöhe Solar Observatory (Austria), and the Yunnan Astronomical
Observatory (China). Each of the three stations have a 2K×2K pixel CCD
detector available to monitor the sun with a spatial resolution of 1
arcsec per pixel and a cadence of at least 1 image per minute. Having
high-cadence data from three observing stations available enables us to
accurately track solar rotation rates and meridional motions by local
correlation (LCT) and feature tracking techniques. This includes, e.g.,
tracking over several days the motions around active regions. After
an overview of the new Hα network and its scientific objectives, we
present and discuss the first preliminary results of the determination
of the chromospheric differential rotation by LCT from a high-cadence
time-series of Hα full-disk images. The obtained equatorial rotation
rate of 13.3044 deg/day (2.6876 μrad/s) agrees well with the values
obtained by other authors. Finally, we briefly outline our future
plans for the continuation of this work.
Title: A Neural Network Approach to Solar Flare Alerting (CD-ROM
Directory: contribs/steinegg)
Authors: Steinegger, M.; Veronig, A.; Hanslmeier, A.; Messerotti,
M.; Otruba, W.
Bibcode: 2001ASPC..223.1165S
Altcode: 2001csss...11.1165S
No abstract at ADS
Title: A Lattice Gas Model for Twodimensional Boussinesq Convection
Authors: Schaffenberger, W.; Hanslmeier, A.; Messerotti, M.
Bibcode: 2001HvaOB..25...49S
Altcode:
In this paper, we present a 2-D model for simulating the convection of
an incompressible fluid between two walls of different temperatures. In
particular, a bidimensional cellular automaton (CA) was developed to
study the evolution of a discrete particle system, which represents a
modified Frisch-Hasslacher-Pomeau (FHP) lattice gas. The derivation of
the model equations and some relevant diagnostics, such as the Rayleigh,
Prandtl and Nusselt numbers, are briefly outlined. The diagnostics
computed for test runs indicate the consistency of the model as well
as the preliminary simulation performed with a CA.
Title: Radio Pulsations in the m-dm Band: Case Studies
Authors: Messerotti, M.; Zlobec, P.; Veronig, A.; Hanslmeier, A.
Bibcode: 2001pre5.conf..471M
Altcode:
Radio pulsations are observed during several type IV bursts in the
metric and decimetric band. A great variety of morphological and
evolutionary features characterizes such events. Radio pulsations
should carry information about the magnetic topology of the corona, the
local particle density distribution, and about magnetic reconnection
and particle acceleration processes at or near the radio source; the
polarization degree should bring important clues about emission mode
and propagation effects in the source and outside it. In this frame,
we selected a representative set of radio pulsations, observed with high
time resolution by the Trieste Solar Radio System in the meter-decimeter
(m-dm) wavelength band, and performed a detailed morphological and
spectral analysis to identify possible similarities in the descriptors
relevant to different categories of events. Both classical and nonlinear
techniques were applied in the attempt to investigate more deeply the
physical nature of the emission process. The obtained results give
the trend how the ratio magnetic field - characteristic dimension of
the source increases at higher observing frequencies. A sudden rise of
this ratio across the m-dm range was derived, indicating a different
nature of pulsations in the two ranges.
Title: Dynamics of the Upper Photosphere: Coherence and Phase Analysis
(CD-ROM Directory: contribs/hanslmei)
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2001ASPC..223..669H
Altcode: 2001csss...11..669H
No abstract at ADS
Title: Statistical Study of Solar Flares Observed in Soft X-Ray,
Hard X-Ray and Hα Emission
Authors: Veronig, A.; Vršnak, B.; Temmer, M.; Magdalenić, J.;
Hanslmeier, A.
Bibcode: 2001HvaOB..25...39V
Altcode:
Correlations among statistical properties of solar flares observed
in soft X-rays, hard X-rays and Hα are studied. We investigate
corresponding HXR flares measured by BATSE, SXR flares observed by GOES
and Hα flares reported in the SGD for the period 1997--2000. Distinct
correlations are found among the SXR peak flux and Hα area, as well
as between the SXR peak flux and HXR fluence. This can be comprehended
in the frame of the chromospheric evaporation model of flares.
Title: Infrared Photometry of Solar Photospheric Structures. I. Active
Regions at the Center of the Disk
Authors: Sobotka, M.; Vázquez, M.; Sánchez Cuberes, M.; Bonet,
J. A.; Hanslmeier, A.
Bibcode: 2000ApJ...544.1155S
Altcode:
Simultaneous time series of broadband images of two active regions
close to the disk center were acquired at the Swedish Vacuum
Solar Telescope, La Palma, in the infrared bands at 1.55 and 0.80
μm, corresponding to the minimum and maximum continuum opacities,
respectively. Dark faculae are detected in images obtained as weighted
intensity differences between both wavelength bands. Maps of brightness
temperatures Tb (1.55 μm) and Tb (0.80 μm)
were computed for the best pairs of images. In the scatter plots
Tb (1.55) versus Tb (0.80), the elements of
quiet regions can be clearly distinguished from those of faculae and
pores, while the transition between faculae and pores is smooth. The
temperature difference Tb(1.55)-Tb(0.80) in
faculae is lower than that in the quiet photosphere but increases with
decreasing Tb and is higher inside pores. Most of the pores
are surrounded by ringlike regions of low temperature difference. The
minimum intensity of pores at both wavelengths decreases with increasing
diameter. Maps of horizontal motions of dark faculae and pores were
derived from time series of intensity-difference images, using the
local correlation tracking technique. Velocities corresponding to
large-scale separation of polarities, an emergence of magnetic flux,
twist and contraction related to a pore formation, shear motions,
and a twist in dark faculae were measured.
Title: Correlative relationships in an inhomogeneous solar atmosphere
Authors: Gadun, A. S.; Hanslmeier, A.; Kučera, A.; Rybák, J.;
Wöhl, H.
Bibcode: 2000A&A...363..289G
Altcode:
We analyse the correlative relationships between various quantities
derived from 2-D inhomogeneous and time-dependent model atmospheres
and between selected simulated line parameters to compare them with
height-dependent correlations derived from spectral observations. We
detect three photospheric regions: thermal convection, overshooting
convection and a transition layer. We also show that correlations
found for the model data and those computed within simulated spectral
observations are a good testing tool for line formation depths. As
an example, we examine two criteria, providing heights of line core
formation in LTE, and conclude that the approach which defines
this quantity as geometrical height at line center optical depth
τλ0 = 1 is likely more suitable for diagnostic purposes
than the method based on depression contribution function.
Title: Size-dependent properties of simulated 2-D solar granulation
Authors: Gadun, A. S.; Hanslmeier, A.; Pikalov, K. N.; Ploner,
S. R. O.; Puschmann, K. G.; Solanki, S. K.
Bibcode: 2000A&AS..146..267G
Altcode:
Two time-dependent sets of two-dimensional hydrodynamic models of solar
granulation have been analyzed to obtain dependence of simulated thermal
convection on the horizontal size of the convection cells. The two
sets of models treat thermal convection either as fully non-stationary,
multiscale convection (granular convection is a surface phenomenon) or
as quasi-steady-state convection cells (they treat granular convection
as a collection of deep-formed cells). The following results were
obtained: 1) quasi-steady convection cells can be divided into 3
groups according to their properties and evolution, namely small-scale
(up to L ~ 900 km), intermediate-scale (1000-1500 km) and large-scale
(larger 1500 km) convection cells. For the first group thermal damping
due to radiative exchange of energy, mostly in the horizontal direction,
is very important. Large-scale cells build up a pressure excess, which
can lead to their total fragmentation. Similar processes also acts on
the fully non-stationary convection. 2) The largest horizontal size
of convection cells for which steady-state solutions can be obtained
is about 1500 km. This corresponds to granules, i.e. the bright
parts of the convection cells, with a diameter of about 1000 km. 3)
In addition to the zone of high convective instability associated
with the partial ionization of hydrogen, we identify another layer
harboring important dynamic processes in steady-state models. Just
below the hydrogen-ionization layer pressure fluctuations and the
acoustic flux are reduced. Steady-state models with reflecting lateral
boundaries even exhibit an inversion of pressure fluctuations there. 4)
From observational point of view the surface convection differs from
steady-state deep treatment of thermal convection in the dependence
of vertical granular velocities on their sizes for small-scale
inhomogeneous. However, they cannot be distinguished by the dependence
of temperature or emergent intensity of brightness structures. 5) Both
kinds of models demonstrate the inversion of density in subphotospheric
layers. It is more pronounced in small-scale cells and inside hot
upflows. 6) The brightness of simulated granules linearly increases
with their size for small granules and is approximately constant or
even decreases slightly for larger granules. For intergranular lanes
the simulations predict a decrease of their brightness with increasing
size. It falls very rapidly for narrow lanes and remains unchanged
for broader lanes. 7) A quantitative comparison of the brightness
properties of simulated granulation with real observations shows
that the strong size-dependence of the properties of the smallest
simulated granules is not accessible to current observations due to
their limited spatial resolution. The observed size dependences result
rather from spatial smoothing and the granule-finding algorithm. We
do not exclude, however, an influence of the limitations of the 2-D
treatment of thermal convection on the present results.
Title: Evaluation of a low-end architecture for collaborative software
development, remote observing, and data analysis from multiple sites
Authors: Messerotti, Mauro; Otruba, Wolfgang; Hanslmeier, Arnold
Bibcode: 2000SPIE.4011...11M
Altcode:
The Kanzelhoehe Solar Observatory is an observing facility located
in Carinthia (Austria) and operated by the Institute of Geophysics,
Astrophysics and Meteorology of the Karl- Franzens University Graz. A
set of instruments for solar surveillance at different wavelengths
bands is continuously operated in automatic mode and is presently
being upgraded to be used in supplying near-real-time solar activity
indexes for space weather applications. In this frame, we tested a
low-end software/hardware architecture running on the PC platform in a
non-homogeneous, remotely distributed environment that allows efficient
or moderately efficient application sharing at the Intranet and Extranet
(i.e., Wide Area Network) levels respectively. Due to the geographical
distributed of participating teams (Trieste, Italy; Kanzelhoehe and
Graz, Austria), we have been using such features for collaborative
remote software development and testing, data analysis and calibration,
and observing run emulation from multiple sites as well. In this work,
we describe the used architecture and its performances based on a
series of application sharing tests we carried out to ascertain its
effectiveness in real collaborative remote work, observations and data
exchange. The system proved to be reliable at the Intranet level for
most distributed tasks, limited to less demanding ones at the Extranet
level, but quite effective in remote instrument control when real time
response is not needed.
Title: NOAA AR 8210: Evolution and Flares from Multiband Diagnostics
Authors: Warmuth, Alexander; Hanslmeier, Arnold; Messerotti, Mauro;
Cacciani, Alessandro; Moretti, Pier Francesco; Otruba, Wolfgang
Bibcode: 2000SoPh..194..103W
Altcode:
NOAA 8210 has been a region showing a remarkable level of activity well
before solar maximum. Dominated by a large, rapidly rotating δ spot,
it produced several intense flares during its disk passage at the end
of April-beginning of May 1998. We examine the development of AR 8210 in
Hα and white light (WL) and study the evolution of its complex magnetic
topology. While the other principal flares are briefly reviewed,
the great X1.1/3B flare of 2 May, which was observed at Kanzelhöhe
Solar Observatory during a SOHO/UVCS ground support campaign, is
studied in detail. This event has been documented in full-disk Hα
and Na-D intensitygrams, Dopplergrams, and magnetograms, with a time
cadence of one minute each. The flare was associated with a CME and
produced significant geomagnetic effects. Furthermore, we point out
the perspectives for our planned Flare Monitoring and Alerting System,
since the two new instruments (Magneto-Optical Filter and Digital Hα
camera), which made their first operational run with the campaign,
are crucial components for this program.
Title: Determination of fractal dimensions of solar radio bursts
Authors: Veronig, A.; Messerotti, M.; Hanslmeier, A.
