Author name code: cauzzi
ADS astronomy entries on 2022-09-14
author:"Cauzzi, Gianna"
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Title: Development of Integral Field Spectrographs to Revolutionize
Spectroscopic Observations of Solar Flares and other Energetic
Solar Eruptions
Authors: Lin, Haosheng; Anan, Tetsu; Cauzzi, Gianna; Fletcher, Lyndsay;
Huang, Pei; Kowalski, Adam; Kramar, Maxim; Qiu, Jiong; Samra, Jenna;
Spittler, Constance; Sukegawa, Takashi; Wirth, Gregory
Bibcode: 2022arXiv220900788L
Altcode:
The Sun's proximity offers us a unique opportunity to study in detail
the physical processes on a star's surface; however, the highly dynamic
nature of the stellar surface -- in particular, energetic eruptions
such as flares and coronal mass ejections -- presents tremendous
observational challenges. Spectroscopy probes the physical state of
the solar atmosphere, but conventional scanning spectrographs and
spectrometers are unable to capture the full evolutionary history of
these dynamic events with a sufficiently wide field of view and high
spatial, spectral, and temporal resolution. Resolving the physics of the
dynamic sun requires gathering simultaneous spectra across a contiguous
area over the full duration of these events, a goal now tantalizingly
close to achievable with continued investment in developing powerful
new Integral Field Spectrographs to serve as the foundation of both
future ground- and space-based missions. This technology promises to
revolutionize our ability to study solar flares and CMEs, addressing
NASA's strategic objective to "understand the Sun, solar system, and
universe." Since such events generate electromagnetic radiation and
high-energy particles that disrupt terrestrial electric infrastructure,
this investment not only advances humanity's scientific endeavors
but also enhances our space weather forecasting capability to protect
against threats to our technology-reliant civilization.
Title: IBIS-A: The IBIS data Archive. High-resolution observations
of the solar photosphere and chromosphere with contextual data
Authors: Ermolli, Ilaria; Giorgi, Fabrizio; Murabito, Mariarita;
Stangalini, Marco; Guido, Vincenzo; Molinaro, Marco; Romano, Paolo;
Guglielmino, Salvatore L.; Viavattene, Giorgio; Cauzzi, Gianna;
Criscuoli, Serena; Reardon, Kevin P.; Tritschler, Alexandra
Bibcode: 2022A&A...661A..74E
Altcode: 2022arXiv220209946E
Context. The IBIS data Archive (IBIS-A) stores data acquired with
the Interferometric BIdimensional Spectropolarimeter (IBIS), which
was operated at the Dunn Solar Telescope of the US National Solar
Observatory from June 2003 to June 2019. The instrument provided series
of high-resolution narrowband spectropolarimetric imaging observations
of the photosphere and chromosphere in the range 5800-8600 Å and
co-temporal broadband observations in the same spectral range and
with the same field of view as for the polarimetric data.
Aims: We present the data currently stored in IBIS-A, as well as the
interface utilized to explore such data and facilitate its scientific
exploitation. To this end, we also describe the use of IBIS-A data
in recent and undergoing studies relevant to solar physics and
space weather research.
Methods: IBIS-A includes raw and
calibrated observations, as well as science-ready data. The latter
comprise maps of the circular, linear, and net circular polarization,
and of the magnetic and velocity fields derived for a significant
fraction of the series available in the archive. IBIS-A furthermore
contains links to observations complementary to the IBIS data, such
as co-temporal high-resolution observations of the solar atmosphere
available from the instruments onboard the Hinode and IRIS satellites,
and full-disk multi-band images from INAF solar telescopes.
Results: IBIS-A currently consists of 30 TB of data taken with IBIS
during 28 observing campaigns performed in 2008 and from 2012 to 2019
on 159 days. Of the observations, 29% are released as Level 1 data
calibrated for instrumental response and compensated for residual seeing
degradation, while 10% of the calibrated data are also available as
Level 1.5 format as multi-dimensional arrays of circular, linear, and
net circular polarization maps, and line-of-sight velocity patterns;
81% of the photospheric calibrated series present Level 2 data with
the view of the magnetic and velocity fields of the targets, as derived
from data inversion with the Very Fast Inversion of the Stokes Vector
code. Metadata and movies of each calibrated and science-ready series
are also available to help users evaluate observing conditions.
Conclusions: IBIS-A represents a unique resource for investigating
the plasma processes in the solar atmosphere and the solar origin of
space weather events. The archive currently contains 454 different
series of observations. A recently undertaken effort to preserve
IBIS observations is expected to lead in the future to an increase in
the raw measurements and the fraction of processed data available in
IBIS-A. Research supported by the H2020 SOLARNET grant no. 824135.
Title: Subarcsecond Imaging of a Solar Active Region Filament With
ALMA and IRIS
Authors: da Silva Santos, J. M.; White, S. M.; Reardon, K.; Cauzzi,
G.; Gunár, S.; Heinzel, P.; Leenaarts, J.
Bibcode: 2022FrASS...9.8115D
Altcode: 2022arXiv220413178D
Quiescent filaments appear as absorption features on the solar disk
when observed in chromospheric lines and at continuum wavelengths
in the millimeter (mm) range. Active region (AR) filaments are their
small-scale, low-altitude analogues, but they could not be resolved
in previous mm observations. This spectral diagnostic can provide
insight into the details of the formation and physical properties of
their fine threads, which are still not fully understood. Here, we shed
light on the thermal structure of an AR filament using high-resolution
brightness temperature (Tb) maps taken with ALMA Band 6 complemented by
simultaneous IRIS near-UV spectra, Hinode/SOT photospheric magnetograms,
and SDO/AIA extreme-UV images. Some of the dark threads visible in the
AIA 304 Å passband and in the core of Mg ii resonance lines have dark
(Tb < 5,000 K) counterparts in the 1.25 mm maps, but their visibility
significantly varies across the filament spine and in time. These
opacity changes are possibly related to variations in temperature and
electron density in filament fine structures. The coolest Tb values
(< 5,000 K) coincide with regions of low integrated intensity in the
Mg ii h and k lines. ALMA Band 3 maps taken after the Band 6 ones do not
clearly show the filament structure, contrary to the expectation that
the contrast should increase at longer wavelengths based on previous
observations of quiescent filaments. The ALMA maps are not consistent
with isothermal conditions, but the temporal evolution of the filament
may partly account for this.
Title: A Prototype of a Large Tunable Fabry-Pérot Interferometer
for Solar Spectroscopy
Authors: Greco, V.; Sordini, A.; Cauzzi, G.; Cavallini, F.; Del
Vecchio, C.; Giovannelli, L.; Berrilli, F.; Del Moro, D.; Reardon,
K.; Pietraszewski, K. A. R. B.
Bibcode: 2022PASP..134a5007G
Altcode: 2021arXiv211202224G
Large Fabry-Pérot Interferometers (FPIs) are used in a variety of
astronomical instrumentation, including spectro-polarimeters for 4 m
class solar telescopes. In this work we comprehensively characterize
the cavity of a prototype 150 mm FPI, sporting a novel, fully symmetric
design. Of particular interest, we define a new method to properly
assess the gravity effects on the interferometer's cavity when the
system is used in either the vertical or horizontal configuration,
both typical of solar observations. We show that the symmetric design
very effectively limits the combined effects of pre-load and gravity
forces to only a few nm over a 120 mm diameter illuminated surface,
with gravity contributing ~2 nm peak-to-valley (~0.3 nm rms) in either
configuration. We confirm a variation of the tilt between the plates
of the interferometer during the spectral scan, which can be mitigated
with appropriate corrections to the spacing commands. Finally, we show
that the dynamical response of the new system fully satisfies typical
operational scenarios. We conclude that large, fully symmetric FPIs
can be safely used within solar instrumentation in both, horizontal
and vertical position, with the latter better suited to limiting the
overall volume occupied by such an instrument.
Title: The National Science Foundation's Daniel K. Inouye Solar
Telescope — Status Update
Authors: Rimmele, T.; Woeger, F.; Tritschler, A.; Casini, R.; de Wijn,
A.; Fehlmann, A.; Harrington, D.; Jaeggli, S.; Anan, T.; Beck, C.;
Cauzzi, G.; Schad, T.; Criscuoli, S.; Davey, A.; Lin, H.; Kuhn, J.;
Rast, M.; Goode, P.; Knoelker, M.; Rosner, R.; von der Luehe, O.;
Mathioudakis, M.; Dkist Team
Bibcode: 2021AAS...23810601R
Altcode:
The National Science Foundation's 4m Daniel K. Inouye Solar Telescope
(DKIST) on Haleakala, Maui is now the largest solar telescope in the
world. DKIST's superb resolution and polarimetric sensitivity will
enable astronomers to unravel many of the mysteries the Sun presents,
including the origin of solar magnetism, the mechanisms of coronal
heating and drivers of flares and coronal mass ejections. Five
instruments, four of which provide highly sensitive measurements
of solar magnetic fields, including the illusive magnetic field of
the faint solar corona. The DKIST instruments will produce large and
complex data sets, which will be distributed through the NSO/DKIST Data
Center. DKIST has achieved first engineering solar light in December
of 2019. Due to COVID the start of the operations commissioning phase
is delayed and is now expected for fall of 2021. We present a status
update for the construction effort and progress with the operations
commissioning phase.
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
Bibcode: 2021SoPh..296...70R
Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
Title: Measuring Decay Timescales of Downflows in Solar Flare
Footpoints: Testing the One-minute Theory (Abstract)
Authors: Beltzer-Sweeney, A. K.; Butler, E.; Kowalski, A.; Cauzzi, G.
Bibcode: 2020JAVSO..48R.107B
Altcode:
(Abstract only) In 1989 George Fisher found analytically that
chromospheric downflows in flare footprints should slow down to
background detection levels within ~ 1 minute regardless of the initial
energy injected. We set to test this theory by measuring downflows in
flare kernels that were observed by the IRIS satellite between 2014
and 2017. The GOES classification system was used as a proxy for
the energy of the nonthermal electron beam that is thought to heat
the flare footprint. The redshift evolution of a Mg II triplet line
was measured in twenty-six C, M, and X class flares to determine the
timescale of deceleration of the chromospheric plasma in response to
explosive flare heating. Two different methods for measuring the decay
of the redshift as a function of time, bisector and gaussian, were
used to test the robustness of the inferred downflow gas velocities
across the wide variety of flares. Results of the analysis show
that downflow velocities reached 30 ~ 50 km/s, which is consistent
with previous results with a derived Mach number of 4 ~ 5. The times
of half-maximum velocity were found to be between 15 ~ 30 seconds,
indicating a rapid slowing. At later times, the Mg II line profiles
exhibit prolonged redshifts with inferred speeds of 5 to 7 km/s.
Title: Spectral Signatures of Chromospheric Condensation in a Major
Solar Flare
Authors: Graham, David R.; Cauzzi, Gianna; Zangrilli, Luca; Kowalski,
Adam; Simões, Paulo; Allred, Joel
Bibcode: 2020ApJ...895....6G
Altcode: 2020arXiv200405075G
We study the evolution of chromospheric line and continuum emission
during the impulsive phase of the X-class SOL2014-09-10T17:45
solar flare. We extend previous analyses of this flare to multiple
chromospheric lines of Fe I, Fe II, Mg II, C I, and Si II observed
with the Interface Region Imaging Spectrograph, combined with
radiative-hydrodynamical (RHD) modeling. For multiple flaring kernels,
the lines all show a rapidly evolving double-component structure: an
enhanced emission component at rest, and a broad, highly redshifted
component of comparable intensity. The redshifted components migrate
from 25 to 50 km s-1 toward the rest wavelength within ∼30
s. Using Fermi hard X-ray observations, we derive the parameters of
an accelerated electron beam impacting the dense chromosphere, using
them to drive an RHD simulation with the RADYN code. As in Kowalski
et al. (2017), our simulations show that the most energetic electrons
penetrate into the deep chromosphere, heating it to T ∼ 10,000 K,
while the bulk of the electrons dissipate their energy higher, driving
an explosive evaporation, and its counterpart condensation—a very
dense (ne ∼ 2 × 1014 cm-3), thin
layer (30-40 km thickness), heated to 8-12,000 K, moving toward the
stationary chromosphere at up to 50 km s-1. The synthetic
Fe II 2814.45 Å profiles closely resemble the observational
data, including a continuum enhancement, and both a stationary
and a highly redshifted component, rapidly moving toward the rest
wavelength. Importantly, the absolute continuum intensity, ratio
of component intensities, relative time of appearance, and redshift
amplitude are sensitive to the model input parameters, showing great
potential as diagnostics.
Title: Solar physics in the 2020s: DKIST, parker solar probe, and
solar orbiter as a multi-messenger constellation
Authors: Martinez Pillet, V.; Tritschler, A.; Harra, L.; Andretta, V.;
Vourlidas, A.; Raouafi, N.; Alterman, B. L.; Bellot Rubio, L.; Cauzzi,
G.; Cranmer, S. R.; Gibson, S.; Habbal, S.; Ko, Y. K.; Lepri, S. T.;
Linker, J.; Malaspina, D. M.; Matthews, S.; Parenti, S.; Petrie, G.;
Spadaro, D.; Ugarte-Urra, I.; Warren, H.; Winslow, R.
Bibcode: 2020arXiv200408632M
Altcode:
The National Science Foundation (NSF) Daniel K. Inouye Solar Telescope
(DKIST) is about to start operations at the summit of Haleakala
(Hawaii). DKIST will join the early science phases of the NASA
and ESA Parker Solar Probe and Solar Orbiter encounter missions. By
combining in-situ measurements of the near-sun plasma environment and
detail remote observations of multiple layers of the Sun, the three
observatories form an unprecedented multi-messenger constellation to
study the magnetic connectivity inside the solar system. This white
paper outlines the synergistic science that this multi-messenger
suite enables.
Title: Measuring Decay Timescales of Downflows in Solar Flare
Footpoints: Testing the 1-minute Theory
Authors: Beltzer-Sweeney, A. K.; Butler, E.; Kowalski, A. F.;
Cauzzi, G.
Bibcode: 2019AGUFMSH13D3423B
Altcode:
In 1989 George Fisher found analytically that chromospheric downflows in
flare footprints should slow down to background detection levels within
~1 minute regardless of the initial energy injected. We set to test
this theory by measuring downflows in flare kernels that were observed
by the IRIS satellite between 2014-2017. The GOES classification system
was used as a proxy for the energy of the nonthermal electron beam
that is thought to heat the flare footprint. The redshift evolution
of a Mg II triplet line was measured in twenty-six C, M, and X class
flares to determine the timescale of deceleration of the chromospheric
plasma in response to explosive flare heating. Two different methods
for measuring the decay of the redshift as a function of time, bisector
and gaussian, were used to test the robustness of the inferred downflow
gas velocities across the wide variety of flares. Results of the
analysis show that downflow velocities reached 30~50 km/s, which is
consistent with previous results with a derived Mach number of 4~5. The
times of half-maximum velocity were found to be between 15~30 seconds,
indicating a rapid slowing. At later times, the Mg II line profiles
exhibit prolonged redshifts with inferred speeds of 5-7 km/s.
Title: IBIS-A: The IBIS Solar Spectro-polarimetric Data Archive
Authors: Ermolli, Ilaria; Giordano, Silvio; Giorgi, Fabrizio; Guido,
Vincenzo; Marassi, Alessandro; Volpicelli, Antonio; Di Marcantonio,
Paolo; Zuccarello, Francesca; Cauzzi, Gianna
Bibcode: 2019ASPC..521..431E
Altcode:
We review the efforts undertaken to set up the archive of the IBIS
ground-based solar spectro-polarimetric observations into the VO
framework, according to the SOLARNET standards, by using SOAP/XML and
RESTful Web Services.
Title: Solar Chromospheric Temperature Diagnostics: A Joint ALMA-Hα
Analysis
Authors: Molnar, Momchil E.; Reardon, Kevin P.; Chai, Yi; Gary, Dale;
Uitenbroek, Han; Cauzzi, Gianna; Cranmer, Steven R.
Bibcode: 2019ApJ...881...99M
Altcode: 2019arXiv190608896M
We present the first high-resolution, simultaneous observations of
the solar chromosphere in the optical and millimeter wavelength
ranges, obtained with the Atacama Large Millimeter Array (ALMA)
and the Interferometric Bidimensional Spectrometer at the Dunn Solar
Telescope. In this paper we concentrate on the comparison between the
brightness temperature observed in ALMA Band 3 (3 mm; 100 GHz) and the
core width of the Hα 6563 Å line, previously identified as a possible
diagnostic of the chromospheric temperature. We find that in the area
of plage, network and fibrils covered by our field of view, the two
diagnostics are well correlated, with similar spatial structures
observed in both. The strength of the correlation is remarkable,
given that the source function of the millimeter radiation obeys local
thermodynamic equilibrium, while the Hα line has a source function that
deviates significantly from the local Planck function. The observed
range of ALMA brightness temperatures is sensibly smaller than the
temperature range that was previously invoked to explain the observed
width variations in Hα. We employ analysis from forward modeling
with the Rybicki-Hummer (RH) code to argue that the strong correlation
between Hα width and ALMA brightness temperature is caused by their
shared dependence on the population number n 2 of the first
excited level of hydrogen. This population number drives millimeter
opacity through hydrogen ionization via the Balmer continuum, and
Hα width through a curve-of-growth-like opacity effect. Ultimately,
the n 2 population is regulated by the enhancement or lack
of downward Lyα flux, which coherently shifts the formation height
of both diagnostics to regions with different temperature, respectively.
Title: New technique to measure the cavity defects of Fabry-Perot
interferometers
Authors: Greco, V.; Sordini, A.; Cauzzi, G.; Reardon, K.; Cavallini, F.
Bibcode: 2019A&A...626A..43G
Altcode: 2019arXiv190501393G
Context. Several astronomical instruments, for both nighttime and
solar use, rely on tunable Fabry-Perot interferometers (FPIs). Knowing
the exact shape of the etalons' cavity is crucial for assessing the
overall instrumental transmission profile and its possible variations
during the tuning process.
Aims: We aim to define and test
a technique to accurately measure the cavity defects of air-spaced
FPIs, including distortions due to the spectral tuning process that
are typical of astronomical observations. We further aim to develop a
correction technique to maintain the shape of the cavity as constant as
possible during the spectral scan. These are necessary steps to optimize
the spectral transmission profile of a two-dimensional spectrograph
(polarimeter) using one or more FPIs in series, and to ensure that
the spectral transmission profile remains constant during typical
observing conditions.
Methods: We devised a generalization of the
techniques developed for the so-called phase-shifting interferometry to
the case of FPI. This measuring technique is applicable to any given FPI
that can be tuned via changing the cavity spacing (z-axis), and can be
used for any etalon regardless of the coating' reflectivity. The major
strength of our method is the ability to fully characterize the cavity
during a spectral scan, allowing for the determination of scan-dependent
modifications of the plates. We have applied the measuring technique to
three 50 mm diameter interferometers, with cavity gaps ranging between
600 μm and 3 mm, coated for use in the visible range.
