Author name code: gandorfer
ADS astronomy entries on 2022-09-14
author:"Gandorfer, Achim"
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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.
Bibcode: 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.
Title: Development of Fast and Precise Scan Mirror Mechanism for an
Airborne Solar Telescope
Authors: Oba, Takayoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Kubo,
Masahito; Kawabata, Yusuke; Hara, Hirohisa; Uraguchi, Fumihiro;
Tsuzuki, Toshihiro; Tamura, Tomonori; Shinoda, Kazuya; Kodeki,
Kazuhide; Fukushima, Kazuhiko; Morales Fernández, José Miguel;
Sánchez Gómez, Antonio; Balaguer Jimenéz, María; Hernández
Expósito, David; Gandorfer, Achim
Bibcode: 2022arXiv220713864O
Altcode:
We developed a scan mirror mechanism (SMM) that enable a slit-based
spectrometer or spectropolarimeter to precisely and quickly map
an astronomical object. The SMM, designed to be installed in the
optical path preceding the entrance slit, tilts a folding mirror
and then moves the reflected image laterally on the slit plane,
thereby feeding a different one-dimensional image to be dispersed by
the spectroscopic equipment. In general, the SMM is required to scan
quickly and broadly while precisely placing the slit position across
the field-of-view (FOV). These performances are highly in demand for
near-future observations, such as studies on the magnetohydrodynamics of
the photosphere and the chromosphere. Our SMM implements a closed-loop
control system by installing electromagnetic actuators and gap-based
capacitance sensors. Our optical test measurements confirmed that the
SMM fulfils the following performance criteria: i) supreme scan-step
uniformity (linearity of 0.08%) across the wide scan range (${\pm}$1005
arcsec), ii) high stability (3${\sigma}$ = 0.1 arcsec), where the
angles are expressed in mechanical angle, and iii) fast stepping speed
(26 ms). The excellent capability of the SMM will be demonstrated
soon in actual use by installing the mechanism for a near-infrared
spectropolarimeter onboard the balloon-borne solar observatory for
the third launch, Sunrise III.
Title: Polarimetric calibration of the Sunrise UV Spectropolarimeter
and Imager
Authors: Iglesias, F. A.; Feller, A.; Gandorfer, A.; Lagg, A.;
Riethmüller, T. L.; Solanki, S. K.; Katsukawa, Y.; Kubo, M.;
Zucarelli, G.; Sanchez, M.; Sunrise Team
Bibcode: 2022BAAA...63..305I
Altcode:
Sunrise is an optical observatory mounted in a stratospheric balloon,
developed to study magnetic fields in the solar atmosphere with very
high resolution. In its third flight, Sunrise carry the Sunrise UV
Spectropolarimeter and Imager (SUSI), that operates in the 313-430 nm
range, covering thousands of spectral lines not accessible from the
ground and thus largely unexplored. SUSI does not include a polarimetric
calibration unit on board. We report about the development status of
SUSI and the preliminary results of its calibration.
Title: The essential role of Earth-Sun L4 in solar particle event
forecasting for Lunar and Mars exploration
Authors: Posner, Arik; Toit Strauss, Du; Solanki, Sami K.; Effenberger,
Frederic; Gandorfer, Achim; Hirzberger, Johann; Kühl, Patrick; Heber,
Bernd; Malandraki, Olga; Folta, David; Jones, Sarah; Arge, Charles;
Sterken, Veerle; Henney, Carl J.; Staub, Jan; Hatten, Noble; Stcyr,
O. Chris
Bibcode: 2022cosp...44.1157P
Altcode:
We learned from the STEREO mission that solar particle events
originating from behind the west limb of the Sun, i.e., out of view
from Earth, make up about 30 percent of those significantly affecting
Earth's vicinity and thus could endanger human exploration of the
Moon. The Earth-Sun Lagrangian point 4 is a meta-stable location at 1
au from the Sun, 60° ahead of Earth's orbit. L4 has an uninterrupted
view of the solar photosphere centered on W60, the Earth's nominal
magnetic field connection to the Sun. The role of L4 observations
for improving several existing short-term SEP forecasting techniques,
including protons, ESPERTA, UMASEP and pps, for Lunar exploration will
be highlighted. We can show that BFO dose savings from short-term
solar energetic particle forecasts are critically important in a
worst-case scenario. Placing a mission at L4 is even a precondition
for any SEP all-clear forecasting for Lunar exploration. Furthermore,
we analyzed example trajectories of short-term Mars round trips that
may be considered for future human exploration of Mars and find that
L4-based SWx observations would have relevance for protecting Mars
explorers from radiation exposure.
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.
Bibcode: 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.
Title: A Multi-Purpose Heliophysics L4 Mission
Authors: Posner, A.; Arge, C. N.; Staub, J.; StCyr, O. C.; Folta,
D.; Solanki, S. K.; Strauss, R. D. T.; Effenberger, F.; Gandorfer,
A.; Heber, B.; Henney, C. J.; Hirzberger, J.; Jones, S. I.; Kühl,
P.; Malandraki, O.; Sterken, V. J.
Bibcode: 2021SpWea..1902777P
Altcode:
The Earth-Sun Lagrangian point 4 is a meta-stable location at 1 AU from
the Sun, 60° ahead of Earth's orbit. It has an uninterrupted view of
the solar photosphere centered on W60, the Earth's nominal magnetic
field connection to the Sun. Such a mission on its own would serve
as a solar remote sensing observatory that would oversee the entire
solar radiation hemisphere with significant relevance for protecting
Moon and Mars explorers from radiation exposure. In combination with
appropriately planned observatories at L1 and L5, the three spacecraft
would provide 300° longitude coverage of photospheric magnetic field
structure, and allow continuous viewing of both solar poles, with
>3.6° elevation. Ideally, the L4 and L5 missions would orbit the Sun
with a 7.2° inclination out of the heliographic equator, 14.5° out of
the ecliptic plane. We discuss the impact of extending solar magnetic
field observations in both longitude and latitude to improve global
solar wind modeling and, with the development of local helioseismology,
the potential for long-term solar activity forecasting. Such a mission
would provide a unique opportunity for interplanetary and interstellar
dust science. It would significantly add to reliability of operational
observations on fast coronal mass ejections directed at Earth and
for human Mars explorers on their round-trip journey. The L4 mission
concept is technically feasible, and is scientifically compelling.
Title: SUNRISE Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: Scan mirror mechanism
Authors: Oba, Takayoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Kubo,
Masahito; Uraguchi, Fumihiro; Tsuzuki, Toshihiro; Tamura, Tomonori;
Shinoda, Kazuya; Kodeki, Kazuhide; Fukushima, Kazuhiko; Gandorfer,
Achim; del Toro Iniesta, Jose Carlos
Bibcode: 2020SPIE11445E..4FO
Altcode:
The SUNRISE Chromospheric Infrared spectroPolarimeter (SCIP) is a
balloon-borne long-slit spectrograph for SUNRISE III to precisely
measure magnetic fields in the solar atmosphere. The scan mirror
mechanism (SMM) is installed in the optical path to the entrance slit
of the SCIP to move solar images focused on the slit for 2-dimensional
mapping. The SMM is required to have (1) the tilt stability better
than 0.035″ (3σ) on the sky angle for the diffraction-limited
spatial resolution of 0.2″, (2) step response shorter than 32 msec
for rapid scanning observations, and (3) good linearity (i.e. step
uniformity) over the entire field-of-view (60″x60″). To achieve
these performances, we have developed a flight-model mechanism
and its electronics, in which the mirror tilt is controlled by
electromagnetic actuators with a closed-loop feedback logic with
tilt angles from gap-based capacitance sensors. Several optical
measurements on the optical bench verified that the mechanism meets
the requirements. In particular, the tilt stability achives better
than 0.012″ (3σ). Thermal cycling and thermal vacuum tests have
been completed to demonstrate the performance in the vacuum and the
operational temperature range expected in the balloon flight. We
found a small temperature dependence in the step uniformity and this
dependence will be corrected to have 2-demensional maps with the
sub-arcsec spatial accuracy in the data post-processing.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: optical design and performance
Authors: Tsuzuki, Toshihiro; Katsukawa, Yukio; Uraguchi, Fumihiro;
Hara, Hirohisa; Kubo, Masahito; Nodomi, Yoshifumi; Suematsu, Yoshinori;
Kawabata, Yusuke; Shimizu, Toshifumi; Gandorfer, Achim; Feller, Alex;
Grauf, Bianca; Solanki, Sami; Carlos del Toro Iniesta, Jose
Bibcode: 2020SPIE11447E..AJT
Altcode:
The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is a
near-IR spectro-polarimeter instrument newly designed for Sunrise III,
which is a balloon-borne solar observatory equipped with a 1 m optical
telescope. To acquire high-quality 3D magnetic and velocity fields,
SCIP selects the two wavelength bands centered at 850 nm and 770 nm,
which contain many spectrum lines that are highly sensitive to magnetic
fields permeating the photosphere and chromosphere. To achieve high
spatial and spectral resolution (0.21 arcsec and 2 × 105),
SCIP optics adopt a quasi-Littrow configuration based on an echelle
grating and two high-order aspheric mirrors. Using different diffraction
orders of the echelle grating, dichroic beam splitter, and polarizing
beam-splitters, SCIP can obtain s- and p-polarization signals in the
two wavelength bands simultaneously within a relatively small space. We
established the wavefront error budget based on tolerance analysis,
surface figure errors, alignment errors, and environmental changes. In
addition, we performed stray light analysis, and designed light traps
and baffles needed to suppress unwanted reflections and diffraction
by the grating. In this paper, we present the details of this optical
system and its performance.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: opto-mechanical analysis and design
Authors: Uraguchi, Fumihiro; Tsuzuki, Toshihiro; Katsukawa, Yukio;
Hara, Hirohisa; Iwamura, Satoru; Kubo, Masahito; Nodomi, Yoshifumi;
Suematsu, Yoshinori; Kawabata, Yusuke; Shimizu, Toshifumi; Gandorfer,
Achim; del Toro Iniesta, Jose Carlos
Bibcode: 2020SPIE11447E..ABU
Altcode:
The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is a
near-IR spectro-polarimeter instrument newly designed for Sunrise III,
a balloon-borne solar observatory with a 1-m diameter telescope. In
order to achieve the strict requirements the SCIP wavefront error, it is
necessary to quantify the errors due to environmen- tal effects such as
gravity and temperature variation under the observation conditions. We
therefore conducted an integrated opto-mechanical analysis incorporating
mechanical and thermal disturbances into a finite element model of
the entire SCIP structure to acquire the nodal displacements of each
optical element, then fed them back to the optical analysis software
in the form of rigid body motion and surface deformation fitted by
polynomials. This method allowed us to determine the error factors
having a significant influence on optical performance. For example,
no significant wavefront degradation was associated with the structural
mountings because the optical element mounts were well designed based
on quasi-kinematic constraints. In contrast, we found that the main
factor affecting wavefront degradation was the rigid body motions of
the optical elements, which must be mini- mized within the allowable
level. Based on these results, we constructed the optical bench using a
sandwich panel as the optical bench consisting of an aluminum-honeycomb
core and carbon fiber reinforced plastic skins with a high stiffness
and low coefficient of thermal expansion. We then confirmed that the
new opto-mechanical model achieved the wavefront error requirement. In
this paper, we report the details of this integrated opto-mechanical
analysis, including the wavefront error budgeting and the design of
the opto-mechanics.