Bibcode: 2000A&A...357..337V
Altcode: 2002nlin......7021V
We present a dimension analysis of a set of solar type I storms and
type IV events with different kind of fine structures, recorded at the
Trieste Astronomical Observatory. The signature of such types of solar
radio events is highly structured in time. However, periodicities
are rather seldom, and linear mode theory can provide only limited
interpretation of the data. Therefore, we performed an analysis
based on methods of the nonlinear dynamics theory. Additionally to the
commonly used correlation dimension, we also calculated local pointwise
dimensions. This alternative approach is motivated by the fact that
astrophysical time series represent real-world systems, which cannot
be kept in a controlled state and which are highly interconnected with
their surroundings. In such systems pure determinism is rather unlikely
to be realized, and therefore a characterization by invariants of the
dynamics might probably be inadequate. In fact, the outcome of the
dimension analysis does not give hints for low-dimensional determinism
in the data, but we show that, contrary to the correlation dimension
method, local dimension estimations can give physical insight into the
events even in cases in which pure determinism cannot be established. In
particular, in most of the analyzed radio events nonlinearity in the
data is detected, and the local dimension analysis provides a basis
for a quantitative description of the time series, which can be used
to characterize the complexity of the related physical system in a
comparative and non-invariant manner. In this frame, the degree of
complexity we inferred for type I storms is on the average lower than
that relevant to type IV events. For the type IV events significant
differences occur with regard to the various subtypes, where pulsations
and sudden reductions can be described by distinctly lower values than
spikes and fast pulsations.
Title: First Observations with the Global High-Resolution H-alpha
Network
Authors: Varsik, J. R.; Steinegger, M.; Denker, C.; Goode, P. R.;
Wang, H.; Luo, G.; Chen, D.; Zhang, Q.; Otruba, W.; Hanslmeier, A.;
Freislich, H.
Bibcode: 2000SPD....3102108V
Altcode: 2000BAAS...32..830V
We are in the final stages of establishing a three-site global network
for continuous full disk H-alpha observations based on our experience
with making high-resolution full disk H-alpha observations at Big
Bear Solar Observatory. Utilizing existing telescopes at Big Bear
Solar Observatory (USA), Kanzelhoehe Solar Observatory (Austria),
and Yunnan Astronomical Observatory (China), the three stations are
each equipped with 2K X 2K CCD detectors and will monitor the Sun at a
1 minute cadence. We expect to monitor the emergence of each new flux
region to obtain an unbiased data set in order to understand why some
regions grow to super-activity while most decay quickly, as well as a
more complete and uniform set of flare observations. We also expect
to implement automatic detection of filament eruptions. Having high
cadence data from three observing stations will also increase the
accuracy of solar rotation rates as determined by feature tracking
techniques. We will show the first data sets from the new network.
Title: Dynamics of the upper solar photosphere
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Neunteufel, B.;
Wöhl, H.
Bibcode: 2000A&A...356..308H
Altcode:
The dynamics of the upper solar photosphere was studied by using
1-D photospheric line spectrograms obtained using the VTT of the
Observatorio del Teide. Three spectral lines with line core formation
heights between 250 and 500 km were analyzed. It is clearly seen that at
these levels the velocity and intensity fields are highly correlated
but different from the lower lying zone where convective motions
predominate. This is shown by classical methods (using correlations and
bisectors) as well as by applying the Hurst exponent method to the data.
Title: Fe II lines in the problem of the diagnostic of solar
photospheric shocks
Authors: Gadun, A. S.; Hanslmeier, A.
Bibcode: 2000KFNT...16..130G
Altcode:
We propose to use Fe II lines observed near the solar limb for the
detection of photospheric shocks at granule edges. Their theoretical
spectral scans synthesized with 2-D models provide a more clear
evidence for photospheric shocks as compared to spectral lines of
neutral elements.
Title: Correlative analysis of 2-D solar atmosphere
Authors: Gadun, A. S.; Hanslmeier, A.
Bibcode: 2000KFNT...16..121G
Altcode:
Correlations between various parameters of 2-D inhomogeneous
time-dependent solar atmospheres are analyzed to be directly related
to height-dependent correlations found on the basis of spectral
simulations. We detect four photospheric regions with thermal and
overshooting convection, transition zone, and fully oscillating
layears. The correlations found for the model data and those computed
within simulated spectral scans are a good testing tool for systems
of spectral line heights if these correlations are analyzed in
comparison. In particular, we examine two methods providing the heights
of line core formation in LTE and show that the approach which defines
this quantity as a geometrical height at the optical depth of line
center τλ0 = 1 is more suitable for diagnostic purpose
than the method based on depression contribution function.
Title: Automatic Image Processing in the Frame of a Solar Flare
Alerting System
Authors: Veronig, A.; Steinegger, M.; Otruba, W.; Hanslmeier, A.;
Messerotti, M.; Temmer, M.; Gonzi, S.; Brunner, G.
Bibcode: 2000HvaOB..24..195V
Altcode:
In the present paper we describe image processing techniques applied
to solar H-alpha full-disk images, with the objective of automatic
and quasi real-time detection of the onset of H-alpha flares and
describing their evolution. For this purpose we utilize a combination
of region-based and edge-based image segmentation methods.
Title: Automatic Image Segmentation and Feature Detection in Solar
Full-Disk Images
Authors: Veronig, A.; Steinegger, M.; Otruba, W.; Hanslmeier, A.;
Messerotti, M.; Temmer, M.; Brunner, G.; Gonzi, S.
Bibcode: 2000ESASP.463..455V
Altcode: 2000sctc.proc..455V
At Kanzelhoehe Solar Observatory, Austria, a solar activity monitoring
and flare alerting system is under development, which will be based
on the parametrization of solar flare activity using photometric and
magnetic full-disk images of the Sun obtained simultaneously with high
time cadence. An important step in this project is the automatic image
segmentation and feature detection of solar activity phenomena related
to the occurrence of solar flares. In a first step we have developed
a procedure for automatically detecting the onset and describing the
evolution of flares in H-alpha full-disk images.
Title: 3-D Tomography of the Solar Photosphere
Authors: Hanslmeier, A.; Kucera, A.; Rybak, J.; Wohl, H.
Bibcode: 2000ESASP.463..333H
Altcode: 2000sctc.proc..333H
No abstract at ADS
Title: Granular Evolution from 2D (x,t)-Slices and from Tracking
Granules
Authors: Poetzi, W.; Hanslmeier, A.; Brandt, P. N.
Bibcode: 2000ESASP.463..407P
Altcode: 2000sctc.proc..407P
No abstract at ADS
Title: Local and Global Magnetic Oscillations in the Photosphere
Authors: Moretti, P. F.; Cacciani, A.; Hanslmeier, A.; Messerotti,
M.; Otruba, W.
Bibcode: 2000ESASP.463..381M
Altcode: 2000sctc.proc..381M
The solar influence on the terrestrial climate is typically associated
to changes during the solar cycle, that is at timescales of years and
more. In fact, the variability seems to be related to the magnetic
activity. Nevertheless, the dynamic of the magnetic field is still not
well understood. The characteristics of the processes acting at higher
temporal frequencies (such as flares etc.) are clearly a signature
of long term magnetic changes and their investigation supports the
understanding of the energy relaxing in the interplanetary space. Four
hour fulldisk magnetograms (with a 4 arcsec/pix resolution) obtained
in the Sodium D-lines have been analyzed pixel-by-pixel (locally) and
in the l-nu diagram (globally). The magnetic oscillations have been
detected at different frequencies and identified on the solar disk. Some
oscillations have been correlated to the H-alpha bright points as the
signature of the magnetic reconnection and subsequent plasma out-flow.
Title: Institut für Geophysik, Astrophysik und Meteorologie
der Universität Graz. Bereich Astrophysik. Sonnenobservatorium
Kanzelhöhe. Jahresbericht für 1999.
Authors: Hanslmeier, A.
Bibcode: 2000MitAG..83..359H
Altcode:
No abstract at ADS
Title: Spectral Statistics of Fe I and Ca II K Lines in the Quiet
and Active Solar Atmosphere
Authors: Kucera, A.; Brcekova, A. K.; Hanslmeier, A.; Rybak, J.;
Woehl, H.
Bibcode: 2000HvaOB..24..111K
Altcode:
Based on two Fe I and Ca II K lines spectra obtained with high spatial
and spectral resolution we investigated some spectral characteristics
of these lines in quiet and active regions. In this paper we present
the behaviour of the central line intensities in different types of
solar activity. We discuss the obtained results and compare them with
the results reported by other authors.
Title: An Overview of the New Global High-Resolution H-alpha Network
Authors: Steinegger, M.; Hanslmeier, A.; Otruba, W.; Freislich, H.;
Denker, C.; Goode, P. R.; Marquette, W. M.; Varied, J.; Wang, H.;
Luo, G.; Chen, D.; Zhang, Q.
Bibcode: 2000HvaOB..24..179S
Altcode:
In this paper we give a brief overview of the new global high resolution
H-alpha network which was recently established between the Big Bear
Solar Observatory (USA), the Kanzelhoehe Solar Observatory (Austria),
and the Yunnan Astronomical Observatory (China). A short description
of the sites, instruments, and the scientific aims, as well as some
sample data are presented.
Title: Applications of nonlinear time series analysis in solar physics
Authors: Veronig, A.; Messerotti, M.; Hanslmeier, A.
Bibcode: 2000swms.work...41V
Altcode:
We applied methods of nonlinear time series analysis to different
aspects of the solar phenomenology, as the solar cycle, the solar
granulation and solar radio bursts. The methods include tests for
deterministic chaos hidden in the data, as the determination of
global attractor dimensions. However, in solar physics we deal
with "real world" time series, which hardly allow to detect pure
determinism. Therefore we also applied tools, which enable to cope with
non-stationarities in the data and provide statistical significance
even in cases where the existence of low-dimensional chaos cannot be
established, like local dimension estimations and recurrence plots. The
relevant methods are described with application to different solar
time series.
Title: Two Dimensional Spectral Time Series
Authors: Hanslmeier, A.; Kucera, A.; Rybak, J.; Woehl, H.
Bibcode: 2000HvaOB..24...81H
Altcode:
We analyze two dimensional time series of solar photospheric
spectrograms in order to study the dynamics of solar fine structures and
their evolution. The two dimensional images were obtained by scanning
over the photosphere. Spectrographic data of this type include a much
higher information than ordinary images.
Title: Statistical Properties Relevant to Solar Flare Prediction
Authors: Temmer, M.; Veronig, A.; Hanslmeier, A.; Steinegger, M.;
Brunner, G.; Gonzi, S.; Otruba, W.; Messerotti, M.
Bibcode: 2000HvaOB..24..185T
Altcode:
We statistically analyzed the characteristic temporal properties of
H-alpha flares, such as duration, rising and setting times, with the aim
to determine a proper acquisition rate for H-alpha patrol observations,
which will be the basis for the automatic flare alerting and prediction
system at the Kanzelhoehe Solar Observatory, Austria. Furthermore,
the comparison of absolute and normalized values reveals interesting
aspects on how flares of different importance classes behave with
respect to the rising and decay phase.
Title: Fe I and Ca II K Lines in Quiet and Active Regions
Authors: Kucera, A.; Brcekova, K.; Hanslmeier, A.; Rybak, J.; Wohl, H.
Bibcode: 2000ESASP.463..357K
Altcode: 2000sctc.proc..357K
No abstract at ADS
Title: The New Global High-Resolution Hα Network: First Observations
and First Results
Authors: Steinegger, M.; Denker, C.; Goode, P. R.; Marquette, W. H.;
Varsik, J.; Wang, H.; Otruba, W.; Freislich, H.; Hanslmeier, A.; Luo,
G.; Chen, D.; Zhang, Q.
Bibcode: 2000ESASP.463..617S
Altcode: 2000sctc.proc..617S
No abstract at ADS
Title: Time Series of Solar Granulation Images. III. Dynamics of
Exploding Granules and Related Phenomena
Authors: Hirzberger, J.; Bonet, J. A.; Vázquez, M.; Hanslmeier, A.
