bellot-rubio

explanation blue bibcodes open ADS page with paths to full text

Author name code: bellot-rubio
ADS astronomy entries on 2022-09-14
author:"Bellot Rubio, Luis Ramon"

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Title: The on-ground data reduction and calibration pipeline for
SO/PHI-HRT
Authors: Sinjan, J.; Calchetti, D.; Hirzberger, J.; Orozco Suárez,
D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero,
A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero,
L.; Gutierrez Marquez, P.; Kahil, F.; Kolleck, M.; Solanki, S. K.; del
Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama,
J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez,
M.; Bellot Rubio, L. R.; Carmona, M.; Deutsch, W.; Fernandez-Rico,
G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.;
Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López
Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.;
Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub,
J.; Strecker, H.; Torralbo, I.; Valori, G.
2022arXiv220814904S Altcode:
The ESA/NASA Solar Orbiter space mission has been successfully launched
in February 2020. Onboard is the Polarimetric and Helioseismic Imager
(SO/PHI), which has two telescopes, a High Resolution Telescope
(HRT) and the Full Disc Telescope (FDT). The instrument is designed
to infer the photospheric magnetic field and line-of-sight velocity
through differential imaging of the polarised light emitted by the
Sun. It calculates the full Stokes vector at 6 wavelength positions
at the Fe I 617.3 nm absorption line. Due to telemetry constraints,
the instrument nominally processes these Stokes profiles onboard,
however when telemetry is available, the raw images are downlinked and
reduced on ground. Here the architecture of the on-ground pipeline
for HRT is presented, which also offers additional corrections not
currently available on board the instrument. The pipeline can reduce
raw images to the full Stokes vector with a polarimetric sensitivity
of $10^{-3}\cdot I_{c}$ or better.

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Title: Unipolar versus Bipolar Internetwork Flux Appearance
Authors: Gosic, Milan; Katsukawa, Yukio; Bellot Rubio, L. R.; Del
Toro Iniesta, Jose Carlos; Cheung, Mark; Orozco Suárez, David
2022cosp...44.2513G Altcode:
Small-scale internetwork (IN) magnetic fields are considered to be
the main building blocks of the quiet Sun magnetism. It is therefore
of paramount importance to understand how these fields are generated
on the solar surface. To shed new light on this open question,
we studied the appearance modes and spatio-temporal evolution of
individual IN magnetic elements inside one supergranular cell. For
that purpose, we employed a high-resolution, high-sensitivity,
long-duration Hinode/NFI magnetogram sequence. From identification
of flux patches and magnetofrictional simulations, we show that there
are two distinct populations of IN flux concentrations: unipolar and
bipolar features. Bipolar features tend to be bigger, live longer
and carry more flux than unipolar features. About $70$% of the total
instantaneous IN flux detected inside the supergranule is in the form
of bipoles. Both types of flux concentrations are uniformly distributed
over the solar surface. However, bipolar features appear (randomly
oriented) at a faster rate than unipolar features (68 as opposed to
55~Mx~cm$^{-2}$~day$^{-1}$). Our results lend support to the idea that
bipolar features may be the signature of local dynamo action, while
unipolar features seem to be formed by coalescence of background flux.

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Title: Emergence of internetwork magnetic fields into the chromosphere
and transition region
Authors: Gosic, Milan; De Pontieu, Bart; Bellot Rubio, L. R.; Sainz
Dalda, A.; Esteban Pozuelo, Sara
2022cosp...44.2511G Altcode:
Internetwork (IN) magnetic fields are highly dynamic, short-lived
magnetic structures that populate the interior of supergranular
cells. Since they are spread all over the Sun, they may hold a
significant fraction of the total magnetic energy stored in the
photosphere. Therefore, it is crucial to understand their role in the
quiet Sun magnetism and impact on the energetics and dynamics of the
solar atmosphere. To provide new insights into this topic, we studied
three flux emergence events and followed them as they emerge into the
photosphere and reach the chromosphere and transition region. We used
coordinated, high-resolution, multiwavelength observations obtained with
the Swedish 1-m Solar Telescope (SST) and the Interface Region Imaging
Spectrograph (IRIS). SST Fe I 6173 and Mg I b$_2$ 5173 magnetograms
show the footpoints of the IN bipoles emerging at the solar surface
and rising toward the upper solar atmosphere. For the first time, our
spectropolarimetric measurements in the Ca II 8542 \AA\/ line provide
direct observational evidence that IN fields are capable of reaching
the chromosphere. IRIS observations reveal another important piece of
information - small-scale IN loops can even reach transition region
heights, and locally heat the upper solar atmosphere.

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Title: Magnetic properties of short-lived penumbral microjets
Authors: Tapia, Azaymi Siu; Bellot Rubio, L. R.; Gafeira, Ricardo;
Orozco Suárez, David
2022cosp...44.2520T Altcode:
Penumbral microjets (PMJs) are fast elongated brightenings above
sunspots penumbrae. They are presumed to be related to photospheric
magnetic reconnection processes and contribute to the heating of the
plasma in the higher atmospheric layers. Studying the spectral and
polarization properties of the shortest-living microjets requires
the fastest temporal cadence possible and is currently a challenging
task. In this work, we use fast spectropolarimetric measurements of
the Ca II 8542 A line made with the CRISP instrument at the Swedish
1 m Solar Telescope, and exploit the diagnostic capabilities of this
line to retrieve the magnetic field configuration and its evolution
at different atmospheric heights during PMJs. Our findings show that
short-lived PMJs are associated with a transient perturbation in
the photospheric magnetic field and sometimes they show clear but
weaker changes in the chromospheric field as well. We will describe
the different types of evolution that were identified. These results
support the idea that PMJs may be the result of magnetic reconnection
at low altitudes in sunspot penumbra.

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Title: The magnetic canopy of pores and quiet Sun features as observed
through the Mg I b2 line
Authors: Tapia, Azaymi Siu; Bellot Rubio, L. R.
2022cosp...44.2512T Altcode:
We study the expansion of the magnetic field above pores and quiet
Sun magnetic elements from the photosphere to the low chromosphere,
using high-spatial-resolution observations in the Fe I 6173 Å and Mg
I 5173 Å lines made with CRISP at the SST. The longitudinal component
of the magnetic field and its variation with height have been inferred
by applying the weak-field approximation (WFA) in different spectral
windows within the Mg line and a simple SIR inversion to the Fe line. We
also present the first non-LTE inversions of these two lines performed
over a large field of view. The results from such inversions validate
the applicability of the WFA as a diagnostic tool that can be used
to analyze the magnetic field intensity and orientation, as well as
their gradients with height, in these lines. This work also provides
observational evidence on the formation of low-lying canopies above
bright quiet Sun magnetic structures, network elements, and pores,
near the temperature minimum region.

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Title: The European Solar Telescope
Authors: Quintero Noda, C.; Schlichenmaier, R.; Bellot Rubio, L. R.;
Löfdahl, M. G.; Khomenko, E.; Jurcak, J.; Leenaarts, J.; Kuckein,
C.; González Manrique, S. J.; Gunar, S.; Nelson, C. J.; de la Cruz
Rodríguez, J.; Tziotziou, K.; Tsiropoula, G.; Aulanier, G.; Collados,
M.; the EST team
2022arXiv220710905Q Altcode:
The European Solar Telescope (EST) is a project aimed at studying
the magnetic connectivity of the solar atmosphere, from the deep
photosphere to the upper chromosphere. Its design combines the knowledge
and expertise gathered by the European solar physics community during
the construction and operation of state-of-the-art solar telescopes
operating in visible and near-infrared wavelengths: the Swedish 1m Solar
Telescope (SST), the German Vacuum Tower Telescope (VTT) and GREGOR,
the French Télescope Héliographique pour l'Étude du Magnétisme
et des Instabilités Solaires (THÉMIS), and the Dutch Open Telescope
(DOT). With its 4.2 m primary mirror and an open configuration, EST will
become the most powerful European ground-based facility to study the Sun
in the coming decades in the visible and near-infrared bands. EST uses
the most innovative technological advances: the first adaptive secondary
mirror ever used in a solar telescope, a complex multi-conjugate
adaptive optics with deformable mirrors that form part of the optical
design in a natural way, a polarimetrically compensated telescope design
that eliminates the complex temporal variation and wavelength dependence
of the telescope Mueller matrix, and an instrument suite containing
several (etalon-based) tunable imaging spectropolarimeters and several
integral field unit spectropolarimeters. This publication summarises
some fundamental science questions that can be addressed with the
telescope, together with a complete description of its major subsystems.

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Title: The magnetic drivers of campfires seen by the Polarimetric
and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
2022A&A...660A.143K Altcode: 2022arXiv220213859K
Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
(SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
termed campfires, that have been proposed to be brightenings near the
apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
magnetic processes driving these campfires are not understood. Aims: During the cruise phase of SO and at a distance of 0.523
AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
offering the possibility to investigate the surface magnetic field
dynamics underlying campfires at a spatial resolution of about 380
km. Methods: We used co-spatial and co-temporal data of the
quiet-Sun network at disc centre acquired with the High Resolution
Imager of SO/EUI at 17.4 nm (HRIEUV, cadence 2 s) and the
High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
min). Campfires that are within the SO/PHI−SO/EUI common field
of view were isolated and categorised according to the underlying
magnetic activity. Results: In 71% of the 38 isolated events,
campfires are confined between bipolar magnetic features, which seem to
exhibit signatures of magnetic flux cancellation. The flux cancellation
occurs either between the two main footpoints, or between one of the
footpoints of the loop housing the campfire and a nearby opposite
polarity patch. In one particularly clear-cut case, we detected the
emergence of a small-scale magnetic loop in the internetwork followed
soon afterwards by a campfire brightening adjacent to the location
of the linear polarisation signal in the photosphere, that is to
say near where the apex of the emerging loop lays. The rest of the
events were observed over small scattered magnetic features, which
could not be identified as magnetic footpoints of the campfire hosting
loops. Conclusions: The majority of campfires could be driven
by magnetic reconnection triggered at the footpoints, similar to the
physical processes occurring in the burst-like EUV events discussed
in the literature. About a quarter of all analysed campfires, however,
are not associated to such magnetic activity in the photosphere, which
implies that other heating mechanisms are energising these small-scale
EUV brightenings.

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Title: CASPER: A mission to study the time-dependent evolution of
the magnetic solar chromosphere and transition regions
Authors: Orozco Suárez, D.; del Toro Iniesta, J. C.; Bailén, F. J.;
López Jiménez, A.; Balaguez Jiménez, M.; Bellot Rubio, L. R.;
Ishikawa, R.; Katsukawa, Y.; Kano, R.; Shimizu, T.; Trujillo Bueno,
J.; Asensio Ramos, A.; del Pino Alemán, T.
2022ExA...tmp...26O Altcode:
Our knowledge about the solar chromosphere and transition region (TR)
has increased in the last decade thanks to the huge scientific return
of space-borne observatories like SDO, IRIS, and Hinode, and suborbital
rocket experiments like CLASP1, CLASP2, and Hi-C. However, the magnetic
nature of those solar regions remain barely explored. The chromosphere
and TR of the Sun harbor weak fields and are in a low ionization stage
both having critical effects on their thermodynamic behavior. Relatively
cold gas structures, such as spicules and prominences, are located in
these two regions and display a dynamic evolution in high-resolution
observations that static and instantaneous 3D-magnetohydrodynamic (MHD)
models are not able to reproduce. The role of the chromosphere and TR
as the necessary path to a (largely unexplained) very hot corona calls
for the generation of observationally based, time-dependent models
of these two layers that include essential, up to now disregarded,
ingredients in the modeling such as the vector magnetic field. We
believe that the community is convinced that the origin of both the
heat and kinetic energy observed in the upper layers of the solar
atmosphere is of magnetic origin, but reliable magnetic field
measurements are missing. The access to sensitive polarimetric
measurements in the ultraviolet wavelengths has been elusive until
recently due to limitations in the available technology. We propose a
low-risk and high-Technology Readiness Level (TRL) mission to explore
the magnetism and dynamics of the solar chromosphere and TR. The mission
baseline is a low-Earth, Sun-synchronous orbit at an altitude between
600 and 800 km. The proposed scientific payload consists of a 30 cm
aperture telescope with a spectropolarimeter covering the hydrogen
Ly-alpha and the Mg II h&amp;k ultraviolet lines. The instrument shall
record high-cadence, full spectropolarimetric observations of the
solar upper atmosphere. Besides the answers to a fundamental solar
problem the mission has a broader scientific return. For example,
the time-dependent modeling of the chromospheres of stars harboring
exoplanets is fundamental for estimating the planetary radiation
environment. The mission is based on technologies that are mature
enough for space and will provide scientific measurements that are
not available by other means.

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Title: The Solar Internetwork. III. Unipolar versus Bipolar Flux
Appearance
Authors: Gošić, M.; Bellot Rubio, L. R.; Cheung, M. C. M.; Orozco
Suárez, D.; Katsukawa, Y.; del Toro Iniesta, J. C.
2022ApJ...925..188G Altcode: 2021arXiv211103208G
Small-scale internetwork (IN) magnetic fields are considered to be the
main building blocks of quiet Sun magnetism. For this reason, it is
crucial to understand how they appear on the solar surface. Here,
we employ a high-resolution, high-sensitivity, long-duration
Hinode/NFI magnetogram sequence to analyze the appearance modes and
spatiotemporal evolution of individual IN magnetic elements inside a
supergranular cell at the disk center. From identification of flux
patches and magnetofrictional simulations, we show that there are
two distinct populations of IN flux concentrations: unipolar and
bipolar features. Bipolar features tend to be bigger and stronger
than unipolar features. They also live longer and carry more flux
per feature. Both types of flux concentrations appear uniformly over
the solar surface. However, we argue that bipolar features truly
represent the emergence of new flux on the solar surface, while
unipolar features seem to be formed by the coalescence of background
flux. Magnetic bipoles appear at a faster rate than unipolar features
(68 as opposed to 55 Mx cm-2 day-1), and provide
about 70% of the total instantaneous IN flux detected in the interior
of the supergranule.

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Title: A journey of exploration to the polar regions of a star:
probing the solar poles and the heliosphere from high helio-latitude
Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry;
Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier,
Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry;
Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle,
Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.;
Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic,
Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen,
Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli,
Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.
2021ExA...tmp...93H Altcode: 2021arXiv210410876H
A mission to view the solar poles from high helio-latitudes (above 60°)
will build on the experience of Solar Orbiter as well as a long heritage
of successful solar missions and instrumentation (e.g. SOHO Domingo et
al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space
Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar
Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2),
3-15 2012), but will focus for the first time on the solar poles,
enabling scientific investigations that cannot be done by any other
mission. One of the major mysteries of the Sun is the solar cycle. The
activity cycle of the Sun drives the structure and behaviour of the
heliosphere and of course, the driver of space weather. In addition,
solar activity and variability provides fluctuating input into the
Earth climate models, and these same physical processes are applicable
to stellar systems hosting exoplanets. One of the main obstructions
to understanding the solar cycle, and hence all solar activity,
is our current lack of understanding of the polar regions. In this
White Paper, submitted to the European Space Agency in response to the
Voyage 2050 call, we describe a mission concept that aims to address
this fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.

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Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
2021SoPh..296...70R Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.

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Title: Emergence of Internetwork Magnetic Fields through the Solar
Atmosphere
Authors: Gošić, M.; De Pontieu, B.; Bellot Rubio, L. R.; Sainz Dalda,
A.; Pozuelo, S. Esteban
2021ApJ...911...41G Altcode: 2021arXiv210302213G
Internetwork (IN) magnetic fields are highly dynamic, short-lived
magnetic structures that populate the interior of supergranular
cells. Since they emerge all over the Sun, these small-scale fields
bring a substantial amount of flux, and therefore energy, to the solar
surface. Because of this, IN fields are crucial for understanding
the quiet Sun (QS) magnetism. However, they are weak and produce very
small polarization signals, which is the reason why their properties
and impact on the energetics and dynamics of the solar atmosphere are
poorly known. Here we use coordinated, high-resolution, multiwavelength
observations obtained with the Swedish 1 m Solar Telescope and the
Interface Region Imaging Spectrograph (IRIS) to follow the evolution
of IN magnetic loops as they emerge into the photosphere and reach
the chromosphere and transition region. We studied in this paper three
flux emergence events having total unsigned magnetic fluxes of 1.9 ×
1018, 2.5 × 1018, and 5.3 × 1018
Mx. The footpoints of the emerging IN bipoles are clearly seen
to appear in the photosphere and to rise up through the solar
atmosphere, as observed in Fe I 6173 Å and Mg I b2 5173
Å magnetograms, respectively. For the first time, our polarimetric
measurements taken in the chromospheric Ca II 8542 Å line provide
direct observational evidence that IN fields are capable of reaching the
chromosphere. Moreover, using IRIS data, we study the effects of these
weak fields on the heating of the chromosphere and transition region.

---------------------------------------------------------
Title: A Journey of Exploration to the Polar Regions of a Star:
Probing the Solar Poles and the Heliosphere from High Helio-Latitude
Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.;
Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.;
Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi,
S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.;
Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.;
Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli,
M.; Sekii, T.; Spadaro, D.; Veronig, A.
2020AGUFMSH0110005F Altcode:
A mission to view the solar poles from high helio-latitudes (above
60°) will build on the experience of Solar Orbiter as well as a long
heritage of successful solar missions and instrumentation (e.g. SOHO,
STEREO, Hinode, SDO), but will focus for the first time on the solar
poles, enabling scientific investigations that cannot be done by
any other mission. One of the major mysteries of the Sun is the solar
cycle. The activity cycle of the Sun drives the structure and behaviour
of the heliosphere and is, of course, the driver of space weather. In
addition, solar activity and variability provides fluctuating input
into the Earth climate models, and these same physical processes
are applicable to stellar systems hosting exoplanets. One of the
main obstructions to understanding the solar cycle, and hence all
solar activity, is our current lack of understanding of the polar
regions. We describe a mission concept that aims to address this
fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.

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Title: Lagrangian chaotic saddles and objective vortices in solar
plasmas
Authors: Chian, Abraham C. -L.; Silva, Suzana S. A.; Rempel, Erico L.;
Bellot Rubio, Luis R.; Gošić, Milan; Kusano, Kanya; Park, Sung-Hong
2020PhRvE.102f0201C Altcode:
We report observational evidence of Lagrangian chaotic saddles
in plasmas, given by the intersections of finite-time unstable and
stable manifolds, using an ≈22 h sequence of spacecraft images of the
horizontal velocity field of solar photosphere. A set of 29 persistent
objective vortices with lifetimes varying from 28.5 to 298.3 min are
detected by computing the Lagrangian averaged vorticity deviation. The
unstable manifold of the Lagrangian chaotic saddles computed for ≈11
h exhibits twisted folding motions indicative of recurring vortices in
a magnetic mixed-polarity region. We show that the persistent objective
vortices are formed in the gap regions of Lagrangian chaotic saddles
at supergranular junctions.

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Title: Chromospheric response to emergence of internetwork magnetic
fields
Authors: Gosic, M.; De Pontieu, B.; Bellot Rubio, L.; Sainz Dalda, A.
2020AGUFMSH0010006G Altcode:
Internetwork (IN) magnetic fields are weak, short-lived, but highly
dynamic magnetic structures that emerge all over the Sun. They
bring an enormous amount of magnetic flux and energy to the solar
surface. Therefore, IN fields are of paramount importance for
maintenance of the QS magnetism. Since these fields are ubiquitous,
they may have a substantial impact on the energetics and dynamics of the
solar atmosphere. In this work, we use coordinated, high-resolution,
multiwavelength observations obtained with the Interface Region
Imaging Spectrograph (IRIS) and the Swedish 1 m Solar Telescope (SST)
to follow the evolution of IN magnetic loops as they emerge into the
photosphere. The footpoints of the emerging IN bipoles are clearly
visible as they appear in the photosphere and rise up through the
solar atmosphere, as seen in SST magnetograms taken in the Fe I
6173 Å and Mg I b2 5173 Å lines, respectively. Our polarimetric
measurements, taken in the Ca II 8542 Å line, provide the first
direct observational evidence that IN fields are capable of reaching
the chromosphere. Moreover, using IRIS data, we describe in detail
how individual IN bipoles affect the dynamics and energetics of the
chromosphere and transition region.

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Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.

---------------------------------------------------------
Title: The Polarimetric and Helioseismic Imager on Solar Orbiter
Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer,
A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez
Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.;
Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.;
Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.;
Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.;
Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott,
D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.;
Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.;
Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.;
Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.;
Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos
Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.;
Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.;
Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila,
B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.;
Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.;
Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond,
J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h,
J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.;
Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell,
A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai,
E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco
Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa,
J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas,
A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.;
Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel,
H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I.
2020A&A...642A..11S Altcode: 2019arXiv190311061S
 Aims: This paper describes the Polarimetric and Helioseismic
Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and
helioseismology instrument to observe the Sun from outside the Sun-Earth
line. It is the key instrument meant to address the top-level science
question: How does the solar dynamo work and drive connections between
the Sun and the heliosphere? SO/PHI will also play an important role
in answering the other top-level science questions of Solar Orbiter,
while hosting the potential of a rich return in further science. Methods: SO/PHI measures the Zeeman effect and the Doppler shift
in the Fe I 617.3 nm spectral line. To this end, the instrument
carries out narrow-band imaging spectro-polarimetry using a tunable
LiNbO3 Fabry-Perot etalon, while the polarisation modulation
is done with liquid crystal variable retarders. The line and the nearby
continuum are sampled at six wavelength points and the data are recorded
by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data
are reduced on board, including being inverted under the assumption of
a Milne-Eddington atmosphere, although simpler reduction methods are
also available on board. SO/PHI is composed of two telescopes; one,
the Full Disc Telescope, covers the full solar disc at all phases of
the orbit, while the other, the High Resolution Telescope, can resolve
structures as small as 200 km on the Sun at closest perihelion. The high
heat load generated through proximity to the Sun is greatly reduced by
the multilayer-coated entrance windows to the two telescopes that allow
less than 4% of the total sunlight to enter the instrument, most of
it in a narrow wavelength band around the chosen spectral line. 
Results: SO/PHI was designed and built by a consortium having partners
in Germany, Spain, and France. The flight model was delivered to
Airbus Defence and Space, Stevenage, and successfully integrated into
the Solar Orbiter spacecraft. A number of innovations were introduced
compared with earlier space-based spectropolarimeters, thus allowing
SO/PHI to fit into the tight mass, volume, power and telemetry budgets
provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal)
challenges posed by the mission's highly elliptical orbit.

---------------------------------------------------------
Title: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
A. N.
2020A&A...642A...2R Altcode:
Context. The Solar Orbiter spacecraft will be equipped with a wide
range of remote-sensing (RS) and in situ (IS) instruments to record
novel and unprecedented measurements of the solar atmosphere and
the inner heliosphere. To take full advantage of these new datasets,
tools and techniques must be developed to ease multi-instrument and
multi-spacecraft studies. In particular the currently inaccessible
low solar corona below two solar radii can only be observed
remotely. Furthermore techniques must be used to retrieve coronal
plasma properties in time and in three dimensional (3D) space. Solar
Orbiter will run complex observation campaigns that provide interesting
opportunities to maximise the likelihood of linking IS data to their
source region near the Sun. Several RS instruments can be directed
to specific targets situated on the solar disk just days before
data acquisition. To compare IS and RS, data we must improve our
understanding of how heliospheric probes magnetically connect to the
solar disk. Aims: The aim of the present paper is to briefly
review how the current modelling of the Sun and its atmosphere
can support Solar Orbiter science. We describe the results of a
community-led effort by European Space Agency's Modelling and Data
Analysis Working Group (MADAWG) to develop different models, tools,
and techniques deemed necessary to test different theories for the
physical processes that may occur in the solar plasma. The focus here
is on the large scales and little is described with regards to kinetic
processes. To exploit future IS and RS data fully, many techniques have
been adapted to model the evolving 3D solar magneto-plasma from the
solar interior to the solar wind. A particular focus in the paper is
placed on techniques that can estimate how Solar Orbiter will connect
magnetically through the complex coronal magnetic fields to various
photospheric and coronal features in support of spacecraft operations
and future scientific studies. Methods: Recent missions such as
STEREO, provided great opportunities for RS, IS, and multi-spacecraft
studies. We summarise the achievements and highlight the challenges
faced during these investigations, many of which motivated the Solar
Orbiter mission. We present the new tools and techniques developed
by the MADAWG to support the science operations and the analysis of
the data from the many instruments on Solar Orbiter. Results:
This article reviews current modelling and tool developments that ease
the comparison of model results with RS and IS data made available
by current and upcoming missions. It also describes the modelling
strategy to support the science operations and subsequent exploitation
of Solar Orbiter data in order to maximise the scientific output
of the mission. Conclusions: The on-going community effort
presented in this paper has provided new models and tools necessary
to support mission operations as well as the science exploitation of
the Solar Orbiter data. The tools and techniques will no doubt evolve
significantly as we refine our procedure and methodology during the
first year of operations of this highly promising mission.

---------------------------------------------------------
Title: Temporal evolution of short-lived penumbral microjets
Authors: Siu-Tapia, A. L.; Bellot Rubio, L. R.; Orozco Suárez, D.;
Gafeira, R.
2020A&A...642A.128S Altcode: 2020arXiv200715926S
Context. Penumbral microjets (PMJs) is the name given to elongated
jet-like brightenings observed in the chromosphere above sunspot
penumbrae. They are transient events that last from a few seconds
to several minutes, and their origin is presumed to be related to
magnetic reconnection processes. Previous studies have mainly focused
on their morphological and spectral characteristics, and more recently
on their spectropolarimetric signals during the maximum brightness
stage. Studies addressing the temporal evolution of PMJs have also
been carried out, but they are based on spatial and spectral time
variations only. Aims: Here we investigate, for the first
time, the temporal evolution of the polarization signals produced by
short-lived PMJs (lifetimes &lt; 2 min) to infer how the magnetic field
vector evolves in the upper photosphere and mid-chromosphere. 
Methods: We use fast-cadence spectropolarimetric observations of the
Ca II 854.2 nm line taken with the CRisp Imaging Spectropolarimeter
at the Swedish 1 m Solar Telescope. The weak-field approximation (WFA)
is used to estimate the strength and inclination of the magnetic field
vector. By separating the Ca II 854.2 nm line into two different
wavelength domains to account for the chromospheric origin of the
line core and the photospheric contribution to the wings, we infer
the height variation of the magnetic field vector. Results:
The WFA reveals larger magnetic field changes in the upper photosphere
than in the chromosphere during the PMJ maximum brightness stage. In
the photosphere, the magnetic field inclination and strength undergo
a transient increase for most PMJs, but in 25% of the cases the field
strength decreases during the brightening. In the chromosphere, the
magnetic field tends to be slightly stronger during the PMJs. Conclusions: The propagation of compressive perturbation fronts
followed by a rarefaction phase in the aftershock region may explain
the observed behavior of the magnetic field vector. The fact that such
behavior varies among the analyzed PMJs could be a consequence of the
limited temporal resolution of the observations and the fast-evolving
nature of the PMJs.

---------------------------------------------------------
Title: Magnetic properties of short-lived penumbral microjets
Authors: Siu-Tapia, A.; Bellot Rubio, L.; Orozco Suárez, D.;
Gafeira, R.
2020sea..confE.208S Altcode:
We investigate the temporal evolution of the polarization properties
during penumbral microjets (PMJs). Studying the magnetic properties
of these transients requires spectropolarimetric observations with
the fastest temporal cadence possible and is currently a challenging
task. In this work, we used fast temporal cadence spectropolarimetric
measurements of the Ca II 8542 Å line from the CRISP instrument at the
Swedish 1 m Solar Telescope, and exploited the diagnosis capabilities of
this line to retrieve the magnetic field configuration and its evolution
at different atmospheric heights during PMJs. Our findings show that
the short-lived PMJs are associated to a transient perturbation in
the photospheric magnetic field and sometimes they show clear but
weaker changes in the chromospheric field as well. Here we describe
the different types of evolution that were identified.

---------------------------------------------------------
Title: On the Magnetic Nature of an Exploding Granule as Revealed
by Sunrise/IMaX
Authors: Guglielmino, Salvo L.; Martínez Pillet, Valentín; Ruiz
Cobo, Basilio; Bellot Rubio, Luis R.; del Toro Iniesta, José Carlos;
Solanki, Sami K.; Riethmüller, Tino L.; Zuccarello, Francesca
2020ApJ...896...62G Altcode: 2020arXiv200503371G
We study the photospheric evolution of an exploding granule
observed in the quiet Sun at high spatial (∼0"3) and temporal
(31.5 s) resolution by the imaging magnetograph Sunrise/IMaX in 2009
June. These observations show that the exploding granule is cospatial
to a magnetic flux emergence event occurring at mesogranular scale
(up to ∼12 Mm2 area). Using a modified version of the
SIR code for inverting the IMaX spectropolarimetric measurements, we
obtain information about the magnetic configuration of this photospheric
feature. In particular, we find evidence of highly inclined emerging
fields in the structure, carrying a magnetic flux content up to ∼4
× 1018 Mx. The balance between gas and magnetic pressure
in the region of flux emergence, compared with a very quiet region of
the Sun, indicates that the additional pressure carried by the emerging
flux increases the total pressure by about 5% and appears to allow the
granulation to be modified, as predicted by numerical simulations. The
overall characteristics suggest that a multipolar structure emerges
into the photosphere, resembling an almost horizontal flux sheet. This
seems to be associated with exploding granules. Finally, we discuss
the origin of such flux emergence events.

---------------------------------------------------------
Title: Solar physics in the 2020s: DKIST, parker solar probe, and
solar orbiter as a multi-messenger constellation
Authors: Martinez Pillet, V.; Tritschler, A.; Harra, L.; Andretta, V.;
Vourlidas, A.; Raouafi, N.; Alterman, B. L.; Bellot Rubio, L.; Cauzzi,
G.; Cranmer, S. R.; Gibson, S.; Habbal, S.; Ko, Y. K.; Lepri, S. T.;
Linker, J.; Malaspina, D. M.; Matthews, S.; Parenti, S.; Petrie, G.;
Spadaro, D.; Ugarte-Urra, I.; Warren, H.; Winslow, R.
2020arXiv200408632M Altcode:
The National Science Foundation (NSF) Daniel K. Inouye Solar Telescope
(DKIST) is about to start operations at the summit of Haleakala
(Hawaii). DKIST will join the early science phases of the NASA
and ESA Parker Solar Probe and Solar Orbiter encounter missions. By
combining in-situ measurements of the near-sun plasma environment and
detail remote observations of multiple layers of the Sun, the three
observatories form an unprecedented multi-messenger constellation to
study the magnetic connectivity inside the solar system. This white
paper outlines the synergistic science that this multi-messenger
suite enables.

---------------------------------------------------------
Title: Science Requirement Document (SRD) for the European Solar
Telescope (EST) (2nd edition, December 2019)
Authors: Schlichenmaier, R.; Bellot Rubio, L. R.; Collados, M.;
Erdelyi, R.; Feller, A.; Fletcher, L.; Jurcak, J.; Khomenko, E.;
Leenaarts, J.; Matthews, S.; Belluzzi, L.; Carlsson, M.; Dalmasse,
K.; Danilovic, S.; Gömöry, P.; Kuckein, C.; Manso Sainz, R.;
Martinez Gonzalez, M.; Mathioudakis, M.; Ortiz, A.; Riethmüller,
T. L.; Rouppe van der Voort, L.; Simoes, P. J. A.; Trujillo Bueno,
J.; Utz, D.; Zuccarello, F.
2019arXiv191208650S Altcode:
The European Solar Telescope (EST) is a research infrastructure
for solar physics. It is planned to be an on-axis solar telescope
with an aperture of 4 m and equipped with an innovative suite of
spectro-polarimetric and imaging post-focus instrumentation. The EST
project was initiated and is driven by EAST, the European Association
for Solar Telescopes. EAST was founded in 2006 as an association
of 14 European countries. Today, as of December 2019, EAST consists
of 26 European research institutes from 18 European countries. The
Preliminary Design Phase of EST was accomplished between 2008 and
2011. During this phase, in 2010, the first version of the EST Science
Requirement Document (SRD) was published. After EST became a project
on the ESFRI roadmap 2016, the preparatory phase started. The goal
of the preparatory phase is to accomplish a final design for the
telescope and the legal governance structure of EST. A major milestone
on this path is to revisit and update the Science Requirement Document
(SRD). The EST Science Advisory Group (SAG) has been constituted by
EAST and the Board of the PRE-EST EU project in November 2017 and has
been charged with the task of providing with a final statement on the
science requirements for EST. Based on the conceptual design, the SRD
update takes into account recent technical and scientific developments,
to ensure that EST provides significant advancement beyond the current
state-of-the-art. The present update of the EST SRD has been developed
and discussed during a series of EST SAG meetings. The SRD develops
the top-level science objectives of EST into individual science
cases. Identifying critical science requirements is one of its main
goals. Those requirements will define the capabilities of EST and the
post-focus instrument suite. The technical requirements for the final
design of EST will be derived from the SRD.

---------------------------------------------------------
Title: Erratum: Supergranular turbulence in the quiet Sun: Lagrangian
coherent structures
Authors: Chian, Abraham C. -L.; Silva, Suzana S. A.; Rempel, Erico
L.; Gošić; , Milan; Bellot Rubio, Luis R.; Kusano, Kanya; Miranda,
Rodrigo A.; Requerey, Iker S.
2019MNRAS.489..707C Altcode: 2019MNRAS.tmp.2225C
No abstract at ADS

---------------------------------------------------------
Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
Peter R.
2019PASJ...71R...1H Altcode:
Hinode is Japan's third solar mission following Hinotori (1981-1982)
and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
operation currently. Hinode carries three instruments: the Solar Optical
Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
instruments were built under international collaboration with the
National Aeronautics and Space Administration and the UK Science and
Technology Facilities Council, and its operation has been contributed
to by the European Space Agency and the Norwegian Space Center. After
describing the satellite operations and giving a performance evaluation
of the three instruments, reviews are presented on major scientific
discoveries by Hinode in the first eleven years (one solar cycle long)
of its operation. This review article concludes with future prospects
for solar physics research based on the achievements of Hinode.

---------------------------------------------------------
Title: Supergranular turbulence in the quiet Sun: Lagrangian coherent
structures
Authors: Chian, Abraham C. -L.; Silva, Suzana S. A.; Rempel, Erico
L.; Gošić; , Milan; Bellot Rubio, Luis R.; Kusano, Kanya; Miranda,
Rodrigo A.; Requerey, Iker S.
2019MNRAS.488.3076C Altcode: 2019MNRAS.tmp.1841C; 2019arXiv190408472C
The quiet Sun exhibits a wealth of magnetic activities that are
fundamental for our understanding of solar magnetism. The magnetic
fields in the quiet Sun are observed to evolve coherently, interacting
with each other to form prominent structures as they are advected by
photospheric flows. The aim of this paper is to study supergranular
turbulence by detecting Lagrangian coherent structures (LCS) based on
the horizontal velocity fields derived from Hinode intensity images at
disc centre of the quiet Sun on 2010 November 2. LCS act as transport
barriers and are responsible for attracting/repelling the fluid elements
and swirling motions in a finite time. Repelling/attracting LCS are
found by computing the forward/backward finite-time Lyapunov exponent
(FTLE), and vortices are found by the Lagrangian-averaged vorticity
deviation method. We show that the Lagrangian centres and boundaries
of supergranular cells are given by the local maximum of the forward
and backward FTLE, respectively. The attracting LCS expose the location
of the sinks of photospheric flows at supergranular junctions, whereas
the repelling LCS interconnect the Lagrangian centres of neighbouring
supergranular cells. Lagrangian transport barriers are found within a
supergranular cell and from one cell to other cells, which play a key
role in the dynamics of internetwork and network magnetic elements. Such
barriers favour the formation of vortices in supergranular junctions. In
particular, we show that the magnetic field distribution in the quiet
Sun is determined by the combined action of attracting/repelling LCS
and vortices.