Title: First results from SO/PHI's on-board data reduction
Authors: Albert, K.; Hirzberger, J.; Kolleck, M.; Albelo Jorge,
N.; Busse, D.; Blanco Rodriguez, J.; Cobos Carrascosa, J. P.;
Fiethe, B.; Gandorfer, A.; Germerott, D.; Guan, Y.; Guerrero, L.;
Gutierrez-Marques, P.; Hernández Expósito, D.; Lange, T.; Michalik,
H.; Orozco Suárez, D.; Schou, J.; Solanki, S. K.; Woch, J. G.
Bibcode: 2020AGUFMSH038..05A
Altcode:
The Polarimetric and Helioseismic Imager (PHI), on-board Solar
Orbiter (SO), is a spectropolarimeter imaging the solar photosphere
at the wavelengths of the Fe I 617.3 nm Zeeman sensitive absorption
line. SO/PHI's aim is to provide data about the magnetic structures and
the line-of-sight (LOS) velocity in the solar atmosphere. For this, it
takes time series of data sets consisting of 2048 x 2048 pixel images of
the Sun at 6 wavelengths, each in 4 different polarisation states. With
the minimum necessary 17 bits pixel depth, one data set amounts to
approx. 0.2 GB. The guaranteed data telemetry for PHI, in contrast,
is only 50 GiB/orbit which would also need to contain any calibration
data obtained on-board, i.e. our flat and dark fields. To cope with
this discrepancy, SO/PHI is performing full data reduction on-board,
including the inversion of the radiative transfer equation. The
downloaded results are science ready data, containing 5 final images: a
total intensity image from nearby the spectral line, the magnetic field
strength, azimuth and inclination (describing the magnetic vector) and
the LOS velocity. This process maximises the science return by reducing
the number of necessary images in a data set, as well as rendering the
download of calibration data unessential. In the commissioning phase
of SO/PHI we used the on-board data reduction system successfully
for the first time. We have calibrated the instrument to its optimal
operational parameters (calculation of exposure time, focus, etc.),
acquired and processed calibration data (dark and flat fields),
removed the most significant instrumental artefacts from the data
(dark field, flat field, polarimetric modulation and polarimetric
cross-talk), and performed the inversion of the radiative transfer
equation. The data have then been compressed to further maximise the
use of our telemetry. This contribution presents and discusses the
final results from this process.
Title: Power spectrum of turbulent convection in the solar photosphere
Authors: Yelles Chaouche, L.; Cameron, R. H.; Solanki, S. K.;
Riethmüller, T. L.; Anusha, L. S.; Witzke, V.; Shapiro, A. I.;
Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; van Noort,
M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2020A&A...644A..44Y
Altcode: 2020arXiv201009037Y
The solar photosphere provides us with a laboratory for understanding
turbulence in a layer where the fundamental processes of transport
vary rapidly and a strongly superadiabatic region lies very closely
to a subadiabatic layer. Our tools for probing the turbulence are
high-resolution spectropolarimetric observations such as have recently
been obtained with the two balloon-borne SUNRISE missions, and numerical
simulations. Our aim is to study photospheric turbulence with the
help of Fourier power spectra that we compute from observations
and simulations. We also attempt to explain some properties of the
photospheric overshooting flow with the help of its governing equations
and simulations. We find that quiet-Sun observations and smeared
simulations are consistent with each other and exhibit a power-law
behavior in the subgranular range of their Doppler velocity power
spectra with a power-law index of ≈ - 2. The unsmeared simulations
exhibit a power law that extends over the full range between the
integral and Taylor scales with a power-law index of ≈ - 2.25. The
smearing, reminiscent of observational conditions, considerably reduces
the extent of the power-law-like portion of the power spectra. This
suggests that the limited spatial resolution in some observations
might eventually result in larger uncertainties in the estimation of
the power-law indices. The simulated vertical velocity power spectra
as a function of height show a rapid change in the power-law index
(at the subgranular range) from roughly the optical depth unity layer,
that is, the solar surface, to 300 km above it. We propose that the
cause of the steepening of the power-law index is the transition from
a super- to a subadiabatic region, in which the dominant source of
motions is overshooting convection. A scale-dependent transport of
the vertical momentum occurs. At smaller scales, the vertical momentum
is more efficiently transported sideways than at larger scales. This
results in less vertical velocity power transported upward at small
scales than at larger scales and produces a progressively steeper
vertical velocity power law below 180 km. Above this height, the
gravity work progressively gains importance at all relevant scales,
making the atmosphere progressively more hydrostatic and resulting
in a gradually less steep power law. Radiative heating and cooling of
the plasma is shown to play a dominant role in the plasma energetics
in this region, which is important in terms of nonadiabatic damping
of the convective motions.
Title: The SUNRISE UV Spectropolarimeter and imager for SUNRISE III
Authors: Feller, Alex; Gandorfer, Achim; Iglesias, Francisco A.;
Lagg, Andreas; Riethmüller, Tino L.; Solanki, Sami K.; Katsukawa,
Yukio; Kubo, Masahito
Bibcode: 2020SPIE11447E..AKF
Altcode:
Sunrise is a balloon-borne solar observatory dedicated to the
investigation of key processes of the magnetic field and the plasma
flows in the lower solar atmosphere. The observatory operates in
the stratosphere at an altitude of around 37 km in order to avoid
image degradation due to turbulence in the Earth's atmosphere and to
access the UV range. The third science flight of Sunrise will carry new
instrumentation which samples the solar spectrum over a broad wavelength
domain from the UV to the near IR and covers an extended height range in
the solar atmosphere. A key feature of the Sunrise UV Spectropolarimeter
and Imager (SUSI) operating between 309 nm and 417 nm, is its capability
to simultaneously record a large number of spectral lines. By combining
the spectral and polarization information of many individual lines
with different formation heights and sensitivities, the accuracy and
the height resolution of the inferred atmospheric parameters can be
significantly increased. The spectral bands of SUSI are selected one
at a time by rotating a diffraction grating with respect to a fixed
polarimetry unit. The spatial and spectral field of view on the 2k x
2k cameras is 59" and 2.0 - 2.3 nm, respectively. A further innovation
is the numerical restoration of the spectrograph scans by means of
synchronized 2D context imaging, a technique that has recently produced
impressive results at ground-based solar observatories.
Title: Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP)
for sunrise III: system design and capability
Authors: Katsukawa, Y.; del Toro Iniesta, J. C.; Solanki, S. K.;
Kubo, M.; Hara, H.; Shimizu, T.; Oba, T.; Kawabata, Y.; Tsuzuki,
T.; Uraguchi, F.; Nodomi, Y.; Shinoda, K.; Tamura, T.; Suematsu,
Y.; Ishikawa, R.; Kano, R.; Matsumoto, T.; Ichimoto, K.; Nagata, S.;
Quintero Noda, C.; Anan, T.; Orozco Suárez, D.; Balaguer Jiménez,
M.; López Jiménez, A. C.; Cobos Carrascosa, J. P.; Feller, A.;
Riethmueller, T.; Gandorfer, A.; Lagg, A.
Bibcode: 2020SPIE11447E..0YK
Altcode:
The Sunrise balloon-borne solar observatory carries a 1 m aperture
optical telescope and provides us a unique platform to conduct
continuous seeing-free observations at UV-visible-IR wavelengths from
an altitude of higher than 35 km. For the next flight planned for
2022, the post-focus instrumentation is upgraded with new spectro-
polarimeters for the near UV (SUSI) and the near-IR (SCIP), whereas
the imaging spectro-polarimeter Tunable Magnetograph (TuMag) is capable
of observing multiple spectral lines within the visible wavelength. A
new spectro-polarimeter called the Sunrise Chromospheric Infrared
spectroPolarimeter (SCIP) is under development for observing near-IR
wavelength ranges of around 770 nm and 850 nm. These wavelength ranges
contain many spectral lines sensitive to solar magnetic fields and
SCIP will be able to obtain magnetic and velocity structures in the
solar atmosphere with a sufficient height resolution by combining
spectro-polarimetric data of these lines. Polarimetric measurements are
conducted using a rotating waveplate as a modulator and polarizing beam
splitters in front of the cameras. The spatial and spectral resolutions
are 0.2" and 2 105, respectively, and a polarimetric sensitivity of
0.03 % (1σ) is achieved within a 10 s integration time. To detect
minute polarization signals with good precision, we carefully designed
the opto-mechanical system, polarization optics and modulation, and
onboard data processing.
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.
