Author name code: bemporad
ADS astronomy entries on 2022-09-14
author:"Bemporad, Alessandro"
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Title: Coronal mass ejection followed by a prominence eruption and
a plasma blob as observed by Solar Orbiter
Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro,
D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu,
D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel,
P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse,
G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli,
M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L.
Bibcode: 2022A&A...665A...7B
Altcode: 2022arXiv220210294B
Context. On 2021 February 12, two subsequent eruptions occurred above
the western limb of the Sun, as seen along the Sun-Earth line. The
first event was a typical slow coronal mass ejection (CME), followed
∼7 h later by a smaller and collimated prominence eruption,
originating south of the CME, followed by a plasma blob. These
events were observed not only by the SOHO and STEREO-A missions,
but also by the suite of remote-sensing instruments on board Solar
Orbiter.
Aims: We show how data acquired by the Full Sun
Imager (FSI), the Metis coronagraph, and the Heliospheric Imager
(HI) from the Solar Orbiter perspective can be combined to study
the eruptions and different source regions. Moreover, we show how
Metis data can be analyzed to provide new information about solar
eruptions.
Methods: Different 3D reconstruction methods were
applied to the data acquired by different spacecraft, including
remote-sensing instruments on board Solar Orbiter. Images acquired
by the two Metis channels in the visible light (VL) and H I Ly-α
line (UV) were combined to derive physical information about the
expanding plasma. The polarization ratio technique was also applied
for the first time to Metis images acquired in the VL channel.
Results: The two eruptions were followed in 3D from their source
region to their expansion in the intermediate corona. By combining
VL and UV Metis data, the formation of a post-CME current sheet (CS)
was followed for the first time in the intermediate corona. The
plasma temperature gradient across a post-CME blob propagating
along the CS was also measured for the first time. Application
of the polarization ratio technique to Metis data shows that by
combining four different polarization measurements, the errors are
reduced by ∼5 − 7%. This constrains the 3D plasma distribution
better. Movies associated to Figs. 4-7 are available at https://www.aanda.org
Title: Metis/Solar Orbiter Observation of Comets
Authors: Matteo Giordano, Silvio; Mancuso, Salvatore; Bemporad,
Alessandro; Raymond, John; Battams, Karl; Da Deppo, Vania; Knight,
Matthew; Nisticò, Giuseppe; Corso, Alain J.
Bibcode: 2022cosp...44.1353M
Altcode:
The Metis coronagraph on-board the Solar Orbiter mission, focused on
the study of the solar corona, has also detected also near-Sun comets
in the first two years of observations. Metis observes comets passing
into the field of view covering an annulus between 1.5° and 2.9°
centered in the Sun direction, with a spatial resolution of 20 arcsec,
the corresponding imaged heliocentric distance ranges from 1.6 to 12
Solar Radii depending on the spacecraft distance from the Sun. The
two instrument channels, UV narrow band HI Lyman-α at 121.6 nm, and
the polarized broad-band visible light (580 - 640 nm) can be operated
with high cadence, then, for the first time, Metis allows simultaneous
observation of 2D comet images both in the visible and in the UV
emission. These observations provide direct information on cometary
parameters (e.g. water outgassing rate, coma and tail composition,
fragmentation) and allow to constrain the physical parameters of the
coronal plasma encountering the comet (e.g. electron density and solar
wind velocity). Collaboration with currently operational missions
(in particular SOHO and STEREO) allows to improve the stereoscopic
description of observed comets and to determine more accurately the
orbital parameters. Based on studies from SOHO observations, we expect
to regularly observe comets. A project is underway to systematically
research the comets detected by Metis. In this paper, we present the
first results obtained with the observations of the long period comet
C/2021 A1 (Leonard), and two sungrazing comets observed on September
2nd and December 24th, 2021.
Title: Polarimetric Studies of a Fast Coronal Mass Ejection
Authors: Mierla, Marilena; Inhester, Bernd; Zhukov, Andrei N.; Shestov,
Sergei V.; Bemporad, Alessandro; Lamy, Philippe; Koutchmy, Serge
Bibcode: 2022SoPh..297...78M
Altcode: 2022arXiv220604411M
In this work we performed a polarimetric study of a fast and wide
coronal mass ejection (CME) observed on 12 July 2012 by the COR1 and
COR2 instruments onboard the Solar TErrestrial RElations Observatory
(STEREO) mission. The CME source region was an X1.4 flare located at
approximately S15W01 on the solar disk, as observed from the Earth's
perspective. The position of the CME as derived from the 3D Graduated
Cylindrical Shell (GCS) reconstruction method was at around S18W00
at 2.5 solar radii and S07W00 at 5.7 solar radii, meaning that the
CME was deflected towards the Equator while propagating outward in
the corona. The projected speed of the leading edge of the CME also
evolved from around 200 km s−1 in the lower corona to
around 1000 km s−1 in the COR2 field of view. The degree
of polarisation of the CME is around 65% but it can go as high as 80%
in some CME regions. The CME showed deviation of the polarisation
angle from the tangential in the range of 10 - 15∘ (or
more). Our analysis showed that this is mostly due to the fact that the
sequence of three polarised images from where the polarised parameters
are derived is not taken simultaneously, but at a difference of a few
seconds in time. In this interval of time, the CME moves by at least
two pixels in the FOV of the instruments and this displacement results
in uncertainties in the polarisation parameters (degree of polarisation,
polarisation angle, etc.). We propose some steps forward to improve the
derivation of the polarisation. This study is important for analysing
the future data from instruments with polarisation capabilities.
Title: Acceleration of Solar Energetic Particles through CME-driven
Shock and Streamer Interaction
Authors: Frassati, Federica; Laurenza, Monica; Bemporad, Alessandro;
West, Matthew J.; Mancuso, Salvatore; Susino, Roberto; Alberti,
Tommaso; Romano, Paolo
Bibcode: 2022ApJ...926..227F
Altcode:
On 2013 June 21, a solar prominence eruption was observed, accompanied
by an M2.9 class flare, a fast coronal mass ejection, and a type II
radio burst. The concomitant emission of solar energetic particles
(SEPs) produced a significant proton flux increase, in the energy
range 4-100 MeV, measured by the Low and High Energy Telescopes
on board the Solar TErrestrial RElations Observatory (STEREO)-B
spacecraft. Only small enhancements, at lower energies, were observed
at the STEREO-A and Geostationary Operational Environmental Satellite
(GOES) spacecraft. This work investigates the relationship between
the expanding front, coronal streamers, and the SEP fluxes observed
at different locations. Extreme-ultraviolet data, acquired by the
Atmospheric Imaging Assembly (AIA) instrument on board the Solar
Dynamics Observatory (SDO), were used to study the expanding front
and its interaction with streamer structures in the low corona. The
3D shape of the expanding front was reconstructed and extrapolated
at different times by using SDO/AIA, STEREO/Sun Earth Connection
Coronal and Heliospheric Investigation, and Solar and Heliospheric
Observatory/Large Angle and Spectrometric Coronagraph observations
with a spheroidal model. By adopting a potential field source surface
approximation and estimating the magnetic connection of the Parker
spiral, below and above 2.5 R ⊙, we found that during
the early expansion of the eruption, the front had a strong magnetic
connection with STEREO-B (between the nose and flank of the eruption
front) while having a weak connection with STEREO-A and GOES. The
obtained results provide evidence, for the first time, that the
interaction between an expanding front and streamer structures can be
responsible for the acceleration of high-energy SEPs up to at least
100 MeV, as it favors particle trapping and hence increases the shock
acceleration efficiency.
Title: Ultraviolet Observations of Comet 96/P Machholz at Perihelion
Authors: Raymond, J. C.; Giordano, S.; Mancuso, S.; Povich, Matthew
S.; Bemporad, A.
Bibcode: 2022ApJ...926...93R
Altcode: 2021arXiv211115644R
Ultraviolet spectra of Comet 96/P Machholz were obtained during
its 2002 perihelion with the UltraViolet Coronagraph Spectrometer
instrument on board the SOHO satellite. Emission from H I, C II,
C III, and O I is detected near the nucleus. The outgassing rate is
in line with the value extrapolated from rates at larger distances
from the Sun, and abundances of C and O are estimated. Reconstructed
images show a nearly spherical cloud of H I Lyα emission and an ion
tail seen in C III. Radiation pressure on the hydrogen atoms produces
a modest distortion of the shape of the Lyα cloud as seen from SOHO
and Doppler shifts up to 30 km s-1 in the outer parts of
the cloud. We estimate a ratio of C to H2O similar to what
is observed in other comets, so low carbon abundance does not account
for the anomalously low C2 and C3 ratios to
NH2 observed at optical wavelengths.
Title: Combining the Derived Solar Wind Outflow Velocity in the
Inner Corona with the Modelled Magnetic Field
Authors: Casti, Marta; Arge, Charles; Bemporad, Alessandro; Henney,
Carl
Bibcode: 2021AGUFMSH24C..08C
Altcode:
In this work, we discuss the possibility and the potential advantages
of combining synoptic maps reporting the solar wind speed distribution
in corona, obtained exploiting the Doppler Dimming technique, with the
solution of the Wang-Sheeley-Arge (WSA) model. The Doppler Dimming
technique is one of the methods developed to derive the fast and
the slow solar wind speed in the acceleration region, where direct
measurements are not possible. This technique allows retrieval of
the proton speed starting from simultaneous observations in polarized
visible light and in the hydrogen Lyman-alpha line (i.e., 121.6 nm)
of the inner solar corona. Such results have been used in previous
works to generate synoptics maps, at different heliospheric distances,
of the coronal outflow speed projected on the plane-of-the-sky. On
the other hand, the WSA model not only provides a prediction of the
solar wind parameters in the vicinity of a selected satellite, but
also a full reconstruction of the magnetic field lines distribution
for a given photospheric magnetic field map. Magnetic field lines are
traced back from an assigned heliospheric distance to 1 solar radius
and characterized in terms of geometry and associated parameters
such as magnetic field strength both along the line and at the
footprint, distance from the nearest coronal boundary, and expansion
factor. Combining WSA results with the derived outflow speed could lead
to better understanding of the sources, origins, and acceleration of
the solar wind.
Title: The first coronal mass ejection observed in both visible-light
and UV H I Ly-α channels of the Metis coronagraph on board Solar
Orbiter
Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini,
F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.;
Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.;
Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki,
A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto,
P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto,
F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.;
Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.;
Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus,
Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar
Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.;
Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter,
H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan,
L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.;
Woch, J.; Zimbardo, G.
Bibcode: 2021A&A...656L..14A
Altcode:
Context. The Metis coronagraph on board Solar Orbiter offers a new
view of coronal mass ejections (CMEs), observing them for the first
time with simultaneous images acquired with a broad-band filter in
the visible-light interval and with a narrow-band filter around the
H I Ly-α line at 121.567 nm, the so-called Metis UV channel.
Aims: We show the first Metis observations of a CME, obtained on 16
and 17 January 2021. The event was also observed by the EUI/FSI imager
on board Solar Orbiter, as well as by other space-based coronagraphs,
such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here
with Metis data.
Methods: Different images are analysed here
to reconstruct the 3D orientation of the expanding CME flux rope using
the graduated cylindrical shell model. This also allows us to identify
the possible location of the source region. Measurements of the CME
kinematics allow us to quantify the expected Doppler dimming in the
Ly-α channel.
Results: Observations show that most CME features
seen in the visible-light images are also seen in the Ly-α images,
although some features in the latter channel appear more structured
than their visible-light counterparts. We estimated the expansion
velocity of this event to be below 140 km s−1. Hence,
these observations can be understood by assuming that Doppler dimming
effects do not strongly reduce the Ly-α emission from the CME. These
velocities are comparable with or smaller than the radial velocities
inferred from the same data in a similar coronal structure on the
east side of the Sun.
Conclusions: The first observations by
Metis of a CME demonstrate the capability of the instrument to provide
valuable and novel information on the structure and dynamics of these
coronal events. Considering also its diagnostics capabilities regarding
the conditions of the ambient corona, Metis promises to significantly
advance our knowledge of such phenomena. Movies are available at https://www.aanda.org
Title: Cosmic-ray flux predictions and observations for and with
Metis on board Solar Orbiter
Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi,
M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.;
Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.;
Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.;
De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.;
Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.;
Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.;
Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca,
L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P.
Bibcode: 2021A&A...656A..15G
Altcode: 2021arXiv210413700G
Context. The Metis coronagraph is one of the remote sensing instruments
hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted
to carry out the first simultaneous imaging of the solar corona in
both visible light (VL) and ultraviolet (UV). High-energy particles
can penetrate spacecraft materials and may limit the performance of
the on-board instruments. A study of the galactic cosmic-ray (GCR)
tracks observed in the first VL images gathered by Metis during the
commissioning phase is presented here. A similar analysis is planned
for the UV channel.
Aims: We aim to formulate a prediction of
the GCR flux up to hundreds of GeV for the first part of the Solar
Orbiter mission to study the performance of the Metis coronagraph.
Methods: The GCR model predictions are compared to observations
gathered on board Solar Orbiter by the High-Energy Telescope in the
range between 10 MeV and 100 MeV in the summer of 2020 as well as with
the previous measurements. Estimated cosmic-ray fluxes above 70 MeV
n−1 have been also parameterized and used for Monte Carlo
simulations aimed at reproducing the cosmic-ray track observations in
the Metis coronagraph VL images. The same parameterizations can also
be used to study the performance of other detectors.
Results:
By comparing observations of cosmic-ray tracks in the Metis VL images
with FLUKA Monte Carlo simulations of cosmic-ray interactions in
the VL detector, we find that cosmic rays fire only a fraction, on
the order of 10−4, of the whole image pixel sample. We
also find that the overall efficiency for cosmic-ray identification
in the Metis VL images is approximately equal to the contribution
of Z ≥ 2 GCR particles. A similar study will be carried out during
the whole of the Solar Orbiter's mission duration for the purposes of
instrument diagnostics and to verify whether the Metis data and Monte
Carlo simulations would allow for a long-term monitoring of the GCR
proton flux.
Title: First light observations of the solar wind in the outer corona
with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
Bibcode: 2021A&A...656A..32R
Altcode: 2021arXiv210613344R
In this work, we present an investigation of the wind in the solar
corona that has been initiated by observations of the resonantly
scattered ultraviolet emission of the coronal plasma obtained with
UVCS-SOHO, designed to measure the wind outflow speed by applying
Doppler dimming diagnostics. Metis on Solar Orbiter complements the
UVCS spectroscopic observations that were performed during solar
activity cycle 23 by simultaneously imaging the polarized visible
light and the H I Lyman-α corona in order to obtain high spatial and
temporal resolution maps of the outward velocity of the continuously
expanding solar atmosphere. The Metis observations, taken on May 15,
2020, provide the first H I Lyman-α images of the extended corona
and the first instantaneous map of the speed of the coronal plasma
outflows during the minimum of solar activity and allow us to identify
the layer where the slow wind flow is observed. The polarized visible
light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal
emissions, obtained with the two Metis channels, were combined in
order to measure the dimming of the UV emission relative to a static
corona. This effect is caused by the outward motion of the coronal
plasma along the direction of incidence of the chromospheric photons
on the coronal neutral hydrogen. The plasma outflow velocity was then
derived as a function of the measured Doppler dimming. The static
corona UV emission was simulated on the basis of the plasma electron
density inferred from the polarized visible light. This study leads
to the identification, in the velocity maps of the solar corona, of
the high-density layer about ±10° wide, centered on the extension
of a quiet equatorial streamer present at the east limb - the coronal
origin of the heliospheric current sheet - where the slowest wind
flows at about 160 ± 18 km s−1 from 4 R⊙
to 6 R⊙. Beyond the boundaries of the high-density layer,
the wind velocity rapidly increases, marking the transition between
slow and fast wind in the corona.
Title: Tracing the ICME plasma with a MHD simulation
Authors: Biondo, Ruggero; Pagano, Paolo; Reale, Fabio; Bemporad,
Alessandro
Bibcode: 2021A&A...654L...3B
Altcode:
The determination of the chemical composition of interplanetary coronal
mass ejection (ICME) plasma is an open issue. More specifically,
it is not yet fully understood how remote sensing observations
of the solar corona plasma during solar disturbances evolve into
plasma properties measured in situ away from the Sun. The ambient
conditions of the background interplanetary plasma are important for
space weather because they influence the evolutions, arrival times,
and geo-effectiveness of the disturbances. The Reverse In situ and MHD
APproach (RIMAP) is a technique to reconstruct the heliosphere on the
ecliptic plane (including the magnetic Parker spiral) directly from in
situ measurements acquired at 1 AU. It combines analytical and numerical
approaches, preserving the small-scale longitudinal variability of the
wind flow lines. In this work, we use RIMAP to test the interaction of
an ICME with the interplanetary medium. We model the propagation of
a homogeneous non-magnetised (i.e. with no internal flux rope) cloud
starting at 800 km s−1 at 0.1 AU out to 1.1 AU. Our 3D
magnetohydrodynamics (MHD) simulation made with the PLUTO MHD code shows
the formation of a compression front ahead of the ICME, continuously
driven by the cloud expansion. Using a passive tracer, we find that
the initial ICME material does not fragment behind the front during
its propagation, and we quantify the mixing of the propagating plasma
cloud with the ambient solar wind plasma, which can be detected
at 1 AU. Movie associated with Fig. 1 is available at https://www.aanda.org
Title: Combining white light and UV Lyman-α coronagraphic images
to determine the solar wind speed. The quick inversion method
Authors: Bemporad, A.; Giordano, S.; Zangrilli, L.; Frassati, F.
Bibcode: 2021A&A...654A..58B
Altcode: 2021arXiv210706811B
Context. The availability of multi-channel coronagraphic images in
different wavelength intervals acquired from the space will provide
a new view of the solar corona, allowing us to investigate the 2D
distribution and time evolution of many plasma physical parameters,
such as plasma density, temperature, and outflow speed.
Aims:
This work focuses on the combination of white light (WL) and UV (Lyα)
coronagraphic images to demonstrate the capability of measuring the
solar wind speed in the inner corona directly with the ratio of these
two images (a technique called the quick inversion method), thus
avoiding having to account for the line-of-sight (LOS) integration
effects in the inversion of data.
Methods: After a derivation
of the theoretical basis and illustration of the main hypotheses in
the quick inversion method, the data inversion technique is tested
first with 1D radial analytic profiles and then with 3D numerical
MHD simulations in order to show the effects of variabilities related
to different phases of the solar activity cycle and the complex LOS
distribution of plasma parameters. The same technique is also applied
to average WL and UV images obtained from real data acquired by the
SOHO UVCS and LASCO instruments around the minimum and maximum of the
solar activity cycle.