---------------------------------------------------------
Title: Evolution of bipolar internetwork magnetic fields
Authors: Gosic, Milan; De Pontieu, Bart; Bellot Rubio, Luis Ramon
2019AAS...23431102G Altcode:
Internetwork (IN) magnetic fields can be found inside supergranular
cells all over the solar surface. Thanks to their abundance and
appearance rate, IN fields are considered to be an essential contributor
to the magnetic flux and energy budget of the solar photosphere, and
may also play a major role in the energy budget of the chromosphere
and transition region. Therefore, it is crucial to understand how
IN magnetic fields appear, evolve, interact with the preexisting
magnetic structures, and what impact they have on the upper solar
atmosphere. Here, we analyze spatio-temporal evolution of IN magnetic
bipolar structures, i.e, loops and clusters, employing multi-instrument
(IRIS and SST), multi-wavelength observations of IN regions with the
highest sensitivity and resolution possible. For the first time, our
observations allow us to describe in detail how IN bipoles emerge in
the photosphere and even reach the chromosphere. We estimate the field
strengths of these IN magnetic structures both in the photosphere and
the chromosphere, using full Stokes measurements in Fe I 6173 Å, Mg I
b2 5173 Å, and Ca II 8542 Å. Employing the IRIS FUV and
NUV spectra, we show that IN fields contribute to the chromospheric
and transition region heating through interaction with the preexisting
ambient fields.

---------------------------------------------------------
Title: On the Magnetic Nature of Solar Exploding Granules
Authors: Guglielmino, S. L.; Martínez Pillet, V.; Ruiz Cobo,
B.; Bellot Rubio, L. R.; del Toro Iniesta, J. C.; Solanki, S. K.;
Zuccarello, F.
2019ASPC..526..299G Altcode:
We report on spectropolarimetric observations acquired by the imaging
magnetograph SUNRISE/IMaX at high spatial 0.”3 and temporal (31.5 s)
resolution during the first science flight of this balloon-borne solar
observatory. We describe the photospheric evolution of an exploding
granule observed in the quiet Sun. This granule is cospatial with
a magnetic flux emergence event occurring at mesogranular scales
(up to ∼12 Mm2 area). Using a modified version of the
SIR code, we show that we can estimate the longitudinal field also
in the presence of a residual cross-talk in these IMaX longitudinal
measurements. We determine the magnetic flux content of the structure
(∼3 ×1018 Mx), which appears to have a multipolar
configuration, and discuss the origin of such flux emergence events.

---------------------------------------------------------
Title: Quiet Sun magnetic fields: an observational view
Authors: Bellot Rubio, Luis; Orozco Suárez, David
2019LRSP...16....1B Altcode:
The quiet Sun is the region of the solar surface outside of sunspots,
pores, and plages. In continuum intensity it appears dominated by
granular convection. However, in polarized light the quiet Sun exhibits
impressive magnetic activity on a broad range of scales, from the 30,000
km of supergranular cells down to the smallest magnetic features of
about 100 km resolvable with current instruments. Quiet Sun fields are
observed to evolve in a coherent way, interacting with each other as
they are advected by the horizontal photospheric flows. They appear and
disappear over surprisingly short time scales, bringing large amounts
of magnetic flux to the solar surface. For this reason they may be
important contributors to the heating of the chromosphere. Peering into
such fields is difficult because of the weak signals they produce, which
are easily affected, and even completely hidden, by photon noise. Thus,
their evolution and nature remain largely unknown. In recent years
the situation has improved thanks to the advent of high-resolution,
high-sensitivity spectropolarimetric measurements and the application
of state-of-the-art Zeeman and Hanle effect diagnostics. Here we review
this important aspect of solar magnetism, paying special attention
to the techniques used to observe and characterize the fields,
their evolution on the solar surface, and their physical properties
as revealed by the most recent analyses. We identify the main open
questions that need to be addressed in the future and offer some ideas
on how to solve them.

---------------------------------------------------------
Title: Emergence of internetwork magnetic fields through the solar
atmosphere
Authors: Gosic, Milan; De Pontieu, Bart; Bellot Rubio, L. R.
2018cosp...42E1261G Altcode:
Internetwork (IN) magnetic fields are highly dynamic, short-lived
magnetic structures that populate the interior of supergranular
cells. Since they emerge all over the Sun, these small-scale fields
bring a substantial amount of flux, and therefore energy, to the solar
surface. Because of this, IN fields are crucial for understanding the
quiet Sun magnetism. However, they are weak and produce very small
polarization signals, which is the reason why their properties and
impact on the energetics and dynamics of the solar atmosphere are
largely unknown. Here we use coordinated IRIS and SST observations
of IN regions at high spatial and temporal resolution. They give us
the opportunity to follow the evolution of IN magnetic loops as they
emerge into the photosphere. For the first time, our polarimetric
measurements provide a direct observational evidence of IN fields
reaching the chromosphere. Moreover, we show that IN magnetic loops
contribute to the chromospheric and transition region heating through
interaction with preexisting ambient fields.

---------------------------------------------------------
Title: Transport of Internetwork Magnetic Flux Elements in the Solar
Photosphere : Signatures of Large-Scale Flows and their Effect on
Transport Statistics
Authors: Agrawal, Piyush; Rast, Mark; Gosic, Milan; Rempel, Matthias;
Bellot Rubio, Luis
2018tess.conf21704A Altcode:
The motions of small-scale magnetic &lt;span class="s1" flux elements
in the solar photosphere can provide some measure of the Lagrangian
properties of the convective &lt;span class="s1" flow. Measurements of
these motions have been critical in estimating the turbulent diffusion
coef&lt;span class="s1" ficient in &lt;span class="s1" flux-transport
dynamo models and in determining the Alfvén wave excitation spectrum
for coronal heating models. We examine the motions of internetwork
&lt;span class="s1" flux elements in Hinode&lt;span class="s1"
/Narrowband Filter Imager magnetograms and study the scaling of
their mean squared displacement and the shape of their displacement
probability distribution as a function of time. We &lt;span class="s1"
find that the mean squared displacement scales super-diffusively with
a slope of about 1.48. Super-diffusive scaling has been observed in
other studies for temporal increments as small as 5 s, increments over
which ballistic scaling would be expected. Using high-cadence MURaM
simulations, we show that the observed super-diffusive scaling at short
increments is a consequence of random changes in barycenter positions
due to &lt;span class="s1" flux evolution. We also &lt;span class="s1"
find that for long temporal increments, beyond granular lifetimes,
the observed displacement distribution deviates from that expected
for a diffusive process, evolving from Rayleigh to Gaussian. This
change in distribution can be modeled analytically by accounting for
supergranular advection along with granular motions. These results
complicate the interpretation of magnetic element motions as strictly
advective or diffusive on short and long timescales and suggest that
measurements of magnetic element motions must be used with caution
in turbulent diffusion or wave excitation models. We propose that
passive tracer motions in measured photospheric &lt;span class="s1"
flows may yield more robust transport statistics.

---------------------------------------------------------
Title: Emergence of internetwork magnetic fields through the solar
atmosphere
Authors: Gosic, Milan; De Pontieu, Bart; Bellot Rubio, Luis
2018tess.conf21701G Altcode:
Internetwork (IN) magnetic fields are highly dynamic, short-lived
magnetic structures that populate the interior of supergranular
cells. Since they emerge all over the Sun, these small-scale fields
bring a substantial amount of flux, and therefore energy, to the solar
surface. Because of this, IN fields are crucial for understanding the
quiet Sun magnetism. However, they are weak and produce very small
polarization signals, which is the reason why their properties and
impact on the energetics and dynamics of the solar atmosphere are
largely unknown. Here we use coordinated IRIS and SST observations
of IN regions at high spatial and temporal resolution. They give us
the opportunity to follow the evolution of IN magnetic loops as they
emerge into the photosphere. For the first time, our polarimetric
measurements provide a direct observational evidence of IN fields
reaching the chromosphere. Moreover, we show that IN magnetic loops
contribute to the chromospheric and transition region heating through
interaction with preexisting ambient fields.

---------------------------------------------------------
Title: Chromospheric Heating due to Cancellation of Quiet Sun
Internetwork Fields
Authors: Gošić, M.; de la Cruz Rodríguez, J.; De Pontieu, B.; Bellot
Rubio, L. R.; Carlsson, M.; Esteban Pozuelo, S.; Ortiz, A.; Polito, V.
2018ApJ...857...48G Altcode: 2018arXiv180207392G
The heating of the solar chromosphere remains one of the most
important questions in solar physics. Our current understanding is that
small-scale internetwork (IN) magnetic fields play an important role
as a heating agent. Indeed, cancellations of IN magnetic elements in
the photosphere can produce transient brightenings in the chromosphere
and transition region. These bright structures might be the signature
of energy release and plasma heating, probably driven by the magnetic
reconnection of IN field lines. Although single events are not expected
to release large amounts of energy, their global contribution to the
chromosphere may be significant due to their ubiquitous presence
in quiet Sun regions. In this paper, we study cancellations of IN
elements and analyze their impact on the energetics and dynamics of
the quiet Sun atmosphere. We use high-resolution, multiwavelength,
coordinated observations obtained with the Interface Region Imaging
Spectrograph and the Swedish 1 m Solar Telescope (SST) to identify
cancellations of IN magnetic flux patches and follow their evolution. We
find that, on average, these events live for ∼3 minutes in the
photosphere and ∼12 minutes in the chromosphere and/or transition
region. Employing multi-line inversions of the Mg II h and k lines,
we show that cancellations produce clear signatures of heating in the
upper atmospheric layers. However, at the resolution and sensitivity
accessible to the SST, their number density still seems to be one
order of magnitude too low to explain the global chromospheric heating.

---------------------------------------------------------
Title: Persistent magnetic vortex flow at a supergranular vertex
Authors: Requerey, Iker S.; Cobo, Basilio Ruiz; Gošić, Milan;
Bellot Rubio, Luis R.
2018A&A...610A..84R Altcode: 2017arXiv171201510R
Context. Photospheric vortex flows are thought to play a key role
in the evolution of magnetic fields. Recent studies show that these
swirling motions are ubiquitous in the solar surface convection and
occur in a wide range of temporal and spatial scales. Their interplay
with magnetic fields is poorly characterized, however. Aims:
We study the relation between a persistent photospheric vortex flow
and the evolution of a network magnetic element at a supergranular
vertex. Methods: We used long-duration sequences of continuum
intensity images acquired with Hinode and the local correlation-tracking
method to derive the horizontal photospheric flows. Supergranular
cells are detected as large-scale divergence structures in the flow
maps. At their vertices, and cospatial with network magnetic elements,
the velocity flows converge on a central point. Results: One
of these converging flows is observed as a vortex during the whole
24 h time series. It consists of three consecutive vortices that
appear nearly at the same location. At their core, a network magnetic
element is also detected. Its evolution is strongly correlated to
that of the vortices. The magnetic feature is concentrated and
evacuated when it is caught by the vortices and is weakened and
fragmented after the whirls disappear. Conclusions: This
evolutionary behavior supports the picture presented previously,
where a small flux tube becomes stable when it is surrounded by
a vortex flow. A movie attached to Fig. 2 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201731842/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Occurrence and persistence of magnetic elements in the
quiet Sun
Authors: Giannattasio, F.; Berrilli, F.; Consolini, G.; Del Moro,
D.; Gošić, M.; Bellot Rubio, L.
2018A&A...611A..56G Altcode: 2018arXiv180103871G
Context. Turbulent convection efficiently transports energy up to the
solar photosphere, but its multi-scale nature and dynamic properties
are still not fully understood. Several works in the literature have
investigated the emergence of patterns of convective and magnetic
nature in the quiet Sun at spatial and temporal scales from granular
to global. Aims: To shed light on the scales of organisation
at which turbulent convection operates, and its relationship with
the magnetic flux therein, we studied characteristic spatial and
temporal scales of magnetic features in the quiet Sun. Methods:
Thanks to an unprecedented data set entirely enclosing a supergranule,
occurrence and persistence analysis of magnetogram time series were
used to detect spatial and long-lived temporal correlations in the
quiet Sun and to investigate their nature. Results: A relation
between occurrence and persistence representative for the quiet Sun was
found. In particular, highly recurrent and persistent patterns were
detected especially in the boundary of the supergranular cell. These
are due to moving magnetic elements undergoing motion that behaves
like a random walk together with longer decorrelations ( 2 h) with
respect to regions inside the supergranule. In the vertices of the
supegranular cell the maximum observed occurrence is not associated
with the maximum persistence, suggesting that there are different
dynamic regimes affecting the magnetic elements.

---------------------------------------------------------
Title: Transport of Internetwork Magnetic Flux Elements in the
Solar Photosphere
Authors: Agrawal, Piyush; Rast, Mark P.; Gošić, Milan; Bellot Rubio,
Luis R.; Rempel, Matthias
2018ApJ...854..118A Altcode: 2017arXiv171101290A
The motions of small-scale magnetic flux elements in the solar
photosphere can provide some measure of the Lagrangian properties of
the convective flow. Measurements of these motions have been critical
in estimating the turbulent diffusion coefficient in flux-transport
dynamo models and in determining the Alfvén wave excitation spectrum
for coronal heating models. We examine the motions of internetwork
flux elements in Hinode/Narrowband Filter Imager magnetograms and
study the scaling of their mean squared displacement and the shape of
their displacement probability distribution as a function of time. We
find that the mean squared displacement scales super-diffusively with
a slope of about 1.48. Super-diffusive scaling has been observed in
other studies for temporal increments as small as 5 s, increments
over which ballistic scaling would be expected. Using high-cadence
MURaM simulations, we show that the observed super-diffusive scaling
at short increments is a consequence of random changes in barycenter
positions due to flux evolution. We also find that for long temporal
increments, beyond granular lifetimes, the observed displacement
distribution deviates from that expected for a diffusive process,
evolving from Rayleigh to Gaussian. This change in distribution can be
modeled analytically by accounting for supergranular advection along
with granular motions. These results complicate the interpretation
of magnetic element motions as strictly advective or diffusive on
short and long timescales and suggest that measurements of magnetic
element motions must be used with caution in turbulent diffusion or
wave excitation models. We propose that passive tracer motions in
measured photospheric flows may yield more robust transport statistics.

---------------------------------------------------------
Title: Chromospheric Heating Driven by Cancellations of Internetwork
Magnetic Flux
Authors: Gosic, M.; de la Cruz Rodriguez, J.; De Pontieu, B.; Bellot
Rubio, L.; Esteban Pozuelo, S.; Ortiz-Carbonell, A. N.
2017AGUFMSH41C..02G Altcode:
The heating of the solar chromosphere remains to be one of the
most important questions in solar physics. It is believed that this
phenomenon may significantly be supported by small-scale internetwork
(IN) magnetic fields. Indeed, cancellations of IN magnetic flux can
generate transient brightenings in the chromosphere and transition
region. These bright structures might be the signature of energy release
and plasma heating, probably driven by magnetic reconnection of IN field
lines. Using high resolution, multiwavelength, coordinated observations
recorded with the Interface Region Imaging Spectrograph (IRIS) and
the Swedish 1-m Solar Telescope (SST), we analyzed cancellations of IN
flux and their impact on the energetics and dynamics of the quiet Sun
atmosphere. From their temporal and spatial evolution, we determine that
these events can heat locally the upper atmospheric layers. However,
employing multi-line inversions of the Mg II h &amp; k lines, we show
that cancellations, although occurring ubiquitously over IN regions,
are not capable of sustaining the total radiative losses of the quiet
Sun chromosphere.

---------------------------------------------------------
Title: Chromospheric heating due to internetwork magnetic flux
cancellations
Authors: Gosic, Milan; de la Cruz Rodriguez, Jaime; De Pontieu, Bart;
Bellot Rubio, Luis; Ortiz, Ada; Esteban Pozuelo, Sara
2017SPD....4810404G Altcode:
The heating of the solar chromosphere is one of the most intriguing
unanswered problems in solar physics. It is believed that this
phenomenon may significantly be supported by small-scale internetwork
(IN) magnetic fields. Indeed, cancellations of IN magnetic flux
patches might be an efficient way to transport flux and energy from
the photosphere to the chromosphere. Because of this, it is essential
to determine where they occur, the rates at which they proceed, and
understand their influence on the chromosphere. Here we study the
spatial and temporal evolution of IN cancelling patches using high
resolution, multiwavelength, coordinated observations obtained with
the Interface Region Imaging Spectrograph (IRIS) and the Swedish
1-m Solar Telescope (SST). Employing multi-line inversions of the
Mg II h&amp;k lines we show that cancelling events, while occurring
ubiquitously over IN regions, produce clear signatures of heating in
the upper atmospheric layers. Using the RADYN code we determine the
energy released due to cancellations of IN elements and discuss about
their impact on the dynamics and energetics of the solar chromosphere.

---------------------------------------------------------
Title: Convectively Driven Sinks and Magnetic Fields in the Quiet-Sun
Authors: Requerey, Iker S.; Del Toro Iniesta, Jose Carlos; Bellot
Rubio, Luis R.; Martínez Pillet, Valentín; Solanki, Sami K.;
Schmidt, Wolfgang
2017ApJS..229...14R Altcode: 2016arXiv161007622R
We study the relation between mesogranular flows, convectively
driven sinks and magnetic fields using high spatial resolution
spectropolarimetric data acquired with the Imaging Magnetograph
eXperiment on board Sunrise. We obtain the horizontal velocity
flow fields of two quiet-Sun regions (31.2 × 31.2 Mm2)
via local correlation tracking. Mesogranular lanes and the central
position of sinks are identified using Lagrange tracers. We find
6.7× {10}-2 sinks per Mm2 in the two observed
regions. The sinks are located at the mesogranular vertices and turn
out to be associated with (1) horizontal velocity flows converging to a
central point and (2) long-lived downdrafts. The spatial distribution
of magnetic fields in the quiet-Sun is also examined. The strongest
magnetic fields are preferentially located at sinks. We find that 40% of
the pixels with longitudinal components of the magnetic field stronger
than 500 G are located in the close neighborhood of sinks. In contrast,
the small-scale magnetic loops detected by Martínez González et al. in
the same two observed areas do not show any preferential distribution
at mesogranular scales. The study of individual examples reveals
that sinks can play an important role in the evolution of quiet-Sun
magnetic features.

---------------------------------------------------------
Title: Properties of Supersonic Evershed Downflows
Authors: Pozuelo, S. Esteban; Bellot Rubio, L. R.; de la Cruz
Rodríguez, J.
2016ApJ...832..170P Altcode: 2016ApJ...832..170E; 2016arXiv160901106E
We study supersonic Evershed downflows in a sunspot penumbra by means
of high spatial resolution spectropolarimetric data acquired in the
Fe I 617.3 nm line with the CRISP instrument at the Swedish 1 m Solar
Telescope. Physical observables, such as Dopplergrams calculated from
line bisectors and Stokes V zero-crossing wavelengths, and Stokes V
maps in the far red-wing, are used to find regions where supersonic
Evershed downflows may exist. We retrieve the line-of-sight velocity
and the magnetic field vector in these regions using two-component
inversions of the observed Stokes profiles with the help of the SIR
code. We follow these regions during their lifetime to study their
temporal behavior. Finally, we carry out a statistical analysis
of the detected supersonic downflows to characterize their physical
properties. Supersonic downflows are contained in compact patches moving
outward, which are located in the mid- and outer penumbra. They are
observed as bright, roundish structures at the outer end of penumbral
filaments that resemble penumbral grains. The patches may undergo
fragmentations and mergings during their lifetime; some of them are
recurrent. Supersonic downflows are associated with strong and rather
vertical magnetic fields with a reversed polarity compared to that of
the sunspot. Our results suggest that downflows returning back to the
solar surface with supersonic velocities are abruptly stopped in dense
deep layers and produce a shock. Consequently, this shock enhances
the temperature and is detected as a bright grain in the continuum
filtergrams, which could explain the existence of outward-moving grains
in the mid- and outer penumbra.

---------------------------------------------------------
Title: A study on Ca II 854.2 nm emission in a sunspot umbra using
a thin cloud model
Authors: Hamedivafa, H.; Sobotka, M.; Bellot Rubio, L.; Esteban
Pozuelo, S.
2016arXiv161206636H Altcode:
In the present work, we introduce and explain a method of solution
of the radiative transfer equation based on a thin cloud model. The
efficiency of this method to retrieve dynamical chromospheric parameters
from Stokes I profiles of Ca II 854.2 nm line showing spectral emission
is investigated. The analyzed data were recorded with the Crisp
Imaging Spectro-Polarimeter (CRISP) at Swedish 1-m Solar Telescope
on La Palma on 2012 May 5 between 8:11 - 9:00 UT. The target was a
large decaying sunspot (NOAA 11471) at heliocentric position W 15
deg S 19 deg. This sunspot has a large umbra divided into two umbral
cores (UCs). One of these UCs shows steady spectral emission in both
Ca II 854.2 nm and H-alpha lines, where downflows prevail. The other
UC shows intermittent spectral emission only in Ca II 854.2 nm, when
umbral flashes are propagating. The statistics of the obtained Doppler
velocities in both UCs is discussed.

---------------------------------------------------------
Title: Emergence of Granular-sized Magnetic Bubbles Through the
Solar Atmosphere. III. The Path to the Transition Region
Authors: Ortiz, Ada; Hansteen, Viggo H.; Bellot Rubio, Luis Ramón;
de la Cruz Rodríguez, Jaime; De Pontieu, Bart; Carlsson, Mats;
Rouppe van der Voort, Luc
2016ApJ...825...93O Altcode: 2016arXiv160400302O
We study, for the first time, the ascent of granular-sized magnetic
bubbles from the solar photosphere through the chromosphere into the
transition region and above. Such events occurred in a flux emerging
region in NOAA 11850 on 2013 September 25. During that time, the
first co-observing campaign between the Swedish 1-m Solar Telescope
(SST) and the Interface Region Imaging Spectrograph (IRIS) spacecraft
was carried out. Simultaneous observations of the chromospheric Hα
656.28 nm and Ca II 854.2 nm lines, plus the photospheric Fe I 630.25
nm line, were made with the CRISP spectropolarimeter at the Spitzer
Space Telescope (SST) reaching a spatial resolution of 0.″14. At
the same time, IRIS was performing a four-step dense raster of the
emerging flux region, taking slit jaw images at 133 (C II, transition
region), 140 (Si IV, transition region), 279.6 (Mg II k, core, upper
chromosphere), and 283.2 nm (Mg II k, wing, photosphere). Spectroscopy
of several lines was performed by the IRIS spectrograph in the far-
and near-ultraviolet, of which we have used the Si IV 140.3 and the
Mg II k 279.6 nm lines. Coronal images from the Atmospheric Imaging
Assembly of the Solar Dynamics Observatory were used to investigate
the possible coronal signatures of the flux emergence events. The
photospheric and chromospheric properties of small-scale emerging
magnetic bubbles have been described in detail in Ortiz et al. Here
we are able to follow such structures up to the transition region. We
describe the properties, including temporal delays, of the observed
flux emergence in all layers. We believe this may be an important
mechanism of transporting energy and magnetic flux from subsurface
layers to the transition region and corona.

---------------------------------------------------------
Title: Turbulent transport of Small-scale magnetic flux elements on
Solar Photosphere
Authors: Agrawal, Piyush; Rempel, Matthias; Bellot Rubio, Luis;
Rast, Mark
2016SPD....47.1201A Altcode:
We study the transport of small-scale magnetic elements on the solar
photosphere using both observations and simulations. Observational
data was obtained from Hinode - Solar Optical Telescope (SOT/SP)
instrument and simulations from MURaM code. The magnetic flux elements
were tracked in both data sets and statistics were obtained. We compute
the probability density of the Eulerian distances traveled by the flux
elements along Lagrangian trajectories. For a two-dimensional random
walk process this distribution should be Rayleigh. Preliminary results
show that the measured probability distribution in both the observed
and simulated data approximates a random walk, on time scale close to
the lifetime of granules, but deviates from it for longer times. This
implies that diffusion may not be an appropriate framework for transport
in the solar photosphere. We explore the roles of flux cancelation
and element trapping in producing this result. Work is ongoing.

---------------------------------------------------------
Title: Flux appearance and disappearance rates in the solar
internetwork
Authors: Gosic, Milan; Bellot Rubio, Luis; Del Toro Iniesta, Jose
Carlos; Orozco Suarez, David; Katsukawa, Yukio
2016SPD....4740105G Altcode:
The solar internetwork contains weak and highly dynamic magnetic
fields that are essential to understanding the solar magnetism at small
spatial and temporal scales. Therefore, it is important to determine
how these fields are maintained on the solar surface. Using unique
Hinode observations, we follow the evolution of individual magnetic
elements in the interior of two supergranular cells at the disk
center. From up to 38 hr of continuous measurements, we show that
magnetic flux appears in internetwork regions at a rate of 120±3
Mx cm-2 day-1 (3.7±0.4 × 1024 Mx
day-1 over the entire solar surface). Flux disappears from
the internetwork at a rate of 125±6 Mx cm-2 day-1
(3.9±0.5 × 1024 Mx day-1) through fading of
magnetic elements, cancellation between opposite-polarity features,
and interactions with network patches, which converts internetwork
elements into network features. The removal of flux from supergranules
occurs mainly through fading and interactions with network, at nearly
the same rate of about 50 Mx cm-2 day-1. Our
results demonstrate that the sources and sinks of internetwork magnetic
flux are well balanced, reflecting the steady-state nature of the quiet
Sun. Using the instantaneous flux appearance and disappearance rates,
we successfully reproduce, for the first time, the temporal evolution
of the total unsigned flux in the interior of supergranular cells.

---------------------------------------------------------
Title: The Solar Internetwork. II. Flux Appearance and Disappearance
Rates
Authors: Gošić, M.; Bellot Rubio, L. R.; del Toro Iniesta, J. C.;
Orozco Suárez, D.; Katsukawa, Y.
2016ApJ...820...35G Altcode: 2016arXiv160205892G
Small-scale internetwork magnetic fields are important ingredients of
the quiet Sun. In this paper we analyze how they appear and disappear
on the solar surface. Using high resolution Hinode magnetograms,
we follow the evolution of individual magnetic elements in the
interior of two supergranular cells at the disk center. From up to
38 hr of continuous measurements, we show that magnetic flux appears
in internetwork regions at a rate of 120 ± 3 Mx cm-2
day-1 (3.7 ± 0.4 × 1024 Mx day-1
over the entire solar surface). Flux disappears from the internetwork
at a rate of 125 ± 6 Mx cm-2 day-1 (3.9
± 0.5 × 1024 Mx day-1) through fading of
magnetic elements, cancelation between opposite-polarity features,
and interactions with network patches, which converts internetwork
elements into network features. Most of the flux is lost through
fading and interactions with the network, at nearly the same rate of
about 50 Mx cm-2 day-1. Our results demonstrate
that the sources and sinks of internetwork magnetic flux are well
balanced. Using the instantaneous flux appearance and disappearance
rates, we successfully reproduce the time evolution of the total
unsigned flux in the two supergranular cells.

---------------------------------------------------------
Title: Small-scale magnetic flux emergence in a sunspot light bridge
Authors: Louis, Rohan E.; Bellot Rubio, Luis R.; de la Cruz Rodríguez,
Jaime; Socas-Navarro, Héctor; Ortiz, Ada
2015A&A...584A...1L Altcode: 2015arXiv150900741L
Context. Light bridges are convective intrusions in sunspots that
often show enhanced chromospheric activity. Aims: We seek
to determine the nature of flux emergence in a light bridge and the
processes related to its evolution in the solar atmosphere. 
Methods: We analyse a sequence of high-resolution spectropolarimetric
observations of a sunspot taken at the Swedish 1-m Solar Telescope. The
data consist of spectral scans of the photospheric Fe i line pair at
630 nm and the chromospheric Ca ii 854.2 nm line. Bisectors were used
to construct Dopplergrams from the Fe i 630.15 nm measurements. We
employed LTE and non-LTE inversions to derive maps of physical
parameters in the photosphere and chromosphere, respectively. 
Results: We observe the onset of blueshifts of about 2 km s-1
near the entrance of a granular light bridge on the limbward side of
the spot. The blueshifts lie immediately next to a strongly redshifted
patch that appeared six minutes earlier. Both patches can be seen for
25 min until the end of the sequence. The blueshifts coincide with
an elongated emerging granule, while the redshifts appear at the end
of the granule. In the photosphere, the development of the blueshifts
is accompanied by a simultaneous increase in field strength of about
400 G. The field inclination increases by some 25°, becoming nearly
horizontal. At the position of the redshifts, the magnetic field is
equally horizontal but of opposite polarity. An intense brightening
is seen in the Ca ii filtergrams over the blueshifts and redshifts,
about 17 min after their detection in the photosphere. The brightening
is due to emission in the blue wing of the Ca ii 854.2 nm line, close
to its knee. Non-LTE inversions reveal that this kind of asymmetric
emission is caused by a temperature enhancement of ~700 K between -5.0
≤ log τ ≤ -3.0 and a blueshift of 3 km s-1 at log τ
= -2.3 that decreases to zero at log τ = -6.0 Conclusions:
The photospheric blueshifts and redshifts observed in a granular
light bridge seem to be caused by the emergence of a small-scale,
flat Ω-loop with highly inclined footpoints of opposite polarity that
brings new magnetic field to the surface. The gas motions detected in
the two footpoints are reminiscent of a siphon flow. The rising loop
is probably confined to the lower atmosphere by the overlying sunspot
magnetic field and the interaction between the two flux systems may be
responsible for temperature enhancements in the upper photosphere/lower
chromosphere. This is the first time that magnetic flux is observed
to emerge in the strongly magnetised environment of sunspots, pushed
upwards by the convective flows of a granular light bridge. The
movie associated to Fig. 2 is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201526854/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: ADAHELI: exploring the fast, dynamic Sun in the x-ray, optical,
and near-infrared
Authors: Berrilli, Francesco; Soffitta, Paolo; Velli, Marco; Sabatini,
Paolo; Bigazzi, Alberto; Bellazzini, Ronaldo; Bellot Rubio, Luis
Ramon; Brez, Alessandro; Carbone, Vincenzo; Cauzzi, Gianna; Cavallini,
Fabio; Consolini, Giuseppe; Curti, Fabio; Del Moro, Dario; Di Giorgio,
Anna Maria; Ermolli, Ilaria; Fabiani, Sergio; Faurobert, Marianne;
Feller, Alex; Galsgaard, Klaus; Gburek, Szymon; Giannattasio, Fabio;
Giovannelli, Luca; Hirzberger, Johann; Jefferies, Stuart M.; Madjarska,
Maria S.; Manni, Fabio; Mazzoni, Alessandro; Muleri, Fabio; Penza,
Valentina; Peres, Giovanni; Piazzesi, Roberto; Pieralli, Francesca;
Pietropaolo, Ermanno; Martinez Pillet, Valentin; Pinchera, Michele;
Reale, Fabio; Romano, Paolo; Romoli, Andrea; Romoli, Marco; Rubini,
Alda; Rudawy, Pawel; Sandri, Paolo; Scardigli, Stefano; Spandre,
Gloria; Solanki, Sami K.; Stangalini, Marco; Vecchio, Antonio;
Zuccarello, Francesca
2015JATIS...1d4006B Altcode:
Advanced Astronomy for Heliophysics Plus (ADAHELI) is a project concept
for a small solar and space weather mission with a budget compatible
with an European Space Agency (ESA) S-class mission, including launch,
and a fast development cycle. ADAHELI was submitted to the European
Space Agency by a European-wide consortium of solar physics research
institutes in response to the "Call for a small mission opportunity
for a launch in 2017," of March 9, 2012. The ADAHELI project builds
on the heritage of the former ADAHELI mission, which had successfully
completed its phase-A study under the Italian Space Agency 2007 Small
Mission Programme, thus proving the soundness and feasibility of
its innovative low-budget design. ADAHELI is a solar space mission
with two main instruments: ISODY: an imager, based on Fabry-Pérot
interferometers, whose design is optimized to the acquisition of
highest cadence, long-duration, multiline spectropolarimetric images
in the visible/near-infrared region of the solar spectrum. XSPO: an
x-ray polarimeter for solar flares in x-rays with energies in the 15
to 35 keV range. ADAHELI is capable of performing observations that
cannot be addressed by other currently planned solar space missions,
due to their limited telemetry, or by ground-based facilities, due to
the problematic effect of the terrestrial atmosphere.

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Title: Parallelization of the SIR code for the investigation of
small-scale features in the solar photosphere
Authors: Thonhofer, Stefan; Bellot Rubio, Luis R.; Utz, Dominik;
Hanslmeier, Arnold; Jurçák, Jan
2015IAUS..305..251T Altcode: 2015arXiv150303710T
Magnetic fields are one of the most important drivers of the highly
dynamic processes that occur in the lower solar atmosphere. They span a
broad range of sizes, from large- and intermediate-scale structures such
as sunspots, pores and magnetic knots, down to the smallest magnetic
elements observable with current telescopes. On small scales, magnetic
flux tubes are often visible as Magnetic Bright Points (MBPs). Apart
from simple V/I magnetograms, the most common method to deduce their
magnetic properties is the inversion of spectropolarimetric data. Here
we employ the SIR code for that purpose. SIR is a well-established
tool that can derive not only the magnetic field vector and other
atmospheric parameters (e.g., temperature, line-of-sight velocity),
but also their stratifications with height, effectively producing
3-dimensional models of the lower solar atmosphere. In order to enhance
the runtime performance and the usability of SIR we parallelized the
existing code and standardized the input and output formats. This and
other improvements make it feasible to invert extensive high-resolution
data sets within a reasonable amount of computing time. An evaluation
of the speedup of the parallel SIR code shows a substantial improvement
in runtime.

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Title: Dynamics of Multi-cored Magnetic Structures in the Quiet Sun
Authors: Requerey, Iker S.; Del Toro Iniesta, Jose Carlos; Bellot
Rubio, Luis R.; Martínez Pillet, Valentín; Solanki, Sami K.;
Schmidt, Wolfgang
2015ApJ...810...79R Altcode: 2015arXiv150806998R
We report on the dynamical interaction of quiet-Sun magnetic fields and
granular convection in the solar photosphere as seen by Sunrise. We
use high spatial resolution (0.″15-0.″18) and temporal cadence
(33 s) spectropolarimetric Imaging Magnetograph eXperiment data,
together with simultaneous CN and Ca ii H filtergrams from Sunrise
Filter Imager. We apply the SIR inversion code to the polarimetric
data in order to infer the line of sight velocity and vector magnetic
field in the photosphere. The analysis reveals bundles of individual
flux tubes evolving as a single entity during the entire 23 minute data
set. The group shares a common canopy in the upper photospheric layers,
while the individual tubes continually intensify, fragment and merge in
the same way that chains of bright points in photometric observations
have been reported to do. The evolution of the tube cores are driven
by the local granular convection flows. They intensify when they
are “compressed” by surrounding granules and split when they are
“squeezed” between two moving granules. The resulting fragments
are usually later regrouped in intergranular lanes by the granular
flows. The continual intensification, fragmentation and coalescence of
flux results in magnetic field oscillations of the global entity. From
the observations we conclude that the magnetic field oscillations first
reported by Martínez González et al. correspond to the forcing by
granular motions and not to characteristic oscillatory modes of thin
flux tubes.