Bibcode: 1999ApJ...527..405H
Altcode:
The evolution of exploding granules is studied by using a spatially as
well as temporally highly resolved time series of white-light images of
80 minute duration. The results of this study show that the dynamics
of exploding granules is strongly affected by their surroundings and
that their appearance is closely related to the mesogranular flow
field. Comparing the behavior of exploding granules with that of
smaller dark structures--so-called dark dots--and with the results of
model simulations leads to the conclusion that both phenomena, as well
as a third newly found phenomenon (dark structures occurring in the
centers of granules that are approximately twice as large as dark dots
but smaller than typical centers of exploding granules) are different
types of strong downflows developing in the centers of granules. The
motions of all these three phenomena--the expansion of exploding
granules and the proper motions of the smaller dark structures,
respectively--can reach velocities close to the sound speed in the solar
photosphere. Another type of structure--narrow intergranular connections
between granules--has also been studied. Our results show that these
structures are real solar phenomena and are not caused by a variation
of the image quality. Therefore, in following and describing their
evolution, we try to find an explanation for their frequent occurrence.
Title: Interaction of Convective Structures with the Magnetic Field
of Solar Pores
Authors: Sobotka, M.; Vázquez, M.; Bonet, J. A.; Hanslmeier, A.
Bibcode: 1999ASPC..184...60S
Altcode:
Time series of high-resolution white-light images of solar pores are
analyzed. Granular motions in the vicinity of pores are driven by
mesogranular flows: Motions toward the pore dominate in the 2 arcsec
zone around the pore boundary, while at larger distances the granules
move away from the pore. Triggered by these motions, small granules
and granular fragments located close to the pore border penetrate into
the pore, where they move inwards as short-lived bright features very
similar to umbral dots. The formation of a transitory penumbra-like
structure at the border of a large pore was observed simultaneously
with a temporary reorganization of adjacent granular field to expanding
elongated granules separated by dark filaments.
Title: An Effective, Low-Cost Architecture for Remote Observing and
Distributed Data Analysis Over the WAN
Authors: Messerotti, M.; Otruba, W.; Hanslmeier, A.
Bibcode: 1999ASPC..184..324M
Altcode:
We describe the architecture and the performance of a low-cost
software-hardware system, which allows common work and remote observing
to be carried out over both the Local (LAN) and the Wide Area Network
(WAN) in the frame of a remotely distributed working group. The system
consists in a set of Personal Computers (PC) of the Pentium class
running Microsoft Windows 95 or NT 4 and the free application NetMeeting
2.1. The physical location of the machines was Trieste, Kanzelhoehe
and Graz respectively. A series of tests was performed to ascertain
the usability of such a configuration for scientific applications. In
particular, we tested remote joint work as software development and
data analysis (with particular regard to IDL applications), data
transfer, remote observing by simulating access to the Kanzelhoehe
Vacuum Telescope, and audio/video communications. As expected, all
such applications are quite demanding from the point of view of both
local hardware performances and required bandwidth. Despite of that,
the system proved to be an effective and practical tool, low-cost and
easy to set up due to its full integrability with the above Operating
Systems (O/S).
Title: Fiber Optics Device for Solar Spectroscopy - First Measurements
Authors: Kucera, A.; Rybák, J.; Wöhl, H.; Hanslmeier, A.
Bibcode: 1999ASPC..184..319K
Altcode:
In 1996 we introduced the fiber optics device designed for 2D
solar spectroscopy (Kucera et al. 1997). Now we present the first
results obtained within last year. First experiences with wavelength
calibration, light transmission through the fibers, noise reduction,
software for reduction of observations and preliminary results of
reduced scientific data are presented.
Title: Time Series of Solar Granulation Images. II. Evolution of
Individual Granules
Authors: Hirzberger, J.; Bonet, J. A.; Vázquez, M.; Hanslmeier, A.
Bibcode: 1999ApJ...515..441H
Altcode:
The properties of the evolution of solar granulation have been
studied using an 80 minute time series of high spatial resolution
white-light images obtained with the Swedish Vacuum Solar Telescope at
the Observatorio del Roque de los Muchachos, La Palma. An automatic
tracking algorithm has been developed to follow the evolution of
individual granules, and a sample of 2643 granules has been analyzed. To
check the reliability of this automatic procedure, we have manually
tracked a sample of 481 solar granules and compared the results of both
procedures. An exponential law gives a good fit to the distribution of
granular lifetimes, T. Our estimated mean lifetime is about 6 minutes,
which is at the lower limit of the ample range of values reported
in the literature. We note a linear increase in the time-averaged
granular sizes and intensities with the lifetime. T=12 minutes marks
a sizeable change in the slopes of these linear trends. Regarding
the location of granules with respect to the meso- and supergranular
flow field, we find only a small excess of long-lived granules in the
upflows. Fragmentation, merging, and emergence from (or dissolution
into) the background are the birth and death mechanisms detected,
resulting in nine granular families from the combination of these
six possibilities. A comparative study of these families leads to
the following conclusions: (1) fragmentation is the most frequent
birth mechanism, while merging is the most frequent death mechanism;
(2) spontaneous emergence from the background occurs very rarely,
but dissolution into the background is much more frequent; and (3)
different granular mean lifetimes are determined for each of these
families; the granules that are born and die by fragmentation have
the longest mean lifetime (9.23 minutes). From a comparison of the
evolution of granules belonging to the most populated families, two
critical values appear for the initial area in a granular evolution:
0.8 Mm2 (dg=1.39") and 1.3 Mm2
(dg=1.77"). These values mark limits characterizing the birth
mechanism of a granule, and predict its evolution to some extent. The
findings of the present work complement the earlier results presented
in this series of papers and reinforce with new inputs, as far as
the evolutionary aspects are concerned, the conclusion stated there
that granules can be classified into two populations with different
underlying physics. The boundary between these two classes could be
established at the scale of dg=1.4".
Title: Solar Line Bisectors in the Infrared
Authors: Puschmann, K.; Hanslmeier, A.; Solanki, S. K.
Bibcode: 1999ASSL..239..227P
Altcode: 1999msa..proc..227P
In the present work we made some analysis with respect to shifts
and asymmetries of infrared solar spectral lines to get information
about vertical velocity fields in the deep layers of the Solar
Photosphere. For the analysis of shifts and asymmetries of bisectors
were used. We averaged bisectors belonging to a group of similar line
parameter. Therefore it was possible, to analyse correlations between
asymmetries and line shifts and corresponding vertical velocities with
line parameters and to discuss the results with other literature.
Title: Motions in the Solar Atmosphere
Authors: Hanslmeier, Arnold; Messerotti, Mauro
Bibcode: 1999ASSL..239.....H
Altcode: 1999msa..proc.....H
No abstract at ADS
Title: Temporal Evolution of Fine Structures in and around Solar Pores
Authors: Sobotka, Michal; Vázquez, Manuel; Bonet, José Antonio;
Hanslmeier, Arnold; Hirzberger, Johann
Bibcode: 1999ApJ...511..436S
Altcode:
Time series of high-resolution white-light images of six solar pores,
observed in 1993 and 1995 at the Swedish Vacuum Solar Telescope (La
Palma), are analyzed. The pores constitute an almost ideal laboratory
in which to study the interaction of a vertical magnetic field with
surrounding convective motions, without the perturbation of the inclined
magnetic field in the penumbra. Umbral dots observed in a large (D=8.9")
pore are similar to those in mature umbrae, but they live longer, are
brighter, and have a higher filling factor. Granular motions in the
vicinity of pores are driven by mesogranular flows. Motions toward the
pore dominate in the 2" zone around the pore boundary, while at larger
distances the granules move away from the pore. Pushed by these motions,
small granules and granular fragments located close to the pore border
sometimes penetrate into the pore, where they move inward as bright
short-lived features very similar to umbral dots. The capture of bright
features by the pore is probably a microscale manifestation of the
``turbulent erosion,'' which results in the decay of the pore. Formation
of a transitory penumbra-like structure at the border of the large
pore was observed simultaneously with the appearance of expanding
elongated granules, separated by dark filaments, in an adjacent
granular field. These effects can be interpreted as a consequence of
emerging bipolar magnetic ``loops'' caused by a temporary protrusion
of opposite magnetic polarity.
Title: Modelling of Solar Irradiance Variations
Authors: Otruba, W.; Brandt, P. N.; Eker, Z.; Hanslmeier, A.;
Steinegger, M.
Bibcode: 1999ASSL..239..213O
Altcode: 1999msa..proc..213O
A modelling of the sunspot deficit in solar irradiance measurements
in 3 spectral wavelengths and the total flux as observed by the VIRGO
experiment on SOHO has been performed for several periods of 1996 in
a pixel-by-pixel manner using high resolution photoheliograms taken at
Kanzelhöhe Observatory. The calculation of the irradiance contributions
of the other features of active regions is in progress.
Title: Institut für Astronomie, Universität Graz,
Sonnenobservatorium Kanzelhöhe. Jahresbericht für 1998.
Authors: Hanslmeier, A.
Bibcode: 1999MitAG..82..347H
Altcode:
No abstract at ADS
Title: Longterm Prediction of Solar Activity Using the Combined Method
Authors: Hanslmeier, Arnold; Denkmayr, Klaus; Weiss, Peter
Bibcode: 1999SoPh..184..213H
Altcode:
The Combined Method is a non-parametric regression technique for
long-term prediction of smoothed monthly sunspot numbers. Starting from
a solar minimum, a prediction of the succeeding maximum is obtained
by using a dynamo-based relation between the geomagnetic aa index and
succeeding solar maxima. Then a series of predictions is calculated by
computing the weighted average of past cycles of similar level. This
technique leads to a good prediction performance, particularly in the
ascending phase of the solar cycle where purely statistical methods tend
to be inaccurate. For cycle 23 the combined method predicts a maximum
of 160 (in terms of smoothed sunspot number) early in the year 2000.
Title: Time Evolution of Solar Granulation
Authors: Hirzberger, J.; Hanslmeier, A.; Bonet, J.; Vázquez, M.
Bibcode: 1999ASPC..183..507H
Altcode: 1999hrsp.conf..507H
No abstract at ADS
Title: The Magneto-Optical Filter at Kanzelhöhe
Authors: Cacciani, A.; Moretti, P. F.; Messerotti, M.; Hanslmeier,
A.; Otruba, W.; Pettauer, T. V.
Bibcode: 1999ASSL..239..271C
Altcode: 1999msa..proc..271C
An observing station based on the Magneto-Optical Filter (MOF)
technology has been installed at Kanzelhöhe at the beginning of
1997. In this paper, the main characteristics of this instrument are
discussed and a one day solar velocity observing run is shown.
Title: Time Series of Solar Photospheric Spectrograms Bisector
Analysis
Authors: Hanslmeier, A.; Bonet, J.; Vázquez, M.
Bibcode: 1999ASPC..183..479H
Altcode: 1999hrsp.conf..479H
No abstract at ADS
Title: Solar Activity Monitoring - a New Approach Using Combined
Datasets, Pattern Recognition and Neural Networks
Authors: Hanslmeier, A.; Veronig, M.; Steinegger, M.; Brunner, G.;
Gonzi, S.; Temmer, M.; Otruba, W.; Messerotti, M.
Bibcode: 1999HvaOB..23...31H
Altcode:
In this paper we give an overview of the activities of the recently
established solar activity monitoring and flare alerting working group
at the University of Graz and its planned activities. Solar flares
can trigger events at the earth environment that can be dangerous to
technological systems as well as to human life. Therefore, it is an
important target in solar physics to predict such events, providing
an essential contribution to space weather forecasts.
Title: Searching for mesogranulation - problems and possible methods.
Authors: Mühlmann, W.; Hanslmeier, A.; Brandt, P. N.
Bibcode: 1999joso.proc..145M
Altcode:
A time series of 8.5 hours with 1500 images of the solar granulation
is investigated in this study. By various methods, such as feature
tracking, LCT, and pattern recognition the authors try to find the
mesogranulation. The divergence of the velocity fields calculated by
LCT methods shows the mesogranular pattern after about 1.5 hours and,
after a longer integration time (5 to 6 hours), also the supergranular
pattern. Cork plots, i.e. small points, driven by the velocity vectors,
show the same behaviour. Following the granules shows that they are
moving toward regions looking like a network of 10 arcsec in size,
which could be seen as the inter-mesogranular regions. The pattern
recognition method does not show any correlation with the other methods.
