Author name code: palacios
ADS astronomy entries on 2022-09-14
author:"Palacios, Judith"
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Title: Intermittency scaling laws in the fast solar wind and
magnetohydrodynamic turbulence simulations.
Authors: Palacios, J. C. C.; Perez, J. C.; Bourouaine, S.
Bibcode: 2020AGUFMSH0510006P
Altcode:
Turbulence is an irregular state characterized by the excitation
of fluid motions over a wide range of length-scales. Intermittency
is a process caused by the stochastic dissipation of the energy
cascade as it proceeds from large to small scales, developing
characteristically non-Gaussian statistics from the inertial
range to dissipation scales. The spatial structures generated by
this phenomenon, which has been observed in simulations as well as
observations in fluids and plasmas, influence dissipation, heating,
transport and acceleration of charged particles. In this work, the
structure and scaling properties of the statistical distribution of
field increments are investigated using solar wind observations and
numerical simulations of magnetohydrodynamic (MHD) turbulence. The
moments of these distributions, also known as structure functions,
satisfy universal power law scalings in the inertial range. However,
lack of ergodicity and finite sample size are the main complications
when calculating these functions, for both experimental data and results
from simulations, especially for high order structure functions where
rare events play a very important role. Our approach aims to overcome
these limitations by instead modeling the scale-dependent Probability
Distribution Functions (PDFs) of field increments of various turbulent
quantities and infer their scaling law properties from these PDFs. For
observations we used 23 years of data from the WIND spacecraft located
near 1 AU, carefully selected to represent periods of homogeneous and
incompressible turbulence in the fast solar wind. For simulations,
high resolution simulations of homogeneous RMHD (2048^3 grid points)
were analyzed. Results show very good agreement between observations and
simulations when comparing PDFs, allowing us to obtain better estimates
of the scaling exponents of structure functions for homogeneous and
incompressible turbulence in the fast solar wind.
Title: Magnetic Flux Emergence in a Coronal Hole
Authors: Palacios, Judith; Utz, Dominik; Hofmeister, Stefan; Krikova,
Kilian; Gömöry, Peter; Kuckein, Christoph; Denker, Carsten; Verma,
Meetu; González Manrique, Sergio Javier; Campos Rozo, Jose Iván;
Koza, Július; Temmer, Manuela; Veronig, Astrid; Diercke, Andrea;
Kontogiannis, Ioannis; Cid, Consuelo
Bibcode: 2020SoPh..295...64P
Altcode: 2020arXiv200611779P
A joint campaign of various space-borne and ground-based observatories,
comprising the Japanese Hinode mission (Hinode Observing Plan 338,
20 - 30 September 2017), the GREGOR solar telescope, and the Vacuum
Tower Telescope (VTT), investigated numerous targets such as pores,
sunspots, and coronal holes. In this study, we focus on the coronal
hole region target. On 24 September 2017, a very extended non-polar
coronal hole developed patches of flux emergence, which contributed
to the decrease of the overall area of the coronal hole. These flux
emergence patches erode the coronal hole and transform the area into a
more quiet-Sun-like area, whereby bipolar magnetic structures play an
important role. Conversely, flux cancellation leads to the reduction
of opposite-polarity magnetic fields and to an increase in the area
of the coronal hole.
Title: Dragonfly: In Situ Exploration of Titan's Organic Chemistry
and Habitability
Authors: Turtle, E. P.; Trainer, M. G.; Barnes, J. W.; Lorenz,
R. D.; Hibbard, K. E.; Adams, D. S.; Bedini, P. D.; Brinckerhoff,
W. B.; Burks, M. T.; Cable, M. L.; Ernst, C.; Freissinet, C.;
Hand, K.; Hayes, A. G.; Hörst, S. M.; Johnson, J. R.; Karkoschka,
E.; Langelaan, J. W.; Lawrence, D. J.; Le Gall, A.; Lora, J. M.;
MacKenzie, S. M.; McKay, C. P.; Miller, R. S.; Murchie, S.; Neish,
C. D.; Newman, C. E.; Núñez, J. I.; Palacios, J.; Panning, M. P.;
Parsons, A. M.; Peplowski, P. N.; Quick, L. C.; Radebaugh, J.; Rafkin,
S. C. R.; Ravine, M. A.; Schmitz, S.; Shiraishi, H.; Soderblom, J. M.;
Sotzen, K. S.; Stickle, A. M.; Stofan, E. R.; Szopa, C.; Tokano, T.;
Wilson, C.; Yingst, R. A.; Zacny, K.
Bibcode: 2020LPI....51.2288T
Altcode:
Dragonfly explores / Life's chemical origins / Titan's mysteries.
Title: Intermittency in inertial range MHD turbulence in simulations
and observations
Authors: Palacios, J. C.; Perez, J. C.; Bourouaine, S.
Bibcode: 2019AGUFMSH13E3458P
Altcode:
Intermittency plays a very important role in a number of turbulent
systems, including MHD turbulence. Understanding the statistical
properties of the fluctuating velocity, magnetic field and Elsasser
variables, can give us an important insight on the nature of the
turbulence and energy dissipation in plasmas. Estimation of high order
moments of fluctuations could help to discriminate between models of
turbulent cascades. However, this estimation is a very difficult task
because of lack of ergodicity and finite sample size. One approach
is trying to model the Probability Distribution Functions (PDF)
for fluctuations in plasmas at different scales. PDFs show that
the nature of these fluctuations is significantly non-Gaussian as
we go to smaller scales like inertial and dissipative range. Using
high resolution homogeneous RMHD simulations (2048^3 grid points)
and periods of homogeneous turbulence in the solar wind near 1AU from
1995 to 2017, we studied the intermittency of plasma turbulence and
the scaling laws governing the structure of high order statistics in
the inertial range by analyzing PDFs of increments on the fields.
Title: The Plasma β Evolution through the Solar Corona during Solar
Cycles 23 and 24
Authors: Rodríguez Gómez, Jenny Marcela; Palacios, Judith; Vieira,
Luis E. A.; Dal Lago, Alisson
Bibcode: 2019ApJ...884...88R
Altcode: 2019arXiv191000894R
The plasma β is important in the investigation of interchanging
roles of plasma and magnetic pressure in the solar atmosphere. It can
help to describe features over the photosphere and their changes at
different heights. The goal of this paper is to obtain the plasma
β variations through the solar corona during solar cycles 23 and
24. The plasma β is reconstructed in different layers of the solar
atmosphere. For this purpose, we use an updated version of the COronal
DEnsity and Temperature model. In this version we selected different
features in the solar atmosphere such as quiet-Sun (QS), faculae, and
active regions. We calculate the β variations at different layers in
the solar corona (R = 1.14, 1.19, 1.23, 1.28, 1.34, 1.40, 1.46, 1.53,
1.61, 1.74, 1.79, 1.84, and 1.90 R ⊙). In the photosphere
we use temperature values from the FALC model to obtain plasma β in
QS and faculae. Additionally, variations of the magnetic and kinetic
pressure were modeled during the last solar cycles at coronal heights.
Title: Dragonfly: In Situ Exploration of Titan's Organic Chemistry
and Habitability
Authors: Turtle, E. P.; Trainer, M. G.; Barnes, J. W.; Lorenz, R. D.;
Hibbard, K. E.; Adams, D. S.; Bedini, P.; Brinckerhoff, W. B.; Cable,
M. L.; Ernst, C.; Freissinet, C.; Hand, K.; Hayes, A. G.; Hörst,
S. M.; Johnson, J. R.; Karkoschka, E.; Langelaan, J. W.; Lawrence,
D. J.; Le Gall, A.; Lora, J. M.; MacKenzie, S. M.; McKay, C. P.;
Miller, R. S.; Murchie, S.; Neish, C. D.; Newman, C. E.; Palacios,
J.; Panning, M. P.; Parsons, A. M.; Peplowski, P. N.; Quick, L. C.;
Radebaugh, J.; Rafkin, S. C. R.; Ravine, M. A.; Schmitz, S.; Soderblom,
J. M.; Sotzen, K. S.; Stickle, A. M.; Stofan, E. R.; Szopa, C.;
Tokano, T.; Wilson, C.; Yingst, R. A.; Zacny, K.; Burks, M. T.
Bibcode: 2019LPI....50.2888T
Altcode:
Dragonfly explores / Life's chemical origins / Titan holds the clues.
Title: The consequences of erosion in modeling the shape of the CMEs
and its influence on the magnetosphere
Authors: Cid, Consuelo; Palacios, Judith; Saiz, Elena; Guerrero,
Antonio
Bibcode: 2018EGUGA..2018214C
Altcode:
On 2015 January 6 - 7 an interplanetary coronal mass ejection (ICME) was
observed at L1. A fast stream from a solar coronal hole was surrounding
this ICME. In this comunication we show that the stealth CME on January
3, while travelling away from the Sun embebed in this fast solar wind,
modifies its magnetic topology. Erosion, at least at the front boundary
of the ICME, produces a disappearance of a large part of the southern
component in the MC. This interaction not only results in a decrease
of the expected geoeffectiveness, but also in inaccurate estimations
of the flux rope axis when not considered in theoretical models.
Title: Magnetospheric response to extreme interplanetary magnetic
field transients
Authors: Cid, Consuelo; Guerrero, Antonio; Saiz, Elena; Palacios,
Judith; Cerrato, Yolanda
Bibcode: 2018EGUGA..2018465C
Altcode:
A statistical analysis of the solar wind parameters observed during
the ACE mission yields ten unique extreme B-field events throughout the
mission (1998-2018). In this work we analyze magnetospheric response to
these IP transients and the differences in their geoeffectiveness. Five
ground geomagnetic observatories at mid-latitude, widely spread in
longitude and with good data coverage are considered in the analysis
of the magnetic disturbances of these extreme events: San Pablo Toledo,
Surlary, Irkutsk, Memambetsu and Fresno observatories, whose IAGA codes
are SPT, SUA, IRT, MMB and FRN, respectively. The global and local
response components are distinguished, which nowadays has become a
turning point to advance towards a better geomagnetic storm forecasting.
Title: Solar wind parameter distributions and thresholds for extreme
values
Authors: Palacios, Judith; Cid, Consuelo; Guerrero, Antonio; Saiz,
Elena; Cerrato, Yolanda
Bibcode: 2018EGUGA..2019182P
Altcode:
A statistical analysis of the solar wind parameters observed during the
whole ACE mission duration, from 1998 to 2016, has been performed. These
high quality data taken by MAG/SWEPAM and SWICS comprise solar wind
parameters plus solar wind ion composition. The analysis includes
interplanetary magnetic field, proton temperature and density, solar
wind velocity and compositional anomalies. This communication shows
the most relevant results of the analyses, including the variety of
parameter distribution shapes, the goodness of distribution functions
for fitting the solar wind parameter distributions, the possibility
to establish thresholds for extreme values, and the dependence of the
data distributions with solar cycle.
Title: Dragonfly: In Situ Exploration of Titan's Organic Chemistry
and Habitability
Authors: Turtle, E. P.; Barnes, J. W.; Trainer, M. G.; Lorenz, R. D.;
Hibbard, K. E.; Adams, D. S.; Bedini, P.; Brinckerhoff, W. B.; Cable,
M. L.; Ernst, C.; Freissinet, C.; Hand, K.; Hayes, A. G.; Horst,
S. M.; Johnson, J. R.; Karkoschka, E.; Langelaan, J. W.; Lawrence,
D. J.; Le Gall, A.; Lora, J. M.; MacKenzie, S. M.; McKay, C. P.;
Neish, C. D.; Newman, C. E.; Palacios, J.; Panning, M. P.; Parsons,
A. M.; Peplowski, P. N.; Radebaugh, J.; Rafkin, S. C. R.; Ravine,
M. A.; Schmitz, S.; Soderblom, J. M.; Sotzen, K. S.; Stickle, A. M.;
Stofan, E. R.; Tokano, T.; Wilson, C.; Yingst, R. A.; Zacny, K.
Bibcode: 2018LPI....49.1641T
Altcode:
Titan quadcopter / Samples complex organics / How does life begin?
Title: Coronal Electron Density Temperature and Solar Spectral
Irradiance during Solar Cycles 23 and 24
Authors: Rodríguez Gómez, J. M.; Vieira, L.; Dal Lago, A.;
Palacios, J.