Results: Comparisons between input and
output velocities show a good agreement overall, demonstrating that
this method, which allowed us to infer the solar wind speed with the
WL-to-UV image ratio, can be complementary to more complex techniques
requiring the full LOS integration. The analysis described here also
allowed us to quantify the possible errors in the outflow speed, and to
identify the coronal regions where the quick inversion method performs
at the best. The quick inversion applied to real UVCS and LASCO data
also allowed us to reconstruct the typical bimodal distribution of fast
and slow wind at solar minimum, and to derive a more complex picture
around the solar maximum.
Conclusions: The application of the
technique shown here will be very important for the future analyses
of data acquired with multi-channel WL and UV (Lyα) coronagraphs,
such as Metis on board the Solar Orbiter, LST on board ASO-S, and any
other future WL and UV Lyα multi-channel coronagraphs.
Title: Exploring the Solar Wind from Its Source on the Corona into
the Inner Heliosphere during the First Solar Orbiter-Parker Solar
Probe Quadrature
Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester;
Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano;
Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.;
Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd
D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.;
Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case,
Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso,
Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry;
Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino,
Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck,
Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro;
Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David
M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto,
Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco,
Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale,
Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini,
Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca,
Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli,
Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano;
Zuppella, Paola
Bibcode: 2021ApJ...920L..14T
Altcode: 2021arXiv211011031T
This Letter addresses the first Solar Orbiter (SO)-Parker Solar
Probe (PSP) quadrature, occurring on 2021 January 18 to investigate
the evolution of solar wind from the extended corona to the inner
heliosphere. Assuming ballistic propagation, the same plasma volume
observed remotely in the corona at altitudes between 3.5 and 6.3
solar radii above the solar limb with the Metis coronagraph on SO
can be tracked to PSP, orbiting at 0.1 au, thus allowing the local
properties of the solar wind to be linked to the coronal source region
from where it originated. Thanks to the close approach of PSP to the
Sun and the simultaneous Metis observation of the solar corona, the
flow-aligned magnetic field and the bulk kinetic energy flux density
can be empirically inferred along the coronal current sheet with an
unprecedented accuracy, allowing in particular estimation of the Alfvén
radius at 8.7 solar radii during the time of this event. This is thus
the very first study of the same solar wind plasma as it expands from
the sub-Alfvénic solar corona to just above the Alfvén surface.
Title: Effects of the chromospheric Lyα line profile shape on
the determination of the solar wind H I outflow velocity using the
Doppler dimming technique
Authors: Capuano, G. E.; Dolei, S.; Spadaro, D.; Guglielmino, S. L.;
Romano, P.; Ventura, R.; Andretta, V.; Bemporad, A.; Sasso, C.;
Susino, R.; Da Deppo, V.; Frassetto, F.; Giordano, S. M.; Landini,
F.; Nicolini, G.; Pancrazzi, M.; Romoli, M.; Zangrilli, L.
Bibcode: 2021A&A...652A..85C
Altcode: 2021arXiv210805957C
Context. The determination of solar wind H I outflow velocity is
fundamental to shedding light on the mechanisms of wind acceleration
occurring in the corona. Moreover, it has implications in various
astrophysical contexts, such as in the heliosphere and in cometary
and planetary atmospheres.
Aims: We aim to study the effects
of the chromospheric Lyα line profile shape on the determination
of the outflow speed of coronal H I atoms via the Doppler dimming
technique. This is of particular interest in view of the upcoming
measurements of the Metis coronagraph aboard the Solar Orbiter
mission.
Methods: The Doppler dimming technique exploits the
decrease of coronal Lyα radiation in regions where H I atoms flow out
in the solar wind. Starting from UV observations of the coronal Lyα
line from the Solar and Heliospheric Observatory (SOHO), aboard the
UltraViolet Coronagraph Spectrometer, and simultaneous measurements
of coronal electron densities from pB coronagraphic observations, we
explored the effect of the profile of the pumping chromospheric Lyα
line. We used measurements from the Solar UV Measurement of Emitted
Radiation, aboard SOHO, the Ultraviolet Spectrometer and Polarimeter,
aboard the Solar Maximum Mission, and the Laboratoire de Physique
Stellaire et Planetaire, aboard the Eight Orbiting Solar Observatory,
both from representative on-disc regions, such as coronal holes
and quiet Sun and active regions, and as a function of time during
the solar activity cycle. In particular, we considered the effect
of four chromospheric line parameters: line width, reversal depth,
asymmetry, and distance of the peaks.
Results: We find that
the range of variability of the four line parameters is of about 50%
for the width, 69% for the reversal depth, and 35% and 50% for the
asymmetry and distance of the peaks, respectively. We then find that
the variability of the pumping Lyα profile affects the estimates of
the coronal H I velocity by about 9−12%. This uncertainty is smaller
than the uncertainties due to variations of other physical quantities,
such as electron density, electron temperature, H I temperature, and
integrated chromospheric Lyα radiance.
Conclusions: Our work
suggests that the observed variations in the chromospheric Lyα line
profile parameters along a cycle and in specific regions negligibly
affect the determination of the solar wind speed of H I atoms. Due
to this weak dependence, a unique shape of the Lyα profile over
the solar disc that is constant in time can be adopted to obtain the
values of the solar wind H I outflow velocity. Moreover, the use of an
empirical analytical chromospheric profile of the Lyα, assumed uniform
over the solar disc and constant in time, is justifiable in order to
obtain a good estimate of the coronal wind H I outflow velocity using
coronagraphic UV images.
Title: Magnetic imaging of the outer solar atmosphere (MImOSA)
Authors: Peter, H.; Ballester, E. Alsina; Andretta, V.; Auchère, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; Alemán, T. del Pino; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo
Bibcode: 2021ExA...tmp...95P
Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability of
planets orbiting these host stars. Although the magnetic field at the
surface of the Sun is reasonably well characterised by observations,
the information on the magnetic field in the higher atmospheric layers
is mainly indirect. This lack of information hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution
and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is
designed to measure the large-scale magnetic field in the corona with
an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter
based on a 30 cm telescope that combines high throughput in the
extreme UV with polarimetry to connect the magnetic measurements
of the other two instruments. Placed in a near-Earth orbit, the data
downlink would be maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-based
observatories. This mission to measure the magnetic field will finally
unlock the driver of the dynamics in the outer solar atmosphere and
thereby will greatly advance our understanding of the Sun and the
heliosphere.
Title: Radio evidence for a shock wave reflected by a coronal hole
Authors: Mancuso, S.; Bemporad, A.; Frassati, F.; Barghini, D.;
Giordano, S.; Telloni, D.; Taricco, C.
Bibcode: 2021A&A...651L..14M
Altcode: 2021arXiv210705931M
We report the first unambiguous observational evidence in the radio
range of the reflection of a coronal shock wave at the boundary of a
coronal hole. The event occurred above an active region located at
the northwest limb of the Sun and was characterized by an eruptive
prominence and an extreme-ultraviolet wave steepening into a shock. The
EUV observations acquired by the Atmospheric Imaging Assembly instrument
on board the Solar Dynamics Observatory and the Extreme Ultraviolet
Imager instrument on board the Solar TErrestrial RElations Observatory
were used to track the development of the EUV front in the inner
corona. Metric type II radio emission, a distinguishing feature of shock
waves propagating in the inner corona, was simultaneously recorded by
ground-based radio spectrometers. The radio dynamic spectra displayed
an unusual reversal of the type II emission lanes, together with type
III-like herringbone emission, indicating shock-accelerated electron
beams. Combined analysis of imaging data from the two space-based
EUV instruments and the Nançay Radioheliograph evidences that the
reverse-drifting type II emission was produced at the intersection
of the shock front, reflected at a coronal hole boundary, with
an intervening low-Alfvén-speed region characterized by an open
field configuration. We also provide an outstanding data-driven
reconstruction of the spatiotemporal evolution in the inner corona of
the shock-accelerated electron beams produced by the reflected shock.
Title: Laboratory testbed for the calibration and the validation of
the shadow position sensor subsystem of the PROBA3 ESA mission
Authors: Loreggia, Davide; Zangrilli, Luca; Capobianco, Gerardo;
Massone, Giuseppe; Belluso, Massimiliano; Fineschi, Silvano; Amadori,
Francesco; Noce, Vladimiro; Bemporad, Alessandro; Casti, Marta;
Nicolini, Gianalfredo; Landini, Federico; Pancrazzi, Maurizio;
Romoli, Marco
Bibcode: 2021SPIE11852E..6QL
Altcode:
The PROBA3 mission of the European Space Agency is the first formation
flying (FF) mission that will be flown in high elliptic geocentric
orbit aiming at verifying and validating different metrology control
systems and algorithms in order to realize and maintain the formation
of two independent spacecraft, in total autonomy. The final target
accuracy for the relative and absolute alignment of the two satellites
is of about 2mm over an inter satellite distance of 144.3m. During
the FF, the two spacecraft will realize a giant coronagraph with
the external occulter on one payload and the telescope on the other
one. The Sun Corona observation will be the scientific tool for the
FF validation. Between the different metrology systems that will be
tested, the Shadow Position Sensor (SPS) is the most challenging one,
aiming at returning the relative and absolute position of the formation
with the finest accuracy: 0.5mm out of the guidance and navigation and
control loop and 2mm within the loop. The mission program is now in the
Phase D with the realization and the testing of the flight model. Due to
the high expected performance, a fine calibration of the SPS subsystem
is mandatory. In this paper, we discuss the radiometric and spectral
calibration plan, the algorithm validation procedure, and the laboratory
test-bed realized to reproduce the in-flight observation conditions
of the SPS by using a set of calibrated LED and a mechanical set-up
equivalent to the SPS system. Preliminary results are also reviewed.
Title: Metrology on-board PROBA-3: The shadow position sensors
subsystem
Authors: Noce, Vladimiro; Loreggia, Davide; Capobianco, Gerardo;
Fineschi, Silvano; Bemporad, Alessandro; Casti, Marta; Buckley, Steven;
Romoli, Marco; Focardi, Mauro; Belluso, Massimiliano; Thizy, Cédric;
Hermans, Aline; Galano, Damien; Versluys, Jorg
Bibcode: 2021AdSpR..67.3807N
Altcode:
PROBA-3 is an ESA mission aimed at the demonstration of formation flying
performance of two satellites that will form a giant coronagraph in
space. The first spacecraft will host a telescope imaging the solar
corona in visible light, while the second, the external occulter,
will produce an artificial eclipse. This instrument is named ASPIICS
(Association of Spacecraft for Polarimetric and Imaging Investigation of
the Corona of the Sun). To accomplish the payload's scientific tasks,
PROBA-3 will ensure sub-millimeter reciprocal positioning of its two
satellites using closed-loop on-board metrology. Several metrology
systems will be used and the Shadow Position Sensor (SPS) subsystem
senses the penumbra around the instrument aperture and returns the
3-D displacement of the coronagraph satellite, with respect to its
nominal position, by running a dedicated algorithm. In this paper,
we describe how the SPS works and the choices made to accomplish the
mission objectives.
Title: In-flight optical performance assessment for the Metis solar
coronagraph
Authors: Da Deppo, Vania; Chioetto, Paolo; Andretta, Vincenzo; Casini,
Chiara; Frassetto, Fabio; Slemer, Alessandra; Zuppella, Paola; Romoli,
Marco; Fineschi, Silvano; Heinzel, Petr; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca;
Bemporad, Alessandro; Casti, Marta; Fabi, Michele; Grimani, Catia;
Heerlein, Klaus; Jerse, Giovanna; Landini, Federico; Liberatore,
Alessandro; Magli, Enrico; Melich, Radek; Pancrazzi, Maurizio; Pelizzo,
Maria-G.; Romano, Paolo; Sasso, Clementina; Straus, Thomas; Susino,
Roberto; Uslenghi, Michela; Volpicelli, Cosimo Antonio
Bibcode: 2021SPIE11852E..10D
Altcode:
Metis is a multi-wavelength coronagraph onboard the European Space
Agency (ESA) Solar Orbiter mission. The instrument features an
innovative instrument design conceived for simultaneously imaging the
Sun's corona in the visible and ultraviolet range. The Metis visible
channel employs broad-band, polarized imaging of the visible K-corona,
while the UV one uses narrow-band imaging at the HI Ly , i.e. 121.6
nm. During the commissioning different acquisitions and activities,
performed with both the Metis channels, have been carried out with the
aim to check the functioning and the performance of the instrument. In
particular, specific observations of stars have been devised to assess
the optical alignment of the telescope and to derive the instrument
optical parameters such as focal length, PSF and possibly check the
optical distortion and the vignetting function. In this paper, the
preliminary results obtained for the PSF of both channels and the
determination of the scale for the visible channel will be described
and discussed. The in-flight obtained data will be compared to those
obtained on-ground during the calibration campaign.
Title: PROBA-3 mission and the Shadow Position Sensors: Metrology
measurement concept and budget
Authors: Loreggia, Davide; Fineschi, Silvano; Capobianco,
Gerardo; Bemporad, Alessandro; Casti, Marta; Landini, Federico;
Nicolini, Gianalfredo; Zangrilli, Luca; Massone, Giuseppe; Noce,
Vladimiro; Romoli, Marco; Terenzi, Luca; Morgante, Gianluca; Belluso,
Massimiliano; Thizy, Cedric; Galy, Camille; Hermans, Aline; Franco,
Pierre; Pirard, Ariane; Rossi, Laurence; Buckley, Steve; Spillane,
Raymond; O'Shea, Martin; Galano, Damien; Versluys, Jorg; Hernan, Ken;
Accatino, Luciano
Bibcode: 2021AdSpR..67.3793L
Altcode:
PROBA-3 is a space mission of the European Space Agency that will test,
and validate metrology and control systems for autonomous formation
flying of two independent satellites. PROBA-3 will operate in a High
Elliptic Orbit and when approaching the apogee at 6·104 Km,
the two spacecraft will align to realize a giant externally occulted
coronagraph named ASPIICS, with the telescope on one satellite and
the external occulter on the other one, at inter-satellite distance
of 144.3 m. The formation will be maintained over 6 hrs across the
apogee transit and during this time different validation operations
will be performed to confirm the effectiveness of the formation flying
metrology concept, the metrology control systems and algorithms, and
the spacecraft manoeuvring. The observation of the Sun's Corona in the
field of view [1.08;3.0]RSun will represent the scientific
tool to confirm the formation flying alignment. In this paper, we review
the mission concept and we describe the Shadow Position Sensors (SPS),
one of the metrological systems designed to provide high accuracy
(sub-millimetre level) absolute and relative alignment measurement
of the formation flying. The metrology algorithm developed to convert
the SPS measurements in lateral and longitudinal movement estimation
is also described and the measurement budget summarized.
Title: On-ground flat-field calibration of the Metis coronagraph
onboard the Solar Orbiter ESA mission
Authors: Casini, C.; Da Deppo, V.; Zuppella, P.; Chioetto, P.; Slemer,
A.; Frassetto, F.; Romoli, M.; Landini, F.; Pancrazzi, M.; Andretta,
V.; De Leo, Y.; Bemporad, A.; Fabi, M.; Fineschi, S.; Frassati, F.;
Grimani, C.; Jerse, G.; Heerlein, K.; Liberatore, A.; Magli, E.;
Naletto, G.; Nicolini, G.; Pelizzo, M. G.; Romano, P.; Sasso, C.;
Spadaro, D.; Stangalini, M.; Straus, T.; Susino, R.; Teriaca, L.;
Uslenghi, M.; Casti, M.; Heinzel, P.; Volpicelli, A.
Bibcode: 2021SPIE11852E..5BC
Altcode:
Solar Orbiter, launched on February 9th 2020, is an
ESA/NASA mission conceived to study the Sun. This work presents
the embedded Metis coronagraph and its on-ground calibration in the
580-640 nm wavelength range using a flat field panel. It provides
a uniform illumination to evaluate the response of each pixel of
the detector; and to characterize the Field of View (FoV) of the
coronagraph. Different images with different exposure times were
acquired during the on-ground calibration campaign. They were analyzed
to verify the linearity response of the instrument and the requirements
for the FoV: the maximum area of the sky that Metis can acquire.
Title: Formation flying performances simulator for the shadow position
sensors of the ESA PROBA-3 mission
Authors: Capobianco, Gerardo; Amadori, Francesco; Fineschi, Silvano;
Bemporad, Alessandro; Casti, Marta; Loreggia, Davide; Noce, Vladimiro;
Pancrazzi, Maurizio; Landini, Federico; Thizy, Cedric; Rougeot,
Raphael; Galano, Damien; Versluys, Jorg
Bibcode: 2021SPIE11852E..6PC
Altcode:
PROBA-3 (PRoject for OnBoard Autonomy) is an ESA mission to be launched
on beginning of 2023 where a spacecraft is used as an external occulter
(OSC-Occulter Spacecraft), to create an artificial solar eclipse as
observed by a second spacecraft, the coronagraph (CSC-Coronagraph
Spacecraft). The two spacecrafts (SCs) will orbit around the Earth,
with a highly elliptic orbit (HEO), with the perigee at 600 km, the
apogee at about 60530 km and an eccentricity of ≍ 0.81. The orbital
period is of 19.7 hours and the precise formation flight (within 1
mm) will be maintained for about 6 hours over the apogee, in order
to guarantee the observation of the solar corona with the required
spatial resolution. The relative alignment of the two spacecrafts is
obtained by combining information from several subsystems. One of
the most accurate subsystems is the Shadow Position Sensors (SPS),
composed of eight photo-multipliers installed around the entrance
pupil of the CSC. The SPS will monitor the penumbra generated by the
occulter spacecraft, whose intensity will change according to the
relative position of the two satellites. A dedicated algorithm has
been developed to retrieve the displacement of the spacecrafts from
the measurements of the SPS. Several tests are required in order to
evaluate the robustness of the algorithm and its performances/results
for different possible configurations. A software simulator has been
developed for this purpose. The simulator includes the possibility
to generate synthetic 2-D penumbra profile maps or analyze measured
profiles and run different versions of the retrieving algorithms,
including the "on-board" version. In order to import the "as-built"
algorithms, the software is coded using Matlab. The main aspects of the
simulator, such as the results of the simulations, with the inclusion
of some specific case studies, will be reported and discussed in
this paper.
Title: In-flight calibration of Metis coronagraph on board of
Solar Orbiter
Authors: Liberatore, A.; Fineschi, S.; Casti, M.; Capobianco, G.;
Romoli, M.; Andretta, V.; Bemporad, A.; Da Deppo, V.; De Leo, Y.; Fabi,
M.; Frassetto, F.; Grimani, C.; Heerlein, K.; Heinzel, P.; Jerse,
G.; Landini, F.; Magli, E.; Naletto, G.; Nicolini, G.; Pancrazzi,
M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Slemer, A.; Spadaro, D.;
Straus, T.; Susino, R.; Teriaca, L.; Uslenghi, M.; Volpicelli, C. A.;
Zuppella, P.