Title: Cellular Automata Models for Convection
Authors: Schaffenberger, W.; Hanslmeier, A.; Messerotti, M.
Bibcode: 1999ASSL..239..267S
Altcode: 1999msa..proc..267S
We present here three models for convection. The models make use of
the concept of cellular automata (CA). CA are discrete systems. The
advantages of CA are their simple and parallel structure. The
simplest of the presented models simulates two-dimensional Boussinesq
convection. The two other models are extensions to compressible fluids
and three-dimensional convection, respectively. We derive the model
equations for the simplest model and present some of our results.
Title: The solar surveillance program at the Kanzelhoehe Solar
Observatory: new facilities for high speed digital imaging and
dynamic event tracking
Authors: Messerotti, M.; Otruba, W.; Warmuth, A.; Cacciani, A.;
Moretti, P. F.; Hanslmeier, A.; Steinegger, M.
Bibcode: 1999WPP...155..321M
Altcode:
The Kanzelhoehe Solar Observatory (Austria) has been devoted to
multiwavelength synoptic observations of the sun for a long time in the
frame of a long-term Solar Surveillance Program. Recently the observing
capabilities were boosted by two new instruments for full-disk imaging:
a digital H-alpha camera and a Magneto-Optical Filter (MOF) system. In
this frame, we sketch the feasibility of a fully digital flare survey
and a quasi-real time analysis system based on an artificial neural
network, which might be relevant to the prediction of solar events
affecting the solar-terrestrial environment.
Title: Some Properties of the Solar Granulation and Mesogranulation
Authors: Mühlmann, W.; Hanslmeier, A.; Brandt, P. N.
Bibcode: 1999ASSL..239..223M
Altcode: 1999msa..proc..223M
Based on a 8.7 hour time series of solar granulation images (Simon
et al., 1994), of a spatial resolution mostly better than 400 km, we
calculated some properties of granules, vorticity and divergence of
the velocity fields and we tried to determine the mesogranular pattern
by corks.
Title: Nonlinear Measures: an Application to Solar Radio Bursts
Authors: Veronig, V. M.; Messerotti, M.; Hanslmeier, A.
Bibcode: 1999joso.proc..186V
Altcode:
We investigated different types of solar radio bursts by means of the
nonlinear dynamics theory, as phase space reconstructions, dimension
estimates, and recurrence diagrams. The data sets are high time
resolution (50 Hz), single-frequency recordings from the multichannel
radio polarimeter of the Trieste Observatory. Special attention was
paid to the non-stationary behaviour of the data and its implications
for different nonlinear measures.
Title: Granulation in active regions as compared to quiet regions
Authors: Hirzberger, J.; Bonet, J. A.; Vázquez, M.; Hanslmeier, A.;
Sobotka, M.
Bibcode: 1999AGAb...15...88H
Altcode: 1999AGM....15..P09H
A comparative study of the statistical properties of granulation
in active and quiet regions is performed. The analysis is based on a
high-resolution time series of simultaneous white light (lambda5425 Å)
and G-band (lambda 4308 Å) images obtained at the Swedish Vacuum Solar
Telescope, La Palma, Canary Islands. The G-band images have been used
to discern quiet and active regions in the field of view, whereas the
white-light images were taken to analyze the photometry, size and time
evolution of granules in regions of different magnetic activity. Power
spectra confirm that the granular size decreases with increasing G-band
brightness. Granules with diameters below 0''.8 are systematically
brighter in the abnormal granulation than in quiet regions. These
small and bright elements are embedded in a diffuse background of
approximately mean photospheric brightness covering all the fields of
abnormal granulation. The granular lifetime decreases with increasing
G-band brighness. The conclusions about the behaviour of the granulation
have been decontaminated of the influence of magnetic elements (the
so-called Bright Points), that have been separated using criteria
of size (d < 0''.5) and lifetime (T > 6 min). A significant
fraction of them are concentrated in regions of high G-band activity,
an emerging flux region, and the rest are m ainly aligned outlining a
cellular pattern (the magnetic network formed by supergranular motions).
Title: Synoptic Photometric Full-Disk Observations at Kanzelhöhe
Solar Observatory
Authors: Steinegger, M.; Hanslmeier, A.
Bibcode: 1999ASSL..239..209S
Altcode: 1999msa..proc..209S
At the Institute of Astronomy in Graz a small full-disk telescope
for photometric observations of the Sun is under construction. After
completion this instrument will provide long-term solar observations
of the photosphere and chromosphere in various wavelengths with high
time cadence. In this paper the main characteristics of this instrument
and its components are described.
Title: Localized Measures of Solar Radio Bursts
Authors: Veronig, A.; Hanslmeier, A.; Messerotti, M.
Bibcode: 1999ASSL..239..255V
Altcode: 1999msa..proc..255V
We investigated localized measures of solar radio bursts by analyzing
local pointwise dimensions and recurrence plots of a set of type I
and type IV solar radio bursts. The analysis indicates that type IV
bursts are a more complex phenomenon than type I bursts.
Title: Starspot modelling approach of the solar irradiance variability
as measured by SOHO/VIRGO.
Authors: Steinegger, M.; Brandt, P. N.; Eker, Z.; Hanslmeier, A.;
Otruba, W.
Bibcode: 1999joso.proc..160S
Altcode:
The evolution of solar active regions and their passage across the
visible solar hemisphere cause the well known phenomenon of solar
irradiance variability. The VIRGO experiment onboard SOHO measures
the total solar irradiance as well as the spectral irradiance in three
wavelength bands. For some selected periods in 1996, during which only
a few active regions were present on the Sun, the authors try to model
the total and the spectral irradiance variations by use of SOHO/MDI full
disk images and ground-based photometric data like photoheliograms and
spectroheliograms. In a new approach the authors apply starspot models
to the problem of modelling solar irradiance variations. Therefore,
this attempt might also lead to an improved modelling of spatially
unresolved starspots.
Title: Temporal Evolution of Artificial Solar Granules
Authors: Ploner, S. R. O.; Solanki, S. K.; Gadun, A. S.; Hanslmeier, A.
Bibcode: 1998SSRv...85..261P
Altcode:
We study the evolution of artificial granulation on the basis of 2-D
hydrodynamical simulations. These clearly show that granules die in
two different ways. One route to death is the well known bifurcation
or fragmentation of a large granule into 2 smaller ones (exploding
granules). The other pathway to death is characterized by merging
intergranular lanes and the accompanying dissolution of the granule
located between them. It is found that the lifetime and maximum
brightness is independent of the way in which granules evolve and
die. They clearly differ in size, however, with exploding granules
being in general significantly larger.
Title: Determination of Local Pointwise Dimensions for Solar Radio
Bursts
Authors: Veronig, A.; Messerotti, M.; Hanslmeier, A.; Rucker, H. O.
Bibcode: 1998cee..workE..66V
Altcode:
We analyzed a set of type I and type IV solar radio bursts. The data
sets are high time resolution, single frequency recordings from the
multichannel radio polarimeter of the Trieste Astronomical Observatory
operating in the meter range. In order to get indications about the
complexity of the underlying physical system we determined the fractal
dimension of a tentative attractor. As especially indicated by localized
measures (Mayer-Kress, 1994), as, e.g., the local pointwise dimension,
type IV bursts seem to be phenomena of higher complexity and higher
diversity from one event to another than type I bursts (Veronig et al.,
1998). Figure 1 represents the time series of pulsations in a type IV
event and the related local pointwise dimension D_p(xii),
respectively D_p(t_i), showing a clear convergence behaviour
interrupted by a few sections of high values of D_p(t_i), indicating
non-uniformities of the system's attractor. Figure 1. Top panel: Time
series of a type IV event with quasi-periodic pulsations. Bottom panel:
The related local pointwise dimension, converging to an average value
of bar{D}_p ~4.1. A fractal dimension of ~4.1 means that the number of
free parameters, needed to describe the underlying dynamical system,
should be at least 5. In future we plan to develop an extension of
the dimension algorithm to be applied to two dimensional time series
in order to include the additional information given by dynamic radio
spectra. The radio spectra will be acquired by the newly developed
digital spectropolarimeter with time resolution Delta t = 1ms and
spectral resolution Delta f = 10kHz to be installed at the radio
station Lustbuhel, Graz, Austria (Kleewein, 1997).
Title: RODOMA: The Rome network for Doppler and magnetic oscillations
Authors: Cacciani, A.; Hanslmeier, A.; Messerotti, M.; Moretti, P. F.;
Otruba, W.; Pettauer, Th.; Rodgers, W.
Bibcode: 1998ESASP.418..131C
Altcode: 1998soho....6..131C
The development of the RODOMA network is now at the point to start
taking regular observations from two sites: the Austria site in
Kanzelhoehe and the California site in Apple Valley. The final test
is connected with a UVCS(SOHO) campaign operating between april 20
and May 05 1998. The data consist of Doppler and simultaneous magnetic
and intensity fulldisk images taken at intervals of 30 or 60 seconds,
depending on the final desired precision. The contribution is aimed to
illustrate the state and the characteristics of the instrumentation and
to show samples of results. A third site will be Tashkent in Uzbekistan,
in the framework of the IRIS collaboration.
Title: Institut für Astronomie, Universität
Graz. Sonnenobservatorium Kanzelhöhe. Jahresbericht für 1997.
Authors: Hanslmeier, A.
Bibcode: 1998MitAG..81..307H
Altcode:
No abstract at ADS
Title: Temporal Evolution of Artificial Solar Granules
Authors: Ploner, S. R. O.; Solanki, S. K.; Gadun, A. S.; Hanslmeier, A.
Bibcode: 1998sce..conf..261P
Altcode:
No abstract at ADS
Title: A Photometric Full-Disk Telescope for Kanzelhöhe Solar
Observatory
Authors: Steinegger, M.; Hanslmeier, A.
Bibcode: 1998ASPC..155..270S
Altcode: 1998sasp.conf..270S
No abstract at ADS
Title: Case studies of magnetic topology evolution in active regions
Authors: Cacciani, A.; di Martino, V.; Hanslmeier, A.; Messerotti,
M.; Moretti, P. F.; Pettauer, Th.; Veronig, A.
Bibcode: 1998ASPC..155..229C
Altcode: 1998sasp.conf..229C
We give a preliminary report on the evolution of the magnetic field
topology extrapolated in the current-free approximation for two solar
active regions observed through an MOF imaging magnetograph.
Title: A MOF-based full vector imaging magnetograph
Authors: Cacciani, A.; Comari, M.; Furlani, S.; Hanslmeier, A.;
Messerotti, M.; Moretti, P. F.; Pettauer, Th.; Veronig, A.
Bibcode: 1998ASPC..155..265C
Altcode: 1998sasp.conf..265C
The scheme and the operating principles of a fast, compact,
magneto-optical filter-based, full-vector imaging magnetograph,
currently under development for solar observations, are briefly outlined
as well as planned improvements and possible applications.
Title: Determining fractal dimensions of solar radio bursts
Authors: Veronig, A.; Messerotti, M.; Hanslmeier, A.
Bibcode: 1998joso.proc..166V
Altcode:
We determined fractal dimensions of solar radio bursts, namely the
correlation dimension and the local pointwise dimension of a set of
type I and type IV solar radio bursts. The data sets are high time
resolution (50Hz), single frequency recordings from the multichannel
radio polarimeter of the Trieste Observatory. A comparative study of the
analysis methodology shows that the local pointwise dimension yields
more stable and reliable results than the widely used correlation
dimension. The outcome of the dimension analysis indicates that type
IV bursts are a more complex and diverse phenomenon than type I bursts.
Title: Dynamics of the solar granulation. IV. Granular shear flow.
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Schleicher, H.;
Sigwarth, M.; Staiger, J.