Bibcode: 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: Autonomous on-board data processing and instrument calibration
software for the Polarimetric and Helioseismic Imager on-board the
Solar Orbiter mission
Authors: Albert, Kinga; Hirzberger, Johann; Kolleck, Martin; Jorge,
Nestor Albelo; Busse, Dennis; Rodríguez, Julian Blanco; Carrascosa,
Juan Pedro Cobos; Fiethe, Björn; Gandorfer, Achim; Germerott, Dietmar;
Guan, Yejun; Guerrero, Lucas; Gutierrez-Marques, Pablo; Expósito,
David Hernández; Lange, Tobias; Michalik, Harald; Suárez, David
Orozco; Schou, Jesper; Solanki, Sami K.; del Toro Iniesta, José
Carlos; Woch, Joachim
Bibcode: 2020JATIS...6d8004A
Altcode:
A frequent problem arising for deep space missions is the discrepancy
between the amount of data desired to be transmitted to the ground
and the available telemetry bandwidth. A part of these data consists
of scientific observations, being complemented by calibration data
to help remove instrumental effects. We present our solution for this
discrepancy, implemented for the Polarimetric and Helioseismic Imager
on-board the Solar Orbiter mission, the first solar spectropolarimeter
in deep space. We implemented an on-board data reduction system that
processes calibration data, applies them to the raw science observables,
and derives science-ready physical parameters. This process reduces
the raw data for a single measurement from 24 images to five, thus
reducing the amount of downlinked data, and in addition, renders the
transmission of the calibration data unnecessary. Both these on-board
actions are completed autonomously.
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.
Bibcode: 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: PMI: The Photospheric Magnetic Field Imager
Authors: Staub, Jan; Fernandez-Rico, German; Gandorfer, Achim; Gizon,
Laurent; Hirzberger, Johann; Kraft, Stefan; Lagg, Andreas; Schou,
Jesper; Solanki, Sami K.; del Toro Iniesta, Jose Carlos; Wiegelmann,
Thomas; Woch, Joachim
Bibcode: 2020JSWSC..10...54S
Altcode:
We describe the design and the capabilities of the Photospheric Magnetic
field Imager (PMI), a compact and lightweight vector magnetograph,
which is being developed for ESA's Lagrange mission to the Lagrange
L5 point. After listing the design requirements and give a scientific
justification for them, we describe the technical implementation and
the design solution capable of fulfilling these requirements. This is
followed by a description of the hardware architecture as well as the
operations principle. An outlook on the expected performance concludes
the paper.
Title: The SO/PHI instrument on Solar Orbiter and its data products
Authors: Solanki, Sami K.; Hirzberger, Johann; Wiegelmann, Thomas;
Gandorfer, Achim; Woch, Joachim; del Toro Iniesta, José Carlos
Bibcode: 2020EGUGA..2217904S
Altcode:
A central instrument of Solar Orbiter is the Polarimetric and
Helioseismic Imager, SO/PHI. It is a vector magnetograph that also
provides data for helioseismology. SO/PHI is composed of two telescopes,
a full-disk telescope (FDT) and a high-resolution telescope (HRT). The
HRT will observe at a resolution as high as 200 km on the solar
surface, while the FDT will obtain the magnetic field and velocity of
the full solar disc whenever it observes. SO/PHI will be the first
solar spectro-polarimeter to leave the Sun-Earth line, opening up
some unique perspectives, such as the first detailed view of the solar
poles. This will allow not just a more precise and exact mapping of the
polar magnetic field than possible so far, but will also enable us to
follow the dynamics of individual magnetic features at high latitudes
and to determine solar surface and sub-surface flows right up to the
poles. In addition to its standard data products (vector magnetograms,
continuum images and maps of the line-of-sight velocity), SO/PHI will
also provide higher-level data products. These will include synoptic
charts, local magnetic field extrapolations starting from HRT data and
global magnetic field extrapolations (from FDT data) with potential
field source-surface (PFSS) models and possibly also non-potential
models such as NLFFF (non-linear force-free fields), magnetostatics
and MHD. The SO/PHI data products will usefully complement the data
taken by other instruments on Solar Orbiter and on Solar Probe, as
well as instruments on the ground or in Earth orbit. Combining with
observations by Earth-based and near-Earth telescopes will enable
new types of investigations, such as stereoscopic polarimetry and
stereoscopic helioseismology.
Title: Performance Analysis of the SO/PHI Software Framework for
On-board Data Reduction
Authors: Albert, K.; Hirzberger, J.; Busse, D.; Rodríguez, J. Blanco;
Castellanos Duran, J. S.; Cobos Carrascosa, J. P.; Fiethe, B.;
Gandorfer, A.; Guan, Y.; Kolleck, M.; Lagg, A.; Lange, T.; Michalik,
H.; Solanki, S. K.; del Toro Iniesta, J. C.
Bibcode: 2019ASPC..523..151A
Altcode: 2019arXiv190508690A
The Polarimetric and Helioseismic Imager (PHI) is the first deep-space
solar spectropolarimeter, on-board the Solar Orbiter (SO) space
mission. It faces: stringent requirements on science data accuracy, a
dynamic environment, and severe limitations on telemetry volume. SO/PHI
overcomes these restrictions through on-board instrument calibration
and science data reduction, using dedicated firmware in FPGAs. This
contribution analyses the accuracy of a data processing pipeline by
comparing the results obtained with SO/PHI hardware to a reference
from a ground computer. The results show that for the analyzed pipeline
the error introduced by the firmware implementation is well below the
requirements of SO/PHI.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for the SUNRISE balloon-borne solar observatory
Authors: Suematsu, Yoshinori; Katsukawa, Yukio; Hara, Hirohisa;
Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito; Barthol,
Peter; Riethmueller, Tino; Gandorfer, Achim; Feller, Alex; Orozco
Suárez, David; Del Toro Iniesta, Jose Carlos; Kano, Ryouhei; Ishikawa,
Shin-nosuke; Ishikawa, Ryohko; Tsuzuki, Toshihiro; Uraguchi, Fumihiro;
Quintero Noda, Carlos; Tamura, Tomonori; Oba, Takayoshi; Kawabata,
Yusuke; Nagata, Shinichi; Anan, Tetsu; Cobos Carrascosa, Juan Pedro;
Lopez Jimenez, Antonio Carlos; Balaguer Jimenez, Maria; Solanki, Sami
Bibcode: 2018cosp...42E3285S
Altcode:
The SUNRISE balloon-borne solar observatory carries a 1 m aperture
optical telescope, and allows us to perform seeing-free continuous
observations at visible-IR wavelengths from an altitude higher than
35 km. In the past two flights, in 2009 and 2013, observations mainly
focused on fine structures of photospheric magnetic fields. For the
third flight planned for 2021, we are developing a new instrument
for conducting spectro-polarimetry of spectral lines formed over a
larger height range in the solar atmosphere from the photosphere to
the chromosphere. Targets of the spectro-polarimetric observation
are (1) to determine 3D magnetic structure from the photosphere to
the chromosphere, (2) to trace MHD waves from the photosphere to the
chromosphere, and (3) to reveal the mechanism driving chromospheric
jets, by measuring height- and time-dependent velocities and magnetic
fields. To achieve these goals, a spectro-polarimeter called SCIP
(Sunrise Chromospheric Infrared spectroPolarimeter) is designed to
observe near-infrared spectrum lines sensitive to solar magnetic
fields. The spatial and spectral resolutions are 0.2 arcsec and
200,000, respectively, while 0.03% polarimetric sensitivity is
achieved within a 10 sec integration time. The optical system employs
an Echelle grating and off-axis aspheric mirrors to observe the two
wavelength ranges centered at 850 nm and 770 nm simultaneously by
two cameras. Polarimetric measurements are performed using a rotating
waveplate and polarization beam-splitters in front of the cameras. For
detecting minute polarization signals with good precision, we carefully
assess the temperature dependence of polarization optics, and make
the opto-structural design that minimizes the thermal deformation
of the spectrograph optics. Another key technique is to attain good
(better than 30 msec) synchronization among the rotating phase of
the waveplate, read-out timing of cameras, and step timing of a
slit-scanning mirror. On-board accumulation and data processing are
also critical because we cannot store all the raw data read-out from the
cameras. We demonstrate that we can reduce the data down to almost 10%
with loss-less image compression and without sacrificing polarimetric
information in the data. The SCIP instrument is developed by internal
collaboration among Japanese institutes including Japan Aerospace
Exploration Agency (JAXA), the Spanish Sunrise consortium, and the
German Max Planck Institute for Solar System Research (MPS) with a
leadership of the National Astronomical Observatory of Japan (NAOJ).
Title: Getting Ready for the Third Science Flight of SUNRISE
Authors: Barthol, Peter; Katsukawa, Yukio; Lagg, Andreas; Solanki,
Sami K.; Kubo, Masahito; Riethmueller, Tino; Martínez Pillet,
Valentin; Gandorfer, Achim; Feller, Alex; Berkefeld, . Thomas; Orozco
Suárez, David; Del Toro Iniesta, Jose Carlos; Bernasconi, Pietro;
Álvarez-Herrero, Alberto; Quintero Noda, Carlos
Bibcode: 2018cosp...42E.215B
Altcode:
SUNRISE is a balloon-borne, stratospheric solar observatory dedicated
to the investigation of the structure and dynamics of the Sun's
magnetic field and its interaction with convective plasma flows and
waves. The previous science flights of SUNRISE in 2009 and 2013 have
led to many new scientific results, so far described in around 90
refereed publications. This success has shown the huge potential of the
SUNRISE concept and the recovery of the largely intact payload offers
the opportunity for a third flight.The scientific instrumentation of
SUNRISE 3 will have extended capabilities in particular to measure
magnetic fields, plasma velocities and temperatures with increased
sensitivity and over a larger height range in the solar atmosphere, from
the convectively dominated photosphere up to the still poorly understood
chromosphere. The latter is the key interaction region between magnetic
field, waves and radiation and plays a central role in transporting
energy to the outer layers of the solar atmosphere including the
corona.SUNRISE 3 will carry 2 new grating-based spectro-polarimeters
with slit-scanning and context imaging with slitjaw cameras. The
SUNRISE UV Spectro-polarimeter and Imager (SUSI) will explore the rich
near-UV range between 300 nm and 430 nm which is poorly accessible
from the ground. The SUNRISE Chromospheric Infrared spectro-Polarimeter
(SCIP) will sample 2 spectral windows in the near-infrared, containing
many spectral lines highly sensitive to magnetic fields at different
formation heights. In addition to the two new instruments the Imaging
Magnetograph eXperiment (IMaX), an etalon-based tunable filtergraph and
spectro-polarimeter flown on both previous missions, will be upgraded
to IMaX+, enhancing its cadence and giving access to 2 spectral lines
in the visible spectral range. All three instruments will allow
investigating both the photosphere and the chromosphere and will
ideally complement each other in terms of sensitivity, height coverage
and resolution.A new gondola with a sophisticated attitude control
system including roll damping will provide improved pointing/tracking
performance. Upgraded image stabilization with higher bandwidth will
further reduce residual jitter, maximizing the quality of the science
data.SUNRISE 3 is a joint project of the German Max-Planck-Institut für
Sonnensystemforschung together with the Spanish SUNRISE consortium, the
Johns Hopkins University Applied Physics Laboratory, USA, the German
Kiepenheuer Institut für Sonnenphysik, the National Astronomical
Observatory of Japan and the Japan Aerospace eXploraion Agency (JAXA).