Results:
The technique developed in this paper allows us to accurately and
reliably measure the cavity defects of air-spaced FPIs, and of their
evolution during the entire spectral scan. Our main, and unexpected,
result is that the relative tilt between the two FPI plates varies
significantly during the spectral scan, and can dominate the cavity
defects; in particular, we observe that the tilt component at the
extremes of the scan is sensibly larger than that at the center of
the scan. Exploiting the capability of the electronic controllers to
set the reference plane at any given spectral step, we then develop
a correction technique that allows the minimization of the tilt
during a complete spectral scan. The correction remains highly stable
over long periods, well beyond the typical duration of astronomical
observations. Movies attached to Figs. 6 and 13 are available at https://www.aanda.org
Title: Spectral Evidence for Heating at Large Column Mass in Umbral
Solar Flare Kernels. I. IRIS Near-UV Spectra of the X1 Solar Flare
of 2014 October 25
Authors: Kowalski, Adam F.; Butler, Elizabeth; Daw, Adrian N.;
Fletcher, Lyndsay; Allred, Joel C.; De Pontieu, Bart; Kerr, Graham S.;
Cauzzi, Gianna
Bibcode: 2019ApJ...878..135K
Altcode: 2019arXiv190502111K
The GOES X1 flare SOL2014-10-25T17:08:00 was a three-ribbon solar
flare observed with the Interface Region Imaging Spectrograph (IRIS)
in the near-UV (NUV) and far-UV. One of the flare ribbons crossed
a sunspot umbra, producing a dramatic, ∼1000% increase in the NUV
continuum radiation. We comprehensively analyze the UV spectral data
of the umbral flare brightenings, which provide new challenges for
radiative-hydrodynamic modeling of the chromospheric velocity field and
the white-light continuum radiation. The emission line profiles in the
umbral flare brightenings exhibit redshifts and profile asymmetries,
but these are significantly smaller than in another, well-studied
X-class solar flare. We present a ratio of the NUV continuum intensity
to the Fe II λ2814.45 intensity. This continuum-to-line ratio is a
new spectral diagnostic of significant heating at high column mass
(log m/[g cm-2] > -2) during solar flares because the
continuum and emission line radiation originate from relatively similar
temperatures but moderately different optical depths. The full spectral
readout of these IRIS data also allow for a comprehensive survey of the
flaring NUV landscape: in addition to many lines of Fe II and Cr II, we
identify a new solar flare emission line, He I λ2829.91 (as previously
identified in laboratory and early-type stellar spectra). The Fermi/GBM
hard X-ray data provide inputs to radiative-hydrodynamic models (which
will be presented in Paper II) in order to better understand the large
continuum-to-line ratios, the origin of the white-light continuum
radiation, and the role of electron beam heating in the low atmosphere.
Title: High Resolution Observations of Chromospheric Condensation
Authors: Cauzzi, Gianna; Graham, David; Zangrilli, Luca; Kowalski, Adam
Bibcode: 2019shin.confE.180C
Altcode:
The chromospheric response to flaring can provide information on
the coronal magnetic reconnection processes driving the flare. In
particular, the evolution of the chromospheric condensation can
trace the site and size of episodes of energy release in the corona,
and inform on their duration. High resolution, spectrally resolved
observations of chromospheric lines and continua are necessary to fully
study this phenomenon. High cadence observations of chromospheric
condensation in small flaring kernels, derived from a multi-spectral
analysis of IRIS UV lines in a well-studied X1 flare, put some hard
constraints on these values. In particular, it is found that the
chromospheric signatures occurr sequentially in multiple distinct
positions, separated by only 0.3"
Title: The Critical Science Plan for DKIST
Authors: Rast, M.; Cauzzi, G.; Martinez Pillet, V.
Bibcode: 2019NCimC..42....7R
Altcode:
The 4-meter Daniel K. Inouye Solar Telescope is nearing completion on
Haleakala, Maui, with first light expected in 2020. In preparation
for early science, the National Solar Observatory is reaching out
to the solar community in order to define the critical science goals
for the first two years of DKIST operations. The overall aim of this
"Critical Science Plan" is to be ready, by start of operations, to
execute a set of observations that take full advantage of the DKIST
capabilities to address critical compelling science.
Title: IRIS Ultraviolet Spectral Properties of a Sample of X-Class
Solar Flares
Authors: Butler, Elizabeth; Kowalski, Adam; Cauzzi, Gianna; Allred,
Joel C.; Daw, Adrian N.
Bibcode: 2018AAS...23212101B
Altcode:
The white-light (near-ultraviolet (NUV) and optical) continuum emission
comprises the majority of the radiated energy in solar flares. However,
there are nearly as many explanations for the origin of the white-light
continuum radiation as there are white-light flares that have been
studied in detail with spectra. Furthermore, there are rarely robust
constraints on the time-resolved dynamics in the white-light emitting
flare layers. We are conducting a statistical study of the properties of
Fe II lines, Mg II lines, and NUV continuum intensity in bright flare
kernels observed by the Interface Region Imaging Spectrograph (IRIS),
in order to provide comprehensive constraints for radiative-hydrodynamic
flare models. Here we present a new technique for identifying bright
flare kernels and preliminary relationships among IRIS spectral
properties for a sample of X-class solar flares.
Title: Hα and Hβ emission in a C3.3 solar flare: comparison between
observations and simulations
Authors: Zuccarello, F.; Simoes, P. J. D. A.; Capparelli, V.; Fletcher,
L.; Romano, P.; Mathioudakis, M.; Cauzzi, G.; Carlsson, M.; Kuridze,
D.; Keys, P.
Bibcode: 2017AGUFMSH41A2742Z
Altcode:
This work is based on the analysis of an extremely rare set of
simultaneous observations of a C3.3 solar flare in the Hα and Hβ lines
at high spatial and temporal resolution, which were acquired at the
Dunn Solar Telescope. Images of the C3.3 flare (SOL2014-04-22T15:22)
made at various wavelengths along the Hα line profile by the
Interferometric Bidimensional Spectrometer (IBIS) and in the Hβ
with the Rapid Oscillations in the Solar Atmosphere (ROSA) broadband
imager are analyzed to obtain the intensity evolution. The analysis
shows that Hα and Hβ intensity excesses in three identified flare
footpoints are well correlated in time. In the stronger footpoints,
the typical value of the the Hα/Hβ intensity ratio observed is ∼
0.4 - 0.5, in broad agreement with values obtained from a RADYN non-LTE
simulation driven by an electron beam with parameters constrained by
observations. The weaker footpoint has a larger Hα/Hβ ratio, again
consistent with a RADYN simulation but with a smaller energy flux.
Title: Hα and Hβ Emission in a C3.3 Solar Flare: Comparison between
Observations and Simulations
Authors: Capparelli, Vincenzo; Zuccarello, Francesca; Romano, Paolo;
Simões, Paulo J. A.; Fletcher, Lyndsay; Kuridze, David; Mathioudakis,
Mihalis; Keys, Peter H.; Cauzzi, Gianna; Carlsson, Mats
Bibcode: 2017ApJ...850...36C
Altcode: 2017arXiv171004067C
The hydrogen Balmer series is a basic radiative loss channel from
the flaring solar chromosphere. We report here on the analysis of an
extremely rare set of simultaneous observations of a solar flare in the
{{H}}α and {{H}}β lines, at high spatial and temporal resolutions,
that were acquired at the Dunn Solar Telescope. Images of the C3.3 flare
(SOL2014-04-22T15:22) made at various wavelengths along the {{H}}α line
profile by the Interferometric Bidimensional Spectrometer (IBIS) and in
the {{H}}β with the Rapid Oscillations in the Solar Atmosphere (ROSA)
broadband imager are analyzed to obtain the intensity evolution. The
{{H}}α and {{H}}β intensity excesses in three identified flare
footpoints are well-correlated in time. We examine the ratio of {{H}}α
to {{H}}β flare excess, which was proposed by previous authors as
a possible diagnostic of the level of electron-beam energy input. In
the stronger footpoints, the typical value of the the {{H}}α /H β
intensity ratio observed is ∼0.4-0.5, in broad agreement with values
obtained from a RADYN non-LTE simulation driven by an electron beam
with parameters constrained (as far as possible) by observation. The
weaker footpoint has a larger {{H}}α /H β ratio, again consistent
with a RADYN simulation, but with a smaller energy flux. The {{H}}α
line profiles observed have a less prominent central reversal than is
predicted by the RADYN results, but can be brought into agreement if
the {{H}}α -emitting material has a filling factor of around 0.2-0.3.
Title: The Atmospheric Response to High Nonthermal Electron Beam
Fluxes in Solar Flares. I. Modeling the Brightest NUV Footpoints in
the X1 Solar Flare of 2014 March 29
Authors: Kowalski, Adam F.; Allred, Joel C.; Daw, Adrian; Cauzzi,
Gianna; Carlsson, Mats
Bibcode: 2017ApJ...836...12K
Altcode: 2016arXiv160907390K
The 2014 March 29 X1 solar flare (SOL20140329T17:48) produced bright
continuum emission in the far- and near-ultraviolet (NUV) and highly
asymmetric chromospheric emission lines, providing long-sought
constraints on the heating mechanisms of the lower atmosphere in
solar flares. We analyze the continuum and emission line data from
the Interface Region Imaging Spectrograph (IRIS) of the brightest
flaring magnetic footpoints in this flare. We compare the NUV spectra
of the brightest pixels to new radiative-hydrodynamic predictions
calculated with the RADYN code using constraints on a nonthermal
electron beam inferred from the collisional thick-target modeling of
hard X-ray data from Reuven Ramaty High Energy Solar Spectroscopic
Imager. We show that the atmospheric response to a high beam flux
density satisfactorily achieves the observed continuum brightness
in the NUV. The NUV continuum emission in this flare is consistent
with hydrogen (Balmer) recombination radiation that originates from
low optical depth in a dense chromospheric condensation and from the
stationary beam-heated layers just below the condensation. A model
producing two flaring regions (a condensation and stationary layers)
in the lower atmosphere is also consistent with the asymmetric Fe II
chromospheric emission line profiles observed in the impulsive phase.
Title: A Chromospheric Flare Model Consisting of Two Dynamical Layers:
Critical Tests from IRIS Data of Solar Flares
Authors: Kowalski, Adam; Allred, Joel C.; Daw, Adrian N.; Cauzzi,
Gianna; Carlsson, Mats; Inglis, Andrew; O'Neill, Aaron; Mathioudakis,
Mihalis; Uitenbroek, Han
Bibcode: 2017AAS...22933902K
Altcode:
Recent 1D radiative-hydrodynamic simulations of flares have shown that
a heated, chromospheric compression layer and a stationary layer, just
below the compression, are produced in response to high flux electron
beam heating. The hot blackbody-like continuum and redshifted intensity
in singly ionized chromospheric lines in these model predictions are
generally consistent with broad wavelength coverage spectra of M dwarf
flares and with high spectral resolution observations of solar flares,
respectively. We critically test this two-component chromospheric
flare model against the Fe II profiles and NUV continuum brightness
for several X-class solar flares observed with the Interface Region
Imaging Spectrograph (IRIS). We present several new predictions for
the Daniel K. Inoue Solar Telescope (DKIST).
Title: Flares In Time-Domain Surveys
Authors: Kowalski, Adam; Hawley, Suzanne; Davenport, James; Berlicki,
Arkadiusz; Cauzzi, Gianna; Fletcher, Lyndsay; Heinzel, Petr; Notsu,
Yuta; Loyd, Parke; Martinez Oliveros, Juan Carlos; Pugh, Chloe;
Schmidt, Sarah Jane; Karmakar, Subhajeet; Pye, John; Flaccomio, Ettore
Bibcode: 2016csss.confE.126K
Altcode:
Proceedings for the splinter session "Flares in Time-Domain Surveys"
convened at Cool Stars 19 on June 07, 2016 in Uppsala, Sweden. Contains
a two page summary of the splinter session, links to YouTube talks,
and a PDF copy of the slides from the presenters.
Title: Spectral analysis and modeling of solar flares chromospheric
condensation
Authors: Cauzzi, Gianna; Graham, David; Kowalski, Adam; Zangrilli,
Luca; Simoes, Paulo; Allred, Joel C.
Bibcode: 2016SPD....47.0609C
Altcode:
We follow up on our recent analysis of the X1.1 flare
SOL2014-09-10T17:45, where we studied the impulsive phase dynamics
of tens of individual flaring "kernels", in both coronal (Fe XXI)
and chromospheric (MgII) lines observed at high cadence with IRIS.We
concentrate here on the chromospheric aspect of the phenomenon,
extending the analysis to multiple spectral lines of Mg II, Fe II,
Si I, C II. We show that many flaring kernels display high velocity
downflows in the spectra of all these chromospheric lines, exhibiting
distinct, transient and strongly redshifted spectral components.From
modeling using RADYN with the thick-target interpretation, the presence
of two spectral components appears to be consistent with a high flux
beam of accelerated electrons, characterized by a hard spectrum. In
particular the highest energy electrons heat the denser, lower layers
of the atmosphere, while the bulk of the beam energy, deposited higher
in the atmosphere, is sufficient to produce chromospheric evaporation
with a corresponding condensation.
Title: FUV Continuum in Flare Kernels Observed by IRIS
Authors: Daw, Adrian N.; Kowalski, Adam; Allred, Joel C.; Cauzzi,
Gianna
Bibcode: 2016SPD....47.0604D
Altcode:
Fits to Interface Region Imaging Spectrograph (IRIS) spectra observed
from bright kernels during the impulsive phase of solar flares are
providing long-sought constraints on the UV/white-light continuum
emission. Results of fits of continua plus numerous atomic and molecular
emission lines to IRIS far ultraviolet (FUV) spectra of bright kernels
are presented. Constraints on beam energy and cross sectional area
are provided by cotemporaneous RHESSI, FERMI, ROSA/DST, IRIS slit-jaw
and SDO/AIA observations, allowing for comparison of the observed IRIS
continuum to calculations of non-thermal electron beam heating using
the RADYN radiative-hydrodynamic loop model.
Title: Commission 12: Solar Radiation and Structure
Authors: Cauzzi, Gianna; Shchukina, Nataliya; Kosovichev, Alexander;
Bianda, Michele; Brandenburg, Axel; Chou, Dean-Yi; Dasso, Sergio; Ding,
Ming-De; Jefferies, Stuart; Krivova, Natalie; Kuznetsov, Vladimir D.;
Moreno-Insertis, Fernando
Bibcode: 2016IAUTA..29..278C
Altcode:
Commission 12 of the International Astronomical Union encompasses
investigations of the internal structure and dynamics of the Sun,
the quiet solar atmosphere, solar radiation and its variability, and
the nature of relatively stable magnetic structures like sunspots,
faculae and the magnetic network. The Commission sees participation
of over 300 scientists worldwide.
Title: ADAHELI: exploring the fast, dynamic Sun in the x-ray, optical,
and near-infrared
Authors: Berrilli, Francesco; Soffitta, Paolo; Velli, Marco; Sabatini,
Paolo; Bigazzi, Alberto; Bellazzini, Ronaldo; Bellot Rubio, Luis
Ramon; Brez, Alessandro; Carbone, Vincenzo; Cauzzi, Gianna; Cavallini,
Fabio; Consolini, Giuseppe; Curti, Fabio; Del Moro, Dario; Di Giorgio,
Anna Maria; Ermolli, Ilaria; Fabiani, Sergio; Faurobert, Marianne;
Feller, Alex; Galsgaard, Klaus; Gburek, Szymon; Giannattasio, Fabio;
Giovannelli, Luca; Hirzberger, Johann; Jefferies, Stuart M.; Madjarska,
Maria S.; Manni, Fabio; Mazzoni, Alessandro; Muleri, Fabio; Penza,
Valentina; Peres, Giovanni; Piazzesi, Roberto; Pieralli, Francesca;
Pietropaolo, Ermanno; Martinez Pillet, Valentin; Pinchera, Michele;
Reale, Fabio; Romano, Paolo; Romoli, Andrea; Romoli, Marco; Rubini,
Alda; Rudawy, Pawel; Sandri, Paolo; Scardigli, Stefano; Spandre,
Gloria; Solanki, Sami K.; Stangalini, Marco; Vecchio, Antonio;
Zuccarello, Francesca
Bibcode: 2015JATIS...1d4006B
Altcode:
Advanced Astronomy for Heliophysics Plus (ADAHELI) is a project concept
for a small solar and space weather mission with a budget compatible
with an European Space Agency (ESA) S-class mission, including launch,
and a fast development cycle. ADAHELI was submitted to the European
Space Agency by a European-wide consortium of solar physics research
institutes in response to the "Call for a small mission opportunity
for a launch in 2017," of March 9, 2012. The ADAHELI project builds
on the heritage of the former ADAHELI mission, which had successfully
completed its phase-A study under the Italian Space Agency 2007 Small
Mission Programme, thus proving the soundness and feasibility of
its innovative low-budget design. ADAHELI is a solar space mission
with two main instruments: ISODY: an imager, based on Fabry-Pérot
interferometers, whose design is optimized to the acquisition of
highest cadence, long-duration, multiline spectropolarimetric images
in the visible/near-infrared region of the solar spectrum. XSPO: an
x-ray polarimeter for solar flares in x-rays with energies in the 15
to 35 keV range. ADAHELI is capable of performing observations that
cannot be addressed by other currently planned solar space missions,
due to their limited telemetry, or by ground-based facilities, due to
the problematic effect of the terrestrial atmosphere.
Title: IRIS observations of chromospheric evaporation in multiple,
individual flaring kernels
Authors: Cauzzi, Gianna; Graham, David; Zangrilli, Luca
Bibcode: 2015IAUGA..2257379C
Altcode:
We present new results from IRIS showing the dynamic evolution
of chromospheric evaporation in a flare ribbon, with the highest
temporal and spatial resolution to date. IRIS observed the entire
duration of an X-class event using a 9 second cadence 'sit and stare'
mode. As the ribbon brightened successively at new positions along
the slit, a unique impulsive phase evolution was observed for about 80
individual spatial pixels in both coronal (Fe XXI) and chromospheric
(MgII) lines.Each activation of a new footpoint kernel displays the
same initial coronal up-flows of up to ~350 km/s, co-temporal and
co-spatial with chromospheric downflows up to 40 km/s. This represents
one of the most convincing examples of the development and evolution
of chromospheric evaporation. Further, the temporal evolution of flows
is remarkably similar between all slit pixel positions, leading to
the conclusion that the time of energy deposition in any one footpoint
is short - between 30-60 seconds - and occurs in an area of less than
2". Surprisingly the Fe XXI flows are sustained for several minutes,
and significant line broadening beyond the thermal width is seen,
which we interperet here as plasma above the equilibrium formation
temperature. To understand these observations we compare them with a
hydrodynamic flare model.
Title: Division II: Commission 12: Solar Radiation and Structure
Authors: Kosovichev, Alexander; Cauzzi, Gianna; Martinez Pillet,
Valentin; Asplund, Martin; Brandenburg, Axel; Chou, Dean-Yi;
Christensen-Dalsgaard, Jorgen; Gan, Weiqun; Kuznetsov, Vladimir D.;
Rovira, Marta G.; Shchukina, Nataliya; Venkatakrishnan, P.
Bibcode: 2015IAUTB..28..109K
Altcode:
The President of C12, Alexander Kosovichev, presented the status of
the Commission and its working Group(s). Primary activities included
organization of international meetings (IAU Symposia, Special Sessions
and Joint Discussion); review and support of proposals for IAU sponsored
meetings; organization of working groups on the Commission topics
to promote the international cooperation; preparation of triennial
report on the organizational and science activities of Commission
members. Commission 12 broadly encompasses topics of solar research
which include studies of the Sun's internal structure, composition,
dynamics and magnetism (through helioseismology and other techniques),
studies of the quiet photosphere, chromosphere and corona, and also
research of the mechanisms of solar radiation, and its variability on
various time scales. Some overlap with topics covered by Commission
10 Solar Activity is unavoidable, and many activities are sponsored
jointly by these two commissions. The Commission website can be found
at http://sun.stanford.edu/IAU-Com12/, with information about related
IAU Symposiums and activities, and links to appropriate web sites.