Bibcode: 1997A&A...326..851N
Altcode:
Strong velocity gradients at granular borders appear to be the source
of unresolved velocity fluctuations detectable as line broadening
variations of magnetically and thermally insensitive absorption
lines. Based on spectrograms of high spatial and spectral resolution
taken with the German Vacuum Tower Telescope(VTT) in Izana (Tenerife) we
study the strong velocity gradients and the unresolved velocity field as
well as their mutual interaction. We also investigate the variation of
these quantities with the height in the photosphere, for both a regular
and an exploding granule. By means of a coherence analysis we study,
furthermore, the extension of the convective and turbulent fluctuation
field of the granulation layers into the overlying overshoot layers as
a function of the wavenumber. The results of the coherence analysis
are consistent with, and complementary to, those obtained from the
investigation of regular and exploding granules. The small and large
scales of the convective and unresolved velocity field behave clearly
different as far as their penetration into the overlying photospheric
layers is concerned. One pressure scale height above the continuum we
find an unresolved velocity field that does not show any resemblance
to the same velocity field at the continuum level. We find that the
symmetry behavior of the unresolved velocity field with respect to
the granular flow varies with the height in the photosphere. The
unresolved velocity field could be of oscillatory, convective, or
turbulent character. However, the fact that the unresolved velocity
field is more prominent at the granular border, which is also the
location of strong shear flow, favors its turbulent character. In
this sense the granules can be seen as quasi-laminar convective flows
emerging in the turbulent field of the overshoot layers.
Title: Simulating convection with cellular automata.
Authors: Schaffenberger, W.; Hanslmeier, A.; Messerotti, M.
Bibcode: 1997AGAb...13..175S
Altcode:
No abstract at ADS
Title: A Solar α - ω Dynamo Study and its Transition to Chaos
Authors: Grassmugg, Maria; Hanslmeier, Arnold; Laback, Otto
Bibcode: 1997SoPh..174..437G
Altcode:
In this contribution we present a nonlinear dynamo model, described
by an infinite dimensional system of differential equations, whose
solutions depend on the essential parameter D, the dynamo number. The
solutions and the bifurcation points of the system are determined with
the help of a new developed computer code. We show that, depending on D,
stationary, oscillatory and chaotic solutions, which are characterized
by Lyapunov exponents, result. We find that the solar dynamo may
operate either in the chaotic or in the stable limit cycle domain,
depending on the characteristic value of the dynamo number or the
motion of the convection zone.
Title: Asymmetry and line-parameter variations in
granular-intergranular regions in 2D artificial granulation
Authors: Gadun, A. S.; Hanslmeier, A.
Bibcode: 1997KFNT...13c..24G
Altcode:
Two sets of 2D models of solar granulation are used to interpret
published observations of the spectral lines of Fe I 491.154, 491.178,
and 649.499 nm obtained with high spectral and spatial resolution
over selected granular-intergranular regions. We study variations of
continuum intensity, residual intensity in the line cores, Doppler
velocities, and line asymmetries over granular-intergranular areas
in the center of the solar disk, and compare the correlation between
these parameters obtained from models with observational ones. It
is found that 2D models of the solar granulation that describe the
convective motions as quasi-stationary, cellular, and laminar with the
system of quasi-column vertical photospheric velocities show the high
correlation values between the line-parameter variations and cannot
explain the observational behavior of spectral line characterstics
over single granular-intergranular areas. A good reproduction of
observational results can be found only by applying 2D models that
treat the solar thermal convection as a fully nonstationary system
with interacting flows.
Title: Time Series of Solar Granulation Images. I. Differences
between Small and Large Granules in Quiet Regions
Authors: Hirzberger, J.; Vázquez, M.; Bonet, J. A.; Hanslmeier, A.;
Sobotka, M.
Bibcode: 1997ApJ...480..406H
Altcode:
A 90 minute time series of high spatial resolution white-light images
of solar granulation, obtained at the Swedish Vacuum Solar Tower
(Observatorio del Roque de los Muchachos, La Palma), was analyzed
to study how the physical properties of the granules changed with
size. The observational material was corrected for global motions and
for the instrumental profile, and a subsonic filter was applied. A
definition of granular border was adopted using the inflection points
of the intensity of the images, and the granular cells were defined
as areas including, in addition to the granules, one-half of their
surrounding intergranular lanes. Using time series to investigate the
average behavior of solar granulation has three strong advantages:
the first is the possibility of removing the acoustic waves; second,
the possibility of estimating the effect of the variability of
seeing on our results; and, third, the opportunity to attain high
statistical significance in the analysis as a result of the large
number of extracted granules (61,138). It is shown that the
granules of the sample can be classified according to their mean
and maximum intensities and their fractal dimension into two regimes,
with diameters smaller than and larger than 1.4", respectively. A broad
transition region in which both regimes coexist was found. The resolved
internal brightness structure of both the granules and the intergranular
lanes shows a linear increase of the number of substructures with the
granular and intergranular areas. The diameters of these substructures
range between our effective resolution limit (~0.3") and ~1.5",
with preferential sizes at 0.65" and 0.55", respectively. Moreover,
it seems that large and small granules are unevenly distributed with
respect to the large-scale vertical flows. Thus smaller granules are
more concentrated along downdrafts whereas larger ones preferentially
occupy the updrafts. Finally, a physical scenario compatible with the
existence of these two granular populations is discussed.
Title: Bisectors and line-parameter variations over granular and
intergranular regions in 2-D artificial granulation.
Authors: Gadun, A. S.; Hanslmeier, A.; Pikalov, K. N.
Bibcode: 1997A&A...320.1001G
Altcode:
Two sets of two-dimensional models of the solar granulation have
been used to interpret the published observations of spectral lines
of Fe I 4911.54, 4911.78, and 6494.99Å obtained with high spectral
and spatial resolution over selected granular and intergranular
regions. The models differ by the horizontal size of the modeling
region and treatment of thermal convection. We study the variations
of continuum intensity, residual intensity in the line cores, Doppler
velocities, line asymmetries over granular and intergranular areas
in the center of the solar disk and compare the correlation between
these parameters obtained from models with observational ones. A
good reproduction of the observational results can be found only by
applying d models that treat the solar thermal convection as a fully
non-stationary system with interacting flows. Such models also take
into account the important role of secondary motions that influence
the middle and upper photosphere. As essential perturbing factors
there appear photospheric flows with supersonic velocities which
can change the photometric profiles of granules, create regions with
inversion of temperature distribution and impact onto the velocity
field. Variations of line parameters strongly depend on limitations
in spatial resolution (spatial smearing). This was simulated in the
models by applying different Gaussian smearing functions. Seeing was
found to affect variations of equivalent widths, full widths at half
maxima, and bisectors of the lines most strongly.
Title: Some properties of the solar granulation and mesogranulation.
Authors: Mühlmann, W.; Hanslmeier, A.; Brandt, P. N.
Bibcode: 1997AGAb...13..166M
Altcode:
No abstract at ADS
Title: Photometric Observations of the Solar Atmosphere in Several
Waveleenghts at Kanzelhoehe Solar Observatory
Authors: Steinegger, M.; Hanslmeier, A.
Bibcode: 1997HvaOB..21..115S
Altcode:
A small full-disk telescope for photometric observations of the Sun is
currently under construction at the Institute of Astronomy in Graz,
Austria. After completion this instrument should be installed during
1998 at Kanzelhohe Solar Observatory. It will provide long-term
solar observations of the photosphere and chromosphere in various
wavelengths with high time cadence. The photometric data obtained
will be made accessible to the public by means of an on-line archive,
which will also be incorporated into the international network of
ground-based supporting stations for the SOHO mission. Among the
scientific objectives to be pursued with these photometric data are
the interpretation and modelling of solar irradiance variations as
observed e.g. by the VIRGO experiment onboard the SOHO satellite.
Title: Non Linear Dynamics in Solar Physics
Authors: Hanslmeier, A.
Bibcode: 1997HvaOB..21...77H
Altcode:
In this paper a short overview of the basic concepts and tools of
non linear dynamics followed by some applications to solar physics
is given. These applications include the problematics of the solar
granulation, solar dynamos, and solar radio bursts. The main outcome
of these applications is discussed.
Title: A new telescope for photometric full-disk observations of
the Sun.
Authors: Steinegger, M.; Hanslmeier, A.
Bibcode: 1997AGAb...13..165S
Altcode:
No abstract at ADS
Title: Institut für Astronomie, Universität Graz,
Sonnenobservatorium Kanzelhöhe. Jahresbericht für 1996.
Authors: Hanslmeier, A.
Bibcode: 1997MitAG..80..277H
Altcode:
No abstract at ADS
Title: Variations of line parameters and bisectors over
granular-intergranular regions in the 2-D artificial solar
granulation.
Authors: Gadun, A. S.; Hanslmeier, A.
Bibcode: 1997KPCB...13c..17G
Altcode: 1997KPCB...13Q..17G
Variations in the Fe I lines λλ 491.154, 491.178, and 649.499
nm in the solar spectrum observed with high spectral and spatial
resolution in selected granular-intergranular regions are interpreted
with the use of two sets of solar granulation models which differ
by the horizontal size of the region modeled and by treatment of
thermal convection. The authors analyze variations of the continuum
intensity, residual intensity in the line cores, Doppler velocities,
equivalent widths, half-widths, and asymmetries of synthesized lines
in the center of the solar disk, as well as correlations between the
parameter variations. The authors compare also these correlations
with those between the observed line parameters. It is found that the
models which describe the solar thermal convection as quasi-stationary,
cellular, and laminar motions show strong correlation between line
parameter variations and cannot reproduce the behavior of spectral
line characteristics observed in individual granular-intergranular
areas. Observational results are well reproduced by the models where
the thermal convection is treated as a completely nonstationary system
with active secondary motions in the middle and upper photosphere.
Title: On the Influence of Supernova Shockfronts on the Stability
of the Solar System
Authors: Schaffenberger, W.; Hanslmeier, A.
Bibcode: 1997dbps.conf..393S
Altcode:
No abstract at ADS
Title: Die österreichische Teilnahme am Projekt SOHO.
Authors: Hanslmeier, A.
Bibcode: 1997Sterb..40..106H
Altcode:
No abstract at ADS
Title: Simulation of solar convection with cellular automata -
first results.
Authors: Schaffenberger, W.; Hanslmeier, A.; Messerotti, M.
Bibcode: 1997joso.proc...82S
Altcode:
No abstract at ADS
Title: A solar α-ω dynamo and its transition to chaos.
Authors: Grassmugg, M.; Hanslmeier, A.; Laback, O.
Bibcode: 1997joso.proc...62G
Altcode:
No abstract at ADS
Title: Nonlinear Analysis of Solar Radio Events: A Preliminary
Approach
Authors: Veronig, A.; Messerotti, M.; Hanslmeier, A.
Bibcode: 1997pre4.conf..463V
Altcode: 1997pre4.proc..463V
We analysed a set of time series related to different types of solar
radio events (type I, type IV and spikes) in order to determine the
nature of the underlying generating process through the methods of
nonlinear dynamics. The Grassberger-Procaccia method was used to
evaluate the correlation dimension of a possible attractor in subsets
which fulfilled the stationarity condition. The majority of samples
do not show a low dimensionality, suggesting stochasticity or a high
dimensional system; only two overlapping subsets of one type IV event
with spikes exhibit a finite dimension (D 3.5 and D 3.7). The limited
datasets do not allow to draw any definite conclusion, but the varied
results indicate that a critical analysis on the physical character
of solar radio events is needed to give a consistent interpretation.
Title: Non-linear analysis of the dynamics of solar radio events.
Authors: Veronig, A.; Messerotti, M.; Hanslmeier, A.
Bibcode: 1996AGAb...12..165V
Altcode:
No abstract at ADS
Title: A cellulare automaton for modelling the convection.
Authors: Schaffenberger, W.; Hanslmeier, A.; Messerotti, M.
Bibcode: 1996AGAb...12..162S
Altcode:
No abstract at ADS
Title: Time evolution of solar granulation phenomena.
Authors: Hirzberger, J.; Bonet, J. A.; Hanslmeier, A.; Vázquez, M.;
Sobotka, M.
Bibcode: 1996AGAb...12..160H
Altcode:
No abstract at ADS
Title: Properties of the solar granulation and the mesogranulation.
Authors: Mühlmann, W.; Hanslmeier, A.; Brandt, P. N.