Title: Autonomous on-board data processing and instrument calibration
software for the SO/PHI
Authors: Albert, K.; Hirzberger, J.; Busse, D.; Lange, T.; Kolleck, M.;
Fiethe, B.; Orozco Suárez, D.; Woch, J.; Schou, J.; Blanco Rodriguez,
J.; Gandorfer, A.; Guan, Y.; Cobos Carrascosa, J. P.; Hernández
Expósito, D.; del Toro Iniesta, J. C.; Solanki, S. K.; Michalik, H.
Bibcode: 2018SPIE10707E..0OA
Altcode: 2018arXiv181003493A
The extension of on-board data processing capabilities is an
attractive option to reduce telemetry for scientific instruments
on deep space missions. The challenges that this presents, however,
require a comprehensive software system, which operates on the limited
resources a data processing unit in space allows. We implemented such
a system for the Polarimetric and Helioseismic Imager (PHI) on-board
the Solar Orbiter (SO) spacecraft. It ensures autonomous operation
to handle long command-response times, easy changing of the processes
after new lessons have been learned and meticulous book-keeping of all
operations to ensure scientific accuracy. This contribution presents
the requirements and main aspects of the software implementation,
followed by an example of a task implemented in the software frame,
and results from running it on SO/PHI. The presented example shows
that the different parts of the software framework work well together,
and that the system processes data as we expect. The flexibility of
the framework makes it possible to use it as a baseline for future
applications with similar needs and limitations as SO/PHI.
Title: The High Resolution Telescope (HRT) of the Polarimetric and
Helioseismic Imager (PHI) onboard Solar Orbiter
Authors: Gandorfer, A.; Grauf, B.; Staub, J.; Bischoff, J.; Woch, J.;
Hirzberger, J.; Solanki, S. K.; Álvarez-Herrero, A.; García Parejo,
P.; Schmidt, W.; Volkmer, R.; Appourchaux, T.; del Toro Iniesta, J. C.
Bibcode: 2018SPIE10698E..4NG
Altcode:
Solar Orbiter is a joint mission of ESA and NASA scheduled for
launch in 2020. Solar Orbiter is a complete and unique heliophysics
mission, combining remote sensing and in-situ analysis; its special
elliptical orbit allows viewing the Sun from a distance of only 0.28
AU, and - leaving the ecliptic plane - to observe the solar poles from
a hitherto unexplored vantage point. One of the key instruments for
Solar Orbiter's science is the "Polarimetric and Helioseismic Imager"
(PHI), which will provide maps of the solar surface magnetic fields and
the gas flows on the visible solar surface. Two telescopes, a full disc
imager, and a high resolution channel feed a common Fabry-Perot based
tunable filter and thus allow sampling a single Fraunhofer line at 617.3
nm with high spectral resolution; a polarization modulation system
makes the system sensitive to the full state of polarization. From
the analysis of the Doppler shift and the magnetically induced Zeeman
polarization in this line, the magnetic field and the line-of-sight
gas motions can be detected for each point in the image. In this
paper we describe the opto-mechanical system design of the high
resolution telescope. It is based on a decentred Ritchey-Chrétien
two-mirror telescope. The telescope includes a Barlow type magnifier
lens group, which is used as in-orbit focus compensator, and a beam
splitter, which sends a small fraction of the collected light onto
a fast camera, which provides the error signals for the actively
controlled secondary mirror compensating for spacecraft jitter and other
disturbances. The elliptical orbit of the spacecraft poses high demands
on the thermo-mechanical stability. The varying size of the solar disk
image requires a special false-light suppression architecture, which is
briefly described. In combination with a heat-rejecting entrance window,
the optical energy impinging on the polarimetric and spectral analysis
system is efficiently reduced. We show how the design can preserve the
diffraction-limited imaging performance over the design temperature
range of -20°C to +60°C. The decentred hyperbolical mirrors require
special measures for the inter-alignment and their alignment with
respect to the mechanical structure. A system of alignment flats and
mechanical references is used for this purpose. We will describe the
steps of the alignment procedure, and the dedicated optical ground
support equipment, which are needed to reach the diffraction limited
performance of the telescope. We will also report on the verification
of the telescope performance, both - in ambient condition - and in
vacuum at different temperatures.
Title: Prospects of Solar Magnetometry—From Ground and in Space
Authors: Kleint, Lucia; Gandorfer, Achim
Bibcode: 2018smf..book..397K
Altcode:
No abstract at ADS
Title: The Maximum Entropy Limit of Small-scale Magnetic Field
Fluctuations in the Quiet Sun
Authors: Gorobets, A. Y.; Berdyugina, S. V.; Riethmüller, T. L.;
Blanco Rodríguez, J.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Gizon, L.; Hirzberger, J.; van Noort, M.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..233....5G
Altcode: 2017arXiv171008361G
The observed magnetic field on the solar surface is characterized by a
very complex spatial and temporal behavior. Although feature-tracking
algorithms have allowed us to deepen our understanding of this behavior,
subjectivity plays an important role in the identification and tracking
of such features. In this paper, we continue studies of the temporal
stochasticity of the magnetic field on the solar surface without relying
either on the concept of magnetic features or on subjective assumptions
about their identification and interaction. We propose a data analysis
method to quantify fluctuations of the line-of-sight magnetic field by
means of reducing the temporal field’s evolution to the regular Markov
process. We build a representative model of fluctuations converging to
the unique stationary (equilibrium) distribution in the long time limit
with maximum entropy. We obtained different rates of convergence to the
equilibrium at fixed noise cutoff for two sets of data. This indicates
a strong influence of the data spatial resolution and mixing-polarity
fluctuations on the relaxation process. The analysis is applied to
observations of magnetic fields of the relatively quiet areas around an
active region carried out during the second flight of the Sunrise/IMaX
and quiet Sun areas at the disk center from the Helioseismic and
Magnetic Imager on board the Solar Dynamics Observatory satellite.
Title: Prospects of Solar Magnetometry—From Ground and in Space
Authors: Kleint, Lucia; Gandorfer, Achim
Bibcode: 2017SSRv..210..397K
Altcode: 2015SSRv..tmp..114K; 2015arXiv151003763K
In this review we present an overview of observing facilities for solar
research, which are planned or will come to operation in near future. We
concentrate on facilities, which harbor specific potential for solar
magnetometry. We describe the challenges and science goals of future
magnetic measurements, the status of magnetic field measurements at
different major solar observatories, and provide an outlook on possible
upgrades of future instrumentation.
Title: The Solar Ultraviolet Imaging Telescope on-board Aditya-L1
Authors: Tripathi, Durgesh; Ramaprakash, A. N.; Khan, Aafaque;
Ghosh, Avyarthana; Chatterjee, Subhamoy; Banerjee, Dipankar; Chordia,
Pravin; Gandorfer, Achim; Krivova, Natalie; Nandy, Dibyendu; Rajarshi,
Chaitanya; Solanki, Sami K.
Bibcode: 2017CSci..113..616T
Altcode: 2022arXiv220407732T
The Solar Ultraviolet Imaging Telescope (SUIT) is an instrument
onboard the Aditya-L1 mission of ISRO that will measure and monitor
the solar radiation emitted in the near-ultraviolet wavelength range
(200-400 nm). SUIT will simultaneously map the photosphere and the
chromosphere of the Sun using 11 filters sensitive to different
wavelengths and covering different heights in the solar atmosphere
and help us understand the processes involved in the transfer of
mass and energy from one layer to the other. SUIT will also allow us
to measure and monitor spatially resolved solar spectral irradiance
that governs the chemistry of oxygen and ozone in the stratosphere of
Earth's atmosphere. This is central to our understanding of the Sun
climate relationship.
Title: Erratum: Morphological Properties of
Slender CaII H Fibrils Observed by sunrise II (ApJS 229, 1, 6)
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..230...11G
Altcode:
No abstract at ADS
Title: Slender Ca II H Fibrils Mapping Magnetic Fields in the Low
Solar Chromosphere
Authors: Jafarzadeh, S.; Rutten, R. J.; Solanki, S. K.; Wiegelmann, T.;
Riethmüller, T. L.; van Noort, M.; Szydlarski, M.; Blanco Rodríguez,
J.; Barthol, P.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.;
Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Schmidt, W.
Bibcode: 2017ApJS..229...11J
Altcode: 2016arXiv161003104J
A dense forest of slender bright fibrils near a small solar active
region is seen in high-quality narrowband Ca II H images from the SuFI
instrument onboard the Sunrise balloon-borne solar observatory. The
orientation of these slender Ca II H fibrils (SCF) overlaps with the
magnetic field configuration in the low solar chromosphere derived
by magnetostatic extrapolation of the photospheric field observed
with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are
qualitatively aligned with small-scale loops computed from a novel
inversion approach based on best-fit numerical MHD simulation. Such
loops are organized in canopy-like arches over quiet areas that differ
in height depending on the field strength near their roots.
Title: Magneto-static Modeling from Sunrise/IMaX: Application to an
Active Region Observed with Sunrise II
Authors: Wiegelmann, T.; Neukirch, T.; Nickeler, D. H.; Solanki, S. K.;
Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller,
T. L.; van Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...18W
Altcode: 2017arXiv170101458N; 2017arXiv170101458W
Magneto-static models may overcome some of the issues facing force-free
magnetic field extrapolations. So far they have seen limited use
and have faced problems when applied to quiet-Sun data. Here we
present a first application to an active region. We use solar vector
magnetic field measurements gathered by the IMaX polarimeter during
the flight of the Sunrise balloon-borne solar observatory in 2013
June as boundary conditions for a magneto-static model of the higher
solar atmosphere above an active region. The IMaX data are embedded
in active region vector magnetograms observed with SDO/HMI. This work
continues our magneto-static extrapolation approach, which was applied
earlier to a quiet-Sun region observed with Sunrise I. In an active
region the signal-to-noise-ratio in the measured Stokes parameters
is considerably higher than in the quiet-Sun and consequently the
IMaX measurements of the horizontal photospheric magnetic field allow
us to specify the free parameters of the model in a special class of
linear magneto-static equilibria. The high spatial resolution of IMaX
(110-130 km, pixel size 40 km) enables us to model the non-force-free
layer between the photosphere and the mid-chromosphere vertically
by about 50 grid points. In our approach we can incorporate some
aspects of the mixed beta layer of photosphere and chromosphere, e.g.,
taking a finite Lorentz force into account, which was not possible with
lower-resolution photospheric measurements in the past. The linear model
does not, however, permit us to model intrinsic nonlinear structures
like strongly localized electric currents.