Bibcode: 2018ApJ...852..137R
Altcode: 2018arXiv180404089R
Plasma parameters such as the electron density and temperature play a
key role in the dynamics of the solar atmosphere. These characteristics
are important in solar physics because they can help us to understand
the physics of the solar corona, the ultimate goal being the
reconstruction of the electron density and temperature distributions in
the solar corona. The relations between emission and plasma parameters
in different timescales are studied. We present a physics-based model to
reconstruct the density, temperature, and emission in the EUV band. This
model, called COronal DEnsity and Temperature (CODET), is composed of
a flux transport model, an extrapolation model, an emission model, and
an optimization algorithm. The CODET model parameters were constrained
by comparing the model’s output to the TIMED/SEE record instead of
direct observations because it covers a longer time interval than the
direct solar observations currently available. The most important
results of the current work are the recovery of SSI variability in
specific wavelengths in the EUV band, as well as the variations in
density and temperature during large timescales through the solar
atmosphere with the CODET model. The evolution of the electron density
and temperature profiles through the solar corona in different layers
during solar cycles 23 and 24 will be presented. The emission maps were
obtained and they are in accordance with the observations. Additionally,
the density and temperature maps are related to the variations of the
magnetic field in different layers through the solar atmosphere.
Title: On the statistics of increments in strong Alfvenic turbulence
Authors: Palacios, J. C.; Perez, J. C.
Bibcode: 2017AGUFMSH33B2779P
Altcode:
In-situ measurements have shown that the solar wind is dominated
by non-compressive Alfvén-like fluctuations of plasma velocity
and magnetic field over a broad range of scales. In this work, we
present recent progress in understanding intermittency in Alfvenic
turbulence by investigating the statistics of Elsasser increments from
simulations of steadily driven Reduced MHD with numerical resolutions up
to 2048^3. The nature of these statistics guards a close relation to the
fundamental properties of small-scale structures in which the turbulence
is ultimately dissipated and therefore has profound implications in the
possible contribution of turbulence to the heating of the solar wind. We
extensively investigate the properties and three-dimensional structure
of probability density functions (PDFs) of increments and compare with
recent phenomenological models of intermittency in MHD turbulence.
Title: Modelling short-term Solar Spectral Irradiance (SSI) using
coronal electron density and temperature profiles based on solar
magnetic field observations
Authors: Gómez, J. M. Rodríguez; Vieira, L. E. Antunes; Lago,
A. Dal; Palacios, J.; Balmaceda, L. A.; Stekel, T.
Bibcode: 2017IAUS..327...82G
Altcode:
Some key physical processes that impact the evolution of Earth's
atmosphere on time-scale from days to millennia, such as the EUV
emissions, are determined by the solar magnetic field. However,
observations of the solar spectral irradiance are restricted to
the last few solar cycles and are subject to large uncertainties. We
present a physics-based model to reconstruct short-term solar spectral
irradiance (SSI) variability. The coronal magnetic field is estimated
to employ the Potential Field Source Surface extrapolation (PFSS)
based on observational synoptic charts and magnetic flux transport
model. The emission is estimated to employ the CHIANTI atomic database
8.0. The performance of the model is compared to the emission observed
by TIMED/SORCE.
Title: Storm and Substorm Causes and Effects at Midlatitude Location
for the St. Patrick's 2013 and 2015 Events
Authors: Guerrero, A.; Palacios, J.; Rodríguez-Bouza, M.;
Rodríguez-Bilbao, I.; Aran, A.; Cid, C.; Herraiz, M.; Saiz, E.;
Rodríguez-Caderot, G.; Cerrato, Y.
Bibcode: 2017JGRA..122.9994G
Altcode:
Midlatitude locations are unique regions exposed to both geomagnetic
storm and substorm effects, which may be superposed on specific events
imposing an extra handicap for the analysis and identification of the
sources and triggers. We study space weather effects at the midlatitude
location of the Iberian Peninsula for the St. Patrick's day events in
2013 and 2015. We have been able to identify and separate storm and
substorm effects on ground magnetometer data from San Pablo-Toledo
observatory during storm time revealing important contributions
of the Substorm Current Wedge on both events. The analysis of these
substorm local signatures have shown to be related to the production of
effective geomagnetically induced currents and ionospheric disturbances
as measured from Global Navigation Satellite Systems data at MAD2 IGS
permanent station and not directly related to the storm main phase. The
whole Sun-to-Earth chain has been analyzed in order to identify the
solar and interplanetary triggers. In both events a high-speed stream
(HSS) and a coronal mass ejections (CME) are involved, though for
2015 event, the HSS has merged with the CME, increasing the storm
geoeffectiveness. The enhancement of substorm geoeffectiveness is
justified by the effects of the inclined magnetic axes of the Sun and
of the Earth during equinox period.
Title: Photospheric magnetic field of an eroded-by-solar-wind coronal
mass ejection
Authors: Palacios, J.; Cid, C.; Saiz, E.; Guerrero, A.
Bibcode: 2017IAUS..327...67P
Altcode:
We have investigated the case of a coronal mass ejection that was
eroded by the fast wind of a coronal hole in the interplanetary
medium. When a solar ejection takes place close to a coronal hole,
the flux rope magnetic topology of the coronal mass ejection (CME)
may become misshapen at 1 AU as a result of the interaction. Detailed
analysis of this event reveals erosion of the interplanetary coronal
mass ejection (ICME) magnetic field. In this communication, we study
the photospheric magnetic roots of the coronal hole and the coronal
mass ejection area with HMI/SDO magnetograms to define their magnetic
characteristics.
Title: Modelling coronal electron density and temperature profiles
based on solar magnetic field observations
Authors: Rodríguez Gómez, J. M.; Antunes Vieira, L. E.; Dal Lago,
A.; Palacios, J.; Balmaceda, L. A.; Stekel, T.
Bibcode: 2017IAUS..328..159R
Altcode:
The density and temperature profiles in the solar corona are complex to
describe, the observational diagnostics is not easy. Here we present a
physics-based model to reconstruct the evolution of the electron density
and temperature in the solar corona based on the configuration of the
magnetic field imprinted on the solar surface. The structure of the
coronal magnetic field is estimated from Potential Field Source Surface
(PFSS) based on magnetic field from both observational synoptic charts
and a magnetic flux transport model. We use an emission model based on
the ionization equilibrium and coronal abundances from CHIANTI atomic
database 8.0. The preliminary results are discussed in details.
Title: Evolution of the Active Region NOAA 12443 based on magnetic
field extrapolations: preliminary results
Authors: Chicrala, André; Dallaqua, Renato Sergio; Antunes Vieira,
Luis Eduardo; Dal Lago, Alisson; Rodríguez Gómez, Jenny Marcela;
Palacios, Judith; Coelho Stekel, Tardelli Ronan; Rezende Costa,
Joaquim Eduardo; da Silva Rockenbach, Marlos
Bibcode: 2017IAUS..328..127C
Altcode:
The behavior of Active Regions (ARs) is directly related to the
occurrence of some remarkable phenomena in the Sun such as solar flares
or coronal mass ejections (CME). In this sense, changes in the magnetic
field of the region can be used to uncover other relevant features
like the evolution of the ARs magnetic structure and the plasma flow
related to it. In this work we describe the evolution of the magnetic
structure of the active region AR NOAA12443 observed from 2015/10/30
to 2015/11/10, which may be associated with several X-ray flares of
classes C and M. The analysis is based on observations of the solar
surface and atmosphere provided by HMI and AIA instruments on board
of the SDO spacecraft. In order to investigate the magnetic energy
buildup and release of the ARs, we shall employ potential and linear
force free extrapolations based on the solar surface magnetic field
distribution and the photospheric velocity fields.
Title: Magnetic instability of filaments in different solar regions
Authors: Palacios, J.; Guerrero, A.; Cid, C.; Saiz, E.; Cerrato, Y.
Bibcode: 2017IAUS..327...71P
Altcode:
Magnetic instability is a key consideration for filament eruptions
and subsequent CMEs. In this contribution we are considering different
magnetic conditions for active and non-active regions, such as coronal
hole regions and quiet sun, and also active regions of a simple magnetic
configuration. The aim is to assess magnetic instability through
potential and non-potential field modelling and 3D evaluation of the
magnetic decay index. Some eruptive examples from solar cycle 24 using
HMI/SDO data are presented, complemented with observations of AIA/SDO.
Title: Modelling coronal electron density and temperature profiles
of the Active Region NOAA 11855
Authors: Rodríguez Gómez, J. M.; Antunes Vieira, L. E.; Dal Lago,
A.; Palacios, J.; Balmaceda, L. A.; Stekel, T.
Bibcode: 2017IAUS..328..149R
Altcode:
The magnetic flux emergence can help understand the physical mechanism
responsible for solar atmospheric phenomena. Emerging magnetic flux is
frequently related to eruptive events, because when emerging they can
reconnected with the ambient field and release magnetic energy. We
will use a physic-based model to reconstruct the evolution of the
solar emission based on the configuration of the photospheric magnetic
field. The structure of the coronal magnetic field is estimated by
employing force-free extrapolation NLFFF based on vector magnetic field
products (SHARPS) observed by HMI instrument aboard SDO spacecraft from
Sept. 29 (2013) to Oct. 07 (2013). The coronal plasma temperature and
density are described and the emission is estimated using the CHIANTI
atomic database 8.0. The performance of the our model is compared to
the integrated emission from the AIA instrument aboard SDO spacecraft
in the specific wavelengths 171Å and 304Å.
Title: Multi-wavelength observations of vortex-like flows in the
photosphere using ground-based and space-borne telescopes
Authors: Palacios, J.; Vargas Domínguez, S.; Balmaceda, L. A.;
Cabello, I.; Domingo, V.
Bibcode: 2017arXiv170400660P
Altcode:
In this work we follow a series of papers on high-resolution
observations of small-scale structures in the solar atmosphere
\citep[][Cabello et al., in prep]{Balmaceda2009, Balmaceda2010,
Vargas2011, Palacios2012, Domingo2012, Vargas2015}, combining several
multi-wavelength data series. These were acquired by both ground-based
(SST) and space-borne (Hinode) instruments during the joint campaign of
the Hinode Operation Program 14, in September 2007. Diffraction-limited
SST data were taken in the G-band and G-cont, and were restored by
the MFBD technique. Hinode instruments, on the other hand, provided
multispectral data from SOT-FG in the CN band, and Mg~{\sc I} and
Ca {\sc II}~lines, as well as from SOT-SP in the Fe~{\sc I} line. In
this series of works we have thoroughly studied vortex flows and their
statistical occurrences, horizontal velocity fields by means of Local
Correlation Tracking (LCT), divergence and vorticity. Taking advantage
of the high-cadence and high spatial resolution data, we have also
studied bright point statistics and magnetic field intensification,
highlighting the importance of the smallest-scale magnetic element
observations.
Title: The Spanish Space Weather Service SeNMEs. A case study on
the Sun-Earth chain
Authors: Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato,
Y.; Rodríguez-Bouza, M.; Rodríguez-Bilbao, I.; Herraiz, M.;
Rodríguez-Caderot, G.
Bibcode: 2017arXiv170400684P
Altcode:
The Spanish Space Weather Service SeNMEs, \url{www.senmes.es}, is a
portal created by the SRG-SW of the Universidad de Alcalá, Spain,
to meet societal needs of near real-time space weather services. This
webpage-portal is divided in different sections to fulfill users needs
about space weather effects: radio blackouts, solar energetic particle
events, geomagnetic storms and presence of geomagnetically induced
currents. In less than one year of activity, this service has released
a daily report concerning the solar current status and interplanetary
medium, informing about the chances of a solar perturbation to hit the
Earth's environment. There are also two different forecasting tools for
geomagnetic storms, and a daily ionospheric map. These tools allow us
to nowcast a variety of solar eruptive events and forecast geomagnetic
storms and their recovery, including a new local geomagnetic index,
LDi{ñ}, along with some specific new scaling. In this paper we also
include a case study analysed by SeNMEs. Using different high resolution
and cadence data from space-borne solar telescopes SDO, SOHO and GOES,
along with ionospheric and geomagnetic data, we describe the Sun-Earth
feature chain for the event.
Title: Scaling-laws and high-order statistics in strong Alfvenic
turbulence
Authors: Palacios, J. C.; Perez, J. C.