Bibcode: 1996AGAb...12..161M
Altcode:
No abstract at ADS
Title: Image Compression by Means of Wavelet Transform - Application
to Solar Observations
Authors: Mühlmann, Werner; Hanslmeier, Arnold
Bibcode: 1996SoPh..166..445M
Altcode:
Images and spectra contain a large amount of data. Therefore the
question arises, how this data can be decreased or compressed without
losing important detail. The discrete wavelet transform is a tool
which can be used to compress data because of its good approximation
properties. It is very easy to implement and requires approximately the
same amount of calculation as the fast Fourier transform. It has the
advantage of giving information both in time and frequency. Since most
of the coefficients in the transformed data are very small compared to
the maximum values, which means that they do not contribute much to the
transform, a large number of them can be neglected. Although some data
get lost, the physical results deduced from the data remain the same, as
is demonstrated by various examples. By this method it is even possible
to compress data containing much noise to high-compression ratios.
Title: Dynamics of the solar granulation. V. The intergranular space.
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Schleicher, H.;
Sigwarth, M.; Staiger, J.
Bibcode: 1996A&A...310..973N
Altcode:
This investigation is based on a spectrogram of extraordinary spatial
resolution selected from a series of 80 spectrograms taken with the
vacuum tower telescope at Izana (Tenerife) in May 1994. The wavelength
range was λλ: 491.00-491.40nm and includes both magnetically sensitive
and insensitive spectral lines. The spectrograph slit intersected parts
of the border and interior of CaII network cells, thus permitting a
comparative study of the granular dynamics at varying, but moderate,
levels of magnetic activity. As diagnostic tools we use the Doppler
shift variation of line cores, which is associated with spatially
resolved velocity structures, and the line broadening variation,
which is a signature of unresolved velocity fluctuations. We discuss
in particular the granular dynamics and the intermittency of the
line broadening within the intergranular space as functions of height
and position relative to network cells. Our results suggest that the
magnetic field in the network is not only located preferentially in
the intergranular space, but furthermore coincides with regions of
enhanced line broadening. We confirm that the Doppler shift variation
is reduced in regions of enhanced magnetic field, but we find that this
reduction affects the entire range of granular scales. The slopes of
the velocity power spectra are independent of the magnetic activity
level. This result is surprising, since on the basis of classical MHD
turbulence theory one would have expected shallower power spectra in
magnetically active regions. The line broadening variation is much
less sensitive to the magnetic field than the line shift variation.
Title: Institut für Astronomie, Universität Graz,
Sonnenobservatorium Kanzelhöhe. Jahresbericht für 1995.
Authors: Hanslmeier, A.
Bibcode: 1996MitAG..79..299H
Altcode:
No abstract at ADS
Title: On the Dynamics of Bright Features in Sunspot Umbrae
Authors: Sobotka, Michal; Bonet, Jose A.; Vazquez, Manuel; Hanslmeier,
Arnold
Bibcode: 1995ApJ...447L.133S
Altcode:
Time series of white-light pictures of the sunspot NOAA 7522, obtained
at the Swedish Vacuum Solar Telescope (La Palma), were analyzed
to study the proper motion of bright features in sunspots. For the
first time, its relation with the dark nuclei present in the umbra is
investigated. The bright features are visible in the penumbra as bright
grains moving into the umbra. A few of them cross the penumbra/umbra
boundary, becoming peripheral umbral dots, which move farther into
the umbra until they meet dark nuclei, braking their motion and
disappearing. In some cases the encounter with a dark nucleus produces
a brightening of the central umbral dots placed on the opposite side
of the nucleus. A similar phenomenon is observed in the grains of a
faint light bridge, when bright penumbral grains collide with one of
the edges of the bridge.
Title: Dynamics of the solar granulation. III. Fractional diffusion.
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Staiger, J.; Westendorp
Plaza, C.; Grabowski, U.
Bibcode: 1995A&A...296..210N
Altcode:
In most papers dealing with random motions and diffusion of small
magnetic elements in the photosphere, the convective flows and
in particular the granulation are considered as drivers of these
motions. The results of these works have been discussed in terms
of the fractal dimension of the granulation as seen in intensity
pictures. So far neither a fractal dimension associated with the
granular velocity field nor the nature of the random walks in the
granular intergranular space have been determined. Using spectrograms
of high spatial resolution taken with the VTT at Izana (Tenerife,
Spain) we investigated the granular velocity field in terms of its
fractal nature and its diffusion properties. We applied the rescaled
range analysis to both the velocity and intensity fields, thus enabling
us to calculate a fractal dimension as well as a "diffusion" exponent
which together characterize the diffusion properties of the granulation
layers. We found a fractal dimension of the granular velocity of the
same order as the fractal dimensions of the distribution of the magnetic
elements in the photosphere, and the fractal dimension corresponding
to the diffusion of the magnetic elements in a fractal geometry. The
diffusion processes in the granulation layers show a subdiffusive
nature characteristic of anomalous diffusion rather than the classical
Fickian diffusion. Anomalous diffusion is often found in stochastic
transport in spatially heterogeneous media. The velocity field of the
granulation can be thought of as a heterogeneous turbulent medium:
the granules show less turbulence than the intergranular space.
Title: Austrian astronomy today: a joint research initiative in
stellar astrophysics
Authors: Breger, M.; Dorfi, E. A.; Hron, J.; Strassmeier, K. G.; Weiss,
W. W.; Oberhummer, H.; Hanslmeier, A.; Lustig, G.; Schober, H. J.
Bibcode: 1995IAUS..176P...4B
Altcode:
No abstract at ADS
Title: Area and intensity distribution in solar granulation
Authors: Hirzberger, J.; Hanslmeier, A.; Bonet, J. A.; Vázquez, M.
Bibcode: 1995IAUS..176P.114H
Altcode:
No abstract at ADS
Title: Solar line bisectors in the infrared
Authors: Puschmann, K.; Hanslmeier, A.; Solanki, S. K.
Bibcode: 1995IAUS..176P.117P
Altcode:
No abstract at ADS
Title: Institut für Astronomie, Universität Graz,
Sonnenobservatorium Kanzelhöhe. Jahresbericht für 1994.
Authors: Hanslmeier, A.
Bibcode: 1995MitAG..78..245H
Altcode:
No abstract at ADS
Title: Dynamics of the solar granulation: bisector analysis
Authors: Hanslmeier, A.; Nesis, A.; Mattig, W.
Bibcode: 1994A&A...288..960H
Altcode:
Using four selected examples of bisector and line parameter variations
due to granular/intergranular motions in the solar photosphere, we
investigate in this paper the coherence between these parameters over
single granular/intergranular areas. It is shown, that there is no
definite correlation between intensity variations, velocity variations
and the shape of the respective bisectors. This is in contradiction to
some model calculations but is consistent with the results extracted
from spatially highly resolved spectrograms in previous papers. We found
enhancements of the line parameter full width at half maximum at the
granular/intergranular border, non symmetric intensity and velocity
variations around their maxima or minima values and a correlation
between velocity variations on the horizontal scale with the full width
at half maximum values (δfw). However, there is no correlation between
δfw and continuum intensity, because the enhancement of δfw occurs
at moderate values of continuum intensity. Since the full width at
half maximum indicates enhanced non thermal motions, these areas are
the location of post shock turbulence as it is described by newer
hydrodynamical models. These examples are of course influenced by
subjective selection but should be on the other hand also described
by hydrodynamical model calculations.
Title: Non linear dynamics of the solar granulation: a first approach
Authors: Hanslmeier, A.; Nesis, A.
Bibcode: 1994A&A...286..263H
Altcode:
The non turbulent or turbulent behaviour of overshooting convective
motions in the solar photosphere is studied by analysing spatially
highly resolved spectrograms. We calculate the variation of a function
similar to the well known Liapunov exponent derived from several
line parameters. When the data are filtered and the variation of
the parameters is considered over subgranular scales (<1arcsec)
the Liapunov like exponents show a random variation at positive
values. Normally, positive values of Liapunov exponents indicate
chaotic motions, and our results are a hint that at subgranular scales
the physics change which is in agreement with results from a coherence
analysis between line parameters at several photospheric heights, the
enhancement of the full width at half maximum in the intergranulum and
model calculations that give evidence for the existence of a turbulent
component of the temperature and velocity field.
Title: The Dynamics of the Solar Granulation Investigated by Fractal
Statistics
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.
Bibcode: 1994ASPC...64..655N
Altcode: 1994csss....8..655N
No abstract at ADS
Title: Spatially highly resolved time series of solar granulation
spectra.
Authors: Hanslmeier, A.; Bonet, J. A.; Vazquez, M.
Bibcode: 1994AGAb...10..114H
Altcode:
No abstract at ADS
Title: Aspects of turbulent convection in stars.
Authors: Jordan, K.; Hanslmeier, A.
Bibcode: 1994AGAb...10..120J
Altcode:
No abstract at ADS
Title: Datacompression unsing wavelets.
Authors: Mühlmann, W.; Hanslmeier, A.
Bibcode: 1994AGAb...10..118M
Altcode:
No abstract at ADS
Title: The solar dynamo - applications to stars.
Authors: Grassmugg, M.; Hanslmeier, A.; Laback, O.
Bibcode: 1994AGAb...10..119G
Altcode:
No abstract at ADS
Title: On the Onset of Secondary Motions in the Higher Solar
Photosphere
Authors: Hanslmeier, A.
Bibcode: 1994swms.conf...15H
Altcode:
No abstract at ADS
Title: Solar granulation models - comparison with observations.
Authors: Hirzberger, J.; Hanslmeier, A.
Bibcode: 1994AGAb...10..115H
Altcode:
No abstract at ADS
Title: Fractal Behavior of the Solar Granular Velocity
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.
Bibcode: 1994smf..conf..288N
Altcode:
No abstract at ADS
Title: Dynamics of the solar granulation.
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig,
W.; Staiger, J.
Bibcode: 1993A&A...279..599N
Altcode:
This investigation is based on a series of spectrograms of extraordinary
spatial resolution taken with the vacuum tower telescope (VTT) at Izana
(Tenerife) in 1990. The quantitative analysis of these spectrograms
reveals an asymmetrical character of the granular flow (non-Benard like
convection). We suggest that a typical granule consists of a region
of high intensity and low turbulence in its interior and a region of
high turbulence and moderate intensity at its border. In other words,
we surmise that reigons of enhanced turbulence outline the borders
of granules. By means of power and coherence analyses we found two
different scaling laws for the small scale range: both the velocity
and intensity power as well as various cross-correlation functions
change their behavior near log k approximately = 0.8.
Title: Fractal Distributions of the Intensity and Velocity Variations
of the Solar Granulation
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.
Bibcode: 1993BAAS...25.1184N
Altcode:
No abstract at ADS
Title: Dynamics of the solar granulation - Coherence of line
parameters and their variation with the height
Authors: Hanslmeier, A.; Nesis, A.; Mattig, W.
Bibcode: 1993A&A...270..516H
Altcode:
We give a coherence analysis of various line parameters deduced
from spatially highly resolved solar photospheric spectra obtained
with the VTT at Izana, Tenerife. The high quality of the spectra
and the selection of the wavelength range containing lines of
different strengths allow us to investigate the transition from
coherent to noncoherent flow patterns in the photosphere which occurs
about a height of 150 km. The low correlation values found here are
explained by an enhanced resolution of random motions and phase shifts
between the intensity-velocity coherence which therefore reduces the
coefficients. Two data sets containing a different number of data
samples are compared and show nearly an identical behavior.
Title: Rapid Variations in the Intergranular Space
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig,
W.; Staiger, J.
Bibcode: 1993ASPC...46..222N
Altcode: 1993mvfs.conf..222N; 1993IAUCo.141..222N
No abstract at ADS
Title: Coherence Analysis of Photospheric Line Parameters in Active
and Non-Active Solar Regions
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1993ASPC...46...36H
Altcode: 1993IAUCo.141...36H; 1993mvfs.conf...36H
No abstract at ADS
Title: Statische Simulation von Sternentstehung durch
Gravitationskollaps.