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Title: Emergence of Granular-sized Magnetic Bubbles through the
Solar Atmosphere. II. Non-LTE Chromospheric Diagnostics and Inversions
Authors: de la Cruz Rodríguez, Jaime; Hansteen, Viggo; Bellot-Rubio,
Luis; Ortiz, Ada
2015ApJ...810..145D Altcode: 2015arXiv150303846D
Magnetic flux emergence into the outer layers of the Sun is a
fundamental mechanism for releasing energy into the chromosphere and
the corona. In this paper, we study the emergence of granular-sized
flux concentrations and the structuring of the corresponding physical
parameters and atmospheric diagnostics in the upper photosphere and
in the chromosphere. We make use of a realistic 3D MHD simulation of
the outer layers of the Sun to study the formation of the Ca ii 8542
line. We also derive semi-empirical 3D models from non-LTE inversions of
our observations. These models contain information on the line-of-sight
stratifications of temperature, velocity, and the magnetic field. Our
analysis explains the peculiar Ca ii 8542 Å profiles observed in the
flux emerging region. Additionally, we derive detailed temperature
and velocity maps describing the ascent of a magnetic bubble from the
photosphere to the chromosphere. The inversions suggest that, in active
regions, granular-sized bubbles emerge up to the lower chromosphere
where the existing large-scale field hinders their ascent. We report
hints of heating when the field reaches the chromosphere.

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Title: Magnetic bright point dynamics and evolutions observed by
Sunrise/IMaX and other instruments
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L.; Thonhofer,
S.; Jurčák, J.
2015hsa8.conf..689U Altcode:
In this proceeding we will have a closer look on recent observations
and results regarding the dynamics and evolution of so-called magnetic
bright points (MBPs). MBPs are manifestations of kG magnetic field
strong flux concentrations seen in the solar photosphere. They belong
to the class of small-scale solar magnetic features with diameters
starting from low values around the current observational resolution
limit - about 100 km - up to a few hundred km. They might play an
important role in several key research questions like the total solar
irradiance variation (TSI variation) as well as the solar atmospheric
heating problem. Especially their dynamic behaviour is of interest
for the heating problem as they might trigger all kinds of MHD waves
which travel up to the higher solar atmospheric layers, where they can
get damped leading to a heating of the plasma. Furthermore they might
engage in magnetic field reconnection processes leading consequently
also to a heating. Due to these reasons, and also for the sake of a
better understanding of the physical processes involved on small-scales,
detailed investigations on the dynamical behaviour and evolution of
such magnetic field proxies like MBPs is in order. In this conference
proceeding we wish to give in a first part an overview about the
obtained knowledge so far. In a second part we highlight recent results
regarding the dynamical evolution of plasma parameters of MBPs such as
magnetic field strength, temperature, and line of sight velocity. This
proceeding is completed by an outlook on what can and should be done
in the near future with available data from recent telescopes.

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Title: Lateral Downflows in Sunspot Penumbral Filaments and their
Temporal Evolution
Authors: Esteban Pozuelo, S.; Bellot Rubio, L. R.; de la Cruz
Rodríguez, J.
2015ApJ...803...93E Altcode: 2015arXiv150202981E
We study the temporal evolution of downflows observed at the lateral
edges of penumbral filaments in a sunspot located very close to
the disk center. Our analysis is based on a sequence of nearly
diffraction-limited scans of the Fe i 617.3 nm line taken with the
CRisp Imaging Spectro-Polarimeter instrument at the Swedish 1 m
Solar Telescope. We compute Dopplergrams from the observed intensity
profiles using line bisectors and filter the resulting velocity maps
for subsonic oscillations. Lateral downflows appear everywhere in
the center-side penumbra as small, weak patches of redshifts next to
or along the edges of blueshifted flow channels. These patches have
an intermittent life and undergo mergings and fragmentations quite
frequently. The lateral downflows move together with the hosting
filaments and react to their shape variations, very much resembling
the evolution of granular convection in the quiet Sun. There is a
good relation between brightness and velocity in the center-side
penumbra, with downflows being darker than upflows on average, which
is again reminiscent of quiet Sun convection. These results point to
the existence of overturning convection in sunspot penumbrae, with
elongated cells forming filaments where the flow is upward but very
inclined, and weak lateral downward flows. In general, the circular
polarization profiles emerging from the lateral downflows do not show
sign reversals, although sometimes we detect three-lobed profiles that
are suggestive of opposite magnetic polarities in the pixel.

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Title: Long time variations of Magnetic Bright Points observed
by Hinode/SOT
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot-Rubio, L.;
Bodnárová, M.; Muller, R.; Bárta, M.; Thonhofer, S.; Hanslmeier, A.
2015CEAB...39...91U Altcode:
Magnetic bright points (MBPs) are manifestations of small-scale solar
magnetic flux concentrations, best observable due to their high contrast
in molecular bands like the G-band. Moreover, they are among the most
interesting magnetic features to be studied in high spatial and temporal
resolution in the solar photosphere. Their relevance for solar physics
is not only given by their contribution to fundamental solar plasma
physics on small scales but in addition due to their involvement in
processes like the solar atmospheric heating problem (chromosphere
and corona), their influence on granulation and hence the convective
energy transport, as well as their contribution to the variations in
total solar irradiance caused by their higher relative intensity. In
this ongoing study we focus on the long-time evolution of statistical
parameters of MBPs over the solar cycle. Are parameters like the mean
intensity, average size/diameter, and number of MBPs per unit surface
element variable with time? If so, how do these parameters vary and is
there a relationship to the solar cycle? In the actual contribution
we will discuss preliminary results regarding the variation of the
number of MBPs with time. We saw a decrease in the number of MBPs for
the first years of observation (2006 until 2011) with two distinct
local minima in the years 2009 and 2011. After 2011 the number of MBPs
is increasing again along with an increase in general solar activity
(as seen by the number of sunspots, flares, and CMEs).

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Title: The Formation and Disintegration of Magnetic Bright Points
Observed by Sunrise/IMaX
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.;
Jurčák, J.; Martínez Pillet, V.; Solanki, S. K.; Schmidt, W.
2014ApJ...796...79U Altcode: 2014arXiv1411.3240U
The evolution of the physical parameters of magnetic bright points
(MBPs) located in the quiet Sun (mainly in the interwork) during
their lifetime is studied. First, we concentrate on the detailed
description of the magnetic field evolution of three MBPs. This
reveals that individual features follow different, generally complex,
and rather dynamic scenarios of evolution. Next, we apply statistical
methods on roughly 200 observed MBP evolutionary tracks. MBPs are found
to be formed by the strengthening of an equipartition field patch,
which initially exhibits a moderate downflow. During the evolution,
strong downdrafts with an average velocity of 2.4 km s-1
set in. These flows, taken together with the concurrent strengthening of
the field, suggest that we are witnessing the occurrence of convective
collapses in these features, although only 30% of them reach kG field
strengths. This fraction might turn out to be larger when the new 4
m class solar telescopes are operational as observations of MBPs with
current state of the art instrumentation could still be suffering from
resolution limitations. Finally, when the bright point disappears
(although the magnetic field often continues to exist) the magnetic
field strength has dropped to the equipartition level and is generally
somewhat weaker than at the beginning of the MBP's evolution. Also,
only relatively weak downflows are found on average at this stage of
the evolution. Only 16% of the features display upflows at the time
that the field weakens, or the MBP disappears. This speaks either for
a very fast evolving dynamic process at the end of the lifetime, which
could not be temporally resolved, or against strong upflows as the cause
of the weakening of the field of these magnetic elements, as has been
proposed based on simulation results. It is noteworthy that in about 10%
of the cases, we observe in the vicinity of the downflows small-scale
strong (exceeding 2 km s-1) intergranular upflows related
spatially and temporally to these downflows. The paper is complemented
by a detailed discussion of aspects regarding the applied methods,
the complementary literature, and in depth analysis of parameters
like magnetic field strength and velocity distributions. An important
difference to magnetic elements and associated bright structures in
active region plage is that most of the quiet Sun bright points display
significant downflows over a large fraction of their lifetime (i.e.,
in more than 46% of time instances/measurements they show downflows
exceeding 1 km s-1).

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Title: The Solar Internetwork. I. Contribution to the Network
Magnetic Flux
Authors: Gošić, M.; Bellot Rubio, L. R.; Orozco Suárez, D.;
Katsukawa, Y.; del Toro Iniesta, J. C.
2014ApJ...797...49G Altcode: 2014arXiv1408.2369G
The magnetic network (NE) observed on the solar surface harbors a
sizable fraction of the total quiet Sun flux. However, its origin and
maintenance are not well known. Here we investigate the contribution
of internetwork (IN) magnetic fields to the NE flux. IN fields permeate
the interior of supergranular cells and show large emergence rates. We
use long-duration sequences of magnetograms acquired by Hinode and
an automatic feature tracking algorithm to follow the evolution of NE
and IN flux elements. We find that 14% of the quiet Sun (QS) flux is
in the form of IN fields with little temporal variations. IN elements
interact with NE patches and modify the flux budget of the NE either
by adding flux (through merging processes) or by removing it (through
cancellation events). Mergings appear to be dominant, so the net flux
contribution of the IN is positive. The observed rate of flux transfer
to the NE is 1.5 × 1024 Mx day-1 over the entire
solar surface. Thus, the IN supplies as much flux as is present in the
NE in only 9-13 hr. Taking into account that not all the transferred
flux is incorporated into the NE, we find that the IN would be able
to replace the entire NE flux in approximately 18-24 hr. This renders
the IN the most important contributor to the NE, challenging the view
that ephemeral regions are the main source of flux in the QS. About 40%
of the total IN flux eventually ends up in the NE.

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Title: Pair separation of magnetic elements in the quiet Sun
Authors: Giannattasio, F.; Berrilli, F.; Biferale, L.; Del Moro, D.;
Sbragaglia, M.; Bellot Rubio, L.; Gošić, M.; Orozco Suárez, D.
2014A&A...569A.121G Altcode: 2014arXiv1409.1010G
The dynamic properties of the quiet Sun photosphere can be investigated
by analyzing the pair dispersion of small-scale magnetic fields
(i.e., magnetic elements). By using 25 h-long Hinode magnetograms
at high spatial resolution (0.3 arcsec), we tracked 68 490 magnetic
element pairs within a supergranular cell near the disk center. The
computed pair separation spectrum, calculated on the whole set of
particle pairs independently of their initial separation, points
out what is known as a super-diffusive regime with spectral index
γ = 1.55 ± 0.05, in agreement with the most recent literature, but
extended to unprecedented spatial and temporal scales (from granular
to supergranular). Furthermore, for the first time, we investigated
here the spectrum of the mean square displacement of pairs of magnetic
elements, depending on their initial separation r0. We found
that there is a typical initial distance above (below) which the pair
separation is faster (slower) than the average. A possible physical
interpretation of such a typical spatial scale is also provided.

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Title: Inclinations of small quiet-Sun magnetic features based on
a new geometric approach
Authors: Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; Bellot Rubio,
L. R.; van Noort, M.; Feller, A.; Danilovic, S.
2014A&A...569A.105J Altcode: 2014arXiv1408.2443J
Context. High levels of horizontal magnetic flux have been reported
in the quiet-Sun internetwork, often based on Stokes profile
inversions. Aims: Here we introduce a new method for deducing
the inclination of magnetic elements and use it to test magnetic field
inclinations from inversions. Methods: We determine accurate
positions of a set of small, bright magnetic elements in high spatial
resolution images sampling different photospheric heights obtained by
the Sunrise balloon-borne solar observatory. Together with estimates
of the formation heights of the employed spectral bands, these provide
us with the inclinations of the magnetic features. We also compute
the magnetic inclination angle of the same magnetic features from the
inversion of simultaneously recorded Stokes parameters. Results:
Our new, geometric method returns nearly vertical fields (average
inclination of around 14° with a relatively narrow distribution
having a standard deviation of 6°). In strong contrast to this, the
traditionally used inversions give almost horizontal fields (average
inclination of 75 ± 8°) for the same small magnetic features,
whose linearly polarised Stokes profiles are adversely affected by
noise. We show that for such magnetic features inversions overestimate
the flux in horizontal magnetic fields by an order of magnitude. 
Conclusions: The almost vertical field of bright magnetic features from
our geometric method is clearly incompatible with the nearly horizontal
magnetic fields obtained from the inversions. This indicates that the
amount of magnetic flux in horizontal fields deduced from inversions is
overestimated in the presence of weak Stokes signals, in particular if
Stokes Q and U are close to or under the noise level. Inversions should
be used with great caution when applied to data with no clear Stokes Q
and no U signal. By combining the proposed method with inversions we are
not just improving the inclination, but also the field strength. This
technique allows us to analyse features that are not reliably treated
by inversions, thus greatly extending our capability to study the
complete magnetic field of the quiet Sun.

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Title: The History of a Quiet-Sun Magnetic Element Revealed by
IMaX/SUNRISE
Authors: Requerey, Iker S.; Del Toro Iniesta, Jose Carlos; Bellot
Rubio, Luis R.; Bonet, José A.; Martínez Pillet, Valentín; Solanki,
Sami K.; Schmidt, Wolfgang
2014ApJ...789....6R Altcode: 2014arXiv1405.2837R
Isolated flux tubes are considered to be fundamental magnetic building
blocks of the solar photosphere. Their formation is usually attributed
to the concentration of magnetic field to kG strengths by the convective
collapse mechanism. However, the small size of the magnetic elements in
quiet-Sun areas has prevented this scenario from being studied in fully
resolved structures. Here, we report on the formation and subsequent
evolution of one such photospheric magnetic flux tube, observed in
the quiet Sun with unprecedented spatial resolution (0.”15-0.”18)
and high temporal cadence (33 s). The observations were acquired by
the Imaging Magnetograph eXperiment on board the SUNRISE balloon-borne
solar observatory. The equipartition field strength magnetic element
is the result of the merging of several same polarity magnetic flux
patches, including a footpoint of a previously emerged loop. The
magnetic structure is then further intensified to kG field strengths
by convective collapse. The fine structure found within the flux
concentration reveals that the scenario is more complex than can be
described by a thin flux tube model with bright points and downflow
plumes being established near the edges of the kG magnetic feature. We
also observe a daisy-like alignment of surrounding granules and a
long-lived inflow toward the magnetic feature. After a subsequent
weakening process, the field is again intensified to kG strengths. The
area of the magnetic feature is seen to change in anti-phase with the
field strength, while the brightness of the bright points and the speed
of the downflows varies in phase. We also find a relation between the
brightness of the bright point and the presence of upflows within it.

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Title: Diffusion of Magnetic Elements in a Supergranular Cell
Authors: Giannattasio, F.; Stangalini, M.; Berrilli, F.; Del Moro,
D.; Bellot Rubio, L.
2014ApJ...788..137G Altcode: 2014arXiv1405.0677G
Small scale magnetic fields (magnetic elements) are ubiquitous in the
solar photosphere. Their interaction can provide energy to the upper
atmospheric layers, and contribute to heat the solar corona. In this
work, the dynamic properties of magnetic elements in the quiet Sun
are investigated. The high number of magnetic elements detected in a
supergranular cell allowed us to compute their displacement spectrum
lang(Δr)2rangvpropτγ (with γ &gt; 0, and τ
the time since the first detection), separating the contribution of
the network (NW) and the internetwork (IN) regions. In particular,
we found γ = 1.27 ± 0.05 and γ = 1.08 ± 0.11 in NW (at smaller
and larger scales, respectively), and γ = 1.44 ± 0.08 in IN. These
results are discussed in light of the literature on the topic, as well
as the implications for the build-up of the magnetic network.

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Title: Orphan penumbrae: Submerging horizontal fields
Authors: Jurčák, J.; Bellot Rubio, L. R.; Sobotka, M.
2014A&A...564A..91J Altcode: 2014arXiv1402.6558J
 Aims: We investigate the properties of orphan penumbrae,
which are photospheric filamentary structures observed in active
regions near polarity inversion lines that resemble the penumbra of
regular sunspots but are not connected to any umbra. Methods:
We use Hinode data from the Solar Optical Telescope to determine the
properties of orphan penumbrae. Spectropolarimetric data are employed
to obtain the vector magnetic field and line-of-sight velocities in
the photosphere. Magnetograms are used to study the overall evolution
of these structures, and G-band and Ca ii H filtergrams are to
investigate their brightness and apparent horizontal motions. 
Results: Orphan penumbrae form between regions of opposite polarity in
places with horizontal magnetic fields. Their magnetic configuration
is that of Ω-shaped flux ropes. In the two cases studied here,
the opposite-polarity regions approach each other with time and the
whole structure submerges as the penumbral filaments disappear. Orphan
penumbrae are very similar to regular penumbrae, including the existence
of strong gas flows. Therefore, they could have a similar origin. The
main difference between them is the absence of a "background" magnetic
field in orphan penumbrae. This could explain most of the observed
differences. Conclusions: The fast flows we detect in orphan
penumbrae may be caused by the siphon flow mechanism. Based on the
similarities between orphan and regular penumbrae, we propose that
the Evershed flow is also a manifestation of siphon flows. A
movie attached to Fig. 11 is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322340/olm">http://www.aanda.org</A>

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Title: Emergence of Granular-sized Magnetic Bubbles through the
Solar Atmosphere. I. Spectropolarimetric Observations and Simulations
Authors: Ortiz, Ada; Bellot Rubio, Luis R.; Hansteen, Viggo H.;
de la Cruz Rodríguez, Jaime; Rouppe van der Voort, Luc
2014ApJ...781..126O Altcode: 2013arXiv1312.5735O
We study a granular-sized magnetic flux emergence event that occurred
in NOAA 11024 in 2009 July. The observations were made with the CRISP
spectropolarimeter at the Swedish 1 m Solar Telescope achieving a
spatial resolution of 0.”14. Simultaneous full Stokes observations of
the two photospheric Fe I lines at 630.2 nm and the chromospheric Ca
II 854.2 nm line allow us to describe in detail the emergence process
across the solar atmosphere. We report here on three-dimensional
(3D) semi-spherical bubble events, where instead of simple magnetic
footpoints, we observe complex semi-circular feet straddling a few
granules. Several phenomena occur simultaneously, namely, abnormal
granulation, separation of opposite-polarity legs, and brightenings at
chromospheric heights. However, the most characteristic signature in
these events is the observation of a dark bubble in filtergrams taken
in the wings of the Ca II 854.2 nm line. There is a clear coincidence
between the emergence of horizontal magnetic field patches and the
formation of the dark bubble. We can infer how the bubble rises through
the solar atmosphere as we see it progressing from the wings to the
core of Ca II 854.2 nm. In the photosphere, the magnetic bubble shows
mean upward Doppler velocities of 2 km s-1 and expands at a
horizontal speed of 4 km s-1. In about 3.5 minutes it travels
some 1100 km to reach the mid chromosphere, implying an average ascent
speed of 5.2 km s-1. The maximum separation attained by the
magnetic legs is 6.”6. From an inversion of the observed Stokes spectra
with the SIR code, we find maximum photospheric field strengths of 480 G
and inclinations of nearly 90° in the magnetic bubble interior, along
with temperature deficits of up to 250 K at log τ = -2 and above. To
aid the interpretation of the observations, we carry out 3D numerical
simulations of the evolution of a horizontal, untwisted magnetic flux
sheet injected in the convection zone, using the Bifrost code. The
computational domain spans from the upper convection zone to the lower
corona. In the modeled chromosphere, the rising flux sheet produces a
large, cool, magnetized bubble. We compare this bubble with the observed
ones and find excellent agreement, including similar field strengths
and velocity signals in the photosphere and chromosphere, temperature
deficits, ascent speeds, expansion velocities, and lifetimes.

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Title: Time evolution of a single, quiet-Sun magnetic structure
Authors: Requerey, Iker S.; Bonet, José Antonio; Solanki, Sami K.;
Bellot Rubio, L. R.; Del Toro Iniesta, Jose Carlos
2014cosp...40E2828R Altcode:
Isolated flux tubes are considered to be fundamental magnetic building
blocks of the solar photosphere. Their formation is usually attributed
to the concentration of magnetic field to kG strengths by the convective
instability mechanism. However, the small size of the magnetic elements
in quiet-Sun areas has prevented this scenario from being studied
in fully resolved structures. Here we report on the formation and
subsequent evolution of a photospheric magnetic flux tube, observed
in the quiet Sun with unprecedented spatial resolution (0. (”) 15 -
0. (”) 18) and high temporal cadence (33 s). The observations were
acquired by the Imaging Magnetograph Experiment (IMaX) aboard the
textsc{Sunrise} balloon-borne solar observatory. The equipartition
field strength magnetic element is reached from the merging of
several magnetic flux patches in a mesogranule-sized sink. The
magnetic structure is then further intensified to kG field strengths by
convective collapse and granular compression. The fine structure found
within the flux concentration reveal that the scenario is more complex
than a canonical flux tube model. After a subsequent weakening process,
the field is further intensified to kG strengths. Seen as a whole, the
evolution of the magnetic structure is compatible with oscillations in
all basic physical quantities. A discussion on whether this evolution
fits to the current theoretical descriptions is also presented.

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Title: Flux emergence in the solar internetwork and its contribution
to the network
Authors: Gosic, Milan; Katsukawa, Yukio; Orozco Suarez, David; Bellot
Rubio, L. R.
2014cosp...40E1055G Altcode:
Network and internetwork magnetic fields are believed to play a
crucial role in the energy budget of the solar atmosphere. Therefore,
it is essential to understand how they are maintained on the
solar surface. Using high resolution Hinode/NFI magnetograms at
disk center, we automatically follow quiet Sun magnetic elements
from their appearance to disappearance. From up to 40 hours of
continuous measurements, we derive the flux emergence rate in the
solar internetwork to be around 40 Mx cm(-2) day(-1) . We show
that internetwork fields appearing in the interior of individual
supergranular cells contribute flux to the surrounding network at
a rate of 2×10(19) Mx h(-1) . In only 10-20 hours, internetwork
elements can transfer as much flux as resides in network features,
establishing them as the most important source of flux for the network
and the quiet Sun flux budget.

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Title: New insights into the evolution of magnetic bright point
plasma parameters
Authors: Utz, Dominik; Hanslmeier, Arnold; Bellot Rubio, L. R.;
Del Toro Iniesta, Jose Carlos; Jurcak, Jan
2014cosp...40E3448U Altcode:
The dynamics within the solar atmosphere are governed by the Suńs
magnetic fields. In the recent years the resolution limits were steadily
driven up by better and better instruments and telescopes (like Hinode,
Sunrise, NST, Gregor, ..) leading to higher resolved data. Therefore
the interest in ever smaller magnetic field structures within the solar
atmosphere rises. Among the smallest yet identified structures are
so-called magnetic bright points (MBPs). These features are thought to
be made up of single flux tubes and they have been studied exhaustively
in the Fraunhofer G-band since the 70´s of the last century. They are
important features not only due to their small scale (about 200 km in
diameter) and hence used as proxies for the smallest solar magnetic
field physics and processes, but also because they are involved in
topics like the chromospheric/coronal heating problem or the total
solar irradiance variation. In the current contribution we want to
study the evolution of important plasma parameters of MBPs, such
as temperature, magnetic field strength and line of sight velocity,
to get a deeper understanding of the involved physics and occuring
processes. Among the used data will be G-band filtergam data from
Hinode/SOT and spectro-polarimetric data from the IMaX instrument
onboard the Sunrise mission.

---------------------------------------------------------
Title: New insights into the temporal evolution of MBPs
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.;
Jurčak, J.; Thonhofer, S.; Bodnárová, M.; Hanslmeier, A.; Lemmerer,
B.; Piantschitsch, I.; Guttenbrunner, S.
2014CEAB...38...73U Altcode:
Magnetic bright points (MBPs) are among the most fascinating and
interesting manifestations of small-scale solar magnetic fields. In the
present work the temporal evolution of MBPs is followed in data sets
taken by the Hinode satellite. The analysed data and obtained results
confirm a recently presented study done with Sunrise/IMaX data, namely
that MBPs are features undergoing fast evolution with magnetic fields
starting around the equipartition field strength, then showing strong
downflows (between 2 to 4 km/s) causing the magnetic field to amplify
into the kG range (700 to 1500 G) before dissolving again. Furthermore
the initial field inclinations depend on the initial magnetic field
strengths and show an evolution with more vertical angles at some
point during the evolution.

---------------------------------------------------------
Title: Effects of flux emergence in the outer solar
atmosphere. Observational advances
Authors: Ortiz Carbonell, Ada; De Pontieu, Bart; Bellot Rubio, L. R.;
Hansteen, Viggo; Rouppe van der Voort, Luc; Carlsson, Mats
2014cosp...40E2387O Altcode:
We study granular sized magnetic flux emergence events that occur in
a flux emergence region in NOAA 11850 on September 25, 2013. During
that time, the first co-observing campaign between the Swedish 1 m
Solar Telescope and the IRIS spacecraft was carried out. Simultaneous
observations of the Halpha 656.28 nm and Ca II 854.2 nm chromospheric
lines, and the Fe I 630.25 nm photospheric line, were made with
the CRISP/SST spectropolarimeter reaching a spatial resolution of
0."14. At the same time, IRIS was performing a four-step dense raster
of the said emerging flux region, taking slit-jaw images at 133 (C II
transiti on region), 140 (Si IV, transition region), 279.6 (Mg II k,
core, upper chromosphere), and 283.2 nm (Mg II k, wing, photosphere),
obtaining thus the highest resolution images ever taken of the upper
chromosphere and transition region. The photospheric and chromospheric
properties of the emerging magnetic flux bubbles have been described
in detail in Ortiz et al. (2014). However, in the current work we are
able to follow such lower atmosphere observations of flux emergence
up to the transition region with unprecedented spatial and temporal
resolution. We describe the properties (size, time delays, lifetime,
velocities, temperature) of the observed signatures of flux emergence
in the transition region. We believe this may be an important mechanism
of transporting energy and magnetic flux to the upper layers of the
solar atmosphere, namely the transition region and corona, at least
in cases when active regions are formed by flux emerging through the
photosphere. * Ortiz et al. (2014) ApJ 781, 126

---------------------------------------------------------
Title: Parallelization of the SIR code
Authors: Thonhofer, S.; Bellot Rubio, L. R.; Utz, D.; Jurčak, J.;
Hanslmeier, A.; Piantschitsch, I.; Pauritsch, J.; Lemmerer, B.;
Guttenbrunner, S.
2014CEAB...38...31T Altcode:
A high-resolution 3-dimensional model of the photospheric magnetic
field is essential for the investigation of small-scale solar magnetic
phenomena. The SIR code is an advanced Stokes-inversion code that
deduces physical quantities, e.g. magnetic field vector, temperature,
and LOS velocity, from spectropolarimetric data. We extended this code
by the capability of directly using large data sets and inverting the
pixels in parallel. Due to this parallelization it is now feasible to
apply the code directly on extensive data sets. Besides, we included
the possibility to use different initial model atmospheres for the
inversion, which enhances the quality of the results.

---------------------------------------------------------
Title: Diffusion of Solar Magnetic Elements up to Supergranular
Spatial and Temporal Scales
Authors: Giannattasio, F.; Del Moro, D.; Berrilli, F.; Bellot Rubio,
L.; Gošić, M.; Orozco Suárez, D.
2013ApJ...770L..36G Altcode: 2013arXiv1305.4006G
The study of spatial and temporal scales on which small magnetic
structures (magnetic elements) are organized in the quiet Sun
may be approached by determining how they are transported on the
solar photosphere by convective motions. The process involved
is diffusion. Taking advantage of Hinode high spatial resolution
magnetograms of a quiet-Sun region at the disk center, we tracked
20,145 magnetic elements. The large field of view (~50 Mm) and the
long duration of the observations (over 25 hr without interruption at
a cadence of 90 s) allowed us to investigate the turbulent flows at
unprecedented large spatial and temporal scales. In the field of view
an entire supergranule is clearly recognizable. The magnetic element
displacement spectrum shows a double-regime behavior: superdiffusive
(γ = 1.34 ± 0.02) up to granular spatial scales (~1500 km) and
slightly superdiffusive (γ = 1.20 ± 0.05) up to supergranular scales.

---------------------------------------------------------
Title: Temporal variations in solar magnetic bright points intensity
and plasma parameters
Authors: Jurčák, J.; Utz, D.; Bellot Rubio, L. R.
2013JPhCS.440a2032J Altcode:
Magnetic bright points are one of the finest magnetic structures
observed in the solar atmosphere. They possibly represent single
flux tubes in quiet Sun regions. Their formation is described by the
convective collapse model, while the decay phase of these structures
is not well characterized yet. We attempt to follow the evolution of a
few selected examples of MBPs and to study their changes in brightness
and also the variations of plasma parameters during their lifetime. We
use data from the Hinode satellite and the Sunrise mission. The G-band
observations taken with a cadence of 30 seconds by the Hinode Solar
Optical Telescope (SOT) show very fast changes of the maximum intensity
of these structures. The complementary spectropolarimetric data, which
are used to estimate the plasma parameters, were taken with a cadence
of approximately two minutes. The variations of plasma parameters
cannot be matched one to one to the changes in intensity due to the
different temporal resolution. However, the slow changes of intensity
with large amplitude are matched with variations of magnetic field
strength and line-of-sight (LOS) velocity. The Sunrise/IMaX data have
a temporal resolution of 32 seconds and show fast variations in the
line wing intensity. These variations are associated with changes in
the magnetic field strength and LOS velocity.

---------------------------------------------------------
Title: Is Magnetic Reconnection the Cause of Supersonic Upflows in
Granular Cells?
Authors: Borrero, J. M.; Martínez Pillet, V.; Schmidt, W.; Quintero
Noda, C.; Bonet, J. A.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.
2013ApJ...768...69B Altcode: 2013arXiv1303.2557B
In a previous work, we reported on the discovery of supersonic magnetic
upflows on granular cells in data from the SUNRISE/IMaX instrument. In
the present work, we investigate the physical origin of these events
employing data from the same instrument but with higher spectral
sampling. By means of the inversion of Stokes profiles we are able
to recover the physical parameters (temperature, magnetic field,
line-of-sight velocity, etc.) present in the solar photosphere at the
time of these events. The inversion is performed in a Monte-Carlo-like
fashion, that is, repeating it many times with different initializations
and retaining only the best result. We find that many of the events are
characterized by a reversal in the polarity of the magnetic field along
the vertical direction in the photosphere, accompanied by an enhancement
in the temperature and by supersonic line-of-sight velocities. In
about half of the studied events, large blueshifted and redshifted
line-of-sight velocities coexist above/below each other. These features
can be explained in terms of magnetic reconnection, where the energy
stored in the magnetic field is released in the form of kinetic
and thermal energy when magnetic field lines of opposite polarities
coalesce. However, the agreement with magnetic reconnection is not
perfect and, therefore, other possible physical mechanisms might also
play a role.

---------------------------------------------------------
Title: A Magnetic Bright Point Case Study
Authors: Utz, D.; Jurčák, J.; Bellot-Rubio, L.; del Toro Iniesta,
J. C.; Thonhofer, S.; Hanslmeier, A.; Veronig, A.; Muller, R.;
Lemmerer, B.
2013CEAB...37..459U Altcode:
Due to its magnetic fields our host star - the Sun - becomes the
interesting object for research as we know it. The magnetic fields
themselves cover different spatial, lifetime and strength scales and
reach down from enormous flux concentrations like active sunspot
groups to single isolated magnetic flux tubes and even weaker,
predominantly inclined intranetwork structures. Flux tubes can be seen
in filtergram observations as magnetic bright points (MBPs). They are
of interest for research not only due to their sheer existence but
due to their important role in atmospheric heating (wave heating as
well as reconnection processes), to their role in the understanding
of creation and annihilation of magnetic fields as well as to their
influence on the total solar irradiance variation. In this study we
present a close look onto an evolutionary track of an MBP from its
formation to its disintegration. Physical quantities of MBPs like
their magnetic field strength and inclination, their line-of-sight
velocity, and their temperature at different heights are inferred
from the inversion of spectropolarimetric data. Original data are
taken from the Sunrise/IMaX instrument and constitute a time series
of some 60 min. The presented case resembles the convective collapse
model and is in agreement with previous studies.

---------------------------------------------------------
Title: Inversions of L12-2 IMaX data of an emerging flux mantle
Authors: Guglielmino, S. L.; Martínez Pillet, V.; Ruiz Cobo,
B.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.; Solanki, S. K.;
Sunrise/IMaX Team
2013MmSAI..84..355G Altcode:
We present the analysis of a flux emergence event observed with
the IMaX magnetograph flown aboard the SUNRISE balloon. IMaX took a
15' sequence with cadence of 31 s along the Fe I line at 525.0 nm,
acquiring only Stokes I and V at 12 line positions (L12-2 mode). This
sequence shows the emergence of a flux mantle at mesogranular scale,
cospatial with a large exploding granule. An undesired cross-talk
between Stokes U and V was found in such L12-2 data. We show that the
use of a modified version of the SIR inversion code is able to remove
such effect in inferring the physical quantities of interest.

---------------------------------------------------------
Title: Requirements for the Analysis of Quiet-Sun Internetwork
Magnetic Elements with EST and ATST
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Katsukawa, Y.
2012ASPC..463...57O Altcode: 2012arXiv1203.2185O
The quiet-Sun internetwork is permeated by weak and highly inclined
magnetic fields whose physical properties, dynamics, and magnetic
interactions are not fully understood. High spatial resolution
magnetograms show them as discrete magnetic elements that appear/emerge
and disappear/cancel continuously over the quiet Sun surface. The
4-m European Solar Telescope (EST) and the Advanced Technology
Solar Telescope (ATST) will obtain two-dimensional, high cadence,
high precision polarimetric measurements at the diffraction limit
(30 km). Here, we compile the basic requirements for the observation
of internetwork fields with EST and ATST (field of view, cadence,
instrument configuration, etc.). More specifically, we concentrate
on the field-of-view requirements. To set them we analyze the proper
motion of internetwork magnetic elements across the solar surface. We
use 13 hours of magnetograms taken with the Hinode satellite to
identify and track thousands of internetwork magnetic element in an
isolated supergranular cell. We calculate the velocity components of
each element and the mean distance they travel. The results show that,
on average, magnetic elements in the interior of supergranular cells
move toward the network. The radial velocity is observed to depend on
the distance to the center of the supergranule. Internetwork magnetic
elements travel 4″ on average. These results suggest that ATST and
EST should cover, at least, one supergranular cell to obtain a complete
picture of the quiet Sun internetwork.