Bibcode: 2016AGUFMSH41A2517P
Altcode:
The bulk of the fluctuation energy in the solar wind is observed to
be the form of incompressible fluctuations of the plasma velocity
and magnetic field, consistent with strong Alfvenic turbulence. Over
the last few decades, significant progress has been made in theory
and numerical simulations of Alfvenic turbulence allowing for direct
comparisons with solar wind observations. A large part of this progress
has been devoted to explain scaling laws in the power spectrum of
velocity and magnetic field fluctuations, turbulence anisotropy and
turbulent dissipation, which are inextricably related to the second
and third order statistics of the underlying turbulence. More recently
there has been increased interest in understanding high-order statistics
(or intermittency), at and beyond third order, due to its intimate
relation to the fundamental properties of small-scale structures in
which the turbulence is ultimately dissipated. Understanding the nature
of these small-scale structures generated by the turbulence has profound
implications in a number of practical applications, such as turbulent
heating in the solar wind and cosmic-ray acceleration. In this work we
present an extensive analysis of scaling-laws governing the structure
of high-order statistics in steady-state strong Alfven turbulence from
high-resolution numerical simulations. High Reynolds number numerical
simulations with up to 2048^3 grid points are used to construct three
dimensional probability distribution functions, using over one-billion
samples per distribution, allowing for measurements of structure
functions and scaling law exponents with unprecedented accuracy. The
results are discussed in the context of recent models and simulations
of anisotropy and intermittency as well as solar wind observations. We
will also discuss the limits and uncertainties associated with the
estimation of high-order moments from a finite-number of samples,
which are unavoidable in numerical simulations.
Title: Redefining the Boundaries of Interplanetary Coronal Mass
Ejections from Observations at the Ecliptic Plane
Authors: Cid, C.; Palacios, J.; Saiz, E.; Guerrero, A.
Bibcode: 2016ApJ...828...11C
Altcode: 2016arXiv160901140C
On 2015 January 6-7, an interplanetary coronal mass ejection (ICME) was
observed at L1. This event, which can be associated with a weak and slow
coronal mass ejection, allows us to discuss the differences between the
boundaries of the magnetic cloud and the compositional boundaries. A
fast stream from a solar coronal hole surrounding this ICME offers
a unique opportunity to check the boundaries’ process definition
and to explain differences between them. Using Wind and ACE data, we
perform a complementary analysis involving compositional, magnetic,
and kinematic observations providing relevant information regarding
the evolution of the ICME as travelling away from the Sun. We propose
erosion, at least at the front boundary of the ICME, as the main reason
for the difference between the boundaries, and compositional signatures
as the most precise diagnostic tool for the boundaries of ICMEs.
Title: Multi-wavelength Observations of Photospheric Vortex Flows
in the Photosphere Using Ground-based and Space-borne Telescopes
Authors: Palacios, J.; Vargas Domínguez, S.; Balmaceda, L. A.;
Cabello, I.; Domingo, V.
Bibcode: 2016ASPC..504..139P
Altcode:
In this work we follow a series of papers on high-resolution
observations of small-scale structures in the solar atmosphere
(Balmaceda et al. 2009, 2010; Vargas Domínguez et al. 2011; Palacios et
al. 2012; Domingo et al. 2012; Vargas Domínguez et al. 2015, Cabello et
al., in prep), combining several multi-wavelength data series. These
were acquired by both ground-based (SST) and space-borne (Hinode)
instruments during the joint campaign of the Hinode Operation Program
14, in September 2007. Diffraction-limited SST data were taken in the
G-band and G-cont, and were restored by the MFBD technique. Hinode
instruments, on the other hand, provided multispectral data from SOT-FG
in the CN band, and Mg I and Ca II lines, as well as from SOT-SP in
the Fe I line. In this series of works we have thoroughly studied
vortex flows and their statistical occurrences, horizontal velocity
fields by means of Local Correlation Tracking (LCT), divergence and
vorticity. Taking advantage of the high-cadence and high spatial
resolution data, we have also studied bright point statistics and
magnetic field intensification, highlighting the importance of the
smallest-scale magnetic element observations.
Title: The Spanish Space Weather Service SeNMEs. A Case Study on
the Sun-Earth Chain
Authors: Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato,
Y.; Rodríguez-Bouza, M.; Rodríguez-Bilbao, I.; Herraiz, M.;
Rodríguez-Caderot, G.
Bibcode: 2016ASPC..504..131P
Altcode:
The Spanish Space Weather Service SeNMEs, www.senmes.es, is a
portal created by the SRG-SW of the Universidad de Alcalá, Spain,
to meet societal needs of near real-time space weather services. This
webpage-portal is divided in different sections to fulfill users needs
about space weather effects: radio blackouts, solar energetic particle
events, geomagnetic storms and presence of geomagnetically induced
currents. In less than one year of activity, this service has released
a daily report concerning the solar current status and interplanetary
medium, informing about the chances of a solar perturbation to hit the
Earth's environment. There are also two different forecasting tools for
geomagnetic storms, and a daily ionospheric map. These tools allow us
to nowcast a variety of solar eruptive events and forecast geomagnetic
storms and their recovery, including a new local geomagnetic index,
LDiñ, along with some specific new scaling. In this paper we also
include a case study analysed by SeNMEs. Using different high resolution
and cadence data from space-borne solar telescopes SDO, SOHO and GOES,
along with ionospheric and geomagnetic data, we describe the Sun-Earth
feature chain for the event.
Title: Influence of a plasma swirl motion on fine magnetic
concentrations in the solar photosphere
Authors: Palacios, Judith; Balmaceda, Laura; Cabello, Iballa; Domingo,
Vicente
Bibcode: 2016Tecci..11....1P
Altcode:
High-resolution observations from ground-based (Solar Swedish Telescope)
and space-borne (Hinode) solar telescopes acquired data with various
filters, obtaining images of a quiet Sun region populated with
small-scale magnetic elements. The region is also characterized by the
presence of photospheric swirl convective plasma structures. This work
abridges the results of different analyses applied over time series of
images to follow the evolution of magnetic features aiming to establish
the influence of the plasma vortices on their motions.
Title: Searching for Carrington-like events and their signatures
and triggers
Authors: Saiz, Elena; Guerrero, Antonio; Cid, Consuelo; Palacios,
Judith; Cerrato, Yolanda
Bibcode: 2016JSWSC...6A...6S
Altcode: 2016arXiv160105711S
The Carrington storm in 1859 is considered to be the major geomagnetic
disturbance related to solar activity. In a recent paper, Cid
et al. (2015) discovered a geomagnetic disturbance case with a
profile extraordinarily similar to the disturbance of the Carrington
event at Colaba, but at a mid-latitude observatory, leading to a
reinterpretation of the 1859 event. Based on those results, this paper
performs a deep search for other "Carrington-like" events and analyses
interplanetary observations leading to the ground disturbances which
emerged from the systematic analysis. The results of this study based
on two Carrington-like events (1) reinforce the awareness about the
possibility of missing hazardous space weather events as the large
H-spike recorded at Colaba by using global geomagnetic indices, (2)
argue against the role of the ring current as the major current involved
in Carrington-like events, leaving field-aligned currents (FACs) as
the main current involved and (3) propose abrupt southward reversals of
IMF along with high solar wind pressure as the interplanetary trigger
of a Carrington-like event.
Title: Design review of the Brazilian Experimental Solar Telescope
Authors: Dal Lago, A.; Vieira, L. E. A.; Albuquerque, B.; Castilho,
B.; Guarnieri, F. L.; Cardoso, F. R.; Guerrero, G.; Rodríguez, J. M.;
Santos, J.; Costa, J. E. R.; Palacios, J.; da Silva, L.; Alves, L. R.;
Costa, L. L.; Sampaio, M.; Dias Silveira, M. V.; Domingues, M. O.;
Rockenbach, M.; Aquino, M. C. O.; Soares, M. C. R.; Barbosa, M. J.;
Mendes, O., Jr.; Jauer, P. R.; Branco, R.; Dallaqua, R.; Stekel,
T. R. C.; Pinto, T. S. N.; Menconi, V. E.; Souza, V. M. C. E. S.;
Gonzalez, W.; Rigozo, N.
Bibcode: 2015AGUFMSH13D2462D
Altcode:
The Brazilian's National Institute for Space Research (INPE),
in collaboration with the Engineering School of Lorena/University
of São Paulo (EEL/USP), the Federal University of Minas Gerais
(UFMG), and the Brazilian's National Laboratory for Astrophysics
(LNA), is developing a solar vector magnetograph and visible-light
imager to study solar processes through observations of the solar
surface magnetic field. The Brazilian Experimental Solar Telescope
is designed to obtain full disk magnetic field and line-of-sight
velocity observations in the photosphere. Here we discuss the system
requirements and the first design review of the instrument. The
instrument is composed by a Ritchey-Chrétien telescope with a 500 mm
aperture and 4000 mm focal length. LCD polarization modulators will be
employed for the polarization analysis and a tuning Fabry-Perot filter
for the wavelength scanning near the Fe II 630.25 nm line. Two large
field-of-view, high-resolution 5.5 megapixel sCMOS cameras will be
employed as sensors. Additionally, we describe the project management
and system engineering approaches employed in this project. As the
magnetic field anchored at the solar surface produces most of the
structures and energetic events in the upper solar atmosphere and
significantly influences the heliosphere, the development of this
instrument plays an important role in advancing scientific knowledge in
this field. In particular, the Brazilian's Space Weather program will
benefit most from the development of this technology. We expect that
this project will be the starting point to establish a strong research
program on Solar Physics in Brazil. Our main aim is to progressively
acquire the know-how to build state-of-art solar vector magnetograph
and visible-light imagers for space-based platforms.
Title: Supergranular-scale magnetic flux emergence beneath an
unstable filament
Authors: Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato, Y.
Bibcode: 2015A&A...583A..47P
Altcode: 2015arXiv150905602P
Aims: Here we report evidence of a large solar filament eruption
on 2013, September 29. This smooth eruption, which passed without
any previous flare, formed after a two-ribbon flare and a coronal
mass ejection towards Earth. The coronal mass ejection generated
a moderate geomagnetic storm on 2013, October 2 with very serious
localized effects. The whole event passed unnoticed to flare-warning
systems.
Methods: We have conducted multi-wavelength analyses
of the Solar Dynamics Observatory through Atmospheric Imaging Assembly
(AIA) and Helioseismic and Magnetic Imager (HMI) data. The AIA data
on 304, 193, 211, and 94 Å sample the transition region and the
corona, respectively, while HMI provides photospheric magnetograms,
continuum, and linear polarization data, in addition to the fully
inverted data provided by HMI.
Results: This flux emergence
happened very close to a filament barb that was very active in
mass motion, as seen in 304 Å images. The observed flux emergence
exhibited hectogauss values. The flux emergence extent appeared just
beneath the filament, and the filament rose during the following
hours. The emergence acquired a size of 33'' in ~12 h, about ~0.16
km s-1. The rate of signed magnetic flux is around 2 ×
1017 Mx min-1 for each polarity. We have also
studied the eruption speed, size, and dynamics. The mean velocity
of the rising filament during the ~40 min previous to the flare is
115 ± 5 km s-1, and the subsequent acceleration in this
period is 0.049 ± 0.001 km s-2.
Conclusions: We have
observed a supergranular-sized emergence close to a large filament in
the boundary of the active region NOAA11850. Filament dynamics and
magnetogram results suggest that the magnetic flux emergence takes
place in the photospheric level below the filament. Reconnection
occurs underneath the filament between the dipped lines that support
the filament and the supergranular emergence. The very smooth ascent
is probably caused by this emergence and torus instability may play
a fundamental role, which is helped by the emergence. Movies
associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org
Title: Flux emergence event underneath a filament
Authors: Palacios, J.; Cerrato, Y.; Cid, C.; Guerrero, A.; Saiz, E.
Bibcode: 2015IAUS..305...79P
Altcode: 2017arXiv170400681P
Flux emergence phenomena are relevant at different temporal and
spatial scales. We have studied a flux emergence region underneath a
filament. This filament elevated itself smoothly, and the associated
CME reached the Earth. In this study we investigate the size and the
amount of flux in the emergence event. The flux emergence site appeared
just beneath a filament. The emergence acquired a size of 24 Mm in
half a day. The unsigned magnetic flux density from LOS-magnetograms
was around 1 kG at its maximum. The transverse field as well as the
filament eruption were also analysed.