Bibcode: 2021SPIE11852E..48L
Altcode:
Metis coronagraph is one of the remote-sensing instruments of the Solar
Orbiter mission launched at the begin of 2020. The mission profile will
allow for the first time the remote-sensing observation of the Sun
from a very close distance and increasing the latitude with respect
to the ecliptic plane. In particular, Metis is aimed at the overall
characterization and study of the solar corona and solar wind. Metis
instrument acquires images of the solar corona in two different
wavelengths simultaneously; ultraviolet (UV) and visible-light (VL). The
VL channel includes a polarimeter with an electro-optically modulating
Liquid Crystal Variable Retarder (LCVR) to measure the linearly
polarized brighness pB) of the K-corona. This paper presents part of
the in-flight calibration results for both wavelength channels together
with a comparison with on-ground calibrations. The orientation of the
K-corona linear polarization was used for the in-flight calibration
of the Metis polarimeter. This paper describes the correction of the
on-ground VL vignetting function after the in-flight adjustment of
the internal occulter. The same vignetting function was adaptated to
the UV channel.
Title: Challenges during Metis-Solar Orbiter commissioning phase
Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro;
Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi,
Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel,
Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro;
Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi,
Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina;
Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas;
Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo
Antonio; Zupella, Paola
Bibcode: 2021SPIE11852E..5AR
Altcode:
Metis is the visible light and UV light imaging coronagraph on board
the ESA-NASA mission Solar Orbiter that has been launched February 10th,
2020, from Cape Canaveral. Scope of the mission is to study the Sun up
close, taking high-resolution images of the Sun's poles for the first
time, and understanding the Sun-Earth connection. Metis coronagraph
will image the solar corona in the linearly polarized broadband visible
radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at
Solar Orbiter perihelion, providing a diagnostics, with unprecedented
temporal coverage and spatial resolution, of the structures and dynamics
of the full corona. Solar Orbiter commissioning phase big challenge was
Covid-19 social distancing phase that affected the way commissioning
of a spacecraft and its payload is typically done. Metis coronagraph
on-board Solar Orbiter had its additional challenges: to wake up and
check the performance of the optical, electrical and thermal subsystems,
most of them unchecked since Metis delivery to spacecraft prime, Airbus,
in May 2017. The roadmap to the fully commissioned coronagraph is here
described throughout the steps from the software functional test,
the switch on of the detectors of the two channels, UV and visible,
to the optimization of the occulting system and the characterization
of the instrumental stray light, one of the most challenging features
in a coronagraph.
Title: First-light Science Observations of the Metis Solar Coronagraph
Authors: Fineschi, S.; Romoli, M.; Andretta, V.; Bemporad, A.;
Capobianco, G.; Casti, M.; Da Deppo, V.; De Leo, Y.; Fabi, M.;
Frassetto, F.
Bibcode: 2021SPIE11852E..11F
Altcode:
Metis coronagraph is one of the remote-sensing instruments of the Solar
Orbiter mission launched in February 2020. The mission profile will
allow for the first time the remote-sensing observation of the Sun from
as close as 0.28 AU and from ecliptic latitudes as high as 30?. Metis,
in particular, is aimed at the study and the overall characterization
of the solar corona and solar wind. This instrument is an innovative
inverted-occultation coronagraph that will image the solar corona for
the first time simultaneously in two different wavelength band-passes:
in the linearly-polarized visible-light (VL), between 580 and 640 nm,
and in the ultraviolet (UV) Lyman-a line of hydrogen, HI at 121.6 nm
by combining in the same telescope UV interference mirror coatings
(Al/MgF2) and spectral bandpass filters. The visible channel includes
a broad-band polarimeter to observe the linearly polarized component of
the K corona. These measurements will allow a complete characterization
of the physical parameters, such as density and outflow speed, of
the two major plasma components of the corona and the solar wind:
electrons (protons) and hydrogen. After a period of commissioning, by
the summer of 2020, Metis will have performed the First-light Science
Observations during the "Remote-Sensing Check-out Window" (RSCW) that
is a telemetry contact period, specifically allocated before entering
the operational phase at the end of 2021. This presentation will report
the first-light science observations of Metis represented by the UV
and polarized VL images of the corona. The calibration results from
the commissioning will be used for the correction of the instrumental
effects. The resulting first-light maps of the coronal electron and
hydrogen distributions will be presented.
Title: The Solar Wind
Authors: Rouillard, Alexis P.; Viall, Nicholeen; Pierrard, Viviane;
Vocks, Christian; Matteini, Lorenzo; Alexandrova, Olga; Higginson,
Aleida K.; Lavraud, Benoit; Lavarra, Michael; Wu, Yihong; Pinto, Rui;
Bemporad, Alessandro; Sanchez-Diaz, Eduardo
Bibcode: 2021GMS...258....1R
Altcode:
No abstract at ADS
Title: Evolution of solar wind flows from the inner corona to 1 AU:
constraints provided by SOHO UVCS and SWAN data
Authors: Bemporad, Alessandro; Katushkina, Olga; Izmodenov, Vladislav;
Koutroumpa, Dimitra; Quemerais, Eric
Bibcode: 2021EGUGA..2311921B
Altcode:
The Sun modulates with the solar wind flow the shape of the whole
Heliosphere interacting with the surrounding interstellar medium. Recent
results from IBEX and INCA experiments, as well as recent measurements
from Voyager 1 and 2, demonstrated that this interaction is much
more complex and subject to temporal and heliolatitudinal variations
than previously thought. These variations could be also related
with the evolution of solar wind during its journey through the
Heliosphere. Hence, understanding how the solar wind evolves from its
acceleration region in the inner corona to the Heliospheric boundaries
is very important.In this work, SWAN Lyman-α full-sky observations from
SOHO are combined for the very first time with measurements acquired
in the inner corona by SOHO UVCS and LASCO instruments, to trace the
solar wind expansion from the Sun to 1 AU. The solar wind mass flux
in the inner corona was derived over one full solar rotation period
in 1997, based on LASCO polarized brightness measurements, and on
the Doppler dimming technique applied to UVCS Lyman-α emission from
neutral H coronal atoms due to resonant scattering of chromospheric
radiation. On the other hand, the SWAN Lyman-α emission (due to
back-scattering from neutral H atoms in the interstellar medium)
was analyzed based on numerical models of the interstellar hydrogen
distribution in the heliosphere and the radiation transfer. The SWAN
full-sky Lyman-α intensity maps are used for solving of the inverse
problem and deriving of the solar wind mass flux at 1 AU from the Sun
as a function of heliolatitude. First results from this comparison for
a chosen time period in 1997 are described here, and possible future
applications for Solar Orbiter data are discussed.
Title: Three-dimensional reconstruction of an expanding shock
associated with a Solar particle event
Authors: Frassati, Federica; Laurenza, Monica; Bemporad, Alessandro;
West, Matthew J.; Mancuso, Salvatore; Susino, Roberto; Alberti,
Tommaso; Romano, Paolo
Bibcode: 2021EGUGA..2312154F
Altcode:
On 2013 June 21st an eruption occurred in the active region NOAA 1177
(14S73E), giving rise to a M2.9 class flare starting at 02:30 UT,
a fast partial halo coronal mass ejection (CME), and a type II radio
burst. The concomitant emission of solar energetic particles (SEPs)
produced a significant increase in the proton fluxes measured by LET
and HET aboard STEREO-B. By using stereoscopic observations in extreme
ultra violet (EUV) and white light (WL) spectral intervals, we performed
a 3D reconstruction of the expanding front by processing SDO/AIA,
STEREO/EUVI, COR1 and COR2, and SOHO/LASCO data assuming a spheroidal
model. By using the 3D reconstruction, we estimated the temporal
evolution of θBn, i.e., the angle between the normal to the expanding
front and the coronal magnetic field computed by the Potential-Field
Source-Surface (PFSS) approximation, within 2.5 Rʘ. The front of
the CMEwas found to be quasi-parallel to the magnetic field almost
everywhere. Above 2.5 Rʘ, where the front was identified as a shock,
we projected the 3D expanding surface reconstructed for different times
on the ecliptic plane and we calculated the θBn between the normal
to the front and Parker spiral arms. In this case the shock was almost
perpendicular to the magnetic field (quasi-parallel shock). During the
expansion the region located between the nose and the eastern flank
of the shock was magnetically connected with ST-B in agreement with
the significant SEP flux measured on-board this spacecraft. While the
shock was only marginally connected with ST-A and GOES-15. The SEP
release time was estimated to be 10 minutes after the Type II onset,
when the shock front was already above 2.5 Rʘ with a quasi-parallel
configuration. Our results are discussed in the framework of the shock
acceleration scenario, even if quasi-parallel shocks are expected to
have a reduced acceleration efficiency.
Title: Possible advantages of a twin spacecraft Heliospheric mission
at the Sun-Earth Lagrangian points L4 and L5
Authors: Bemporad, A.
Bibcode: 2021FrASS...8...11B
Altcode:
After the launch of STEREO twin spacecraft, and most recently of
Solar Orbiter and Parker Solar Probe spacecraft, the next mission
that will explore Sun-Earth interactions and how the Sun modulates
the Heliosphere will be the "Lagrange" mission, which will consist of
two satellites placed in orbit around L1 and L5 Sun-Earth Lagrangian
points. Despite the significant novelties that will be provided by
such a double vantage point, there will be also missing information,
that are briefly discussed here. For future heliospheric missions, an
alternative advantageous approach that has not been considered so far
would be to place two twin spacecraft not in L1 and L5, but in L4 and
L5 Lagrangian points. If these two spacecraft will be equipped with
in situ instruments, and also remote sensing instruments measuring
not only photospheric but also coronal magnetic fields, significant
advancing will be possible. In particular, data provided by such a
twin mission will allow to follow the evolution of magnetic fields
from inside the sun (with stereoscopic helioseismology), to its surface
(with classical photospheric magnetometers), and its atmosphere (with
spectro-polarimeters); this will provide a tremendous improvement in
our physical understanding of solar activity. Moreover, the L4-L5
twin satellites will take different interesting configurations,
such as relative quadrature, and quasi-quadrature with the Earth,
providing a baseline for monitoring the Sun-to-Earth propagation of
solar disturbances.
Title: Reconstruction of the Parker spiral with the Reverse In situ
data and MHD APproach - RIMAP
Authors: Biondo, Ruggero; Bemporad, Alessandro; Mignone, Andrea;
Reale, Fabio
Bibcode: 2021JSWSC..11....7B
Altcode:
The reconstruction of plasma parameters in the interplanetary medium
is very important to understand the interplanetary propagation of solar
eruptions and for Space Weather application purposes. Because only a few
spacecraft are measuring in situ these parameters, reconstructions are
currently performed by running complex numerical Magneto-hydrodynamic
(MHD) simulations starting from remote sensing observations of the
Sun. Current models apply full 3D MHD simulations of the corona
or extrapolations of photospheric magnetic fields combined with
semi-empirical relationships to derive the plasma parameters on
a sphere centered on the Sun (inner boundary). The plasma is then
propagated in the interplanetary medium up to the Earth's orbit and
beyond. Nevertheless, this approach requires significant theoretical
and computational efforts, and the results are only in partial
agreement with the in situ observations. In this paper we describe a
new approach to this problem called RIMAP - Reverse In situ data and
MHD APproach. The plasma parameters in the inner boundary at 0.1 AU
are derived directly from the in situ measurements acquired at 1 AU,
by applying a back reconstruction technique to remap them into the
inner heliosphere. This remapping is done by using the Weber and Davies
solar wind theoretical model to reconstruct the wind flowlines. The
plasma is then re-propagated outward from 0.1 AU by running a MHD
numerical simulation based on the PLUTO code. The interplanetary spiral
reconstructions obtained with RIMAP are not only in a much better
agreement with the in situ observations, but are also including many
more small-scale longitudinal features in the plasma parameters that
are not reproduced with the approaches developed so far.
Title: Magnetic Imaging of the Outer Solar Atmosphere (MImOSA):
Unlocking the driver of the dynamics in the upper solar atmosphere
Authors: Peter, H.; Alsina Ballester, E.; Andretta, V.; Auchere, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; del Pino Aleman, T.; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Stepan, J.; Teriaca, L.; Trujillo Bueno, J.
Bibcode: 2021arXiv210101566P
Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability
of planets orbiting these host stars. The lack of information on the
magnetic field in the higher atmospheric layers hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution and high
sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to
measure the large-scale magnetic field in the corona with an aperture
of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
cm telescope that combines high throughput in the extreme UV with
polarimetry to connect the magnetic measurements of the other two
instruments. This mission to measure the magnetic field will unlock
the driver of the dynamics in the outer solar atmosphere and thereby
greatly advance our understanding of the Sun and the heliosphere.
Title: SWELTO -- Space WEather Laboratory in Turin Observatory
Authors: Bemporad, A.; Abbo, L.; Barghini, D.; Benna, C.; Biondo,
R.; Bonino, D.; Capobianco, G.; Carella, F.; Cora, A.; Fineschi, S.;
Frassati, F.; Gardiol, D.; Giordano, S.; Liberatore, A.; Mancuso, S.;
Mignone, A.; Rasetti, S.; Reale, F.; Riva, A.; Salvati, F.; Susino,
R.; Volpicelli, A.; Zangrilli, L.
Bibcode: 2021arXiv210107037B
Altcode:
SWELTO -- Space WEather Laboratory in Turin Observatory is a
conceptual framework where new ideas for the analysis of space-based
and ground-based data are developed and tested. The input data are
(but not limited to) remote sensing observations (EUV images of the
solar disk, Visible Light coronagraphic images, radio dynamic spectra,
etc...), in situ plasma measurements (interplanetary plasma density,
velocity, magnetic field, etc...), as well as measurements acquired
by local sensors and detectors (radio antenna, fluxgate magnetometer,
full-sky cameras, located in OATo). The output products are automatic
identification, tracking, and monitoring of solar stationary and dynamic
features near the Sun (coronal holes, active regions, coronal mass
ejections, etc...), and in the interplanetary medium (shocks, plasmoids,
corotating interaction regions, etc...), as well as reconstructions of
the interplanetary medium where solar disturbances may propagate from
the Sun to the Earth and beyond. These are based both on empirical
models and numerical MHD simulations. The aim of SWELTO is not only
to test new data analysis methods for future application for Space
Weather monitoring and prediction purposes, but also to procure,
test and deploy new ground-based instrumentation to monitor the
ionospheric and geomagnetic responses to solar activity. Moreover,
people involved in SWELTO are active in outreach to disseminate the
topics related with Space Weather to students and the general public.
Title: Current state and perspectives of Space Weather science
in Italy
Authors: Plainaki, Christina; Antonucci, Marco; Bemporad, Alessandro;
Berrilli, Francesco; Bertucci, Bruna; Castronuovo, Marco; De Michelis,
Paola; Giardino, Marco; Iuppa, Roberto; Laurenza, Monica; Marcucci,
Federica; Messerotti, Mauro; Narici, Livio; Negri, Barbara; Nozzoli,
Francesco; Orsini, Stefano; Romano, Vincenzo; Cavallini, Enrico;
Polenta, Gianluca; Ippolito, Alessandro
Bibcode: 2020JSWSC..10....6P
Altcode:
Italian teams have been involved many times in Space Weather
observational campaigns from space and from the ground, contributing
in the advancing of our knowledge on the properties and evolution
of the related phenomena. Numerous Space Weather forecasting and
now-casting modeling efforts have resulted in a remarkable add-on to
the overall progress in the field, at both national and international
level. The Italian Space Agency has participated several times in
space missions with science objectives related to Space Weather;
indeed, an important field for the Italian scientific and industrial
communities interested in Heliophysics and Space Weather, is the
development of new instrumentation for future space missions. In
this paper, we present a brief state-of-the-art in Space Weather
science in Italy and we discuss some ideas on a long-term plan for the
support of future scientific research in the related disciplines. In
the context of the current roadmap, the Italian Space Agency aims to
assess the possibility to develop a national scientific Space Weather
data centre to encourage synergies between different science teams
with interest in the field and to motivate innovation and new mission
concept development. Alongside with the proposed recommendations, we
also discuss how the Italian expertise could complement international
efforts in a wider international Space Weather context.
Title: Italian SWA-Solar Orbiter Working Group on "Particle
Energization"
Authors: Perri, S.; Bemporad, A.; Benella, S.; Bruno, R.; Catapano, F.;
D'Amicis, R.; De Marco, R.; Frassati, F.; Grimani, C.; Ippolito, A.;
Jagarlamudi, V. K.; Laurenza, M.; Lepreti, F.; Nisticò, G.; Pecora,
F.; Perrone, D.; Pezzi, O.; Plainaki, C.; Prete, G.; Pucci, F.; Retino,
A.; Servidio, S.; Susino, R.; Trotta, D.; Valentini, F.; Zimbardo, G.
Bibcode: 2020AGUFMSH0360017P
Altcode:
One of the outstanding scientific questions in space physics is how
charged particles are accelerated up to supra-thermal energies and
how they are transported through the inner heliosphere. Such problems
match some of the scientific objectives of the Solar Orbiter Science
Activity Plan and represent the main scientific cases discussed in the
Italian SWA-Solar Orbiter Working Group (WG) on "Particle Energization"
(https://sites.google.com/view/italian-solar-orbiter-swa/research-interests/particle-energization?authuser=0).
The WG started its activities on May 2020 and gathers experts of
in-situ observations, remote sensing, and numerical simulations. This
variety of expertises is fundamental for reaching the science
objectives. Indeed, candidates for particle acceleration are shocks
driven by eruptive phenomena in the solar corona as the coronal mass
ejections (CMEs). Thanks to the joint combination between in-situ
(as MAG, SWA, EPD) and remote sensing (EUI, METIS) instruments on
board Solar Orbiter and to its vicinity to the Sun, we will have
the opportunity to study, with unprecedented precision, the onset
of CMEs and the properties of the induced shocks propagating in the
interplanetary medium. Thus, parameters as the sonic Mach number,
the compression ratio and the shock geometry (both when shocks form in
the corona and then propagate in the interplanetary space) will give a
quantitative estimation of the shocks evolution and their capability to
accelerate particles. Then, the investigation of the phenomena involved
in the acceleration and propagation of solar energetic particles (SEPs)
that were difficult to resolve from prior observations, will be carried
out. Further, being close to the source of acceleration, it will be
possible to investigate the properties of the local energetic particle
"seed" population. In this abstract we would like to present the
ongoing activity of the Italian SWA WG on "Particle Energization",
pointing out the physical problems discussed during the last months,
with particular focus on the possible analysis of Solar Orbiter
data (both in-situ and remote sensing) in the framework of particle
energization, which we propose to carry out once the data will be
available to the scientific community.