---------------------------------------------------------
Title: Comparing Simultaneous Measurements of two High-Resolution
Imaging Spectropolarimeters: The `Göttingen' FPI@VTT and CRISP@SST
Authors: Bello González, N.; Bellot Rubio, L. R.; Ortiz, A.; Rezaei,
R.; Rouppe van der Voort, L.; Schlichenmaier, R.
2012ASPC..463..251B Altcode: 2012arXiv1204.1023B
In July 2009, the leading spot of the active region NOAA11024 was
observed simultaneously and independently with the ‘Göttingen’
FPI at VTT and CRISP at SST, i.e., at two different sites,
telescopes, instruments and using different spectral lines. The data
processing and data analysis have been carried out independently
with different techniques. Maps of physical parameters retrieved
from 2D spectro-polarimetric data observed with ‘Göttingen’
FPI and CRISP show an impressive agreement. In addition, the
‘Göttingen’ FPI maps also exhibit a notable resemblance with
simultaneous TIP (spectrographic) observations. The consistency in the
results demonstrates the excellent capabilities of these observing
facilities. Besides, it confirms the solar origin of the detected
signals and the reliability of FPI-based spectro-polarimeters.

---------------------------------------------------------
Title: Turbulent diffusion on the solar photosphere through 24-hour
continuous observations of magnetic elements
Authors: Giannattasio, F.; Berrilli, F.; Del Moro, D.; Bellot Rubio,
L.; Orozco Suarez, D.; Gosic, M.
2012AGUFMSH13A2242G Altcode:
Solar atmosphere is a unique laboratory for the study of turbulent
flows under extreme conditions (e.g. very high Reynolds numbers). The
turbulent nature of the flow may be approached by determining how
magnetic flux elements are transported on the solar surface, and
measuring the spatio-temporal scales on which these small magnetic
structures are organized. The process involved is diffusion. Several
works explored this topic, both by simulations and observations,
and the results are often contradictory, ranging from fully-developed
turbulent scenarios to normal-diffusive motions. We analyze 24-hour
continuous Hinode SOT observations of a supergranular region (for the
first time these long scales are explored), studying the evolution of
the mutual distance between magnetic element pairs and its scaling laws,
in order to investigate the diffusion process. We find a super-diffusive
behavior, with a gamma index depending on the spatial scale selected.

---------------------------------------------------------
Title: The Connection between Internetwork Magnetic Elements and
Supergranular Flows
Authors: Orozco Suárez, D.; Katsukawa, Y.; Bellot Rubio, L. R.
2012ApJ...758L..38O Altcode:
The advection of internetwork magnetic elements by supergranular
convective flows is investigated using high spatial resolution, high
cadence, and high signal-to-noise ratio Na I D1 magnetograms obtained
with the Hinode satellite. The observations show that magnetic elements
appear everywhere across the quiet Sun surface. We calculate the proper
motion of these magnetic elements with the aid of a feature tracking
algorithm. The results indicate that magnetic elements appearing in
the interior of supergranules tend to drift toward the supergranular
boundaries with a non-constant velocity. The azimuthally averaged
radial velocities of the magnetic elements and of the supergranular
flow, calculated from a local correlation tracking technique applied
to Dopplergrams, are very similar. This suggests that, in the long
term, surface magnetic elements are advected by supergranular flows,
although on short timescales their very chaotic motions are driven
mostly by granular flows and other processes.

---------------------------------------------------------
Title: Resolving the Internal Magnetic Structure of the Solar Network
Authors: Martínez González, M. J.; Bellot Rubio, L. R.; Solanki,
S. K.; Martínez Pillet, V.; Del Toro Iniesta, J. C.; Barthol, P.;
Schmidt, W.
2012ApJ...758L..40M Altcode: 2012arXiv1209.2584M
We analyze the spectral asymmetry of Stokes V (circularly polarized)
profiles of an individual network patch in the quiet Sun observed
by Sunrise/IMaX. At a spatial resolution of 0farcs15-0farcs18, the
network elements contain substructure which is revealed by the spatial
distribution of Stokes V asymmetries. The area asymmetry between the
red and blue lobes of Stokes V increases from nearly zero at the core
of the structure to values close to unity at its edges (single-lobed
profiles). Such a distribution of the area asymmetry is consistent
with magnetic fields expanding with height, i.e., an expanding
magnetic canopy (which is required to fulfill pressure balance and
flux conservation in the solar atmosphere). Inversion of the Stokes
I and V profiles of the patch confirms this picture, revealing a
decreasing field strength and increasing height of the canopy base
from the core to the periphery of the network patch. However, the
non-roundish shape of the structure and the presence of negative area
and amplitude asymmetries reveal that the scenario is more complex than
a canonical flux tube expanding with height surrounded by downflows.

---------------------------------------------------------
Title: Temporal Evolution of Velocity and Magnetic Field in and
around Umbral Dots
Authors: Watanabe, Hiroko; Bellot Rubio, Luis R.; de la Cruz
Rodríguez, Jaime; Rouppe van der Voort, Luc
2012ApJ...757...49W Altcode: 2012arXiv1207.6006W
We study the temporal evolution of umbral dots (UDs) using measurements
from the CRISP imaging spectropolarimeter at the Swedish 1 m Solar
Telescope. Scans of the magnetically sensitive 630 nm iron lines
were performed under stable atmospheric conditions for 71 minutes
with a cadence of 63 s. These observations allow us to investigate
the magnetic field and velocity in and around UDs at a resolution
approaching 0farcs13. From the analysis of 339 UDs, we draw the
following conclusions: (1) UDs show clear hints of upflows, as predicted
by magnetohydrodynamic simulations. By contrast, we could not find
systematic downflow signals. Only in very deep layers, we detect
localized downflows around UDs, but they do not persist in time. (2)
We confirm that UDs exhibit weaker and more inclined fields than their
surroundings, as reported previously. However, UDs that have strong
fields above 2000 G or are in the decay phase show enhanced and more
vertical fields. (3) There are enhanced fields at the migration front
of UDs detached from penumbral grains, as if their motion were impeded
by the ambient field. (4) Long-lived UDs travel longer distances with
slower proper motions. Our results appear to confirm some aspects of
recent numerical simulations of magnetoconvection in the umbra (e.g.,
the existence of upflows in UDs), but not others (e.g., the systematic
weakening of the magnetic field at the position of UDs).

---------------------------------------------------------
Title: Pervasive Linear Polarization Signals in the Quiet Sun
Authors: Bellot Rubio, L. R.; Orozco Suárez, D.
2012ApJ...757...19B Altcode: 2012arXiv1207.0692B
This paper investigates the distribution of linear polarization signals
in the quiet-Sun internetwork using ultra-deep spectropolarimetric
data. We reduce the noise of the observations as much as is feasible
by adding single-slit measurements of the Zeeman-sensitive Fe I 630 nm
lines taken by the Hinode spectropolarimeter. The integrated Stokes
spectra are employed to determine the fraction of the field of view
covered by linear polarization signals. We find that up to 69% of
the quiet solar surface at disk center shows Stokes Q or U profiles
with amplitudes larger than 0.032% (4.5 times the noise level of 7 ×
10-5 reached by the longer integrations). The mere presence
of linear polarization in most of the quiet Sun implies that the weak
internetwork fields must be highly inclined, but we quantify this
by inverting those pixels with Stokes Q or U signals well above the
noise. This allows for a precise determination of the field inclination,
field strength, and field azimuth because the information carried by all
four Stokes spectra is used simultaneously. The inversion is performed
for 53% of the observed field of view at a noise level of 1.3 ×
10-4 I c. The derived magnetic distributions are
thus representative of more than half of the quiet-Sun internetwork. Our
results confirm the conclusions drawn from previous analyses using
mainly Stokes I and V: internetwork fields are very inclined, but
except in azimuth they do not seem to be isotropically distributed.

---------------------------------------------------------
Title: Analysis of a Fragmenting Sunspot Using Hinode Observations
Authors: Louis, Rohan E.; Ravindra, B.; Mathew, Shibu K.; Bellot Rubio,
Luis R.; Raja Bayanna, A.; Venkatakrishnan, P.
2012ApJ...755...16L Altcode: 2012arXiv1205.6669L
We employ high-resolution filtergrams and polarimetric measurements
from Hinode to follow the evolution of a sunspot for eight days
starting on 2007 June 28. The imaging data were corrected for intensity
gradients, projection effects, and instrumental stray light prior to
the analysis. The observations show the formation of a light bridge
at one corner of the sunspot by a slow intrusion of neighboring
penumbral filaments. This divided the umbra into two individual
umbral cores. During the light bridge formation, there was a steep
increase in its intensity from 0.28 to 0.7 I QS in nearly
4 hr, followed by a gradual increase to quiet-Sun (QS) values in 13
hr. This increase in intensity was accompanied by a large reduction
in the field strength from 1800 G to 300 G. The smaller umbral core
gradually broke away from the parent sunspot nearly two days after
the formation of the light bridge, rendering the parent spot without a
penumbra at the location of fragmentation. The penumbra in the fragment
disappeared first within 34 hr, followed by the fragment whose area
decayed exponentially with a time constant of 22 hr. In comparison, the
parent sunspot area followed a linear decay rate of 0.94 Mm2
hr-1. The depleted penumbra in the parent sunspot regenerated
when the inclination of the magnetic field at the penumbra-QS boundary
became within 40° from being completely horizontal and this occurred
near the end of the fragment's lifetime. After the disappearance of the
fragment, another light bridge formed in the parent which had similar
properties as the fragmenting one, but did not divide the sunspot. The
significant weakening in field strength in the light bridge along with
the presence of granulation is suggestive of strong convection in the
sunspot, which might have triggered the expulsion and fragmentation of
the smaller spot. Although the presence of QS photospheric conditions
in sunspot umbrae could be a necessary condition for fragmentation,
it is not a sufficient one.

---------------------------------------------------------
Title: Bipolar Magnetic Structures in Sunspot Penumbrae
Authors: Sainz Dalda, A.; Bellot Rubio, L. R.
2012ASPC..454..221S Altcode:
We present a study of bipolar, sea-serpent-like structures in
the penumbra of sunspots. Our analysis is based on longitudinal
magnetograms and full Stokes spectra of AR 10923 taken with the
NFI and SP instruments of Hinode. The circular polarization maps
reveal the presence of many elongated structures in the mid penumbra
and beyond. They consist of two opposite-polarity patches that move
together as a single entity toward the outer penumbral boundary, where
they become moving magnetic features. Their Stokes profiles suggest
a complex magnetic topology. The existence of opposite polarities in
the penumbra is well known from previous analyses, but this is the
first time that their bipolar nature is unveiled. Our observations
also demonstrate that they are intimately connected with the Evershed
flow. These structures provide new constraints to theoretical and
numerical models of sunspots.

---------------------------------------------------------
Title: Supersonic flows in the solar photosphere
Authors: Bellot Rubio, Luis
2012cosp...39..133B Altcode: 2012cosp.meet..133B
Except for sunspot penumbrae, very few instances of supersonic mass
flows in the photosphere were known a few years ago. The situation has
changed dramatically thanks to the extremely high spatial resolution
provided by Hinode, SUNRISE, and the Swedish 1-m Solar Telescope. Using
spectropolarimetric measurements from these instruments, supersonic
flows have been discovered both in the quiet Sun and in active regions,
in places where they were completely unexpected. Most of them are
directed downward, but there are also cases of upward and horizontal
motions. Quiescent, relatively stable structures that harbor supersonic
flows include granular cells, small-scale flux tubes undergoing
convective collapse, pores, light bridges, and sunspot penumbrae
(at all radial distances). An overview of these flows will be given,
emphasizing their properties and effects on higher atmospheric layers.

---------------------------------------------------------
Title: Evolution of internetwork magnetic fields inside supergranular
cells
Authors: Gosic, Milan; Katsukawa, Yukio; Bellot Rubio, Luis; Orozco
Suarez, David
2012cosp...39..657G Altcode: 2012cosp.meet..657G
To understand the formation of small-scale magnetic fields in the quiet
Sun and their contribution to the solar activity, it is essential to
investigate the properties of internetwork magnetic fields. Using
Hinode/NFI magnetograms of very high sensitivity (7 Mx/cm^{2}),
spatial resolution (0.16 arcsec/pixel), and cadence (90 s), we
follow the evolution of magnetic fields inside of a supergranular
cell located at disk center. In 5 hours of continuous measurements
covering an area of 20.8 × 23.2 arcsec^{2}, we manually track 2415
magnetic elements from appearance to disappearance and derive their
physical properties. The average values of the magnetic flux, effective
diameter, lifetime, and horizontal velocity are 3 × 10^{17} Mx, 0.5 Mm,
17 min, and 2 km/s, respectively. We also investigate how the physical
parameters of the individual elements vary as a function of time,
flux, and spatial position. Using this unique data set, we determine
with unprecedented accuracy the flux emergence and disappearance rate
in the solar internetwork.

---------------------------------------------------------
Title: Properties of Umbral Dots from Stray Light Corrected Hinode
Filtergrams
Authors: Louis, Rohan E.; Mathew, Shibu K.; Bellot Rubio, Luis R.;
Ichimoto, Kiyoshi; Ravindra, B.; Raja Bayanna, A.
2012ApJ...752..109L Altcode: 2012arXiv1204.4088L
High-resolution blue continuum filtergrams from Hinode are employed
to study the umbral fine structure of a regular unipolar sunspot. The
removal of scattered light from the images increases the rms contrast
by a factor of 1.45 on average. Improvement in image contrast renders
identification of short filamentary structures resembling penumbrae
that are well separated from the umbra-penumbra boundary and comprise
bright filaments/grains flanking dark filaments. Such fine structures
were recently detected from ground-based telescopes and have now been
observed with Hinode. A multi-level tracking algorithm was used to
identify umbral dots (UDs) in both the uncorrected and corrected images
and to track them in time. The distribution of the values describing
the photometric and geometric properties of UDs is more easily affected
by the presence of stray light while it is less severe in the case
of kinematic properties. Statistically, UDs exhibit a peak intensity,
effective diameter, lifetime, horizontal speed, and a trajectory length
of 0.29I QS, 272 km, 8.4 minutes, 0.45 km s-1,
and 221 km, respectively. The 2 hr 20 minute time sequence depicts
several locations where UDs tend to appear and disappear repeatedly
with various time intervals. The correction for scattered light in the
Hinode filtergrams facilitates photometry of umbral fine structure,
which can be related to results obtained from larger telescopes and
numerical simulations.

---------------------------------------------------------
Title: 4th Hinode Science Meeting: Unsolved Problems and Recent
Insights
Authors: Bellot Rubio, L.; Reale, F.; Carlsson, M.
2012ASPC..455.....B Altcode: 2012ASPC..455.....R
No abstract at ADS

---------------------------------------------------------
Title: Observations of Supersonic Downflows near the Umbra-Penumbra
Boundary of Sunspots as Revealed by Hinode
Authors: Louis, R. E.; Bellot Rubio, L. R.; Mathew, S. K.;
Venkatakrishnan, P.
2012ASPC..455...75L Altcode: 2011arXiv1101.0751L
High resolution spectropolarimetric observations by Hinode have revealed
the existence of supersonic downflows at the umbra-penumbra boundary
of 3 sunspots (Louis et al. 2011). These downflows are observed to be
co-spatial with bright penumbral filaments and occupy an area greater
than 1.6 arcsec2. They are located at the center-side
penumbra and have the same polarity as the sunspot which suggests
that they are not associated with the Evershed flow. In this paper
we describe the supersonic velocities observed in NOAA AR 10923 and
discuss the photospheric as well as chromospheric brightenings that
lie close to the downflowing areas. Our observations suggest that this
phenomenon is driven by dynamic and energetic physical processes in the
inner penumbra which affect the chromosphere, providing new constraints
to numerical models of sunspots.

---------------------------------------------------------
Title: Analysis of Quiet-Sun Internetwork Magnetic Fields Based on
Linear Polarization Signals
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.
2012ApJ...751....2O Altcode: 2012arXiv1203.1440O
We present results from the analysis of Fe I 630 nm measurements
of the quiet Sun taken with the spectropolarimeter of the Hinode
satellite. Two data sets with noise levels of 1.2 × 10-3
and 3 × 10-4 are employed. We determine the distribution
of field strengths and inclinations by inverting the two observations
with a Milne-Eddington model atmosphere. The inversions show a
predominance of weak, highly inclined fields. By means of several tests
we conclude that these properties cannot be attributed to photon noise
effects. To obtain the most accurate results, we focus on the 27.4%
of the pixels in the second data set that have linear polarization
amplitudes larger than 4.5 times the noise level. The vector magnetic
field derived for these pixels is very precise because both circular
and linear polarization signals are used simultaneously. The inferred
field strength, inclination, and filling factor distributions agree
with previous results, supporting the idea that internetwork (IN)
fields are weak and very inclined, at least in about one quarter
of the area occupied by the IN. These properties differ from those
of network fields. The average magnetic flux density and the mean
field strength derived from the 27.4% of the field of view with clear
linear polarization signals are 16.3 Mx cm-2 and 220 G,
respectively. The ratio between the average horizontal and vertical
components of the field is approximately 3.1. The IN fields do not
follow an isotropic distribution of orientations.

---------------------------------------------------------
Title: Granular-Scale Elementary Flux Emergence Episodes in a Solar
Active Region
Authors: Vargas Domínguez, S.; van Driel-Gesztelyi, L.; Bellot Rubio,
L. R.
2012SoPh..278...99V Altcode: 2012SoPh..tmp..259F; 2012arXiv1203.6428V
We analyse data from Hinode spacecraft taken over two 54-minute periods
during the emergence of AR 11024. We focus on small-scale portions
within the observed solar active region and discover the appearance of
very distinctive small-scale and short-lived dark features in Ca II H
chromospheric filtergrams and Stokes I images. The features appear in
regions with close-to-zero longitudinal magnetic field, and are observed
to increase in length before they eventually disappear. Energy release
in the low chromospheric line is detected while the dark features
are fading. Three complete series of these events are detected with
remarkably similar properties, i.e. lifetime of ≈ 12 min, maximum
length and area of 2 - 4 Mm and 1.6 - 4 Mm2, respectively,
and all with associated brightenings. In time series of magnetograms a
diverging bipolar configuration is observed accompanying the appearance
of the dark features and the brightenings. The observed phenomena
are explained as evidencing elementary flux emergence in the solar
atmosphere, i.e. small-scale arch filament systems rising up from the
photosphere to the lower chromosphere with a length scale of a few
solar granules. Brightenings are explained as being the signatures of
chromospheric heating triggered by reconnection of the rising loops
(once they have reached chromospheric heights) with pre-existing
magnetic fields, as well as being due to reconnection/cancellation
events in U-loop segments of emerging serpentine fields. The
characteristic length scale, area and lifetime of these elementary
flux emergence events agree well with those of the serpentine field
observed in emerging active regions. We study the temporal evolution
and dynamics of the events and compare them with the emergence of
magnetic loops detected in quiet Sun regions and serpentine flux
emergence signatures in active regions. The physical processes of
the emergence of granular-scale magnetic loops seem to be the same
in the quiet Sun and active regions. The difference is the reduced
chromospheric emission in the quiet Sun attributed to the fact that
loops are emerging in a region of lower ambient magnetic field density,
making interactions and reconnection less likely to occur. Incorporating
the novel features of granular-scale flux emergence presented in this
study, we advance the scenario for serpentine flux emergence.

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Title: Observation, inversion and numerical simulation of single-lobed
Stokes V profiles in the quiet sun.
Authors: Sainz Dalda, A.; Martínez-Sykora, J.; Bellot Rubio, L.;
Title, A.
2012decs.confE..89S Altcode:
We have studied characteristics and statistics of strong asymmetric
profiles in Stokes V, i.e., single-lobed profiles, in quiet sun using
Hinode/SOT. These profiles require the existence of a velocity gradient
along the line-of-sight, possibly associated with gradients of magnetic
field strength, inclination and/or azimuth. For a better understanding,
observations, inversions and numerical simulations are compared. We
focus our analysis of the observations on the statistical properties
of the single-lobed Stokes V profiles and the results provided by the
inversions using SIRJUMP, which is an LTE inversion code that can
reproduce sharp discontinuities or jump in the magnetic field and
line-of-sight velocity of the atmosphere model. In the quiet sun,
magnetic field is continuously appearing and disappearing at small
scales due to the convective motions and the input of new flux from
deeper layers. From radiative MHD 3D simulations, using Bifrost code, we
note that most of these small scale processes have stratifications with
gradients of magnetic field strength, inclination and velocities. As
result, those stratifications showing jumps in the magnetic field
configuration are associated with the existence of single-lobe Stokes
V profiles in the solar photosphere, as we previously assumed for the
inversions. We show that most of these profiles come from emerging and
disappearance magnetic flux in small scales in the simulations. Finally,
we emphasize importance of the comparison between the synthetic profiles
from the simulations with the observed ones and the atmospheres that
produce them. This comparison will ultimately improve the realism of
the simulations and quantify the emerging and disappearance flux in
the quiet sun.

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Title: Study of Single-lobed Circular Polarization Profiles in the
Quiet Sun
Authors: Sainz Dalda, A.; Martínez-Sykora, J.; Bellot Rubio, L.;
Title, A.
2012ApJ...748...38S Altcode: 2012arXiv1202.0593S
The existence of asymmetries in the circular polarization (Stokes V)
profiles emerging from the solar photosphere has been known since
the 1970s. These profiles require the presence of a velocity gradient
along the line of sight (LOS), possibly associated with gradients of
magnetic field strength, inclination, and/or azimuth. We have focused
our study on the Stokes V profiles showing extreme asymmetry in the
form of only one lobe. Using Hinode spectropolarimetric measurements,
we have performed a statistical study of the properties of these
profiles in the quiet Sun. We show their spatial distribution, their
main physical properties, how they are related with several physical
observables, and their behavior with respect to their position on
the solar disk. The single-lobed Stokes V profiles occupy roughly
2% of the solar surface. For the first time, we have observed their
temporal evolution and have retrieved the physical conditions of the
atmospheres from which they emerged using an inversion code implementing
discontinuities of the atmospheric parameters along the LOS. In
addition, we use synthetic Stokes profiles from three-dimensional
magnetoconvection simulations to complement the results of the
inversion. The main features of the synthetic single-lobed profiles
are in general agreement with the observed ones, lending support to
the magnetic and dynamic topologies inferred from the inversion. The
combination of all these different analyses suggests that most of the
single-lobed Stokes V profiles are signals coming from the magnetic
flux emergence and/or submergence processes taking place in small
patches in the photosphere of the quiet Sun.

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Title: The Frontier between Small-scale Bipoles and Ephemeral Regions
in the Solar Photosphere: Emergence and Decay of an Intermediate-scale
Bipole Observed with SUNRISE/IMaX
Authors: Guglielmino, S. L.; Martínez Pillet, V.; Bonet, J. A.;
del Toro Iniesta, J. Carlos; Bellot Rubio, L. R.; Solanki, S. K.;
Schmidt, W.; Gandorfer, A.; Barthol, P.; Knölker, M.
2012ApJ...745..160G Altcode: 2011arXiv1110.1405G
We report on the photospheric evolution of an intermediate-scale (≈4
Mm footpoint separation) magnetic bipole, from emergence to decay,
observed in the quiet Sun at high spatial (0farcs3) and temporal (33 s)
resolution. The observations were acquired by the Imaging Magnetograph
Experiment imaging magnetograph during the first science flight of the
SUNRISE balloon-borne solar observatory. The bipole flux content is 6 ×
1017 Mx, representing a structure bridging the gap between
granular scale bipoles and the smaller ephemeral regions. Footpoints
separate at a speed of 3.5 km s-1 and reach a maximum
distance of 4.5 Mm before the field dissolves. The evolution of the
bipole is revealed to be very dynamic: we found a proper motion of
the bipole axis and detected a change of the azimuth angle of 90° in
300 s, which may indicate the presence of some writhe in the emerging
structure. The overall morphology and behavior are in agreement with
previous analyses of bipolar structures emerging at the granular scale,
but we also found several similarities with emerging flux structures
at larger scales. The flux growth rate is 2.6 × 1015 Mx
s-1, while the mean decay rate is one order of magnitude
smaller. We describe in some detail the decay phase of the bipole
footpoints that includes break up into smaller structures, and
interaction with preexisting fields leading to cancellation, but it
appears to be dominated by an as-yet unidentified diffusive process
that removes most of the flux with an exponential flux decay curve. The
diffusion constant (8 × 102 km2 s-1)
associated with this decay is similar to the values used to describe
the large-scale diffusion in flux transport models.

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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.
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 <A
href="http://www.aanda.org">http://www.aanda.org</A>

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Title: Spectropolarimetric Study of Sea-serpent Penumbral Filaments
and a Naked Sunspot
Authors: Sainz Dalda, Alberto; Tarbell, T.; Title, A.; Vargas
Dominguez, S.; Bellot Rubio, L. R.
2011SPD....42.0303S Altcode: 2011BAAS..43S.0303S
We present a spectropolarimetric study of the sea-serpent penumbral
filaments in AR NOAA 10944 and of a naked sunspot (i.e. a sunspot-like
feature without penumbra) in AR NOAA 10977. Both active regions were
observed by Hinode-SOT/SP in the photospheric lines Fe I 6301 &amp;
6302 [[Unable to Display Character: &amp;#506]]. The high spatial and
temporal resolution combined with the high polarimetric sensitivity
of these observations enables us to get a better understanding of the
dynamics of the penumbra and the moving magnetic feature (herafter MMF)
activity in and around both traditional and naked sunspots. Our results
show how the temporal evolution of the sea-serpent filaments fits
very well with the thin-tube flux model for the penumbra presented by
Schlichenmaier (2003). In addition, the spectropolarmetric analysis of
the naked sunspot addresses the issue posed by Zuccarello et al. (2009)
about the existence of bipolar MMFs around naked sunspots even when
they cannot be explained as an extension of the penumbral filaments.

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Title: Mesogranulation and the Solar Surface Magnetic Field
Distribution
Authors: Yelles Chaouche, L.; Moreno-Insertis, F.; Martínez Pillet,
V.; Wiegelmann, T.; Bonet, J. A.; Knölker, M.; Bellot Rubio, L. R.;
del Toro Iniesta, J. C.; Barthol, P.; Gandorfer, A.; Schmidt, W.;
Solanki, S. K.
2011ApJ...727L..30Y Altcode: 2010arXiv1012.4481Y
The relation of the solar surface magnetic field with mesogranular
cells is studied using high spatial (≈100 km) and temporal (≈30
s) resolution data obtained with the IMaX instrument on board
SUNRISE. First, mesogranular cells are identified using Lagrange
tracers (corks) based on horizontal velocity fields obtained through
local correlation tracking. After ≈20 minutes of integration, the
tracers delineate a sharp mesogranular network with lanes of width
below about 280 km. The preferential location of magnetic elements in
mesogranular cells is tested quantitatively. Roughly 85% of pixels with
magnetic field higher than 100 G are located in the near neighborhood
of mesogranular lanes. Magnetic flux is therefore concentrated in
mesogranular lanes rather than intergranular ones. Second, magnetic
field extrapolations are performed to obtain field lines anchored in
the observed flux elements. This analysis, therefore, is independent
of the horizontal flows determined in the first part. A probability
density function (PDF) is calculated for the distribution of distances
between the footpoints of individual magnetic field lines. The PDF has
an exponential shape at scales between 1 and 10 Mm, with a constant
characteristic decay distance, indicating the absence of preferred
convection scales in the mesogranular range. Our results support
the view that mesogranulation is not an intrinsic convective scale
(in the sense that it is not a primary energy-injection scale of solar
convection), but also give quantitative confirmation that, nevertheless,
the magnetic elements are preferentially found along mesogranular lanes.

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Title: The Imaging Magnetograph eXperiment (IMaX) for the Sunrise
Balloon-Borne Solar Observatory
Authors: Martínez Pillet, V.; del Toro Iniesta, J. C.;
Álvarez-Herrero, A.; Domingo, V.; Bonet, J. A.; González Fernández,
L.; López Jiménez, A.; Pastor, C.; Gasent Blesa, J. L.; Mellado, P.;
Piqueras, J.; Aparicio, B.; Balaguer, M.; Ballesteros, E.; Belenguer,
T.; Bellot Rubio, L. R.; Berkefeld, T.; Collados, M.; Deutsch, W.;
Feller, A.; Girela, F.; Grauf, B.; Heredero, R. L.; Herranz, M.;
Jerónimo, J. M.; Laguna, H.; Meller, R.; Menéndez, M.; Morales, R.;
Orozco Suárez, D.; Ramos, G.; Reina, M.; Ramos, J. L.; Rodríguez,
P.; Sánchez, A.; Uribe-Patarroyo, N.; Barthol, P.; Gandorfer, A.;
Knoelker, M.; Schmidt, W.; Solanki, S. K.; Vargas Domínguez, S.
2011SoPh..268...57M Altcode: 2010SoPh..tmp..181M; 2010arXiv1009.1095M
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter
built by four institutions in Spain that flew on board the Sunrise
balloon-borne solar observatory in June 2009 for almost six days over
the Arctic Circle. As a polarimeter, IMaX uses fast polarization
modulation (based on the use of two liquid crystal retarders),
real-time image accumulation, and dual-beam polarimetry to reach
polarization sensitivities of 0.1%. As a spectrograph, the instrument
uses a LiNbO3 etalon in double pass and a narrow band
pre-filter to achieve a spectral resolution of 85 mÅ. IMaX uses the
high-Zeeman-sensitive line of Fe I at 5250.2 Å and observes all four
Stokes parameters at various points inside the spectral line. This
allows vector magnetograms, Dopplergrams, and intensity frames to be
produced that, after reconstruction, reach spatial resolutions in the
0.15 - 0.18 arcsec range over a 50×50 arcsec field of view. Time
cadences vary between 10 and 33 s, although the shortest one only
includes longitudinal polarimetry. The spectral line is sampled in
various ways depending on the applied observing mode, from just two
points inside the line to 11 of them. All observing modes include
one extra wavelength point in the nearby continuum. Gauss equivalent
sensitivities are 4 G for longitudinal fields and 80 G for transverse
fields per wavelength sample. The line-of-sight velocities are estimated
with statistical errors of the order of 5 - 40 m s−1. The
design, calibration, and integration phases of the instrument,
together with the implemented data reduction scheme, are described in
some detail.

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Title: Supersonic Downflows at the Umbra-Penumbra Boundary of Sunspots
Authors: Louis, Rohan E.; Bellot Rubio, Luis R.; Mathew, Shibu K.;
Venkatakrishnan, P.
2011ApJ...727...49L Altcode: 2010arXiv1010.0519L
High-resolution spectropolarimetric observations of three sunspots
taken with Hinode demonstrate the existence of supersonic downflows
at or close to the umbra-penumbra boundary which have not been
reported before. These downflows are confined to large patches,
usually encompassing bright penumbral filaments, and have lifetimes of
more than 14 hr. The presence of strong downflows in the center-side
penumbra near the umbra rules out an association with the Evershed
flow. Chromospheric filtergrams acquired close to the time of the
spectropolarimetric measurements show large, strong, and long-lived
brightenings in the neighborhood of the downflows. The photospheric
intensity also exhibits persistent brightenings comparable to the
quiet Sun. Interestingly, the orientation of the penumbral filaments
at the site of the downflows is similar to that resulting from the
reconnection process described by Ryutova et al. The existence of such
downflows in the inner penumbra represents a challenge for numerical
models of sunspots because they have to explain them in terms of
physical processes likely affecting the chromosphere.

---------------------------------------------------------
Title: Searching for Overturning Convection in Penumbral Filaments:
Slit Spectroscopy at 0farcs2 Resolution
Authors: Bellot Rubio, L. R.; Schlichenmaier, R.; Langhans, K.
2010ApJ...725...11B Altcode: 2010arXiv1009.5650B
Recent numerical simulations of sunspots suggest that overturning
convection is responsible for the existence of penumbral filaments
and the Evershed flow, but there is little observational evidence
of this process. Here, we carry out a spectroscopic search for
small-scale convective motions in the penumbra of a sunspot located
5° away from the disk center. The position of the spot is very
favorable for the detection of overturning downflows at the edges
of penumbral filaments. Our analysis is based on measurements of
the Fe I 709.0 nm line taken with the Littrow spectrograph of the
Swedish 1 m Solar Telescope under excellent seeing conditions. We
compute line bisectors at different intensity levels and derive
Doppler velocities from them. The velocities are calibrated using
a nearby telluric line, with systematic errors smaller than 150 m
s-1. Deep in the photosphere, as sampled by the bisectors
at the 80%-88% intensity levels, we always observe blueshifts or
zero velocities. The maximum blueshifts reach 1.2 km s-1
and tend to be cospatial with bright penumbral filaments. In the line
core, we detect blueshifts for the most part, with small velocities
not exceeding 300 m s-1. Redshifts also occur, but at the
level of 100-150 m s-1, and only occasionally. The fact
that they are visible in high layers casts doubts on their convective
origin. Overall, we do not find indications of downflows that could be
associated with overturning convection at our detection limit of 150
m s-1. Either no downflows exist, or we have been unable
to observe them because they occur beneath τ = 1 or the spatial
resolution/height resolution of the measurements is still insufficient.

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Title: Multiwavelength Observations of Small-scale Reconnection
Events Triggered by Magnetic Flux Emergence in the Solar Atmosphere
Authors: Guglielmino, S. L.; Bellot Rubio, L. R.; Zuccarello, F.;
Aulanier, G.; Vargas Domínguez, S.; Kamio, S.
2010ApJ...724.1083G Altcode: 2010arXiv1007.4657G
The interaction between emerging magnetic flux and the pre-existing
ambient field has become a "hot" topic for both numerical simulations
and high-resolution observations of the solar atmosphere. The appearance
of brightenings and surges during episodes of flux emergence is believed
to be a signature of magnetic reconnection processes. We present an
analysis of a small-scale flux emergence event in NOAA 10971, observed
simultaneously with the Swedish 1 m Solar Telescope on La Palma and the
Hinode satellite during a joint campaign in 2007 September. Extremely
high-resolution G-band, Hα, and Ca II H filtergrams, Fe I and Na
I magnetograms, EUV raster scans, and X-ray images show that the
emerging region was associated with chromospheric, transition region
and coronal brightenings, as well as with chromospheric surges. We
suggest that these features were caused by magnetic reconnection
at low altitude in the atmosphere. To support this idea, we perform
potential and linear force-free field extrapolations using the FROMAGE
service. The extrapolations show that the emergence site is cospatial
with a three-dimensional null point, from which a spine originates. This
magnetic configuration and the overall orientation of the field lines
above the emerging flux region are compatible with the structures
observed in the different atmospheric layers and remain stable against
variations of the force-free field parameter. Our analysis supports
the predictions of recent three-dimensional numerical simulations that
energetic phenomena may result from the interaction between emerging
flux and the pre-existing chromospheric and coronal field.