Title: Future observations of solar activity
Authors: Cauzzi, Gianna
Bibcode: 2015IAUGA..2257363C
Altcode:
Several large solar telescopes and instrumental projects are well
underway and scheduled to completion in the next decade. Notable
examples are the US-led 4-m ground-based DKIST, optimized for high
resolution studies in the optical and infrared, that will see first
light in 2019; the ESA-NASA Solar Orbiter, scheduled for launch in 2018
on an innovative orbite which will provide close-up, high-latitude
observations of the Sun; the Japan-led Solar-C spacecraft, with a
large suite of complementary instruments aiming at understanding the
magnetised solar atmosphere from bottom to top, that is currently
being proposed jointly to JAXA, ESA and NASA.I will provide a short
review of such facilities from the point of view of solar activity
studies, highlighting the novel approach they will provide for solar
flare analysis, and discuss the possibilities offered by coordinated
operations of multiple telescopes.
Title: Temporal Evolution of Multiple Evaporating Ribbon Sources in
a Solar Flare
Authors: Graham, D. R.; Cauzzi, G.
Bibcode: 2015ApJ...807L..22G
Altcode: 2015arXiv150603465G
We present new results from the Interface Region Imaging Spectrograph
(IRIS) showing the dynamic evolution of chromospheric evaporation
and condensation in a flare ribbon, with the highest temporal
and spatial resolution to date. IRIS observed the entire impulsive
phase of the X-class flare SOL2014-09-10T17:45 using a 9.4 s cadence
“sit-and-stare” mode. As the ribbon brightened successively at
new positions along the slit, a unique impulsive phase evolution
was observed for many tens of individual pixels in both coronal and
chromospheric lines. Each activation of a new footpoint displays
the same initial coronal upflows of up to ∼300 km s-1
and chromospheric downflows up to 40 km s-1. Although the
coronal flows can be delayed by over 1 minute with respect to those in
the chromosphere, the temporal evolution of flows is strikingly similar
between all pixels and consistent with predictions from hydrodynamic
flare models. Given the large sample of independent footpoints, we
conclude that each flaring pixel can be considered a prototypical,
“elementary” flare kernel.
Title: Science with Large Solar Telescopes: Overview of SpS 6
Authors: Cauzzi, Gianna; Tritschler, Alexandra; Deng, Yuanyong
Bibcode: 2015HiA....16..439C
Altcode:
With several large aperture optical and IR telescopes just coming
on-line, or scheduled for the near future, solar physics is on the
verge of a quantum leap in observational capabilities. An efficient
use of such facilities will require new and innovative approaches to
both observatory operations and data handling. This two-days
long Special Session discussed the science expected with large
solar telescopes, and started addressing the strategies necessary
to optimize their scientific return. Cutting edge solar science as
derived from state-of-the-art observations and numerical simulations
and modeling was presented, and discussions were held on the role of
large facilities in satisfying the demanding requirements of spatial and
temporal resolution, stray-light correction, and spectro-polarimetric
accuracy. Building on the experience of recently commissioned
telescopes, critical issues for the development of future facilities
were discussed. These included operational issues peculiar to large
telecopes as well as strategies for their best use.
Title: Optical Spectral Observations of a Flickering White-light
Kernel in a C1 Solar Flare
Authors: Kowalski, Adam F.; Cauzzi, Gianna; Fletcher, Lyndsay
Bibcode: 2015ApJ...798..107K
Altcode: 2014arXiv1411.0770K
We analyze optical spectra of a two-ribbon, long-duration
C1.1 flare that occurred on 2011 August 18 within AR 11271
(SOL2011-08-18T15:15). The impulsive phase of the flare was observed
with a comprehensive set of space-borne and ground-based instruments,
which provide a range of unique diagnostics of the lower flaring
atmosphere. Here we report the detection of enhanced continuum emission,
observed in low-resolution spectra from 3600 Å to 4550 Å acquired
with the Horizontal Spectrograph at the Dunn Solar Telescope. A small,
<=0.''5 (1015 cm2) penumbral/umbral kernel
brightens repeatedly in the optical continuum and chromospheric
emission lines, similar to the temporal characteristics of the hard
X-ray variation as detected by the Gamma-ray Burst Monitor on the Fermi
spacecraft. Radiative-hydrodynamic flare models that employ a nonthermal
electron beam energy flux high enough to produce the optical contrast
in our flare spectra would predict a large Balmer jump in emission,
indicative of hydrogen recombination radiation from the upper flare
chromosphere. However, we find no evidence of such a Balmer jump in
the bluemost spectral region of the continuum excess. Just redward of
the expected Balmer jump, we find evidence of a "blue continuum bump"
in the excess emission which may be indicative of the merging of the
higher order Balmer lines. The large number of observational constraints
provides a springboard for modeling the blue/optical emission for this
particular flare with radiative-hydrodynamic codes, which are necessary
to understand the opacity effects for the continuum and emission line
radiation at these wavelengths.
Title: Continuum Emission from a Microflare Kernel Observed by IRIS
Authors: Daw, A. N.; Kowalski, A. F.; Wuelser, J. P.; Cauzzi, G.;
Allred, J. C.; Christe, S.
Bibcode: 2014AGUFMSH51C4166D
Altcode:
Fits to Interface Region Imaging Spectrograph (IRIS) spectra observed
from a bright kernel during the impulsive phase of a solar microflare
(GOES class B9) are presented, providing long-sought constraints on
the UV/white-light continuum emission during flares. Constraints on
beam energy and cross sectional area are provided by cotemporaneous
RHESSI and SDO/AIA 1700 A observations, respectively, allowing for
comparison of the observed IRIS continuum to calculations of non-thermal
electron beam heating using the RADYN radiative-hydrodynamic loop
model. Implications for flare energy release are discussed.
Title: Chromospheric umbral dynamics
Authors: Reardon, Kevin P.; Vecchio, Antonio; Cauzzi, Gianna;
Tritschler, Alexandra
Bibcode: 2014AAS...22432304R
Altcode:
The chromosphere above sunspots is seen to undergo dynamical driving
from perturbations from lower layers of the atmosphere. Umbral
flashes have long been understood to be the result of acoustic shocks
due to the drop in density in the sunspot chromosphere. Detailed
observations of the umbral waves and flashes may help reveal the
nature of the sunspot structure in the upper atmosphere. We report
on high-resolution observations of umbral dynamics observed in the Ca
II 8542 line by IBIS at the Dunn Solar Telescope. We use a principal
component decomposition technique (POD) to isolate different components
of the observed oscillations. We are able to explore temporal and
spatial evolution of the umbral flashes. We find significant variation
in the nature of the flashes over the sunspot, indicating that the
chromospheric magnetic topology can strongly modify the nature of the
umbral intensity and velocity oscillations.
Title: F-CHROMA.Flare Chromospheres: Observations, Models and Archives
Authors: Cauzzi, Gianna; Fletcher, Lyndsay; Mathioudakis, Mihalis;
Carlsson, Mats; Heinzel, Petr; Berlicki, Arek; Zuccarello, Francesca
Bibcode: 2014AAS...22412339C
Altcode:
F-CHROMA is a collaborative project newly funded under the EU-Framework
Programme 7 "FP7-SPACE-2013-1", involving seven different European
research Institutes and Universities. The goal of F-CHROMA is to
substantially advance our understanding of the physics of energy
dissipation and radiation in the flaring solar atmosphere, with a
particular focus on the flares' chromosphere. A major outcome of the
F-CHROMA project will be the creation of an archive of chromospheric
flare observations and models to be made available to the community
for further research.In this poster we describe the structure and
milestones of the project, the different activities planned, as well
as early results. Emphasis will be given to the dissemination efforts
of the project to make results of these activities available to and
usable by the community.
Title: Chromospheric Diagnostics from IRIS and DST
Authors: Cauzzi, Gianna; Reardon, Kevin P.; Jaeggli, Sarah A.;
Reid, Aaron
Bibcode: 2014AAS...22430201C
Altcode:
Using data obtained during a coordinated observing campaign in
September 2013, we compare the spectral and imaging diagnostics from
IRIS and the instruments at the Dunn Solar Telescope (DST). We focus
on a small active region observed for approximately one hour with IRIS
(NUV, FUV, and SJI) in conjunction with IBIS, FIRS, and ROSA from the
DST.In particular, we examine the line widths and intensities in the
different chromospheric lines (H-alpha, Ca II 8542, Mg II) and the
temporal evolution of these different diagnostics. This allows us to
better relate the views from new window provided by IRIS to previous
studies of the chromosphere.
Title: The Solar Chromosphere Observed at 1 Hz and 0.''2 Resolution
Authors: Lipartito, Isabel; Judge, Philip G.; Reardon, Kevin; Cauzzi,
Gianna
Bibcode: 2014ApJ...785..109L
Altcode: 2014arXiv1401.4474L
We recently reported extremely rapid changes in chromospheric fine
structure observed using the IBIS instrument in the red wing of
Hα. Here, we examine data obtained during the same observing run
(2010 August 7), of a mature active region NOAA 11094. We analyze
more IBIS data including wavelength scans and data from the Solar
Dynamics Observatory, all from within a 30 minute interval. Using a
slab radiative transfer model, we investigate the physical nature of
fibrils in terms of tube-like versus sheet-like structures. Principal
Component Analysis shows that the very rapid Hα variations in the
line wings depend mostly on changes of line width and line shift,
but for Ca II 854.2 the variations are dominated by changes in column
densities. The tube model must be rejected for a small but significant
class of fibrils undergoing very rapid changes. If our wing data arise
from the same structures leading to "type II spicules," our analysis
calls into question much recent work. Instead, the data do not reject
the hypothesis that some fibrils are optical superpositions of plasma
collected into sheets. We review how Parker's theory of tangential
discontinuities naturally leads to plasma collecting into sheets,
and show that the sheet picture is falsifiable. Chromospheric fine
structures seem to be populated by both tubes and sheets. We assess the
merits of spectral imaging versus slit spectroscopy for future studies.
Title: Comet C/2012 S1 (ISON): Observations of the Dust Grains from
SOFIA and of the Atomic Gas from NSO Dunn and McMath-Pierce Solar
Telescopes (Invited)
Authors: Wooden, D. H.; Woodward, C. E.; Harker, D. E.; Kelley, M. S.;
Sitko, M.; Reach, W. T.; De Pater, I.; Gehrz, R. D.; Kolokolova,
L.; Cochran, A. L.; McKay, A. J.; Reardon, K.; Cauzzi, G.; Tozzi,
G.; Christian, D. J.; Jess, D. B.; Mathioudakis, M.; Lisse, C. M.;
Morgenthaler, J. P.; Knight, M. M.
Bibcode: 2013AGUFM.P24A..07W
Altcode:
Comet C/2012 S1 (ISON) is unique in that it is a dynamically new comet
derived from the Oort cloud reservoir of comets with a sun-grazing
orbit. Infrared (IR) and visible wavelength observing campaigns were
planned on NASA's Stratospheric Observatory For Infrared Astronomy
(SOFIA) and on National Solar Observatory Dunn (DST) and McMath-Pierce
Solar Telescopes, respectively. We highlight our early results. SOFIA
(+FORCAST [1]) mid- to far-IR images and spectroscopy (~5-35 μm)
of the dust in the coma of ISON are to be obtained by the ISON-SOFIA
Team during a flight window 2013 Oct 21-23 UT (r_h≈1.18 AU). Dust
characteristics, identified through the 10 μm silicate emission
feature and its strength [2], as well as spectral features from
cometary crystalline silicates (Forsterite) at 11.05-11.2 μm, and
near 16, 19, 23.5, 27.5, and 33 μm are compared with other Oort cloud
comets that span the range of small and/or highly porous grains (e.g.,
C/1995 O1 (Hale-Bopp) [3,4,5] and C/2001 Q4 (NEAT) [6]) to large and/or
compact grains (e.g., C/2007 N4 (Lulin) [7] and C/2006 P1 (McNaught)
[8]). Measurement of the crystalline peaks in contrast to the broad
10 and 20 μm amorphous silicate features yields the cometary silicate
crystalline mass fraction [9], which is a benchmark for radial transport
in our protoplanetary disk [10]. The central wavelength positions,
relative intensities, and feature asymmetries for the crystalline
peaks may constrain the shapes of the crystals [11]. Only SOFIA can
look for cometary organics in the 5-8 μm region. Spatially resolved
measurements of atoms and simple molecules from when comet ISON is
near the Sun (r_h< 0.4 AU, near Nov-20--Dec-03 UT) were proposed
for by the ISON-DST Team. Comet ISON is the first comet since comet
Ikeya-Seki (1965f) [12,13] suitable for studying the alkalai metals Na
and K and the atoms specifically attributed to dust grains including
Mg, Si, Fe, as well as Ca. DST's Horizontal Grating Spectrometer
(HGS) measures 4 settings: Na I, K, C2 to sample cometary organics
(along with Mg I), and [O I] as a proxy for activity from water [14]
(along with Si I and Fe I). State-of-the-art instruments that will also
be employed include IBIS [15], which is a Fabry-Perot spectral imaging
system that concurrently measures lines of Na, K, Ca II, or Fe, and ROSA
(CSUN/QUB) [16], which is a rapid imager that simultaneously monitors Ca
II or CN. From McMath-Pierce, the Solar-Stellar Spectrograph also will
target ISON (320-900 nm, R~21,000, r_h<0.3 AU). Assuming survival,
the intent is to target ISON over r_h<0.4 AU, characteristic of
prior Na detections [12,13,17,18,19]. References: [1] Adams, J.D., et
al. 2012, SPIE, 8446, 16; [2] Kelley, M.S., Wooden, D.H. 2009, PSS, 57,
1133; [3] Harker et al. 2002, ApJ, 580, 579; [4] Hayward et al. 2000,
ApJ, 538, 428; [5] Hadamcik, E., Levasseur-Regourd, A.C. 2003, JQSRT,
79-80, 661; [6] Wooden, D.H. 2004, ApJL, 612, L77; [7] Woodward et
al. 2011, AJ, 141, 181; [8] Kelley et al. 2010, LPSC, 41, #2375;
[9] Kelley, M.S. et al. 2011, AAS, 211, 560; [10] Wooden, D.H. 2008,
SSRv, 138, 75; [11] Lindsay et al. 2013, ApJ, 766, 54; [12] Preston,
G. W. 1967, ApJ, 147, 718; [13] Slaughter, C.D. 1969, AJ, 74, 929;
[14] McKay et al. 2012, Icarus, 222, 684; [15] Cavallini, F., 2006,
Solar Phys., 236, 415; [16] Jess et al., 2010, Solar Phys, 261, 363;
[17] Watanabe, J-I. et al. 2003, ApJ, 585, L159; [18] Leblanc, F. et
al. 2008, A&A, 482, 293; [19] Fulle, M. et al. 2013, ApJL, 771, L21
Title: Spatially Resolved Spectroscopic Observations of Na and K in
the Tail of Comet C/2011 L4 (PanSTARRS)
Authors: Cochran, Anita L.; Wooden, D. H.; McKay, A. J.; Cauzzi, G.;
Reardon, K.; Tozzi, G.
Bibcode: 2013DPS....4550205C
Altcode:
We used the Dunn Solar Telescope (DST) of The National Solar Observatory
to obtain spectroscopic observations of comet C/2011 L4 (PanSTARRS) on
13 and 14 March 2013. The DST has the advantage for comet observations
that one can observe the comet when it is close to the Sun. At the
time of our observations, comet PanSTARRS was at 0.31 and 0.32 AU
heliocentric distance. We used the Horizontal Spectrograph to observe
five different spectral regions of the coma. The resolving power was
50,000 - 60,000. The slit was 0.3 arcsec wide and 171 arcsec long. At
the comet's geocentric distance, the slit covered 1.43e5 km. The
comet was approximately centered on the slit. We observed strong
emissions from sodium (D1@589.592nm and D2@588.995nm) and potassium
(D1@770.108nm and D2@671.701nm), along with a weak continuum. Lithium
was not detected. The sodium was visible on the optocenter and the
tailward side of the comet and extended to the edge of the slit (i.e. at
least 70,000km tailward). It shifted redward at larger cometocentric
distances, attributable to the acceleration of sodium by solar radiation
pressure. The potassium was much weaker than the sodium and does not
appear to extend as far from the optocenter. In this paper, we will show
the distribution of these gases and compare their relative strengths. We
will discuss the effects of the different photodissociative lifetimes
of sodium and potassium and how they dictate what we observed.
Title: The properties of flare kernels observed by the Dunn Solar
Telescope
Authors: Fletcher, Lyndsay; Kowalski, A.; Cauzzi, G.; Hawley, S. L.;
Hudson, H. S.
Bibcode: 2013SPD....44...67F
Altcode:
We report on a campaign at the Dunn Solar Telescope which resulted in
successful imaging and spectroscopic observations of a C1.1 solar flare
on 18th August 2011. This flare exhibited ribbons with complicated
fine structure at the resolution of the DST/IBIS instrument, and a
number of bright kernels with sizes comparable to the smallest scales
sampled by IBIS, around 2-4 pixels (0."3-0."6) FWHM. We focus on these
bright kernels, describing their spatial characteristics in the core
and wing of H alpha and Ca II 8542, and in the UV and EUV with SDO. We
also show preliminary broad-band spectroscopy of the kernels which may
demonstrate the presence of an optical continuum in this small flare.
Title: First Results from the EUNIS 2013 Sounding Rocket Campaign
Authors: Daw, Adrian N.; Rabin, D. M.; Brosius, J. W.; Haas, J. P.;
Plummer, T.; Cauzzi, G.; Reardon, K. P.; Beck, C.
Bibcode: 2013SPD....4410501D
Altcode:
The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS)
sounding rocket launched 23 April 2013 at 17:30 UT, as part of a
campaign including co-ordinated observations with the Dunn Solar
Telescope/IBIS, Hinode/EIS, SoHO/CDS, RHESSI and SDO. EUNIS obtained
the highest-resolution observations of the solar spectrum from 52-63 nm
observed to date, as well as observations with the previously-flown
waveband from 30-37 nm. The broad spectral coverage of the EUV
observations includes emission lines of ionization stages from He I to
Fe XIX, and thus a wide temperature range of 0.025 to 10 MK. Absolute
radiometric calibration of EUNIS provides underflight calibration of
CDS, EIS and AIA. Spectra were obtained with a 1.3 s cadence as the
660-arcsec long slit was rastered across two different regions. The
observations captured a B-class flare in active region NOAA 11726 as
well as active regions 11723, 11724, off-limb, quiet sun and a coronal
hole. We discuss first results from anaysis of this rich and extensive
data set.
Title: Science with Large Solar Telescopes
Authors: Cauzzi, G.; Tritschler, A.; Deng, Y.
Bibcode: 2012IAUSS...6E....C
Altcode:
With several large aperture optical/IR telescopes coming on-line,
and scheduled for the near future, solar physics is on the verge
of a quantum leap in observational capabilities. An efficient use
of such facilities will require new and innovative approaches to
both observatory operations and data handling. This two-days
long Special Session will discuss the science expected with large
solar telescopes, and start addressing the strategies necessary to
optimize their scientific return. Cutting edge solar science as derived
from state of the art observations and numerical simulations will be
presented, and discussions will be held on the role of large facilities
in satisfying the demanding requirements of spatial and temporal
resolution, stray-light, and spectro-polarimetric accuracy. Building on
the experience of recently commissioned telescopes, we will then discuss
critical issues for the development of future facilities including
operational issues peculiar to large telecopes, and strategies for
their best use.
Title: The IBIS Mosaic
Authors: Cauzzi, G.; Reardon, K.