Title: Studying CMEs with Metis on-board Solar Orbiter: constraints
from synthetic data analysis
Authors: Giordano, S.; Pagano, P.; Bemporad, A.; Ying, B.; Feng, L.
Bibcode: 2020AGUFMSH0280001G
Altcode:
The Metis instrument on-board Solar Orbiter will provide the first
ever multi-channel coronagraphic images of Coronal Mass Ejections
(CMEs). This unprecedented combination of visible-light (VL) and UV HI
Lyman-α images will allow to investigate the thermodynamic evolution
of CMEs in their expansion and propagation phase, that is crucially
associated with plasma heating and cooling processes. However, the UV
HI Lyman-α emissivity of the coronal plasma depends on its density,
temperature, outflow velocity, and scattering of chromospheric
radiation, making the inversion of future images a complex and
undetermined problem. To disentangle the problem, synergies between
different analysis tools are required, where VL images will play
a pivotal role. A few years ago, we started an effort to develop a
complete set of diagnostic techniques and our main results are presented
here. In our approach, we heavily relied on realistic 3D MHD simulations
of CMEs and used these to derive VL and UV 2D synthetic images. The
images are then analyzed and inverted using several techniques that
are tested and verified by comparing the diagnostic with the MHD
evolution. This effort provides a pathway to accurate estimates of
plasma parameters with Metis and the errors associated with these
measures. In the latest segment of this work, we are assessing the
impact of non-equilibrium ionization effect on Lyman-α emission from
the solar corona and, crucially, how much the ionization equilibrium
approximation affects the diagnostic. These results will impact the
analysis of future data acquired by multi-channel VL and UV Lyman-α
coronagraphs such as Metis on-board Solar Orbiter, but also LST on
ASO-S mission, and any other future VL+UV coronagraph.
Title: Coronal Electron Densities Derived with Images Acquired during
the 2017 August 21 Total Solar Eclipse
Authors: Bemporad, A.
Bibcode: 2020ApJ...904..178B
Altcode: 2020arXiv201015005B
The total solar eclipse of 2017 August 21 was observed with a digital
single lens reflex (DSLR) camera equipped with a linear polarizing
filter. A method was developed to combine images acquired with 15
different exposure times (from 1/4000 s to 4 s), identifying in each
pixel the best interval of detector linearity. The resulting mosaic
image of the solar corona extends up to more than 5 solar radii, with
a projected pixel size of 3.7 arcsec/pixel and an effective image
resolution of 10"2, as determined with visible α-Leo and ν-Leo
stars. Image analysis shows that in the inner corona the intensity
gradients are so steep that nearby pixels show a relative intensity
difference of up to ∼10%; this implies that care must be taken when
analyzing single exposures acquired with polarization cameras. Images
acquired with two different orientations of the polarizer have been
analyzed to derive the degree of linear polarization and the polarized
brightness pB in the solar corona. After intercalibration with pB
measurements by the K-Cor instrument on Mauna Loa Solar Observatory
(MLSO), the data analysis provided the 2D coronal electron density
distribution from 1.1 up to ∼3 solar radii. The absolute radiometric
calibration was also performed with the full Sun image and with
magnitudes of visible stars. The resulting absolute calibrations show a
disagreement by a factor of ∼2 with respect to MLSO; interestingly,
this is the same disagreement recently found with eclipse predictions
provided by MHD numerical simulations.
Title: Metis - Solar Orbiter Topical Team on "Modelling of CME
propagation/evolution in corona and solar wind in connection with
Space Weather"
Authors: Bemporad, A.; Banerjee, D.; Berlicki, A.; Biondo, R.; Boe,
B.; Calchetti, D.; Capuano, G.; De Leo, Y.; Del Moro, D.; Feng, L.;
Foldes, R.; Frassati, F.; Frazin, R. A.; Giovannelli, L.; Giunta,
A. S.; Heinzel, P.; Ippolito, A.; Janvier, M.; Jerse, G.; Kilpua,
K. E. J.; Laurenza, M.; Lloveras, D.; Magdalenic, J.; Mancuso, S.;
Messerotti, M.; Mierla, M.; Nandy, D.; Napoletano, G.; Nuevo, F.;
Pagano, P.; Pinto, R.; Plainaki, C.; Reale, F.; Romoli, M.; Rodriguez,
L.; Slemer, A.; Spadaro, D.; Susino, R.; Stangalini, M.; Vainio,
R. O.; Valori, G.; Vásquez, A. M.; West, M. J.
Bibcode: 2020AGUFMSH0360027B
Altcode:
Despite the current availability of multi-spacecraft observations of
Coronal Mass Ejections (CMEs) and their interplanetary counterpart
(ICMEs), at present we still don't understand which physical phenomena
are driving their expansion and propagation phases. This also limits
our understanding on how CMEs (observed with remote sensing data)
become ICMEs (observed in situ), how they interact with the background
solar wind, and how their final geo-effectiveness can be modified
during their interplanetary evolution. Such problems match some of
the scientific objectives of the Solar Orbiter Science Activity Plan
and of the Metis coronagraph. Thanks to its multi-channel capability,
Metis (acquiring images in the visible light and at the same time in
the UV HI Lyman-alpha emission) will really provide an unprecedented
view of CMEs and in particular of their thermodynamic evolution. At
closest approaches to the Sun (in the nominal mission), Metis will
acquire high spatial resolution and/or temporal cadence multi-channel
images of CMEs. Farther from the Sun, Metis will shed light on the
early Interplanetary propagation of CMEs. Later on (in the extended
mission) Metis will observe for the first time the CME/ICME propagation
out-of-ecliptic. These novelties will be combined with the unique
vantage point that will be offered by the Solar Orbiter spacecraft,
and supported with valuable data acquired by other on-board remote
sensing (e.g. SPICE, EUI, SoloHI) and in situ (e.g. EPD, MAG,
SWA, RPW) instruments. In this contribution we present the ongoing
activities of the Metis Topical Team on "CME/ICME propagation", (http://metis.oato.inaf.it/topical_teams.html),
an international working group recently established and gathering
scientists from different countries, experts of both in-situ and remote
sensing observations, as well as numerical simulations, and we summarize
the main science objectives discussed during the last months.
Title: Coordination within the remote sensing payload on the Solar
Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
Bibcode: 2020A&A...642A...6A
Altcode:
Context. To meet the scientific objectives of the mission, the Solar
Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
(RS) instruments designed for joint operations with inter-instrument
communication capabilities. Indeed, previous missions have shown that
the Sun (imaged by the RS instruments) and the heliosphere (mainly
sampled by the IS instruments) should be considered as an integrated
system rather than separate entities. Many of the advances expected
from Solar Orbiter rely on this synergistic approach between IS and
RS measurements.
Aims: Many aspects of hardware development,
integration, testing, and operations are common to two or more
RS instruments. In this paper, we describe the coordination effort
initiated from the early mission phases by the Remote Sensing Working
Group. We review the scientific goals and challenges, and give an
overview of the technical solutions devised to successfully operate
these instruments together.
Methods: A major constraint for the
RS instruments is the limited telemetry (TM) bandwidth of the Solar
Orbiter deep-space mission compared to missions in Earth orbit. Hence,
many of the strategies developed to maximise the scientific return from
these instruments revolve around the optimisation of TM usage, relying
for example on onboard autonomy for data processing, compression,
and selection for downlink. The planning process itself has been
optimised to alleviate the dynamic nature of the targets, and an
inter-instrument communication scheme has been implemented which can
be used to autonomously alter the observing modes. We also outline the
plans for in-flight cross-calibration, which will be essential to the
joint data reduction and analysis.
Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.
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: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
A. N.
Bibcode: 2020A&A...642A...2R
Altcode:
Context. The Solar Orbiter spacecraft will be equipped with a wide
range of remote-sensing (RS) and in situ (IS) instruments to record
novel and unprecedented measurements of the solar atmosphere and
the inner heliosphere. To take full advantage of these new datasets,
tools and techniques must be developed to ease multi-instrument and
multi-spacecraft studies. In particular the currently inaccessible
low solar corona below two solar radii can only be observed
remotely. Furthermore techniques must be used to retrieve coronal
plasma properties in time and in three dimensional (3D) space. Solar
Orbiter will run complex observation campaigns that provide interesting
opportunities to maximise the likelihood of linking IS data to their
source region near the Sun. Several RS instruments can be directed
to specific targets situated on the solar disk just days before
data acquisition. To compare IS and RS, data we must improve our
understanding of how heliospheric probes magnetically connect to the
solar disk.
Aims: The aim of the present paper is to briefly
review how the current modelling of the Sun and its atmosphere
can support Solar Orbiter science. We describe the results of a
community-led effort by European Space Agency's Modelling and Data
Analysis Working Group (MADAWG) to develop different models, tools,
and techniques deemed necessary to test different theories for the
physical processes that may occur in the solar plasma. The focus here
is on the large scales and little is described with regards to kinetic
processes. To exploit future IS and RS data fully, many techniques have
been adapted to model the evolving 3D solar magneto-plasma from the
solar interior to the solar wind. A particular focus in the paper is
placed on techniques that can estimate how Solar Orbiter will connect
magnetically through the complex coronal magnetic fields to various
photospheric and coronal features in support of spacecraft operations
and future scientific studies.
Methods: Recent missions such as
STEREO, provided great opportunities for RS, IS, and multi-spacecraft
studies. We summarise the achievements and highlight the challenges
faced during these investigations, many of which motivated the Solar
Orbiter mission. We present the new tools and techniques developed
by the MADAWG to support the science operations and the analysis of
the data from the many instruments on Solar Orbiter.
Results:
This article reviews current modelling and tool developments that ease
the comparison of model results with RS and IS data made available
by current and upcoming missions. It also describes the modelling
strategy to support the science operations and subsequent exploitation
of Solar Orbiter data in order to maximise the scientific output
of the mission.
Conclusions: The on-going community effort
presented in this paper has provided new models and tools necessary
to support mission operations as well as the science exploitation of
the Solar Orbiter data. The tools and techniques will no doubt evolve
significantly as we refine our procedure and methodology during the
first year of operations of this highly promising mission.
Title: Metis: the Solar Orbiter visible light and ultraviolet
coronal imager
Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi,
Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli,
Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek;
Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo,
Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki,
Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe;
Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro;
Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro;
Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola;
Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso,
Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis,
Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy,
Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki,
Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael;
Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi,
Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio;
Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco;
Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci,
Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo;
Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo;
Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro;
Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo,
Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone,
Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero,
María; Amoruso, Mauro; Centonze, Vito
Bibcode: 2020A&A...642A..10A
Altcode: 2019arXiv191108462A
Aims: Metis is the first solar coronagraph designed for a
space mission and is capable of performing simultaneous imaging of the
off-limb solar corona in both visible and UV light. The observations
obtained with Metis aboard the Solar Orbiter ESA-NASA observatory
will enable us to diagnose, with unprecedented temporal coverage and
spatial resolution, the structures and dynamics of the full corona
in a square field of view (FoV) of ±2.9° in width, with an inner
circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7
R⊙ to about 9 R⊙, owing to the eccentricity
of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter
mission profile, Metis will be able to observe the solar corona
from a close (0.28 AU, at the closest perihelion) vantage point,
achieving increasing out-of-ecliptic views with the increase of the
orbit inclination over time. Moreover, observations near perihelion,
during the phase of lower rotational velocity of the solar surface
relative to the spacecraft, allow longer-term studies of the off-limb
coronal features, thus finally disentangling their intrinsic evolution
from effects due to solar rotation.
Methods: Thanks to a novel
occultation design and a combination of a UV interference coating of
the mirrors and a spectral bandpass filter, Metis images the solar
corona simultaneously in the visible light band, between 580 and 640
nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light
channel also includes a broadband polarimeter able to observe the
linearly polarised component of the K corona. The coronal images in
both the UV H I Lyman-α and polarised visible light are obtained at
high spatial resolution with a spatial scale down to about 2000 km
and 15 000 km at perihelion, in the cases of the visible and UV light,
respectively. A temporal resolution down to 1 s can be achieved when
observing coronal fluctuations in visible light.
Results: The
Metis measurements, obtained from different latitudes, will allow for
complete characterisation of the main physical parameters and dynamics
of the electron and neutral hydrogen/proton plasma components of the
corona in the region where the solar wind undergoes the acceleration
process and where the onset and initial propagation of coronal mass
ejections (CMEs) take place. The near-Sun multi-wavelength coronal
imaging performed with Metis, combined with the unique opportunities
offered by the Solar Orbiter mission, can effectively address crucial
issues of solar physics such as: the origin and heating/acceleration
of the fast and slow solar wind streams; the origin, acceleration,
and transport of the solar energetic particles; and the transient
ejection of coronal mass and its evolution in the inner heliosphere,
thus significantly improving our understanding of the region connecting
the Sun to the heliosphere and of the processes generating and driving
the solar wind and coronal mass ejections.
Conclusions: This
paper presents the scientific objectives and requirements, the overall
optical design of the Metis instrument, the thermo-mechanical design,
and the processing and power unit; reports on the results of the
campaigns dedicated to integration, alignment, and tests, and to
the characterisation of the instrument performance; describes the
operation concept, data handling, and software tools; and, finally,
the diagnostic techniques to be applied to the data, as well as a brief
description of the expected scientific products. The performance of the
instrument measured during calibrations ensures that the scientific
objectives of Metis can be pursued with success. Metis website:
http://metis.oato.inaf.it
Title: Estimate of Plasma Temperatures Across a CME-Driven Shock
from a Comparison Between EUV and Radio Data
Authors: Frassati, Federica; Mancuso, Salvatore; Bemporad, Alessandro
Bibcode: 2020SoPh..295..124F
Altcode:
In this work, we analyze the evolution of an EUV wave front associated
with a solar eruption that occurred on 30 October 2014, with the aim of
investigating, through differential emission measure (DEM) analysis,
the physical properties of the plasma compressed and heated by the
accompanying shock wave. The EUV wave was observed by the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO)
and was accompanied by the detection of a metric Type II burst
observed by ground-based radio spectrographs. The EUV signature of
the shock wave was also detected in two of the AIA channels centered
at 193 Å and 211 Å as an EUV intensity enhancement propagating
ahead of the associated CME. The density compression ratio X of the
shock as inferred from the analysis of the EUV data is X ≈1.23 , in
agreement with independent estimates obtained from the analysis of the
Type II band-splitting of the radio data and inferred by adopting the
upstream-downstream interpretation. By applying the Rankine-Hugoniot
jump conditions under the hypothesis of a perpendicular shock, we also
estimate the temperature ratio as TD/TU≈1.55
and the post-shock temperature as TD≈2.75 MK. The modest
compression ratio and temperature jump derived from the EUV analysis
at the shock passage are typical of weak coronal shocks.
Title: On the Possibility of Detecting Helium D3 Line Polarization
with Metis
Authors: Heinzel, Petr; Štěpán, Jiři; Bemporad, Alessandro;
Fineschi, Silvano; Jejčič, Sonja; Labrosse, Nicolas; Susino, Roberto
Bibcode: 2020ApJ...900....8H
Altcode: 2020arXiv200708940H
Metis, the space coronagraph on board the Solar Orbiter, offers us
new capabilities for studying eruptive prominences and coronal mass
ejections (CMEs). Its two spectral channels, hydrogen Lα and visible
light (VL), will provide for the first time coaligned and cotemporal
images to study dynamics and plasma properties of CMEs. Moreover,
with the VL channel (580-640 nm) we find an exciting possibility
to detect the helium D3 line (587.73 nm) and its linear
polarization. The aim of this study is to predict the diagnostic
potential of this line regarding the CME thermal and magnetic
structure. For a grid of models we first compute the intensity of the
D3 line together with VL continuum intensity due to Thomson
scattering on core electrons. We show that the Metis VL channel will
detect a mixture of both, with predominance of the helium emission at
intermediate temperatures between 30 and 50,000 K. Then we use the
code HAZEL to compute the degree of linear polarization detectable
in the VL channel. This is a mixture of D3 scattering
polarization and continuum polarization. The former one is lowered in
the presence of a magnetic field and the polarization axis is rotated
(Hanle effect). Metis has the capability of measuring Q/I and U/I
polarization degrees and we show their dependence on temperature and
magnetic field. At T = 30,000 K we find a significant lowering of
Q/I which is due to strongly enhanced D3 line emission,
while depolarization at 10 G amounts roughly to 10%.
Title: Extensive Study of a Coronal Mass Ejection with UV and
White-light Coronagraphs: The Need for Multiwavelength Observations
Authors: Ying, Beili; Bemporad, Alessandro; Feng, Li; Lu, Lei; Gan,
Weiqun; Li, Hui
Bibcode: 2020ApJ...899...12Y
Altcode: 2020arXiv200704575Y
Coronal mass ejections (CMEs) often show different features in
different bandpasses. By combining data in white-light (WL) and
ultraviolet (UV) bands, we have applied different techniques to
derive plasma temperatures, electron density, internal radial speed,
and so on, within a fast CME. They serve as extensive tests of the
diagnostic capabilities developed for the observations provided by
future multichannel coronagraphs (such as Solar Orbiter/Metis, Chinese
Advanced Space-based Solar Observatory/Lyα Solar Telescope (LST),
and PROBA-3/ASPIICS). The data involved include WL images acquired by
Solar and Heliospheric Observatory (SOHO)/Large Angle Spectroscopic
Coronagraph (LASCO) coronagraphs, and intensities measured by the
SOHO/UV Coronagraph Spectrometer (UVCS) at 2.45 R⊙ in
the UV (H I Lyα and O VI 1032 Å lines) and WL channels. Data from
the UVCS WL channel have been employed for the first time to measure
the CME position angle with the polarization-ratio technique. Plasma
electron and effective temperatures of the CME core and void are
estimated by combining UV and WL data. Due to the CME expansion and the
possible existence of prominence segments, the transit of the CME core
results in decreases in the electron temperature down to 105
K. The front is observed as a significant dimming in the Lyα intensity,
associated with a line broadening due to plasma heating and flows along
the line of sight. The 2D distribution of plasma speeds within the CME
body is reconstructed from LASCO images and employed to constrain the
Doppler dimming of the Lyα line and simulate future CME observations
by Metis and LST.
Title: Hydrogen non-equilibrium ionisation effects in coronal mass
ejections
Authors: Pagano, P.; Bemporad, A.; Mackay, D. H.
Bibcode: 2020A&A...637A..49P
Altcode: 2020arXiv200312337P
Context. A new generation of coronagraphs used to study solar wind and
coronal mass ejections (CMEs) are being developed and launched. These
coronagraphs will heavily rely on multi-channel observations where
visible light (VL) and UV-EUV (ultraviolet-extreme ultraviolet)
observations provide new plasma diagnostics. One of these instruments,
Metis on board ESA-Solar Orbiter, will simultaneously observe VL and
the UV Lyman-α line. The number of neutral hydrogen atoms (a small
fraction of coronal protons) is a key parameter for deriving plasma
properties, such as the temperature from the observed Lyman-α line
intensity. However, these measurements are significantly affected
if non-equilibrium ionisation effects occur, which can be relevant
during CMEs.