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Title: Retrieval of solar magnetic fields from high-spatial resolution
filtergraph data: the Imaging Magnetograph eXperiment (IMaX)
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Martínez Pillet,
V.; Bonet, J. A.; Vargas Domínguez, S.; Del Toro Iniesta, J. C.
2010A&A...522A.101O Altcode: 2010arXiv1006.5510O
Context. The design of modern instruments does not only imply thorough
studies of instrumental effects but also a good understanding of the
scientific analysis planned for the data. Aims: We investigate
the reliability of Milne-Eddington (ME) inversions of high-resolution
magnetograph measurements such as those to be obtained with the Imaging
Magnetograph eXperiment (IMaX) aboard the Sunrise balloon. We also
provide arguments to choose either Fe I 525.02 or 525.06 nm as the
most suitable line for IMaX. Methods: We reproduce an IMaX
observation using magnetoconvection simulations of the quiet Sun
and synthesizing the four Stokes profiles emerging from them. The
profiles are degraded by spatial and spectral resolution, noise,
and limited wavelength sampling, just as real IMaX measurements. We
invert these data and estimate the uncertainties in the retrieved
physical parameters caused by the ME approximation and the spectral
sampling. Results: It is possible to infer the magnetic field
strength, inclination, azimuth, and line-of-sight velocity from
standard IMaX measurements (4 Stokes parameters, 5 wavelength points,
and a signal-to-noise ratio of 1000) applying ME inversions to any
of the Fe I lines at 525 nm. We also find that telescope diffraction
has important effects on the spectra coming from very high resolution
observations of inhomogeneous atmospheres. Diffration reduces the
amplitude of the polarization signals and changes the asymmetry of
the Stokes profiles. Conclusions: The two Fe I lines at 525 nm
meet the scientific requirements of IMaX, but Fe I 525.02 nm is to be
preferred because it leads to smaller uncertainties in the retrieved
parameters and offers a better detectability of the weakest (linear)
polarization signals prevailing in the quiet Sun.

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Title: Two-dimensional solar spectropolarimetry with the KIS/IAA
Visible Imaging Polarimeter
Authors: Beck, C.; Bellot Rubio, L. R.; Kentischer, T. J.; Tritschler,
A.; Del Toro Iniesta, J. C.
2010A&A...520A.115B Altcode: 2010arXiv1007.1153B
Context. Spectropolarimetry at high spatial and spectral resolution
is a basic tool to characterize the magnetic properties of the solar
atmosphere. Aims: We introduce the KIS/IAA Visible Imaging
Polarimeter (VIP), a new post-focus instrument that upgrades the TESOS
spectrometer at the German Vacuum Tower Telescope (VTT) into a full
vector polarimeter. VIP is a collaboration between the Kiepenheuer
Institut für Sonnenphysik (KIS) and the Instituto de Astrofísica
de Andalucía (IAA-CSIC). Methods: We describe the optical
setup of VIP, the data acquisition procedure, and the calibration of
the spectropolarimetric measurements. We show examples of data taken
between 2005 and 2008 to illustrate the potential of the instrument. Results: VIP is capable of measuring the four Stokes profiles of
spectral lines in the range from 420 to 700 nm with a spatial resolution
better than 0farcs5. Lines can be sampled at 40 wavelength positions
in 60 s, achieving a noise level of about 2 × 10-3 with
exposure times of 300 ms and pixel sizes of 0farcs17 × 0farcs17 (2
× 2 binning). The polarization modulation is stable over periods of a
few days, ensuring high polarimetric accuracy. The excellent spectral
resolution of TESOS allows the use of sophisticated data analysis
techniques such as Stokes inversions. One of the first scientific
results of VIP presented here is that the ribbon-like magnetic
structures of the network are associated with a distinct pattern of
net circular polarization away from disk center. Conclusions:
VIP performs spectropolarimetric measurements of solar magnetic fields
at a spatial resolution that is only slightly worse than that of the
Hinode spectropolarimeter, while providing a 2D field field of view and
the possibility to observe up to four spectral regions sequentially
with high cadence. VIP can be used as a stand-alone instrument or in
combination with other spectropolarimeters and imaging systems of the
VTT for extended wavelength coverage.

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Title: Upflows in the Central Dark Lane of Sunspot Light Bridges
Authors: Rouppe van der Voort, L.; Bellot Rubio, L. R.; Ortiz, A.
2010ApJ...718L..78R Altcode: 2010arXiv1006.4578R
We use high spatial and spectral resolution observations obtained with
the CRisp Imaging SpectroPolarimeter at the Swedish 1 m Solar Telescope
to analyze the velocity profile of granular light bridges (LBs) in
a sunspot. We find upflows associated with the central dark lanes of
the LBs. From bisectors in the Fe I 630.15 nm line we find that the
magnitude of the upflows varies with height, with the strongest upflows
being deeper in the atmosphere. Typical upflow velocities measured from
the 70% bisector are around 500 m s-1 with peaks above 1 km
s-1. The upflows in the central dark lane are surrounded by
downflows of weaker magnitude, sometimes concentrated in patches with
enhanced velocities reaching up to 1.1 km s-1. A small
spatial offset between the upflows and the continuum dark lane is
interpreted as a line-of-sight effect due to the elevated nature of the
dark lane and the LB above the umbral surroundings. Our observations
show that the central dark lane in granular LBs is not equivalent to
the intergranular lanes of normal photospheric granulation that host
convective downflows. These results support recent MHD simulations of
magneto-convection in sunspot atmospheres.

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Title: Milne-Eddington inversion of the Fe I line pair at 630 nm
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Del Toro Iniesta,
J. C.
2010A&A...518A...3O Altcode: 2010arXiv1005.5013S; 2010arXiv1005.5013O
Context. The iron lines at 630.15 and 630.25 nm are often used to
determine the physical conditions of the solar photosphere. A common
approach is to invert them simultaneously under the Milne-Eddington
approximation. The same thermodynamic parameters are employed for the
two lines, except for their opacities, which are assumed to have a
constant ratio. Aims: We aim at investigating the validity of
this assumption, since the two lines are not exactly the same. Methods: We use magnetohydrodynamic simulations of the quiet
Sun to examine the behavior of the ME thermodynamic parameters and
their influence on the retrieval of vector magnetic fields and flow
velocities. Results: Our analysis shows that the two lines can
be coupled and inverted simultaneously using the same thermodynamic
parameters and a constant opacity ratio. The inversion of two lines
is significantly more accurate than single-line inversions because of
the larger number of observables.

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Title: Applicability of Milne-Eddington inversions to high spatial
resolution observations of the quiet Sun
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Vögler, A.; Del
Toro Iniesta, J. C.
2010A&A...518A...2O Altcode: 2010arXiv1005.5012O
Context. The physical conditions of the solar photosphere change on
very small spatial scales both horizontally and vertically. Such a
complexity may pose a serious obstacle to the accurate determination
of solar magnetic fields. Aims: We examine the applicability of
Milne-Eddington (ME) inversions to high spatial resolution observations
of the quiet Sun. Our aim is to understand the connection between
the ME inferences and the actual stratifications of the atmospheric
parameters. Methods: We use magnetoconvection simulations of
the solar surface to synthesize asymmetric Stokes profiles such as
those observed in the quiet Sun. We then invert the profiles with the
ME approximation. We perform an empirical analysis of the heights of
formation of ME measurements and analyze the uncertainties brought
about by the ME approximation. We also investigate the quality of the
fits and their relationship with the model stratifications. 
Results: The atmospheric parameters derived from ME inversions of
high-spatial resolution profiles are reasonably accurate and can be
used for statistical analyses of solar magnetic fields, even if the
fit is not always good. We also show that the ME inferences cannot be
assigned to a specific atmospheric layer: different parameters sample
different ranges of optical depths, and even the same parameter
may trace different layers depending on the physical conditions
of the atmosphere. Despite this variability, ME inversions tend
to probe deeper layers in granules than in intergranular lanes. Figure 10 and appendix are only available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>

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Title: Explanation of the Sea-serpent Magnetic Structure of Sunspot
Penumbrae
Authors: Kitiashvili, I. N.; Bellot Rubio, L. R.; Kosovichev, A. G.;
Mansour, N. N.; Sainz Dalda, A.; Wray, A. A.
2010ApJ...716L.181K Altcode: 2010arXiv1003.0049K
Recent spectro-polarimetric observations of a sunspot showed the
formation of bipolar magnetic patches in the mid-penumbra and their
propagation toward the outer penumbral boundary. The observations
were interpreted as being caused by sea-serpent magnetic fields near
the solar surface. In this Letter, we develop a three-dimensional
radiative MHD numerical model to explain the sea-serpent structure
and the wave-like behavior of the penumbral magnetic field lines. The
simulations reproduce the observed behavior, suggesting that the
sea-serpent phenomenon is a consequence of magnetoconvection in
a strongly inclined magnetic field. It involves several physical
processes: filamentary structurization, high-speed overturning
convective motions in strong, almost horizontal magnetic fields with
partially frozen field lines, and traveling convective waves. The
results demonstrate a correlation of the bipolar magnetic patches with
high-speed Evershed downflows in the penumbra. This is the first time
that a three-dimensional numerical model of the penumbra results in
downward-directed magnetic fields, an essential ingredient of sunspot
penumbrae that has eluded explanation until now.

---------------------------------------------------------
Title: Sea-Serpent Magnetic Structure of Sunspot Penumbrae:
Observations and MHD Simulations
Authors: Kitiashvili, Irina; Bellot Rubio, L. R.; Kosovichev, A. G.;
Mansour, N. N.; Sainz Dalda, A.; Wray, A. A.
2010AAS...21631706K Altcode: 2010BAAS...41..899K
Recent high-resolution spectro-polarimetric observations of a sunspot
detected formation of bipolar magnetic patches in the mid penumbra and
propagation of these patches toward the outer penumbral boundary. The
observations have been interpreted as an evidence of sea-serpent field
lines near the solar surface. Using a radiative 3D MHD code, we model
the behavior of solar magnetoconvection in strongly inclined magnetic
field of penumbra. The numerical simulation results reproduce the
moving bipolar magnetic elements observed in high-resolution SOHO/MDI
and Hinode/SOT data and also their physical properties, supporting the
sea-serpent model. The simulations explain the sea-serpent structure
and dynamics of the penumbral field as a consequence of turbulent
magnetoconvection in a highly inclined, strong magnetic field,
which forms filamentary structures and has properties of traveling
convective wave. The model also shows that the appearance of the
sea-serpent magnetic field lines is closely related to high-speed
patches ("Evershed clouds") of the penumbra radial outflow.

---------------------------------------------------------
Title: Small Magnetic Loops Connecting the Quiet Surface and the
Hot Outer Atmosphere of the Sun
Authors: Martínez González, M. J.; Manso Sainz, R.; Asensio Ramos,
A.; Bellot Rubio, L. R.
2010ApJ...714L..94M Altcode: 2010arXiv1003.1255M
Sunspots are the most spectacular manifestation of solar magnetism,
yet 99% of the solar surface remains "quiet" at any time of the solar
cycle. The quiet sun is not void of magnetic fields, though; they
are organized at smaller spatial scales and evolve relatively fast,
which makes them difficult to detect. Thus, although extensive quiet
Sun magnetism would be a natural driver to a uniform, steady heating of
the outer solar atmosphere, it is not clear what the physical processes
involved would be, due to lack of observational evidence. We report on
the topology and dynamics of the magnetic field in very quiet regions of
the Sun from spectropolarimetric observations of the Hinode satellite,
showing a continuous injection of magnetic flux with a well-organized
topology of Ω-loop from below the solar surface into the upper
layers. At first stages, when the loop travels across the photosphere,
it has a flattened (staple-like) geometry and a mean velocity ascent
of ~3 km s-1. When the loop crosses the minimum temperature
region, the magnetic fields at the footpoints become almost vertical and
the loop topology resembles a potential field. The mean ascent velocity
at chromospheric height is ~12 km s-1. The energy input rate
of these small-scale loops in the lower boundary of the chromosphere
is (at least) of 1.4 × 106-2.2 × 107 erg
cm-2 s-1. Our findings provide empirical evidence
for solar magnetism as a multi-scale system, in which small-scale
low-flux magnetism plays a crucial role, at least as important as active
regions, coupling different layers of the solar atmosphere and being
an important ingredient for chromospheric and coronal heating models.

---------------------------------------------------------
Title: Scattering Polarization in the Fe I 630 nm Emission Lines at
the Extreme Limb of the Sun
Authors: Lites, B. W.; Casini, R.; Manso Sainz, R.; Jurčák, J.;
Ichimoto, K.; Ishikawa, R.; Okamoto, T. J.; Tsuneta, S.; Bellot
Rubio, L.
2010ApJ...713..450L Altcode:
Spectro-polarimetric observations with the Solar Optical Telescope
onboard Hinode reveal the emission spectrum of the Fe I 630 nm lines
at the solar limb. The emission shell extends for less than 1” thereby
making it extremely difficult to detect from ground-based observatories
viewing the limb through the Earth's atmosphere. The linear polarization
signal is clearly due to scattering and it is predominantly oriented
in the radial direction. Using a comprehensive atomic model of
iron, we are able to interpret qualitatively the observed signals,
including the radial orientation of the linear polarization. The Hanle
effect causes the linear polarization of the Fe I 630 nm lines to be
sensitive to magnetic fields between ~0.1 G and ~40 G, and also to
be sensitive to the field's topology for stronger fields. The overall
degree of observed polarization can be reproduced by randomly oriented
horizontal magnetic fields of strength ≈2 G. The discovery of their
scattering polarization signals thus opens a new diagnostic opportunity
for these lines.

---------------------------------------------------------
Title: Downflows in Sunspot Umbral Dots
Authors: Ortiz, A.; Bellot Rubio, L. R.; Rouppe van der Voort, L.
2010ApJ...713.1282O Altcode: 2010arXiv1003.1897O
We study the velocity field of umbral dots (UDs) at a resolution
of 0farcs14. Our analysis is based on full Stokes measurements of a
pore taken with the Crisp Imaging Spectro-Polarimeter at the Swedish
1 m Solar Telescope. We determine the flow velocity at different
heights in the photosphere from a bisector analysis of the Fe I 630 nm
lines. In addition, we use the observed Stokes Q, U, and V profiles
to characterize the magnetic properties of these structures. We find
that most UDs are associated with strong upflows in deep photospheric
layers. Some of them also show concentrated patches of downflows at
their edges, with sizes of about 0farcs25, velocities of up to 1000
m s-1, and enhanced net circular polarization signals. The
downflows evolve rapidly and have lifetimes of only a few minutes. These
results appear to validate numerical models of magnetoconvection in
the presence of strong magnetic fields.

---------------------------------------------------------
Title: The stochastic, intermittent nature of quiet Sun magnetism
Authors: Martinez González, M. J.; Manso Sainz, R.; López Ariste,
A.; Bellot Rubio, L. R.; Bianda, M.
2010iac..talk....1M Altcode: 2010iac..talk..153M
No abstract at ADS

---------------------------------------------------------
Title: On Spectropolarimetric Measurements with Visible Lines
Authors: del Toro Iniesta, J. C.; Orozco Suárez, D.; Bellot Rubio,
L. R.
2010ApJ...711..312D Altcode: 2010arXiv1001.3022D
The ability of new instruments for providing accurate inferences of
vector magnetic fields and line-of-sight velocities of the solar
plasma depends a great deal on the sensitivity to these physical
quantities of the spectral lines chosen to be measured. Recently,
doubts have been raised about visible Stokes profiles to provide
a clear distinction between weak fields and strong ones filling a
small fraction of the observed area. The goal of this paper is to
give qualitative and quantitative arguments that help in settling the
debate since several instruments that employ visible lines are either
operating or planned for the near future. The sensitivity of the Stokes
profiles is calculated through the response functions (RFs), for e.g.,
by Ruiz Cobo &amp; Del Toro Iniesta. Both theoretical and empirical
evidences are gathered in favor of the reliability of visible Stokes
profiles. The RFs are also used for estimating the uncertainties in
the physical quantities due to noise in observations. A useful formula
has been derived that takes into account the measurement technique
(number of polarization measurements, polarimetric efficiencies, and
number of wavelength samples), the model assumptions (number of free
parameters and the filling factor), and the radiative transfer (RFs). We
conclude that a scenario with a weak magnetic field can reasonably
be distinguished with visible lines from another with a strong field
but a similar Stokes V amplitude, provided that the Milne-Eddington
approximation is good enough to describe the solar atmosphere and the
polarization signal is at least 3 or 4 times larger than the typical
rms noise of 10-3 I c reached in the observations.

---------------------------------------------------------
Title: The Evershed Flow and the Brightness of the Penumbra
Authors: Bellot Rubio, L. R.
2010ASSP...19..193B Altcode: 2010ASSP...19..193R; 2010mcia.conf..193B; 2009arXiv0903.3619B
The Evershed flow is a systematic motion of gas that occurs in
the penumbra of all sunspots. Discovered in 1909, it still lacks a
satisfactory explanation. We know that the flow is magnetized, often
supersonic, and that it shows conspicuous fine structure on spatial
scales of 0.2″-0.3″, but its origin remains unclear. The hope
is that a good observational understanding of the relation between
the flow and the penumbral magnetic field will help us determine its
nature. Here I review advances in the characterization of the Evershed
flow and sunspot magnetic fields from high-resolution spectroscopic
and spectropolarimetric measurements. Using this information as input
for 2D heat transfer simulations, it has been demonstrated that hot
Evershed upflows along nearly horizontal field lines are capable of
explaining one of the most intriguing aspects of sunspots: the surplus
brightness of the penumbra relative to the umbra. They also explain
the existence of penumbral filaments with dark cores. These results
support the idea that the Evershed flow is largely responsible for
the transport of energy in the penumbra.

---------------------------------------------------------
Title: Structure and Dynamics of Penumbral Filaments
Authors: Ruiz Cobo, B.; Bellot Rubio, L. R.
2010ASSP...14..461R Altcode: 2010hsa5.conf..461R; 2010ASSP...14..461C; 2008arXiv0810.2463R
High-resolution observations of sunspots have revealed the existence
of dark cores inside the bright filaments of the penumbra. Here we
present the stationary solution of the heat transfer equation in a
stratified penumbra consisting of nearly horizontal magnetic flux
tubes embedded in a stronger and more vertical field. The tubes and
the external medium are in horizontal mechanical equilibrium. This
model produces bright filaments with dark cores as a consequence of
the higher density of the plasma inside the flux tube, which shifts
the surface of optical depth unity toward higher (cooler) layers. Our
results suggest that the surplus brightness of the penumbra is a natural
consequence of the Evershed flow, and that magnetic flux tubes about
250 km in diameter can explain the morphology of sunspot penumbra.

---------------------------------------------------------
Title: High-resolution observations of interactions during the
emergence of magnetic flux from the photosphere to the corona
Authors: Guglielmino, S. L.; Bellot Rubio, L. R.; Zuccarello, F.;
Romano, P.; Vargas Domínguez, S.
2010MSAIS..14..184G Altcode:
Interactions occurring at sites where new flux emerges and an
old flux system is already present can trigger various phenomena,
such as flux cancellation, reconnection events, and even flaring. We
analyze high-resolution observations of a small-scale flux emergence
event in NOAA 10971, observed simultaneously by the Hinode satellite
and the Swedish Solar Telescope in La Palma Island during a joint
campaign. G-band, Halpha , and Ca II H filtergrams were acquired
together with Fe I and Na I magnetograms. The data show that the
emerging region seen in the photosphere is associated with Ca II H
brightenings and a Halpha chromospheric surge. Moreover, EUV raster
scans and XRT filtergrams show cospatial brightenings. Comparing our
results with recent 3D simulations, we interpret our observations in the
context of the low-altitude magnetic reconnection model, suggesting
that interactions between the emerging flux and the pre-existing
magnetic field can explain the observed coupling.

---------------------------------------------------------
Title: Supersonic Downflows in a Sunspot Light Bridge
Authors: Louis, Rohan E.; Bellot Rubio, Luis R.; Mathew, Shibu K.;
Venkatakrishnan, P.
2009ApJ...704L..29L Altcode: 2009arXiv0908.3465L
We report the discovery of supersonic downflows in a sunspot light
bridge using measurements taken with the spectropolarimeter onboard
the Hinode satellite. The downflows occur in small patches close to
regions where the vector magnetic field changes orientation rapidly,
and are associated with anomalous circular polarization profiles. An
inversion of the observed Stokes spectra reveals velocities of up to
10 km s-1, making them the strongest photospheric flows
ever measured in light bridges. Some (but not all) of the downflowing
patches are cospatial and cotemporal with brightness enhancements in
chromospheric Ca II H filtergrams. We suggest that these flows are due
to magnetic reconnection in the upper photosphere/lower chromosphere,
although other mechanisms cannot be ruled out.

---------------------------------------------------------
Title: Emergence of Small-scale Magnetic Loops Through the Quiet
Solar Atmosphere
Authors: Martínez González, M. J.; Bellot Rubio, L. R.
2009ApJ...700.1391M Altcode: 2009arXiv0905.2691M
We investigate the emergence of magnetic flux in the quiet Sun
at very small spatial scales, focusing on the magnetic connection
between the photosphere and chromosphere. The observational data
consist of spectropolarimetric measurements and filtergrams taken
with the Hinode satellite and the Dutch Open Telescope. We find that
a significant fraction of the magnetic flux present in internetwork
regions appears in the form of Ω-shaped loops. The emergence rate
is 0.02 loops per hour and arcsec-2, which brings 1.1
× 1012 Mx s-1 arcsec-2 of new
flux to the solar surface. Initially, the loops are observed as
small patches of linear polarization above a granular cell. Shortly
afterward, two footpoints of opposite polarity become visible in
circular polarization within or at the edges of the granule and start
moving toward the adjacent intergranular space. The orientation of the
footpoints does not seem to obey Hale's polarity rules. The loops are
continuously buffeted by convective motions, but they always retain a
high degree of coherence. Interestingly, 23% of the loops that emerge
in the photosphere reach the chromosphere (16 cases out of 69). They
are first detected in Fe I 630 nm magnetograms and 5 minutes later
in Mg I b 517.3 nm magnetograms. After about 8 minutes, some of them
are also observed in Ca II H line-core images, where the footpoints
produce small brightness enhancements.

---------------------------------------------------------
Title: Imaging Spectropolarimetry with IBIS: Evolution of Bright
Points in the Quiet Sun
Authors: Viticchié, B.; Del Moro, D.; Berrilli, F.; Bellot Rubio,
L.; Tritschler, A.
2009ApJ...700L.145V Altcode: 2009arXiv0906.2663V
We present the results from first spectropolarimetric observations
of the solar photosphere acquired at the Dunn Solar Telescope with
the Interferometric Bidimensional Spectrometer. Full Stokes profiles
were measured in the Fe I 630.15 nm and Fe I 630.25 nm lines with high
spatial and spectral resolutions for 53 minutes, with a Stokes V noise
of 3 × 10-3 the continuum intensity level. The data set
allows us to study the evolution of several magnetic features associated
with G-band bright points (BPs) in the quiet Sun. Here we focus on
the analysis of three distinct processes, namely the coalescence,
fragmentation, and cancellation of G-band BPs. Our analysis is
based on an SIR inversion of the Stokes I and V profiles of both Fe
I lines. The high spatial resolution of the G-band images combined
with the inversion results helps to interpret the undergoing physical
processes. The appearance (dissolution) of high-contrast G-band BPs is
found to be related to the local increase (decrease) of the magnetic
filling factor, without appreciable changes in the field strength. The
cancellation of opposite-polarity BPs can be the signature of either
magnetic reconnection or the emergence/submergence of magnetic loops.

---------------------------------------------------------
Title: Detection of Supersonic Horizontal Flows in the Solar
Granulation
Authors: Bellot Rubio, L. R.
2009ApJ...700..284B Altcode: 2009arXiv0905.3719B
Hydrodynamic simulations of granular convection predict the existence of
supersonic flows covering ~3%-4% of the solar surface at any time, but
these flows have not been detected unambiguously as yet. Using data from
the spectropolarimeter aboard the Hinode satellite, I present direct
evidence of fast horizontal plasma motions in quiet-Sun granules. Their
visibility increases toward the limb due to more favorable viewing
conditions. At the resolution of Hinode, the horizontal flows give rise
to asymmetric intensity profiles with very inclined blue wings and even
line satellites located blueward of the main absorption feature. Doppler
shifts of up to 9 km s-1 are observed at the edges of bright
granules, demonstrating that the flows reach supersonic speeds. The
strongest velocities occur in patches of 0farcs5 or less. They tend
to be associated with enhanced continuum intensities, line widths,
and equivalent widths, but large values of these parameters do not
necessarily imply the existence of supersonic flows. Time series
of spectropolarimetric measurements in regions away from the disk
center show the transient nature of the strong horizontal motions,
which last only for a fraction of the granule lifetime. Supersonic
flows are expected to produce shocks at the boundaries between granules
and intergranular lanes, and may also play a role in the emergence of
small-scale magnetic fields in quiet-Sun internetwork regions.

---------------------------------------------------------
Title: Observations of small-scale flux evolution with HINODE
Authors: Guglielmino, S. L.; Romano, P.; Zuccarello, F.; Bellot Rubio,
L. R.
2009MmSAI..80..278G Altcode:
We present observations of NOAA 10971 acquired by the Solar
Optical Telescope onboard the HINODE satellite. We have inverted
spectropolarimetric data of SOT/SP along Fe I doublet at 630.15 nm
and 630.25 nm, using the SIR inversion code in order to get magnetic
field strength, inclination, azimuth, Doppler velocity and temperature
from the observed Stokes profiles. We compare these first results with
SOT/FG broad-band observations in the Ca II H line (396.85 ± 0.3 nm)
and G-band (430.5 ±± 0.8 nm), and with magnetograms obtained from the
narrow-band shuttered Stokes I and V in the wings of the Na I D1 line
(589.6 nm). Small-scale events of flux emergence and flux cancellation
have been singled out.

---------------------------------------------------------
Title: Hinode Observations of Chromospheric Brightenings in the Ca
II H Line during Small-Scale Flux Emergence Events
Authors: Guglielmino, S. L.; Zuccarello, F.; Romano, P.; Bellot Rubio,
L. R.
2008ApJ...688L.111G Altcode: 2008arXiv0810.2494G
Ca II H emission is a well-known indicator of magnetic activity in
the Sun and other stars. It is also viewed as an important signature
of chromospheric heating. However, the Ca II H line has not been
used as a diagnostic of magnetic flux emergence from the solar
interior. Here we report on Hinode observations of chromospheric Ca II
H brightenings associated with a repeated, small-scale flux emergence
event. We describe this process and investigate the evolution of
the magnetic flux, G-band brightness, and Ca II H intensity in the
emerging region. Our results suggest that energy is released in the
chromosphere as a consequence of interactions between the emerging
flux and the preexisting magnetic field, in agreement with recent 3D
numerical simulations.

---------------------------------------------------------
Title: Chromospheric Brightenings during Small-scale Flux Emergence
Events
Authors: Guglielmino, S. L.; Zuccarello, F.; Romano, P.; Bellot Rubio,
L. R.
2008ESPM...12.2.46G Altcode:
We present multi-wavelength high-resolution observations of active
region NOAA 10971, performed by the Solar Optical Telescope aboard
the Hinode satellite. Small-scale events of flux emergence occurring
in this region have been singled out. In particular, we report
observations of chromospheric Ca II H brightenings associated with a
repeated emergence event. We describe this process and investigate
the evolution of the magnetic flux, G-band brightness, and Ca II H
intensity in the emerging region. We compare these observations with
simultaneous spectropolarimetric measurements, using the SIR code to
retrieve the thermal, dynamical, and magnetic properties of the emerging
region. We discuss our results in the context of the chromospheric
heating problem. Magnetic reconnection between the emerging flux
and the pre-existing chromospheric field would be able to explain
the observed chromospheric brightness enhancements. The reconnection
releases energy, and this could be an efficient source of local heating
for the chromosphere, as suggested by recent 3D numerical simulations.

---------------------------------------------------------
Title: Heat transfer in sunspot penumbrae. Origin of dark-cored
penumbral filaments
Authors: Ruiz Cobo, B.; Bellot Rubio, L. R.
2008A&A...488..749R Altcode: 2008arXiv0806.0804R
Context: Observations at 0.1 arcsec have revealed the existence of
dark cores in the bright filaments of sunspot penumbrae. Expectations
are high that such dark-cored filaments are the basic building blocks
of the penumbra, but their nature remains unknown. Aims: We
investigate the origin of dark cores in penumbral filaments and the
surplus brightness of the penumbra. To that end we use an uncombed
penumbral model. Methods: The 2D stationary heat transfer equation
is solved in a stratified atmosphere consisting of nearly horizontal
magnetic flux tubes embedded in a stronger and more vertical field. The
tubes carry an Evershed flow of hot plasma. Results: This model
produces bright filaments with dark cores as a consequence of the higher
density of the plasma inside the tubes, which shifts the surface of
optical depth unity toward higher (cooler) layers. Our calculations
suggest that the surplus brightness of the penumbra is a natural
consequence of the Evershed flow, and that magnetic flux tubes about
250 km in diameter can explain the morphology of sunspot penumbrae.

---------------------------------------------------------
Title: Solar spectropolarimetry at high spatial resolution: Quiet-Sun
magnetic fields
Authors: Bellot Rubio, L. R.; Borrero, J. M.
2008ESPM...12..2.4B Altcode:
Spectropolarimetry permits quantitative inferences of solar magnetic
fields to be carried out. It is in fact the only means at our disposal
to characterize the physical properties of small magnetic structures
from low spatial-resolution observations. The accuracy of the results
derived from spectropolarimetric measurements has improved dramatically
with the advent of simultaneous observations in different spectral
regions and high angular resolution measurements. The main advantage
brought about by high spatial resolution is that there is less need
to model complex scenarios involving different fields and/or flows
coexisting in the pixel. Currently it is possible to achieve resolutions
of 0.3 arcsec from space (with the Hinode satellite) and 0.15 arcsec
from the ground (with the 1-m Swedish Solar Telescope). In this talk
we will show examples of high spatial resolution spectropolarimetric
observations and how they are challenging our understanding of quiet
Sun magnetic fields and sunspot penumbrae. In addition, we will
describe previously unknown issues that affect diffraction-limited
observations. Proper interpretations of the measurements require these
effects to be taken into account.

---------------------------------------------------------
Title: Erratum: The Analysis of Penumbral Fine Structure Using an
Advanced Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
2008PASJ...60..933J Altcode:
In the article [PASJ 59, S601-S606 (2007)], the word ”CSIC” was
omitted from the affiliation of Dr. Luis Bellot Rubio. The correct
affiliation is : 2Instituto de Astrofísica de Andalucía
(CSIC), Apdo. de Correos 3004, 18080 Granada, Spain

---------------------------------------------------------
Title: Detection of sea-serpent field lines in sunspot penumbrae
Authors: Sainz Dalda, A.; Bellot Rubio, L. R.
2008A&A...481L..21S Altcode: 2007arXiv0712.2983S
Aims:We investigate the spatial distribution of magnetic polarities
in the penumbra of a spot observed very close to disk center. Methods: High angular and temporal resolution magnetograms taken with
the Narrowband Filter Imager aboard Hinode are used in this study. They
provide continuous and stable measurements in the photospheric Fe I
630.25 line for long periods of time. Results: Our observations
show small-scale, elongated, bipolar magnetic structures that appear in
the mid penumbra and move radially outward. They occur in between the
more vertical fields of the penumbra, and can be associated with the
horizontal fields that harbor the Evershed flow. Many of them cross
the outer penumbral boundary, becoming moving magnetic features in
the sunspot moat. We determine the properties of these structures,
including their sizes, proper motions, footpoint separation, and
lifetimes. Conclusions: The bipolar patches can be interpreted
as being produced by sea-serpent field lines that originate in the mid
penumbra and eventually leave the spot in the form moving magnetic
features. The existence of such field lines has been inferred from
Stokes inversions of spectropolarimetric measurements at lower angular
resolution, but this is the first time they are imaged directly. Our
observations add another piece of evidence in favor of the uncombed
structure of penumbral magnetic fields. A movie is only available
in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: Magnetic field emergence in quiet Sun granules
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.; Tsuneta, S.
2008A&A...481L..33O Altcode: 2007arXiv0712.2663O
Aims:We describe a new form of small-scale magnetic flux emergence in
the quiet Sun. This process seems to take vertical magnetic fields
from subsurface layers to the photosphere, where they appear above
granular convection cells. Methods: High-cadence time series
of spectropolarimetric measurements obtained by Hinode in a quiet
region near disk center are analyzed. We extract line parameters from
the observed Stokes profiles and study their evolution with time. Results: The circular polarization maps derived from the observed Fe
I 630 nm lines show clear magnetic signals emerging at the center of
granular cells. We do not find any evidence for linear polarization
signals associated with these events. The magnetic flux patches grow
with time, occupying a significant fraction of the granular area. The
signals then fade until they disappear completely. The typical lifetime
of these events is of the order of 20 min. No significant changes in
the chromosphere are seen to occur in response to the emergence, as
revealed by co-spatial Ca II H filtergrams. The Stokes I and V profiles
measured in the emerging flux concentrations show strong asymmetries
and Doppler shifts. Conclusions: The origin of these events is
unclear at present, but we suggest that they may represent the emergence
of vertical fields lines from the bottom of the photosphere, possibly
dragged by the convective upflows of granules. Preliminary inversions
of the Stokes spectra indicate that this scenario is compatible with
the observations, although the emergence of vertical field lines is
not free from conceptual problems.

---------------------------------------------------------
Title: Formation of Solar Magnetic Flux Tubes with Kilogauss Field
Strength Induced by Convective Instability
Authors: Nagata, Shin'ichi; Tsuneta, Saku; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Katsukawa, Yukio; Shimizu, Toshifumi; Yokoyama,
Takaaki; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.;
Berger, Thomas E.; Title, Alan M.; Bellot Rubio, Luis R.; Orozco
Suárez, David
2008ApJ...677L.145N Altcode:
Convective instability has been a mechanism used to explain
the formation of solar photospheric flux tubes with kG field
strength. However, the turbulence of the Earth's atmosphere has
prevented ground-based observers from examining the hypothesis
with precise polarimetric measurement on the subarcsecond scale
flux tubes. Here we discuss observational evidence of this scenario
based on observations with the Solar Optical Telescope (SOT) aboard
Hinode. The cooling of an equipartition field strength flux tube
precedes a transient downflow reaching 6 km s-1 and the
intensification of the field strength to 2 kG. These observations
agree very well with the theoretical predictions.

---------------------------------------------------------
Title: Penumbral models in the light of Hinode spectropolarimetric
observations
Authors: Jurčák, J.; Bellot Rubio, L. R.
2008A&A...481L..17J Altcode: 2007arXiv0711.1692J
Aims:The realism of current models of the penumbra is assessed
by comparing their predictions with the plasma properties
of penumbral filaments as retrieved from spectropolarimetric
observations. Methods: The spectropolarimeter onboard Hinode
allows us, for the first time, to distinguish the fine structure
of the penumbra. Therefore, we can use one-component inversions to
obtain the stratifications of plasma parameters in each pixel. The
correlations between the plasma parameters and the continuum intensity
are studied. Results: We find that, in the outer penumbra,
the stronger flows and higher values of magnetic field inclination
tend to be located in dark filaments. This finding does not seem to
be compatible with the scenario of a field-free gappy penumbra.

---------------------------------------------------------
Title: Spectropolarimetry of a Decaying Sunspot Penumbra
Authors: Bellot Rubio, L. R.; Tritschler, A.; Martínez Pillet, V.
2008ApJ...676..698B Altcode: 2007arXiv0712.2937B
We report on high angular resolution, high-precision spectropolarimetric
measurements of a decaying sunspot. The spot gradually lost
its penumbra during the course of 3 days. In the late stages of
evolution, where the only remnant of the spot is a naked umbra, we
find small-scale inhomogeneities in the magnetic canopy surrounding
it. The inhomogeneities are observed as finger-like structures
of weak and nearly horizontal magnetic fields extending 1”-2”
from the border of the umbra. These fields are not associated with
filamentary structures in continuum intensity or with conspicuous
Evershed flows. The Stokes profiles emerging from the fingers exhibit
blueshifts, which we interpret as upward motions. This previously
unknown fine structure may be related to penumbral field lines that
no longer carry strong Evershed flows and rise to the chromosphere,
producing the disappearance of the penumbra at photospheric levels.