Title: The Second Flight of the Sunrise Balloon-borne Solar
Observatory: Overview of Instrument Updates, the Flight, the Data,
and First Results
Authors: Solanki, S. K.; Riethmüller, T. L.; Barthol, P.; Danilovic,
S.; Deutsch, W.; Doerr, H. -P.; Feller, A.; Gandorfer, A.; Germerott,
D.; Gizon, L.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.;
Lagg, A.; Meller, R.; Tomasch, G.; van Noort, M.; Blanco Rodríguez,
J.; Gasent Blesa, J. L.; Balaguer Jiménez, M.; Del Toro Iniesta,
J. C.; López Jiménez, A. C.; Orozco Suarez, D.; Berkefeld, T.;
Halbgewachs, C.; Schmidt, W.; Álvarez-Herrero, A.; Sabau-Graziati,
L.; Pérez Grande, I.; Martínez Pillet, V.; Card, G.; Centeno, R.;
Knölker, M.; Lecinski, A.
Bibcode: 2017ApJS..229....2S
Altcode: 2017arXiv170101555S
The Sunrise balloon-borne solar observatory, consisting of a 1 m
aperture telescope that provides a stabilized image to a UV filter
imager and an imaging vector polarimeter, carried out its second science
flight in 2013 June. It provided observations of parts of active regions
at high spatial resolution, including the first high-resolution images
in the Mg II k line. The obtained data are of very high quality, with
the best UV images reaching the diffraction limit of the telescope
at 3000 Å after Multi-Frame Blind Deconvolution reconstruction
accounting for phase-diversity information. Here a brief update is
given of the instruments and the data reduction techniques, which
includes an inversion of the polarimetric data. Mainly those aspects
that evolved compared with the first flight are described. A tabular
overview of the observations is given. In addition, an example time
series of a part of the emerging active region NOAA AR 11768 observed
relatively close to disk center is described and discussed in some
detail. The observations cover the pores in the trailing polarity of
the active region, as well as the polarity inversion line where flux
emergence was ongoing and a small flare-like brightening occurred in
the course of the time series. The pores are found to contain magnetic
field strengths ranging up to 2500 G, and while large pores are clearly
darker and cooler than the quiet Sun in all layers of the photosphere,
the temperature and brightness of small pores approach or even exceed
those of the quiet Sun in the upper photosphere.
Title: A Tale of Two Emergences: Sunrise II Observations of Emergence
Sites in a Solar Active Region
Authors: Centeno, R.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.;
Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger,
J.; Riethmüller, T. L.; van Noort, M.; Orozco Suárez, D.; Berkefeld,
T.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....3C
Altcode: 2016arXiv161003531C
In 2013 June, the two scientific instruments on board the second Sunrise
mission witnessed, in detail, a small-scale magnetic flux emergence
event as part of the birth of an active region. The Imaging Magnetograph
Experiment (IMaX) recorded two small (∼ 5\prime\prime )
emerging flux patches in the polarized filtergrams of a photospheric Fe
I spectral line. Meanwhile, the Sunrise Filter Imager (SuFI) captured
the highly dynamic chromospheric response to the magnetic fields pushing
their way through the lower solar atmosphere. The serendipitous capture
of this event offers a closer look at the inner workings of active
region emergence sites. In particular, it reveals in meticulous detail
how the rising magnetic fields interact with the granulation as they
push through the Sun’s surface, dragging photospheric plasma in
their upward travel. The plasma that is burdening the rising field
slides along the field lines, creating fast downflowing channels at
the footpoints. The weight of this material anchors this field to the
surface at semi-regular spatial intervals, shaping it in an undulatory
fashion. Finally, magnetic reconnection enables the field to release
itself from its photospheric anchors, allowing it to continue its
voyage up to higher layers. This process releases energy that lights
up the arch-filament systems and heats the surrounding chromosphere.
Title: Photospheric Response to an Ellerman Bomb-like Event—An
Analogy of Sunrise/IMaX Observations and MHD Simulations
Authors: Danilovic, S.; Solanki, S. K.; Barthol, P.; Gandorfer,
A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van Noort, M.;
Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez, D.;
Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....5D
Altcode: 2016arXiv160903817D
Ellerman Bombs are signatures of magnetic reconnection, which is an
important physical process in the solar atmosphere. How and where they
occur is a subject of debate. In this paper, we analyze Sunrise/IMaX
data, along with 3D MHD simulations that aim to reproduce the exact
scenario proposed for the formation of these features. Although
the observed event seems to be more dynamic and violent than the
simulated one, simulations clearly confirm the basic scenario for the
production of EBs. The simulations also reveal the full complexity of
the underlying process. The simulated observations show that the Fe I
525.02 nm line gives no information on the height where reconnection
takes place. It can only give clues about the heating in the aftermath
of the reconnection. However, the information on the magnetic field
vector and velocity at this spatial resolution is extremely valuable
because it shows what numerical models miss and how they can be
improved.
Title: Transverse Oscillations in Slender Ca II H Fibrils Observed
with Sunrise/SuFI
Authors: Jafarzadeh, S.; Solanki, S. K.; Gafeira, R.; van Noort, M.;
Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer,
A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.;
Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....9J
Altcode: 2016arXiv161007449J
We present observations of transverse oscillations in slender Ca II
H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long
time series of high- (spatial and temporal-) resolution seeing-free
observations in a 1.1 Å wide passband covering the line core of Ca
II H 3969 Å from the second flight of the Sunrise balloon-borne solar
observatory. The entire field of view, spanning the polarity inversion
line of an active region close to the solar disk center, is covered with
bright, thin, and very dynamic fine structures. Our analysis reveals
the prevalence of transverse waves in SCFs with median amplitudes and
periods on the order of 2.4 ± 0.8 km s-1 and 83 ± 29 s,
respectively (with standard deviations given as uncertainties). We
find that the transverse waves often propagate along (parts of) the
SCFs with median phase speeds of 9 ± 14 km s-1. While the
propagation is only in one direction along the axis in some of the
SCFs, propagating waves in both directions, as well as standing waves
are also observed. The transverse oscillations are likely Alfvénic
and are thought to be representative of magnetohydrodynamic kink
waves. The wave propagation suggests that the rapid high-frequency
transverse waves, often produced in the lower photosphere, can
penetrate into the chromosphere with an estimated energy flux of ≈15
kW m-2. Characteristics of these waves differ from those
reported for other fibrillar structures, which, however, were observed
mainly in the upper solar chromosphere.
Title: Kinematics of Magnetic Bright Features in the Solar Photosphere
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Barthol, P.;
Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon,
L.; Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Riethmüller, T. L.; Schmidt, W.; van Noort, M.
Bibcode: 2017ApJS..229....8J
Altcode: 2016arXiv161007634J
Convective flows are known as the prime means of transporting magnetic
fields on the solar surface. Thus, small magnetic structures are good
tracers of turbulent flows. We study the migration and dispersal
of magnetic bright features (MBFs) in intergranular areas observed
at high spatial resolution with Sunrise/IMaX. We describe the flux
dispersal of individual MBFs as a diffusion process whose parameters are
computed for various areas in the quiet-Sun and the vicinity of active
regions from seeing-free data. We find that magnetic concentrations
are best described as random walkers close to network areas (diffusion
index, γ =1.0), travelers with constant speeds over a supergranule
(γ =1.9{--}2.0), and decelerating movers in the vicinity of flux
emergence and/or within active regions (γ =1.4{--}1.5). The three
types of regions host MBFs with mean diffusion coefficients of 130
km2 s-1, 80-90 km2 s-1,
and 25-70 km2 s-1, respectively. The MBFs in
these three types of regions are found to display a distinct kinematic
behavior at a confidence level in excess of 95%.
Title: Spectropolarimetric Evidence for a Siphon Flow along an
Emerging Magnetic Flux Tube
Authors: Requerey, Iker S.; Ruiz Cobo, B.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Blanco Rodríguez, J.; Solanki, S. K.; Barthol,
P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.;
van Noort, M.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...15R
Altcode: 2016arXiv161106732R
We study the dynamics and topology of an emerging magnetic flux
concentration using high spatial resolution spectropolarimetric data
acquired with the Imaging Magnetograph eXperiment on board the sunrise
balloon-borne solar observatory. We obtain the full vector magnetic
field and the line of sight (LOS) velocity through inversions of
the Fe I line at 525.02 nm with the SPINOR code. The derived vector
magnetic field is used to trace magnetic field lines. Two magnetic flux
concentrations with different polarities and LOS velocities are found
to be connected by a group of arch-shaped magnetic field lines. The
positive polarity footpoint is weaker (1100 G) and displays an upflow,
while the negative polarity footpoint is stronger (2200 G) and shows
a downflow. This configuration is naturally interpreted as a siphon
flow along an arched magnetic flux tube.
Title: Morphological Properties of Slender Ca II H Fibrils Observed
by SUNRISE II
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....6G
Altcode: 2016arXiv161200319G
We use seeing-free high spatial resolution Ca II H data obtained by
the SUNRISE observatory to determine properties of slender fibrils
in the lower solar chromosphere. In this work we use intensity images
taken with the SuFI instrument in the Ca II H line during the second
scientific flight of the SUNRISE observatory to identify and track
elongated bright structures. After identification, we analyze theses
structures to extract their morphological properties. We identify
598 slender Ca II H fibrils (SCFs) with an average width of around
180 km, length between 500 and 4000 km, average lifetime of ≈400
s, and average curvature of 0.002 arcsec-1. The maximum
lifetime of the SCFs within our time series of 57 minutes is ≈2000
s. We discuss similarities and differences of the SCFs with other
small-scale, chromospheric structures such as spicules of type I and
II, or Ca II K fibrils.