Aims: The aim of this work is to determine if
non-equilibrium ionisation effects are relevant in CMEs and, in
particular, when and in which regions of the CME plasma ionisation
equilibrium can be assumed for data analysis.
Methods:
We used a magneto-hydrodynamic (MHD) simulation of a magnetic flux
rope ejection to generate a CME. From this, we then reconstructed the
ionisation state of hydrogen atoms in the CME by evaluating both the
advection of neutral and ionised hydrogen atoms and the ionisation
and recombination rates in the MHD simulation.
Results: We
find that the equilibrium ionisation assumption mostly holds in the
core of the CME, which is represented by a magnetic flux rope. In
contrast, non-equilibrium ionisation effects are significant at the
CME front, where we find about 100 times more neutral hydrogen atoms
than prescribed by ionisation equilibrium conditions. We find this to
be the case even if this neutral hydrogen excess might be difficult
to identify due to projection effects.
Conclusions: This work
provides key information for the development of a new generation of
diagnostic techniques that aim to combine visible light and Lyman-α
line emissions. The results show that non-equilibrium ionisation effects
need to be considered when we analyse CME fronts. Incorrectly assuming
equilibrium ionisation in these regions would lead to a systematic
underestimate of plasma temperatures.
Title: Modeling and forecasting the background solar wind with
data-driven physics-based models
Authors: Lavarra, Michael; Pinto, Rui; Rouillard, Alexis; Kouloumvakos,
Athanasios; Bemporad, Alessandro; Nickolos Arge, Charles; Alexandre,
Matthieu; Genot, Vincent
Bibcode: 2020EGUGA..2217669L
Altcode:
The quasi-steady solar wind flow is a key component of space weather,
being the source of corotating density structures that perturb planetary
atmospheres and affect the propagation of impulsive perturbations (such
as CME). Fast and slow wind streams develop at different places in the
solar atmosphere, reflecting the global distribution of the coronal
magnetic field during solar cycle and its consequences for heat and mass
transport across the corona. I will present recent advances on global
solar wind simulations that provides robust and fully physics-based
predictions of the structure and physical parameters of the solar wind
based on a multi-1D approach (MULTI-VP, ISAM). Such advances relate
to the driving the models with time-dependant magnetogram data,
to the inclusion of transient heating phenomena, and to switching
from a fluid to a multi-species description of the solar wind. The
model was also driven by daily synchronic magnetograms (ADAPT) for a
full solar rotation and the simulation results were compared to UVCS
plane-of-sky data.The simulations produce a large range of synthetic
observables (e.g multi-spacecraft in-situ measurements, white-light
and EUV imagery) meant to be compared to data from current and future
missions (e.g Solar Orbiter and Parker Solar Probe), and to establish
physiccal connections between remote observation of the solar surface
and corona and the interplanetary medium.
Title: First Determination of 2D Speed Distribution within the Bodies
of Coronal Mass Ejections with Cross-correlation Analysis
Authors: Ying, B.; Bemporad, A.; Giordano, S.; Pagano, P.; Feng, L.;
Lu, L.; Li, H.; Gan, W.
Bibcode: 2019AGUFMSH21D3307Y
Altcode:
The determination of the speed of coronal mass ejections (CMEs) is
usually done by tracking brighter features (such as the CME front
and core) in visible light (VL) coronagraphic images and by deriving
unidimensional profiles of the CME speed as a function of altitude or
time. Nevertheless, CMEs are usually characterized by the presence of
significant density inhomogeneities propagating outward with different
radial and latitudinal projected speeds, resulting in a complex
evolution eventually forming the interplanetary CME. In this work, we
demonstrate for the first time how coronagraphic image sequences can be
analyzed with the cross-correlation technique to derive two-dimensional
(2D) maps of the almost instantaneous plasma speed distribution within
the body of CMEs. The technique is first tested with the analysis of
synthetic data and then applied to real observations. Results from this
work allow us to characterize the distribution and time evolution of
kinetic energy inside CMEs, as well as the mechanical energy (combined
with the kinetic and potential energy) partition between the core and
front of the CME. In the future, CMEs will be observed by two channels
(VL and UV Lyα) coronagraphs, such as Metis on board ESA Solar Orbiter
mission as well as the Lyα Solar Telescope on board the Chinese
Advanced Space-based Solar Observatory mission. Our results will help
in the analysis of these future observations, helping in particular
to take into account the 2D distribution of Lyα Doppler dimming effect.
Title: Modeling and forecasting the background solar wind with
data-driven physics-based models.
Authors: Pinto, R.; Rouillard, A. P.; Kouloumvakos, A.; Valette, E.;
Bemporad, A.; Arge, C. N.; Alexandre, M.; Genot, V. N.
Bibcode: 2019AGUFMSH11C3400P
Altcode:
The quasi-steady solar wind flow is a key component of space weather,
being the source of corotating density structures that perturb
planetary atmospheres and affect the propagation of impulsive
perturbations (such as CME). Fast and slow wind streams develop
ate different places in the solar atmosphere, reflecting the global
distribution of the coronal magnetic field during solar cycle. I will
present global solar wind simulations obtained via a numerical model
(MULTI-VP) that provides robust and fully physics-based predictions
of the structure and physical parameters of the solar wind. The
model is driven by a combination of existing surface magnetograms
(WSO, SOLIS, GONG), flux-transport and data assimilation techniques
(ADAPT), different coronal field reconstruction methods (PFSS,
NLFFF), and interfaces with multiple heliospheric propagation models
(CDPP/AMDA 1D MHD, ENLIL, EUHFORIA). These simulations were calibrated
against in-situ measurements of different spacecraft, white-light
J-Maps and coronal/heliospheric imager. The CIR's identified in the
HELCATS CIRCAT catalogue were traced back to the low corona, and
their positions were verified to correlate well with the interfaces
of fast and slow wind streams simulated. The model was also driven by
daily synchronic magnetograms (ADAPT) for a full solar rotation and
the simulation results were compared to UVCS plane-of-sky data. The
wind model interfaces with several IRAP data tools, such as the
Connectivity Tool and the SEP tool, hence providing invaluable support
for the exploitation of Solar Orbiter and Parker Solar Probe, and to
establish synergies between them. I will also report on the on-going
development of the real-time space weather forecasting pipeline SWiFT
(Solar Wind Flux-Tube)-FORECAST that benefits from these advances in
solar wind modelling.
Title: Detection of Coronal Mass Ejections at L1 and Forecast of
Their Geoeffectiveness
Authors: Telloni, Daniele; Antonucci, Ester; Bemporad, Alessandro;
Bianchi, Tiziano; Bruno, Roberto; Fineschi, Silvano; Magli, Enrico;
Nicolini, Gianalfredo; Susino, Roberto
Bibcode: 2019ApJ...885..120T
Altcode:
A novel tool aimed to detect solar coronal mass ejections (CMEs)
at the Lagrangian point L1 and to forecast their geoeffectiveness
is presented in this paper. This approach is based on the analysis
of in situ magnetic field and plasma measurements to compute some
important magnetohydrodynamic quantities of the solar wind (the total
pressure, the magnetic helicity, and the magnetic and kinetic energy),
which are used to identify the CME events, that is their arrival and
transit times, and to assess their likelihood for impacting the Earths
magnetosphere. The method is essentially based on the comparison of
the topological properties of the CME magnetic field configuration and
of the CME energetic budget with those of the quasi-steady ambient
solar wind. The algorithm performances are estimated by testing the
tool on solar wind data collected in situ by the Wind spacecraft from
2005 to 2016. In the scanned 12 yr time interval, it results that
(i) the procedure efficiency is of 86% for the weakest magnetospheric
disturbances, increasing with the level of the geomagnetic storming,
up to 100% for the most intense geomagnetic events, (ii) zero false
positive predictions are produced by the algorithm, and (iii) the
mean delay between the potentially geoeffective CME detection and
the geomagnetic storm onset if of 4 hr, with a 98% 2-8 hr confidence
interval. Hence, this new technique appears to be very promising in
forecasting space weather phenomena associated to CMEs.
Title: Distributed framework for Space Weather forecasts
Authors: Fabio Mulone, Angelo; Casti, Marta; Susino, Roberto; Messineo,
Rosario; Antonucci, Ester; Chiesura, Gabriele; Telloni, Daniele;
De March, Ruben; Magli, Enrico; Bemporad, Alessandro; Nicolini,
Gianalfredo; Fineschi, Silvano; Solitro, Filomena; Martino, Michele
Bibcode: 2019EPSC...13.1997F
Altcode:
HDS (Heliospheric Data System) is a system designed and implemented to
provide space weather services. The main system goal is to reduce the
time between the space weather services definition and their activation
in operating environment. It is capable to manage and process near-real
time data. Tens of different data sources, related to past and current
missions, have been integrated. Data managed by the system have been
described using standard data models. Big data technologies have
been exploited to deal with the challenges of big data management
and processing. The first version of the system provided medium and
short-term forecast of geo-effective space weather events like the
coronal mass ejections (CMEs).
Title: Comparing extrapolations of the coronal magnetic field
structure at 2.5 R⊙ with multi-viewpoint coronagraphic
observations
Authors: Sasso, C.; Pinto, R. F.; Andretta, V.; Howard, R. A.;
Vourlidas, A.; Bemporad, A.; Dolei, S.; Spadaro, D.; Susino, R.;
Antonucci, E.; Abbo, L.; Da Deppo, V.; Fineschi, S.; Frassetto, F.;
Landini, F.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.;
Romoli, M.; Telloni, D.; Ventura, R.
Bibcode: 2019A&A...627A...9S
Altcode: 2019arXiv190509005S
The magnetic field shapes the structure of the solar corona, but we
still know little about the interrelationships between the coronal
magnetic field configurations and the resulting quasi-stationary
structures observed in coronagraphic images (such as streamers,
plumes, and coronal holes). One way to obtain information on the
large-scale structure of the coronal magnetic field is to extrapolate
it from photospheric data and compare the results with coronagraphic
images. Our aim is to verify whether this comparison can be a fast
method to systematically determine the reliability of the many methods
that are available for modeling the coronal magnetic field. Coronal
fields are usually extrapolated from photospheric measurements that
are typically obtained in a region close to the central meridian on
the solar disk and are then compared with coronagraphic images at the
limbs, acquired at least seven days before or after to account for solar
rotation. This implicitly assumes that no significant changes occurred
in the corona during that period. In this work, we combine images from
three coronagraphs (SOHO/LASCO-C2 and the two STEREO/SECCHI-COR1) that
observe the Sun from different viewing angles to build Carrington maps
that cover the entire corona to reduce the effect of temporal evolution
to about five days. We then compare the position of the observed
streamers in these Carrington maps with that of the neutral lines
obtained from four different magnetic field extrapolations to evaluate
the performances of the latter in the solar corona. Our results show
that the location of coronal streamers can provide important indications
to distinguish between different magnetic field extrapolations.
Title: First Determination of 2D Speed Distribution within the Bodies
of Coronal Mass Ejections with Cross-correlation Analysis
Authors: Ying, Beili; Bemporad, Alessandro; Giordano, Silvio; Pagano,
Paolo; Feng, Li; Lu, Lei; Li, Hui; Gan, Weiqun
Bibcode: 2019ApJ...880...41Y
Altcode: 2019arXiv190511772Y
The determination of the speed of coronal mass ejections (CMEs) is
usually done by tracking brighter features (such as the CME front
and core) in visible light (VL) coronagraphic images and by deriving
unidimensional profiles of the CME speed as a function of altitude or
time. Nevertheless, CMEs are usually characterized by the presence of
significant density inhomogeneities propagating outward with different
radial and latitudinal projected speeds, resulting in a complex
evolution eventually forming the interplanetary CME. In this work, we
demonstrate for the first time how coronagraphic image sequences can be
analyzed with the cross-correlation technique to derive two-dimensional
(2D) maps of the almost instantaneous plasma speed distribution within
the body of CMEs. The technique is first tested with the analysis of
synthetic data and then applied to real observations. Results from this
work allow us to characterize the distribution and time evolution of
kinetic energy inside CMEs, as well as the mechanical energy (combined
with the kinetic and potential energy) partition between the core and
front of the CME. In the future, CMEs will be observed by two channels
(VL and UV Lyα) coronagraphs, such as Metis on board ESA Solar Orbiter
mission as well as the Lyα Solar Telescope on board the Chinese
Advanced Space-based Solar Observatory mission. Our results will help
in the analysis of these future observations, helping in particular
to take into account the 2D distribution of Lyα Doppler dimming effect.
Title: PROBA-3 formation-flying metrology: algorithms for the shadow
position sensor system
Authors: Casti, M.; Bemporad, A.; Fineschi, S.; Capobianco, G.;
Loreggia, D.; Noce, V.; Landini, F.; Thizy, C.; Galano, D.; Rougeot, R.
Bibcode: 2019SPIE11180E..82C
Altcode:
PROBA-3 ESA's mission aims at demonstrating the possibility and the
capacity to carry out a space mission in which two spacecrafts fly in
formation and maintain a fixed configuration. In particular, these
two satellites - the Coronagraph Spacecraft (CSC) and the Occulter
Spacecraft (OSC) - will form a 150-meters externally occulted
coronagraph for the purpose of observing the faint solar corona,
close to the solar limb - i.e. 1.05 solar radii from the Sun's center
(RΘ). The first satellite will host the ASPIICS (Association
de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne
Solaire) coronagraph as primary payload. These features give to the
PROBA-3 mission the characteristics of both, a technological and a
scientific mission. Several metrology systems have been implemented
in order to keep the formation-flying configuration. Among them,
the Shadow Position Sensors (SPSs) assembly. The SPSs are designed
to verify the sun-pointing alignment between the Coronagraph
pupil entrance centre and the umbra cone generated by the Occulter
Disk. The accurate alignment between the spacecrafts is required for
observations of the solar corona as much close to the limb as 1.05
RΘ.The metrological system based on the SPSs is composed
of two sets of four micro arrays of Silicon Photomultipliers (SiPMs)
located on the coronagraph pupil plane and acquiring data related
to the intensity of the penumbra illumination level to retrieve the
spacecrafts relative position. We developed and tested a dedicated
algorithm for retrieving the satellites position with respect to the
Sun. Starting from the measurements of the penumbra profile in four
different spots and applying a suitable logic, the algorithm evaluates
the spacecraft tri-dimensional relative position. In particular, during
the observational phase, when the two satellites will be at 150 meters
of distance, the algorithm will compute the relative position around
the ideal aligned position with an accuracy of 500μm within the lateral
plane and 500 mm for the longitudinal measurement. This work describes
the formation flying algorithm based on the SPS measurements. In
particular, the implementation logic and the formulae are described
together with the results of the algorithm testing.
Title: Effect of the non-uniform solar chromospheric Lyα radiation
on determining the coronal H I outflow velocity
Authors: Dolei, S.; Spadaro, D.; Ventura, R.; Bemporad, A.; Andretta,
V.; Sasso, C.; Susino, R.; Antonucci, E.; Da Deppo, V.; Fineschi,
S.; Frassetto, F.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi,
M.; Romoli, M.
Bibcode: 2019A&A...627A..18D
Altcode:
We derived maps of the solar wind outflow velocity of coronal
neutral hydrogen atoms at solar minimum in the altitude range
1.5-4.0 R⊙. We applied the Doppler dimming technique to
coronagraphic observations in the UV H I Lyα line at 121.6 nm. The
technique exploits the intensity reduction in the coronal line with
increasing velocities of the outflowing plasma to determine the
solar wind velocity by iterative modelling. The Lyα line intensity
is sensitive to the wind outflow velocity and also depends on the
physical properties of coronal particles and underlying chromospheric
emission. Measurements of irradiance by the chromospheric Lyα
radiation in the corona are required for a rigorous application of
the Doppler dimming technique, but they are not provided by past
and current instrumentations. A correlation function between the H
I 121.6 nm and He II 30.4 nm line intensities was used to construct
Carrington rotation maps of the non-uniform solar chromospheric Lyα
radiation and thus to compute the Lyα line irradiance throughout
the outer corona. Approximations concerning the temperature of
the scattering H I atoms and exciting solar disc radiation were
also adopted to significantly reduce the computational time and
obtain a faster procedure for a quick-look data analysis of future
coronagraphic observations. The effect of the chromospheric Lyα
brightness distribution on the resulting H I outflow velocities
was quantified. In particular, we found that the usual uniform-disc
approximation systematically leads to an overestimated velocity in
the polar and mid-latitude coronal regions up to a maximum of about
50-60 km s-1 closer to the Sun. This difference decreases at
higher altitudes, where an increasingly larger chromospheric portion,
including both brighter and darker disc features, contributes to
illuminate the solar corona, and the non-uniform radiation condition
progressively approaches the uniform-disc approximation.
Title: Three-dimensional reconstruction of CME-driven shock-streamer
interaction from radio and EUV observations: a different take on
the diagnostics of coronal magnetic fields
Authors: Mancuso, S.; Frassati, F.; Bemporad, A.; Barghini, D.
Bibcode: 2019A&A...624L...2M
Altcode: 2019arXiv190306604M
On 2014 October 30, a band-splitted type II radio burst associated
with a coronal mass ejection (CME) observed by the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamic Observatory (SDO) occurred
over the southeast limb of the Sun. The fast expansion in all directions
of the plasma front acted as a piston and drove a spherical fast shock
ahead of it, whose outward progression was traced by simultaneous
images obtained with the Nançay Radioheliograph (NRH). The geometry
of the CME/shock event was recovered through 3D modeling, given the
absence of concomitant stereoscopic observations, and assuming that the
band-splitted type II burst was emitted at the intersection of the shock
surface with two adjacent low-Alfvén speed coronal streamers. From the
derived spatiotemporal evolution of the standoff distance between shock
and CME leading edge, we were finally able to infer the magnetic field
strength B in the inner corona. A simple radial profile of the form
B(r) = (12.6 ± 2.5)r-4 nicely fits our results, together
with previous estimates, in the range r = 1.1-2.0 R⊙.