---------------------------------------------------------
Title: Temporal evolution of the Evershed flow in
sunspots. II. Physical properties and nature of Evershed clouds
Authors: Cabrera Solana, D.; Bellot Rubio, L. R.; Borrero, J. M.;
Del Toro Iniesta, J. C.
2008A&A...477..273C Altcode: 2007arXiv0709.1601C
Context: Evershed clouds (ECs) represent the most conspicuous
variation of the Evershed flow in sunspot penumbrae. Aims:
We determine the physical properties of ECs from high spatial and
temporal resolution spectropolarimetric measurements. This information
is used to investigate the nature of the EC phenomenon. Methods:
The Stokes profiles of four visible and three infrared spectral lines
are subject to inversions based on simple one-component models as well
as more sophisticated realizations of penumbral flux tubes embedded
in a static ambient field (uncombed models). Results: According
to the one-component inversions, the EC phenomenon can be understood
as a perturbation of the magnetic and dynamic configuration of the
penumbral filaments along which the ECs move. The uncombed inversions,
on the other hand, suggest that ECs are the result of enhancements
in the visibility of penumbral flux tubes. We conjecture that
these enhancements are caused by a perturbation of the thermodynamic
properties of the tubes, rather than by changes in the vector magnetic
field. This mechanism is investigated performing numerical experiments
of thick penumbral tubes in mechanical equilibrium with a background
field. Conclusions: While the one-component inversions confirm
many of the properties indicated by a simple line parameter analysis
(Paper I of this series), we give more credit to the results of the
uncombed inversions because they take into account, at least in an
approximate manner, the fine structure of the penumbra. Appendix
A is only available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: Temporal evolution of the Evershed flow in
sunspots. I. Observational characterization of Evershed clouds
Authors: Cabrera Solana, D.; Bellot Rubio, L. R.; Beck, C.; Del Toro
Iniesta, J. C.
2007A&A...475.1067C Altcode: 2007arXiv0707.2629C
Context: The magnetic and kinematic properties of the photospheric
Evershed flow are relatively well known, but not completely
understood. The evolution of the flow with time, which is mainly due
to the appearance of velocity packets called Evershed clouds (ECs),
may provide information to further constrain its origin. Aims:
We undertake a detailed analysis of the evolution of the Evershed flow
by studying the properties of ECs. In this first paper we determine
the sizes, proper motions, location in the penumbra, and frequency
of appearance of ECs, as well as their typical Doppler velocities,
linear and circular polarization signals, Stokes V area asymmetries,
and continuum intensities. Methods: High-cadence, high-resolution,
full vector spectropolarimetric measurements in visible and infrared
lines are used to characterize the EC phenomenon through a simple
line-parameter analysis. Results: ECs appear in the mid penumbra
and propagate outward along filaments having large linear polarization
signals and enhanced Evershed flows. The frequency of appearance of
ECs varies between 15 and 40 min in different filaments. ECs exhibit
the largest Doppler velocities and linear-to-circular polarization
ratios of the whole penumbra. In addition, lines formed deeper in the
atmosphere show larger Doppler velocities, much in the same way as
the “quiescent” Evershed flow. According to our observations, ECs
can be classified in two groups: type I ECs, which vanish in the outer
penumbra, and type II ECs, which cross the outer penumbral boundary and
enter the sunspot moat. Most of the observed ECs belong to type I. On
average, type II ECs can be detected as velocity structures outside
of the spot for only about 14 min. Their proper motions in the moat
are significantly reduced with respect to the ones they had in the
penumbra. Appendices A and B are only available in electronic
form at http://www.aanda.org

---------------------------------------------------------
Title: Quiet-Sun Internetwork Magnetic Fields from the Inversion of
Hinode Measurements
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.; Tsuneta, S.; Lites, B. W.; Ichimoto, K.; Katsukawa, Y.; Nagata,
S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
2007ApJ...670L..61O Altcode: 2007arXiv0710.1405O
We analyze Fe I 630 nm observations of the quiet Sun at disk center
taken with the spectropolarimeter of the Solar Optical Telescope aboard
the Hinode satellite. A significant fraction of the scanned area,
including granules, turns out to be covered by magnetic fields. We
derive field strength and inclination probability density functions from
a Milne-Eddington inversion of the observed Stokes profiles. They show
that the internetwork consists of very inclined, hG fields. As expected,
network areas exhibit a predominance of kG field concentrations. The
high spatial resolution of Hinode's spectropolarimetric measurements
brings to an agreement the results obtained from the analysis of
visible and near-infrared lines.

---------------------------------------------------------
Title: Strategy for the Inversion of Hinode Spectropolarimetric
Measurements in the Quiet Sun
Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro
Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
2007PASJ...59S.837O Altcode: 2007arXiv0709.2033O
In this paper we propose an inversion strategy for the analysis of
spectropolarimetric measurements taken by Hinode in the quiet Sun. The
Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records
the Stokes spectra of the FeI line pair at 630.2nm with unprecendented
angular resolution, high spectral resolution, and high sensitivity. We
discuss the need to consider a local stray-light contamination to
account for the effects of telescope diffraction. The strategy is
applied to observations of a wide quiet Sun area at disk center. Using
these data we examine the influence of noise and initial guess models
in the inversion results. Our analysis yields the distributions of
magnetic field strengths and stray-light factors. They show that quiet
Sun internetwork regions consist mainly of hG fields with stray-light
contamination of about 0.8.

---------------------------------------------------------
Title: The Analysis of Penumbral Fine Structure Using an Advanced
Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
2007PASJ...59S.601J Altcode: 2007arXiv0707.1560J
We present a method to study the penumbral fine structure using data
obtained by the spectropolarimeter on board Hinode. For the first
time, the penumbral filaments can be considered as being resolved in
spectropolarimetric measurements. This enables us to use inversion
codes with only one-component model atmospheres, and thus to assign
the obtained stratifications of the plasma parameters directly to the
penumbral fine structure. This approach was applied to the limb-side
part of the penumbra in the active region NOAA10923. Preliminary results
show a clear dependence of the plasma parameters on the continuum
intensity in the inner penumbra, i.e., a weaker and horizontal magnetic
field along with an increased line-of-sight velocity are found in the
low layers of the bright filaments. The results in the mid penumbra
are ambiguous, and future analyses are necessary to unveil the magnetic
field structure and other plasma parameters there.

---------------------------------------------------------
Title: Vector Spectropolarimetry of Dark-cored Penumbral Filaments
with Hinode
Authors: Bellot Rubio, L. R.; Tsuneta, S.; Ichimoto, K.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.; del Toro Iniesta, J. C.
2007ApJ...668L..91B Altcode: 2007arXiv0708.2791B
We present spectropolarimetric measurements of dark-cored penumbral
filaments taken with Hinode at a resolution of 0.3". Our observations
demonstrate that dark-cored filaments are more prominent in polarized
light than in continuum intensity. Far from disk center, the Stokes
profiles emerging from these structures are very asymmetric and show
evidence for magnetic fields of different inclinations along the
line of sight, together with strong Evershed flows of at least 6-7 km
s-1. In sunspots closer to disk center, dark-cored penumbral
filaments exhibit regular Stokes profiles with little asymmetries due
to the vanishing line-of-sight component of the horizontal Evershed
flow. An inversion of the observed spectra indicates that the magnetic
field is weaker and more inclined in the dark cores as compared with
the surrounding bright structures. This is compatible with the idea
that dark-cored filaments are the manifestation of flux tubes carrying
hot Evershed flows.

---------------------------------------------------------
Title: Flux Tubes as the Origin of Net Circular Polarization in
Sunspot Penumbrae
Authors: Borrero, J. M.; Bellot Rubio, L. R.; Müller, D. A. N.
2007ApJ...666L.133B Altcode: 2007arXiv0707.4145B
We employ a three-dimensional magnetohydrostatic model of a
horizontal flux tube, embedded in a magnetic surrounding atmosphere,
to successfully reproduce the azimuthal and center-to-limb variations
of the net circular polarization observed in sunspot penumbrae. This
success is partly due to the realistic modeling of the interaction
between the flux tube and the surrounding magnetic field.

---------------------------------------------------------
Title: Magnetic properties of G-band bright points in a sunspot moat
Authors: Beck, C.; Bellot Rubio, L. R.; Schlichenmaier, R.;
Sütterlin, P.
2007A&A...472..607B Altcode: 2007arXiv0707.1232B
We present simultaneous spectropolarimetric observations of four
visible (630 nm) and three infrared (1565 nm) spectral lines from the
German Vacuum Tower Telescope, together with speckle-reconstructed
filtergrams in the G-band and the Ca II H line core from the Dutch
Open Telescope. After alignment of the data sets, we used the G-band
intensity to locate bright points (BPs) in the moat of a regular
sunspot. With the cospatial and cotemporal information provided by the
polarimetric data, we characterize the magnetic, kinematic, and thermal
properties of the BPs. We find that (a) 94% of the BPs are associated
with magnetic fields; (b) their field strengths range between 500 and
1400 G, with a rather flat distribution; (c) the contrast of BPs in the
G-band depends on the angle between the vector magnetic field and the
line of sight; (d) the BPs harbor downflows of magnetized plasma and
exhibit Stokes V profiles with large area and amplitude asymmetries;
(e) the magnetic interior of BPs is hotter than the immediate field-free
surroundings by about 1000 K at equal optical depth; and (f) the mean
effective diameter of BPs in our data set is 150 km, with very few
BPs larger than 300 km. Most of these properties can be explained
by the classical magnetic flux tube model. However, the wide range
of BP parameters found in this study indicates that not all G-band
BPs are identical to stable long-lived flux tubes or sheets of kG
strength. Appendices A-C are only available in electronic form
at http://www.aanda.org

---------------------------------------------------------
Title: Quiet-Sun Magnetic Fields from Space-borne Observations:
Simulating Hinode's Case
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.
2007ApJ...662L..31O Altcode: 2007arXiv0705.0096O
We examine whether it is possible to derive the field strength
distribution of quiet-Sun internetwork regions from very high spatial
resolution polarimetric observations in the visible. In particular,
we consider the case of the spectropolarimeter attached to the Solar
Optical Telescope aboard Hinode. Radiative magnetoconvection simulations
are used to synthesize the four Stokes profiles of the Fe I 630.2
nm lines. Once the profiles are degraded to a spatial resolution of
0.32" and added noise, we infer the atmospheric parameters by means
of Milne-Eddington inversions. The comparison of the derived values
with the real ones indicates that the visible lines yield correct
internetwork field strengths and magnetic fluxes, with uncertainties
smaller than ~150 G, when a stray-light contamination factor is
included in the inversion. Contrary to the results of ground-based
observations at 1", weak fields are retrieved wherever the field is
weak in the simulation.

---------------------------------------------------------
Title: Multi-wavelength observations at the German VTT on Tenerife
Authors: Beck, C.; Mikurda, K.; Bellot Rubio, L. R.; Kentischer, T.;
Collados, M.
2007msfa.conf...55B Altcode:
To study the small-scale dynamic processes of magneto-convection in the
solar photosphere in more detail than currently achieveable, not only
the spatial resolution has to be increased, but also the information
content of observations. In order to do so, several wavelengths and
spectral lines must be observed simultaneously. This is often achieved
by coordinated campaigns at several telescopes with different post-focus
instrumentation. The German Vacuum Tower Telescope (VTT) on Tenerife
offers the possibility to operate several dedicated instruments
spectrometers, polarimeters, imaging systems at the same time. We
describe some of the possible combinations of post-focus instruments,
and present examples of multi-wavelength data obtained recently.

---------------------------------------------------------
Title: S im ulation And Analysis Of VIM Measurements: Feedback On
Design Parameters
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Vargas, S.; Bonet,
J. A.; Martíez Pillet, V.; del Toro Iniesta, J. C.
2007ESASP.641E..49O Altcode: 2006astro.ph.11443O
The Visible-light Imager and Magnetograph (VIM) proposed for the
ESA Solar Orbiter mission will observe a photo spheric spectral
line at high spatial resolution. Here we simulate and interpret VIM
measurements. Realistic MHD models are used to synthesize "observed"
Stokes profiles of the photospheric Fe I 617.3 nm line. The profiles are
degraded by telescope diffraction and detector pixel size to a spatial
resolution of 162 km on the solar surface. We stufy the influence
of spectral resolving power, noise, and limited wavelength sampling
on the vector magnetic fields and line-of-sight velocities derived
from Milne-Eddington inversions of the simulated measurements. VIM
will provide reasonably accurate values of the atmospheric parametes
even with the filter widths of 120 Å and 3 wavelength positions plus
continuum, as long as the noise level is kept below 10-3 Ic.

---------------------------------------------------------
Title: A Look into the Guts of Sunspots
Authors: Bellot Rubio, L. R.
2007hsa..conf..271B Altcode: 2006astro.ph.11471B
Advances in instrumentation have made it possible to study sunspots with
unprecedented detail. New capabilities include imaging observations
at a resolution of 0.1" (70 km on the sun), spectroscopy at ~0.2",
and simultaneous spectropolarimetry in visible and infrared lines at
resolutions well below 1". In spite of these advances, we still have
not identified the building blocks of the penumbra and the mechanism
responsible for the Evershed flow. Three different models have been
proposed to explain the corpus of observations gathered over the
years. The strengths and limitations of these models are reviewed in
this contribution.

---------------------------------------------------------
Title: Magnetic properties of G-band bright points
Authors: Beck, C.; Mikurda, K.; Bellot Rubio, L. R.; Schlichenmaier,
R.; Sütterlin, P.
2007msfa.conf..165B Altcode:
Bright points (BPs) visible in the G band at 430 nm are commonly used
as tracers of magnetic fields, indicating the location of kG flux
concentrations. To study the actual magnetic properties of G-band BPs,
we took observations in 2003 and 2005, employing simultaneously a
speckle setup in the G band and vector spectropolarimetry to derive
the magnetic field vector. From the analysis of the co-aligned
polarimetric data we find that the BPs show a broad range of field
strengths, magnetic fluxes, and field inclinations. Many G-band
BPs are not co-spatial with the central part of the nearby flux
concentrations. Even at the small heliocentric angle of only 12°,
the BPs appear projected on adjacent granules, whereas the magnetic
field is concentrated in the intergranular lanes. Our findings support
the view that the G-band BPs are a result of the "hot wall effect". The
downward shift of the optical depth scale in the presence of magnetic
fields allows to see deeper and hotter layers in the hot granules next
to the field concentrations, where CH dissociates. Thus, information
drawn from imaging observations of BPs has limited use to investigate
the actual magnetic field structure, when the BPs are not co-spatial
with the central part of the flux concentrations.

---------------------------------------------------------
Title: Polarimetric Observations of the Formation of a G-Band
Bright Point
Authors: Beck, C.; Schmidt, W.; Bellot Rubio, L. R.; Schlichenmaier,
R.; Sütterlin, P.; Lites, B. W.
2006ASPC..358...72B Altcode:
We investigate the kinematic and magnetic properties of G-band bright
points in the moat of a regular sunspot. The analysis is based on vector
polarimetric measurements made at the German Vacuum Tower Telescope in
visible (630 nm) and infrared (1565 nm) spectral lines, complemented
by high-resolution filtergrams in the G-band at 430.6 nm and the core
of the Ca II H line at 396.7 nm from the Dutch Open Telescope. The
spectro-polarimetric data has been inverted to derive the magnetic
field properties of the observed region. We witness the formation of a
G-band bright point from a patch of diffuse flux with an initial field
strength of 0.4 kG. The magnetic field strength increases to 0.9 kG in
the course of several minutes, accompanied by a downflow of magnetized
plasma. A few minutes after the field intensification, a G-band bright
point is seen at the location of the flux concentration. The formation
of the bright point shows the signatures of convective collapse.

---------------------------------------------------------
Title: Stokes Inversion Techniques: Recent Advances and New Challenges
Authors: Bellot Rubio, L. R.
2006ASPC..358..107B Altcode: 2006astro.ph..1483B
Inversion techniques (ITs) allow us to infer the magnetic, dynamic,
and thermal properties of the solar atmosphere from polarization
line profiles. In recent years, major progress has come from the
application of ITs to state-of-the-art observations. This paper
summarizes the main results achieved both in the photosphere and in the
chromosphere. It also discusses the challenges facing ITs in the near
future. Understanding the limitations of spectral lines, implementing
more complex atmospheric models, and devising efficient strategies of
data analysis for upcoming ground-based and space-borne instruments, are
among the most important issues that need to be addressed. It is argued
that proper interpretations of diffraction-limited Stokes profiles will
not be possible without accounting for gradients of the atmospheric
parameters along the line of sight. The feasibility of determining
gradients in real time from space-borne observations is examined.

---------------------------------------------------------
Title: First Steps Towards the Electronic Inversion of the Radiative
Transfer Equation
Authors: Castillo Lorenzo, J. L.; Orozco Suárez, D.; Bellot Rubio,
L. R.; Jiménez, L.; Del Toro Iniesta, J. C.
2006ASPC..358..177C Altcode:
The radiative transfer equation (RTE) gives us information about how the
light streams through the medium. It must be inverted in order to obtain
the properties of the medium that generated the observation. While
there are a number of well discussed methods to approach the solution
of the inversion, none of them is suitable for the real-time analysis
of high-resolution images due to their computational requirements. This
document introduces an electronic inverter for the RTE, suitable for
real-time inversion and mainly intended for space missions and on-line
ground-based observations.

---------------------------------------------------------
Title: Inversion of Visible and IR Stokes Profiles in Sunspots
Authors: Cabrera Solana, D.; Bellot Rubio, L. R.; Beck, C.; Del Toro
Iniesta, J. C.
2006ASPC..358...25C Altcode:
We present an analysis of simultaneous observations of a sunspot
in two different spectral ranges (630 nm and 1565 nm). The dataset
was acquired with the POlarimetric LIttrow Spectrograph (POLIS) and
the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower
Telescope (VTT) of Observatorio del Teide. Inversions of both sets
of lines are carried out to retrieve physical quantities such as
temperature and magnetic fields. We find that: a) the differences
between the atmospheric parameters inferred from the two ranges
are small, demonstrating that inversion techniques provide unique
results; b) there is a cross-talk between temperature and stray light
for visible lines; c) a more realistic treatment of the stray light
contamination is required. Making use of both visible and infrared
lines we obtain &lt; dB/dz &gt;=-2.3±0.6 G km-1 and &lt;
dγ/dz &gt;=-0.019±0.015 deg km-1 in the umbra. Finally,
we show how simultaneous spectro-polarimetric observations of the Sun
in visible and infrared wavelengths improve the diagnostic capabilities
of a single spectral range alone.

---------------------------------------------------------
Title: Milne-Eddington Response Functions and Their Applications
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Del Toro Iniesta,
J. C.
2006ASPC..358..197O Altcode:
We examine the errors in the atmospheric parameters recovered
from the inversion of spectro-polarimetric data with limited
wavelength sampling. We suggest that response functions evaluated in
Milne-Eddington atmospheres may be useful as diagnostic tools that
allow, for instance, the selection of the optimum wavelength positions
to be observed by vector magnetographs.

---------------------------------------------------------
Title: Evershed Clouds as Precursors of Moving Magnetic Features
around Sunspots
Authors: Cabrera Solana, D.; Bellot Rubio, L. R.; Beck, C.; del Toro
Iniesta, J. C.
2006ApJ...649L..41C Altcode: 2006astro.ph..9108C
The relation between the Evershed flow and moving magnetic features
(MMFs) is studied using high-cadence, simultaneous spectropolarimetric
measurements of a sunspot in visible (630.2 nm) and near-infrared
(1565 nm) lines. Doppler velocities, magnetograms, and total linear
polarization maps are calculated from the observed Stokes profiles. We
follow the temporal evolution of two Evershed clouds that move radially
outward along the same penumbral filament. Eventually, the clouds
cross the visible border of the spot and enter the moat region, where
they become MMFs. The flux patch farther from the sunspot has the same
polarity of the spot, while the MMF closer to it has opposite polarity
and exhibits abnormal circular polarization profiles. Our results
provide strong evidence that at least some MMFs are the continuation
of the penumbral Evershed flow into the moat. This, in turn, suggests
that MMFs are magnetically connected to sunspots.

---------------------------------------------------------
Title: The flow field in the sunspot canopy
Authors: Rezaei, R.; Schlichenmaier, R.; Beck, C.; Bellot Rubio, L. R.
2006A&A...454..975R Altcode: 2006astro.ph..4301R
Aims.We investigate the flow field in the sunspot canopy using
simultaneous Stokes vector spectropolarimetry of three sunspots
(θ=27°, 50°, 75°) and their surroundings in visible (630.15 and
630.25 nm) and near infrared (1564.8 and 1565.2 nm) neutral iron
lines. Methods: .To calibrate the Doppler shifts, we compare
an absolute velocity calibration using the telluric O_2-line at
630.20 nm and a relative velocity calibration using the Doppler
shift of Stokes V profiles in the umbra under the assumption that
the umbra is at rest. Both methods yield the same result within the
calibration uncertainties (~150 m s-1). We study the radial
dependence of Stokes V profiles in the directions of disk center and
limb side. Results: .Maps of Stokes V profile shifts, polarity,
amplitude asymmetry, field strength and magnetic field azimuth provide
strong evidence for the presence of a magnetic canopy and for the
existence of a radial outflow in the canopy. Conclusions: .Our
findings indicate that the Evershed flow does not cease abruptly at the
white-light spot boundary, but that at least a part of the penumbral
Evershed flow continues into the magnetic canopy.

---------------------------------------------------------
Title: VIP - 2D Vector Spectropolarimetry of the Solar Atmosphere
near the Diffraction Limit
Authors: Bellot Rubio, L. R.; Tritschler, A.; Kentischer, T.; Beck,
C.; Del Toro Iniesta, J. C.
2006IAUJD...3E..58B Altcode:
The KIS/IAA Vector Imaging Polarimeter (VIP) is a new instrument for
two-dimensional spectropolarimetry of the solar atmosphere. It is used
with TESOS, the triple etalon Fabry-Perot interferometer installed at
the German Vacuum Tower Telescope of Observatorio del Teide (Tenerife,
Spain). The polarimeter is based on a pair of nematic liquid crystal
retarders and a Wollaston prism. VIP and TESOS are able to observe
any spectral line in the range from 450 nm to 750 nm with a spectral
resolving power of about 250000 and spatial resolutions better than
0.5" (thanks to the Kiepenheuer Adaptive Optics System). Typically,
the four Stokes parameters of a line can be measured at 40 wavelength
points in less than 60 s, with a noise level of 1-2 x 10^-3 and a
pixel size of 0.18" x 0.18" (2x2 binning). The modulation matrix of
VIP is derived using the polarimetric calibration unit installed at
the telescope. Here we present first-light observations of VIP carried
out in November 2005. We recorded the full Stokes profiles of the 630.1
and 630.2 nm Fe I lines emerging from a solar pore and its surroundings
at a spatial resolution of ~0.4". Based on these data, we discuss the
performance and capabilities of VIP as a powerful instrument for high
spatial and temporal resolution measurements of vector magnetic fields
in the solar atmosphere.

---------------------------------------------------------
Title: Two-dimensional spectroscopy of a sunspot. III. Thermal and
kinematic structure of the penumbra at 0.5 arcsec resolution
Authors: Bellot Rubio, L. R.; Schlichenmaier, R.; Tritschler, A.
2006A&A...453.1117B Altcode: 2006astro.ph..1423B
We investigate the thermal and kinematic configuration of a sunspot
penumbra using high spectral and spatial resolution intensity profiles
of the non-magnetic Fe I 557.6 nm line. The data set was acquired
with the 2D solar spectrometer TESOS. The profiles are inverted using
a one-component model atmosphere with gradients of the physical
quantities. From this inversion we obtain the stratification with
depth of temperature, line-of-sight velocity, and microturbulence
across the penumbra. Our results suggest that the physical mechanism(s)
responsible for the penumbral filaments operate preferentially in the
lower photosphere. The spot, located at an heliocentric angle of 23°,
exhibits larger continuum intensities in the center-side penumbra
as compared with the limb side, which translates into an average
temperature difference of 100-150 K at log τ500 = 0. We
investigate the nature of the bright ring that appears in the inner
penumbra when sunspots are observed in the wing of spectral lines. It
is suggested that the bright ring does not reflect a temperature
enhancement in the mid photospheric layers. The line-of-sight velocities
retrieved from the inversion are used to determine the flow geometry
at different heights in the photosphere. Both the flow speed and
flow angle increase with optical depth and radial distance. Downflows
are detected in the mid and outer penumbra, but only in deep layers
(log τ500 ≥ -1.4). We demonstrate that the velocity
stratifications retrieved from the inversion are consistent with the
idea of penumbral flux tubes channeling the Evershed flow. Finally, we
show that larger Evershed flows are associated with brighter continuum
intensities in the inner center-side penumbra. Dark structures,
however, are also associated with significant Evershed flows. This
leads us to suggest that the bright and dark filaments seen at 0.5
arcsec resolution are not individual flow channels, but a collection
of them. Our analysis highlights the importance of very high spatial
resolution spectroscopic and spectropolarimetric measurements for a
better understanding of sunspot penumbrae.

---------------------------------------------------------
Title: Dynamical Properties of Photospheric Flux Tubes at the
Footpoints of Hot and Cool Coronal Loops
Authors: Nagata, Shin'ichi; Bellot Rubio, Luis R.; Katsukawa, Yukio
2006ApJ...638..539N Altcode:
The dynamical properties of photospheric flux tubes at the footpoints
of hot (T&gt;2 MK) and cool (T=1-2 MK) coronal loops in active region
plages are investigated by analyzing the Stokes V profile parameters of
Fe I λ6302. We show that the footpoints of both hot and cool loops are
located at the periphery of small magnetic concentrations, such as pores
and azimuth centers, having a field strength of 1-1.8 kG and a spatial
size of 2"-5". The footpoints of cool loops seem to be associated with
more densely packed and higher field strength pores and azimuth centers
than those of hot loops. Enhanced Stokes V asymmetries, redshifted
zero-crossing velocities, and small magnetic filling factors are found
at the footpoints of both types of loops, as compared with outside
the footpoints. However, the largest asymmetries and more redshifted
zero-crossing velocities are observed at the footpoints of hot loops,
where the filling factor is smaller than at the footpoints of cool
loops. The differences between the profiles emerging from the footpoints
of hot and cool coronal loops suggest that heating of the coronal loops
could be related to the dynamical properties of photospheric flux tubes.

---------------------------------------------------------
Title: A polarization model for the German Vacuum Tower Telescope
from in situ and laboratory measurements
Authors: Beck, C.; Schlichenmaier, R.; Collados, M.; Bellot Rubio,
L.; Kentischer, T.
2005A&A...443.1047B Altcode:
It is essential to properly calibrate the polarimetric properties of
telescopes, if one wants to take advantage of the capabilities of high
precision spectro-polarimeters. We have constructed a model for the
German Vacuum Tower Telescope (VTT) that describes its time-dependent
polarization properties. Since the coelostat of the telescope changes
the polarization state of the light by introducing cross talk among
different polarization states, such a model is necessary to correct the
measurements, in order to retrieve the true polarization as emitted
from the Sun. The telescope model is quantified by a time-dependent
Mueller matrix that depends on the geometry of the light beam through
the telescope, and on material properties: the refractive indices of the
coelostat mirrors, and the birefringence of the entrance window to the
vacuum tube. These material properties were determined experimentally
in-situ by feeding the telescope with known states of polarization
(including unpolarized light) and by measuring its response, and from
measurements of an aluminum-coated sample in the laboratory. Accuracy
can in our case be determined only for the combination of telescope
and spectro-polarimeter used; for the instrument POLIS at the VTT,
we estimate an accuracy of ±4-5× 10-3 for the cross talk
correction coefficients.

---------------------------------------------------------
Title: Multi-line spectroscopy of dark-cored penumbral filaments
Authors: Bellot Rubio, L. R.; Langhans, K.; Schlichenmaier, R.
2005A&A...443L...7B Altcode:
Dark-cored filaments could be the basic building blocks of sunspot
penumbrae. Yet, their nature and physical conditions are unknown. In an
attempt to improve this situation, we present the first high-resolution
spectra of dark-cored penumbral filaments. Several such filaments
were observed near the umbra/penumbra boundary of a sunspot located at
heliocentric angles of 5° and 20°. Our data reveal (a) significantly
larger Doppler shifts in the dark cores as compared to their lateral
brightenings; (b) Doppler shifts that increase with depth in the
photosphere, up to 1.5 km s-1; and (c) Doppler shifts that
increase with increasing heliocentric distance. The Doppler velocities
measured in the dark cores are almost certainly produced by upflows. In
addition, dark-cored penumbral filaments exhibit weaker fields than
their surroundings (by 100-300 G). These results provide new constraints
for models of dark-cored penumbral filaments.

---------------------------------------------------------
Title: Chromospheric and Coronal Signatures of Magnetic Flux
Cancellation in a Sunspot's Moat
Authors: Beck, C.; Bellot Rubio, L. R.; Nagata, S.
2005ESASP.596E..51B Altcode: 2005ccmf.confE..51B
No abstract at ADS

---------------------------------------------------------
Title: Sensitivity of spectral lines to temperature, velocity,
and magnetic field
Authors: Cabrera Solana, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.
2005A&A...439..687C Altcode:
We present an analytical and numerical study of the sensitivity of
weak solar photospheric lines to temperature, velocity, and magnetic
fields. Our investigation is based on the concept of response functions
(Landi degl'Innocenti &amp; Landi degl'Innocenti 1977; Ruiz Cobo &amp;
del Toro Iniesta 1994). Lines commonly used in solar spectropolarimetry,
like Fe I 630.25 nm in the visible and Fe I 1564.85 nm in the infrared,
are examined in detail as emerging from reference quiet Sun and sunspot
models. We develop a simple phenomenological model capable of describing
the response of any given line to these atmospheric parameters. We
find that: (a) the sensitivity of the lines to velocity and magnetic
fields increases with the sharpness of the intensity and circular
polarization profiles; (b) the sensitivity to temperature is determined
mainly by the variation of the source function with temperature,
which is smaller at longer wavelengths; and (c) lines quoted to be
insensitive to temperature, like Fe I 1564.85 nm and Fe I 557.61 nm,
exhibit larger changes in equivalent width than lines presumed to
have higher sensitivities to T, such as Fe I 630.25 nm. The relations
provided by our model are universal and can be used to decide which
line is better suited to measuring a given atmospheric parameter. The
results of this study are of practical interest for the design of new
instruments and for better exploitation of existing ones.

---------------------------------------------------------
Title: Magnetic Flux Cancellation in the Moat of Sunspots: Results
from Simultaneous Vector Spectropolarimetry in the Visible and
the Infrared
Authors: Bellot Rubio, Luis R.; Beck, Christian
2005ApJ...626L.125B Altcode:
We analyze multiwavelength observations of the cancellation of a
moving magnetic feature and a plage element at the outer edge of
the moat of an isolated, round sunspot. The event lasted for some 35
minutes until the smaller flux concentration disappeared completely
from the photosphere. The data set consists of high-resolution, full
vector spectropolarimetric measurements of four visible lines and
two near-infrared lines, along with speckle-reconstructed G-band and
Ca II H filtergrams. The observations reveal strong chromospheric
emission at the neutral line separating the two magnetic poles;
it becomes visible 18 minutes after the cancellation has started
and persists for 25 minutes. We have carried out an inversion of
the observed Stokes profiles to determine the variation of the
vector magnetic field, temperature, and line-of-sight velocity
during the cancellation. No significant changes in field strength,
field inclination, or temperature are observed in either of the two
opposite-polarity patches. The decrease in magnetic flux is primarily
due to a decrease in magnetic filling factor, which is accompanied by
strong upflows (of at least 1.1 km s-1) in the smaller flux
concentration. These results suggest that the cancellation is due to
magnetic reconnection in the photosphere.

---------------------------------------------------------
Title: Flow filaments linking bright and dark filaments in a sunspot
penumbra
Authors: Tritschler, A.; Schlichenmaier, R.; Bellot Rubio, L. R.
2005AGUSMSP11A..08T Altcode:
We present two-dimensional spectroscopic sunspot observations of
high spatial (≍ 0.5 arcsec) and high spectral resolution (λ/Δλ
= 250000). The observations were taken with the Telecentric Solar
Spectrometer (TESOS) operated at the German Vacuum Tower Telescope on
Tenerife. We examine a single scan taken in the popular non-magnetic
neutral iron line at 557.6 nm and concentrate our analysis on the
unsettled issue of the relation between the Evershed flow and the
intensity structure in a sunspot penumbra. At the end of the 20th
century, observers concluded that the highest flow velocities are
connected to the dark filaments which harbour more horizontal magnetic
fields than the bright filaments. Based on a correlation analysis we
find that the correlation between flows and intensity varies from the
inner to the outer penumbra, from the center-side to the limb-side
penumbra, and depends on the length of the trace used to perform
the correlation. The line-of-sight velocity maps reveal that the
Evershed flow on the center-side penumbra appears highly organised in
narrow flow filaments, while the flows in the red-shifted limb-side
penumbra do not show a filamentary fine-structure. A high correlation
between flow speed and intensity is only observed over small spatial
scales, i.e. considering short traces cutting individual features. The
correlation is positive in the inner centre and limb-side penumbra, and
tends to be negative in the outer penumbra. Our results imply that the
Evershed flow is present in bright and dark filaments. In individual
cases we find that flow filaments connect bright and dark filaments
supporting the moving tube model for the penumbral fine structure.

---------------------------------------------------------
Title: On the relation between penumbral intensity and flow filaments
Authors: Schlichenmaier, R.; Bellot Rubio, L. R.; Tritschler, A.
2005AN....326..301S Altcode:
Taking advantage of high spatial (≈ 0.5 arcsec) and high spectral
(λ/δλ = 250 000) resolution observations obtained with the 2D
spectrometer TESOS, we analyze a sunspot located at a heliocentric angle
of 23o. We elaborate on the issue of a correlation between
dark filaments and the Evershed flow in sunspot penumbrae. Controversies
on the existence of such a correlation are resolved: It varies from
the inner to the outer penumbra, from the center-side to the limb-side
penumbra, and depends on the length of the trace which is used to
perform the correlation. The flow map exhibits flow filaments in the
center-side penumbra while the red-shifted limb-side penumbra does not
show filamentary fine-structure. High correlation coefficients, |C|
≈ 0.9 are only found if small scales, i.e. short traces cutting
individual features are considered. C is positive in the inner
center and limb-side penumbra, and tends to be negative in the outer
penumbra. Our results imply that the Evershed flow is present in bright
and dark filaments. In individual cases we find that bright and dark
intensities are connected by a flow filament supporting the moving
tube model for the penumbral fine structure.