Title: Preliminary design of the INPE's Solar Vector Magnetograph
Authors: Vieira, L. E. A.; de Gonzalez, A. L. Clúa; Lago, A. Dal;
Wrasse, C.; Echer, E.; Guarnieri, F. L.; Cardoso, F. Reis; Guerrero,
G.; Costa, J. Rezende; Palacios, J.; Balmaceda, L.; Alves, L. Ribeiro;
da Silva, L.; Costa, L. L.; Sampaio, M.; Soares, M. C. Rabello;
Barbosa, M.; Domingues, M.; Rigozo, N.; Mendes, O.; Jauer, P.;
Dallaqua, R.; Branco, R. H.; Stekel, T.; Gonzalez, W.; Kabata, W.
Bibcode: 2015IAUS..305..195V
Altcode: 2016arXiv160900995V
We describe the preliminary design of a magnetograph and visible-light
imager instrument to study the solar dynamo processes through
observations of the solar surface magnetic field distribution. The
instrument will provide measurements of the vector magnetic field and
of the line-of-sight velocity in the solar photosphere. As the magnetic
field anchored at the solar surface produces most of the structures
and energetic events in the upper solar atmosphere and significantly
influences the heliosphere, the development of this instrument plays an
important role in reaching the scientific goals of The Atmospheric and
Space Science Coordination (CEA) at the Brazilian National Institute
for Space Research (INPE). In particular, the CEA's space weather
program will benefit most from the development of this technology. We
expect that this project will be the starting point to establish a
strong research program on Solar Physics in Brazil. Our main aim is
acquiring progressively the know-how to build state-of-the-art solar
vector magnetograph and visible-light imagers for space-based platforms
to contribute to the efforts of the solar-terrestrial physics community
to address the main unanswered questions on how our nearby Star works.
Title: Magnetic field configuration in a flaring active region
Authors: Palacios, J.; Balmaceda, L. A.; Vieira, L. E.
Bibcode: 2015IAUS..305...97P
Altcode:
The Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics
Observatory (SDO) provides continuous monitoring of the Sun's vector
magnetic field through full-disk photospheric data with both high
cadence and high spatial resolution. Here we investigate the evolution
of AR 11249 from March 6 to March 7, 2012. We make use of HMI Stokes
imaging, SDO/SHARPs, the HMI magnetic field line-of-sight (LOS) maps and
the transverse components of the magnetic field as well as LOS velocity
maps in order to detect regions with significant flux emergence and/or
cancellation. In addition, we apply the Local Correlation Tracking (LCT)
technique to the total and signed magnetic flux data and derive maps
of horizontal velocity. From this analysis, we were able to pinpoint
localized shear regions (and a shear channel) where penumbrae and pore
formation areas, with strong linear polarization signals, are stretched
and squeezed, showing also important downflows and upflows. We have
also utilized Hinode/SP data and compared them to the HMI-SHARPs and
the HMI-Stokes spectrograms. The aforementioned shear channel seems to
correspond well with the X-class flare main channel of March 7 2012,
as observed in AIA/SDO 171, 304 and 1600 Å.
Title: A Carrington-like geomagnetic storm observed in the 21st
century
Authors: Cid, Consuelo; Saiz, Elena; Guerrero, Antonio; Palacios,
Judith; Cerrato, Yolanda
Bibcode: 2015JSWSC...5A..16C
Altcode: 2015arXiv150507028C
In September 1859 the Colaba observatory measured the most extreme
geomagnetic disturbance ever recorded at low latitudes related
to solar activity: the Carrington storm. This paper describes a
geomagnetic disturbance case with a profile extraordinarily similar
to the disturbance of the Carrington event at Colaba: the event on 29
October 2003 at Tihany magnetic observatory in Hungary. The analysis of
the H-field at different locations during the "Carrington-like" event
leads to a re-interpretation of the 1859 event. The major conclusions of
the paper are the following: (a) the global Dst or SYM-H, as indices
based on averaging, missed the largest geomagnetic disturbance in
the 29 October 2003 event and might have missed the 1859 disturbance,
since the large spike in the horizontal component (H) of terrestrial
magnetic field depends strongly on magnetic local time (MLT); (b)
the main cause of the large drop in H recorded at Colaba during the
Carrington storm was not the ring current but field-aligned currents
(FACs); and (c) the very local signatures of the H-spike imply that
a Carrington-like event can occur more often than expected.
Title: Evolution of Small-Scale Magnetic Elements in the Vicinity
of Granular-Sized Swirl Convective Motions
Authors: Vargas Domínguez, S.; Palacios, J.; Balmaceda, L.; Cabello,
I.; Domingo, V.
Bibcode: 2015SoPh..290..301V
Altcode: 2014SoPh..tmp..187V; 2014arXiv1405.2380V
Advances in solar instrumentation have led to widespread use of time
series to study the dynamics of solar features, especially at small
spatial scales and at very fast cadences. Physical processes at such
scales are important as building blocks for many other processes
occurring from the lower to the upper layers of the solar atmosphere
and beyond, ultimately for understanding the larger picture of solar
activity. Ground-based (Swedish Solar Telescope) and space-borne
(Hinode) high-resolution solar data are analyzed in a quiet-Sun region
that displays negative-polarity small-scale magnetic concentrations
and a cluster of bright points observed in G-band. The region is
characterized by two granular-sized convective vortex-type plasma
motions, one of which appears to be affecting the dynamics of magnetic
features and bright points in its vicinity and is therefore the main
target of our investigations. We followed the evolution of the bright
points, intensity variations at different atmospheric height, and
the magnetic evolution for a set of interesting selected regions. We
describe the evolution of the photospheric plasma motions in the region
near the convective vortex and some plausible cases for convective
collapse detected in Stokes profiles.
Title: On extreme geomagnetic storms
Authors: Cid, Consuelo; Palacios, Judith; Saiz, Elena; Guerrero,
Antonio; Cerrato, Yolanda
Bibcode: 2014JSWSC...4A..28C
Altcode:
Extreme geomagnetic storms are considered as one of the major natural
hazards for technology-dependent society. Geomagnetic field disturbances
can disrupt the operation of critical infrastructures relying on
space-based assets, and can also result in terrestrial effects, such
as the Quebec electrical disruption in 1989. Forecasting potential
hazards is a matter of high priority, but considering large flares
as the only criterion for early-warning systems has demonstrated
to release a large amount of false alarms and misses. Moreover, the
quantification of the severity of the geomagnetic disturbance at the
terrestrial surface using indices as Dst cannot be considered as the
best approach to give account of the damage in utilities. High temporal
resolution local indices come out as a possible solution to this issue,
as disturbances recorded at the terrestrial surface differ largely
both in latitude and longitude. The recovery phase of extreme storms
presents also some peculiar features which make it different from other
less intense storms. This paper goes through all these issues related
to extreme storms by analysing a few events, highlighting the March
1989 storm, related to the Quebec blackout, and the October 2003 event,
when several transformers burnt out in South Africa.
Title: Featuring dark coronal structures: physical signatures of
filaments and coronal holes for automated recognition
Authors: Palacios, Judith; Cid, Consuelo; Saiz, Elena; Cerrato,
Yolanda; Guerrero, Antonio
Bibcode: 2014IAUS..300..517P
Altcode: 2017arXiv170400692P
Filaments may be mistaken for coronal holes when observed in extreme
ultraviolet (EUV) images; however, a closer and more careful look
reveals that their photometric properties are different. The combination
of EUV images with photospheric magnetograms shows some characteristic
differences between filaments and coronal holes. We have performed
analyses with 7 different SDO/AIA wavelengths (94, 131, 171, 211, 193,
304, 335 Å) and SDO/HMI magnetograms obtained in September 2011 and
March 2012 to study coronal holes and filaments from the photometric,
magnetic, and also geometric point of view, since projection effects
play an important role on the aforementioned traits.
Title: Collisional Interactions of Low Temperature Ice Milliparticles
with Spacecraft at Speeds Up To 120 m/s
Authors: Gold, R. E.; Iyer, K.; Struk, P.; Palacios, J.; Lynch, C.;
Vargas, M.; Spisz, T.; Kreeger, E.
Bibcode: 2013AGUFM.P41E1964G
Altcode:
There is scant data on collisions between spacecraft and small ice
particles at low (<100K) temperatures and impact speeds of order
100 m/s. These conditions are believed to characterize potential space
missions to comets, icy moons, and ring systems. This collisional
phenomenology is relevant to fly-by capture and return of samples from
planetary targets, and landing on icy surfaces. Previous efforts in the
area of ice particle impact response have addressed ~3 mm diameter ice
spheres near the elastic/inelastic transition speed, ~10 m/s (Higa et
al, 1998). The present work describes development of specially designed
experiments to enable imaging of the fragmentation behavior of 3 mm
diameter (nominal) ice spheres at significantly greater impact speeds
(~20 - 120 m/s) and normal (0°) and glancing (30°, 45° and 60°)
impacts for the first time. The imaging of the high speed impacts was
achieved through precise synchronization of an ice particle dispenser,
a rotating polished aluminum alloy impact surface representing the
spacecraft, and a high-speed camera. Individual video frames reveal
the motion of both the larger impact fragments as well as the average
motion of the clouds of small fragments that are generated by the
spacecraft-ice impacts. This new experimental capability can be used
to help design future planetary missions to icy bodies. Ice particle
impacts at 120 m/s with surface at 60 degree angle.
Title: Modeling the recovery phase of extreme geomagnetic storms
Authors: Cid, C.; Palacios, J.; Saiz, E.; Cerrato, Y.; Aguado, J.;
Guerrero, A.
Bibcode: 2013JGRA..118.4352C
Altcode: 2014arXiv1405.4804C
recovery phase of the largest storms ever recorded has been
studied. These events provide an extraordinary opportunity for two
goals: (1) to validate the hyperbolic model by Aguado et al. (<link
href="#jgra50409-bib-0001"/>) for the recovery phase after
disturbances as severe as the Carrington event or that related to
the Hydro-Quebec blackout in March 1989, and (2) to check whether
the linear relationship between the recovery time and the intensity
of the storm still complies. Our results reveal the high accuracy of
the hyperbolic decay function to reproduce the recovery phase of the
magnetosphere after an extreme storm. Moreover, the characteristic time
that takes the magnetosphere to recover depends in an exponential way
on the intensity of the storm, as indicated by the relationship between
the two parameters involved in the hyperbolic decay. This exponential
function can be approached by a linear function when the severity of
the storm diminishes.
Title: Solar sources of the geoeffective events in September 2011
Authors: Palacios, J.; Guerrero, A.; Cid, C.; Saiz, E.; Cerrato, Y.
Bibcode: 2013hsa7.conf..792P
Altcode: 2014arXiv1401.1721P
We investigate the geoeffective events happened from 8 to 20 Sept
2011, analysing the most plausible solar sources of these events,
where coronal mass ejections and coronal holes play a fundamental
role. The physical properties of the coronal holes, such as area and
magnetic field, are studied through the Solar Dynamics Observatory
instruments: AIA 193 Å images and HMI longitudinal magnetograms. The
active regions which are the origin of the coronal mass ejections are
analysed on AIA and SoHO-LASCO data.
Title: Magnetic evolution of faculae observed with IMaX
Authors: Blanco, J.; Palacios, J.; Cabello, I.; Domingo, V.;
Sunrise Team
Bibcode: 2013hsa7.conf..803B
Altcode:
The SUNRISE mission, consisting of a one metre diameter telescope on
board a stratospheric balloon, was launched on June 2009 on route over
the artic circle. At approximately 36 km height, the balloon flight
allowed to observe with almost no atmospheric influence yielding
very good quality data as well as observations in ultraviolet
spectral lines (by means of the SUFI instrument). The mission's
artic summer-circumpolar flight path provided continuous solar
observations, without day-night cycles, during the almost 5 days of
the mission. IMaX/SUNRISE instrument --developed by a consortium of
Spanish institutions-- is a spectropolarimeter based in the use of a
Fabry-Pérot etalon and liquid crystals for spectral and polarimetric
analysis, respectively. It obtained full-Stokes vector maps at the
selected wavelength of Fe I 5250.2 Å with a temporal cadence of
around 30 seconds and a spatial resolution of approximately 0.15--0.18
arcsec. In this poster, we present a temporal series of a group of limb
faculae comprising approximately 21 minutes. Thanks to the data quality,
as well as the full-Stokes maps and fast temporal cadence, small-scale
magnetic cancellations and emergences can be observed around and at
the faculae positions. We focused on a small area of the instrument
field of view where the cancellation magnetogram shows high magnetic
polarity changes. What we observe are confronted patches of opposite
polarities from the longitudinal magnetic field, being cancelled
and reappearing, while the transversal field signal present changes
also accordingly. This reflects as well in the continuum intensity
images where facular brightenings are seen enhancing and decreasing
in consonance with the transversal field evolution. Studies of this
cancellation phenomena and evolution of the facular structures as
magnetic tubes are being performed for more thorough analyses.