Title: Coronagraphic observations of Solar Eruptions and Solar Wind
in the UV range: past, present and future
Authors: Bemporad, Alessandro
Bibcode: 2019EGUGA..2117131B
Altcode:
After the first observations of the extended solar corona in the
UV carried out starting from late '70s with rocket experiments,
and later on with the Spartan flights, the field was revolutionized
thanks to the UVCS (UV Coronagraph Spectrometer) instrument on-board
SOHO mission. UVCS observed the UV extended corona (tipically above
0.5 solar radii from the limb) at different latitudes over more than
15 years (1996-2012), and captured the transit of hundreds of small-
and large-scale solar eruptions (CMEs, jets, prominences). These
observations (combined with data acquired by other instruments)
allowed to derive unique information on the early evolution of
plasma embedded in solar eruptions, and on related topics (e.g. 3D
structure, post-CME Current Sheets, CME-driven shocks). The same
data led also to fundamental new discoveries on the Solar Wind,
and allowed to characterize the backround corona being crossed by
each solar eruption. At present UVCS is not taking data anymore since
2012, but lot of data in the archive still have to be analysed; for
the next future, no similar instruments have been selected at present
as a payload of forthcoming solar missions. Nevertheless, the next
generation multi-channel coronagraphs (such as Metis on-board Solar
Orbiter) will observe at the same time and same locations the Visible
Light and the UV HI Lyman-alpha extended corona. These data will really
provide a new view not only of solar eruptions, but also of the ambient
solar wind. Future prospects will be summarized here.
Title: Comprehensive Analysis of the Formation of a Shock Wave
Associated with a Coronal Mass Ejection
Authors: Frassati, Federica; Susino, Roberto; Mancuso, Salvatore;
Bemporad, Alessandro
Bibcode: 2019ApJ...871..212F
Altcode:
On 2014 November 1, a solar prominence eruption associated with a C2.7
class flare and a type II radio burst resulted in a fast partial halo
coronal mass ejection (CME). Images acquired in the extreme ultraviolet
(EUV) by the Solar Dynamics Observatory/Atmospheric Imaging Assembly
(AIA) and PROBA2/SWAP and in white light (WL) by Solar and Heliospheric
Observatory/Large Angle and Spectrometric Coronagraph show the
expansion of a bright compression front ahead of the CME. In this work,
we present a detailed investigation of the CME-driven shock associated
with this event following the early evolution of the compression front
observed near the Sun up to the extended corona. Our aim is to shed
light on the long-debated issue concerning the location and timing of
shock formation in the corona. Through differential emission measure
analysis, we derived, for the first time, the compression ratio across
the expanding EUV front observed by AIA at different temperature
ranges: higher compression ratios corresponded to higher plasma
temperature ranges, as expected. Moreover, comparison between up- and
downstream temperatures and those expected via adiabatic compression
shows that no additional heating mechanisms occurred in the early
front expansion phase, implying that the shock formed beyond the AIA
field of view. Finally, the analysis of the associated type II radio
burst, in combination with the inferred coronal density distribution,
allowed us to identify a well-defined region located northward of the
CME source region as the site for shock formation and to outline its
kinematics in accordance with the evolution of the expanding front as
obtained from the EUV and WL data.
Title: AntarctiCor: Solar Coronagraph in Antarctica for the ESCAPE
Project
Authors: Fineschi, S.; Capobianco, G.; Massone, G.; Susino, R.;
Zangrilli, L.; Bemporad, A.; Liberatore, A.; Landini, F.; Romoli,
M.; Damé, L.; Christille, J. M.; Sandri, P.; Marmonti, M.; Galy, C.
Bibcode: 2019NCimC..42...26F
Altcode:
The Antarctica solar coronagraph - AntarctiCor- for the "Extreme
Solar Coronagraphy Antarctic Program Experiment" -ESCAPE- comprises
an internally-occulted coronagraph based on the externally-occulted
ASPIICS coronagraph for the ESA formation-flying PROBA-3 mission. This
paper describes the AntarctiCor design for ground-based observations
from the DomeC Antarctica plateau of the polarized broad-band (591 nm
± 5 nm) K-corona and of the narrow-band (FWHM = 0.5 nm), polarized
emission of the coronal green-line at 530.3 nm. The science goal of
these observations is to map the topology and dynamics of the coronal
magnetic field, addressing coronal heating and space weather questions.
Title: Measuring the 2D distribution of the expansion speed of solar
eruptions: A first test based on synthetic coronagraphic data
Authors: Ying, B.; Bemporad, A.; Giordano, S.; Pagano, P.; Feng, L.
Bibcode: 2019NCimC..42...36Y
Altcode:
The determination of the propagation speed of Coronal Mass Ejections
(CMEs) is usually done by tracking the motion of isolated brighter
parcels of plasma embedded in the body of the eruption in coronagraphic
and heliospheric imagers. In this work we explore the possibility to
derive the 2D map of the instantaneous velocity distribution in the
body of a CME. To this end, in this first test we analysed synthetic
coronagraphic observations, to compare the derived CME speed with
the expanding speed of the simulated eruption. First results are
presented here.
Title: Metrology on-board PROBA-3: The Shadow Position Sensor (SPS)
subsystem
Authors: Noce, V.; Romoli, M.; Focardi, M.; Fineschi, S.; Loreggia,
D.; Casti, M.; Landini, F.; Baccani, C.; Bemporad, A.; Belluso, M.;
Capobianco, G.; Thizy, C.; Denis, F.; Buckley, S.
Bibcode: 2019NCimC..42...27N
Altcode:
PROBA-3 is an ESA Mission whose aim is to demonstrate the in-orbit
Formation Flying and attitude control capabilities of its two satellites
by means of closed-loop, on-board metrology. The two small spacecraft
will form a giant externally occulted coronagraph that will observe in
visible polarized light the inner part of the solar corona. The SPS
subsystem is composed of eight sensors that will measure, with the
required sensitivity and dynamic range, the penumbra light intensity
around the coronagraph instrument entrance pupil.
Title: Preface
Authors: Bemporad, A.; Criscuoli, S.; Del Moro, D.; Guglielmino,
S. L.; Landi, S.; Laurenza, M.; Reale, F.; Straus, T.; Vecchio, A.
Bibcode: 2019NCimC..42....1B
Altcode:
No abstract at ADS
Title: The Heliospheric Space Weather Center: A novel space weather
service
Authors: Casti, M.; Mulone, A. F.; Susino, R.; Chiesura, G.;
Telloni, D.; De March, R.; Antonucci, E.; Messineo, R.; Bemporad,
A.; Solitro, F.; Fineschi, S.; Magli, E.; Nicolini, G.; Caronte, ,
F.; Messerotti, M.
Bibcode: 2019NCimC..42...48C
Altcode:
The Heliospheric Space Weather Center project is the result of the
synergy between the Aerospace Logistics Technology Engineering Company
(ALTEC S.p.A.) and the INAF-Astrophysical Observatory of Torino,
both located in Turin, Italy. The main goal of this project is to
provide space weather medium and short-term forecast, by combining
remote-sensing and in situ open data with novel data analysis
technologies, giving to scientists the possibility of designing,
implementing, and validating space-weather algorithms using extensive
data sets.
Title: Determination of the physical properties of an erupting
prominence from SOHO/LASCO and UVCS observations
Authors: Susino, R.; Bemporad, A.; Heinzel, P.; Jejčič, S.; Anzer,
, U.; Dzifčáková, E.
Bibcode: 2019NCimC..42...37S
Altcode:
We studied the physical conditions of an erupting prominence
observed in the core of a coronal mass ejection, using combination
of SOHO/LASCO-C2 visible-light images and SOHO/UVCS ultraviolet
data. Measured intensities and profiles of the neutral-hydrogen
Lyman- α and Lyman- β lines and the 977 Å C III line were
used together with the visible-light brightness to derive the
geometrical and physical parameters of the prominence, such as the
line-of-sight apparent thickness, electron column density, kinetic
temperature, and microturbolent velocity. These parameters were used
to constrain a non-LTE ( i.e., out of local thermodynamic equilibrium)
radiative-transfer model of the prominence that provides the effective
thickness, electron density, and flow velocity, in a sample of points
selected along the prominence. The prominence can be described as a hot
structure with low electron density and very low gas pressure compared
to typical quiescent prominences. Intensities of the hydrogen lines
were also used for a detailed determination of the plasma line-of-sight
filling factor, in the two prominence points where simultaneous and
cospatial LASCO-C2 and UVCS observations were available.
Title: Kinematics of a compression front associated with a Coronal
Mass Ejection
Authors: Frassati, F.; Susino, R.; Mancuso, S.; Bemporad, A.
Bibcode: 2019NCimC..42...35F
Altcode:
On 2014 November 1st a solar prominence eruption associated with a C2.7
class flare and a type II radio burst resulted in a fast partial halo
Coronal Mass Ejection (CME). Images acquired in the extreme UV (EUV)
by SDO/AIA and PROBA-2/SWAP, and in white light (WL) by SOHO/LASCO
show a bright compression front expanding ahead of the CME. The main
goal of this work was to infer the location and timing of the shock
formation in the corona. A comparison between the starting frequency
of the type II emission and the frequencies derived from the inferred
coronal density distribution, allowed us to identify a region located
northward of the CME as the most probable site for shock formation.
Title: Measuring the electron temperatures of coronal mass ejections
with future space-based multi-channel coronagraphs: a numerical test
Authors: Bemporad, A.; Pagano, P.; Giordano, S.
Bibcode: 2018A&A...619A..25B
Altcode:
Context. The determination from coronagraphic observations of physical
parameters of the plasma embedded in coronal mass ejections (CMEs)
is of crucial importance for our understanding of the origin and
evolution of these phenomena.
Aims: The aim of this work is
to perform the first ever numerical simulations of a CME as it will
be observed by future two-channel (visible light VL and UV Ly-α)
coronagraphs, such as the Metis instrument on-board ESA-Solar Orbiter
mission, or any other future coronagraphs with the same spectral
band-passes. These simulations are then used to test and optimize the
plasma diagnostic techniques to be applied to future observations of
CMEs.
Methods: The CME diagnostic techniques are tested here
by analyzing synthetic coronagraphic observations. First, a numerical
three-dimensional (3D) magnetohydrodynamic (MHD) simulation of a CME
is performed, and the plasma parameters in the simulation are used to
generate synthetic visible light (VL) and ultraviolet (UV) coronagraphic
two-dimensional (2D) images of the eruption (i.e., integrated along
the line-of-sight). Second, synthetic data are analyzed with different
assumptions (as will be done with real data), to infer the kinematic
properties of the CME (such as the extension along the line-of-sight
of the emitting region, the expansion speed, and the CME propagation
direction), as well as physical parameters of the CME plasma (the
plasma electron density and temperature). A comparison between input
parameters from the simulation and output parameters from the synthetic
data analysis is then performed.
Results: The inversion of VL
polarized data allows to successfully determine the CME speed and 3D
propagation direction (with the polarization ratio technique), as well
as to derive information on the extension along the line-of-sight of
the emitting plasma, a crucial parameter needed to convert the plasma
electron column densities into number densities. These parameters
are used to analyze UV Ly-α images and to estimate the CME plasma
temperature, also taking into account Doppler dimming effect. Output
plasma temperatures are in general underestimated, both in the CME body
and core regions. By neglecting the UV Ly-α radiative excitation of
H atoms, reliable temperatures can be more easily derived in the CME
core (within ∼60%). On the other hand, we show that a determination
of temperatures (within ∼20-30%) in the CME body requires 2D maps
of CME radial speeds and Doppler dimming coefficients to be derived.
Title: Hot prominence detected in the core of a coronal mass
ejection. III. Plasma filling factor from UVCS Lyman-α and Lyman-β
observations
Authors: Susino, R.; Bemporad, A.; Jejčič, S.; Heinzel, P.
Bibcode: 2018A&A...617A..21S
Altcode: 2018arXiv180512465S
Context. We study an erupting prominence embedded in the core of a
coronal mass ejection that occurred on August 2, 2000, and focus on
deriving the plasma filling factor of the prominence.
Aims:
We explore two methods for measuring this factor along the line of
sight. They are based on a combination of visible-light and ultraviolet
spectroscopic observations.
Methods: Theoretical relationships
for resonant scattering and collisional excitation were used to evaluate
the intensity of the neutral hydrogen Lyman-α and Lyman-β lines in
two prominence points where simultaneous and cospatial LASCO-C2 and
UVCS data were available. Thermodynamic and geometrical parameters
assumed for the calculation (i.e., electron column density, kinetic
temperature, flow velocity, chromospheric Lyα and Lyβ intensities
and profiles, and thickness of the prominence along the line of sight)
are provided by both observations and the results of a detailed 1D
non-local thermal equilibrium (non-LTE) radiative-transfer model
of the prominence, developed in our previous work. The geometrical
filling factor was derived from comparing the calculated and measured
intensities of the two lines. The results were then checked against the
non-LTE model in order to verify the reliability of the methods.
Results: The resulting filling factors are consistent with the model in
both prominence points when the radiative and collisional components
of the total intensity of the hydrogen lines are separated using
the Lyα and Lyβ line intensities, which is required to estimate
the filling factor. The exploration of the parameter space shows
that the results are weakly sensitive to the plasma flow velocity,
but depend more strongly on the assumed kinetic temperatures.
Conclusions: The combination of visible-light and ultraviolet Lyα
and Lyβ data can be used to approximately estimate the line-of-sight
geometrical filling factor in erupting prominences, but the proposed
technique, which is model dependent, is reliable only for emission
that is optically thin in the lines considered, a condition that is
not in general representative of prominence plasma.
Title: Space Weather Services from Integration of Remote Sensing
and In Situ Data from several Solar Space Missions
Authors: Bemporad, Alessandro; Fineschi, Silvano; Telloni, Daniele;
Antonucci, Ester; Susino, Roberto; Nicolini, Gianalfredo; Casti,
Marta; Messineo, Rosario; Fabio Mulone, Angelo; Filippi, Fabio;
Solitro, Filomena; Ciampolini, Armando; Martino, Michele; Magli,
Enrico; Volpicelli, Antonio; Bjorklund, Tomas
Bibcode: 2018cosp...42E.268B
Altcode:
The Heliospheric Data Centre project for Space Weather medium-term and
short-term forecast combines remote sensing and in situ open-access data
relative to the Sun, the Heliosphere and the Earth's magnetosphere. This
is done with the novel big data technologies, to provide scientists
with the possibility to design, implement and validate Space Weather
algorithms on extensive datasets.The Heliospheric Data Centre is
a joint effort between ALTEC and INAF-OATo, both located in Turin,
Italy. The project has two main objectives:1. Consolidate and evolve
the Heliospheric Data Centre, initially set up with the SOHO data
coming from the ESA approved SOLAR (SOho Long-term ARchive) archive,
in order to manage additional solar archives storing solar coronal and
heliospheric data coming from ESA and NASA space programs.2. Develop
a Heliospheric Space Weather Centre to forecast the impacts of solar
disturbances on the Heliosphere and the Earth's magnetosphere.
Title: Magnetic field measurements in the solar corona: facing the
challenge with ground and space based observations
Authors: Bemporad, Alessandro; Fineschi, Silvano; Mancuso, Salvatore;
Gibson, Sarah; Susino, Roberto; Massone, . Giuseppe; Capobianco,
Gerardo; Frassati, Federica
Bibcode: 2018cosp...42E.265B
Altcode:
Actual limitations in understanding physical processes occurring
in the solar atmosphere are related with our poor capabilities in
measuring magnetic fields in its layers. The knowledge of magnetic
fields in the solar corona is crucial to understand the origin of solar
flares and Coronal Mass Ejections, waves, coronal heating and solar
wind acceleration. For these reasons many different techniques have
been proposed to provide these measurements by analysing the emission
related with many different physical phenomena (e.g.: radio observations
of gyrosynchrotron and free-free emission, infrared observations of
Zeeman effect, visible and infrared obervations of the Hanle effect,
UV-EUV observations of CME-driven shock waves, etc..). In order
to provide a continuous monitoring of coronal fields, new ground-
and space-based instrumentations are currently under development, as
well as new techniques to infer the real fields from the line-of-sight
integrated coronal emission. At the same time, the forward modelling of
the expected emission starting from different possible coronal field
configurations is being developed, allowing the definition of the
required properties for future instrumentation and the verification
of the data analysis results.
Title: Early detection and propagation forecast of CMEs from
coronagraphic images
Authors: Bemporad, Alessandro; Fineschi, Silvano; Mancuso, Salvatore;
Giordano, Silvio; Susino, Roberto; Zangrilli, Luca
Bibcode: 2018cosp...42E.269B
Altcode:
In order to forecast the arrival times of Coronal Mass Ejections (CMEs)
at 1 AU for Space Weather purposes, many different pipelines and tools
are actually under development by different groups. The solar physics
group in Turin Observatory is currently developing new routines to
derive from the analysis of remote sensing data different information
needed for CME forecasting. These include the determination of ambient
Parker spiral conditions, the early detection of CMEs from coronagraphic
images, and their propagation in the interplanetary medium taking into
account magnetic drag forces. First results on thse activities will
be reviewd here.
Title: Sources and transport of energetic particles at high
heliolatitudes
Authors: Khabarova, Olga; Bemporad, Alessandro; Obridko, Vladimir;
Malandraki, Olga; Malova, Helmi; Kislov, Roman; Kuznetsov, Vladimir;
Cremades, Hebe; Kharshiladze, Alexander; Merenda, Luciano A.