Title: A New MHD-assisted Stokes Inversion Technique
Authors: Riethmüller, T. L.; Solanki, S. K.; Barthol, P.; Gandorfer,
A.; Gizon, L.; Hirzberger, J.; van Noort, M.; Blanco Rodríguez, J.;
Del Toro Iniesta, J. C.; Orozco Suárez, D.; Schmidt, W.; Martínez
Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...16R
Altcode: 2016arXiv161105175R
We present a new method of Stokes inversion of spectropolarimetric
data and evaluate it by taking the example of a Sunrise/IMaX
observation. An archive of synthetic Stokes profiles is obtained
by the spectral synthesis of state-of-the-art magnetohydrodynamics
(MHD) simulations and a realistic degradation to the level of the
observed data. The definition of a merit function allows the archive
to be searched for the synthetic Stokes profiles that best match the
observed profiles. In contrast to traditional Stokes inversion codes,
which solve the Unno-Rachkovsky equations for the polarized radiative
transfer numerically and fit the Stokes profiles iteratively, the new
technique provides the full set of atmospheric parameters. This gives
us the ability to start an MHD simulation that takes the inversion
result as an initial condition. After a relaxation process of half an
hour solar time we obtain physically consistent MHD data sets with
a target similar to the observation. The new MHD simulation is used
to repeat the method in a second iteration, which further improves
the match between observation and simulation, resulting in a factor
of 2.2 lower mean {χ }2 value. One advantage of the new
technique is that it provides the physical parameters on a geometrical
height scale. It constitutes a first step toward inversions that give
results consistent with the MHD equations.
Title: Oscillations on Width and Intensity of Slender Ca II H Fibrils
from Sunrise/SuFI
Authors: Gafeira, R.; Jafarzadeh, S.; Solanki, S. K.; Lagg, A.;
van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....7G
Altcode: 2017arXiv170102801G
We report the detection of oscillations in slender Ca II H fibrils
(SCFs) from high-resolution observations acquired with the Sunrise
balloon-borne solar observatory. The SCFs show obvious oscillations in
their intensity, but also their width. The oscillatory behaviors are
investigated at several positions along the axes of the SCFs. A large
majority of fibrils show signs of oscillations in intensity. Their
periods and phase speeds are analyzed using a wavelet analysis. The
width and intensity perturbations have overlapping distributions
of the wave period. The obtained distributions have median values
of the period of 32 ± 17 s and 36 ± 25 s, respectively. We
find that the fluctuations of both parameters propagate in
the SCFs with speeds of {11}-11+49 km
s-1 and {15}-15+34 km s-1,
respectively. Furthermore, the width and intensity oscillations have a
strong tendency to be either in anti-phase or, to a smaller extent, in
phase. This suggests that the oscillations of both parameters are caused
by the same wave mode and that the waves are likely propagating. Taking
all the evidence together, the most likely wave mode to explain all
measurements and criteria is the fast sausage mode.
Title: Solar Coronal Loops Associated with Small-scale Mixed Polarity
Surface Magnetic Fields
Authors: Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.;
Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van
Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco
Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....4C
Altcode: 2016arXiv161007484C
How and where are coronal loops rooted in the solar lower
atmosphere? The details of the magnetic environment and its evolution
at the footpoints of coronal loops are crucial to understanding the
processes of mass and energy supply to the solar corona. To address
the above question, we use high-resolution line-of-sight magnetic
field data from the Imaging Magnetograph eXperiment instrument on the
Sunrise balloon-borne observatory and coronal observations from the
Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory
of an emerging active region. We find that the coronal loops are
often rooted at the locations with minor small-scale but persistent
opposite-polarity magnetic elements very close to the larger dominant
polarity. These opposite-polarity small-scale elements continually
interact with the dominant polarity underlying the coronal loop through
flux cancellation. At these locations we detect small inverse Y-shaped
jets in chromospheric Ca II H images obtained from the Sunrise Filter
Imager during the flux cancellation. Our results indicate that magnetic
flux cancellation and reconnection at the base of coronal loops due
to mixed polarity fields might be a crucial feature for the supply of
mass and energy into the corona.
Title: Moving Magnetic Features around a Pore
Authors: Kaithakkal, A. J.; Riethmüller, T. L.; Solanki, S. K.; Lagg,
A.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; vanNoort,
M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...13K
Altcode: 2016arXiv160905664K
Spectropolarimetric observations from Sunrise/IMaX, obtained in 2013
June, are used for a statistical analysis to determine the physical
properties of moving magnetic features (MMFs) observed near a pore. MMFs
of the same and opposite polarity, with respect to the pore, are found
to stream from its border at an average speed of 1.3 km s-1
and 1.2 km s-1, respectively, with mainly same-polarity MMFs
found further away from the pore. MMFs of both polarities are found to
harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs
are blueshifted, whereas same-polarity MMFs do not show any preference
for up- or downflows. Most of the MMFs are found to be of sub-arcsecond
size and carry a mean flux of ∼1.2 × 1017 Mx.
Title: Helioseismology with Solar Orbiter
Authors: Löptien, Björn; Birch, Aaron C.; Gizon, Laurent; Schou,
Jesper; Appourchaux, Thierry; Blanco Rodríguez, Julián; Cally,
Paul S.; Dominguez-Tagle, Carlos; Gandorfer, Achim; Hill, Frank;
Hirzberger, Johann; Scherrer, Philip H.; Solanki, Sami K.
Bibcode: 2017hdsi.book..257L
Altcode:
No abstract at ADS
Title: Far side Helioseismology with Solar Orbiter
Authors: Appourchaux, T.; Birch, A.; Gizon, L. C.; Löptien, B.;
Schou, J.; Solanki, S. K.; del Toro Iniesta, J. C.; Gandorfer, A.;
Hirzberger, J.; Alvarez-Herrero, A.; Woch, J. G.; Schmidt, W.
Bibcode: 2016AGUFMSH43A2554A
Altcode:
The Solar Orbiter mission, to be launched in October 2018, will
carry a suite of remote sensing and in-situ instruments, including
the Polarimetric and Helioseismic Imager (PHI). PHI will deliver
high-cadence images of the Sun in intensity and Doppler velocity
suitable for carrying out novel helioseismic studies. The orbit
of the Solar Orbiter spacecraft will reach a solar latitude up to
34 degrees by the end of the extended mission and thus will enable
the first local helioseismology studies of the polar regions. The
full range of Earth-Sun-spacecraft angles provided by the orbit will
enable helioseismology from two vantage points by combining PHI with
another instrument: stereoscopic helioseismology will allow the study
of the deep solar interior and a better understanding of the physics
of solar oscillations in both quiet Sun and sunspots. In this paper
we will review the helioseismic objectives achievable with PHI, and
will also give a short status report of the development of the Flight
Model of PHI.
Title: The Solar Ultraviolet Imaging Telescope onboard Aditya-L1
Authors: Ghosh, Avyarthana; Chatterjee, Subhamoy; Khan, Aafaque R.;
Tripathi, Durgesh; Ramaprakash, A. N.; Banerjee, Dipankar; Chordia,
Pravin; Gandorfer, Achim M.; Krivova, Natalie; Nandy, Dibyendu;
Rajarshi, Chaitanya; Solanki, Sami K.; Sriram, S.
Bibcode: 2016SPIE.9905E..03G
Altcode:
The Solar Ultraviolet Imaging Telescope (SUIT) is an instrument onboard
the Aditya-L1 spacecraft, the first dedicated solar mission of the
Indian Space Research Organization (ISRO), which will be put in a
halo orbit at the Sun-Earth Langrage point (L1). SUIT has an off-axis
Ritchey-Chrétien configuration with a combination of 11 narrow and
broad bandpass filters which will be used for full-disk solar imaging
in the Ultravoilet (UV) wavelength range 200-400 nm. It will provide
near simultaneous observations of lower and middle layers of the solar
atmosphere, namely the Photosphere and Chromosphere. These observations
will help to improve our understanding of coupling and dynamics of
various layers of the solar atmosphere, mechanisms responsible for
stability, dynamics and eruption of solar prominences and Coronal Mass
ejections, and possible causes of solar irradiance variability in the
Near and Middle UV regions, which is of central interest for assessing
the Sun's influence on climate.
Title: Helioseismology with Solar Orbiter
Authors: Löptien, Björn; Birch, Aaron C.; Gizon, Laurent; Schou,
Jesper; Appourchaux, Thierry; Blanco Rodríguez, Julián; Cally,
Paul S.; Dominguez-Tagle, Carlos; Gandorfer, Achim; Hill, Frank;
Hirzberger, Johann; Scherrer, Philip H.; Solanki, Sami K.
Bibcode: 2015SSRv..196..251L
Altcode: 2014arXiv1406.5435L; 2014SSRv..tmp...31L
The Solar Orbiter mission, to be launched in July 2017, will
carry a suite of remote sensing and in-situ instruments, including
the Polarimetric and Helioseismic Imager (PHI). PHI will deliver
high-cadence images of the Sun in intensity and Doppler velocity
suitable for carrying out novel helioseismic studies. The orbit of
the Solar Orbiter spacecraft will reach a solar latitude of up to
21∘ (up to 34∘ by the end of the extended
mission) and thus will enable the first local helioseismology studies of
the polar regions. Here we consider an array of science objectives to be
addressed by helioseismology within the baseline telemetry allocation
(51 Gbit per orbit, current baseline) and within the science observing
windows (baseline 3×10 days per orbit). A particularly important
objective is the measurement of large-scale flows at high latitudes
(rotation and meridional flow), which are largely unknown but play an
important role in flux transport dynamos. For both helioseismology
and feature tracking methods convection is a source of noise in
the measurement of longitudinally averaged large-scale flows, which
decreases as T -1/2 where T is the total duration of the
observations. Therefore, the detection of small amplitude signals (e.g.,
meridional circulation, flows in the deep solar interior) requires long
observation times. As an example, one hundred days of observations at
lower spatial resolution would provide a noise level of about three m/s
on the meridional flow at 80∘ latitude. Longer time-series
are also needed to study temporal variations with the solar cycle. The
full range of Earth-Sun-spacecraft angles provided by the orbit will
enable helioseismology from two vantage points by combining PHI with
another instrument: stereoscopic helioseismology will allow the study
of the deep solar interior and a better understanding of the physics
of solar oscillations in both quiet Sun and sunspots. We have used a
model of the PHI instrument to study its performance for helioseismology
applications. As input we used a 6 hr time-series of realistic solar
magneto-convection simulation (Stagger code) and the SPINOR radiative
transfer code to synthesize the observables. The simulated power
spectra of solar oscillations show that the instrument is suitable for
helioseismology. In particular, the specified point spread function,
image jitter, and photon noise are no obstacle to a successful mission.