Authors: Hanslmeier, A.; Farnberger, H. -J.; Mathelitsch, L.
Bibcode: 1993Stern..69..131H
Altcode:
No abstract at ADS
Title: Evidence for Transonic Flows in the Solar Granulation
Authors: Nesis, A.; Bogdan, T. J.; Cattaneo, F.; Hanslmeier, A.;
Knoelker, M.; Malagoli, A.
Bibcode: 1992ApJ...399L..99N
Altcode:
High-resolution observations of the solar granulation are interpreted
in the light of recent numerical simulations of compressible
convection. The observations show a negative correlation between
the width of suitably chosen, nonmagnetic lines and the continuum
intensity. This result is consistent with a model of granular convection
where regions of supersonic horizontal flow form intermittently in
the vicinity of the downflow lanes. We conjecture that the observed
line broadening in the regions of low intensity is caused by enhanced
turbulent fluctuations generated by the passage of shock fronts bounding
the regions of supersonic motion.
Title: What are the Boundaries of Solar Granules?
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig,
W.; Staiger, J.
Bibcode: 1992AAS...180.5109N
Altcode: 1992BAAS...24..814N
This investigation is based on a series of spectrograms of extraordinary
spatial resolution taken with the vacuum tower telescope(VTT) at Iza\
na (Tenerife) in 1990. The quantitative analysis of these spectrograms
revealed an asymmetrical character of the granular flow (non-Benard
like convection). The intensity maximum and the maximum of the upward
line-of-sight velocity do not coincide. In most cases the maximum of
the velocity lies near the border of the granule and falls rapidly to
the adjacent intergranular lane(from 1.5 to 0.2kmsec(-1) over 200km),
but moderately towards the other intergranular lane. In some granules
the position with zero velocity coincides with the position of highest
intensity, whereas maxima of velocities with different signs lie at
their border, thus reflecting a typical velocity profile of a rotating
eddy. The low correlation(of less than 0.5) between intensity and
Doppler velocity fluctuations along the spectrograph slit reflects
the asymmetric character of the solar granular flow. Concerning
the border of granules we find that bright regions often exhibit
downward, instead of the expected upward velocity. Moreover, by
investigating the broadening of a non-magnetically sensitive line,
we were able to localize regions with enhanced turbulence within the
intergranular space. We find that these regions do not always cover
the whole intergranular lane, but are concentrated at the border of
the granules, especially where the steep decrease of the velocity
takes place. On the basis of these findings we suggest that a typical
granule consists of a region of high intensity and low turbulence in
its interior and a region of high turbulence and moderate intensity
at its border. In other words, we surmise that regions of enhanced
turbulence outline the borders of granules. Using our time series
of spectrograms, which were taken every 15sec over a total of 5min,
we followed the dynamics of these properties and the evolution of the
steep intensity and velocity changes along the slit. These changes
are connected with shear instabilities and turbulence production. The
findings from non-active regions will be compared with those from
active regions based on magnetically sensitive lines.
Title: Solar Granulation Spectroscopy: Dynamics of the Intergranular
Space
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Mattig, R. Komm W.;
Staiger, J.
Bibcode: 1992ASPC...26..181N
Altcode: 1992csss....7..181N
No abstract at ADS
Title: Dynamics of the solar granulation. I - A phenomenological
approach
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig,
W.; Staiger, J.
Bibcode: 1992A&A...253..561N
Altcode:
High-spatial-resolution spectrograms taken with the vacuum tower
telescope in Tenerife were used to investigate the dynamics of the deep
photospheric layers by tracing the motions of small-scale structures
such as granulation. Based on a time series of these spectrograms,
traces of line Doppler shifts were detected which show strong
asymmetries within solar granules. The results are discussed within
the framework of different granulation flow models.
Title: Bisector; Line Parameter Variation Over a Single Solar Granulum
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1992ASPC...26..168H
Altcode: 1992csss....7..168H
No abstract at ADS
Title: Die turbulente Sonnenoberfläche.
Authors: Hanslmeier, A.
Bibcode: 1992Sterb..35..126H
Altcode:
No abstract at ADS
Title: Die Feinstruktur der Sonnengranulation.
Authors: Hanslmeier, Arnold
Bibcode: 1991S&W....30..724H
Altcode:
High resolution observations of the solar granulation fine structure are
presented. Findings concerning the solar convection, line asymmetry,
bisectors resulting from line profiles, velocity and intensity
fluctuations, magnetic fields, and flow tubes are discussed. Bisectors
exhibit a red asymmetry in the intergrain region and a blue asymmetry in
the grain region. Photospheric plasma motions decrease with increasing
height. Small flow tubes are brighter than the surrounding photosphere.
Title: The variation of the solar granulation structure in active
and non-active regions
Authors: Hanslmeier, A.; Nesis, A.; Mattig, W.
Bibcode: 1991A&A...251..307H
Altcode:
With the aid of a coherence analysis between line-center velocities,
continuum-brightness variations and residual intensities the
height-dependent evolution of overshooting convective elements in
the solar photosphere is studied in magnetically active and nonactive
regions. Evidence of a structuring influence of the magnetic field on
the height dependent evolution of temperature and velocity patterns
is found. From a comparison of intensity and velocity-frequency
distributions in nonactive and active regions enhanced downward motions
in active regions were found. The results are in agreement with small
fluxtube concepts.
Title: Selected examples of bisector and line parameter variation
over a granular-intergranular region
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1991A&A...251..669H
Altcode:
Four examples of bisector and corresponding line parameter variations
over a granular-intergranular region are discussed. These detailed
case studies permit a direct comparison with hydrodynamical model
calculations. Generally, the variation of the line parameters is found
to be more similar than for data where granular and intergranular areas
are averaged. However, the transition from granulum to intergranulum
was found to be nonmonotonic and at the position where the velocity
gradients reach a minimum, the slope of the line parameter curves
also changes.
Title: Granular and intergranular line profiles in solar active and
quiet regions
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1991A&A...248..232H
Altcode:
Two spectra obtained with high spatial resolution in active and
nonactive regions of the sun have been analyzed. The enhanced
fluctuations at subgranular scales in active regions observed in
the power spectra of intensity and velocity, provide evidence for
the existence of small magnetic flux tubes. Using the brightest and
darkest continuum, intensity as indicators for granulum-intergranulum,
granular and intergranular line profiles have been determined. In Ca(+)
active regions, the intergranular profiles are changed more than
the granular profiles. Also the full width at half maximum of the
intergranular line profiles is enhanced in the active region. These
results have been obtained without any polarization equipment and
suggest that the magnetic elements are predominantly located in the
intergranular regions.
Title: High spatial resolution solar photospheric line observations
in Ca(+) active regions
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1991A&A...244..521H
Altcode:
Spatially highly resolved solar photospheric line profiles are
analyzed by calculating bisectors, line center velocities, and line
asymmetries in order to investigate the influence of magnetic fields
on these parameters. A set of three spectrograms containing regions
of different magnetic activity is used. In the active regions, a
reduction of continuum intensity fluctuations as well as small-scale
velocity fluctuations is confirmed; however, on subgranual scales,
the continuum intensity fluctuations and line center velocities for
the lines originating higher than 200 km in the troposphere are found
to be increasing in active regions and becoming equal to or higher
than those in nonactive regions. Significant changes are observed in
the profiles: the mean line asymmetry is negative in the nonactive
regions and positive with a reduction of the standard deviation in
the active regions.
Title: Granulation Spectroscopy: First Results from VTT-Tenerife
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig,
W.; Staiger, J.
Bibcode: 1991BAAS...23R1048N
Altcode:
No abstract at ADS
Title: A comparison of velocity and intensity power spectra in
Ca+ active and non active regions
Authors: Hanslmeier, A.; Mattig, W.
Bibcode: 1991AdSpR..11e.263H
Altcode: 1991AdSpR..11..263H
From an analysis of velocity powerspectra we found for scales smaller
than 800km that the power in magnetically active regions exceeded the
power in magnetically non active regions. This is in agreement with
the flux tube concept, predicting the confinement of the magnetic
field in small filigree structures. We also found evidence for an
increase of the velocity power contribution at small scales in AR with
photospheric height.
Title: Spatially highly resolved line parameters in active and non
active regions.
Authors: Hanslmeier, A.
Bibcode: 1991joso.proc.....H
Altcode:
From a comparison of line parameters obtained from high spatial
resolution spectra in non active and active solar photospheric regions
information about small spatial scale magnetic fine structures and
the influence of magnetic fields on the convective motions are obtained.
Title: On the Dynamics of Granulation in Active Regions and the
Heating Problem (With 2 Figures)
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.
Bibcode: 1991mcch.conf...36N
Altcode:
No abstract at ADS
Title: High spatial resolution observations of some solar photospheric
line profiles
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1990A&A...238..354H
Altcode:
Results are presented of high resolution spectroscopic solar granulation
observations with the Gregory Coude Telescope at Izana (Tenerife) in
photospheric nonactive regions. Line asymmetries of four Fe I lines were
analyzed depending on their origination in granular or intergranular
regions. With the increased spatial resolution, instead of the classical
C-shape, red line asymmetries are found in the intergranulum and
blue line asymmetries in the granulum. Correlations between various
line parameters such as continuum intensity, line center velocity,
and equivalent width were examined. The results are in agreement with
theoretical model calculations.
Title: Line asymmetries in Ca+-active regions
Authors: Hanslmeier, A.; Mattig, W.
Bibcode: 1990Ap&SS.170...51H
Altcode:
Spatially-resolved Fe i line bisectors were studied in magnetically
active and non-active regions. In active regions, small-scale velocities
which are of convective origin, were reduced by a factor of 1.9 and
individual bisectors originating in granular-intergranular regions
showed a different behaviour.
Title: Observations of Line Asymmetries with a 2-D Diode Array
Authors: Hanslmeier, A.; Wittmann, A. D.; Mattig, W.
Bibcode: 1990Ap&SS.170...47H
Altcode:
From two-dimensional Reticon spectra obtained at the Gregory Coudé
Telescope (Tenerife) two Fei lines were studied. It is shown that
the resultant line bisectors could be separated according to their
origination in granular-intergranular regions and that the resolved
bisectors no longer had a C-shape form.
Title: The decay process of the granulation and its influence on
the absorption lines.
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.
Bibcode: 1990AGAb....5...33N
Altcode:
No abstract at ADS
Title: The Influence of the Granulation on the Absorption Lines
I. Nonactive Regions
Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.
Bibcode: 1990PDHO....7..108N
Altcode: 1990ESPM....6..108N; 1990dysu.conf..108N
No abstract at ADS
Title: Influence of Magnetic Fields on Temperature Inhomogeneities
Authors: Hanslmeier, A.; Mattig, W.
Bibcode: 1990PDHO....7..102H
Altcode: 1990dysu.conf..102H; 1990ESPM....6..102H
No abstract at ADS
Title: On the line asymmetry distribution in solar Ca+
active and non active regions.
Authors: Hanslmeier, A.; Mattig, W.
Bibcode: 1990AGAb....5...39H
Altcode:
No abstract at ADS
Title: Pole-equator-difference of the size of the chromospheric CA
II-K-network in quiet and active solar regions
Authors: Muenzer, H.; Schroeter, E. H.; Woehl, H.; Hanslmeier, A.
Bibcode: 1989A&A...213..431M
Altcode:
The dependence of the size of chromospheric network cells on latitude
was investigated for quiet and active solar regions. Calibrated
photographic Ca II K-filtergrams were used and a Fast Fourier Transform
analysis was performed to obtain the cell size. Among other reductions
the results had to be corrected for seeing effects. A significant
decrease of the cell size toward higher latitudes and an increase with
locally increasing magnetic activity was found.
Title: Granulation Line Asymmetries
Authors: Mattig, W.; Hanslmeier, A.; Nesis, A.
Bibcode: 1989ASIC..263..187M
Altcode: 1989ssg..conf..187M
No abstract at ADS
Title: Dependence of solar line bisectors on equivalent widths.
Authors: Hanslmeier, A.; Mattig, W.; Nesis, A.