Bibcode: 2012IAUSS...6E.511C
Altcode:
Existing and planned instrumentation for large solar telescopes is
tailored to exploit the high spatial resolution affordable with such
facilities. However, the typical instrumental tradeoffs restrict the
field-of-view accessible at once to rather small areas (well below
100" diameter): this represents a serious impediment for study of
the active Sun, where large scale magnetic connectivity is of much
relevance. Mosaicking offers a possibility to obtain high-resolution
observations over a large FOV, but the technique has been only
sparsely utilized at ground-based, optical telescopes. In this poster
we report on an investigation of the feasibility and utility of mosaic
observations with a state-of-the-art facility, the Interferometric
BIdimensional Spectrometer instrument (IBIS) installed at the Dunn
Solar Telescope (NSO). We obtained a 3 x 3 mosaic, covering the full
AR NOAA 11092 for a total field in excess of 4' x 4', sampling both
photospheric and chromospheric lines. We report on the methods utilized
for observation and assembly of the data cubes, and some preliminary
comparisons with simultaneous observations from other instruments.
Title: LEMUR: Large European module for solar Ultraviolet
Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
Thomas; Winter, Berend; Young, Peter
Bibcode: 2012ExA....34..273T
Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
The solar outer atmosphere is an extremely dynamic environment
characterized by the continuous interplay between the plasma and the
magnetic field that generates and permeates it. Such interactions play a
fundamental role in hugely diverse astrophysical systems, but occur at
scales that cannot be studied outside the solar system. Understanding
this complex system requires concerted, simultaneous solar observations
from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
high spatial resolution (between 0.1'' and 0.3''), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
from the chromosphere to the flaring corona), and the capability of
measuring magnetic fields through spectropolarimetry at visible and
near-infrared wavelengths. Simultaneous spectroscopic measurements
sampling the entire temperature range are particularly important. These
requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload
providing a significant improvement of imaging and spectropolarimetric
capabilities in the UV, visible, and near-infrared with respect to
what is available today and foreseen in the near future. The Large
European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload
of high-resolution imaging spectrographs and cameras. LEMUR consists
of two major components: a VUV solar telescope with a 30 cm diameter
mirror and a focal length of 3.6 m, and a focal-plane package composed
of VUV spectrometers covering six carefully chosen wavelength ranges
between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with
0.14'' per pixel sampling. In addition, LEMUR is capable of measuring
mass flows velocities (line shifts) down to 2 km s - 1 or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.
Title: Conceptual design of the data handling system for the European
Solar Telescope
Authors: Ermolli, Ilaria; Cauzzi, Gianna; Collados, Manuel; Paletou,
Frederic; Reardon, Kevin; Aboudarham, Jean; Cirami, Roberto; Cosentino,
Rosario; Del Moro, Dario; Di Marcantonio, Paolo; Giorgi, Fabrizio;
Lafon, Martine; Pietropaolo, Ermanno; Romano, Paolo
Bibcode: 2012SPIE.8448E..1SE
Altcode:
We present an overview of the conceptual design of the data handling
unit of the ECS, the Control System for the European Solar Telescope
(EST). We will focus on describing the critical requirements for this
unit resulting from the overall design of the telescope, together with
its architecture and the results of the feasibility analysis carried
out to date.
Title: Evidence for Sheet-like Elementary Structures in the Sun's
Atmosphere?
Authors: Judge, Philip G.; Reardon, Kevin; Cauzzi, Gianna
Bibcode: 2012ApJ...755L..11J
Altcode:
Narrow, thread-like structures in the Sun's chromosphere are currently
understood to be plasma guided along narrow tubes of magnetic flux. We
report on 1 s cadence imaging spectroscopic measurements of the Hα
line with the IBIS Fabry-Pérot instrument at the Dunn Solar Telescope,
obtained +0.11 nm from line center. Rapid changes grossly exceeding
the Alfvén speed are commonly seen along the full extent of many
chromospheric threads. We argue that only an optical superposition
effect can reasonably explain the data, analogous to striations of
curtains blowing in the wind. Other explanations appear to require
significant contrivances to avoid contradicting various aspects of
the data. We infer that the absorbing plasma exists in two-dimensional
sheet-like structures within the three-dimensional magnetofluid, related
perhaps to magnetic tangential discontinuities. This interpretation
demands a re-evaluation of basic assumptions about low-β solar plasmas,
as advocated by Parker, with broader implications in astrophysics
and plasma physics. Diverse, high-cadence observations are needed to
further define the relationship between magnetic field and thermal
fine structure.
Title: The IBIS Mosaic - A Broad View Of The Solar Atmosphere
Authors: Reardon, Kevin P.; Cauzzi, G.
Bibcode: 2012AAS...22020111R
Altcode:
We present a unique set of observations spanning the photosphere and
chromosphere with a large field-of-view (4 x 4 arcminutes) ,high-spatial
resolution (0.1"/pixel), and full spectral profiles (R ∼ 200,000). The
data were obtained with the IBIS imaging spectrometer at the NSO/Dunn
Solar Telescope on August 3, 2010 using a mosaic technique to tile an
active region and surrounding areas. Spectral profiles were obtained
in the chromospheric Hα, CaII 854.2 nm, and He I D3 lines, as well as
photospheric FeI 543.4 nm. Combining this dataset with simultaneous
SDO/AIA and SDO/HMI images and magnetic field measurements allow a
highly comprehensive view of an entire volume of the solar atmosphere
from photosphere to corona. The wealth of information is used to
explore the nature of the chromospheric fibrillar structures and their
relationship with the overlying corona.
Title: Commission 12: Solar Radiation and Structure
Authors: Kosovichev, Alexander; Cauzzi, Gianna; Pillet, Valentin
Martinez; Asplund, Martin; Brandenburg, Axel; Chou, Dean-Yi;
Christensen-Dalsgaard, Jorgen; Gan, Weiqun; Kuznetsov, Vladimir D.;
Rovira, Marta G.; Shchukina, Nataliya; Venkatakrishnan, P.
Bibcode: 2012IAUTA..28...81K
Altcode: 2012IAUTB..28...81K
Commission 12 of the International Astronomical Union encompasses
investigations of the internal structure and dynamics of the Sun, mostly
accessible through the techniques of local and global helioseismology,
the quiet solar atmosphere, solar radiation and its variability, and
the nature of relatively stable magnetic structures like sunspots,
faculae and the magnetic network. The Commission sees participation
of over 350 scientists worldwide.
Title: Division II: Sun and Heliosphere
Authors: Martínez Pillet, Valentín; Klimchuk, James A.; Melrose,
Donald B.; Cauzzi, Gianna; van Driel-Gesztelyi, Lidia; Gopalswamy,
Natchimuthuk; Kosovichev, Alexander; Mann, Ingrid; Schrijver,
Carolus J.
Bibcode: 2012IAUTA..28...61M
Altcode: 2012IAUTA..28...61P
The solar activity cycle entered a prolonged quiet phase that started
in 2008 and ended in 2010. This minimum lasted for a year longer
than expected and all activity proxies, as measured from Earth and
from Space, reached minimum values never observed before (de Toma,
2012). The number of spotless days from 2006 to 2009 totals 800, the
largest ever recorded in modern times. Solar irradiance was at historic
minimums. The interplanetary magnetic field was measured at values as
low as 2.9 nT and the cosmic rays were observed at records-high. While
rumors spread that the Sun could be entering a grand minimum quiet
phase (such as the Maunder minimum of the XVII century), activity
took over in 2010 and we are now well into Solar Cycle 24 (albeit,
probably, a low intensity cycle), approaching towards a maximum due
by mid 2013. In addition to bringing us the possibility to observe
a quiet state of the Sun and of the Heliosphere that was previously
not recorded with modern instruments, the Sun has also shown us how
little we know about the dynamo mechanism that drives its activity as
all solar cycle predictions failed to see this extended minimum coming.
Title: New insight on the coupling of the solar atmosphere from
imaging spectroscopy
Authors: Reardon, K.; Cauzzi, G.
Bibcode: 2012decs.confE..20R
Altcode:
We present spectrally resolved, high-resolution observations of
chromospheric diagnostics obtained with IBIS covering a full active
region. In particular, the data includes the first high-resolution
observations of the He I D3 line (587.6 nm), a subordinate of the more
famous HeI 1083.0 nm line, showing loops and other structures on the
solar disk at the 150 km diffraction limit. The large FOV of our data
allows a meaningfully comparison with the SDO full disk observations
to investigate the coupling between different portions of the solar
atmosphere and the topology of the chromospheric magnetic field. The
relationship between the chromospheric signatures and the SDO 304 Å and
171 Å emission provides intriguing hints to the existence of low-lying
loops at TR temperatures effectively disconnected from the corona.
Title: Data handling and control of the European Solar Telescope
Authors: Ermolli, I.; Bettonvil, F.; Cauzzi, G.; Cavaller, L.;
Collados, M.; Di Marcantonio, P.; Grivel, C.; Paletou, F.; Romano,
P.; Aboudarham, J.; Cirami, R.; Cosentino, R.; Giorgi, F.; Lafon,
M.; Laforgue, D.; Reardon, K.; Sliepen, G.
Bibcode: 2012MSAIS..19..380E
Altcode:
We describe some aspects of the facility operation that have been
considered for the design of the data handling and control of the
European Solar Telescope. The main sub-systems of the EST relevant for
the control are summarized, together with some information on current
solar data models.
Title: Splinter Session "Solar and Stellar Flares"
Authors: Fletcher, L.; Hudson, H.; Cauzzi, G.; Getman, K. V.; Giampapa,
M.; Hawley, S. L.; Heinzel, P.; Johnstone, C.; Kowalski, A. F.; Osten,
R. A.; Pye, J.
Bibcode: 2011ASPC..448..441F
Altcode: 2011csss...16..441F; 2012arXiv1206.3997F
This summary reports on papers presented at the Cool Stars-16 meeting in
the splinter session "Solar and Stellar flares." Although many topics
were discussed, the main themes were the commonality of interests,
and of physics, between the solar and stellar flare communities,
and the opportunities for important new observations in the near future.
Title: Data handling and control for the European Solar Telescope
Authors: Ermolli, Ilaria; Bettonvil, Felix; Cauzzi, Gianna; Cavaller,
Lluis; Collados, Manuel; Di Marcantonio, Paolo; Paletou, Frederic;
Romano, Paolo; Aboudarham, Jean; Cirami, Roberto; Cosentino, Rosario;
Giorgi, Fabrizio; Lafon, Martine; Laforgue, Didier; Reardon, Kevin;
Sliepen, Guus
Bibcode: 2010SPIE.7740E..0GE
Altcode: 2010SPIE.7740E..13E
We introduce the concepts for the control and data handling systems of
the European Solar Telescope (EST), the main functional and technical
requirements for the definition of these systems, and the outcomes
from the trade-off analysis to date. Concerning the telescope control,
EST will have performance requirements similar to those of current
medium-sized night-time telescopes. On the other hand, the science
goals of EST require the simultaneous operation of three instruments
and of a large number of detectors. This leads to a projected data
flux that will be technologically challenging and exceeds that of
most other astronomical projects. We give an overview of the reference
design of the control and data handling systems for the EST to date,
focusing on the more critical and innovative aspects resulting from
the overall design of the telescope.
Title: The ADAHELI solar mission: Investigating the structure of
Sun's lower atmosphere
Authors: Berrilli, F.; Bigazzi, A.; Roselli, L.; Sabatini, P.; Velli,
M.; Alimenti, F.; Cavallini, F.; Greco, V.; Moretti, P. F.; Orsini,
S.; Romoli, M.; White, S. M.; ADAHELI Team; Ascani, L.; Carbone, V.;
Curti, F.; Consolini, G.; Di Mauro, M. P.; Del Moro, D.; Egidi, A.;
Ermolli, I.; Giordano, S.; Pastena, M.; Pulcino, V.; Pietropaolo, E.;
Romano, P.; Ventura, P.; Cauzzi, G.; Valdettaro, L.; Zuccarello, F.;
ADAHELI Team
Bibcode: 2010AdSpR..45.1191B
Altcode: 2010AdSpR..45.1191A
ADAHELI (ADvanced Astronomy for HELIophysics) is a small-class
(500 kg) low-budget (50 MEuro) satellite mission for the study of
the solar photosphere and the chromosphere and for monitoring solar
flare emission. ADAHELI's design has completed its Phase-A feasibility
study in December 2008, in the framework of ASI's (Agenzia Spaziale
Italiana) 2007 "Small Missions" Program (calling for two missions at
50 MEeuros each, plus the launch budget). ADAHELI's main purpose is
to explore Sun's lower atmosphere in the near-infrared, a region so
far unexplored by solar observations from space. ADAHELI will carry
out observations of the solar photosphere and of the chromosphere at
high-temporal rate and high spatial and spectral resolutions. ADAHELI
will contribute to the understanding of Space Weather through the
study of particle acceleration during flares. A radiometer operating
in the millimeter radio band will continuously monitor the solar disk,
throughout the spacecraft's life time. ADAHELI's baseline instruments
are a 50-cm high-resolution telescope operating in the visible and
the near-infrared, and a lightweight full-disk radiometer operating at
millimeter wavelengths (90 GHz). The core of the telescope's focal plane
suite is the spectral imager based on two Fabry-Perot interferometers,
flying for the first time on a solar mission. The instrument
will return fast-cadence, full bi-dimensional spectral images at
high-resolution, thus improving on current slit-scan, mono-dimensional
architectures. Moreover, the possibility of working in polarized light
will enable full 3D magnetic field reconstruction on the photosphere
and the chromosphere. An optional instrumental package is also being
proposed to further extend ADAHELI's scope: a full-disk telescope for
helioseismology based on a double Magneto-Optical Filter, a Neutral
Particle Analyzer for magnetospheric research, an Extreme Ultraviolet
imaging and spectro-radiometry instrument. These options fall outside
the prescribed budget. ADAHELI, flying a Sun-Synchronous orbit at 800
km, will perform continuous, long-duration (4-h), daily acquisitions,
with the possibility of extending them up to 24 h. ADAHELI's operating
life is two years, plus one extension year. Launch would be nominally
planned for 2014.
Title: Delving into the Chromosphere: New Observational Tools
Authors: Reardon, Kevin P.; Cauzzi, G.; Tritschler, A.; Uitenbroek, H.
Bibcode: 2010AAS...21630503R
Altcode:
The chromosphere lies at the boundary between the near-equilibrium
photosphere and the hot, expanding corona. This region combines both
large interconnecting magnetic structures, and fine-scaled dynamics into
an intriguingly complex whole. Studying this behavior is a significant
observational challenge, requiring sizable fields of view (60-90")
sampled at high spatial (< 0.3") and temporal resolution (< 30
seconds), with full spectral information in multiple lines. We will
describe how instruments based on Fabry-Perot interferometers have
recently begun to routinely deliver such observations. We will review
some of the most exciting results obtained and the deeper insights
they have provided into the characteristics of the solar chromosphere.
Title: Fabry-Pérot Versus Slit Spectropolarimetry of Pores and
Active Network: Analysis of IBIS and Hinode Data
Authors: Judge, Philip G.; Tritschler, Alexandra; Uitenbroek, Han;
Reardon, Kevin; Cauzzi, Gianna; de Wijn, Alfred
Bibcode: 2010ApJ...710.1486J
Altcode: 2010arXiv1001.0561J
We discuss spectropolarimetric measurements of photospheric (Fe I
630.25 nm) and chromospheric (Ca II 854.21 nm) spectral lines in and
around small magnetic flux concentrations, including a pore. Our
long-term goal is to diagnose properties of the magnetic field
near the base of the corona. We compare ground-based two-dimensional
spectropolarimetric measurements with (almost) simultaneous space-based
slit spectropolarimetry. We address the question of noise and crosstalk
in the measurements and attempt to determine the suitability of Ca II
measurements with imaging spectropolarimeters for the determination
of chromospheric magnetic fields. The ground-based observations
were obtained 2008 May 20, with the Interferometric Bidimensional
Spectrometer (IBIS) in spectropolarimetric mode operated at the Dunn
Solar Telescope at Sunspot, NM. The space observations were obtained
with the Spectro-Polarimeter of the Solar Optical Telescope aboard the
Japanese Hinode satellite. The agreement between the near-simultaneous
co-spatial IBIS and Hinode Stokes-V profiles at 630.25 nm is
excellent, with V/I amplitudes compatible to within 1%. The IBIS QU
measurements are affected by residual crosstalk from V, arising from
calibration inaccuracies, not from any inherent limitation of imaging
spectroscopy. We use a Principal Component Analysis to quantify the
detected crosstalk. QU profiles with V crosstalk subtracted are in
good agreement with the Hinode measurements, but are noisier owing to
fewer collected photons. Chromospheric magnetic fields are notoriously
difficult to constrain by polarization of Ca II lines alone. However,
we demonstrate that high cadence, high angular resolution monochromatic
images of fibrils in Ca II and Hα, seen clearly in IBIS observations,
can be used to improve the magnetic field constraints, under conditions
of high electrical conductivity. Such work is possible only with time
series data sets from two-dimensional spectroscopic instruments such
as IBIS, under conditions of good seeing.
Title: Dual-Line Spectral Imaging of the Chromosphere
Authors: Cauzzi, G.; Reardon, K.; Rutten, R. J.; Tritschler, A.;
Uitenbroek, H.
Bibcode: 2010ASSP...19..513C
Altcode: 2010mcia.conf..513C
Hα filtergrams are notoriously difficult to interpret, "beautiful
to view but not fit for analysis." We try to remedy this by using
the IBIS bi-dimensional spectrometer at the Dunn Solar Telescope at
NSO/Sacramento Peak to compare the quiet-sun chromosphere observed in
Hα to what is observed simultaneously in Ca II 854.2 nm, sampling both
lines with high angular and spectral resolution and extended coverage
of space, time, and wavelength. Per (x, y, t) pixel we measured the
intensity and Dopplershift of the minimum of each line's profile at
that pixel, as well as the width of their inner chromospheric cores. A
paper submitted to A&A (December 2008) compares these measurements
in detail.
Title: Service-Mode Observations for Ground-Based Solar Physics
Authors: Reardon, K. P.; Rimmele, T.; Tritschler, A.; Cauzzi, G.;
Wöger, F.; Uitenbroek, H.; Tsuneta, S.; Berger, T.
Bibcode: 2009ASPC..415..332R
Altcode: 2009arXiv0909.1522R
There are significant advantages in combining Hinode observations
with ground-based instruments that can observe additional spectral
diagnostics at higher data rates and with greater flexibility. However,
ground-based observations, because of the random effects of weather
and seeing as well as the complexities data analysis due to changing
instrumental configurations, have traditionally been less efficient
than satellite observations in producing useful datasets. Future large
ground-based telescopes will need to find new ways to optimize both
their operational efficiency and scientific output. We have begun
experimenting with service-mode or queue-mode observations at the Dunn
Solar Telescope using the Interferometric Bidimensional Spectrometer
(IBIS) as part of joint Hinode campaigns. We describe our experiences
and the advantag es of such an observing mode for solar physics.
Title: The solar chromosphere at high resolution with
IBIS. IV. Dual-line evidence of heating in chromospheric network
Authors: Cauzzi, G.; Reardon, K.; Rutten, R. J.; Tritschler, A.;
Uitenbroek, H.