Title: The Polarimetric and Helioseismic Imager for Solar Orbiter:
SO/PHI
Authors: Solanki, Sami K.; del Toro Iniesta, Jose Carlos; Woch,
Joachim; Gandorfer, Achim; Hirzberger, Johann; Schmidt, Wolfgang;
Appourchaux, Thierry; Alvarez-Herrero, Alberto
Bibcode: 2015IAUS..305..108S
Altcode: 2015arXiv150203368S
The Solar Orbiter is the next solar physics mission of the European
Space Agency, ESA, in collaboration with NASA, with a launch planned in
2018. The spacecraft is designed to approach the Sun to within 0.28 AU
at perihelion of a highly eccentric orbit. The proximity with the Sun
will also allow its observation at uniformly high resolution at EUV and
visible wavelengths. Such observations are central for learning more
about the magnetic coupling of the solar atmosphere. At a later phase
in the mission the spacecraft will leave the ecliptic and study the
enigmatic poles of the Sun from a heliographic latitude of up to 33°.
Title: Comparison of solar photospheric bright points between Sunrise
observations and MHD simulations
Authors: Riethmüller, T. L.; Solanki, S. K.; Berdyugina, S. V.;
Schüssler, M.; Martínez Pillet, V.; Feller, A.; Gandorfer, A.;
Hirzberger, J.
Bibcode: 2014A&A...568A..13R
Altcode: 2014arXiv1406.1387R
Bright points (BPs) in the solar photosphere are thought to be the
radiative signatures (small-scale brightness enhancements) of magnetic
elements described by slender flux tubes or sheets located in the darker
intergranular lanes in the solar photosphere. They contribute to the
ultraviolet (UV) flux variations over the solar cycle and hence may
play a role in influencing the Earth's climate. Here we aim to obtain
a better insight into their properties by combining high-resolution
UV and spectro-polarimetric observations of BPs by the Sunrise
Observatory with 3D compressible radiation magnetohydrodynamical
(MHD) simulations. To this end, full spectral line syntheses are
performed with the MHD data and a careful degradation is applied
to take into account all relevant instrumental effects of the
observations. In a first step it is demonstrated that the selected
MHD simulations reproduce the measured distributions of intensity at
multiple wavelengths, line-of-sight velocity, spectral line width,
and polarization degree rather well. The simulated line width also
displays the correct mean, but a scatter that is too small. In
the second step, the properties of observed BPs are compared with
synthetic ones. Again, these are found to match relatively well,
except that the observations display a tail of large BPs with strong
polarization signals (most likely network elements) not found in the
simulations, possibly due to the small size of the simulation box. The
higher spatial resolution of the simulations has a significant effect,
leading to smaller and more numerous BPs. The observation that most BPs
are weakly polarized is explained mainly by the spatial degradation,
the stray light contamination, and the temperature sensitivity of the Fe
i line at 5250.2 Å. Finally, given that the MHD simulations are highly
consistent with the observations, we used the simulations to explore
the properties of BPs further. The Stokes V asymmetries increase with
the distance to the center of the mean BP in both observations and
simulations, consistent with the classical picture of a production
of the asymmetry in the canopy. This is the first time that this has
been found also in the internetwork. More or less vertical kilogauss
magnetic fields are found for 98% of the synthetic BPs underlining
that basically every BP is associated with kilogauss fields. At the
continuum formation height, the simulated BPs are on average 190 K
hotter than the mean quiet Sun, the mean BP field strength is found to
be 1750 G, and the mean inclination is 17°, supporting the physical
flux-tube paradigm to describe BPs. On average, the synthetic BPs
harbor downflows increasing with depth. The origin of these downflows
is not yet understood very well and needs further investigation.
Title: Comparison between Mg II k and Ca II H Images Recorded by
SUNRISE/SuFI
Authors: Danilovic, S.; Hirzberger, J.; Riethmüller, T. L.; Solanki,
S. K.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Gizon, L.; Knölker,
M.; Schmidt, W.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.
Bibcode: 2014ApJ...784...20D
Altcode:
We present a comparison of high-resolution images of the solar surface
taken in the Mg II k and Ca II H channels of the Filter Imager on the
balloon-borne solar observatory SUNRISE. The Mg and Ca lines are sampled
with 0.48 nm and 0.11 nm wide filters, respectively. The two channels
show remarkable qualitative and quantitative similarities in the quiet
Sun, in an active region plage and during a small flare. However, the Mg
filtergrams display 1.4-1.7 times higher intensity contrast and appear
more smeared and smoothed in the quiet Sun. In addition, the fibrils
in a plage are wider. Although the exposure time is 100 times longer
for Mg images, the evidence suggests that these differences cannot be
explained only with instrumental effects or the evolution of the solar
scene. The differences at least partially arise because of different
line-formation heights, the stronger response of Mg k emission peaks
to the higher temperatures, and the larger height range sampled by
the broad Mg filter used here. This is evidently manifested during
the flare when a surge in Mg evolves differently than in Ca.
Title: Migration of Ca II H bright points in the internetwork
Authors: Jafarzadeh, S.; Cameron, R. H.; Solanki, S. K.; Pietarila,
A.; Feller, A.; Lagg, A.; Gandorfer, A.
Bibcode: 2014A&A...563A.101J
Altcode: 2014arXiv1401.7522J
Context. The migration of magnetic bright point-like features (MBP)
in the lower solar atmosphere reflects the dispersal of magnetic
flux as well as the horizontal flows of the atmospheric layer they
are embedded in.
Aims: We analyse trajectories of the proper
motion of intrinsically magnetic, isolated internetwork Ca ii H MBPs
(mean lifetime 461 ± 9 s) to obtain their diffusivity behaviour.
Methods: We use seeing-free high spatial and temporal resolution
image sequences of quiet-Sun, disc-centre observations obtained in
the Ca ii H 3968 Å passband of the Sunrise Filter Imager (SuFI)
onboard the Sunrise balloon-borne solar observatory. Small MBPs in
the internetwork are automatically tracked. The trajectory of each
MBP is then calculated and described by a diffusion index (γ) and
a diffusion coefficient (D). We also explore the distribution of the
diffusion indices with the help of a Monte Carlo simulation.
Results: We find γ = 1.69 ± 0.08 and D = 257 ± 32 km2
s-1 averaged over all MBPs. Trajectories of most MBPs are
classified as super-diffusive, i.e. γ > 1, with the determined γ
being the largest obtained so far to our knowledge. A direct correlation
between D and timescale (τ) determined from trajectories of all MBPs is
also obtained. We discuss a simple scenario to explain the diffusivity
of the observed, relatively short-lived MBPs while they migrate within
a small area in a supergranule (i.e. an internetwork area). We show
that the scatter in the γ values obtained for individual MBPs is due
to their limited lifetimes.
Conclusions: The super-diffusive
MBPs can be described as random walkers (due to granular evolution and
intergranular turbulence) superposed on a large systematic (background)
velocity, caused by granular, mesogranular, and supergranular flows.
Title: First High-resolution Images of the Sun in the 2796 Å Mg II
k Line
Authors: Riethmüller, T. L.; Solanki, S. K.; Hirzberger, J.;
Danilovic, S.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Gizon, L.;
Knölker, M.; Schmidt, W.; Del Toro Iniesta, J. C.
Bibcode: 2013ApJ...776L..13R
Altcode: 2013arXiv1309.5213R
We present the first high-resolution solar images in the Mg II k 2796
Å line. The images, taken through a 4.8 Å broad interference filter,
were obtained during the second science flight of Sunrise in 2013 June
by the Sunrise Filter Imager (SuFI) instrument. The Mg II k images
display structures that look qualitatively very similar to images taken
in the core of Ca II H. The Mg II images exhibit reversed granulation
(or shock waves) in the internetwork regions of the quiet Sun, at
intensity contrasts that are similar to those found in Ca II H. Very
prominent in Mg II are bright points, both in the quiet Sun and in plage
regions, particularly near the disk center. These are much brighter than
at other wavelengths sampled at similar resolution. Furthermore, Mg II k
images also show fibril structures associated with plage regions. Again,
the fibrils are similar to those seen in Ca II H images, but tend to
be more pronounced, particularly in weak plage.
Title: Evolution of the Fine Structure of Magnetic Fields in the
Quiet Sun: Observations from Sunrise/IMaX and Extrapolations
Authors: Wiegelmann, T.; Solanki, S. K.; Borrero, J. M.; Peter,
H.; Barthol, P.; Gandorfer, A.; Martínez Pillet, V.; Schmidt, W.;
Knölker, M.
Bibcode: 2013SoPh..283..253W
Altcode:
Observations with the balloon-borne Sunrise/Imaging Magnetograph
eXperiment (IMaX) provide high spatial resolution (roughly 100 km at
disk center) measurements of the magnetic field in the photosphere of
the quiet Sun. To investigate the magnetic structure of the chromosphere
and corona, we extrapolate these photospheric measurements into
the upper solar atmosphere and analyze a 22-minute long time series
with a cadence of 33 seconds. Using the extrapolated magnetic-field
lines as tracer, we investigate temporal evolution of the magnetic
connectivity in the quiet Sun's atmosphere. The majority of magnetic
loops are asymmetric in the sense that the photospheric field strength
at the loop foot points is very different. We find that the magnetic
connectivity of the loops changes rapidly with a typical connection
recycling time of about 3±1 minutes in the upper solar atmosphere and
12±4 minutes in the photosphere. This is considerably shorter than
previously found. Nonetheless, our estimate of the energy released by
the associated magnetic-reconnection processes is not likely to be the
sole source for heating the chromosphere and corona in the quiet Sun.
Title: First Results from the SUNRISE Mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller,
T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González,
M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta,
J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González,
N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt,
W.; Steiner, O.; Title, A. M.
Bibcode: 2012ASPC..455..143S
Altcode:
The SUNRISE balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that reveal the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the SUNRISE data, which include a number of discoveries.