---------------------------------------------------------
Title: Two magnetic components in sunspot penumbrae
Authors: Bellot Rubio, L. R.; Balthasar, H.; Collados, M.
2004A&A...427..319B Altcode:
The magnetic and kinematic configuration of sunspot penumbrae is
investigated by performing an inversion of the Stokes profiles of three
infrared lines at 1565 nm. We use a two-component model atmosphere
to describe, at least to first order, the unresolved structure of
the penumbra. The observed Stokes profiles are successfully fitted,
including those exhibiting abnormal shapes. The results of the inversion
are consistent with the idea that the penumbra is formed by almost
horizontal flux tubes embedded in a more vertical background magnetic
field, as proposed by Solanki &amp; Montavon (\cite{Sol93}). The tubes
possess weaker fields than the background except in the very outer
penumbra, and carry most of the Evershed flow. We characterize the
radial variation of the magnetic field vector and the velocity vector
in these atmospheric components. In the middle penumbra and beyond,
the magnetic field and the flow in the tubes are seen to return to
the solar surface. Everywhere in the penumbra, there is a perfect
alignment of the magnetic field vector and the velocity vector in
the component describing the penumbral flux tubes. We find that the
Evershed flow is supercritical in many places of the outer penumbra,
and supersonic at some locations near the outer sunspot boundary. Based
on these inversions, we suggest that the azimuthal fluctuations in the
average magnetic field inclination and strength inferred from simple
one-component models are caused by fluctuations in the filling factor
(i.e., the fractional area of the resolution element occupied by
flux tubes), not by changes in the intrinsic magnetic and kinematic
properties of the background or the flux-tube atmospheres. Also,
we confirm the jump of magnetic field azimuth proposed by Müller et
al. (\cite{Mul02}) to explain the observed net circular polarization
of infrared lines.

---------------------------------------------------------
Title: Asymmetrical appearance of dark-cored filaments in sunspot
penumbrae
Authors: Sütterlin, P.; Bellot Rubio, L. R.; Schlichenmaier, R.
2004A&A...424.1049S Altcode:
Recent sunspot observations at unprecedented resolution have led to the
discovery of dark cores in the bright filaments that form the penumbra
(\citealt{scharmer02_Nat420}). The discovery paper considered spots
at disk center only, so the properties of the dark-cored filaments
remain largely unknown. Here we analyze a speckle-reconstructed time
series of G-band and blue continuum images of a sunspot acquired with
the Dutch Open Telescope. The target was located at an heliocentric
angle of 27 deg. We confirm the existence of dark-cored penumbral
filaments also in spots outside the disk center, and report on distinct
differences between the center and limb-side penumbra. In the inner
center-side penumbra, filaments are detected as two narrow bright
streaks separated by a central obscuration. These structures move
together as a single entity. On the limb side, dark cores are hardly
seen. The time series is used to determine the sizes (∼200-250 km),
proper motions (∼280 m s-1), and lifetimes (⪉45 min)
of typical dark-cored filaments.

---------------------------------------------------------
Title: On the fine structure of sunspot penumbrae. I. A quantitative
comparison of two semiempirical models with implications for the
Evershed effect
Authors: Borrero, J. M.; Solanki, S. K.; Bellot Rubio, L. R.; Lagg,
A.; Mathew, S. K.
2004A&A...422.1093B Altcode:
Sunspot penumbrae exhibit prominent fine structure. Different
interpretations of spectropolarimetric observations suggest different,
sometimes contradictory, properties of this fine structure. In this
paper we show that the results of inversions of penumbral infrared
profiles based on one-component models with gradients of the atmospheric
parameters and two-component models without gradients are compatible
with each other. Our analysis reconciles the results of previous
investigations and provides further support for the picture that sunspot
penumbrae are composed of penumbral flux tubes embedded in a magnetic
background. The magnetic field in the tubes is more horizontal and
weaker than that of the background atmosphere. While the tubes carry
most of the Evershed flow, the background is essentially at rest. We
notice also that the magnetic field strength in the flux tubes drops
much more slowly with radial distance than the background field. This
finding is discussed as a possible driver for the Evershed flow.

---------------------------------------------------------
Title: Towards 2D-Spectropolarimetry with TESOS and Adaptive Optics
Authors: Tritschler, A.; Bellot Rubio, L. R.; Kentischer, T. J.
2004AAS...204.6902T Altcode: 2004BAAS...36Q.794T
The TElecentric SOlar Spectrometer (TESOS) is a 2D tunable filtergraph
installed at the Vacuum Tower Telescope of Teide Observatory (Tenerife,
Spain). The instrument features a high spectral resolution (λ /Δ
λ ∼ 250000 at 633 nm) and is capable of scanning solar lines
over a broad wavelength range (430 - 700 nm). Together with the
Kiepenheuer-Institute Adaptive Optics System (KAOS), it is able to
achieve spatial resolutions of the order of 0.5 arcsec on a regular
basis. Here we present the first spectropolarimetric observations of
a sunspot and its immediate surroundings using TESOS. We describe the
optical setup, characterize the performance of TESOS operated in the
polarimetric mode, and investigate the appearance of the sunspot as
seen in circular polarized light with an angular resolution better
than 0.5 arcsec. Our results demonstrate the feasibility of using
TESOS as a polarimeter, and may be of interest for the design of
a TESOS-like multiple-etalon magnetograph for the 4-m NSO/Advanced
Technology Solar Telescope.

---------------------------------------------------------
Title: Two-dimensional spectroscopy of a sunspot. II. Penumbral
line asymmetries
Authors: Schlichenmaier, R.; Bellot Rubio, L. R.; Tritschler, A.
2004A&A...415..731S Altcode:
We present, analyse, and interpret line asymmetries from Fe I 557.6
nm of a sunspot penumbra at a heliocentric angle of 23o
with high spatial (0.5 arcsec) and spectral (λ/\triangleλ=250 000)
resolution. The data set is described and presented in the first paper
of this series \citep{tritschler+etal2003}. Line bisectors are used
to quantify the line asymmetries. Our findings are: (1) For averaged
limb and center side bisectors the shift increases linearly with the
bisector intensity level, but the limb side bisector is more inclined
than the center side bisector. (2) Individual bisectors exhibit kinks,
such that the bisector at high intensity levels is shifted towards the
red for both, limb and center side bisectors. Some of the kinks produce
bisector reversals in the outer center side penumbra. The bisector
properties and their intriguing differences between center and limb side
can be explained if one assumes downflows in deep atmospheric layers
(\log τ &gt; -1). This is demonstrated by synthetic bisectors. The
differences between the two penumbral sides are due to projection
effects of non-horizontal flow channels. Our findings also imply that
bisectors reversals are not due to elevated channels, but due to the
presence of downflows. Along a specific center side flow filament the
bisector shift is found to be largest in the line wing, except for the
outer end of the filament, where a kink at high bisector intensities
toward the red is found. This is consistent with an upflow at the
inner footpoint, a deep lying horizontal flow, and, after a spatial
distance of 4 arcsec, with a downflow at the end of the flow filament.

---------------------------------------------------------
Title: Two-dimensional spectroscopy of a sunspot. I. Properties of
the penumbral fine structure
Authors: Tritschler, A.; Schlichenmaier, R.; Bellot Rubio, L. R.;
KAOS Team; Berkefeld, T.; Schelenz, T.
2004A&A...415..717T Altcode:
We investigate the properties of the fine structure of a sunspot
penumbra based on spectroscopic measurements with high spectral
(λ/δλ=250 000) and high spatial (≈0.5 arcsec) resolution. The
magnetically insensitive Fe I 557.6 nm line is used to probe the
penumbral atmosphere. The data was taken at the German Vacuum Tower
Telescope with the 2D-spectrometer TESOS, taking advantage of the
recently installed Kiepenheuer Adaptive Optics System (KAOS). The field
of view covers a sunspot located at 23o off the disk center
and its immediate surroundings. The penumbral structure is studied
by means of maps computed for the line-of-sight velocity, the line
width, the equivalent width and the line depression. Line-of-sight
velocities are derived from the Doppler shifts at different bisector
levels. From these maps we infer the flow field geometry and study the
azimuthal and radial dependences of the line parameters. Our findings
can be summarized as follows: (a) the flow pattern has a conspicuous
filamentary structure in the deep photospheric layers and is rather
diffuse in the high layers. (b) The flow field slightly spreads and
fans out with height. (c) The flow geometry confirms the presence of
an upflow component in the inner penumbra and a downflow component in
the middle and outer penumbra. (d) We find an enhanced brightness of
the mid-penumbra (“bright ring”) in the line wings, but not in the
continuum or line core. (e) The azimuthal average of the equivalent
width, the line width and the absolute flow velocity increase with
radial distance within the penumbra. (f) Small-scale variations of
the equivalent width and the line width on the center-side penumbra
are co-spatial and correlated with (blue-shifted) fluctuations in
the line-of-sight velocity. (g) Inner limb-side penumbral grains are
associated with blue-shifts of v≤-400 m s-1, indicating
upflows. (h) One umbral dot in our sample is associated with a
blue-shift of v=-200 m s-1.

---------------------------------------------------------
Title: Ludwig Biermann Award Lecture: Sunspots as seen in Polarized
Light (With 14 Figures)
Authors: Bellot Rubio, Luis R.
2004RvMA...17...21B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Velocity field in the intergranular atmosphere
Authors: Kučera, A.; Koza, J.; Bellot Rubio, L. R.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
2004HvaOB..28...19K Altcode:
The line-of-sight velocity ľand macroturbulent velocity are studied
in the centre of the intergranular space in the solar photosphere. An
inversion method is applied to a 4-min time sequence of Stokes
I spectra of the 5, 6 and 7 lines observed with high spatial and
temporal resolutions at solar disk centre. The results are presented
in the form of the functional dependence of ľ(logτ5,t)
and (t) on the continuum optical depth τ5 at 500 nm and
time t. A ľof several hundreds of meters per second was found in the
upper photosphere (logτ5≤-1.5), where the plasma flows
away from the observer. On the contrary, upflows directed toward the
observer were found in deeper layers (logτ5&gt;-1.5). The
typical value of in the centre of the intergranular space is found to be
∼1.7 kms, which is about 0.5 kms greater than in the adjacent granule.

---------------------------------------------------------
Title: Thermal Kinematic Structure of a Sunspot at 0.5 arcsec
Resolution
Authors: Bellot Rubio, L. R.; Schlichenmaier, R.; Tritschler, A.
2003ANS...324..104B Altcode: 2003ANS...324..P10B
No abstract at ADS

---------------------------------------------------------
Title: Penumbral Line Asymmetries of Fe I 557.6 nm: Implications on
the Flow Geometry of a Sunspot Penumbra
Authors: Schlichenmaier, P.; Bellot Rubio, L.; Tritschler, A.
2003ANS...324..105S Altcode: 2003ANS...324..P11S
No abstract at ADS

---------------------------------------------------------
Title: Understanding internetwork magnetic fields as determined
from visible and infrared spectral lines
Authors: Bellot Rubio, L. R.; Collados, M.
2003A&A...406..357B Altcode:
We present numerical experiments aimed at understanding why
near-infrared observations systematically deliver weak magnetic fields
in the internetwork, whereas analyses based on visible lines indicate
that kG fields are ubiquitous. Synthetic noisy Stokes V profiles of the
iron lines at 6302 Å and 1.565 mu m have been produced under varying
conditions in an effort to simulate polarized spectra coming from the
internetwork. An inversion technique has been applied to the profiles,
as it is usually done with real observations, in order to derive the
distribution of magnetic fields in the simulated region. Our results
show that infrared lines yield distributions which are very similar to
those used as input for the simulation, while visible lines are to a
large extent affected by noise. Analyses based on the Fe I lines at 6302
Å may lead to an overabundance of kG fields if the signal-to-noise
ratio in Stokes V is poorer than about 10. A particular example is
shown where strong fields are retrieved in nearly 30% of the pixels
of a simulated internetwork region in which only fields of 200 G exist.

---------------------------------------------------------
Title: Accurate atomic parameters for near-infrared spectral lines
Authors: Borrero, J. M.; Bellot Rubio, L. R.; Barklem, P. S.; del
Toro Iniesta, J. C.
2003A&A...404..749B Altcode:
A realistic two-component model of the quiet solar photosphere is
used to fit the intensity spectrum of the Sun in the wavelength
range 0.98-1.57 mu m. Our approach differs from earlier attempts in
many respects: proper account of convective inhomogeneities is made,
accurate collisional broadening parameters from quantum mechanical
computations are used, and the effects of possible blends in the local
continuum are corrected empirically. This allows us to derive oscillator
strengths and central wavelengths for virtually any unblended line of
the solar spectrum. The accuracy of the inferred atomic parameters,
about 0.06 dex for oscillator strengths and 5 mÅ at 1 mu m for central
wavelengths, is similar to that of the best laboratory measurements. We
apply our method to 83 near-infrared lines belonging to 6 different
atomic species. The availability of accurate oscillator strengths and
central wavelengths for lines of different species is essential for
the interpretation of high resolution spectroscopic observations. The
method is especially useful in the infrared, a wavelength domain where
laboratory measurements are scarce.

---------------------------------------------------------
Title: Magnetoacoustic Waves in Sunspots
Authors: Khomenko, E. V.; Collados, M.; Bellot Rubio, L. R.
2003ApJ...588..606K Altcode:
Observed variations of the magnetic field strength in sunspot umbrae
consist of intrinsic oscillations and “false” oscillations due to
time-dependent opacity effects. Here we present an approach intended for
the separation of these components. We develop a mathematical formalism
based on the analytical solution of the MHD equations including gravity,
inclination of the magnetic field, and effects of nonadiabaticity. The
theoretical results are compared with observations in the near-infrared
at 1.56 μm by Bellot Rubio and coworkers using the Tenerife Infrared
Polarimeter. It is shown that part of the detected field strength
variations can be intrinsic magnetic field oscillations caused by
magnetoacoustic waves.

---------------------------------------------------------
Title: Field-aligned Evershed flows in the photosphere of a sunspot
penumbra
Authors: Bellot Rubio, L. R.; Balthasar, H.; Collados, M.;
Schlichenmaier, R.
2003A&A...403L..47B Altcode:
We determine the inclinations of the vector magnetic field and flow
velocity in a sunspot penumbra by interpreting full Stokes profiles of
three infrared lines observed with the Tenerife Infrared Polarimeter. It
is shown that analyses based on one-component atmospheres deliver flow
velocities which are more horizontal than the average magnetic field
by up to 10 deg. This apparent violation of the concept of frozen-in
magnetic fields is solved as soon as two magnetic atmospheres are
allowed to coexist in the resolution element. The magnetic field and
velocity in the atmospheric component carrying the Evershed flow are
found to be aligned to within +/- 2 deg all the way from the inner
to the outer penumbra. This is the first observational confirmation
of magnetic fields being frozen into the plasma in sunspots. Our
results indicate that sunspot penumbrae can be understood in terms of
inclined flux tubes embedded in a more vertical background field. The
flux tubes carry most of the Evershed flows and return to the solar
surface in the middle penumbra and beyond. The background atmosphere
is essentially at rest in the inner penumbra, and harbors small flows
in the outer penumbra.

---------------------------------------------------------
Title: The structure of the penumbra
Authors: Balthasar, H.; Bellot Rubio, L.; Collados, M.
2003AN....324..390B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Fluctuations in the Activity Curve of the 2002 Leonids
Authors: Ruiz Herrera, Lola; Bellot Rubio, Luis R.; Serra-Ricart,
Miquel
2003IAUJD..19E..55R Altcode:
We present observations of the 2002 Leonid meteor shower taken with
four intensified video cameras from Teide Observatory (Tenerife Spain)
on November 19 2002. The cameras fitted with f/1.4 85 mm objectives
were aimed at 6 deg above the horizon in order to monitor the largest
atmospheric volume possible. The most sensitive camera detected 1300
meteors between 0312 and 0456 UT i.e. the period covering the European
Leonid storm of 2002. The activity curve constructed from these data
peaks at 0401 UT about 9 minutes earlier than indicated by the visual
observations analyzed by the International Meteor Organization. Our
results thus favor the model of Lyytinen and van Flandern who predicted
the first maximum at 0402 UT. We find statistically significant
oscillations in the activity curve. A Fourier analysis delivers a
period of about 7 minutes. These observations confirm the discovery
of Singer et al. (2000) that density fluctuations exist in the Leonid
dust trails at spatial scales of 10000-30000 km. The oscillations we
observe are very similar to those detected by Singer et al. the only
difference being that the dust trail is 132 years older.

---------------------------------------------------------
Title: The Fine Structure of the Penumbra: from Observations to
Realistic Physical Models
Authors: Bellot Rubio, L. R.
2003ASPC..307..301B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evolution of temperature in granule and intergranular space
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
2003AN....324..349K Altcode:
The temporal evolution of temperature in a dissolving granule and
in an adjacent intergranular space is presented. The semi-empirical
evolutionary models have been calculated using an inversion method
applied to 4-min time series of Stokes I spectral line profiles. The
models are presented in the form of the functional dependence of
temperature T(log tau_5 ,t) on optical depth tau_5 at 500 nm and time
t. The observed disappearance of the granule is accompanied with overall
cooling of the granular photosphere. Temperature changes greater than
100 K have been found in deeper (log tau_5 &gt;=0) and upper layers
(log tau_5 &lt;=-2) whereas the intermediate layers are thermally
stable. The intergranular space, which is 2 arcsec off the granule,
keeps the temperature structure of the layers from log tau_5 =0.5 to
log tau_5 =-2 without global evolutionary changes except short-term
and spatially confined heating. Finally, the significant temperature
changes in the upper layers (log tau_5 &lt;=-2.5) observed during the
time interval of 4 min are found to be typical for the granular and
intergranular photosphere.

---------------------------------------------------------
Title: 2D Solar Spectroscopy with a Triple Fabry-Perot Filtergraph
Authors: Bellot Rubio, Luis R.; Tritschler, Alexandra; Schlichenmaier,
Rolf
2003IAUJD..20E..27B Altcode:
TESOS is a tunable narrow-band filter based on three Fabry-Perot etalons
operated in a telecentric configuration. Installed at the German Vacuum
Tower Telescope (VTT) of Teide Observatory (Spain) it is used regularly
for 2D spectroscopy of the solar atmosphere. Its spectral resolution
of 250000 is similar to that of grating spectrographs. In the high
resolution mode the field of view of TESOS is 42 arcsec in diameter and
the image scale is 0.09 arcsec/pixel. Due to the high quantum efficiency
of the detector above 500 nm exposure times of a few tens of msec can
be used. As a result TESOS is able to measure the intensity profiles
of a given spectral line across the field of view in less than 40 sec
(assuming 100 wavelength positions). Recently TESOS has been combined
with KAOS the adaptive optics system of the VTT to improve the spatial
resolution of the observations up to 0.4 arcsec. Here we present the
first science results of TESOS+KAOS based on observations of a sunspot
penumbra. Maps of various spectroscopic parameters are computed and
the line asymmetries induced by the Evershed flows are investigated
by means of a bisector analysis of the FeI line at 557.6 nm.

---------------------------------------------------------
Title: Two-Component Modeling of Convective Motions in the Solar
Photosphere and Determination of Atomic Parameters
Authors: Borrero, J. M.; Bellot Rubio, L. R.
2003IAUS..210P..C9B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Accurate Atomic Parameters from the Solar Spectrum
Authors: Bellot Rubio, Luis Ramon; Borrero, Juan Manuel; Barklem,
Paul; del Toro Iniesta, Jose Carlos
2003IAUJD..20E..16B Altcode:
A realistic two-component model of the quiet solar photosphere is used
to fit the full shape of the intensity profiles of unblended lines in
the solar spectrum. Our approach differs from previous attempts in many
respects: proper account of granulation inhomogeneities is made accurate
collisional broadening parameters from quantum mechanical computations
are used and possible absorptions in the local continuum due to blends
are corrected empirically. This allows us to derive oscillator strengths
and central wavelengths for any clean line with an accuracy comparable
with that of the best laboratory measurements. The availability of
very precise atomic parameters for lines of different species is
essential for the interpretation of high resolution spectroscopic
observations. Abundance determinations and investigations of granular
motions in stellar atmospheres are among the applications that would
benefit from such accurate atomic data. As an example we determine the
oscillator strengths and central wavelengths of 100 unblended lines
in the near-infrared (0.99-1.56 microns) a wavelength domain where
laboratory measurements are particularly scarce.

---------------------------------------------------------
Title: Modeling the Fine Structure of a Sunspot Penumbra through
the Inversion of Stokes Profiles
Authors: Borrero, J. M.; Lagg, A.; Solanki, S. K.; Frutiger, C.;
Collados, M.; Bellot Rubio, L. R.
2003ASPC..286..235B Altcode: 2003ctmf.conf..235B
No abstract at ADS

---------------------------------------------------------
Title: Line-of-sight velocity in a semiempirical model of a
disappearing granule
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
2002ESASP.506..443K Altcode: 2002svco.conf..443K; 2002ESPM...10..443K
The behaviour of the line-of-sight velocity in the centre of a
disappearing granule is analyzed using an inversion method applied
to a time-series of spectra containing the Fe I 522.5 nm, 557.6
nm and 557.7 nm lines. The temporal evolution of the line-of-sight
velocity vLOS is presented in the form of the functional
dependence of vLOS(logτ5, t) on the optical
depth τ5 at 500 nm and time t. An oscillatory behaviour
is found in the velocity stratification with nearly constant phase
through the photosphere. The amplitude of variations increases from
logτ5 = -0.3 to logτ5 = -2.5 reaching a maximum
of ~1.2 km s-1. A zero velocity layer is detected in every
instantaneous model of the velocity stratification. The results suggest,
that the zero velocity may occur in a considerable range of the optical
depths from logτ5 ~ -2 to logτ5 ~ -3.5.

---------------------------------------------------------
Title: Observations of the 2001 Leonid meteor storm from northern
Australia with the Teide imaging meteor system
Authors: Bellot Rubio, L. R.; Martínez-Delgado, D.; López-Sánchez,
A. R.; Ruiz Herrera, L.; Serra-Ricart, M.; Rodríguez Gil, P.;
Oscoz, A.
2002ESASP.500..221B Altcode: 2002acm..conf..221B
We describe the Teide Imaging MEteor System (TIMES), a fully automatic
experiment consisting of two fixed image-intensified video cameras
which are operated from Teide Observatory (Tenerife, Spain). A second
station equipped with an identical system is located in Maspalomas
(Gran Canaria, Spain). TIMES has been designed to work with the MetRec
detection software for efficient video observations of meteors with
a minimum of human interaction. The system will be used to monitor
the shower and sporadic meteor activity for at least three years. In
addition, double-station observations will be made on every clear night
for orbital calculations and light curve analyses. We also present
preliminary results on the 2001 Leonid storm observed by TIMES during
the scientific mission organized by the Instituto de Astrofisica de
Canarias (Spain). Double-station observations were carried out in
Central Australia from 16 to 18 November 2001. In this contribution we
concentrate on the night of maximum activity and construct the activity
curve and magnitude distribution of the Leonid meteors detected by
our video system in the interval from 18 to 19 UT, 18 November 2001.

---------------------------------------------------------
Title: Spectropolarimetry and magnetography from the ground
Authors: Bellot Rubio, Luis R.
2002ESASP.505....3B Altcode: 2002solm.conf....3B; 2002IAUCo.188....3B
Most of what we know today about solar magnetic fields has been
learned through the measurement and interpretation of the polarization
of spectral lines. In this contribution, I review the different
instruments used for solar polarimetry, the techniques we apply
to extract information from the measurements, and the advantages
and disadvantages of polarization studies from the ground. I will
describe some recent results obtained from high precision, full
Stokes spectropolarimetry in order to illustrate the potential of
ground-based observations. In particular, I will discuss advances in the
understanding of the structure of sunspot penumbrae, a topic of active
research these days. Finally, expected developments and applications
of solar polarimetry from the ground will be briefly mentioned.

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Title: Observation and Interpretation of Leonid Impact Flashes on
the Moon in 2001
Authors: Ortiz, J. L.; Quesada, J. A.; Aceituno, J.; Aceituno, F. J.;
Bellot Rubio, L. R.
2002ApJ...576..567O Altcode:
We present observations of lunar Leonid impact flashes recorded in 2001
November from Spain. Four impact flashes were detected on November
18. Another flash was also recorded on the same night, which appears
to be impact related, and two more on that night are possibly, but
not unambiguously, of impact nature. On November 19 another flash was
detected, which very likely resulted from an impact. The brightest
impact flash reached a peak brightness of 5.2+/-0.3 mag in V; it had
a very dim precursor just 0.02 s prior to peak brightness and had
a very long lasting afterglow that remained visible for more than
600 ms with oscillations in brightness; this unique and unexpected
behavior challenges current models of impact flashes. The other flashes
did not show such a behavior and remained visible for a few tens of
milliseconds. Adopting the luminous efficiency derived for the 1999
lunar Leonids (2×10-3), our observations can be used
to estimate meteoroid fluxes. The observations are compatible with
a flux of 0.1 meteoroids of mass larger than 2×10-8 kg
km-2 hr-1 on November 18 at 18:15 UT, provided
that a mass index of 1.69 is used. Both the flux and the mass index
agree with meteor observations carried out in 2001 from several
locations on Earth.

---------------------------------------------------------
Title: Iron abundance in the solar photosphere. Application of a
two-component model atmosphere
Authors: Bellot Rubio, L. R.; Borrero, J. M.
2002A&A...391..331B Altcode:
A realistic two-component model of the quiet Sun is used to determine
the solar abundance of iron from the inversion of a number of Fe I and
Fe II spectral lines for which accurate atomic parameters (oscillator
strengths, central wavelengths, and collisional broadening cross
sections) exist. From 33 Fe I lines we infer an abundance of A_Fe =
7.43 +/- 0.06, whereas we estimate A_Fe = 7.45 +/- 0.08 from 10 Fe
II lines. These values are in excellent agreement with the results of
analyses based on realistic 3D hydrodynamical simulations of the solar
granulation, and imply a low photospheric iron abundance. We investigate
the effects of convective motions and granular temperatures and conclude
that both are important for reliable abundance determinations. For Fe
I lines, the effects of convective motions can be simulated by using
a microturbulent velocity of about 1 km s-1, whereas it
is possible to account for temperature inhomogeneities by adopting an
average temperature stratification which is cooler than the Holweger
&amp; Müller model in the upper layers.

---------------------------------------------------------
Title: Modeling the photometric and dynamical behavior of
Super-Schmidt meteors in the Earth's atmosphere
Authors: Bellot Rubio, L. R.; Martínez González, M. J.; Ruiz
Herrera, L.; Licandro, J.; Martínez-Delgado, D.; Rodríguez-Gil,
P.; Serra-Ricart, M.
2002A&A...389..680B Altcode:
Faint meteors observed with Super-Schmidt cameras are re-examined
in order to assess whether their dynamical and photometric behavior
can be described by means of the single body theory. Velocities,
decelerations and magnitudes are fitted simultaneously to synthetic
curves resulting from integration of the appropriate set of differential
equations. The parameters determined by this procedure are the ablation
coefficient, the shape-density coefficient and the preatmospheric
mass of each individual meteoroid. It turns out that 73% of the
meteors analyzed here (with magnitudes in the range from +2.5 to -5)
are reasonably well described by this theory, suggesting that they
did not undergo significant fragmentation during their atmospheric
flight. Nevertheless, we identify some systematic differences between
observed and theoretical light curves of meteors for which the fit
is good. Meteoroid bulk densities are estimated from the retrieved
shape-density coefficients. The distributions of individual values
are broad, indicating that objects of different densities coexist
within the same meteoroid population. The average density is found to
be 2400, 1400, and 400 kg m-3 for A-type, B-type and C-type
meteoroids, respectively. These results do not confirm the large values
determined from quasicontinuous fragmentation models.

---------------------------------------------------------
Title: A two-component model of the solar photosphere from the
inversion of spectral lines
Authors: Borrero, J. M.; Bellot Rubio, L. R.
2002A&A...385.1056B Altcode:
A two-component model of the solar photosphere is obtained from the
inversion of the intensity profiles of 22 Fe I spectral lines for which
very accurate atomic data (oscillator strengths, central wavelengths,
and collisional broadening parameters) exist. The model is meant to
describe the effects of convective motions in the solar photosphere. It
has been subject to various tests to confront its predictions with
observations of the solar spectrum. The model is able to reproduce the
observed line shifts and equivalent widths of about 800 spectral lines
of iron and other species. It is also capable of matching the observed
center-to-limb variation of the continuum intensity with unprecedented
accuracy. This allows us to determine line-transition parameters from
the fitting of the solar spectrum. Exploratory calculations demonstrate
that the model can be used to derive transition probabilities and
central wavelengths of Fe I and Fe II lines, as well as other elements,
within the uncertainties of the best laboratory measurements.

---------------------------------------------------------
Title: Modeling the dynamical and photometric behavior of faint
meteors in the Earth's atmosphere
Authors: Bellot Rubio, Luis R.; Martínez González, María Jesús;
Ruiz Herrera, Lola; Licandro, Javier; Martínez Delgado, David;
Rodríguez Gil, Pablo; Serra-Ricart, Miquel
2001ESASP.495..525B Altcode: 2001mete.conf..525B
Faint meteors observed with Super-Schmidt cameras are re-examined
in order to assess whether their dynamical and photometric behavior
can be described by means of the single body theory. Velocities,
decelerations and magnitudes are fitted simultaneously to synthetic
curves resulting from integration of the appropriate set of differential
equations. The parameters determined by this procedure are the ablation
coefficient, the shape-density coefficient and the preatmospheric mass
of the meteoroids. It turns out that 64% of the meteors analyzed here
are reasonably well described by this theory, suggesting that they
did not undergo significant fragmentation during their atmospheric
flight. We identify some systematic differences between observed and
theoretical light curves of meteors for which the fit is good. From
the retrieved shape-density coefficients we derive meteoroid bulk
densities. The average density turns out to be 1.0 g cm-3,
with individual values ranging from 0.2 g cm-3 to 1.4 g
cm-3. This work represent a first step toward the analysis
of low-light level video observations of very small meteoroids.

---------------------------------------------------------
Title: Observation of Convective Collapse and Upward-moving Shocks
in the Quiet Sun
Authors: Bellot Rubio, Luis R.; Rodríguez Hidalgo, Inés; Collados,
Manuel; Khomenko, Elena; Ruiz Cobo, Basilio
2001ApJ...560.1010B Altcode:
We present spectropolarimetric evidence of convective collapse
and destruction of magnetic flux by upward-moving fronts in the
quiet Sun. The observational material consists of time series of
the full Stokes vector of two infrared spectral lines emerging from
regions associated with Ca II K network points. The amplitude of the
circular polarization profiles of a particular spatial point is seen to
increase while the profiles are redshifted. It then decreases during
a much shorter phase characterized by large blueshifts. Inspection
of the data indicates that the blueshift occurs because of the sudden
appearance of a new, strongly displaced Stokes V profile of the same
polarity. The amplification of the magnetic signal takes place in a
time interval of about 13 minutes, while blueshifts and the concomitant
decreasing Stokes V amplitudes last for only 2 minutes. An inversion
code based on the thin flux-tube scenario has been applied to the data
in order to derive the thermal, magnetic, and dynamic structures of
the atmosphere. According to our results, the field strength undergoes
a moderate increase from 400 to 600 G at z=0 km during the phase in
which redshifts are present. The observed redshifts are produced by
internal downflows of up to 6 km s-1 at z=0 km. After ~13
minutes, the material falling down inside the tube appears to bounce
off in the deeper layers, originating an upward-propagating front whose
manifestation on the Stokes V profiles is a large blueshift. The front
moves with a speed of 2.3 km s-1 and has a downflow-to-upflow
velocity difference of about 7 km s-1 initially and some
4 km s-1 after 2 minutes. It strongly weakens the magnetic
field strength and may be responsible for the complete destruction of
the magnetic feature. The observed behavior is in general agreement
with theoretical predictions of flux expulsion, convective collapse,
and development of shocks within magnetic flux tubes.

---------------------------------------------------------
Title: Cold, Supersonic Evershed Downflows in a Sunspot
Authors: del Toro Iniesta, Jose Carlos; Bellot Rubio, Luis R.;
Collados, Manuel
2001ApJ...549L.139D Altcode:
We report here on the discovery of supersonic Evershed downflows
in the penumbra of a sunspot. These flows are shown to occur along
spatially unresolved, very cold magnetic flux tubes whose downflowing
footpoints are found from the middle penumbra outward. Evershed
flows along magnetic field lines returning to the solar surface were
discovered by Westendorp Plaza and coworkers, but only in the outer
parts of the penumbra and beyond its visible boundary; on the other
hand, no supersonic flows of any type have ever been reported in the
photosphere of sunspots, except for the very different case of the
delta spot analyzed by Martínez Pillet and coworkers. We present
unequivocal evidence of such supersonic motions, already predicted
theoretically by the siphon-flow model, from the interpretation
of infrared spectropolarimetric observations of a sunspot with
unprecedented spatial resolution.

---------------------------------------------------------
Title: Spectropolarimetric Signatures of Convective Collapse
Authors: Rodrígues Hidalgo, I.; Bellot Rubio, L. R.; Collados, M.;
Ruiz Cobo, B.
2001ASPC..236..415R Altcode: 2001aspt.conf..415R
No abstract at ADS

---------------------------------------------------------
Title: The IAC Stokes Profile Inversion Codes based on Response
Functions (CD-ROM Directory: contribs/bellot)
Authors: Bellot Rubio, L. R.
2001ASPC..223..569B Altcode: 2001csss...11..569B
No abstract at ADS

---------------------------------------------------------
Title: Lagrangian and Eulerian Stratifications of Acoustic
Oscillations through the Solar Photosphere
Authors: Rodríguez Hidalgo, Inés; Ruiz Cobo, Basilio; Collados,
Manuel; Bellot Rubio, Luis R.
2001ApJ...547..491R Altcode:
We evaluate the stratification of acoustic oscillations in the solar
photosphere in both the Lagrangian (comoving) frame of reference and
the Eulerian (inertial) frame of reference, from a temporal sequence
of model atmospheres in an optical depth scale obtained after a
quasi-non-LTE inversion of the radiative transfer equation applied to
spectral observations of the K I 7699 Å line. Our results suggest
that, to first order, the photosphere moves up and down as a whole
with amplitudes ranging from ~8 km in deep layers (around 0 km) to ~19
km in the upper layers (around 640 km). In Lagrangian coordinates, we
observe numerous short-lived, local temperature and velocity amplitude
enhancements in medium-high layers, together with asymmetric waveforms
in the oscillation of these two physical quantities. The Lagrangian
temperature oscillation clearly shows two nodes associated with sharp
phase jumps of about 180°, whereas the velocity amplitude shows
the well-known increase with geometrical height, at nearly constant
phase. In Eulerian coordinates, the perturbations are dominated by
the coherent oscillation of the entire photosphere.

---------------------------------------------------------
Title: Photospheric acoustic oscillations in a Langrangian reference
system
Authors: Rodríguez Hidalgo, I.; Ruiz Cobo, B.; Collados Vera, M.;
Bellot Rubio, L. R.
2001ESASP.464..239R Altcode: 2001soho...10..239R
The stratification of acoustic oscillations through the solar
photosphere in Lagrangian (comoving) coordinates has been evaluated from
a quasi-NLTE inversion of the radiative transfer equation (RTE) applied
to a temporal sequence of K I 7699 Å line spectra. The stratifications
of amplitude and phase of the temperature and line-of-sight (LOS)
velocity Lagrangian oscillations have been evaluated. Our results
suggest that, to first order, the photosphere moves up and down as a
whole with amplitudes ranging from ~8 km in deep layers (around 0 km)
to ~19 km in the upper layers (around 640 km). Numerous short-lived,
local temperature and velocity amplitude enhancements in medium-high
layers are observed, together with an asymmetric waveform in the
oscillation of these two physical quantities. Two nodes are clearly seen
in the Lagrangian temperature oscillation run, which are associated with
sharp phase jumps of about 180°. The velocity amplitude shows the well
known increase with geometrical height, keeping practically in phase.