Bibcode: 2009A&A...503..577C
Altcode: 2009arXiv0906.2083C
The structure and energy balance of the solar chromosphere remain
poorly known. We used the imaging spectrometer IBIS at the Dunn Solar
Telescope to obtain fast-cadence, multi-wavelength profile sampling
of Hα and Ca ii 854.2 nm over a sizable two-dimensional field of view
encompassing quiet-Sun network. We provide a first inventory of how the
quiet chromosphere appears in these two lines by comparing basic profile
measurements in the form of image displays, temporal-average displays,
time slices, and pixel-by-pixel correlations. We find that the two lines
can be markedly dissimilar in their rendering of the chromosphere,
but that, nevertheless, both show evidence of chromospheric heating,
particularly in and around network: Hα in its core width and Ca ii
854.2 nm in its brightness. We discuss venues for improved modeling.
Title: The solar chromosphere at high resolution with
IBIS. III. Comparison of Ca II K and Ca II 854.2 nm imaging
Authors: Reardon, K. P.; Uitenbroek, H.; Cauzzi, G.
Bibcode: 2009A&A...500.1239R
Altcode: 2008arXiv0810.5260R
Aims: Filtergrams obtained in Ca II H, Ca II K, and Hα are often
employed as diagnostics of the solar chromosphere. The vastly disparate
appearance between the typical filtergrams in these different lines
calls into question the nature of what is actually being observed. We
investigate the lack of obvious structures of magnetic origin such as
fibrils and mottles in on-disk Ca II H and K images.
Methods: We
directly compare a temporal sequence of classical Ca II K filtergrams
with a co-spatial and co-temporal sequence of spectrally resolved
Ca II 854.2 images obtained with the Interferometric Bidimensional
Spectrometer (IBIS), considering the effect of both the spectral and
spatial smearing. We analyze the temporal behavior of the two series
by means of Fourier analysis.
Results: The lack of fine magnetic
structuring in Ca II K filtergrams, even with the narrowest available
filters, is due to observational effects, primarily contributions from
the bright, photospheric wings of the line that swamp the small and
dark chromospheric structures. Signatures of fibrils remain, however,
in the temporal evolution of the filtergrams, in particular with
the evidence of magnetic shadows around the network elements. The
Ca II K filtergrams do not appear, however, to properly reflect the
high-frequency behavior of the chromosphere. Using the same analysis,
we find no significant chromospheric signature in the Hinode/SOT Ca II
H quiet-Sun filtergrams.
Conclusions: The picture provided by Hα
and Ca II 854.2, which show significant portions of the chromosphere
dominated by magnetic structuring, appears to reflect the true and
essential nature of the solar chromosphere. Data that do not resolve
this aspect, whether spatially or spectrally, may misrepresent the
behavior the chromosphere.
Title: The solar chromosphere at high resolution with
IBIS. II. Acoustic shocks in the quiet internetwork and the role of
magnetic fields
Authors: Vecchio, A.; Cauzzi, G.; Reardon, K. P.
Bibcode: 2009A&A...494..269V
Altcode: 2008arXiv0807.4966V
Context: The exact nature of the quiet solar chromosphere and
especially its temporal variation, are still subjects of intense
debate. One of the contentious issues is the possible role of the
magnetic field in structuring the quieter solar regions.
Aims:
We characterize the dynamics of the quiet inter-network chromosphere
by studying the occurrence of acoustic shocks and their relation with
the concomitant photospheric structure and dynamics, including small
scale magnetic structures.
Methods: We analyze a comprehensive
data set that includes high-resolution chromospheric (Ca ii 854.2
nm) and photospheric (Fe i 709.0 nm) spectra obtained with the IBIS
imaging spectrometer in two quiet-Sun regions. This is complemented by
high-resolution sequences of MDI magnetograms of the same targets. From
the chromospheric spectra we identify the spatio-temporal occurrence of
the acoustic shocks. We compare it with the photospheric dynamics by
means of both Fourier and wavelet analysis and study the influence of
magnetic structures on the phenomenon.
Results: Mid-chromospheric
shocks occur within the general chromospheric dynamics pattern of
acoustic waves propagating from the photosphere. In particular, they
appear as a response to underlying powerful photospheric motions
at periodicities nearing the acoustic cut-off, consistent with 1-D
hydrodynamical modeling. However, their spatial distribution within
the supergranular cells is highly dependent on the local magnetic
topology, both at the network and internetwork scale. We find that
large portions of the internetwork regions undergo very few shocks,
since they are “shadowed” by the horizontal component of the
magnetic field. The latter is betrayed by the presence of chromospheric
fibrils, observed in the core of the Ca ii line as slanted structures
with distinct dynamical properties. The shadow mechanism also appears
to operate on the very small scales of inter-network magnetic elements,
and provides for a very pervasive influence of the magnetic field even
in the quietest region analyzed.
Conclusions: The magnetic field
might play a larger role in structuring the quiet solar chromosphere
than normally assumed. The presence of fibrils highlights a clear
disconnection between the photospheric dynamics and the response of
the geometrically overlaying chromosphere. As these results hold for
a mid-chromospheric indicator such as the Ca ii 854.2 line, it is
expected that diagnostics formed in higher layers, such as UV lines
and continua, will be affected to a greater extent by the presence
of magnetic fields, even in quiet regions. This is relevant for the
chromospheric models that make use of such diagnostics.
Title: The Solar Chromosphere: Old Challenges, New Frontiers
Authors: Ayres, T.; Uitenbroek, H.; Cauzzi, G.; Reardon, K.; Berger,
T.; Schrijver, C.; de Pontieu, B.; Judge, P.; McIntosh, S.; White,
S.; Solanki, S.
Bibcode: 2009astro2010S...9A
Altcode:
No abstract at ADS
Title: Commission 12: Solar Radiation and Structure
Authors: Martínez Pillet, Valentin; Kosovichev, Alexander;
Mariska, John T.; Bogdan, Thomas J.; Asplund, Martin; Cauzzi, Gianna;
Christensen-Dalsgaard, Jørgen; Cram, Lawrence E.; Gan, Weiqun; Gizon,
Laurent; Heinzl, Petr; Rovira, Marta G.; Venkatakrishnan, P.
Bibcode: 2009IAUTA..27..104M
Altcode:
Commission 12 encompasses investigations on the internal structure
and dynamics of the Sun, mostly accessible through the techniques of
local and global helioseismology, the quiet solar atmosphere, solar
radiation and its variability, and the nature of relatively stable
magnetic structures like sunspots, faculae and the magnetic network. A
revision of the progress made in these fields is presented. For some
specific topics, the review has counted with the help of experts
outside the Commission Organizing Committee that are leading and/or
have recently presented relevant works in the respective fields. In
this cases the contributor's name is given in parenthesis.
Title: The ADAHELI Solar Mission
Authors: Berrilli, F.; Velli, M.; Roselli, L.; Bigazzi, A.; Moretti,
P. F.; Romoli, M.; Orsini, S.; Cavallini, F.; Greco, V.; Carbone,
V.; Consolini, G.; Di Mauro, M. P.; Ermolli, I.; Pietropaolo, E.;
Romano, P.; Ventura, P.; White, S. M.; Zuccarello, F.; Cauzzi, G.;
Valdettaro, L.
Bibcode: 2008ESPM...12..6.6B
Altcode:
ADAHELI (Advanced Astronomy for HELIOphysics) is an Italian Space
project for the investigation of solar photospheric and chromospheric
dynamics, via high-resolution spectro-polarimetric observations in the
near-infrared spectral range. The mission has been financed for phase
A study in the framework of ASI Italian Space Agency Small Missions
Program call of September 2007. Four fields have been selected
to highlight the specific benefits of ADAHELI scientific payload: 1)
Photospheric and chromospheric dynamics and structure, 2) Emergence and
evolution of solar active regions and solar irradiance, 3) Chromospheric
and corona heating and turbulence, 4) Solar flares in the millimeter
wavelength region. The principal science instrument, ISODY, is
a 50 cm solar telescope equipped with an innovative Focal Plane Suite
composed of a spectro-polarimetric imager, based upon two Fabry-Perot
interferometers operating in the NIR regions around 845nm and 1083nm, a
broad band imager, and a correlation tracker used as image stabilization
system. Designed Mission Profiles for ADAHELI intend to achieve
continuous high-spectral and spatial resolution observations of the
Sun for a routine duration of 4 hours with a goal to be extended to
24 hours. ADAHELI also carries MIOS, a millimeter wavelengths
radiometer operating at around 90 GHz for flare detection. The
ADAHELI payload's instrument suite integrates and complements, without
overlap, the present major objectives of ESA, NASA and the International
Living with a Star program, in particular Solar Dynamics Observatory,
PICARD, Solar Orbiter, and the Solar Probe missions. Proposals
for optional instruments are also under evaluation: DIMMI-2h, a
double channel MOF based full disk imager operating at 589nm and
770nm, allowing high temporal resolution velocity and magnetic field
measurements; EISR a two channel spectrometer operating in the 50-130
nm wavelength range, and NPA, an in-situ Neutral Particle Analyzer
to detect Energetic Neutral Atoms (ENA). Science objectives related
to optional instruments include: solar high and low-degree p modes
oscillations, EUV solar structures and variability, solar gravitational
red-shift measurement, detection of ENA originating from the plasma
region in the Earth's magnetosphere and undergoing reflection from
the Earth's atmosphere.
Title: Acoustic Shocks in the Quiet Internetwork and the Role of
Magnetic Fields
Authors: Cauzzi, G.; Vecchio, A.; Reardon, K.
Bibcode: 2008ESPM...12.2.37C
Altcode:
By using imaging spectroscopy in the CaII 854.2 nm line obtained with
IBIS over several quiet Sun regions, we present compelling evidence of
acoustic shocks occurring in the quiet chromosphere at the dominant
3-minute periodicity. The shocks present many of the characteristics
prescribed in 1-D hydrodynamics models, including a mostly vertical
propagation of the disturbance from regions of enhanced photospheric
velocity at periodicities close to the acoustic cut-off. Our most
interesting result, however, is the large influence that magnetic
structures exert on the development of chromospheric shocks. In
particular, shocks are essentially absent from extended regions
around magnetic network elements, creating the so-called "magnetic
shadows". These areas coincide with the presence of chromospheric
fibrils rooted in the network itself, that apparently absorb or
otherwise modify the upward propagating acoustic waves, inhibiting
the formation of shocks. Intriguingly, we also find a clear
reduction in the number of shocks observed in quiet internetwork areas
whenever small magnetic structures are seen in MDI HR maps. This is
true even when strong photospheric motions at the relevant periods
are present. This might imply the need to reevaluate the acoustic
contribution to the observed chromospheric "basal" flux.
Title: Chromospheric Counterparts of UV Explosive Events
Authors: Reardon, K.; Cauzzi, G.; Teriaca, L.; Pitterle, M.; Curdt, W.
Bibcode: 2008ESPM...12.2.17R
Altcode:
We present a study of a unique, multi-wavelength dataset of a quiet
sun region with the primary goal of studying explosive events at
chromospheric and transition region heights. Several hypotheses
have been made about the nature of the explosive events, however the
underlying mechanisms remain elusive due to their small spatial and
temporal scales. Several theoretical models predict an important
role for the chromosphere in the triggering of these events. To shed light on this issue, we have obtained a comprehensive
set of simultaneous high spatial, spectral, and temporal resolution
observations on April 18, 2007, combining both ground- and space-based
observatories. Most importantly, we carried out coordinated observations
with SUMER in the transition region Si IV 140.2 nm line together
with high-cadence IBIS imaging spectroscopy of the chromospheric CaII
854.2 nm line. This allows us to examine the chromospheric dynamics
and acoustic shocks that underlie the transition region events. We
also use SOT/NFI magnetograms to examine the relation of the explosive
events to the changes in the magnetic topology. The combined dataset
also includes Hinode/EIS rasters and Hinode/XRT images that provide
information on the higher-temperature coronal response.
Title: On the Role of Acoustic-gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; Cauzzi, G.; McIntosh,
S. W.; Reardon, K.; Severino, G.; Steffen, M.; Suter, M.; Tarbell,
T. D.
Bibcode: 2008ESPM...12.2.11S
Altcode:
We revisit the dynamics and energetics of the solar atmosphere, using a
combination of high-quality observations and 3D numerical simulations
of the overshoot region of compressible convection into the stable
photosphere. We discuss the contribution of acoustic-gravity waves
to the energy balance of the photosphere and low chromosphere. We
demonstrate the presence of propagating internal gravity waves at
low frequencies (< 5mHz). Surprisingly, these waves are found
to be the dominant phenomenon in the quiet middle/upper photosphere
and to transport a significant amount of mechanical energy into the
atmosphere outweighing the contribution of high-frequency (> 5mHz)
acoustic waves by more than an order of magnitude. We compare the
properties of high-frequency waves in the simulations with results
of recent high cadence, high resolution Doppler velocity measurements
obtained with SOT/SP and SOT/NFI on Hinode. Our results seem to be in
conflict with the simple picture of upward propagating sound waves. We
discuss the implications of our findings on the energy flux estimate
at high-frequencies.
Title: Physical Properties of Chromospheric Structures in H-alpha
and and CaII 854.2 nm
Authors: Bostanci, Z. F.; Rutten, R., R. Jtenbroek, H.; Reardon, K.;
Cauzzi, G.
Bibcode: 2008ESPM...12.2.45B
Altcode:
Comprehensive studies of chromospheric structures are the key to
understanding their dynamics in different solar regimes and their
contribution in heating of the solar atmosphere. High spatial and
spectral resolution observations of a quiet chromospheric region
were obtained with the Interferometric BIdimensional Spectrometer
(IBIS) installed at the Dunn Solar Telescope (DST) of the National
Solar Observatory (NSO) on Sacramento Peak, USA. Chromospheric fibrils
that were observed simultaneously in the Balmer H? and CaII 854.2 nm
line are analysed using the cloud model technique to derive numerical
values for the standard cloud model parameters; optical thickness,
source function, Dopplerwidth and Dopplershift for the two lines,
enabling detailed comparison between these.
Title: The Energy Flux of Internal Gravity Waves in the Lower Solar
Atmosphere
Authors: Straus, Thomas; Fleck, Bernhard; Jefferies, Stuart M.;
Cauzzi, Gianna; McIntosh, Scott W.; Reardon, Kevin; Severino, Giuseppe;
Steffen, Matthias
Bibcode: 2008ApJ...681L.125S
Altcode:
Stably stratified fluids, such as stellar and planetary atmospheres,
can support and propagate gravity waves. On Earth these waves,
which can transport energy and momentum over large distances and can
trigger convection, contribute to the formation of our weather and
global climate. Gravity waves also play a pivotal role in planetary
sciences and modern stellar physics. They have also been proposed
as an agent for the heating of stellar atmospheres and coronae, the
exact mechanism behind which is one of the outstanding puzzles in solar
and stellar physics. Using a combination of high-quality observations
and 3D numerical simulations we have the first unambiguous detection
of propagating gravity waves in the Sun's (and hence a stellar)
atmosphere. Moreover, we are able to determine the height dependence of
their energy flux and find that at the base of the Sun's chromosphere it
is around 5 kW m-2. This amount of energy is comparable to
the radiative losses of the entire chromosphere and points to internal
gravity waves as a key mediator of energy into the solar atmosphere.
Title: Search for High Velocities in the Disk Counterpart of Type
II Spicules
Authors: Langangen, Ø.; De Pontieu, B.; Carlsson, M.; Hansteen,
V. H.; Cauzzi, G.; Reardon, K.
Bibcode: 2008ApJ...679L.167L
Altcode: 2008arXiv0804.3256L
Recently, De Pontieu and coworkers discovered a class of spicules
that evolve more rapidly than previously known spicules, with rapid
apparent motions of 50-150 km s-1, thickness of a few 100
km, and lifetimes of order 10-60 s. These so-called type II spicules
have been difficult to study because of limited spatiotemporal and
thermal resolution. Here we use the IBIS instrument to search for the
high velocities in the disk counterpart of type II spicules. We have
detected rapidly evolving events, with lifetimes that are less than a
minute and often equal to the cadence of the instrument (19 s). These
events are characterized by a Doppler shift that only appears in the
blue wing of the Ca II IR line. Furthermore, the spatial extent,
lifetime, and location near network all suggest a link to type II
spicules. However, the magnitude of the measured Doppler velocity is
significantly lower than the apparent motions seen at the limb. We
use Monte Carlo simulations to show that this discrepancy can be
explained by a forward model in which the visibility on the disk of
the high-velocity flows in these events is limited by a combination
of line-of-sight projection and reduced opacity in upward propelled
plasma, especially in reconnection driven jets that are powered by a
roughly constant energy supply.
Title: Solar Chromospheric Dynamics: Onwards and Upwards
Authors: Cauzzi, G.; Reardon, K.; Rimmele, T.; Rutten, R.; Tritschler,
A.; Uitenbroek, H.; Woeger, F.
Bibcode: 2008AGUSMSP41B..03C
Altcode:
We present a study of chromospheric dynamics and its relation with the
driving photospheric magneto-convection in a variety of solar targets,
from quiet Sun to more active regions. To this end high resolution
observations were obtained in CaII 854.2 nm, Hα, and photospheric
FeI lines with the Interferometric BIdimensional Spectrometer (IBIS)
installed at the Dunn Solar Telescope of the NSO. The availability of
full spectroscopic information on extended fields of view allows us
to derive a comprehensive view of the intrinsically 3-D chromospheric
scene. A coherent picture is emerging that involves the propagation
and dissipation of photospheric acoustic waves into the chromospheric
layers, but selected and guided by the local and highly variable
magnetic topology. In particular, ubiquitous fibrilar structures,
apparently originating from even the smallest magnetic elements,
appear an integral part of the dynamic chromosphere.
Title: WHI Targeted Campaigns on Coronal Holes and Quiet Sun: High
Resolution Observations of the Lower Atmosphere With IBIS
Authors: Cauzzi, G.; Reardon, K. P.; Rimmele, T.; Tritschler, A.;
Uitebroek, H.; Woeger, F.; Deforest, C.; McIntosh, S.
Bibcode: 2008AGUSMSH51A..02C
Altcode:
The Interferometric BIdimensional Spectrometer (IBIS) is a dual
Fabry-Perot instrument installed at the Dunn Solar Telescope that allows
two-dimensional spectroscopic observations in a variety of spectral
lines. The IBIS/DST will participate in the WHI targeted campaigns
on coronal holes (April 3-9) and quiet Sun dynamics (April 10-16)
performing simultaneous high-resolution observations of the dynamics of
the photosphere and chromosphere in the coordinated targets. The aim is
to obtain insights on the role of the lower atmosphere's dynamics and
energetics into the structuring of the coronal plasma and, possibly,
into the origin of the solar wind. In this paper we will present the
observations obtained as well as first results, and attempt to relate
them with recent work performed on quiet Sun chromospheric dynamics.
Title: The solar chromosphere at high resolution with IBIS. I. New
insights from the Ca II 854.2 nm line
Authors: Cauzzi, G.; Reardon, K. P.; Uitenbroek, H.; Cavallini, F.;
Falchi, A.; Falciani, R.; Janssen, K.; Rimmele, T.; Vecchio, A.;
Wöger, F.
Bibcode: 2008A&A...480..515C
Altcode: 2007arXiv0709.2417C
Context: The chromosphere remains a poorly understood part of the solar
atmosphere, as current modeling and observing capabilities are still
ill-suited to investigating its fully 3-dimensional nature in depth. In
particular, chromospheric observations that can preserve high spatial
and temporal resolution while providing spectral information over
extended fields of view are still very scarce.
Aims: In this
paper, we seek to establish the suitability of imaging spectroscopy
performed in the Ca II 854.2 nm line as a means of investigating
the solar chromosphere at high resolution.
Methods: We utilize
monochromatic images obtained with the Interferometric BIdimensional
Spectrometer (IBIS) at multiple wavelengths within the Ca II 854.2 nm
line and over several quiet areas. We analyze both the morphological
properties derived from narrow-band monochromatic images and the
average spectral properties of distinct solar features such as network
points, internetwork areas, and fibrils.