Title: Study of the interplanetary and solar structures of two
geoeffective events in September 2011
Authors: Guerrero, A.; Palacios, J.; Saiz, E.; Cid, C.; Cerrato, Y.
Bibcode: 2013hsa7.conf..807G
Altcode:
From the 8th to the 20th of September, 2011 two Coronal Mass Ejections
(CMEs) reached the Earth causing two moderate geomagnetic storms
(Dst<-50 nT). The scenario would be simple except for the presence
of a Coronal Hole (CH) which generates a High Speed Stream (HSS)
situated between the trajectory of the two CMEs. In this study, we
analyze possible interactions between different structures and their
geoeffectiveness, connecting the observed in interplanetary medium
(in-situ and remote) with the observed on earth. Data from ACE and
WIND spacecraft for the interplanetary medium transients are used,
as well as data from STEREO, SOHO, PROBA2 and SDO missions for the
solar sources of the events.
Title: Revising the triggers of the 31 March 2001 geomagnetic storm
Authors: Cid, Consuelo; Richardson, Ian; Palacios, Judith; Tsurutani,
Bruce; Echer, Ezequiel; Cerrato, Yolanda; Gonzalez, Walter D.; Saiz,
Elena; Zhukov, Andrei; Guerrero, Antonio; Lopez, Ramon; Clua de
Gonzalez, Alicia L.; Vasyliünas, Vytenis
Bibcode: 2013EGUGA..1512446C
Altcode:
The 31 March 2001 geomagnetic storm has been extensively analyzed in
literature both, from the magnetospheric point of view and from the
solar triggers and their solar wind counterparts. However, there is not
an agreement among different studies on the solar activity related to
the event. In this presentation we go deeper in the already existing
analyses of solar wind data, which are the link between magnetospheric
response and solar activity in order to discover the true solar triggers
of the event.
Title: Structure of Small Magnetic Elements in the Solar Atmosphere
Authors: Domingo, V.; Palacios, J.; Balmaceda, L. A.; Domínguez,
S. V.; Cabello, I.
Bibcode: 2012ASPC..454...69D
Altcode: 2012arXiv1209.0978D
High resolution images at different wavelengths, spectrograms and
magnetograms, representing different levels of the solar atmosphere
obtained with Hinode have been combined to study the 3-dimensional
structure of the small magnetic elements in relation to their
radiance. A small magnetic element is described as example of the study.
Title: Observations of Vortex Motion in the Solar Photosphere Using
Hinode-SP Data
Authors: Palacios, J.; Balmaceda, L. A.; Domínguez, S. V.; Cabello,
I.; Domingo, V.
Bibcode: 2012ASPC..454...51P
Altcode: 2012arXiv1209.0190P
In this work, we focus in the magnetic evolution of a small
region as seen by Hinode-SP during the time interval of about one
hour. High-cadence LOS magnetograms and velocity maps were derived,
allowing the study of different small-scale processes such as the
formation/dissappearance of bright points accompanying the evolution
of an observed convective vortical motion.
Title: First Results from the SUNRISE Mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller,
T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González,
M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta,
J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González,
N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt,
W.; Steiner, O.; Title, A. M.
Bibcode: 2012ASPC..455..143S
Altcode:
The SUNRISE balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that reveal the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the SUNRISE data, which include a number of discoveries.
Title: Solar and interplanetary triggers of the largest Dst variations
of the solar cycle 23
Authors: Cerrato, Y.; Saiz, E.; Cid, C.; Gonzalez, W. D.; Palacios, J.
Bibcode: 2012JASTP..80..111C
Altcode:
We present the results of an investigation from the Sun to the Earth of
the sequence of events that caused major Dst decreases (ΔDst≤-100 nT
during 1 h) that occurred during 1996-2005. These events are expected to
be better related to geomagnetic induced current (GIC) events than those
events where any geomagnetic index is far from its quiet time value. At
least one full halo CME with a speed on the plane of sky above 900 km/s
participates in every studied event. The seven events were triggered by
interplanetary signatures, which arise as a consequence of interaction
among different solar ejections. The interaction arises at different
stages from the solar surface, between segments of a filament, to the
interplanetary medium, appearing as ejecta or multiple-magnetic clouds
(MultiMCs). In other cases, shock waves overtake or compress previous
ICMEs and at other times the interaction also appears between magnetic
clouds (MCs) and streams.
Title: Geoeffectiveness of two CMEs interacting with the same CH
Authors: Guerrero, A.; Cid, C.; Cerrato, Y.; Saiz, E.; Palacios, J.;
Seaton, D.
Bibcode: 2012EGUGA..14.9720G
Altcode:
From 8th to 20th September, 2011 two Coronal Mass Ejections (CMEs)
reached the Earth causing two moderate geomagnetic storms (Dst <
-50 nT). The sources of the CMEs were two different active regions
(AR) separated by a Coronal Hole (CH) (the first one coming from the
western AR and the second one from the eastern AR). The interplanetary
counterparts of the CMEs and the fast stream from the CH interacted in
their way out. At Lagrangian point L1, two ICMEs appear influenced by
the leading and trailing boundaries of the High Speed Stream. We study
the event all the way from the Sun to the Earth, looking for features
that could have enhanced the geoeffectiveness of the ICMEs. Data from
ACE and WIND spacecraft for the interplanetary medium transients are
used, as well as data from STEREO, SOHO, PROBA2 and SDO missions for
the solar sources of the events.
Title: Magnetic field emergence in mesogranular-sized exploding
granules observed with sunrise/IMaX data
Authors: Palacios, J.; Blanco Rodríguez, J.; Vargas Domínguez, S.;
Domingo, V.; Martínez Pillet, V.; Bonet, J. A.; Bellot Rubio, L. R.;
Del Toro Iniesta, J. C.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Berkefeld, T.; Schmidt, W.; Knölker, M.
Bibcode: 2012A&A...537A..21P
Altcode: 2011arXiv1110.4555P
We report on magnetic field emergences covering significant
areas of exploding granules. The balloon-borne mission Sunrise
provided high spatial and temporal resolution images of the solar
photosphere. Continuum images, longitudinal and transverse magnetic
field maps and Dopplergrams obtained by IMaX onboard Sunrise are
analyzed by local correlation traking (LCT), divergence calculation
and time slices, Stokes inversions and numerical simulations are also
employed. We characterize two mesogranular-scale exploding granules
where ~1018 Mx of magnetic flux emerges. The emergence
of weak unipolar longitudinal fields (~100 G) start with a single
visible magnetic polarity, occupying their respective granules' top
and following the granular splitting. After a while, mixed polarities
start appearing, concentrated in downflow lanes. The events last around
20 min. LCT analyses confirm mesogranular scale expansion, displaying
a similar pattern for all the physical properties, and divergence
centers match between all of them. We found a similar behaviour
with the emergence events in a numerical MHD simulation. Granule
expansion velocities are around 1 kms-1 while magnetic
patches expand at 0.65 kms-1. One of the analyzed events
evidences the emergence of a loop-like structure. Advection of
the emerging magnetic flux features is dominated by convective
motion resulting from the exploding granule due to the magnetic
field frozen in the granular plasma. Intensification of the
magnetic field occurs in the intergranular lanes, probably
because of being directed by the downflowing plasma. Movies
associated to Figs. 2-4 are available in electronic form at http://www.aanda.org
Title: Spatial distribution and statistical properties of small-scale
convective vortex-like motions in a quiet-Sun region
Authors: Vargas Domínguez, S.; Palacios, J.; Balmaceda, L.; Cabello,
I.; Domingo, V.
Bibcode: 2011MNRAS.416..148V
Altcode: 2011MNRAS.tmp.1046V; 2011arXiv1105.3092V
High-resolution observations of a quiet-Sun internetwork region taken
with the Solar 1-m Swedish Telescope in La Palma are analysed. We
determine the location of small-scale vortex motions in the solar
photospheric region by computing the horizontal proper motions
of small-scale structures on time-series of images. These plasma
convectively driven swirl motions are associated to (1) downdrafts
(that have been commonly explained as corresponding to sites where
the plasma is cooled down and hence returned to the interior below
the visible photospheric level) and (2) horizontal velocity vectors
converging on a central point. The sink cores are proved to be the final
destination of passive floats tracing plasma flows towards the centre
of each vortex. We establish the occurrence of these events to be 1.4
× 10-3 and 1.6 × 10-3 vortices Mm-2
min-1, respectively, for the two time-series analysed here.
Title: The Sun at high resolution: first results from the Sunrise
mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller,
A.; Gandorfer, A.; Hirzberger, J.; Lagg, A.; Riethmüller, T. L.;
Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; Pillet, V. Martínez;
Khomenko, E.; del Toro Iniesta, J. C.; Domingo, V.; Palacios, J.;
Knölker, M.; González, N. Bello; Borrero, J. M.; Berkefeld, T.;
Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M.
Bibcode: 2011IAUS..273..226S
Altcode:
The Sunrise balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system and further infrastructure. The first
science flight of Sunrise yielded high-quality data that reveal the
structure, dynamics and evolution of solar convection, oscillations
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the Sunrise data, which include a number of discoveries.
Title: SUNRISE: Instrument, Mission, Data, and First Results
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Riethmüller, T. L.; Schüssler, M.;
Bonet, J. A.; Martínez Pillet, V.; del Toro Iniesta, J. C.; Domingo,
V.; Palacios, J.; Knölker, M.; Bello González, N.; Berkefeld, T.;
Franz, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.127S
Altcode: 2010arXiv1008.3460S
The SUNRISE balloon-borne solar observatory consists of a 1 m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that revealed the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. After a brief description of instruments and data, the first
qualitative results are presented. In contrast to earlier observations,
we clearly see granulation at 214 nm. Images in Ca II H display narrow,
short-lived dark intergranular lanes between the bright edges of
granules. The very small-scale, mixed-polarity internetwork fields
are found to be highly dynamic. A significant increase in detectable
magnetic flux is found after phase-diversity-related reconstruction
of polarization maps, indicating that the polarities are mixed right
down to the spatial resolution limit and probably beyond.
Title: SUNRISE/IMaX Observations of Convectively Driven Vortex Flows
in the Sun
Authors: Bonet, J. A.; Márquez, I.; Sánchez Almeida, J.; Palacios,
J.; Martínez Pillet, V.; Solanki, S. K.; del Toro Iniesta, J. C.;
Domingo, V.; Berkefeld, T.; Schmidt, W.; Gandorfer, A.; Barthol, P.;
Knölker, M.
Bibcode: 2010ApJ...723L.139B
Altcode: 2010arXiv1009.1992B
We characterize the observational properties of the convectively driven
vortex flows recently discovered on the quiet Sun, using magnetograms,
Dopplergrams, and images obtained with the 1 m balloon-borne SUNRISE
telescope. By visual inspection of time series, we find some 3.1
× 10-3 vortices Mm-2 minute-1,
which is a factor of ~1.7 larger than previous estimates. The mean
duration of the individual events turns out to be 7.9 minutes, with
a standard deviation of 3.2 minutes. In addition, we find several
events appearing at the same locations along the duration of the time
series (31.6 minutes). Such recurrent vortices show up in the proper
motion flow field map averaged over the time series. The typical
vertical vorticities are lsim6 × 10-3 s-1,
which corresponds to a period of rotation of some 35 minutes. The
vortices show a preferred counterclockwise sense of rotation, which
we conjecture may have to do with the preferred vorticity impinged by
the solar differential rotation.
Title: Evidence of small-scale magnetic concentrations dragged by
vortex motion of solar photospheric plasma
Authors: Balmaceda, L.; Vargas Domínguez, S.; Palacios, J.; Cabello,
I.; Domingo, V.