Bibcode: 1989sasf.confP.251H
Altcode: 1988sasf.conf..251H; 1989IAUCo.104P.251H
Spectroscopic highly resolved solar granulation observations lead to
intense line asymmetries for rising and sinking elements. In order to
average several granules it is better to use equivalent widths than
continuum intensities.
Title: Verlauf der Gesamthelligkeit des Mondes während der totalen
Mondfinsternis vom 17. August 1989.
Authors: Hanslmeier, A.; Stangl, M.
Bibcode: 1989OAWMN.126..109H
Altcode:
A magnitude decrease of 10m for the totally eclipsed moon
during the total eclipse of Aug 17, 1989 is observed.
Title: High Resolution Granulation Spectroscopy with a 100x100 RETICON
Authors: Hanslmeier, A.; Wittmann, A.
Bibcode: 1989AGAb....3...11H
Altcode:
No abstract at ADS
Title: Mass Flow Measurements around a Sunspot
Authors: Hanslmeier, A.
Bibcode: 1989AGAb....3....8H
Altcode:
No abstract at ADS
Title: Intensity-Velocity Correlation in active and non-active
solar areas
Authors: Hanslmeier, A.; Mattig, W.
Bibcode: 1989AGAb....3....7H
Altcode:
No abstract at ADS
Title: Pole-Equator Difference of the Size of the Chromospheric Ca
II-K Network in Quiet and Active Solar Regions
Authors: Münzer, H.; Hanslmeier, A.; Schröter, E. H.; Wöhl, H.
Bibcode: 1989ASIC..263..217M
Altcode: 1989ssg..conf..217M
No abstract at ADS
Title: Photoelectric five-colour photometry of the asteroids 16
Psyche, 201 Penelope and 702 Alauda
Authors: Pfleiderer, J.; Pfleiderer, M.; Hanslmeier, A.
Bibcode: 1987A&AS...69..117P
Altcode:
UBVRI photometry of 16 Psyche, 201 Penelope, and 702 Alauda have
yielded light curves, colour indices, periods and phase effects. We
find evidence for selective absorption on the planetoidal surfaces,
and a rather uncertain indication of a large directively reflecting
surface feature on Penelope.
Title: Meridional motions of sunspots from 1947.9 to 1985.0. II -
Latitude motions dependent on SPOT type and phase of the activity
cycle
Authors: Lustig, G.; Hanslmeier, A.
Bibcode: 1987A&A...172..332L
Altcode:
The dependence of the meridional motions of sunspots on sunspot-type
and phase in the solar activity cycle for the time interval
1947.9-1985.0 is examined; this was done also with the sunspot data
from the solar-observatory Kanzelhoehe. For the total time interval,
investigations for each cycle were carried out only for the elder
or long lasting G, H, and J sunspot groups and distinctions between
similar sunspot types AB, C, D, EF, GHJ (Zuerich-classification). The
meridional motions about the different activity maxima were also
examined. In all investigations in the period from 1947.9 to 1985.0 a
tendency to a southdrift can be observed on both hemispheres of the
sun, but the mean meridional motions are between the error-bars not
very significantly different from zero.
Title: H-alpha and LiI Observations of the RS CVn Type Binaries:
sigma Gem, alpha Aur, 93 Leo and HR 6469
Authors: Strassmeier, K. G.; Weichinger, S.; Hanslmeier, A.
Bibcode: 1986IBVS.2937....1S
Altcode:
No abstract at ADS
Title: Rotation und meridionale Strömungen auf der Sonne
Authors: Hanslmeier, A.; Lustig, G.; Wöhl, H.
Bibcode: 1986MitAG..67..285H
Altcode:
No abstract at ADS
Title: Meridional motions of sunspots from 1947.9-1985.0. I -
Latitude drift at the different solar-cycles
Authors: Hanslmeier, A.; Lustig, G.
Bibcode: 1986A&A...154..227H
Altcode:
Sunspot data from 1947.9-1985.0 have been analyzed for meridional
sunspot motions. While during cycles 18, 19, and 20 a general southward
drift is noted for spots in regions near the equator, the cycle 21
drifts are within error bars, indicating no significant change. The
rotation rate is also presently determined for each cycle and for the
total interval of the data.
Title: Das Problem der Sonnenneutrinos.
Authors: Hanslmeier, A.
Bibcode: 1986Stern..62..139H
Altcode:
The problem of solar neutrinos is a very serious challenge to our
"classical" views about the internal constitution and energy production
of the Sun and the stars. The measured neutrino flux emerging from
the Sun shows a discrepancy between theory and observation. Several
explanations and hypotheses are discussed in this article and compared
with current theories about stellar formation and evolution.
Title: Lichtelektrische Photometrie dreier Kleinplaneten
Authors: Pfleiderer, M.; Hanslmeier, A.
Bibcode: 1986MitAG..67..275P
Altcode:
No abstract at ADS
Title: New cases of ambiguity among large asteroids' spin rates
Authors: Zappala, V.; Martino, M. Di.; Hanslmeier, A.; Schober, H. J.
Bibcode: 1985A&A...147...35Z
Altcode:
New observational evidence supports the importance of the ambiguity
problem about determination of the spin rate of asteroids. In the
range of objects larger than about 150 km, where equilibrium figures
are thought to exist, and therefore where irregular fragments should
be absent, four cases of periods shorter by a factor two than the
previously adopted values, believed unambiguous, were recently
found. This paper presents results for two of them (409 Aspasia and
423 Diotima), attempting to give plausible physical interpretations,
but admitting that a quantitative explanation cannot be reached with
the present knowledge of the asteroids' surface morphology. Still, the
discrepancies found in preliminary analyses seem to be satisfactorily
overcome.
Title: Geisterteilchen von der Sonne: Sonnen-Neutrinos.
Authors: Hanslmeier, A.
Bibcode: 1985Sterb..28..202H
Altcode:
No abstract at ADS
Title: Photoelektrische Photometrie den Kleinplaneten 115 Thyra.
Authors: Hanslmeier, A.; Denzel, R.
Bibcode: 1985OAWMN.122..151H
Altcode:
The asteroid (115) Thyra was observed photoelectrically at the
Leopold-Figl-Observatory. The rotation period (the authors found is
7h.244) differs by 0h.003 from the value given
by Scaltriti et al. (1981) and the amplitudes of the lightcurves
are approximately 0m.06 smaller than the amplitudes found
earlier.
Title: Application of Lie Series to Regularized Problems in Celestial
Mechanics
Authors: Hanslmeier, A.
Bibcode: 1984CeMec..34..135H
Altcode:
In the following paper we tried to apply the Lie-formalism to the
regularized restricted three body problem. It will be shown that this
algorithm leads to a very simple structure program which is also fast.
Title: Numerical Integration with Lie Series
Authors: Hanslmeier, A.; Dvorak, R.
Bibcode: 1984A&A...132..203H
Altcode:
The aim of this work is the construction of a fast integration method
for differential equations (DE), especially the equations of the
motion of celestial bodies. Although a number of integration schemes
are available none of them seem to be adequate for treating n-body
systems with variable masses, which arise in some cosmogonic problems
of the early solar system. As a first step we are now able to present
a high-speed numerical integration scheme of the classical n-body
system. The basic idea of solving differential equations with Lie-series
is due to Grobner (1967) but, unfortunately, he did not elaborate
on this method and stopped after some numerically unsatisfactory
results. We could simplify the calculation of the Lie-terms and
derived finally a recurrence formula for the Lie-terms. Whereas
Grobner tried to solve the two-body and three (n-body)problem by
two different approaches we solved, at first, in an optimal way
the 2-body- problem. Then we were able to derive in a quite similar
way the solutions of the 3-body and n-body system. Our integration
method for planetary motions has two major advantages: First, it is
a relatively fast method (about the factor 3-10 faster in comparison
with the n-body program by Schubart-Stumpff, which is commonly used
by Astronomers). Second, because larger step lengths can be used,
roundoff errors are smaller (e.g. step length 135 d for Jupiter).
Title: Positionsbestimmungen der Kometen P/Encke und P/Crommelin.
Authors: Hanslmeier, A.; Ornig, W.; Ornig, C.
Bibcode: 1984OAWMN.121...63H
Altcode:
No abstract at ADS
Title: Photographische Positionen des Kleinplaneten 111 Ate.
Authors: Hanslmeier, A.; Jackson, P.
Bibcode: 1984OAWMN.121...15H
Altcode:
No abstract at ADS
Title: Photoelektrische Photometrie der Kleinplaneten (54) Alexandra
und (372) Palma.
Authors: Haupt, H.; Hanslmeier, A.
Bibcode: 1984OAWMN.121...69H
Altcode:
The asteroids (54) Alexandra and (372) Palma have been
observed photoelectrically with the 60 cm telescope of the
Leopold-Figl-Observatory. For (54) an amplitude of 0m.14 and
a Vmax = 10m.28 has been found. The period was
not observed in full but seems to agree with the previously published
one (P = 7h.04). A new period of 6h.58 has
been derived for (372) that seems not be in contradiction with earlier
observations. The amplitude was 0h.11 and the Vmax
= 11m.54.
Title: Lie-integration of planetary motions.
Authors: Dvorak, R.; Hanslmeier, A.; Lichtenegger, H.
Bibcode: 1983BAAS...15..869D
Altcode:
No abstract at ADS
Title: Anwendungen von Lie-Reihen als numerische Integrationsmethode
in der Himmelsmechanik Title: Anwendungen von Lie-Reihen als
numerische Integrationsmethode in der Himmelsmechanik Title:
Applications of Lie series as a numerical integration method in
celestial mechanics;
Authors: Hanslmeier, Arnold
Bibcode: 1983PhDT.......153H
Altcode:
No abstract at ADS
Title: Numerical Integration with Lie-Series
Authors: Dvorak, R.; Hanslmeier, A.
Bibcode: 1983mpna.conf...65D
Altcode:
Lie-series are applicated to the two body and the general three body
problem as a numerical integration method. Since it is easy to compute
even higher Lie-terms bigger step length can be used in order to save
computing time as well as to keep small round off errors. As shown
in a simple example also non-conservative systems can be treated with
the Lie-integration.
Title: Application of Lie-Series to Numerical Integration in
Celestial Mechanics
Authors: Hanslmeier, A.; Dvorak, R.
Bibcode: 1982ASIC...82..345H
Altcode: 1982amdc.proc..345H
No abstract at ADS
Title: Der Rotationslichtwechsel des Kleinplaneten 409 Aspasia.
Authors: Hanslmeier, A.
Bibcode: 1982OAWMN.119Q...5H
Altcode:
The minor planet 409 Aspasia was observed during the 1981 opposition
with a photoelectric photometry attached to the 1 m telescope of the
Observatoire de Haute Provence on 4 consecutive nights. The composite
lightcurve shows two different maxima and gives a period of 16h45m
± 4m. The amplitudes of the two different maxima are 0m.1 and 0m.14
respectively.
Title: Der Rotationslichtwechsel des Kleinplaneten 409 Aspasia.
Authors: Hanslmeier, A.
Bibcode: 1982OAWMN.119R...5H
Altcode:
No abstract at ADS
Title: 14 Irene - A puzzling asteroid
Authors: Scaltriti, F.; Zappala, V.; Schober, H. J.; Hanslmeier, A.;
Sudy, A.; Piironen, J.; Blanco, C.; Catalano, S.
Bibcode: 1981A&A...100..326S
Altcode:
Photoelectric observations of the asteroid 14 Irene made during
three apparitions are analyzed to derive rotational properties. Some
ambiguous results for the rotational periods are obtained due to
the small amplitude of the light curve. Two hypotheses are formed,
which are given the same probability and value the synodic period
as P(1) equals 9.35 h and P(2) equals 18.71 h. Total amplitude is
found to reach a maximum of 0.10 mag at 90 deg of aspect, and the
magnitude-phase relation is obtained. All aspect data, magnitudes and
colors of existing observations are presented, and the hypotheses are
found to satisfy these previous results.
Title: Langsam rotierende Kleinplaneten I: 14 Irene und 60 Echo
Authors: Hanslmeier, A.; Schober, H. J.; Sudy, A.
Bibcode: 1981MitAG..52Q..89H
Altcode:
No abstract at ADS