Results: The spectral
properties derived over quiet-Sun targets are in full agreement with
earlier results obtained with fixed-slit spectrographic observations,
highlighting the reliability of the spectral information obtained
with IBIS. Furthermore, the very narrowband IBIS imaging reveals very
clearly the dual nature of the Ca II 854.2 nm line. Its outer wings
gradually sample the solar photosphere, while the core is a purely
chromospheric indicator. The latter displays a wealth of fine structures
including bright points akin to the Ca II H{2V} and K{2V} grains, and
as fibrils originating from even the smallest magnetic elements. The
fibrils occupy a large fraction of the observed field of view, even
in the quiet regions, and clearly outline atmospheric volumes with
different dynamical properties, strongly dependent on the local magnetic
topology. This highlights how 1D models stratified along the vertical
direction can provide only a very limited representation of the actual
chromospheric physics.
Conclusions: Imaging spectroscopy in the
Ca II 854.2 nm line currently represents one of the best observational
tools for investigating the highly structured and highly dynamical
chromospheric environment. A high-performance instrument such as IBIS
is crucial in achieving the necessary spectral purity and stability,
spatial resolution, and temporal cadence. Two movies are only
available in electronic form at http://www.aanda.org
Title: Comparison of spatially and spectrally resolved solar data
with numerical simulations
Authors: Cauzzi, G.; Asensio Ramos, A.; Reardon, K. P.; Janssen, K.
Bibcode: 2007IAUS..239..138C
Altcode:
No abstract at ADS
Title: Reversed granulation in mid-photosphere of the Sun
Authors: Janssen, Katja; Cauzzi, Gianna
Bibcode: 2007IAUS..239..163J
Altcode:
No abstract at ADS
Title: Acoustic Shocks in the Quiet Solar Chromosphere
Authors: Cauzzi, G.; Reardon, K. P.; Vecchio, A.; Janssen, K.;
Rimmele, T.
Bibcode: 2007ASPC..368..127C
Altcode:
We exploit the two-dimensional spectroscopic capabilities of the
Interferometric BIdimensional Spectrometer (IBIS) to study the
chromospheric Ca II 854.2 nm line and its temporal evolution in a quiet
region at the center of the solar disk. The Ca II 854.2 profiles in the
internetwork portion of the field of view clearly indicate the presence
of hydrodynamic shocks, occurring at frequencies above the acoustic
cut-off. The location and strength of such shocks perfectly map
the areas where large velocity power is found at frequencies of 5.5-8
mHz in a standard Fourier analysis. The shocks locations evidence a
sharp partition of the quiet area in regions of very distinct dynamical
behavior, highlighting the role of the local magnetic topology in
structuring the lower chromosphere. The portions of the field of view
where the photospheric field is very weak, and that are presumably
connected to distant magnetic structures (or open to the interplanetary
field), are the site of frequent shock occurrence. On the contrary, in
regions neighboring the magnetic network and harboring a more horizontal
configuration of the chromospheric magnetic field, shocks are heavily
suppressed, even if the photospheric field is essentially absent in
these areas as well. These latter regions, with much reduced velocity
power at frequencies of 5.5-8 mHz \citep[the ``magnetic shadows'' first
described in][]{gc-judge_01}, are spatially coincident with fibrilar
structures visible in the Ca II 854.2 line core intensity maps. We
finally argue that areas within and immediately surrounding the magnetic
network also display evidence of chromospheric shocks, but occurring at
periodicities of 4-6 minutes. Such slow shocks are stronger than those
occurring in field-free areas, as evidenced by the strong emission
in the inner blue-wing of the line. This is in agreement with recent
results claiming that magneto-acoustic shocks can develop in inclined
magnetic structures, acting as `portals' through which the powerful
low-frequency photospheric oscillations can leak into the chromosphere.
Title: Comparison of Ca II K and Ca II 8542 Å Images
Authors: Reardon, K. P.; Cauzzi, G.; Rimmele, T.
Bibcode: 2007ASPC..368..151R
Altcode:
We compare a time sequence of filtergrams obtained in the Ca II K line
with a series of spectrally resolved images obtained simultaneously
with the IBIS instrument in the Ca II 8542 Å line. Using the
narrowband IBIS images and a synthetic filter profile, we construct
simulated 8542 filtergrams that mimic the observed K2V
filtergrams. We observe that these filtergrams appear to contain
elements corresponding to both photospheric and chromospheric
structures. Intermediate scale patterns seen in the filtergrams may
simply be the result of the combination of a variety of structures
from different atmospheric levels. We analyze the Fourier power
spectra of the filtergrams and note that at frequencies well above
the acoustic cut-off value the observed power in the K2V
filtergrams seems to be predominantly photospheric in origin. The use
of Ca II H and K filtergrams to study the chromospheric behavior thus
may be inherently problematic. Narrowband images in the Ca II 8542 Å
line might provide a better source of information about chromospheric
behavior with little loss in spatial or temporal resolution.
Title: Commission 12: Solar Radiation & Structure
Authors: Bogdan, Thomas. J.; Martínez Pillet, Valentin; Asplund,
M.; Christensen-Dalsgaard, J.; Cauzzi, G.; Cram, L. E.; Dravins, D.;
Gan, W.; Henzl, P.; Kosovichev, A.; Mariska, J. T.; Rovira, M. G.;
Venkatakrishnan, P.
Bibcode: 2007IAUTA..26...89B
Altcode:
Commission 12 covers research on the internal structure and dynamics
of the Sun, the "quiet" solar atmosphere, solar radiation and its
variability, and the nature of relatively stable magnetic structures
like sunspots, faculae and the magnetic network. There is considerable
productive overlap with the other Commissions of Division II as
investigations move progressively toward the fertile intellectual
boundaries between traditional research disciplines. In large part,
the solar magnetic field provides the linkage that connects these
diverse themes. The same magnetic field that produces the more subtle
variations of solar structure and radiative output over the 11 yr
activity cycle is also implicated in rapid and often violent phenomena
such as flares, coronal mass ejections, prominence eruptions, and
episodes of sporadic magnetic reconnection.The last three years have
again brought significant progress in nearly all the research endeavors
touched upon by the interests of Commission 12. The underlying causes
for this success remain the same: sustained advances in computing
capabilities coupled with diverse observations with increasing levels
of spatial, temporal and spectral resolution. It is all but impossible
to deal with these many advances here in anything except a cursory and
selective fashion. Thankfully, the Living Reviews in Solar Physics; has
published several extensive reviews over the last two years that deal
explicitly with issues relevant to the purview of Commission 12. The
reader who is eager for a deeper and more complete understanding of
some of these advances is directed to http://www.livingreviews.org
for access to these articles.
Title: Solar atmospheric oscillations and the chromospheric magnetic
topology
Authors: Vecchio, A.; Cauzzi, G.; Reardon, K. P.; Janssen, K.;
Rimmele, T.
Bibcode: 2007A&A...461L...1V
Altcode: 2006astro.ph.11206V
Aims:We investigate the oscillatory properties of the quiet solar
chromosphere in relation to the underlying photosphere, with particular
regard to the effects of the magnetic topology.
Methods: For the
first time we perform a Fourier analysis on a sequence of line-of-sight
velocities measured simultaneously in a photospheric (Fe I 709.0 nm)
and a chromospheric line (Ca II 854.2 nm). The velocities were obtained
from full spectroscopic data acquired at high spatial resolution with
the Interferometric BIdimensional Spectrometer (IBIS). The field of
view encompasses a full supergranular cell, allowing us to discriminate
between areas with different magnetic characteristics.
Results: We
show that waves with frequencies above the acoustic cut-off propagate
from the photosphere to upper layers only in restricted areas of
the quiet Sun. A large fraction of the quiet chromosphere is in fact
occupied by “magnetic shadows”, surrounding network regions, that
we identify as originating from fibril-like structures observed in
the core intensity of the Ca II line. We show that a large fraction
of the chromospheric acoustic power at frequencies below the acoustic
cut-off, residing in the proximity of the magnetic network elements,
directly propagates from the underlying photosphere. This supports
recent results arguing that network magnetic elements can channel
low-frequency photospheric oscillations into the chromosphere, thus
providing a way to input mechanical energy in the upper layers.
Title: Reversed granulation in Fe I 7090.4Å
Authors: Janssen, K.; Cauzzi, G.
Bibcode: 2007msfa.conf..135J
Altcode:
The reversal of the photospheric continuum intensity pattern is
predicted by numerical simulations and has been observed in the wings of
chromospheric lines. Here we present reversed granulation extracted from
the photospheric Fe I 7090.4 Å line core intensities, after taking into
account the velocity effects, in high spatial, spectral and temporal
resolution. We study correlations with the underlying continuum in terms
of smoothing, time delays and the temporal evolution. The latter appears
to be superimposed with an oscillatory signal, that might suggest the
presence of gravity waves in the observed mid-photospheric layers.
Title: IBIS: Reversed Granulation in the Quiet Photosphere
Authors: Janssen, K.; Cauzzi, G.
Bibcode: 2006ASPC..354...49J
Altcode:
The phenomenon of ``reversed granulation'', i.e. the partial reversal
of the intensity pattern occurring in the low photosphere, is predicted
by numerical simulations and mostly observed in the extended wings
of chromospheric lines. In this contribution we present high spatial
resolution 2D maps of the reversed granulation, obtained from line
core images of the photospheric Fe I 7090.4 Å line, as well as the
temporal evolution of their correlation with continuum maps, that
suggests the presence of gravity waves in the mid-photosphere.
Title: High-resolution IBIS Observations and Comparison with 3D
Simulations
Authors: Cauzzi, G.; Asensio Ramos, A.; Reardon, K.; Janssen, K.
Bibcode: 2006ASPC..354...26C
Altcode:
We present first comparisons between high resolution observations of
the quiet photosphere, obtained with the Interferometric BIdimensional
Spectrometer (IBIS) in the non-magnetic Fe I 7090.4 Å spectral
line, and the synthetic spectrum calculated for a 3D snapshot of a
radiation-hydrodynamical simulation of the solar atmosphere. Together
with morphological comparisons between the synthetic images and the
observed ones at different wavelengths, we have carried out comparisons
between several observables. The simulations reproduce quite well
many of the observational properties of the high resolution IBIS data,
apart from the velocity distribution, that contains values quite larger
than observed.
Title: Dynamics and evolution of an eruptive flare
Authors: Teriaca, L.; Falchi, A.; Falciani, R.; Cauzzi, G.;
Maltagliati, L.
Bibcode: 2006A&A...455.1123T
Altcode: 2009arXiv0903.0232T
Aims.We study the dynamics and the evolution of a C2.3 two-ribbon
flare, developed on 2002 August 11, during the impulsive phase
as well as during the long gradual phase. To this end we obtained
multiwavelength observations using the CDS spectrometer aboard SOHO,
facilities at the National Solar Observatory/Sacramento Peak, and the
TRACE and RHESSI spacecrafts.
Methods: .CDS spectroheliograms
in the Fe xix, Fe xvi, O v and He i lines allow us to determine the
velocity field at different heights/temperatures during the flare
and to compare them with the chromospheric velocity fields deduced
from Hα image differences. TRACE images in the 17.1 nm band greatly
help in determining the morphology and the evolution of the flaring
structures.
Results: .During the impulsive phase a strong
blue-shifted Fe xix component (-200 km s-1) is observed at
the footpoints of the flaring loop system, together with a red-shifted
emission of O v and He i lines (20 km s-1). In one footpoint
simultaneous Hα data are also available and we find, at the same time
and location, downflows with an inferred velocity between 4 and 10 km
s-1. We also verify that the "instantaneous" momenta of the
oppositely directed flows detected in Fe xix and Hα are equal within
one order of magnitude. These signatures are in general agreement with
the scenario of explosive chromospheric evaporation. Combining RHESSI
and CDS data after the coronal upflows have ceased, we prove that,
independently from the filling factor, an essential contribution to
the density of the post-flare loop system is supplied from evaporated
chromospheric material. Finally, we consider the cooling of this loop
system, that becomes successively visible in progressively colder
signatures during the gradual phase. We show that the observed cooling
behaviour can be obtained assuming a coronal filling factor of ≈0.2
to 0.5.
Title: The Interferometric Bidimensional Spectrometer (IBIS)
Authors: Cauzzi, Gianna; Cavallini, F.; Reardon, K.; Berrilli, F.;
Rimmele, T.; IBIS Team
Bibcode: 2006SPD....37.0608C
Altcode: 2006BAAS...38..226C
The Interferometric Bidimensional Spectrometer (IBIS) is an advanced
instrument for imaging spectroscopy installed at the Dunn Solar
Telescope at NSO/Sacramento Peak. The instrument has been constructed by
a consortium of italian institutes and allows for observations of the
photosphere and chromosphere at high spatial, spectral, and temporal
resolution. Such observations are essential for performing spatial
and spectral comparisons with numerical simulations. We will present
some of the performance characteristics of the instrument and show some
examples of the IBIS data. We will also show some initial results of the
recently tested polarimetric mode. IBIS is available for community use
as a facility instrument of NSO.IBIS has been funded by the Italian
Research Ministry (MIUR), the Italian Institute for Astrophysics
(INAF), and the Universities of Florence and Rome. Additional support
is provided by the National Solar Observatory.
Title: Dynamics of the solar photosphere with IBIS. I. Reversed
intensity structure in the mid-photosphere
Authors: Janssen, K.; Cauzzi, G.
Bibcode: 2006A&A...450..365J
Altcode:
Context: .We investigate the quiet solar photosphere with the new
Interferometric BI-dimensional Spectrometer (IBIS), recently installed
at the Dunn Solar Telescope of the National Solar Observatory,
Sacramento Peak, NM.
Aims: . We study the occurrence of reverse
granulation in the mid-photosphere, and its properties.
Methods:
. IBIS, a double Fabry-Perot system with a narrow passband of 20 mÅ
at 6000 Å was used to acquire a one hour sequence of 2D scans in
the photospheric Fe I 7090.4 Å and Fe II 7224.5 Å lines, and in the
chromospheric Ca II 8542 Å line. Photospheric velocities are measured
for statistical study. To visualize the reversed intensity structure,
the influence of velocity on the steep photospheric profiles is taken
into account. The correlation between mid-photospheric intensities and
continuum is then studied, considering the effects of spatial smoothing
and time delay. The temporal evolution of the cross-correlation
coefficients is analyzed.
Results: . The distribution of
photospheric velocities is consistent with values in the literature,
thus confirming the reliability of the instrument for this kind of
study. "Reversed granulation" is clearly visible in the Fe I 7090.4 Å
line center, formed at about 200 km. It provides a weak anti-correlation
with the continuum, as expected from numerical simulations. Images
acquired in the far wings of the Ca II line display the same pattern
with a slightly higher correlation. In both cases a spatial smoothing
larger than 0.5'' decreases the level of anti-correlation, while a
time delay of about 2 min increases it. Together, these facts suggest
that the phenomenon is mainly due to a reversal of temperature
fluctuations between granules and intergranules, occurring in the
mid-photosphere. The temporal evolution of the anti-correlation between
the Fe I line center and the continuum reveals a clear oscillatory
signal that we consider as highly suggestive of the presence of gravity
waves developing from the mid-photosphere outwards.
Title: High-resolution IBIS Observations and Comparison with 3D
Simulations .
Authors: Asensio Ramos, A.; Janssen, K.; Cauzzi, G.; Reardon, K.
Bibcode: 2006MSAIS...9...59A
Altcode:
High resolution observations of a very quiet region of the solar
surface have been obtained with IBIS (Interferometric BIdimensional
Spectrometer) in the non-magnetic Fe I 7090.4 Å spectral line. We
present a first comparison between the observed, spatially resolved,
spectral data and the simulated spectra in a 3D snapshot of a
radiation-hydrodynamical simulation of the solar atmosphere. Preliminary
results indicate that the simulations reproduce quite well many of
the observational properties of the high resolution IBIS data, even
though the simulations present a velocity distribution that contains
values quite larger than the observed ones.
Title: Quiet Solar Photosphere: Comparisons of High Resolution
Observations with 3-D Simulations
Authors: Cauzzi, G.; Asensio Ramos, A.; Reardon, K.; Janssen, K.
Bibcode: 2005ESASP.600E..12C
Altcode: 2005dysu.confE..12C; 2005ESPM...11...12C
No abstract at ADS
Title: Helium line formation in a solar active region
Authors: Mauas, P. J. D.; Andretta, V.; Falchi, A.; Falciani, R.;
Teriaca, L.; Cauzzi, G.
Bibcode: 2005ESASP.560..811M
Altcode: 2005csss...13..811M
No abstract at ADS
Title: Helium Line Formation and Abundance in a Solar Active Region
Authors: Mauas, P. J. D.; Andretta, V.; Falchi, A.; Falciani, R.;
Teriaca, L.; Cauzzi, G.
Bibcode: 2005ApJ...619..604M
Altcode: 2004astro.ph.12058M
An observing campaign (SOHO JOP 139), coordinated between ground-based
and Solar and Heliospheric Observatory (SOHO) instruments, has been
planned to obtain simultaneous spectroheliograms of the same active
region in several spectral lines. The chromospheric lines Ca II K,
Hα, and Na I D, as well as He I 10830, 5876, 584, and He II 304 Å
lines have been observed. The EUV radiation in the range λ<500
Å and in the range 260<λ<340 Å has also been measured at
the same time. These simultaneous observations allow us to build
semiempirical models of the chromosphere and low transition region of
an active region, taking into account the estimated total number of
photoionizing photons impinging on the target active region and their
spectral distribution. We obtained a model that matches very well all
the observed line profiles, using a standard value for the He abundance
([He]=0.1) and a modified distribution of microturbulence. For this
model we study the influence of the coronal radiation on the computed
helium lines. We find that, even in an active region, the incident
coronal radiation has a limited effect on the UV He lines, while it
is of fundamental importance for the D3 and 10830 Å lines. Finally,
we build two more models, assuming values of He abundance [He]=0.07 and
1.5, only in the region where temperatures are >1×104
K. This region, between the chromosphere and transition region, has been
indicated as a good candidate for processes that might be responsible
for strong variations of [He]. The set of our observables can still be
well reproduced in both cases, changing the atmospheric structure mainly
in the low transition region. This implies that, to choose between
different values of [He], it is necessary to constrain the transition
region with different observables, independent of the He lines.
Title: Overview of AN Eruptive Flare: from Chromospheric Evaporation
to Cooling of Hot Flaring Loops
Authors: Teriaca, L.; Maltagliati, L.; Falchi, A.; Falciani, R.;
Cauzzi, G.
Bibcode: 2004ESASP.575..265T
Altcode: 2004soho...15..265T
No abstract at ADS
Title: IBIS Observations of Quiet Sun Photosphere - Velocity Structure
from Fe I 7090.4 Å
Authors: Janßen, Katja; Cauzzi, Gianna; Falchi, Ambretta; Cavallini,
Fabio; Reardon, Kevin
Bibcode: 2004IAUS..223..631J
Altcode: 2005IAUS..223..631J
In our contribution we introduce the new Interferometric BIdimensional
Spectrometer (IBIS) and present the first results on bisector velocities
of two dimensional spectral scans in FeI 7090.4 Å comparing granules
and intergranular regions.