Bibcode: 2010A&A...513L...6B
Altcode: 2010arXiv1004.1185B
Vortex-type motions have been measured by tracking bright points in
high-resolution observations of the solar photosphere. These small-scale
motions are thought to be determinant in the evolution of magnetic
footpoints and their interaction with plasma and therefore likely to
play a role in heating the upper solar atmosphere by twisting magnetic
flux tubes. We report the observation of magnetic concentrations being
dragged towards the center of a convective vortex motion in the solar
photosphere from high-resolution ground-based and space-borne data. We
describe this event by analyzing a series of images at different solar
atmospheric layers. By computing horizontal proper motions, we detect a
vortex whose center appears to be the draining point for the magnetic
concentrations detected in magnetograms and well-correlated with the
locations of bright points seen in G-band and CN images.
Title: Observations of Magnetic Elements in the Quiet Sun Internetwork
Authors: Balmaceda, L. A.; Palacios, J.; Cabello, I.; Domingo, V.
Bibcode: 2009ASPC..415..156B
Altcode:
We present here the analysis of high-resolution images of the quiet Sun
at disk center taken with the Solar Optical Telescope (SOT) on board
Hinode in the CN bandhead (388.35 nm) and magnetograms in the Mg I line
(517.27 nm). These observations are complemented with data from the
Swedish 1m Solar Telescope (SST). All data sets were obtained during
the Hinode/Canary Islands joint campaign (HOP 0014) in September,
2007. In particular, we investigate the morphology, radiative and
magnetic properties of small-scale elements in the solar atmosphere.
Title: Small magnetic structures in the photosphere, radiative
properties
Authors: Palacios, Judith; Domingo, Vicente; Cabello, Iballa; Bonet,
José Antonio; Sánchez Almeida, Jorge
Bibcode: 2008cosp...37.2331P
Altcode: 2008cosp.meet.2331P
The three dimensional structure of small magnetic field features in the
photosphere, their dynamic behavior and their radiative properties are
studied. We analyze data obtained in simultaneous observations made on
Sept 29 and 30, 2007 with the HINODE spacecraft and the Swedish Solar
Telescope (SST) in La Palma in different wavelengths, such as CaII
(396.85 nm) and CN (388.35 nm) and other with Hinode data; and Gband
(430.56 nm) with SST. Tha analysis is completed with high resolution
Gband and Gcontinuum (436.39 nm) images from SST obtained on 2005 and
2006. Magnetograms have been obtained from both observatories. SST
images have been processed with MOMFB code. Ribbon-like structures and
"flowers" are studied in detail. Comparisons with solar atmospheric
models are presented.
Title: Study of multi-muon bundles in cosmic ray showers detected
with the DELPHI detector at LEP
Authors: Delphi Collaboration; Abreu, P.; Adam, W.; Adzic, P.;
Albrecht, T.; Alemany-Fernandez, R.; Allmendinger, T.; Allport,
P. P.; Amaldi, U.; Amapane, N.; Amato, S.; Anashkin, E.; Andreazza,
A.; Andringa, S.; Anjos, N.; Antilogus, P.; Apel, W. -D.; Arnoud,
Y.; Ask, S.; Asman, B.; Augustinus, A.; Baillon, P.; Ballestrero, A.;
Bambade, P.; Barbier, R.; Bardin, D.; Barker, G. J.; Baroncelli, A.;
Battaglia, M.; Baubillier, M.; Becks, K. -H.; Begalli, M.; Behrmann,
A.; Ben-Haim, E.; Benekos, N.; Benvenuti, A.; Berat, C.; Berggren,
M.; Bertrand, D.; Besancon, M.; Besson, N.; Bloch, D.; Blom, M.;
Bluj, M.; Bonesini, M.; Boonekamp, M.; Booth, P. S. L.; Borisov,
G.; Botner, O.; Bouquet, B.; Bowcock, T. J. V.; Boyko, I.; Bracko,
M.; Brenner, R.; Brodet, E.; Bruckman, P.; Brunet, J. M.; Buschbeck,
B.; Buschmann, P.; Calvi, M.; Camporesi, T.; Canale, V.; Carena, F.;
Castro, N.; Cavallo, F.; Chapkin, M.; Charpentier, Ph.; Checchia, P.;
Chierici, R.; Chliapnikov, P.; Chudoba, J.; Chung, S. U.; Cieslik,
K.; Collins, P.; Contri, R.; Cosme, G.; Cossutti, F.; Costa, M. J.;
Crennell, D.; Cuevas, J.; D'Hondt, J.; da Silva, T.; da Silva, W.;
Della Ricca, G.; de Angelis, A.; de Boer, W.; de Clercq, C.; de Lotto,
B.; de Maria, N.; de Min, A.; de Paula, L.; di Ciaccio, L.; di Simone,
A.; Doroba, K.; Drees, J.; Eigen, G.; Ekelof, T.; Ellert, M.; Elsing,
M.; Espirito Santo, M. C.; Fanourakis, G.; Fassouliotis, D.; Feindt,
M.; Fernandez, J.; Ferrer, A.; Ferro, F.; Flagmeyer, U.; Foeth, H.;
Fokitis, E.; Fulda-Quenzer, F.; Fuster, J.; Gandelman, M.; Garcia,
C.; Gavillet, Ph.; Gazis, E.; Gokieli, R.; Golob, B.; Gomez-Ceballos,
G.; Goncalves, P.; Graziani, E.; Grosdidier, G.; Grzelak, K.; Guy, J.;
Haag, C.; Hallgren, A.; Hamacher, K.; Hamilton, K.; Haug, S.; Hauler,
F.; Hedberg, V.; Hennecke, M.; Herr, H.; Hoffman, J.; Holmgren, S. -O.;
Holt, P. J.; Houlden, M. A.; Jackson, J. N.; Jarlskog, G.; Jarry,
P.; Jeans, D.; Johansson, E. K.; Jonsson, P.; Joram, C.; Jungermann,
L.; Kapusta, F.; Katsanevas, S.; Katsoufis, E.; Kernel, G.; Kersevan,
B. P.; Kerzel, U.; King, B. T.; Kjaer, N. J.; Kluit, P.; Kokkinias, P.;
Kourkoumelis, C.; Kouznetsov, O.; Krumstein, Z.; Kucharczyk, M.; Lamsa,
J.; Leder, G.; Ledroit, F.; Leinonen, L.; Leitner, R.; Lemonne, J.;
Lepeltier, V.; Lesiak, T.; Liebig, W.; Liko, D.; Lipniacka, A.; Lopes,
J. H.; Lopez, J. M.; Loukas, D.; Lutz, P.; Lyons, L.; MacNaughton, J.;
Malek, A.; Maltezos, S.; Mandl, F.; Marco, J.; Marco, R.; Marechal, B.;
Margoni, M.; Marin, J. -C.; Mariotti, C.; Markou, A.; Martinez-Rivero,
C.; Masik, J.; Mastroyiannopoulos, N.; Matorras, F.; Matteuzzi, C.;
Mazzucato, F.; Mazzucato, M.; McNulty, R.; Meroni, C.; Migliore, E.;
Mitaroff, W.; Mjoernmark, U.; Moa, T.; Moch, M.; Moenig, K.; Monge,
R.; Montenegro, J.; Moraes, D.; Moreno, S.; Morettini, P.; Mueller,
U.; Muenich, K.; Mulders, M.; Mundim, L.; Murray, W.; Muryn, B.;
Myatt, G.; Myklebust, T.; Nassiakou, M.; Navarria, F.; Nawrocki,
K.; Nicolaidou, R.; Nikolenko, M.; Oblakowska-Mucha, A.; Obraztsov,
V.; Olshevski, A.; Onofre, A.; Orava, R.; Osterberg, K.; Ouraou, A.;
Oyanguren, A.; Paganoni, M.; Paiano, S.; Palacios, J. P.; Palka, H.;
Papadopoulou, Th. D.; Pape, L.; Parkes, C.; Parodi, F.; Parzefall, U.;
Passeri, A.; Passon, O.; Peralta, L.; Perepelitsa, V.; Perrotta, A.;
Petrolini, A.; Piedra, J.; Pieri, L.; Pierre, F.; Pimenta, M.; Piotto,
E.; Podobnik, T.; Poireau, V.; Pol, M. E.; Polok, G.; Pozdniakov, V.;
Pukhaeva, N.; Pullia, A.; Rames, J.; Read, A.; Rebecchi, P.; Rehn, J.;
Reid, D.; Reinhardt, R.; Renton, P.; Richard, F.; Ridky, J.; Rivero,
M.; Rodriguez, D.; Romero, A.; Ronchese, P.; Roudeau, P.; Rovelli,
T.; Ruhlmann-Kleider, V.; Ryabtchikov, D.; Sadovsky, A.; Salmi, L.;
Salt, J.; Sander, C.; Savoy-Navarro, A.; Schwickerath, U.; Sekulin,
R.; Shellard, R. C.; Siebel, M.; Sisakian, A.; Smadja, G.; Smirnova,
O.; Sokolov, A.; Sopczak, A.; Sosnowski, R.; Spassov, T.; Stanitzki,
M.; Stocchi, A.; Strauss, J.; Stugu, B.; Szczekowski, M.; Szeptycka,
M.; Szumlak, T.; Tabarelli, T.; Taffard, A. C.; Tegenfeldt, F.;
Timmermans, J.; Tkatchev, L.; Tobin, M.; Todorovova, S.; Tome, B.;
Tonazzo, A.; Tortosa, P.; Travnicek, P.; Treille, D.; Tristram, G.;
Trochimczuk, M.; Troncon, C.; Turluer, M. -L.; Tyapkin, I. A.; Tyapkin,
P.; Tzamarias, S.; Uvarov, V.; Valenti, G.; van Dam, P.; van Eldik, J.;
van Remortel, N.; van Vulpen, I.; Vegni, G.; Veloso, F.; Venus, W.;
Verdier, P.; Verzi, V.; Vilanova, D.; Vitale, L.; Vrba, V.; Wahlen,
H.; Washbrook, A. J.; Weiser, C.; Wicke, D.; Wickens, J.; Wilkinson,
G.; Winter, M.; Witek, M.; Yushchenko, O.; Zalewska, A.; Zalewski, P.;
Zavrtanik, D.; Zhuravlov, V.; Zimin, N. I.; Zintchenko, A.; Zupan, M.
Bibcode: 2007APh....28..273D
Altcode: 2007arXiv0706.2561T
The DELPHI detector at LEP has been used to measure multi-muon
bundles originating from cosmic ray interactions with air. The cosmic
events were recorded in “parasitic mode” between individual
e+e- interactions and the total live time of
this data taking is equivalent to 1.6 × 106 s. The DELPHI
apparatus is located about 100 m underground and the 84 metres rock
overburden imposes a cutoff of about 52 GeV/c on muon momenta. The data
from the large volume Hadron Calorimeter allowed the muon multiplicity
of 54,201 events to be reconstructed. The resulting muon multiplicity
distribution is compared with the prediction of the Monte Carlo
simulation based on CORSIKA/QGSJET01. The model fails to describe the
abundance of high multiplicity events. The impact of QGSJET internal
parameters on the results is also studied.
Title: Dynamics of the circumstellar gas in the Herbig Ae stars BF
Orionis, SV Cephei, WW Vulpeculae and XY Persei
Authors: Mora, A.; Eiroa, C.; Natta, A.; Grady, C. A.; de Winter, D.;
Davies, J. K.; Ferlet, R.; Harris, A. W.; Miranda, L. F.; Montesinos,
B.; Oudmaijer, R. D.; Palacios, J.; Quirrenbach, A.; Rauer, H.;
Alberdi, A.; Collier Cameron, A.; Deeg, H. J.; Garzón, F.; Horne,
K.; Merín, B.; Penny, A.; Schneider, J.; Solano, E.; Tsapras, Y.;
Wesselius, P. R.