Bibcode: 2018cosp...42E1739K
Altcode:
Understanding the origin and transport of energetic particles of
keV-MeV energies throughout the heliosphere still represents one of the
biggest problems of space physics. Our knowledge of the propagation of
energetic particles is mostly based on theoretical predictions compared
with spacecraft observations at low heliolatitudes. Meanwhile, the
occurrence of energetic particles at high heliolatitudes is even more
puzzling since only one spacecraft, Ulysses, flew over the poles of
the Sun and provided information on the energetic particle properties
far above the ecliptic plane. Ulysses observations show that energetic
particle flux enhancements occur at heliolatitudes over 40 degrees
at both solar maximum and minimum conditions (see, e.g., Smith et
al. 2001; Sanderson et al. 2003; Lario et al. 2004; Sanderson 2004;
Malandraki et al. 2009). This suggests various scenarios of particle
transport. Energetic particles of keV-MeV energies should propagate
mainly along magnetic field lines, but if a source is an active region
at low latitudes or an ICME, their detection at high latitudes can be
explained by particle diffusion across magnetic field lines either in
the solar wind or in the corona. In any event, sources of energetic
particles observed above the ecliptic during solar maxima are more
or less well identified.Interpretations of observations of keV-MeV
energetic particles in polar regions during solar minima are more
complicated. The association of energetic particle flux enhancements
in the polar heliosphere with corotating interaction regions, the
main sources of accelerated particles in quiet times, is sometimes
unsuccessful since there are no signatures of cross-field diffusion or
particle streaming from distant heliocentric distances back to the Sun
as it was presumed. The existence of long-lived conic (or cylindrical)
current sheets (CCSs) in the polar solar wind can naturally solve
this problem (Khabarova et al. 2017). It has been recently found
that CCSs are low-beta and low-speed structures formed within polar
coronal holes. CCS stability is supported by the tornado-like magnetic
field. The occurrence of magnetic separators near the poles in solar
minima is confirmed independently by reconstructions of the coronal
magnetic field based on photospheric magnetic field charts. We show
evidence for association of energetic particles observed by Ulysses
above the pole with reconnection polar jets located at the circle-shaped
touchdown of a CCS. Therefore, it is demonstrated that CCSs might serve
as channels for energetic particles accelerated in the solar corona by
magnetic reconnection, which sheds light on the mystery of energetic
particles observed at high heliolatitudes. This work is partly supported
by the International Space Science Institute (ISSI) in the framework
of International Team 405 entitled "Current Sheets, Turbulence,
Structures and Particle Acceleration in the Heliosphere." and RFBR
grants 16-02-00479, 17-02-00300 and 17-02-01328. Khabarova O.V. et al.,
High-latitude conic current sheets in the solar wind, The Astrophysical
Journal, 836, 108, 1, 2017, https://doi.org/10.3847/1538-4357/836/1/108
Title: Plasma physical parameters of a prominence embedded in the
core of a Coronal Mass Ejection
Authors: Bemporad, Alessandro; Anzer, Ulrich; Heinzel, Petr; Jejcic,
Sonja; Susino, Roberto
Bibcode: 2018cosp...42E.267B
Altcode:
We determine the plasma physical parameters of an erupting prominence
embedded in the core of a CME, combininging visible light coronagraphic
images from SOHO/LASCO with UV spectra acquired by SOHO/UVCS. Strong
UV emissions were detected in the hydrogen Lyman-α and Lyman-β
lines and C III line. Visible light and UV intensities have been used
to estimate the projected thickness and velocity of the prominence,
together with the effective plasma temperature, microturbolent velocity,
and column density. These parameters have been used to constrain
1D NLTE modeling of the erupting plasma, taking into account the
effects of large flow velocities (Doppler dimming). Roughly one-half
of considered points in the prominence body show a non-negligible
Lyman-α optical thickness. Comparison between the calculated and the
measured intensities of the two Lyman lines was also used to derive the
geometrical filling factor. Results show that the erupting prominence
plasma is relatively hot, with a low electron density, a wide range of
effective thicknesses, a rather narrow range of radial flow velocities,
and a microturbulence of about 25 km/s. This analysis provides a basis
for future diagnostics of prominences using the METIS coronagraph on
board the Solar Orbiter mission.
Title: CMEs and shocks evolution in the Interplanetary
Space. Observations of CME evolution from the Sun to the Earth
and beyond
Authors: Bemporad, Alessandro
Bibcode: 2018cosp...42E.266B
Altcode:
Thanks to remote sensing instruments from space-based observatories it
is possible to study in details the early propagation of solar eruptions
(or Coronal Mass Ejections - CMEs). The early detection of CMEs with
remote sensing instruments (e.g. EUV imagers and spectrometers, visible
light coronagraphs, radio spectrometers on-board SOHO, STEREO, SDO,
etc...) allows to identify the events propagating towards the Earth,
and derive in advance information that are crucial for Space Weather
forecasting applications. Higher up, the propagation of Interplanetary
CMEs has been followed many times with Heliospheric imagers (e.g. SMEI
on-board the Coriolis satellite, and HI1 - HI2 on-board the twin STEREO
spacecraft), providing information on ICME drag forces, deflections,
CME-CME interactions, preconditioning, and other phenomena affecting
their propagation to 1 AU and beyond. These data have proven to be very
useful also to derive early information on shock waves associated with
major eruptions, believed to be very important accelerators of Solar
Energetic Particles. Upcoming solar missions (Solar Orbiter, Parker
Solar Probe, PROBA-3, etc...) will provide a new view of CMEs, hopefully
helping us to answer some of the major open questions on these events.
Title: Hot Erupting Prominences in Cores of Cme's
Authors: Heinzel, Petr; Bemporad, Alessandro; Anzer, Ulrich; Jejcic,
Sonja; Susino, Roberto; Dzifcakova, Elena
Bibcode: 2018cosp...42E1421H
Altcode:
Coronal mass ejections (CME) associated with prominence eruptions
exhibit relatively coolmaterial in their cores. Such prominence
plasmas were frequently detected in various spectrallines by SOHO/UVCS
coronagraph and in the visible light by SOHO/LASCO as well as bySTEREO
coronagraphs. UVCS provided excellent spectra of CME-core prominences
and anextended catalogue of these data is available. We will present
recent results of a hot prominence diagnostics using the hydrogen Lyman
lines and the CIII line . The erupting prominence parameters are further
constrained by the visible light observations from LASCO-C2. A novel
non-LTE modeling based on such observations will be presented and we
will highlight the diagnostic potential of the UV and visible light for
future space coronagraphs like Metis on board the ESA Solar Orbiter
mission. The plasma parameters of such hot prominences are compared
with those obtained from numerical MHD simulations of erupting flux
ropes surrounded by CMEs. Finally, we will also mention synergies with
stellar analogues.
Title: Development of ASPIICS: a coronagraph based on Proba-3
formation flying mission
Authors: Galano, Damien; Bemporad, Alessandro; Buckley, Steve; Cernica,
Ileana; Dániel, Vladimír.; Denis, François; de Vos, Lieve; Fineschi,
Silvano; Galy, Camille; Graczyk, Rafal; Horodyska, Petra; Jacob,
Jérôme; Jansen, Richard; Kranitis, Nektarios; Kurowski, Michal;
Ladno, Michal; Ledent, Philippe; Loreggia, Davide; Melich, Radek;
Mollet, Dominique; Mosdorf, Michal; Paschalis, Antonios; Peresty,
Radek; Purica, Munizer; Radzik, Bartlomiej; Rataj, Miroslaw; Rougeot,
Raphaël.; Salvador, Lucas; Thizy, Cédric; Versluys, Jorg; Walczak,
Tomasz; Zarzycka, Alicja; Zender, Joe; Zhukov, Andrei
Bibcode: 2018SPIE10698E..2YG
Altcode:
This paper presents the recent achievements in the development
of ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun), a solar coronagraph that is the
primary payload of ESA's formation flying in-orbit demonstration mission
PROBA-3. The PROBA-3 Coronagraph System is designed as a classical
externally occulted Lyot coronagraph but it takes advantage of the
opportunity to place the 1.4 meter wide external occulter on a companion
spacecraft, about 150m apart, to perform high resolution imaging of the
inner corona of the Sun as close as 1.1 solar radii. Besides providing
scientific data, ASPIICS is also equipped with sensors for providing
relevant navigation data to the Formation Flying GNC system. This paper
is reviewing the recent development status of the ASPIICS instrument
as it passed CDR, following detailed design of all the sub-systems
and testing of STM and various Breadboard models.
Title: Mapping the solar wind HI outflow velocity in the inner
heliosphere by coronagraphic ultraviolet and visible-light
observations
Authors: Dolei, S.; Susino, R.; Sasso, C.; Bemporad, A.; Andretta,
V.; Spadaro, D.; Ventura, R.; Antonucci, E.; Abbo, L.; Da Deppo, V.;
Fineschi, S.; Focardi, M.; Frassetto, F.; Giordano, S.; Landini, F.;
Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.; Romoli, M.;
Telloni, D.
Bibcode: 2018A&A...612A..84D
Altcode:
We investigated the capability of mapping the solar wind outflow
velocity of neutral hydrogen atoms by using synergistic visible-light
and ultraviolet observations. We used polarised brightness images
acquired by the LASCO/SOHO and Mk3/MLSO coronagraphs, and synoptic Lyα
line observations of the UVCS/SOHO spectrometer to obtain daily maps
of solar wind H I outflow velocity between 1.5 and 4.0 R⊙
on the SOHO plane of the sky during a complete solar rotation (from
1997 June 1 to 1997 June 28). The 28-days data sequence allows us to
construct coronal off-limb Carrington maps of the resulting velocities
at different heliocentric distances to investigate the space and time
evolution of the outflowing solar plasma. In addition, we performed
a parameter space exploration in order to study the dependence of the
derived outflow velocities on the physical quantities characterising
the Lyα emitting process in the corona. Our results are important
in anticipation of the future science with the Metis instrument,
selected to be part of the Solar Orbiter scientific payload. It was
conceived to carry out near-sun coronagraphy, performing for the first
time simultaneous imaging in polarised visible-light and ultraviolet
H I Lyα line, so providing an unprecedented view of the solar wind
acceleration region in the inner corona. The movie (see Sect. 4.2)
is available at https://www.aanda.org
Title: Visibility of Prominences Using the He I D3 Line
Filter on the PROBA-3/ASPIICS Coronagraph
Authors: Jejčič, S.; Heinzel, P.; Labrosse, N.; Zhukov, A. N.;
Bemporad, A.; Fineschi, S.; Gunár, S.
Bibcode: 2018SoPh..293...33J
Altcode: 2018arXiv180700155J
We determine the optimal width and shape of the narrow-band filter
centered on the He I D3 line for prominence and coronal
mass ejection (CME) observations with the ASPIICS (Association of
Spacecraft for Polarimetric and Imaging Investigation of the Corona of
the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy)
satellite, to be launched in 2020. We analyze He I D3 line
intensities for three representative non-local thermal equilibrium
prominence models at temperatures 8, 30, and 100 kK computed with a
radiative transfer code and the prominence visible-light (VL) emission
due to Thomson scattering on the prominence electrons. We compute
various useful relations at prominence line-of-sight velocities of 0,
100, and 300 km s−1 for 20 Å wide flat filter and three
Gaussian filters with a full-width at half-maximum (FWHM) equal to 5,
10, and 20 Å to show the relative brightness contribution of the He I
D3 line and the prominence VL to the visibility in a given
narrow-band filter. We also discuss possible signal contamination by Na
I D1 and D2 lines, which otherwise may be useful
to detect comets. Our results mainly show that i) an optimal narrow-band
filter should be flat or somewhere between flat and Gaussian with an
FWHM of 20 Å in order to detect fast-moving prominence structures,
ii) the maximum emission in the He I D3 line is at 30 kK
and the minimal at 100 kK, and iii) the ratio of emission in the He I
D3 line to the VL emission can provide a useful diagnostic
for the temperature of prominence structures. This ratio is up to 10
for hot prominence structures, up to 100 for cool structures, and up
to 1000 for warm structures.
Title: Comprehensive Analysis of the Geoeffective Solar Event
of 21 June 2015: Effects on the Magnetosphere, Plasmasphere, and
Ionosphere Systems
Authors: Piersanti, Mirko; Alberti, Tommaso; Bemporad, Alessandro;
Berrilli, Francesco; Bruno, Roberto; Capparelli, Vincenzo; Carbone,
Vincenzo; Cesaroni, Claudio; Consolini, Giuseppe; Cristaldi, Alice;
Del Corpo, Alfredo; Del Moro, Dario; Di Matteo, Simone; Ermolli,
Ilaria; Fineschi, Silvano; Giannattasio, Fabio; Giorgi, Fabrizio;
Giovannelli, Luca; Guglielmino, Salvatore Luigi; Laurenza, Monica;
Lepreti, Fabio; Marcucci, Maria Federica; Martucci, Matteo; Mergè,
Matteo; Pezzopane, Michael; Pietropaolo, Ermanno; Romano, Paolo;
Sparvoli, Roberta; Spogli, Luca; Stangalini, Marco; Vecchio, Antonio;
Vellante, Massimo; Villante, Umberto; Zuccarello, Francesca; Heilig,
Balázs; Reda, Jan; Lichtenberger, János
Bibcode: 2017SoPh..292..169P
Altcode:
A full-halo coronal mass ejection (CME) left the Sun on 21 June 2015
from active region (AR) NOAA 12371. It encountered Earth on 22 June
2015 and generated a strong geomagnetic storm whose minimum Dst value
was −204 nT. The CME was associated with an M2-class flare observed
at 01:42 UT, located near disk center (N12 E16). Using satellite data
from solar, heliospheric, and magnetospheric missions and ground-based
instruments, we performed a comprehensive Sun-to-Earth analysis. In
particular, we analyzed the active region evolution using ground-based
and satellite instruments (Big Bear Solar Observatory (BBSO), Interface
Region Imaging Spectrograph (IRIS), Hinode, Atmospheric Imaging Assembly
(AIA) onboard the Solar Dynamics Observatory (SDO), Reuven Ramaty High
Energy Solar Spectroscopic Imager (RHESSI), covering Hα , EUV, UV, and
X-ray data); the AR magnetograms, using data from SDO/Helioseismic and
Magnetic Imager (HMI); the high-energy particle data, using the Payload
for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA)
instrument; and the Rome neutron monitor measurements to assess the
effects of the interplanetary perturbation on cosmic-ray intensity. We
also evaluated the 1 - 8 Å soft X-ray data and the ∼1 MHz type III
radio burst time-integrated intensity (or fluence) of the flare in order
to predict the associated solar energetic particle (SEP) event using
the model developed by Laurenza et al. (Space Weather7(4), 2009). In
addition, using ground-based observations from lower to higher latitudes
(International Real-time Magnetic Observatory Network (INTERMAGNET) and
European Quasi-Meridional Magnetometer Array (EMMA)), we reconstructed
the ionospheric current system associated with the geomagnetic
sudden impulse (SI). Furthermore, Super Dual Auroral Radar Network
(SuperDARN) measurements were used to image the global ionospheric
polar convection during the SI and during the principal phases of
the geomagnetic storm. In addition, to investigate the influence of
the disturbed electric field on the low-latitude ionosphere induced
by geomagnetic storms, we focused on the morphology of the crests
of the equatorial ionospheric anomaly by the simultaneous use of the
Global Navigation Satellite System (GNSS) receivers, ionosondes, and
Langmuir probes onboard the Swarm constellation satellites. Moreover,
we investigated the dynamics of the plasmasphere during the different
phases of the geomagnetic storm by examining the time evolution of
the radial profiles of the equatorial plasma mass density derived from
field line resonances detected at the EMMA network (1.5 <L <6.5
). Finally, we present the general features of the geomagnetic response
to the CME by applying innovative data analysis tools that allow us
to investigate the time variation of ground-based observations of the
Earth's magnetic field during the associated geomagnetic storm.
Title: Hot prominence detected in the core of a coronal mass
ejection. II. Analysis of the C III line detected by SOHO/UVCS
Authors: Jejčič, S.; Susino, R.; Heinzel, P.; Dzifčáková, E.;
Bemporad, A.; Anzer, U.
Bibcode: 2017A&A...607A..80J
Altcode:
Context. We study the physics of erupting prominences in the core
of coronal mass ejections (CMEs) and present a continuation of a
previous analysis.
Aims: We determine the kinetic temperature
and microturbulent velocity of an erupting prominence embedded in the
core of a CME that occurred on August 2, 2000 using the Ultraviolet
Coronagraph and Spectrometer observations (UVCS) on board the Solar
and Heliospheric Observatory (SOHO) simultaneously in the hydrogen
Lα and C III lines. We develop the non-LTE (departures from the local
thermodynamic equilibrium - LTE) spectral diagnostics based on Lα and
Lβ measured integrated intensities to derive other physical quantities
of the hot erupting prominence. Based on this, we synthesize the C
III line intensity to compare it with observations.
Methods:
Our method is based on non-LTE modeling of eruptive prominences. We
used a general non-LTE radiative-transfer code only for optically thin
prominence points because optically thick points do not allow the
direct determination of the kinetic temperature and microturbulence
from the line profiles. The input parameters of the code were the
kinetic temperature and microturbulent velocity derived from the Lα
and C III line widths, as well as the integrated intensity of the Lα
and Lβ lines. The code runs in three loops to compute the radial flow
velocity, electron density, and effective thickness as the best fit
to the Lα and Lβ integrated intensities within the accuracy defined
by the absolute radiometric calibration of UVCS data.
Results:
We analyzed 39 observational points along the whole erupting prominence
because for these points we found a solution for the kinetic temperature
and microturbulent velocity. For these points we ran the non-LTE code to
determine best-fit models. All models with τ0(Lα) ≤ 0.3
and τ0(C III) ≤ 0.3 were analyzed further, for which we
computed the integrated intensity of the C III line using a two-level
atom. The best agreement between computed and observed integrated
intensity led to 30 optically thin points along the prominence. The
results are presented as histograms of the kinetic temperature,
microturbulent velocity, effective thickness, radial flow velocity,
electron density, and gas pressure. We also show the relation between
the microturbulence and kinetic temperature together with a scatter plot
of computed versus observed C III integrated intensities and the ratio
of the computed to observed C III integrated intensities versus kinetic
temperature.
Conclusions: The erupting prominence embedded in
the CME is relatively hot with a low electron density, a wide range of
effective thicknesses, a rather narrow range of radial flow velocities,
and a microturbulence of about 25 km s-1. This analysis shows
a disagreement between observed and synthetic intensities of the C III
line, the reason for which most probably is that photoionization is
neglected in calculations of the ionization equilibrium. Alternatively,
the disagreement might be due to non-equilibrium processes.
Title: METIS: the visible and UV coronagraph for solar orbiter
Authors: Romoli, M.; Landini, F.; Antonucci, E.; Andretta, V.;
Berlicki, A.; Fineschi, S.; Moses, J. D.; Naletto, G.; Nicolosi, P.;
Nicolini, G.; Spadaro, D.; Teriaca, L.; Baccani, C.; Focardi, M.;
Pancrazzi, M.; Pucci, S.; Abbo, L.; Bemporad, A.; Capobianco, G.;
Massone, G.; Telloni, D.; Magli, E.; Da Deppo, V.; Frassetto, F.;
Pelizzo, M. G.; Poletto, L.; Uslenghi, M.; Vives, S.; Malvezzi, M.
Bibcode: 2017SPIE10563E..1MR
Altcode:
METIS coronagraph is designed to observe the solar corona with an
annular field of view from 1.5 to 2.9 degrees in the visible broadband
(580-640 nm) and in the UV HI Lyman-alpha, during the Sun close
approaching and high latitude tilting orbit of Solar Orbiter. The
big challenge for a coronagraph is the stray light rejection. In
this paper after a description of the present METIS optical design,
the stray light rejection design is presented in detail together with
METIS off-pointing strategies throughout the mission. Data shown in this
paper derive from the optimization of the optical design performed with
Zemax ray tracing and from laboratory breadboards of the occultation
system and of the polarimeter.
Title: Study of the early phase of a Coronal Mass Ejection driven
shock in EUV images
Authors: Frassati, Federica; Susino, Roberto; Mancuso, Salvatore;
Bemporad, Alessandro
Bibcode: 2017Ap&SS.362..194F
Altcode:
The November 1st, 2014 prominence eruption (associated with a C2.7
class flare) resulted in a fast, partial-halo Coronal Mass Ejection
(CME). During its early propagation, the CME produced a type II radio
burst (seen by the Bruny Island Radio Spectrometer) starting around
04:57 UT when the front entered into the LASCO/C2 field of view (FOV)
and the top of the CME front was at the heliocentric distance of about
2.5 R_{⊙}. In order to identify the source of the type II radio burst,
we studied the kinematic of the eruption with EUV images acquired by
SDO/AIA. Profiles of the observed EUV front speed have been compared
with the Alfvén speed profiles derived by combining the plasma electron
densities obtained from Emission Measure analysis and model magnetic
fields extrapolated on the plane of the sky. Our results show that the
northern half of the front became super-Alfvénic at approximately the
same time when the type-II radio burst started. A comparison between
the starting frequency of the type II emission and the frequencies
corresponding to the coronal densities of the locations where the EUV
front became super-Alfvénic suggests that the radio sources should
be located in the northern flank of the front.