Title: Solar and Heliospheric Observatory/Coronal Diagnostic
Spectrograph and Ground-based Observations of a Two-Ribbon Flare:
Spatially Resolved Signatures of Chromospheric Evaporation
Authors: Teriaca, L.; Falchi, A.; Cauzzi, G.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
Bibcode: 2003ApJ...588..596T
Altcode:
During a coordinated observing campaign (Solar and Heliospheric
Observatory, SOHO JOP 139), we obtained simultaneous spectroheliograms
of a solar active region in several spectral lines, sampling levels
from the chromosphere to the corona. Ground-based spectroheliograms
were acquired at the Dunn Solar Tower of the National Solar
Observatory/Sacramento Peak in four chromospheric lines, while the
coronal diagnostic spectrograph on board SOHO was used to obtain
rasters of the active region in transition region (TR) and coronal
lines. Such a complete data set allowed us to compare the development
of intensity and velocity fields during a small two-ribbon flare
in the whole atmosphere. In particular, we obtained for the first
time quasi-simultaneous and spatially resolved observations of
velocity fields during the impulsive phase of a flare, in both the
chromosphere and upper atmosphere. In this phase, strong downflows
(up to 40 km s-1) following the shape of the developing
ribbons are measured at chromospheric levels, while strong upward
motions are instead measured in TR (up to -100 km s-1)
and coronal lines (-160 km s-1). The spatial pattern of
these velocities have a common area about 10" wide. This is the first
time that opposite-directed flows at different atmospheric levels
are observed in the same spatial location during a flare. These
signatures are highly suggestive of the chromospheric evaporation
scenario predicted in theoretical models of flares.
Title: Mass Motions in a Young Active Region
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.; Smaldone, L. A.
Bibcode: 2003MmSAI..74..659C
Altcode:
We present an observational program devoted to the study of dynamic
phenomena at small spatial and temporal scales throughout the solar
atmosphere, with special attention to chromospheric events that have
an impact on the coronal structure. On the one hand, we show the
existence of flare signatures in the chromosphere at the smallest
scales, supporting the idea that (micro)flares represent a viable
mechanism for supply of heat and mass to the corona. On the other,
such events are quite scarce in our dataset, while much more common
are surge-like events, occurring repeatedly in the same locations
and visible both in the chromosphere and the corona, and that do not
display obvious flare signatures.
Title: Spatially resolved signatures of chromospheric evaporation
during a small two-ribbon flare
Authors: Teriaca, L.; Falchi, A.; Cauzzi, G.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
Bibcode: 2003MmSAI..74..635T
Altcode:
Ground based spectroheliograms of a solar active region were acquired
in four chromospheric lines simultaneously with rasters in transition
region (TR) and coronal lines obtained with the Coronal Diagnostic
Spectrograph (CDS) aboard SOHO. Such a complete dataset allows us to
study the development of intensity and velocity fields during a small
two-ribbon flare in the whole atmosphere. In particular, we obtain for
the first time quasi-simultaneous and spatially resolved observations
of velocity fields during the impulsive phase of a flare, both in
chromosphere and upper atmosphere. In this phase, strong downflows
(up to 40 km s-1) following the shape of the developing
ribbons are measured at chromospheric levels, while strong upward
motions are measured in TR (up to -100 km s-1) and coronal
lines (-160 km s-1). The spatial pattern of these velocities
have a common area about 10 arcsec wide. This is the first time that
opposite directed flows at different atmospheric levels are observed
in the same spatial location during a flare. These signatures are
highly suggestive of the chromospheric evaporation scenario predicted
in theoretical models of flares.
Title: Chromospheric and Transition region He lines during a flare
Authors: Falchi, A.; Mauas, P. J. D.; Andretta, V.; Teriaca, L.;
Cauzzi, G.; Falciani, R.; Smaldone, L. A.
Bibcode: 2003MmSAI..74..639F
Altcode:
An observing campaign (SOHO JOP 139), coordinated between ground
based and SOHO instruments, has been planned to obtain simultaneous
spectroheliograms of the same area in several spectral lines. The
chromospheric lines Ca II K, Hα and Na I D as well as He I 10830,
5876, 584 and 304 Ålines have been observed. These observations allow
us to build semi-empirical models of the atmosphere before and during
a small flare. With these models, constructed to match the observed
line profiles, we can test the He abundance value.
Title: Chromospheric evaporation in a two-ribbon flare
Authors: Cauzzi, G.; Falchi, A.; Teriaca, L.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
Bibcode: 2002ESASP.506..561C
Altcode: 2002ESPM...10..561C; 2002svco.conf..561C
We present simultaneous, spatially and temporally resolved
chromospheric, transition region and coronal observations of a small
eruptive flare studied throughout its whole development. We show
that strong and co-spatial plasma motions, oppositely directed in the
chromosphere (downflows) and in upper atmospheric layers (upflows),
develop at the onset of the flare. For the first time, we prove that
such oppositely directed flows originate from the same flaring kernels
in different atmospheric layers. Using realistic values for the plasma
parameters in the flaring loop, we also estimate a balance between
the upward and downward momenta. Our observations confirm in a very
convincing way the scenario of chromospheric evaporation predicted in
theoretical models of flares.
Title: Combined space and ground based observations of a C-1 flare
Authors: Teriaca, L.; Falchi, A.; Cauzzi, G.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
Bibcode: 2002ESASP.508..457T
Altcode: 2002soho...11..457T
We present temporally and spatially resolved space and ground based
observations of a C1 flare. Ground based spectroheliograms were acquired
at the Dunn Solar Tower of NSO/Sacramento Peak in several chromospheric
lines. Simultaneously, the Coronal Diagnostic Spectrograph (CDS)
aboard SoHO was used to obtrain rasters of the same active region
in transiton region (TR) and coronal lines. This unique dataset
provides us, for the first time, with spatially resolved observations
of velocity fields during the impulsive phase of the flare, from the
chromosphere up to the TR and the corona. At the time of the emission
peak, a large area of the flaring kernel observed in TR lines is
characterized by upward velocities. A ~6"×6" kernel displays upflows
velocity above 80 km s-1. In this same area we found, in
data obtained about 3 minutes later, chromospheric downflows of 10 -
20 km s-1. This is the first time that opposite directed
flows at different atmospheric levels are observed in the same spatial
location during a flare.
Title: Introduction (JOSO Annual Report 2000/2001)
Authors: Cauzzi, G.
Bibcode: 2002joso.book....1C
Altcode:
No abstract at ADS
Title: Minutes of the 33rd JOSO Board Meeting - 2001
Authors: Cauzzi, G.; Kucera, A.; Schmieder, B.
Bibcode: 2002joso.book...15C
Altcode:
No abstract at ADS
Title: European Solar Magnetism Network
Authors: Cauzzi, G.
Bibcode: 2002joso.book....8C
Altcode:
No abstract at ADS
Title: Minutes of the 32nd JOSO Board Meeting - 2000
Authors: Cauzzi, G.; Kucera, A.; Schmieder, B.
Bibcode: 2002joso.book...10C
Altcode:
No abstract at ADS
Title: Search for Microflaring Activity in the Magnetic Network
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.
Bibcode: 2001SoPh..199...47C
Altcode: 2000astro.ph.11433C
We analyze the temporal behavior of network bright points (NBPs)
searching for low-atmosphere signatures of flares occurring
on the magnetic network. We make use of a set of data acquired
during coordinated observations between ground-based observatories
(NSO/Sacramento Peak) and the MDI instrument on board SOHO. Light curves
in chromospheric spectral lines show only small-amplitude temporal
variations, without any sudden intensity enhancement that could suggest
the presence of a transient phenomenon such as a (micro)flare. Only
one NBP shows spikes of downward velocity, of the order of 2-4 km
s−1, considered as signals of compression associated with
a (micro)flare occurrence. For this same NBP, we also find a peculiar
relationship between the magnetic and velocity fields fluctuations,
as measured by MDI. Only for this point the B−V fluctuations
are well correlated, suggesting the presence of magneto-acoustic
waves propagating along the magnetic structure. This correlation is
lost during the compression episodes and resumes afterward. An A6
GOES soft X-ray burst is temporally associated with the downward
velocity episodes, suggesting that this NBP is the footpoint of a
flaring loop. This event has a total thermal energy content of about
1028 erg, and, hence, belongs to the microflare class.
Title: Network and internetwork properties at photospheric and
chromospheric levels
Authors: Falchi, A.; Cauzzi, G.; Falciani, R.
Bibcode: 2001MmSAI..72..549F
Altcode:
We use coordinated observations between ground-based observatories
(NSO/Sacramento Peak) and the Michelson Doppler Interferometer onboard
SOHO to analyze the characteristics of Network Bright Points (NBPs)
at different atmospheric heights and compare them with those of the
surrounding internetwork areas. We improve on the existing statistics
using a sample of 11 NBPs, and the same number of "test" internetwork
areas, defined in a comparable way. The method we adopted to study
the temporal evolution of NBPs insures that each bright structure is
properly followed in time and position at each height.
Title: Network and internetwork: a compared multiwavelength analysis
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.
Bibcode: 2000A&A...357.1093C
Altcode: 2000astro.ph..4082C
We analyze the temporal behavior of Network Bright Points (NBPs)
using a set of data acquired during coordinated observations between
ground-based observatories (mainly at the NSO/Sacramento Peak) and
the Michelson Doppler Interferometer onboard SOHO. We find that, at
any time during the observational sequence, all the NBPs visible in
the NaD_2 images are co-spatial within 1'' with locations
of enhanced magnetic field. The ``excess'' of NaD_2 intensity in NBPs,
i.e. the emission over the average value of quiet regions, is directly
related to the magnetic flux density. This property implies that, in
analogy with the Ca II K line, the NaD_2 line center emission can be
used as a proxy for magnetic structures. We also compare the oscillation
properties of NBPs and internetwork areas. At photospheric levels no
differences between the two structures are found in power spectra,
but analysis of phase and coherence spectra suggests the presence
of downward propagating waves in the internetwork. At chromospheric
levels some differences are evident in the power spectrum between
NBPs and internetwork. At levels contributing to the NaD_2 emission
the NBPs show a strongly reduced amplitude of oscillations at the p -
mode frequencies. At levels contributing to the Hα \ core emission,
the amplitude of network oscillations is higher than the internetwork
ones. The power spectrum of NBPs at this wavelength shows an important
peak at 2.2 mHz (7 minutes), not present in the internetwork areas. Its
coherence spectrum with Hα \ wings shows very low coherence at this
frequency, implying that the oscillations at these chromospheric levels
are not directly coupled with those present in lower layers.
Title: Is Flaring Activity present in the Chromospheric Network ?
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.; Vial, J. C.
Bibcode: 1999ESASP.448..685C
Altcode: 1999mfsp.conf..685C; 1999ESPM....9..685C
Microflares occurring at coronal levels are one of the mechanisms
proposed for the heating and dynamics of the chromospheric
network. During a SOHO coordinated campaign, we acquired a set
of chromospheric and transition region data, at high temporal and
spatial resolution, that are suitable for such a research. We describe
the characteristics of network points at several heights in the
atmosphere. We look for the presence of signatures typical of flares,
albeit at much smaller scales. Only one, of the 11 network points
analyzed over 1 hr of observations, displays several episodes of red
asymmetry in the H_α wings. These asymmetries can be interpreted
as downward motions induced by the sudden compression of the lower
atmosphere caused by either a particle beam or a conduction front. The
analysis hence suggests that microflaring events in network points
have a low occurrence probability, or that their energy flux is still
below our observational capabilities.
Title: Wavelet Analysis of Spatial Coherent Structures in the
Photosphere
Authors: Pietropaolo, E.; Berrilli, F.; Consolini, G.; Smaldone,
L. A.; Straus, T.; Cauzzi, G.; Bruno, R.; Bavassano, B.
Bibcode: 1999ESASP.448..343P
Altcode: 1999ESPM....9..343P; 1999mfsp.conf..343P
No abstract at ADS
Title: Multiwavelength Analysis of Network Bright Points - Coordinated
Observations SOHO-GBO JOP No 37
Authors: Falchi, A.; Cauzzi, G.; Falciani, R.; Vial, J. -C.
Bibcode: 1999ASPC..184..261F
Altcode:
We analyze the temporal behaviour of Network Bright Points (NBPs)
using a set of data acquired during coordinated observations between
ground based observatories (mainly at the NSO/Sacramento Peak) and the
SUMER and MDI instruments onboard SOHO. We find that, at any time,
all NBPs present in the NaD_2 images are co-spatial within 1" with
locations of enhanced magnetic field density, and that not all the
NBPs identified in the low chromosphere can be identified at higher
levels. We calculate the intensity power spectrum for each NBP in
several low-chromospheric signatures, such as the red wing of Hα,
NaD_2 and Hα line center. The power spectra show no power at the 5.5
mHz frequency, while they display an enhancement at frequencies below
2 mHz, corresponding to periods between 8 and 20 minutes.
Title: Asymmetric Magnetic Field Distribution in Active Regions
Authors: Cauzzi, Gianna; van Driel-Gesztelyi, Lidia
Bibcode: 1998ASPC..140..105C
Altcode: 1998ssp..conf..105C
No abstract at ADS
Title: Properties of solar granulation cells in quiet regions as
derived from a time series of white light images
Authors: Cauzzi, G.; Consolini, G.; Berrilli, F.; Smaldone, L. A.;
Straus, T.; Bavassano, B.; Bruno, R.; Caccin, B.; Carbone, V.; Egidi,
A.; Ermolli, I.; Florio, A.; Pietropaolo, E.
Bibcode: 1998MmSAI..69..647C
Altcode:
No abstract at ADS
Title: Chromospheric evidence for magnetic reconnection in a
two-ribbon flare.
Authors: Falchi, A.; Qiu, J.; Cauzzi, G.
Bibcode: 1998joso.proc..149F
Altcode:
The authors study a two-ribbon flare, observed with both ground and
satellite-based instruments. The most important result of their study
is given by the measure of the chromospheric downflows within several
flaring kernels, heated by a conduction front from the corona. In all
the cases examined, they find a stronger downflow at the outer edge
of the flaring ribbon, on a region only a few arcsec across. They
think that these observations provide a clear evidence of magnetic
reconnection. As explicitly show in recent flare models that consider
heat conduction from the reconnecting site, the conduction front
directly maps only the outer boundary magnetic field lines of the
reconnecting loops. Its effect on the chromospheric layers would be
to compress the plasma, triggering downflows only on the outer edge
on the ribbons, consistently with the authors' observations.
Title: Chromospheric evidence for magnetic reconnection
Authors: Falchi, A.; Qiu, J.; Cauzzi, G.
Bibcode: 1997A&A...328..371F
Altcode:
We study the decay phase of an M2.6 flare, observed with ground
based instruments at NSO/Sac Peak and with the cluster of instruments
onboard Yohkoh. The whole set of chromospheric and coronal data gives a
picture consistent with the classical Kopp-Pneuman model of two-ribbon
flares. We clearly witness new episodes of coronal energy release, most
probably due to magnetic reconnection, during the decaying phase of
the flare. Within the newly created chromospheric ribbons, we identify
several small kernels, footpoints of magnetic loops involved in the
flare, where energy is probably deposited by a conduction front from
coronal sources. The presence of a source (T_e=22 MK, and EM=5.x 10(48)
cm(-3) ) thermally emitting in the 14-23 keV energy band confirms this
hypothesis. A new, interesting observational result is given by the
measure of chromospheric downflows in different parts of the flaring
kernels. For all the cases examined, we find a stronger downflow at
the outer edge of the flaring structure. The flows have amplitude of
tens of km \ s(-1) , over regions only a few arcsec across, and seem
to decrease when the flaring kernels slow their motion on the solar
surface and fade away. We believe that these downflows directly map
the outer boundary magnetic field lines of the reconnecting loops,
as predicted in recent reconnection models that take into account
explicity the effects of heat conduction. The flows represent the
chromospheric counterpart of coronal features observed in soft X-ray
such as cusp-like structures and the temperature stratification in
flaring loop systems. The observed amplitude of these chromospheric
flows could be an important constraint for quantitative modelling of
coronal reconnection mechanisms and their effects on the lower solar
atmosphere.
Title: The Magneto-Optical Filter in Napoli: Perspectives and Test
Observations
Authors: Moretti, P. F.; Severino, G.; Cauzzi, G.; Reardon, K.;
Straus, T.; Cacciani, A.; Marmolino, C.; Oliviero, M.; Smaldone, L. A.
Bibcode: 1997ASSL..225..293M
Altcode: 1997scor.proc..293M
An observing station based on the Magneto-Optical-Filter (MOF)
technology is being installed at Osservatorio Astronomico di
Capodimonte, in Napoli. In this paper, the main characteristics and
goals of this new instrument are discussed, and several velocity and
magnetic observations from a test campaign are shown.
Title: Magnetic reconnection driven by emergence of sheared magnetic
field.
Authors: Schmieder, B.; Aulanier, G.; Demoulin, P.; van
Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Cauzzi, G.
Bibcode: 1997A&A...325.1213S
Altcode:
Recurrent subflares (Class C) were observed in the NOAA 7608 active
region on 27 October 1993. From multi-wavelength observations
(white-light, magnetic field, H-alpha, X-ray), obtained during a
coordinated campaign between Pic du Midi and Yohkoh, it appears that
these flares were double ribbon flares caused by new flux emergence. As
the flare begins, the X-ray emission observed with Yohkoh/SXT is
loop-shaped with the axis almost parallel to the magnetic inversion
line, while during the flare development, X-ray loops appear at the
location of the emerging flux. The extrapolation of the photospheric
magnetic field in a linear force-free field configuration allows
identification of the magnetic configuration given by the flares. The
Hα flare ribbons are located at the intersections of the computed
quasi-separatrice layers (QSLs) with the chromosphere. We show that
the initial loop-shaped X-ray emission region is in fact formed by
several smaller loops directed in a nearly orthogonal direction with
their feet anchored close to or in the Hα ribbons. During the flare
development there are X-ray loops which represent only one foot of
open or largescale magnetic loops. For the studied flares the puzzling
soft X-rays observations could only be understood with the help of Hα
and magnetic data combined with a modeling of the coronal magnetic
field. Further, from the deduced magnetic field topology, the width
of the QSLs and our present knowledge of 3-D magnetic reconnection,
we conclude that the flare was due to magnetic reconnection driven
by emergence of sheared magnetic field impacting in the pre-existing
coronal field.
Title: Multispectral Observations of AN Eruptive Flare
Authors: Qiu, J.; Falchi, A.; Falciani, R.; Cauzzi, G.; Smaldone, L. A.
Bibcode: 1997SoPh..172..171Q
Altcode: 1997ESPM....8..171Q
We analyze the pre-flare and impulsive phase of an eruptive (two-ribbon)
flare at several wavelengths. The total energy (mechanical plus
radiative) released by the flare is 8 x 1030 erg, about a
factor 6 higher than the free magnetic energy (1.3 1030 erg)
estimated from the non-potentiality of the magnetic field configuration
in the flare area. During the impulsive phase, we find a very good time
coincidence between the hard X-ray light curve and the light curves
for 2 small areas (≃ 4″ in size) in the red wing of the Hα line
and in the He-D3 line center. This temporal coincidence is
compatible with the interpretation that hard X-ray emission is produced
by bremsstrahlung of accelerated electron beams striking these dense
areas. For the other regions of the Hα ribbons we find more gradual
light curves, suggesting a different energy transport mechanism such
as conduction.
Title: Dynamics of Minor Solar Activity \newline Coordinated
Observations SOHO-GBO JOP #37
Authors: Cauzzi, G.; Vial, J. C.; Falciani, R.; Falchi, A.; Smaldone,
L. A.
Bibcode: 1997ASPC..118..309C
Altcode: 1997fasp.conf..309C
We present a program for coordinated observations between ground based
observatories, mainly NSO/Sacramento Peak, and several instruments
onboard SOHO (primarily SUMER). The scientific goal is the study of
small activity phenomena, at high spatial and temporal resolution.