Bibcode: 2004A&A...419..225M
Altcode: 2004astro.ph..2614M
We present high resolution (λ/Δ λ = 49 000) échelle spectra of the
intermediate mass, pre-main sequence stars BF Ori,
SV Cep, WW Wul and XY
Per. The spectra cover the range 3800-5900 Å and monitor
the stars on time scales of months and days. All spectra show a
large number of Balmer and metallic lines with variable blueshifted
and redshifted absorption features superimposed to the photospheric
stellar spectra. Synthetic Kurucz models are used to estimate rotational
velocities, effective temperatures and gravities of the stars. The
best photospheric models are subtracted from each observed spectrum to
determine the variable absorption features due to the circumstellar
gas; those features are characterized in terms of their velocity, v,
dispersion velocity, Δ v, and residual absorption, Rmax. The
absorption components detected in each spectrum can be grouped by
their similar radial velocities and are interpreted as the signature
of the dynamical evolution of gaseous clumps with, in most cases,
solar-like chemical composition. This infalling and outflowing gas
has similar properties to the circumstellar gas observed in UX Ori,
emphasizing the need for detailed theoretical models, probably in
the framework of the magnetospheric accretion scenario, to understand
the complex environment in Herbig Ae (HAe) stars. WW Vul is unusual
because, in addition to infalling and outflowing gas with properties
similar to those observed in the other stars, it shows also transient
absorption features in metallic lines with no obvious counterparts in
the hydrogen lines. This could, in principle, suggest the presence of
CS gas clouds with enhanced metallicity around WW Vul. The existence
of such a metal-rich gas component, however, needs to be confirmed
by further observations and a more quantitative analysis. Tables
\ref{master_table_bfori}-\ref{master_table_xyper} are only available
in electronic form at http://www.edpsciences.org
Title: Study of the properties and spectral energy distributions of
the Herbig AeBe stars HD 34282 and HD 141569
Authors: Merín, B.; Montesinos, B.; Eiroa, C.; Solano, E.; Mora, A.;
D'Alessio, P.; Calvet, N.; Oudmaijer, R. D.; de Winter, D.; Davies,
J. K.; Harris, A. W.; Collier Cameron, A.; Deeg, H. J.; Ferlet, R.;
Garzón, F.; Grady, C. A.; Horne, K.; Miranda, L. F.; Palacios, J.;
Penny, A.; Quirrenbach, A.; Rauer, H.; Schneider, J.; Wesselius, P. R.
Bibcode: 2004A&A...419..301M
Altcode: 2004astro.ph..2599M
We present a study of the stellar parameters, distances and
spectral energy distributions (SEDs) of HD 34282
and HD 141569, two pre-main sequence Herbig AeBe
stars. Both objects have been reported to show ``anomalous positions''
in the HR diagram in the sense that they appear below the main
sequence. A significant result of this work is that both stars are
metal-deficient. The Hipparcos distance of HD 34282 is very uncertain
and the current study places the star at the expected evolutionary
position in the HR diagram, i.e. as a PMS star. The distance for HD
141569 found in this work matches the Hipparcos distance, and the
problem of its anomalous position is solved as a result of the low
metallicity of the object: using the right metallicity tracks, the
star is in the PMS region. The SEDs are constructed using data covering
ultraviolet to millimetre wavelengths. Physical, non-parametric models,
have been applied in order to extract some properties of the disks
surrounding the stars. The disk around HD 34282 is accreting actively,
it is massive and presents large grains in the mid-plane and small
grains in the surface. HD 141569 has a very low mass disk, which is
in an intermediate stage towards a debris-type disk. Based on
observations made with the CST, NOT, INT and WHT telescopes of the
Canary Islands observatories under the auspices of its International
Time Programme. Also based on observations made with the 2.2 m telescope
at Calar Alto Observatory (Almería).
Title: Physical parameters for the EXPORT sample. Rotational
velocities and effective temperatures
Authors: Solano, E.; Montesinos, B.; Mora, A.; Alberdi, A.;
Collier-Cameron, A.; Davies, J. K.; Deeg, H. J.; Eiroa, C.; Ferlet, R.;
Garzón, F.; Grady, C. A.; Harris, A.; Horne, K.; Merín, B.; Miranda,
L. F.; Oudmaijer, R.; Palacios, J.; Penny, A.; Quirrenbach, A.; Rauer,
H.; Schneider, J.; Tsapras, Y.; Wesselius, P. R.; de Winter, D.
Bibcode: 2004IAUS..202..127S
Altcode:
No abstract at ADS
Title: Properties of the EXPORT sample: Spectral type determination
Authors: Merín, Bruno; Montesinos, Benjamín; Alberdi, A.;
Collier-Cameron, A.; Davies, J. K.; Deeg, H. J.; Eiroa, C.; Ferlet, R.;
Garzón, F.; Grady, C. A.; Harris, A.; Horne, K.; Miranda, L. F.; Mora,
A.; Oudmaijer, R.; Palacios, J.; Penny, A.; Quirenbach, A.; Rauer, H.;
Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.; de Winter, D.
Bibcode: 2004IAUS..202...87M
Altcode:
No abstract at ADS
Title: A dynamical study of the circumstellar gas in UX Orionis
Authors: Mora, A.; Natta, A.; Eiroa, C.; Grady, C. A.; de Winter, D.;
Davies, J. K.; Ferlet, R.; Harris, A. W.; Montesinos, B.; Oudmaijer,
R. D.; Palacios, J.; Quirrenbach, A.; Rauer, H.; Alberdi, A.; Collier
Cameron, A.; Deeg, H. J.; Garzón, F.; Horne, K.; Merín, B.; Penny,
A.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.
Bibcode: 2002A&A...393..259M
Altcode: 2002astro.ph..8322M
We present the results of a high spectral resolution (lambda /
Delta lambda = 49 000) study of the circumstellar (CS) gas around the
intermediate mass, pre-main sequence star UX Ori. The
results are based on a set of 10 échelle spectra covering the
spectral range 3800-5900 Å, monitoring the star on time scales of
months, days and hours. A large number of transient blueshifted and
redshifted absorption features are detected in the Balmer and in many
metallic lines. A multigaussian fit is applied to determine for each
transient absorption the velocity, v, dispersion velocity, Delta v, and
the parameter R, which provides a measure of the absorption strength
of the CS gas. The time evolution of those parameters is presented
and discussed. A comparison of intensity ratios among the transient
absorptions suggests a solar-like composition of the CS gas. This
confirms previous results and excludes a very metal-rich environment
as the cause of the transient features in UX Ori. The features can
be grouped by their similar velocities into 24 groups, of which 17
are redshifted and 7 blueshifted. An analysis of the velocity of
the groups allows us to identify them as signatures of the dynamical
evolution of 7 clumps of gas, of which 4 represent accretion events and
3 outflow events. Most of the events decelerate at a rate of tenths
of m s-2, while 2 events accelerate at approximately the
same rate; one event is seen experiencing both an acceleration and a
deceleration phase and lasts for a period of few days. This time scale
seems to be the typical duration of outflowing and infalling events in
UX Ori. The dispersion velocity and the relative aborption strength
of the features do not show drastic changes during the lifetime of
the events, which suggests they are gaseous blobs preserving their
geometrical and physical identity. These data are a very useful tool
for constraining and validating theoretical models of the chemical
and physical conditions of CS gas around young stars; in particular,
we suggest that the simultaneous presence of infalling and outflowing
gas should be investigated in the context of detailed magnetospheric
accretion models, similar to those proposed for the lower mass T
Tauri stars.
Title: On the simultaneous optical and near-infrared variability of
pre-main sequence stars
Authors: Eiroa, C.; Oudmaijer, R. D.; Davies, J. K.; de Winter, D.;
Garzón, F.; Palacios, J.; Alberdi, A.; Ferlet, R.; Grady, C. A.;
Collier Cameron, A.; Deeg, H. J.; Harris, A. W.; Horne, K.; Merín,
B.; Miranda, L. F.; Montesinos, B.; Mora, A.; Penny, A.; Quirrenbach,
A.; Rauer, H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.
Bibcode: 2002A&A...384.1038E
Altcode:
For a complete understanding of the physical processes causing the
photometric variability of pre-main sequence systems, simultaneous
optical and near-IR observations are required to disentangle the
emission from the stars and that from their associated circumstellar
disks. Data of this sort are extremely rare and little systematic
work has been reported to date. The work presented in this paper
is a systematic attempt in this direction. It presents an analysis
of the simultaneous optical and near-IR photometric variability of
18 Herbig Ae/Be and T Tauri stars which were observed in October 98
by the EXPORT collaboration. The time difference between the UBVRI
and JHK measurements is less than 1 hour in ~50% of the data and the
largest difference is around 2 hours in only ~10% of the data. Twelve
stars appear to show a correlation between the optical and near-IR
variability trends, which suggests a common physical origin such as
spots and/or variable extinction. The optical and near-IR variability is
uncorrelated in the rest of the objects, which suggests it originates
in distinctly different regions. In general, the optical variability
qualitatively follows the predictions of starspots or variable
extinction. As far as the near-IR is concerned, the simultaneity
of the observations demonstrates that for most objects the flux is
largely produced by their circumstellar disks and, consequently, in
many cases the near-IR fluctuations must be attributed to structural
variations of such disks producing variations of their thermal emission
and/or scattered light. The observed near-IR changes of up to around
1 mag on timescales of 1-2 days provide interesting challenges for
understanding the mechanisms generating such remarkable variabilities,
an issue insufficiently investigated until now but one which deserves
further theoretical and modeling efforts.
Title: EXPORT: Optical photometry and polarimetry of Vega-type and
pre-main sequence stars
Authors: Oudmaijer, R. D.; Palacios, J.; Eiroa, C.; Davies, J. K.; de
Winter, D.; Ferlet, R.; Garzón, F.; Grady, C. A.; Collier Cameron,
A.; Deeg, H. J.; Harris, A. W.; Horne, K.; Merín, B.; Miranda,
L. F.; Montesinos, B.; Mora, A.; Penny, A.; Quirrenbach, A.; Rauer,
H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.
Bibcode: 2001A&A...379..564O
Altcode: 2001astro.ph.10641O
This paper presents optical UBVRI broadband photo-polarimetry
of the EXPORT sample obtained at the 2.5 m Nordic Optical
Telescope. The database consists of multi-epoch photo-polarimetry
of 68 pre-main-sequence and main-sequence stars. An investigation of
the polarization variability indicates that 22 objects are variable
at the 3sigma level in our data. All these objects are pre-main
sequence stars, consisting of both T Tauri and Herbig Ae/Be objects
while the main sequence, Vega type and post-T Tauri type objects are
not variable. The polarization properties of the variable sources
are mostly indicative of the UXOR-type behaviour; the objects show
highest polarization when the brightness is at minimum. We add seven
new objects to the class of UXOR variables (BH Cep, VX Cas, DK Tau,
HK Ori, LkHα 234, KK Oph and RY Ori). The main reason for their
discovery is the fact that our data-set is the largest in its kind,
indicating that many more young UXOR-type pre-main sequence stars
remain to be discovered. The set of Vega-like systems has been
investigated for the presence of intrinsic polarization. As they
lack variability, this was done using indirect methods, and apart
from the known case of BD+31o643, the following stars
were found to be strong candidates to exhibit polarization due to
the presence of circumstellar disks: 51 Oph, BD+31o643C,
HD 58647 and HD 233517. Table A1 is only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/379/564
Title: EXPORT: Spectral classification and projected rotational
velocities of Vega-type and pre-main sequence stars
Authors: Mora, A.; Merín, B.; Solano, E.; Montesinos, B.; de Winter,
D.; Eiroa, C.; Ferlet, R.; Grady, C. A.; Davies, J. K.; Miranda,
L. F.; Oudmaijer, R. D.; Palacios, J.; Quirrenbach, A.; Harris, A. W.;
Rauer, H.; Collier Cameron, A.; Deeg, H. J.; Garzón, F.; Penny, A.;
Schneider, J.; Tsapras, Y.; Wesselius, P. R.
Bibcode: 2001A&A...378..116M
Altcode:
In this paper we present the first comprehensive results extracted from
the spectroscopic campaigns carried out by the EXPORT (EXoPlanetary
Observational Research Team) consortium. During 1998-1999, EXPORT
carried out an intensive observational effort in the framework of the
origin and evolution of protoplanetary systems in order to obtain clues
on the evolutionary path from the early stages of the pre-main sequence
to stars with planets already formed. The spectral types of 70 stars,
and the projected rotational velocities, v sin i, of 45 stars, mainly
Vega-type and pre-main sequence, have been determined from intermediate-
and high-resolution spectroscopy, respectively. The first part of
the work is of fundamental importance in order to accurately place
the stars in the HR diagram and determine the evolutionary sequences;
the second part provides information on the kinematics and dynamics of
the stars and the evolution of their angular momentum. The advantage
of using the same observational configuration and methodology for all
the stars is the homogeneity of the set of parameters obtained. Results
from previous work are revised, leading in some cases to completely new
determinations of spectral types and projected rotational velocities;
for some stars no previous studies were available. Tables 1 and
2 are only, and Table 6 also, available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/378/116 Based on
observations made with the Isaac Newton and the William Herschel
telescopes operated on the island of La Palma by the Isaac Newton
Group in the Spanish Observatorio del Roque de los Muchachos of the
Instituto de Astrofísica de Canarias.