---------------------------------------------------------
Title: Luminous Efficiency in Hypervelocity Impacts from the 1999
Lunar Leonids
Authors: Bellot Rubio, L. R.; Ortiz, J. L.; Sada, P. V.
2000ApJ...542L..65B Altcode:
An analysis of the optical flashes produced by Leonid meteoroids
impacting the Moon in 1999 November is carried out in order to estimate
the fraction of kinetic energy converted into radiation, the so-called
luminous efficiency η. It is shown that the observational data are
consistent with luminous efficiencies of 2×10-3 in the
wavelength range of 400-900 nm with an uncertainty of about 1 order
of magnitude. This experimental value of η is significantly larger
than previous estimates for meteoroids of asteroidal composition
based on numerical calculations and scaling laws from laboratory
collisions. According to our results, the luminous efficiency might
vary with mass, i.e., the smaller impactors converting less kinetic
energy into light and vice versa. A comparison with recent numerical
simulations for meteoroids of cometary composition is also carried out.

---------------------------------------------------------
Title: Optical detection of meteoroidal impacts on the Moon
Authors: Ortiz, J. L.; Sada, P. V.; Bellot Rubio, L. R.; Aceituno,
F. J.; Aceituno, J.; Gutiérrez, P. J.; Thiele, U.
2000Natur.405..921O Altcode:
Impacts of meteoroids on the Moon should cause detectable optical
flashes, but the population of objects that are big enough is very low,
and hitherto no unambiguous impact flashes have been recorded. The
flux of meteoroids associated with the Leonid meteor shower of 18
November 1999 was predicted to produce observable flashes on the
night side of the Moon. Here we report the unambiguous detection of
five such impact flashes, three of which were seen simultaneously by
other observers. We also observed a possible impact flash on 16 July
1999. All of the flashes were of very brief duration (&lt;0.02s),
as expected for high-speed impacts.

---------------------------------------------------------
Title: Structure of Plage Flux Tubes from the Inversion of Stokes
Spectra. I. Spatially Averaged Stokes I and V Profiles
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
2000ApJ...535..489B Altcode:
We present results of the inversion of spatially averaged Stokes
I and V profiles emerging from plage regions near disk center. The
observations analyzed in this work were recorded with the Advanced
Stokes Polarimeter. All atmospheric quantities determining the
radiative transfer in the thin flux-tube approximation are inferred
self-consistently with the help of the inversion code described by
Bellot Rubio et al. With regard to thermodynamics, the retrieved
model atmospheres are found to behave as expected on theoretical
grounds. For the first time, velocities inside and outside the tubes
have been derived empirically. The magnetic atmospheres resulting from
the inversion are characterized by the absence of significant motions in
high layers but show strong velocity gradients in deeper layers. These
gradients turn out to be essential for reproducing the whole shape
of the observed profiles and, in particular, the asymmetries and the
extended red tail of Stokes V. Our scenario predicts that the Stokes
V zero-crossing wavelengths of Fe I and Fe II lines are redshifted
by small but nonnegligible amounts, which is indeed confirmed by
observations made with the Fourier Transform Spectrometer. According
to recent numerical simulations, the internal downflows derived from
the inversion could be produced by the strong shear that takes place
in the intermediate layer between the magnetized interior and the
ambient medium. Another possible origin is magnetic flux undergoing
convective collapse within the resolution element.

---------------------------------------------------------
Title: Oscillations in the Photosphere of a Sunspot Umbra from the
Inversion of Infrared Stokes Profiles
Authors: Bellot Rubio, L. R.; Collados, M.; Ruiz Cobo, B.; Rodríguez
Hidalgo, I.
2000ApJ...534..989B Altcode:
We report on the detection of magnetic field strength and velocity
oscillations in the photosphere of a sunspot umbra. Our analysis is
based on the inversion of the full Stokes vector of three Fe I lines
at 15650 Å, from which the stratification with optical depth of the
different atmospheric parameters has been derived. This allows us to
estimate the amplitude of the oscillations and the phase lag between
the fluctuations in the line-of-sight velocity and field strength. Our
results suggest that the inferred magnetic field oscillations are caused
by opacity fluctuations that move upward and downward the region where
the spectral lines are sensitive to magnetic fields.

---------------------------------------------------------
Title: Inversion of Stokes Profiles from Solar Magnetic Elements
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
2000ApJ...535..475B Altcode:
We describe a new LTE inversion code for the analysis of Stokes
profiles emerging from unresolved magnetic elements. It has been
specifically designed to obtain the thermal, dynamic, and magnetic
properties of these structures in a self-consistent manner by fitting
the whole shape of the observed spectra. The inversion code is based on
a previous scheme by Ruiz Cobo &amp; del Toro Iniesta and implements
the thin flux-tube model as a reasonable description of reality. All
physical parameters considered relevant for the problem (including
velocity fields) are retrieved by means of a Marquardt nonlinear
least-squares algorithm. We present the results of extensive tests
aimed at characterizing the behavior of the code so as to understand
its limitations for the analysis of real observations. The code is
found to produce accurate results even with only two spectral lines and
noisy Stokes I and V profiles. A detailed error treatment, in which
the covariances between parameters are explicitly included, is also
carried out in order to investigate the uniqueness and reliability of
the inferred model atmospheres.

---------------------------------------------------------
Title: Bulletin 15 of the International Leonid Watch: First Global
Analysis of the 1999 Leonid Storm
Authors: Arlt, R.; Bellot Rubio, L.; Brown, P.; Gyssens, M.
1999JIMO...27..286A Altcode:
An overall activity profile of the 1999 Leonid meteor shower is
presented based on the observations of 434 observers who reported
277172 Leonids in 10806 observing periods. A storm of Leonid activity
was observed from western Asian, European, and African locations at a
solar longitude of lambda=235.285+-0.001, corresponding to November 18,
1999, 2h02m+-2m UT with a peak equivalent ZHR of 3700+-100 based on
2.8-minute intervals. Solar longitudes refer to equinox J2000.0. The
flux density of particles causing meteors brighter than magnitude
+6.5 is 1.4+-0.3 particles per square kilometer and per hour. This
corresponds to a number density of 5400+-1200 particles per 10^9
cubic kilometer. Additional maxima were found in the ZHR peak profile;
one of them at lambda=235.272 or 1h43m UT can be associated with the
cometary ejecta from the 1932 perihelion passage. The time of this
peak as well as the main peak, which is caused by particles from the
1899 passage, are reproduced by particle simulations. A clear second
activity outburst occurred at lambda=235.87+-0.04 (November 18, 1999,
16h+-1h UT) with a maximum ZHR of 180+-20. The Leonid storm component
is found to exhibit an unusual magnitude distribution with a lack of
both very bright and very faint meteors.

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Title: Formation and Destruction of a Weak Magnetic Feature in the
Solar Photosphere
Authors: Khomenko, E.; Collados, M.; Bellot Rubio, L. R.; Rodríguez
Hidalgo, I.; Ruiz Cobo, B.
1999ESASP.448..307K Altcode: 1999mfsp.conf..307K; 1999ESPM....9..307K
No abstract at ADS

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Title: Video Observations Of Leonids 1999
Authors: Molau, Sirko; Rendtel, Jürgen; Bellot-Rubio, Luis Ramon
1999EM&P...87....1M Altcode:
We analyse data obtained by different ground-based video camera systems
during the 1999 Leonid meteor storm. We observe similar activity
profiles at nearby observing sites, but significant differences over
distances in the order of 4,000 km. The main peak occured at 02:03
UT (λ⊙=235.286, J2000, corrected for the time of the
topocentric stream encounter). At the Iberian peninsula quasi-periodic
activity fluctuations with a period of about 7 min were recorded. The
camera in Jordan detected a broad plateau of activity at 01:39-01:53
UT, but no periodic variations. The Leonid brightness distribution
derived from all cameras shows a lack of faint meteors with a turning
point close to +3m, which corresponds to meteoroids of
approximately 10-3 g. We find a pin-point radiant at
αalpha=153.65 ±0.1, δ=21.80 ±0. (λ⊙=235.290). The
radiant positionis identical before and after the storm, and also
during the storm no driftis observed.

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Title: TIP: The Tenerife Infrared Polarimeter
Authors: Martínez Pillet, V.; Collados, M.; Bellot Rubio, L. R.;
Rodríiguez Hidalgo, I.; Ruiz Cobo, B.; Soltau, D.
1999AGAb...15...89M Altcode: 1999AGM....15..P05M
The aim of the IAC Tenerife Infrared Polarimeter is to obtain
quantitative measurements of the polarization state of the solar
radiation collected in near-infrared wavelengths by the Gregory Coudé
Telescope and the Vacuum Tower Telescope of the Observatorio del Teide
(Spain). In this contribution we describe the analyzer, instrumental
calibration, and detector subsystems of TIP, and give details concerning
the specifications of the instrument.

---------------------------------------------------------
Title: Structure of a Facular Region From the Inversion of High
Spatial and Temporal Resolution Stokes Spectra
Authors: Bellot Rubio, L.; Ruiz Cobo, B.; Collados, M.
1999ASPC..183...61B Altcode: 1999hrsp.conf...61B
No abstract at ADS

---------------------------------------------------------
Title: An LTE code for the inversion of Stokes spectra from solar
magnetic elements
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
1999ASSL..243..271B Altcode: 1999sopo.conf..271B
No abstract at ADS

---------------------------------------------------------
Title: TIP (Tenerife Infrared Polarimeter): a near IR full Stokes
Polarimeter for the German Solar Telescopes at Observatorio del Teide
Authors: Collados, M.; Rodríguez Hidalgo, I.; Bellot Rubio, L.;
Ruiz Cobo, B.; Soltau, D.
1999AGAb...15Q..11C Altcode: 1999AGM....15..A13C
In this contribution, the main characteristics of the=20 Tenerife
Infrared Polarimeter (TIP), recently built at the Instituto de
Astrofísica de Canarias, to be operated at the German Solar
Telescopes (GCT and VTT) of the Observatorio del Teide (Tenerife)
are presented. Especial emphasis is put on the modulation scheme,
polarisation efficiencies, signal-to-noise ratio, spatial and spectral
resolution, and instrumental polarisation cross-talk. Some examples
of data recently obtained are presented, which give an idea of the
performance and capabilities of this instrument.

---------------------------------------------------------
Title: The Hermitian solution of the radiative transfer equation
for non-LTE problems
Authors: Ruiz Cobo, B.; Bellot Rubio, L. R.; Collados, M.
1999ASSL..243..231R Altcode: 1999sopo.conf..231R
No abstract at ADS

---------------------------------------------------------
Title: Probing downflows in solar magnetic elements: the Fe II test
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
1999A&A...341L..31B Altcode:
In an attempt to assess the physical realism of the plage flux tube
model derived by Bellot Rubio, Ruiz Cobo &amp; Collados (\cite{brc},
\cite{bellot}) we extend its predictions to the Stokes V zero-crossing
shifts of a number of Fe ii lines. For this analysis, accurate Fe
ii central wavelengths are required. We have devised a procedure for
bringing the available Fe ii laboratory wavelengths to the system of
accurate Fe i wavelengths of Nave et al. (\cite{nav}). It is shown that,
relative to this system, the Fe ii system of Kurucz (\cite{kur}) is
shifted by 6.4 m Angstroms/ towards longer wavelengths. Some lines,
however, are displaced by more than 10 m Angstroms/. Corrected
central wavelengths have been used to extract the observed Stokes
V zero-crossing shifts of 16 Fe ii lines. Comparison with the
values resulting from the model of Bellot Rubio et al. (\cite{brc},
\cite{bellot}) suggests that the velocity gradients derived by these
authors are esentially correct.

---------------------------------------------------------
Title: The IAC Stokes profile inversion codes
Authors: Bellot Rubio, L. R.
1999AGAb...15...90B Altcode: 1999AGM....15..P06B
In this contribution I describe the main characteristics of the
inversion codes developed at the Instituto de Astrofísica de Canarias
for the analisys of Stokes profiles emerging from single (magnetized
or non-magnetized) atmospheres and thin flux tubes. Some results of
the application of these codes to real data, including infrared Stokes
profiles recorded with the Tenerife Infrared Polarimeter, are presented
as well.

---------------------------------------------------------
Title: Oscillations in a sunspot umbra from the inversion of infrared
Stokes profiles
Authors: Bellot Rubio, Luis R.; Collados, Manuel; Ruiz Cobo, Basilio;
Rodríguez Hidalgo, Inés; Bogdan, Thomas J.
1999AGM....15..A07B Altcode:
We report on the detection of magnetic field strength and velocity
oscillations in the photosphere of a sunspot umbra. Our analysis is
based on the inversion of the full Stokes profiles of three Fe I lines
at 15650 Å, from which the stratification with optical depth of the
different atmospheric parameters has been derived. This allows us to
estimate the amplitude of the oscillations and the phase lag between
the fluctuations in the line-of-sight velocity and field strength. Our
results suggest that the inferred magnetic field oscillations are caused
by opacity fluctuations that move upward and donward the region where
the spectral lines are sensitive to magnetic fields.

---------------------------------------------------------
Title: An Hermitian Method for the Solution of Polarized Radiative
Transfer Problems
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
1998ApJ...506..805B Altcode:
Spectral synthesis calculations in stellar (magnetized) atmospheres
are based on the solution of the radiative transfer equation (RTE)
for polarized light. The thermodynamic and magnetic properties of the
atmospheres, along with the radiation field, completely specify the
basic ingredients of the RTE, after which numerical methods have to
be employed to calculate the emergent Stokes spectra. The advent of
powerful analysis techniques for the inversion of Stokes spectra has
evidenced the need for accurate and fast solutions of the RTE. In
this paper we describe a novel Hermitian strategy to integrate the
polarized RTE that is based on the Taylor expansion of the Stokes
parameter vector to fourth order in depth. Our technique makes use
of the first derivatives of the absorption matrix and source vector
with respect to the coordinate measured along the ray path. Both
analytical and numerical results indicate that the new strategy is
superior to other methods in terms of speed and accuracy. It also gives
an approximation to the evolution operator at no extra cost, which is
of interest for inversion algorithms based on response functions. The
Hermitian technique can be straightforwardly particularized to the
scalar case, providing a very efficient solution of the RTE in the
absence of magnetic fields. We investigate in detail the consequences
of the oscillations that appear in the evolution operator for large
values of line strength η0. The problems they pose are
shared by all integration schemes, but can be minimized by adopting
nonequally spaced grids.

---------------------------------------------------------
Title: Observation and Interpretation of Meteoroid Impact Flashes
on the Moon
Authors: Bellot Rubio, Luis R.; Ortiz, Jose L.; Sada, Pedro V.
1998EM&P...82..575B Altcode: 2000EM&P...82..575B
The first unambiguous detection of meteoroids impacting the night
side of the Moon was obtained during the 1999 Leonid storm. Up
to eight optical flashes were recorded with CCD video cameras
attached to small telescopes on November 18, 1999. Six impacts were
videotaped by at least two independent observers at the same times
and lunar locations, which is perhaps the strongest evidence for their
collisional nature. The flashes were clearly above the noise and lasted
for less than 0.02 s. Although previous observational efforts did not
succeed in detecting impact flashes, additional candidates have been
reported in the literature. The evidence accumulated so far implies
that small telescopes equipped with high speed cameras can be used
as a new tool for studying meteoroid streams, sporadic meteoroids,
and hypervelocity collisions. In this review we discuss the various
intervening parameters for detectability of flashes on the night side
of the Moon (geometrical effects, contamination by scattered light
from the day side, and properties of the meteoroids such as speed and
flux of particles). Particular emphasis is placed on the analysis of
the observations in order to derive relevant physical parameters such
as luminous efficiencies, impactor masses, and crater sizes. Some of
these parameters are of interest for constraining theoretical impact
models. From a simple analysis, it is possible to derive the mass
distribution of the impactors in the kg range. A more elaborate analysis
of the data permits an estimate of the fraction of kinetic energy
converted to radiation (luminous efficiency) if the meteoroid flux on
the Moon is known. Applied to the 1999 lunar Leonids, these methods
yield a mass index of 1.6 +/- 0.1 and luminous efficiencies of 2 ×
10^-3 with an uncertainty of about one order of magnitude. Predictions
of visibility of the major annual meteor showers are given for the
next few years. These include the forthcoming 2001 Leonid return,
for which we estimate detection rates in the visible.

---------------------------------------------------------
Title: Structure of solar magnetic elements from inversion of
Stokes spectra
Authors: Bellot Rubio, Luis Ramon
1998PhDT........24B Altcode:
No abstract at ADS

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Title: The Rotation of Comet 1995 O1 (Hale-Bopp) at Perihelion
Authors: Kidger, M.; Licandro, J.; Sabalisk, N.; Goetz, B.; Santos,
P.; Serra-Ricart, M.; Bellot Rubio, L.; Casas, R.; Gomez, A.; Jorda,
L.; Tozzi, G. -P.; Osip, D.; Boehnhardt, H.; West, R.
1997AAS...191.8801K Altcode: 1997BAAS...29.1356K
Narrow band near infrared images of comet 1995 O1 (Hale-Bopp), where
obtained in day-time, during April 1997, using the 1.52m Carlos
Sanchez Telescope, at Teide Observatory (Tenerife, Spain), by the
Comet Hale Bopp European Team. The comet was observed continuously
for up to 11 hours hours each day on a total of 15 days. This allows
us to obtain a complete map of the rotation of the comet's nucleus,
and the evolution of the structures observed in the inner coma. These
observations were part of a long-term monitoring campaign of the comet's
inner-coma morphology which started in August 1995. A long-enduring
polar fan structure was observed on 76 nights pre-perihelion, from
March to September 1996, in broadband R CCD images obtained with the
0.82m IAC-80 and 0.5m Mons telescopes at Teide Observatory. These
images allow us to obtain the spin axis orientation of the comet with
considerable precision. Preliminary results, combining these data sets,
are presented on the rotation period, pole orientation, and evolution
of the active zones.

---------------------------------------------------------
Title: Precisely reduced meteoroid trajectories and orbits from the
1995 Leonid meteor outburst
Authors: Betlem, Hans; Kuile, Casper Ter; van't Leven, Jaap; de Lignie,
Marc; Bellot Rubio, Luis Ramon; Koop, Mike; Angelo, Chris; Wilson,
Mike; Jenniskens, Peter
1997P&SS...45..853B Altcode:
The discovery of enhanced Leonid activity in 1994 led to the mounting
of a multi-station photographic campaign on two continents during the
Leonids of 1995. The goal was to determine orbits and trajectories of
outburst Leonids. The outburst did recur as predicted, resulting in 23
precisely reduced Leonid orbits and 30 Leonid trajectories. Individual
velocities and radiant positions, as well as the average orbit are
presented. It is found that the distribution of Leonid radiants
contains a dense cluster of seven radiant positions. This clustering
is tentatively associated with the visually observed outburst
component. These seven meteors provide the first orbital elements of
outburst Leonids and put strong constraints on theoretical models of
the origin and evolution of the Leonid stream.

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Title: A Comparison Between Near-Infrared And Visible Imaging Of
The Inner Coma Of Comet Hale-Bopp At Perihelion
Authors: Santos-Sanz, P.; Sabalisck, N.; Kidger, M. R.; Licandro,
J.; Serra-Ricart, M.; Bellot Rubio, L. R.; Casas, R.; Gómez, A.;
Sánchez Portero, J.; Osip, D.
1997EM&P...78..235S Altcode:
We present a comparison between images of comet C/1995 O1 (Hale-Bopp)
obtained from 12 March to 9 May 1997, with two telescopes of the
Observatorio del Teide (IAC, Tenerife, Spain) in visible (Johnson-V
filter) and three near-infrared narrowband filters (Brγ (2.166 μm),
CO (2.295 μm), and Kcon (2.260 μm)). No significant
differences are observed between the images in the three near-infrared
bands suggesting that any CO emission is very weak, or produced by
an extended flat source. We do not find evidence for the existence of
an additional infrared component due to emission by warm dust, or to
dust grains of diverse composition and/or size. Visible and infrared
images of the same rotational phase look almost identical, supporting
the view that the observed jets and shells are mainly dust structures.

---------------------------------------------------------
Title: The Spin Axis Position of C/1995 O1 (Hale-Bopp)
Authors: Licandro, J.; Bellot Rubio, L. R.; Casas, R.; Gómez, A.;
Kidger, M. R.; Sabalisk, N.; Santos-Sanz, P.; Serra-Ricart, M.;
Torres-Chico, R.; Oscoz, A.; Jorda, L.; Denicolo, G.
1997EM&P...77..199L Altcode:
Monitoring of the near-nucleus activity of C/1995 O1 (Hale-Bopp)
began in Teide Observatory in August 1995. During 1996 the comet was
observed on 72 nights between March 26 and November 13. A permanent fan
structure was observed towards the north during the whole period of
observation. The position angle of the axis of this fan was measured
and its variations with time were used to determine the position of
the North Pole of the cometary nucleus.

---------------------------------------------------------
Title: Flux-Tube Model Atmospheres and Stokes V Zero-crossing
Wavelengths
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
1997ApJ...478L..45B Altcode: 1997astro.ph..1059B; 1997astro.ph..1059R
First results of the inversion of Stokes I and V profiles from plage
regions near disk center are presented. Both low and high spatial
resolution spectra of Fe I 6301.5 and Fe I 6302.5 Å obtained with the
Advanced Stokes Polarimeter (ASP) have been considered for analysis. The
thin flux-tube approximation, implemented in an LTE inversion code
based on response functions, is used to describe unresolved magnetic
elements. The code allows the simultaneous and consistent inference of
all atmospheric quantities determining the radiative transfer with the
sole assumption of hydrostatic equilibrium. By considering velocity
gradients within the tubes, we are able to match the full ASP Stokes
profiles. The magnetic atmospheres derived from the inversion are
characterized by the absence of significant motions in high layers
and strong velocity gradients in deeper layers. These are essential
to reproduce the asymmetries of the observed profiles. Our scenario
predicts a shift of the Stokes V zero-crossing wavelengths, which
is indeed present in observations made with the Fourier Transform
Spectrometer.

---------------------------------------------------------
Title: (Erratum) Response functions for the inversion of data from
unresolved solar magnetic elements.
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
1997A&A...319.1036B Altcode:
Erratum to Astron. Astrophys. 306, 960 (1996).

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Title: Evolution of a Spiral Jet in the Inner Coma of Comet Hale-Bopp
(1995 O1)
Authors: Kidger, Mark R.; Serra-Ricart, Miquel; Bellot Rubio, Luis R.;
Casas, Ricard
1996ApJ...461L.119K Altcode:
We present observations of the evolution of a prominent spiral jet in
the inner coma of comet Hale-Bopp (1995 O1). The observations, taken
with the 82 cm IAC-80 telescope at the Teide Observatory, were made on
1995 August 25, 27, 28, and 31, and on September 4--7, as part of an
ongoing program of monitoring the comet in Tenerife. The jet is observed
to show a nearly, but not completely, constant position angle over the
two weeks of observation. Although it is generally assumed that the
jet is a dust event, some aspects of the morphology and behavior mean
that the hypothesis that it is a gas jet cannot be ruled out. No single
hypothesis is thought to be completely satisfactory. Between our first
detection of the jet on August 25 and its disappearance on September
7, we see the point of inflection within the jet expand away from the
nucleus at a highly constant velocity. At the same time, the jet fades
considerably. This jet event seems different from others that have
been observed later because the collimation of the beam is very tight,
rather than the highly wound spiral structure shown by some later jets.

---------------------------------------------------------
Title: Response functions for the inversion of data from unresolved
solar magnetic elements.
Authors: Bellot Rubio, L. R.; Ruiz Cobo, B.; Collados, M.
1996A&A...306..960B Altcode:
By adopting the thin flux tube model as representative of spatially
unresolved magnetic elements in the photosphere of the Sun, we
identify an adequate set of parameters for the model and derive
the corresponding response functions (RFs) which inform about the
variation of the emergent Stokes spectrum when such parameters are
perturbed. We numerically compute these RFs for reasonable values of
the parameters and explore their main properties. It turns out that
the RFs at a given height often depend on the state of layers above as
a result of the constraints imposed by flux tube geometry. As a whole,
RFs can be classified into two well defined groups: one containing RFs
dominated by local effects and another which contains RFs governed by
non-local effects (i.e., contributions coming from layers other than
that where the perturbation takes place). In particular, the RFs to
the temperature, line of sight velocity and microturbulence of both
the internal and the external atmospheres belong to the first group,
while the RFs to the magnetic field strength, external gas pressure and
radius of the tube at the base of the atmosphere must be ascribed to
the second group. The RFs presented in this paper constitute a first
step for the inversion of Stokes spectra from faculae and the network.

---------------------------------------------------------
Title: Determination of fragmentation parameters from photographic
and video data
Authors: Bellot Rubio, L. R.
1996pimo.conf...35B Altcode:
In this paper we introduce the modeling of meteor light curves
obtained by photographic and video observations. We briefly comment
on the physical relevance of the available models for the interaction
atmosphere-meteoroid, and select the quasi-continuous fragmentation
theory as a best general description. The analysis of light curves
makes it possible to derive some parameters of the particles, among
them their bulk densities. By producing synthetic light curves we
explore a successful analysis. It is concluded that measurements of
brightness have to be as accurate as 0.1-0.2 mag to uniquely distinguish
fragmenting behavior.

---------------------------------------------------------
Title: Morphology and Evolution of the Spiral Jets Observed in the
Inner Coma of Comet Hale-Bopp (1995 O1): the 1995 Teide Observing
Campaign
Authors: Kidger, M. R.; Serra-Ricart, M.; Bellot Rubio, L.;
Torres-Chico, R.; Casas, R.; Chinarro, L. M.; Gomez, A.; Lopez, S.;
Manade, L.; Shulman, L.
1995AAS...187.4210K Altcode: 1995BAAS...27.1338K
CCD monitoring of Comet Hale-Bopp (1995 O1) has been carried out on more
than 50 nights using the 82cm IAC-80 Telescope at Teide Observatory
(Tenerife, Spain), operated by the Instituto de Astrofísica de
Canarias. A combination of deep exposures of the extended coma in
BVRI (up to 2 hours total exposure in a single filter) and near
nucleus imaging has been carried out. Major jets were observed in
late August, late September and mid-October which were followed from
first detection to complete disappearance. We present a video of the
evolution of the different events which shows both similarities and
important differences between their morphology and evolution. The
August and October events feature a structure with a straight,
highly collimated jet of increasing projected length with time and
a so-called “spiral arm" which in all three jets ends in a similar
PA, close to the anti-solar direction. These jets we interpret on the
basis of various models in an attempt to derive basic parameters such
as the rotation and axial inclination, as well as the position of the
three sites on the nucleus. There is strong evidence that the three
events are caused by different active points on the nucleus, sited
at different latitudes. We also present light curves of the comet for
different apertures (near-nucleus and total coma) which are linked to
the different jet events.

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Title: Alpha Monocerotid Meteors 1995
Authors: Spurny, P.; Borovicka, J.; Gomez, A.; Bellot Rubio, L.;
Roman, A.; Reyes, F.; Rendtel, J.; Molau, S.; Forti, G.; Haver, R.;
Gorelli, R.; Nagy, Z. A.; Sarenczky, K.; Tepliczky, I.; Gerbos, J.;
Rapavy, P.; Hrusovsky, V.; Steyaert, C.; de Meyere, M.
1995IAUC.6265....1S Altcode:
Numerous reports have been received, from several locations in Europe,
of an excellent display of this occasional, short-lived meteor shower
around Nov. 22.06 UT. Mentioned by Olivier (1936, Pop. Astron. 44,
88) as perhaps having a 10-year periodicity, and discussed at length
by Kresak (1958, Bull. Astron. Inst. Czech. 9, 88), the shower
was widely anticipated to recur in 1995, Jenniskens (1995, WGN 23,
No. 3, 84) predicting the brief maximum as occurring some time during
Nov. 22.00-22.25 UT. P. Spurny and J. Borovicka, Ondrejov Observatory,
report monitoring during Nov. 21.96-22.11, Monocerotids first being
detected at 22.050, with more than six during each 2-min interval until
22.067 and some continuing activity to 22.098; during one minute at
22.058 a maximum of seven meteors was observed. A. Gomez, Instituto
de Astrofisica de Canarias, reports observations from Almeria by
L. Bellot, A. Roman and F. Reyes of as many as 70 Monocerotids during
22.055-22.071; the limiting visual magnitude was about 6.2, and most of
the meteors were in the magnitude range 0-2. J. Rendtel, International
Meteor Organization, Potsdam, noted 34 shower meteors from a radiant of
R.A. = 113 deg, Decl. = -3 deg during 22.042-22.076 (limiting magnitude
6.15), yielding an average ZHR (assuming a population index of r = 2.5)
of 90 (with an equivalent ZHR of up to 190 during 10 min centered on
22.062; on combining his results with those of S. Molau in Chemnitz,
he revised this to 220 +/- 50). G. Forti, Arcetri Observatory,
reports observations by R. Haver and R. Gorelli from Frasso Sabino,
indicating a radiant of R.A. = 112.5 deg, Decl. = -3 deg and a peak
within 5 min of 22.059, there being a sharp rise and fall and no meteors
observed 15 min before or after the peak; the meteors were yellow and
blue, and few were brighter than mag 0. Z. A. Nagy, K. Sarenczky and
I. Tepliczky, observing from Vertes Mountain (Hungary), collectively
recorded Monocerotids during 22.045-22.087, counting 139 shower members
during 22.049-22.072 (with maximum activity during 22.060-22.065),
90 percent of them from a compact radiant at R.A. = 116 deg, Decl. =
+4 deg, and the others from a diffuse radiant between alpha CMi and
delta Mon; several meteors were around mag 0. J. Gerbos, P. Rapavy and
V. Hrusovsky, Rimavska Sobota (Slovakia), collectively registered more
than 600 Monocerotids during one hour beginning 22.049, the maximum
activity in 5 min being centered on 22.058. C. Steyaert reports that
M. De Meyere, monitoring in Deurle (Belgium) a 100-kW radio station
in Budapest, 1170 km away, at 66.51 MHz, detected a significant
(fourfold) enhancement in forward-scattering rates during the hour
beginning 22.042, the number of meteor reflections lasting at least
0.027 second being 232.

---------------------------------------------------------
Title: Effects of a dependence of meteor brightness on the entry
angle.
Authors: Bellot Rubio, L. R.
1995A&A...301..602B Altcode:
In this paper we discuss the observational consequences of a dependence
of meteor brightness on the entry angle z_R_, namely the decrease
of the observed rates of meteors and the reduction of the population
indices r for radiant zenith distances larger than zero. These effects,
if not properly accounted for, lead to erroneous values of meteor shower
activity. The first one is corrected by applying a factor cos^-γ^ z_R_
to the observed rates, while the second one requires a correction of
the form r(0deg)=r(z_R_)^b(z_R_)/b(0deg)^. We give general expressions
for γ and b(z_R_)/b(0deg) in terms of the coefficients relating the
absolute magnitude of the meteor to its physical parameters. High
quality photographic data, as well as naked-eye observations,
are analyzed. It turns out that γ=1+1.53logr(0deg) describes the
photographic behavior quite well. For visual observations, however,
an exponent γ=1 should be employed in most cases. We explain this
difference on the basis of a larger path of the meteoroids at increasing
entry angles, which increases the probability of perception of
meteors for visual observers. As regards b(z_R_)/b(0deg), a dependence
b(z_R_)/b(0deg)=1.04-0.04cos z_R_ is suitable for both photographic and
naked-eye records. These values are compared to predictions resulting
from a detailed treatment of the single body theory. It turns out
that the single body approach gives a much stronger dependence of
the meteor brightness on the entry angle than that obtained from
observations. Models including quasicontinuous fragmentation are
therefore necessary.

---------------------------------------------------------
Title: LTE polarized radiative transfer through interlaced
atmospheres.
Authors: del Toro Iniesta, J. C.; Ruiz Cobo, B.; Bellot Rubio, L. R.;
Collados, M.
1995A&A...294..855D Altcode:
We show that the solution of the radiative transfer equation (RTE)
through a line of sight that pierces several times two alternate
atmospheres can be obtained in terms of the solutions of the RTE
through both single atmospheres separately considered. This also
applies to the response functions of the observed Stokes spectrum
to perturbations of the physical quantities. The analytic solution
of the RTE in case that the single atmospheres are Milne-Eddington
is presented. The simplification of the solution in the case of a
longitudinal or transversal (with constant azimuth) magnetic field
is presented as well. Finally, as a numerical example, we synthesize
the Stokes I- and V-spectrum emerging from a thin magnetic flux tube,
achieving a considerable decrease in computation time with respect to
conventional integrations and without loss of accuracy.

---------------------------------------------------------
Title: An analysis of the Taurid radiants.
Authors: Bellot Rubio, L. R.
1994JIMO...22..108B Altcode: 1994WGN....22..108B
No abstract at ADS

---------------------------------------------------------
Title: Spatial number densities and errors from photographic meteor
observations under very high activity.
Authors: Bellot Rubio, L. R.
1994JIMO...22..118B Altcode: 1994WGN....22..118B
A procedure to compute meteoroid spatial number densities from
photographs is presented. It follows from the visual method of
Koschack and Rendtel with slight changes. Some parameters are
recomputed and hints are given on how to produce useful photographic
observations. Finally, an analysis of the expected errors is performed.

---------------------------------------------------------
Title: Dependence of the population index on the radiant zenithal
distance
Authors: Bellot Rubio, Luis R.
1994JIMO...22...13B Altcode: 1994WGN....22...13B
By integrating the differential equation system of the single-body
meteor theory which describes meteor flight in the atmosphere, we show
that the population index r depends on the radiant zenithal distance
zR. When zR is large, r diminishes, requiring
correction in order to obtain reliable number density profiles. A new
method is proposed to correct the population index when zR
is not zero. Its application to the problem of the 1992 Quadrantids
raised by Rendtel et al. shows that corrected values of r vary from
r=2.32 to r=2.44 between solar longitudes 283.00 and 283.23 deg.

---------------------------------------------------------
Title: On the presence of trains in meteor showers.
Authors: Bellot Rubio, L. R.
1992JIMO...20..140B Altcode: 1992WGN....20..140B
Different mechanisms for meteor train generation are reviewed. Train
percentages for different showers are calculated and compared. An
attempt is made to correlate numbers of trains with train
duration. Finally, fireball trains are considered.

---------------------------------------------------------
Title: 1992 Quadrantid and Coma Berenicid activity in Spain.
Authors: Bellot Rubio, L. R.
1992JIMO...20...93B Altcode: 1992WGN....20...93B
No abstract at ADS

---------------------------------------------------------
Title: The α-Capricornids in 1989.
Authors: Bellot Rubio, L. R.
1990JIMO...18...26B Altcode: 1990WGN....18...26B
No abstract at ADS