Title: Preface
Authors: Cauzzi, G.; Marmolino, C.
Bibcode: 1997MmSAI..68..359C
Altcode:
No abstract at ADS
Title: East-West inclination of field lines in active regions
Authors: Cauzzi, G.; van Driel-Gesztelyi, L.
Bibcode: 1997MmSAI..68..487C
Altcode:
No abstract at ADS
Title: The inconstant Sun. Proceedings. 2nd Napoli Thinkshop on
Physics and Astrophysics, Napoli (Italy), 18 Mar 1996.
Authors: Cauzzi, G.; Marmolino, C.
Bibcode: 1997MmSAI..68..355C
Altcode:
This Thinkshop addresses the problem of the contribution that solar
physics can give to modern physics and astrophysics.
Title: ARTHEMIS: The Archive Project for the IPM and THEMIS
Authors: Reardon, K.; Severino, G.; Cauzzi, G.; Gomez, M. T.; Straus,
T.; Russo, G.; Smaldone, G.; Marmolino, C.
Bibcode: 1997ASPC..118..398R
Altcode: 1997fasp.conf..398R
We describe the plan for ARTHEMIS, the italian archive for THEMIS, from
the point of view of the prospective users of the archive. This archive
is designed to store the data from the Italian Panoramic Monochromator
(IPM) instrument installed on THEMIS as well as the full-disk images
obtained by the telescope. We break the expected users down into
seven categories: a) prospective IPM users; b) campaign planners; c)
data analysts, d) external collaborators; e) instrument monitors, f)
archival observers; and g) the general public.
Title: ARTHEMIS: The archive project for the Italian Panoramic
Monochromator
Authors: Reardon, K.; Severino, G.; Cauzzi, G.; Gomez, M. T.; Straus,
T.; Russo, G.; Smaldone, L. A.; Marmolino, C.
Bibcode: 1997MmSAI..68..499R
Altcode:
No abstract at ADS
Title: The Li I resonance lines in a solar active region.
Authors: Cauzzi, G.; Gomez, M. T.; Severino, G.
Bibcode: 1997joso.proc...57C
Altcode:
No abstract at ADS
Title: 3D Magnetic Reconnection at an X-Ray Bright Point
Authors: Mandrini, C. H.; Démoulin, P.; Van Driel-Gesztelyi, L.;
Schmieder, B.; Cauzzi, G.; Hofmann, A.
Bibcode: 1996SoPh..168..115M
Altcode:
On May 1, 1993, a flaring X-ray bright point (XBP) was observed for
about 16 hours in the old, disintegrating, bipolar active region (AR)
NOAA 7493. During this period, a minor magnetic bipole (1020
Mx) emerged in the region. We have found observational evidence showing
that the XBP brightenings were due to magnetic reconnection between
the new bipole and pre-existing plage fields. The aim of the present
work is to substantiate with magnetic modelling what has been shown
by the observations. For this purpose we extrapolate the observed
photospheric magnetic fields in the linear force-free approximation
and follow its evolution during the lifetime of the XBP. From the
computed coronal field lines we determine the location of regions of
drastic change in field-line linkage, called `quasi-separatrix layers'
or QSLs. QSLs are open layers that behave physically like separatrices:
the break down of ideal magnetohydrodynamics and the release of free
magnetic energy may occur at these locations when their thickness
is small enough. The extrapolated field lines, with photospheric
footpoints on both sides of QSLs, match the observed chromospheric and
coronal structures (arch filament system, XBP and faint X-ray loops
(FXL)). We study also the evolution of the width of the QSL located
over the new negative polarity pore: the calculated QSL is very thin
(typically less than 100 m) during the lifetime of the XBP, but becomes
much thicker (≥ 104 m) after the XBP has faded. Furthermore
we show that peaks in X-ray brightness propagate along the FXL with a
velocity of ≈ 670 km s-1, starting from the XBP location,
implying that the energy is released where the emerging bipole impacts
against pre-existing coronal loops. We discuss the possible mechanism
of energy transport and conclude that the energy is conducted to the
remote footpoints of the FXL by a thermal front. These results strongly
support the supposition that the XBP brightness and flaring are due
to the interaction of different flux systems, through 3D magnetic
reconnection, at QSLs.
Title: Coordinated observations of solar activity phenomena. II. The
velocity field pattern in an elementary flare.
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.; Smaldone, L. A.
Bibcode: 1996A&A...306..625C
Altcode:
We present the line-of-sight velocity pattern determined from spectra
obtained before and during a small flare, whose emission properties have
been studied in Cauzzi et al. (1995, Paper I). The flare hard X-ray
(HXR) emission, in the range 25-100keV, consists of five separate
and short spikes (lasting 1-7s), which suggests that this flare
is a sequence of separate elementary bursts. 40 seconds before the
occurrence of any HXR emission the flare kernel is already bright in
Halpha_+1.5A and shows a typical chromospheric flare spectrum
with Balmer lines in emission up to H_13_. Also, few seconds before
the impulsive phase of the flare (as marked by the occurrence of the
first HXR spike) an upward motion is determined from lines originating
in high chromospheric layers (CaII K and Hdelta_) and from
metallic lines (Si I 3905, Fe I multiplets 4 and 5). These motions
together with a simultaneous strong emission suggest that the early
chromospheric modifications, which may be considered as signatures
of flare precursor, are due to some in situ mechanisms. 6 seconds
after the peak time of the first HXR spike we determine a downward
velocity, ranging from 1km/s for the metallic lines up to 20km/s for
Hdelta_ and CaII K lines, for all the points of the slit
intersecting the Halpha_+1.5A kernel. According to the known
dynamic flare models, the measured velocity can be explained either by
direct heating of the chromosphere from non-thermal electrons with a
low energy cutoff of 10keV, or by a thermal conduction front from the
hot corona. The downward velocity continues to increase (roughly by a
factor of 2) for 10s after the end of the first HXR spike; none of the
existing models predicts a similar behavior. After the fourth HXR spike
the direction of the velocity changes over the Halpha_+1.5 A
kernel and two small regions (=~3" in size), can be distinguished. In
the first one a downward velocity of about 15km/s is derived for
Hdelta_ and CaII K lines simultaneously to a velocity
=~1km/s from the metallic lines. In the second area, the velocities
derived from Hdelta_ and CaII K lines are upward directed,
with values up to -40km/s, while the velocity derived from the metallic
lines is still downward directed, with values =~1km/s. The sudden onset
of an upward motion could be related to the development of a surge
well visible after the flare; probably only the higher chromospheric
layers supply material to the surge.
Title: Asymmetries in solar active regions and flux emergence models
Authors: Cauzzi, G.; Moreno-Insertis, F.; van Driel-Gesztelyi, L.
Bibcode: 1996ASPC..109..121C
Altcode: 1996csss....9..121C
No abstract at ADS
Title: X-Ray Bright Point Flares Due to Magnetic Reconnection
Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein,
N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J.
Bibcode: 1996SoPh..163..145V
Altcode:
Ground-based optical observations coordinated with Yohkoh/SXT X-ray
observations of an old, disintegrating bipolar active region AR NOAA
7493 (May 1, 1993) provided a multiwavelength data base to study
a flaring `active region' X-ray bright point (XBP) of about 16 hr
lifetime, and the activity related to it in different layers of the
solar atmosphere. The XBP appeared to be related to a new minor bipole
of about 1020 Mx. Superposed on a global evolution of soft
X-ray brightness, the XBP displayed changes of brightness, lasting for
1-10 min. During the brightenings the XBP apparently had a spatial
structure, which was (tiny) loop-like rather than point-like. The
X-ray brightenings were correlated with chromospheric activity: (i)
brightenings of underlying chromospheric faculae, and (ii) appearance
of strong turbulent velocities in the arch filament system. We propose
that the XBP brightenings were due to reconnection of the magnetic
field lines (sketched in 3D) between the new bipole and a pre-existing
plage field induced by the motion of one of the new pores (v = 0.2
km s−1) towards the plage, and that the XBP itself was
a reconnected hot loop between them.
Title: Simultaneous Observation of Solar Surges in H alpha and X-ray
Authors: Akioka, M.; Cauzzi, G.
Bibcode: 1996mpsa.conf..451A
Altcode: 1996IAUCo.153..451A
No abstract at ADS
Title: Minor Photospheric and Chromospheric Magnetic Activity and
Related Coronal Signatures
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.; Hiei, E.; Smaldone,
L. A.
Bibcode: 1996mpsa.conf..433C
Altcode: 1996IAUCo.153..433C
No abstract at ADS
Title: A Search for Asymmetric Flows in Young Active Regions
Authors: Cauzzi, G.; Canfield, R. C.; Fisher, G. H.
Bibcode: 1996ApJ...456..850C
Altcode:
We have studied the temporal evolution of photospheric velocities
in young active regions that show evidence of ongoing magnetic
flux emergence. We searched for asymmetries in the vertical plasma
flows between the leading and following legs of the magnetic flux
tubes. Such asymmetries are predicted in models of flux tubes rising
in the convection zone (see the recent work of Fan, Fisher, &
DeLuca). These models, which successfully describe several aspects of
active region formation, predict plasma flows from the leading to the
following leg of a magnetic flux loop, driven by the Coriolis force
acting on the rising loop. These flows contribute to an excess of
gas pressure in the following leg with respect to the leading one. Our results show a predominance of downflow in the leading part of
three young regions with respect to the following part, contrary to
the model predictions. The observed asymmetries, obtained by averaging
over the totality of the magnetic structures, range from 60 to 150 m
s-1. Their real value, however, could be higher if the age
and effective magnetic filling factor were taken into account. The flow
asymmetry seems to disappear when the active regions enter a phase
of magnetic stability. We suggest two possible interpretations
of these results in terms of the dynamics of emerging magnetic flux
tubes as the most plausible ones. One possibility is that the rising
flux tube experiences severe fragmentation during the last stages of
emergence through the convection zone. After fragmentation, the greater
effect of aerodynamic drag strongly reduces the rise speed of the
smaller flux tubes and hence the Coriolis force that drives the flows
from the leading to the following leg of the magnetic loop. Since the
higher gas pressure present in the following leg is no longer balanced,
it will then drive a flow in the opposite direction, i.e., from the
following to the leading side. Estimates of these pressure-driven
flow velocities are consistent with the observed values. A second
possibility is that the asymmetric flows originate from a preexisting
superrotational velocity within high-field strength toroidal flux
rings near the base of the solar convection zone. As pointed out
in the recent work of Moreno-Insertis, Schussler, & Ferriz-Mas,
such superrotational velocities are required to maintain toroidal flux
rings in dynamical equilibrium.
Title: Emerging Flux, Reconnection, and XBP
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.;
Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein,
N.; Mein, P.
Bibcode: 1996mpsa.conf..459V
Altcode: 1996IAUCo.153..459V
No abstract at ADS
Title: Emerging flux seen by Yohkoh.
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.;
Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.;
Mein, N.; Mein, P.
Bibcode: 1996joso.proc..124V
Altcode:
No abstract at ADS
Title: Coordinated observations of solar activity
phenomena. I. Multispectral study of an elementary flare.
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.; Smaldone, L. A.;
Schwartz, R. A.; Hagyard, M.
Bibcode: 1995A&A...299..611C
Altcode:
In this paper we present a multispectral analysis of a small flare
which may be considered as a sequence of elementary bursts rather than a
collective flare phenomenon. A series of 5 short-lived (duration =~1-7s)
emission spikes are in fact observed in hard X-ray (HXR). The flare was
also observed in soft X-ray (SXR), with 3s temporal resolution, and in
the optical range with very high spatial (=~0.5") and temporal (2.7s)
resolutions. Sequences of filter images, in Halpha_ +1.5A,
He-D_3_ and Na-D_2_ wavelengths were acquired. The flare impulsive
phase, indicated by the occurrence of the HXR spikes, is preceded by
an enhancement in the chromospheric and in the coronal SXR emissions
starting, respectively, 40 and 15s before the flare. This indicates
that a density and/or a temperature increase in the flaring loop starts
at chromospheric levels, and only after this phase are the 5 separate
electron beams sequentially accelerated and stopped in an atmosphere
that is already modified. Four of the 5 HXR spikes are temporally
associated with chromospheric emission features over small areas of
3" size, while the fifth spike does not have detectable associated
signatures. Apparent contradictions between Halpha_ +
1.5 A and He-D_3_ emissions can be explained assuming atmospheric
inhomogeneities, already present within the flaring loop. The flare
occurs within an area of positive magnetic polarity, which shows a
moderate but constant weighted magnetic shear. No inclusions of the
opposite polarity are found in the flaring region, and no changes
in the distribution of any of the magnetic field parameters are
detected before, during and after the flare occurrence. No detectable
modifications are measured in the continuum and in all the wavelength
points of the Na-D_2_ line profile apart from the line core; this means
that flare-associated modifications of the flaring loop atmosphere do
not penetrate below the temperature minimum region.
Title: Dynamics of Small Flux Tubes
Authors: Reger, Bernard; Keil, Stephen L.; Smaldone, Luigi A.; Cauzzi,
Gianna; Balasubramaniam, K. S.
Bibcode: 1994ASPC...68..157R
Altcode: 1994sare.conf..157R
No abstract at ADS
Title: Observations of Active Region Dynamics: Preflare Flows and
Field Observations
Authors: Keil, Stephen L.; Balasubramaniam, K. S.; Bernasconi, Pietro;
Smaldone, Luigi A.; Cauzzi, Gianna
Bibcode: 1994ASPC...68..265K
Altcode: 1994sare.conf..265K
No abstract at ADS
Title: High temporal and spatial resolution observations of a solar
flare on June 7, 1991
Authors: Cauzzi, G.; Falchi, A.; Falciani, R.; Smaldone, L. A.
Bibcode: 1993AdSpR..13i.311C
Altcode: 1993AdSpR..13..311C
We present some preliminary results on a small flare observed at the
NSO-Sacramento Peak with very good spatial resolution (.6''-.7''). The
flare occurred on June, 7 1991 at ~ 13:43 UT in the NOAA region 6659
and has been observed by the COMPTON BATSE experiment in the 25-50 KeV
range. A very complex velocity pattern is found for chromospheric and
metallic lines: a small region (5'' wide) presents a strong blue-shifts
in all these lines, lasting through the flare, while, only in the Ca
II-K and Hδ lines, we find a zone (again ~ 5'' wide) of
strong red asymmetries contemporary to the hard X-rays spikes. These
observations show the importance of having high spatial and temporal
resolution measurements in the study of flares.
Title: On the calibration of line-of-sight magnetograms
Authors: Cauzzi, G.; Smaldone, L. A.; Balasubramaniam, K. S.; Keil,
S. L.
Bibcode: 1993SoPh..146..207C
Altcode:
Inference of magnetic fields from very high spatial, spectral, and
temporal resolution polarized images is critical in understanding the
physical processes that form and evolve fine scale structures in the
solar atmosphere. Studying high spectral resolution data also helps
in understanding the limits of lower resolution spectral data. We
compare three different methods for calibrating the line-of-sight
component of the magnetic field. Each method is tested for varying
degrees of spectral resolution on both synthetic line profiles computed
for known magnetic fields and real data. The methods evaluated are:
(a) the differences in the center of gravity of the right and left
circular components for different spectral resolution, (b) conversion
of circular polarization, at particular wavelengths, to magnetic
fields using model-dependent numerical solutions to the equations of
polarized radiative transfer, and (c) the derivative method using
the weak field approximation. Each method is applied to very high
spatial and spectral resolution circular polarization images of an
active region, acquired in the FeI 5250 å Zeeman-sensitive spectral
line. The images were obtained using the 20 må pass-band tunable
filter at NSO/Sacramento Peak Observatory Vacuum Tower Telescope. We
find that the center-of-gravity separation offers the best way of
inferring the longitudinal magnetic field.
Title: Observation of solar flares at high resolution.
Authors: Cauzzi, G.; Falciani, R.; Falchi, A.; Smaldone, L. A.
Bibcode: 1992ESASP.344..141C
Altcode: 1992spai.rept..141C
The authors present some preliminary results of the observation of
a flare performed at the NSO-Sacramento Peak with very good spatial
resolution. The flare occurred on June 7, 1991 at ≡13:43 UT in the
NOAA region 6659, showing an unusual high activity. A small region,
≡3″wide, shows strong blue shifts (of the order of the sound
speed) in some metallic lines formed in the high photosphere, during
the flare impulsive phase. These observations show the importance of
having measurements at higher spatial and temporal resolution for an
effective improvement of the knowledge of the fundamental dynamic of
active regions and flares.
Title: Two-dimensional solar spectroscopy with a Narrow Passband
Filter.
Authors: Cauzzi, G.
Bibcode: 1992lest.rept...19C
Altcode:
The performances of a Narrow Passband Filter recently installed at
NSO-SP are reviewed, in the framework of two-dimensional spectroscopy. A
panoramic of the data reduction procedures and elaboration, together
with samples of the physical parameters one can study, is given.
Title: Variation of the Vector Magnetic Field in an Eruptive Flare
Authors: Rust, D. M.; Cauzzi, G.
Bibcode: 1992LNP...399...46R
Altcode: 1992esf..coll...46R; 1992IAUCo.133...46R
Observations of a 3B, M6 flare on April 2, 1991 appear to confirm
earlier evidence that eruptive flares are triggered by measurable
magnetic field changes. In the eight hours before the flare, the
shear in the magnetic fields increased. The development that likely
triggered the flare was the emergence into the active region and rapid
proper motion of new flux. One of the small spots marking the negative
magnetic leg of the new flux pushed into an established positive field
at 0.2 km/s. Data from the JHU/APL vector magnetograph show that this
motion led to the development of a sheared field. The flare started
near the newly-sheared fields and spread to engulf most of the spot
region. A magnetogram taken 45 min after flare onset shows possible
relaxation of the sheared fields.
Title: Narrow Bandpass Filter Solar Observations
Authors: Smaldone, L. A.; Cauzzi, G.; Keil, S. L.
Bibcode: 1991BAAS...23.1057S
Altcode:
No abstract at ADS
Title: A New Method for Calibrating Vector Magnetograms
Authors: Cauzzi, G.; Rust, D. M.; O'Byrne, J. W.
Bibcode: 1991BAAS...23R1054C
Altcode:
No abstract at ADS
Title: Two-Dimensional High-Resolution Spectroscopy of Quiet Regions
on the Sun
Authors: Bonaccini, D.; Cauzzi, G.; Falchi, A.; Falciani, R.; Smaldone,
L. A.
Bibcode: 1990Ap&SS.170..117B
Altcode:
We present preliminary results of solar bi-dimensional spectroscopy
observations obtained with the new 20 mÅ NSO-Sacramento Peak tunable
filter. The procedures of image destretching and the corrections for
the modulation of the 5-min oscillations are briefly discussed.
Title: Bi-dimensional solar spectroscopy with the 20 mÅ filter:
capabilities and constraints.
Authors: Cauzzi, Gianna; Smaldone, Luigi A.
Bibcode: 1990SPIE.1318..193C
Altcode:
A new technique to perform bi-dimensional solar spectroscopy,
by means of a narrow passband filter, is examined. The technique,
combining high spatial and spectral resolution observations, allows
the determination of the dynamic and thermodynamic parameters of the
observed solar features, their spatial relationships and their evolution
properties. The authors discuss this technique, its observational
constraints and the data reduction procedures.
Title: Some remarks on the data analysis problems in solar
two-dimensional spectroscopy
Authors: Cauzzi, G.; Smaldone, L. A.; Bonaccini, D.; Falciani, R.
Bibcode: 1989hsrs.conf..261C
Altcode:
No abstract at ADS