Title: VizieR Online Data Catalog: Classification and vsini of
Vega-type and PMS stars (Mora+, 2001)
Authors: Mora, A.; Merin, B.; Solano, E.; Montesinos, B.; de Winter,
D.; Eiroa, C.; Ferlet, R.; Grady, C. A.; Davies, J. K.; Miranda,
L. F.; Oudmaijer, R. D.; Palacios, J.; Quirrenbach, A.; Harris, A. W.;
Rauer, H.; Collier Cameron, A.; Deeg, H. J.; Garzon, F.; Penny, A.;
Schneider, J.; Tsapras, Y.; Wesselius, P. R. .
Bibcode: 2001yCat..33780116M
Altcode:
File table1.dat contains the log of the spectroscopic observations of
the stars in the EXPORT sample taken with the Isaac Newton Telescope
during the 1998 International Time Campaigns at the Canary Islands'
Observatories. File table2.dat contains the log of the spectroscopic
observations of the stars in the EXPORT sample taken with the William
Herschel Telescope during the 1998 International Time Campaigns at the
Canary Islands' Observatories. File table6.dat contains the results
of the spectral classification and the projected rotational velocities
for the stars in the EXPORT sample with comparisons with results from
previous work. (4 data files).
Title: VizieR Online Data Catalog: Vega-type and PMS stars UBVRI
photo-polarimetry (Oudmaijer+ 2001)
Authors: Oudmaijer, R. D.; Palacios, J.; Eiroa, C.; Davies, J. K.;
de Winter, D.; Ferlet, R.; Garzon, F.; Grady, C. A.; Collier Cameron,
A.; Deeg, H. J.; Harris, A. W.; Horne, K.; Merin, B.; Miranda, L. F.;
Montesinos, B.; Mora, A.; Penny, A.; Quirrenbach, A.; Rauer, H.;
Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P.
Bibcode: 2001yCat..33790564O
Altcode:
This table presents optical UBVRI broadband photo-polarimetry of the
EXPORT sample obtained at the 2.5m Nordic Optical Telescope. The
database consists of multi-epoch photo-polarimetry of 68
pre-main-sequence and main-sequence stars. (2 data files).
Title: EXPORT: Near-IR observations of Vega-type and pre-main
sequence stars
Authors: Eiroa, C.; Garzón, F.; Alberdi, A.; de Winter, D.; Ferlet,
R.; Grady, C. A.; Collier Cameron, A.; Davies, J. K.; Deeg, H. J.;
Harris, A. W.; Horne, K.; Merín, B.; Miranda, L. F.; Montesinos,
B.; Mora, A.; Oudmaijer, R.; Palacios, J.; Penny, A.; Quirrenbach,
A.; Rauer, H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.
Bibcode: 2001A&A...365..110E
Altcode:
We present near-IR JHK photometric data of a sample of 58 main-sequence,
mainly Vega-type, and pre-main sequence stars. The data were taken
during four observing runs in the period May 1998 to January 1999 and
form part of a coordinated effort with simultaneous optical spectroscopy
and photo-polarimetry. The near-IR colors of the MS stars correspond
in most cases to photospheric colors, although noticeable reddening
is present towards a few objects, and these stars show no brightness
variability within the observational errors. On the other hand,
the PMS stars show near-IR excesses and variability consistent with
previous data. Tables 1 and 2 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/110
Title: ISO-SWS Observations on Proto-Planetary System Candidates
Authors: Palacios, J.; Wesselius, P. R.; Eiroa, C.; Mora, A.;
Montesinos, B.; Merin, B.; Solano, E.; Alberdi, A.; Collier Cameron,
A.; Davies, J. K.; Deeg, H. J.; Ferlet, R.; Garzón, F.; Grady, C. A.;
Harris, A.; Horne, K.; Miranda, L. F.; Oudmaijer, R. D.; Penny, A.;
Quirrenbach, A.; Rauer, H.; Schneider, J.; Tsapras, Y.; de Winter, D.
Bibcode: 2000ESASP.456..219P
Altcode: 2000ibp..conf..219P
We present a preliminary analysis of ISO-SWS spectra of a sample of
Vega-type and pre-main sequence stars, which were observed from the
ground in a project devoted to the study of formation and evolution
of planetary systems, carried out during the 1998 International Time
of the Canary Islands Observatories. ISO-SWS covers many interesting
features expected to be present in Vega-type and pre-main sequence
objects. Most of the Vega-type stars shows photospheric spectral energy
distributions up to ≈ 10 μm, while an IR excess is normally observed
at wavelengths larger than ≈ 20 μm. Pre-main sequence (PMS) stars
usually shows IR excesses along the whole SWS spectral range. The 10
μm silicate feature is observed in emission towards most of the PMS
stars, while it is observed in only one Vega-type star in our sample,
51 Oph. The comparison of the silicate features observed towards the
protoplanetary systems with the silicate band profiles of the Trapezium
and comet Kohoutek suggests a better agreement with the solar system
cometary silicates.
Title: VizieR Online Data Catalog: JHK photometry of Vega-type and
PMS stars (Eiroa+, 2001)
Authors: Eiroa, C.; Garzon, F.; Alberdi, A.; de Winter, D.; Ferlet,
R.; Grady, C. A.; Collier Cameron, A.; Davies, J. K.; Deeg, H. J.;
Harris, A. W.; Horne, K.; Merin, B.; Miranda, L. F.; Montesinos, B.;
Mora, A.; Oudmaijer, R.; Palacios, J.; Penny, A.; Quirrenbach, A.;
Rauer, H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.
Bibcode: 2000yCat..33650110E
Altcode:
File table1.dat contains near-infrared JHK magnitudes of a sample
of 18 Vega-like and post-T Tauri stars observed by the EXPORT
collaboration. File table2.dat contains near-infrared JHK magnitudes
of a sample of 4 pre-main sequence stars observed by EXPORT. The data
were taken during four observing runs in the period May 1998 to January
1999. (3 data files).
Title: ISO-SWS Observations of EXPORT Targets (Contributed Talk)
Authors: Palacios, J.; Wesselius, P. R.; Export
Bibcode: 2000ASPC..219..255P
Altcode: 2000dpp..conf..255P
No abstract at ADS
Title: The Behavior of Vega-Type Stars in the EXPORT Sample
Authors: Mora, A.; Eiroa, C.; Palacios, J.; de Winter, D.; Ferlet,
R.; Garzón, F.; Oudmaijer, R. D.; Export
Bibcode: 2000ASPC..219..411M
Altcode: 2000dpp..conf..411M
No abstract at ADS
Title: Spectro- and Photopolarimetric Monitoring of the HAeBe Star
VV Serpentis
Authors: de Winter, D.; Mora, A.; Eiroa, C.; Palacios, J.; Oudmajier,
R. D.; Garzón, F.; Export
Bibcode: 2000ASPC..219..356D
Altcode: 2000dpp..conf..356D
No abstract at ADS
Title: The 1998 La Palma International Time Project on Exo-Planetary
Systems
Authors: Eiroa, C.; Alberdi, A.; Camron, A.; Davies, J. K.; Deeg,
H. J.; Ferlet, R.; Garzon, F.; Grady, C. A.; Harris, A.; Horne, K.;
Merin, B.; Miranda, L. F.; Montesinos, B.; Mora, A.; Oudmaijer, R.;
Palacios, J.; Penny, A.; Quirrenbach, A.; Rauer, H.; Schneider, J.;
Solano, E.; Tsapras, Y.; Wesselius, P. R.; de Winter, D.
Bibcode: 2000ESASP.451..189E
Altcode: 2000dais.conf..189E
No abstract at ADS
Title: Optical Photopolarimetry and Near-Infrared Photometry of
Pre-Main-Sequence and Main-Sequence Objects (Contributed Talk)
Authors: Oudmaijer, R. D.; Davies, J. K.; Eiroa, C.; Palacios, J.;
Garzón, F.; de Winter, D.; Export
Bibcode: 2000ASPC..219..238O
Altcode: 2000dpp..conf..238O
No abstract at ADS
Title: 1998 La Palma International Time Programme: Formation and
Properties of Planetary Systems
Authors: Eiroa, C.; Mora, A.; Palacios, J.; Alberdi, A.; Miranda,
L. F.; Cameron, A.; Horne, K.; Tsapras, Y.; Davies, L. K.; Deeg,
H. J.; Garzón, F.; de Winter, D.; Ferlet, R.; Grady, C. A.; Harris,
A.; Rauer, H.; Merín, B.; Montesinos, B.; Solano, E.; Oudmaijer,
R.; Penny, A.; Quirrenbach, A.; Schneider, J.; Wesselius, P. R.
Bibcode: 2000ASPC..219....3E
Altcode: 2000dpp..conf....3E
No abstract at ADS
Title: NGC 7129 FIRS 2: an intermediate-mass counterpart of Class
0 objects
Authors: Eiroa, C.; Palacios, J.; Casali, M. M.
Bibcode: 1998A&A...335..243E
Altcode:
We present JCMT (sub)millimetre observations of the young source
NGC 7129 FIRS 2 and HIRAS maps of the whole NGC 7129 region. The
total integrated luminosity of FIRS 2 is ~ 430 Lsun. Its
spectral energy distribution is described by a single-temperature
grey body with T = 35 K and beta = 0.9. The total mass is found to
be ~ 6 Msun. These and other properties indicate that
FIRS 2 is an intermediate-mass counterpart of the low-mass Class 0
protostellar objects; in this sense, FIRS 2 is probably the youngest
intermediate-mass object we know at present. The far-infrared emission
of NGC 7129 is dominated by two sources: FIRS 1, which is located
toward the HAeBe star LkHα 234, and FIRS 2. The cavity observed in
the optical NGC 7129 reflection nebulosity and in radio emission lines
is clearly observed in the HIRAS maps, particularly in the 25 mu m
band. The total estimated luminosity of the region is ~ 4.5 10(3)
Lsun, consistent with the idea that the dust is heated by
the cluster of HAeBe stars in NGC 7129.
Title: Kinematics and stellar populations in active galaxies: the
LINER NGC 4579 (M58).
Authors: Palacios, J.; Garcia-Vargas, M. L.; Diaz, A.; Terlevich,
R.; Terlevich, E.
Bibcode: 1997A&A...323..749P
Altcode:
We present long slit spectroscopy from the blue to the near-IR of
the LINER galaxy NGC 4579 (M58). Stellar indices are used as tools
to investigate if any differences in the kinematics and/or stellar
content exist between the nucleus and the circumnuclear regions of
the galaxy. Blue indices are found to be affected by contamination
due to emission lines in the central region and the method to
measure these indices is discussed. No peculiarities are found in
the stellar kinematics with respect to the bulges of normal spirals,
whose old population can fit the observations of the bulge of NGC
4579. Alternatively, the low central values of Mg_2_ and the high
values of Mg_1_ in the blue and MgI in the near-IR lead us to propose
the dominant bulge stellar population in NGC 4579 to be substantially
younger than the one present in ordinary ellipticals and S0 galaxies,
and therefore a population with an age of about (2.5+/-1)Gyr. and a
metallicity of (1.5+/-0.5)Zsun_ is also able to reproduce
simultaneously the studied spectral indices as well as the optical
spectral energy distribution of the nucleus of NGC 4579.
Title: A Nebulous Ring Around Serpens SVS20
Authors: Eiroa, C.; Palacios, J.; Casali, M. M.
Bibcode: 1997ASPC..119..107E
Altcode: 1997pbss.conf..107E
No abstract at ADS
Title: Time-varying Newtonian gravity - an upper limit for the rate
of change of the gravitational constant
Authors: Lapiedra, R.; Palacios, J. A.
Bibcode: 1981A&A....98..382L
Altcode:
In the Newtonian amended gravity law with a time-dependent gravitational
constant as proposed by the Bishop and Landsberg (1976) theory, the
conventional expression for the energy remains a constant of motion,
despite the fact that G depends on time. In the theory, the angular
momentum is not conserved. In the present paper the variation in time
of the angular momentum predicted by the theory is calculated for
the planets of the solar system and especially for Venus. From this
calculation and present planet eccentricities, an upper limit for the
rate of change of the time varying gravitational constant is obtained.