Title: Detection of Vortex Tubes in Solar Granulation from
Observations SUNRISE
Authors: Steiner, O.; Franz, M.; González, N. B.; Nutto, C.; Rezaei,
R.; Pillet, V. M.; Bonet, J. A.; Iniesta, J. C. d. T.; Domingo, V.;
Solanki, S. K.; Knölker, M.; Schmidt, W.; Barthol, P.; Gandorfer, A.
Bibcode: 2012ASPC..455...35S
Altcode:
We investigated a time series of continuum intensity maps and
Dopplergrams of granulation in a very quiet solar region at the disk
center, recorded with the Imaging Magnetograph eXperiment (IMaX)
on board the balloon-borne solar observatory SUNRISE. We find that
granules frequently show substructure in the form of lanes composed of
a leading bright rim and a trailing dark edge, which move together
from the boundary of a granule into the granule itself. We find
strikingly similar events in synthesized intensity maps from an ab
initio numerical simulation of solar surface convection. We conclude
that these granular lanes are the visible signature of (horizontally
oriented) vortex tubes. The characteristic optical appearance of vortex
tubes at the solar surface is explained. This paper is a summary and
update of the results previously presented in Steiner et al. (2010).
Title: Supersonic Magnetic Flows in the Quiet Sun Observed with
SUNRISE/IMaX
Authors: Borrero, J. M.; Pillet, V. M.; Schlichenmaier, R.; Schmidt,
W.; Berkefeld, T.; Solanki, S. K.; Bonet, J. A.; Iniesta, J. C. d. T.;
Domingo, V.; Barthol, P.; Gandorfer, A.
Bibcode: 2012ASPC..455..155B
Altcode: 2012arXiv1202.4354B
In this contribution we describe some recent observations of high-speed
magnetized flows in the quiet Sun granulation. These observations
were carried out with the Imaging Magnetograph eXperiment (IMaX)
onboard the stratospheric balloon SUNRISE, and possess an unprecedented
spatial resolution and temporal cadence. These flows were identified as
highly shifted circular polarization (Stokes V) signals. We estimate
the LOS velocity responsible for these shifts to be larger than 6 km
s-1, and therefore we refer to them as supersonic magnetic
flows. The average lifetime of the detected events is 81.3 s and
they occupy an average area of about 23 000 km2. Most of
the events occur within granular cells and correspond therefore to
upflows. However some others occur in intergranular lanes or bear no
clear relation to the convective velocity pattern. We analyze a number
of representative examples and discuss them in terms of magnetic loops,
reconnection events, and convective collapse.
Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic
field in the upper atmosphere of our closest star
Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad,
A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt,
W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.;
Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald,
V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.;
Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.;
Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.;
Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C.
Bibcode: 2012ExA....33..271P
Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P
The magnetic field plays a pivotal role in many fields of
Astrophysics. This is especially true for the physics of the solar
atmosphere. Measuring the magnetic field in the upper solar atmosphere
is crucial to understand the nature of the underlying physical
processes that drive the violent dynamics of the solar corona—that
can also affect life on Earth. SolmeX, a fully equipped solar space
observatory for remote-sensing observations, will provide the first
comprehensive measurements of the strength and direction of the
magnetic field in the upper solar atmosphere. The mission consists
of two spacecraft, one carrying the instruments, and another one in
formation flight at a distance of about 200 m carrying the occulter to
provide an artificial total solar eclipse. This will ensure high-quality
coronagraphic observations above the solar limb. SolmeX integrates two
spectro-polarimetric coronagraphs for off-limb observations, one in
the EUV and one in the IR, and three instruments for observations on
the disk. The latter comprises one imaging polarimeter in the EUV for
coronal studies, a spectro-polarimeter in the EUV to investigate the low
corona, and an imaging spectro-polarimeter in the UV for chromospheric
studies. SOHO and other existing missions have investigated the emission
of the upper atmosphere in detail (not considering polarization),
and as this will be the case also for missions planned for the near
future. Therefore it is timely that SolmeX provides the final piece of
the observational quest by measuring the magnetic field in the upper
atmosphere through polarimetric observations.
Title: Solar Particle Acceleration Radiation and Kinetics (SPARK). A
mission to understand the nature of particle acceleration
Authors: Matthews, Sarah A.; Williams, David R.; Klein, Karl-Ludwig;
Kontar, Eduard P.; Smith, David M.; Lagg, Andreas; Krucker, Sam;
Hurford, Gordon J.; Vilmer, Nicole; MacKinnon, Alexander L.; Zharkova,
Valentina V.; Fletcher, Lyndsay; Hannah, Iain G.; Browning, Philippa
K.; Innes, Davina E.; Trottet, Gerard; Foullon, Clare; Nakariakov,
Valery M.; Green, Lucie M.; Lamoureux, Herve; Forsyth, Colin; Walton,
David M.; Mathioudakis, Mihalis; Gandorfer, Achim; Martinez-Pillet,
Valentin; Limousin, Olivier; Verwichte, Erwin; Dalla, Silvia; Mann,
Gottfried; Aurass, Henri; Neukirch, Thomas
Bibcode: 2012ExA....33..237M
Altcode: 2011ExA...tmp..124M
Energetic particles are critical components of plasma populations
found throughout the universe. In many cases particles are accelerated
to relativistic energies and represent a substantial fraction of
the total energy of the system, thus requiring extremely efficient
acceleration processes. The production of accelerated particles
also appears coupled to magnetic field evolution in astrophysical
plasmas through the turbulent magnetic fields produced by diffusive
shock acceleration. Particle acceleration is thus a key component
in helping to understand the origin and evolution of magnetic
structures in, e.g. galaxies. The proximity of the Sun and the range
of high-resolution diagnostics available within the solar atmosphere
offers unique opportunities to study the processes involved in particle
acceleration through the use of a combination of remote sensing
observations of the radiative signatures of accelerated particles, and
of their plasma and magnetic environment. The SPARK concept targets the
broad range of energy, spatial and temporal scales over which particle
acceleration occurs in the solar atmosphere, in order to determine how
and where energetic particles are accelerated. SPARK combines highly
complementary imaging and spectroscopic observations of radiation from
energetic electrons, protons and ions set in their plasma and magnetic
context. The payload comprises focusing-optics X-ray imaging covering
the range from 1 to 60 keV; indirect HXR imaging and spectroscopy
from 5 to 200 keV, γ-ray spectroscopic imaging with high-resolution
LaBr3 scintillators, and photometry and source localisation
at far-infrared wavelengths. The plasma environment of the regions
of acceleration and interaction will be probed using soft X-ray
imaging of the corona and vector magnetography of the photosphere
and chromosphere. SPARK is designed for solar research. However,
in addition it will be able to provide exciting new insights into the
origin of particle acceleration in other regimes, including terrestrial
gamma-ray flashes (TGF), the origin of γ-ray bursts, and the possible
existence of axions.
Title: Diffusivity of Isolated Internetwork Ca II H Bright Points
Observed by SuFI/SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.;
Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A.
Bibcode: 2012decs.confE..99J
Altcode:
We analyze trajectories of the proper motion of intrinsically magnetic,
isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to
obtain their diffusivity behaviors. We use high spatial and temporal
resolution image sequences of quiet-Sun, disc-centre observations
obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager
(SuFI) on board the SUNRISE balloon-borne solar observatory. In
order to avoid misidentification, the BPs are semi-manually selected
and then automatically tracked. The trajectory of each BP is then
calculated and its diffusion index is described by a power law
exponent, using which we classify the BPs' trajectories into sub-,
normal and super- diffusive. In addition, the corresponding diffusion
coefficients (D) based on the observed displacements are consequently
computed. We find a strong super-diffusivity at a height sampled by the
SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to
the temperature minimum). We find that 74% of the identified tiny BPs
are super-diffusive, 18% move randomly (i.e. their motion corresponds
to normal diffusion) and only 8% belong to the sub-diffusion regime. In
addition, we find that 53% of the super-diffusion regime (i.e. 39% of
all BPs) have the diffusivity index of 2 which are termed as "Ballistic
BPs". Finally, we explore the distribution of diffusion index with the
help of a simple simulation. The results suggest that the BPs are random
walkers superposed by a systematic (background) velocity in which the
magnitude of each component (and hence their ratio) depends on the time
and spatial scales. We further discuss a simple sketch to explain the
diffusivity of observed BPs while they migrate within a supergranule
(i.e. internetwork areas) or close to the network regions.
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.
Bibcode: 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.
Title: Magnetic field emergence in mesogranular-sized exploding
granules observed with sunrise/IMaX data
Authors: Palacios, J.; Blanco Rodríguez, J.; Vargas Domínguez, S.;
Domingo, V.; Martínez Pillet, V.; Bonet, J. A.; Bellot Rubio, L. R.;
Del Toro Iniesta, J. C.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Berkefeld, T.; Schmidt, W.; Knölker, M.
Bibcode: 2012A&A...537A..21P
Altcode: 2011arXiv1110.4555P
We report on magnetic field emergences covering significant
areas of exploding granules. The balloon-borne mission Sunrise
provided high spatial and temporal resolution images of the solar
photosphere. Continuum images, longitudinal and transverse magnetic
field maps and Dopplergrams obtained by IMaX onboard Sunrise are
analyzed by local correlation traking (LCT), divergence calculation
and time slices, Stokes inversions and numerical simulations are also
employed. We characterize two mesogranular-scale exploding granules
where ~1018 Mx of magnetic flux emerges. The emergence
of weak unipolar longitudinal fields (~100 G) start with a single
visible magnetic polarity, occupying their respective granules' top
and following the granular splitting. After a while, mixed polarities
start appearing, concentrated in downflow lanes. The events last around
20 min. LCT analyses confirm mesogranular scale expansion, displaying
a similar pattern for all the physical properties, and divergence
centers match between all of them. We found a similar behaviour
with the emergence events in a numerical MHD simulation. Granule
expansion velocities are around 1 kms-1 while magnetic
patches expand at 0.65 kms-1. One of the analyzed events
evidences the emergence of a loop-like structure. Advection of
the emerging magnetic flux features is dominated by convective
motion resulting from the exploding granule due to the magnetic
field frozen in the granular plasma. Intensification of the
magnetic field occurs in the intergranular lanes, probably
because of being directed by the downflowing plasma.