Title: Constraining the pass-band of future space-based coronagraphs
for observations of solar eruptions in the FeXIV 530.3 nm "green line"
Authors: Bemporad, Alessandro; Pagano, Paolo; Giordano, Silvio;
Fineschi, Silvano
Bibcode: 2017ExA....44...83B
Altcode: 2017ExA...tmp...28B
Observations of the solar corona in the FeXIV 530.3 nm "green line"
have been very important in the past, and are planned for future
coronagraphs on-board forthcoming space missions such as PROBA-3
and Aditya. For these instruments, a very important parameter to be
optimized is the spectral width of the band-pass filter to be centred
over the "green line". Focusing on solar eruptions, motions occurring
along the line of sight will Doppler shift the line profiles producing
an emission that will partially fall out of the narrower pass-band,
while broader pass-band will provide observations with reduced
spectral purity. To address these issues, we performed numerical
(MHD) simulation of CME emission in the "green line" and produced
synthetic images assuming 4 different widths of the pass-band (Δλ =
20 Å, 10 Å, 5 Å, and 2 Å). It turns out that, as expected, during
solar eruptions a significant fraction of "green line" emission will
be lost using narrower filters; on the other hand these images will
have a higher spectral purity and will contain emission coming from
parcels of plasma expanding only along the plane of the sky. This
will provide a better definition of single filamentary features and
will help isolating single slices of plasma through the eruption, thus
reducing the problem of superposition of different features along the
line of sight and helping physical interpretation of limb events. For
these reasons, we suggest to use narrower band passes (Δλ ≤ 2 Å)
for the observations of solar eruptions with future coronagraphs.
Title: Exploring the Inner Acceleration Region of Solar Wind:
A Study Based on Coronagraphic UV and Visible Light Data
Authors: Bemporad, A.
Bibcode: 2017ApJ...846...86B
Altcode:
This work combined coronagraphic visible light (VL) and UV data
to provide with an unprecedented view of the inner corona where the
nascent solar wind is accelerated. The UV (H I Lyα) and VL (polarized
brightness) images (reconstructed with SOHO/UVCS, LASCO, and Mauna Loa
data) have been analyzed with the Doppler dimming technique to provide
for the first time daily 2D images of the radial wind speed between 1
and 6 R ⊙ over 1 month of observations. Results show that
both polar and equatorial regions are characterized at the base of the
corona by plasma outflows at speeds > 100 km s-1. The
plasma is then decelerated within ∼1.5 R ⊙ at the poles
and ∼2.0 R ⊙ at the equator, where local minima of the
expansion speeds are reached, and gently reaccelerated higher up,
reaching speeds typical of fast and slow wind components. The mass
flux is highly variable with latitude and time at the equator and more
uniform and stable over the poles. The polar flow is asymmetric, with
speeds above the south pole lower than those above the north pole. A
correlation (anticorrelation) between the wind speed and its density
is found below (above) ∼1.8 R ⊙. The 2D distribution of
forces responsible for deceleration and reacceleration of solar wind
is provided and interpreted in terms of Alfvén waves. These results
provide a possible connection between small-scale outflows reported
with other instruments at the base of the corona and bulk wind flows
measured higher up.
Title: Temporal Characterization of the Remote Sensors Response to
Radiation Damage in L2
Authors: De March, Ruben; Busonero, Deborah; Messineo, Rosario;
Bemporad, Alessandro; Vaccarino, Francesco; Fabio Mulone, Angelo;
Fonti, Andrea; Lattanzi, Mario
Bibcode: 2017arXiv170905130D
Altcode:
Remote sensors on spacecrafts acquire huge volumes of data that can be
processed for other purposes in addition to those they were designed
for. The project TECSEL2 was born for the usage of the Gaia AIM/AVU
daily pipeline output and solar events data to characterize the response
of detectors subjected to strong radiation damage within an environment
not protected by the terrestrial magnetic field, the Lagrangian point
L2, where Gaia operates. The project also aims at identifying anomalies
in the scientific output parameters and relate them to detectors
malfunctioning due to radiation damage issues correlating with solar
events occurred in the same time range. TECSEL2 actually designs and
implements a system based on big data technologies which are the state
of art in the fields of data processing and data storage. The final
goal of TECSEL2 is not only related to the Gaia project, because it
provides useful analysis techniques for generic and potentially huge
time series datasets.
Title: An improved version of the Shadow Position Sensor readout
electronics on-board the ESA PROBA-3 Mission
Authors: Noce, V.; Focardi, M.; Buckley, S.; Bemporad, A.; Fineschi,
S.; Pancrazzi, M.; Landini, F.; Baccani, C.; Capobianco, G.; Loreggia,
D.; Casti, M.; Romoli, M.; Accatino, L.; Thizy, C.; Denis, F.;
Ledent, P.
Bibcode: 2017SPIE10397E..1BN
Altcode:
PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA)
composed by two satellites flying in formation and aimed at achieving
unprecedented performance in terms of relative positioning. The mission
purpose is, in first place, technological: the repeated formation
break and acquisition during each orbit (every about twenty hours)
will be useful to demonstrate the efficacy of the closed-loop control
system in keeping the formation-flying (FF) and attitude (i.e. the
alignment with respect to the Sun) of the system. From the scientific
side, instead, the two spacecraft will create a giant instrument
about 150 m long: an externally occulted coronagraph named ASPIICS
(Association of Spacecraft for Polarimetric and Imaging Investigation of
the Corona of the Sun) dedicated to the study of the inner part of the
visible solar corona. The two satellites composing the mission are: the
Coronagraph Spacecraft (CSC), hosting the Coronagraph Instrument (CI),
and the disk-shaped (1.4 m diameter) Occulter Spacecraft (OSC). The
PROBA-3 GNC (Guidance, Navigation and Control) system will employ
several metrological subsystems to keep and retain the desired relative
position and the absolute attitude (i.e. with respect to the Sun) of
the aligned spacecraft, when in observational mode. The SPS subsystem
[5] is one of these metrological instruments. It is composed of eight
silicon photomultipliers (SiPMs), sensors operated in photovoltaic mode
[6] that will sense the penumbra light around the Instrument's pupil so
to detect any FF displacement from the nominal position. In proximity
of the CDR (Critical Design Review) phase, we describe in the present
paper the changes occurred to design in the last year in consequence
of the tests performed on the SPS Breadboard (Evaluation Board, EB)
and the SPS Development Model (DM) and that will finally lead to the
realization of the flight version of the SPS system.
Title: Test plan for the PROBA3/ASPIICS scaled model measurement
campaign
Authors: Landini, Federico; Baccani, Cristian; Vives, Sébastien;
Fineschi, Silvano; Romoli, Marco; Capobianco, Gerardo; Massone,
Giuseppe; Casti, Marta; Bemporad, Alessandro; Focardi, Mauro;
Pancrazzi, Maurizio; Loreggia, Davide; Noce, Vladimiro; Corso, Alain
Jody; Thizy, Cédric; Renotte, Etienne; Marquet, Benoît
Bibcode: 2017SPIE10397E..1CL
Altcode:
PROBA3/ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun) is the first formation flight
solar coronagraph, scheduled by ESA for a launch and currently in phase
C/D. It is constituted by two spacecraft (one hosting the occulter,
diameter 142 cm, and one with the telescope) separated by 144 m, kept
in strict alignment by means of complex active and metrology custom
systems. The stray light analysis, which is always one the most critical
work packages for a solar coronagraph, has been only theoretically
investigated so far due to the difficulty of replicating the actual
size system in a clean laboratory environment. The light diffracted
by the external occulter is the worst offender for the stray light
level on the instrument focal plane, thus there is strong interest for
scaling at least the occultation system of the coronagraph and test it
in front of a solar simulator in order to experimentally validate the
expected theoretical performance. The theory for scaling the occulter,
the occulter-pupil distance and the source dimension has been developed
and a scaled model is being manufactured. A test campaign is going to be
conducted at the OPSys facility in Torino in front of a solar simulator
(conveniently scaled). This work accounts for the description of the
scaled model laboratory set-up and of the test plan.
Title: CME-driven Shock of 2014 November 1st: EUV, Visible and
Radio Observations
Authors: Mancuso, Salvatore; Frassati, F.; Bemporad, A.; Susino, R.
Bibcode: 2017shin.confE..28M
Altcode:
Coronal shock waves are usually identified by the presence of type
II radio bursts. The association between shocks and their possible
drivers (flares and/or expanding eruption fronts) is however not
fully understood. In this work, we investigate the early expansion
phase of the 2014 November 1st Coronal Mass Ejection (CME) and relate
its kinematical properties with the associated metric type II radio
burst. Background plasma densities were derived by using SDO/AIA EUV
images in the lower corona and by inversion of SOHO/LASCO pB data
in the intermediate corona. The same data were used to infer the
kinematical properties of the expanding CME front in order to compare
its speed with the local Alfvénic speed (derived from model coronal
magnetic fields extrapolated) and retrieve the most probable location
(on the plane of the sky) along the shock front of the region emitting
the observed metric type II burst.
Title: Validating coronal magnetic field reconstruction methods
using solar wind simulations and synthetic imagery
Authors: Pinto, Rui; Rouillard, Alexis; Génot, Vincent; Amari, Tahar;
Buchlin, Eric; Arge, Nick; Sasso, Clementina; Andretta, Vincenzo;
Bemporad, Alessandro
Bibcode: 2017EGUGA..1913650P
Altcode:
We present an ongoing effort within the ESA Modeling and Data Analysis
Working Group (MADAWG) to determine automatically the magnetic
connectivity between the solar surface and any point in interplanetary
space. The goal is to produce predictions of the paths and propagation
delays of plasma and energetic particle propagation. This is a key
point for the data exploitation of the Solar Orbiter and Solar Probe
Plus missions, and for establishing connections between remote and
in-situ data. The background coronal magnetic field is currently
determined via existing surface magnetograms and PFSS extrapolations,
but the interface is ready to include different combinations of coronal
field reconstruction methods (NLFFF, Solar Models), wind models (WSA,
MULTI-VP), heliospheric models (Parker spiral, ENLIL, EUHFORIA). Some
model realisations are also based on advanced magnetograms based on
data assimilation techniques (ADAPT) and the HELCATS catalogue of
simulations. The results from the different models will be combined in
order to better assess the modelling uncertainties. The wind models
provide synthetic white-light and EUV images which are compared to
coronographic imagery, and the heliospheric models provide estimations
of synthetic in-situ data wich are compared to spacecraft data. A part
of this is work (wind modelling) is supported by the FP7 project #606692
(HELCATS).
Title: Modelling magnetic reconnection events relevant for solar
physics with the new Energy Conserving Moment Implicit Method
Authors: Boella, Elisabetta; Herrero-Gonzalez, Diego; Innocenti,
Maria Elena; Bemporad, Alessandro; Lapenta, Giovanni
Bibcode: 2017EGUGA..1918665B
Altcode:
Fully kinetic simulations of magnetic reconnection events in the
solar environment are especially challenging due to the extreme
range of spatial and temporal scales that characterises them. As
one moves from the photosphere to the chromosphere and the corona,
the temperature increases from sub eV to 10-100 eV, while the
mass density decreases from 10-4 to 10-12
kg/m3 and further. The intrinsic scales of kinetic
reconnection (inertial length and gyroradius) are tremendously smaller
than the maximum resolution available in observations. Furthermore,
no direct information is available on the size of reconnection regions,
plasmoids and reconnection fronts, while observations suggest that the
process can cascade down to very small scale te{Bemporad}. Resolving
the electron and ion scales while simulating a sufficiently large
domain is a great challenge facing solar modelling. An especially
challenging aspect is the need to consider the Debye length. The
very low temperature of the electrons and the large spatial and
temporal scales make these simulations hard to implement within
existing Particle in Cell (PIC) methods. The limit is the ratio of
the grid spacing to the Debye length. PIC methods show good stability
and energy conservation when the grid does not exceed the Debye length
too much. Semi-implicit methods te{Brackbill, Langdon} improve on this
point. Only the recently developed fully energy conserving implicit
methods have solved the problem te{Markidis, Chen}, but at a high
computational cost. Very recently, we have developed an efficient
new semi-implicit algorithm, which has been proven to conserve energy
exactly to machine precision te{Lapenta}. In this work, we illustrate
the main steps that enabled this great breakthrough and report the
implementation on a new massively parallel three dimensional PIC
code, called ECsim te{Lapenta2}. The new approach is applied to
the problem of reconnection in the solar environment. We compare
results of a simple 2D configuration similar to the so-called GEM
challenge for different ranges of electron temperature, density and
magnetic field, relative to different distances from the photosphere,
demonstrating the capability of the new code. Finally, we report on
the first results (to the authors' knowledge) of realistic magnetic
3D reconnection simulations in the solar environment, considering a
large domain sufficient to describe the interaction of large scale
dynamics with the reconnection process. A. Bemporad, ApJ 689, 572
(2008). J.U. Brackbill and D.W. Forslund, J. Comput. Phys. 46, 271
(1982). A. Langdon et al., J. Comput. Phys. 51, 107 (1983). S. Markidis and G. Lapenta, J. Comput. Phys. 230, 7037 (2011). G. Chen et al., J. Comput. Phys. 230, 7018 (2011). G. Lapenta,
arXiv preprint arXiv:1602.06326 (2016). G. Lapenta et al., arXiv
preprint arXiv:1612.08289 (2016).
Title: Determination of Coronal Mass Ejection Physical Parameters
from a Combination of Polarized Visible Light and UV Lyα Observations
Authors: Susino, R.; Bemporad, A.
Bibcode: 2016ApJ...830...58S
Altcode: 2016arXiv160901420S
Visible-light observations of Coronal Mass Ejections (CMEs) performed
with coronagraphs and heliospheric imagers (in primis on board the
Solar and Heliospheric Observatory and STEREO missions) have offered
the best way to study the kinematics and geometrical structure of
these fundamental events so far. Nevertheless, it has been widely
demonstrated that only combination of multi-wavelength data (including
X-ray spectra, EUV images, EUV-UV spectra, and radio dynamic spectra)
can provide complete information on the plasma temperature and density
distributions, non-thermal motions, magnetic fields, and other physical
parameters, for both CMEs and CME-related phenomena. In this work,
we analyze three CMEs by combining simultaneous data acquired in
the polarized visible light by the LASCO-C2 coronagraph and in the
UV H I Lyα line (1216 Å) by the UVCS spectrometer, in order to
estimate the CME plasma electron density (using the polarization-ratio
technique to infer the 3D structure of the CME) and temperature (from
the comparison between the expected and measured Lyα intensities)
along the UVCS field of view. This analysis is primarily aimed at
testing the diagnostic methods that will be applied to coronagraphic
observations of CMEs delivered by the Metis instrument on board the
next ESA-Solar Orbiter mission. We find that CME cores are usually
associated with cooler plasma (T∼ {10}6 K), and that a
significant increase of the electron temperatures is observed from
the core to the front of the CME (where T\gt {10}6.3 K),
which seems to be correlated, in all cases, with the morphological
structure of the CME as derived from visible-light images.
Title: Preliminary evaluation of the diffraction behind the PROBA
3/ASPIICS optimized occulter
Authors: Baccani, Cristian; Landini, Federico; Romoli, Marco; Taccola,
Matteo; Schweitzer, Hagen; Fineschi, Silvano; Bemporad, Alessandro;
Loreggia, Davide; Capobianco, Gerardo; Pancrazzi, Maurizio; Focardi,
Mauro; Noce, Vladimiro; Thizy, Cédric; Servaye, Jean-Sébastien;
Renotte, Etienne
Bibcode: 2016SPIE.9904E..50B
Altcode:
PROBA-3 is a technological mission of the European Space Agency
(ESA), devoted to the in-orbit demon- stration of formation flying
(FF) techniques and technologies. ASPIICS is an externally occulted
coronagraph approved by ESA as payload in the framework of the PROBA-3
mission and is currently in its C/D phase. FF offers a solution to
investigate the solar corona close the solar limb using a two-component
space system: the external occulter on one spacecraft and the optical
instrument on the other, separated by a large distance and kept in
strict alignment. ASPIICS is characterized by an inter-satellite
distance of ∼144 m and an external occulter diameter of 1.42 m. The
stray light due to the diffraction by the external occulter edge is
always the most critical offender to a coronagraph performance: the
designer work is focused on reducing the stray light and carefully
evaluating the residuals. In order to match this goal, external
occulters are usually characterized by an optimized shape along the
optical axis. Part of the stray light evaluation process is based on the
diffraction calculation with the optimized occulter and with the whole
solar disk as a source. We used the field tracing software VirtualLabTM
Fusion by Wyrowski Photonics [1] to simulate the diffraction. As a
first approach and in order to evaluate the software, we simulated
linear occulters, through as portions of the flight occulter, in order
to make a direct comparison with the Phase-A measurements [2].
Title: Characterization of the ASPIICS/OPSE metrology sub-system
and PSF centroiding procedure
Authors: Loreggia, D.; Fineschi, S.; Capobianco, G.; Bemporad,
A.; Focardi, M.; Landini, F.; Massone, G.; Casti, M.; Nicolini, G.;
Pancrazi, M.; Romoli, M.; Noce, V.; Baccani, C.; Cernica, I.; Purica,
M.; Nisulescu, M.; Thizy, C.; Servaye, J. S.; Renotte, E.
Bibcode: 2016SPIE.9904E..5OL
Altcode:
years have raised increasing interest. Many applications of astronomical
observation techniques, as coronography and interferometry get great
benefit when moved in space and the employment of diluted systems
represents a milestone to step-over in astronomical research. In
this work, we present the Optical Position Sensors Emitter (OPSE)
metrological sub-system on-board of the PROBA3. PROBA3 is an ESA
technology mission that will test in-orbit many metrology techniques for
the maintenance of a Formation Flying with two satellites, in this case
an occulter and a main satellite housing a coronagraph named ASPIICS,
kept at an average inter-distance of 144m. The scientific task is the
observation of the Sun's Corona at high spatial and temporal resolution
down to 1.08R⊙. The OPSE will monitor the relative position of the two
satellites and consists of 3 emitters positioned on the rear surface
of the occulter, that will be observed by the coronagraph itself. A
Centre of Gravity (CoG) algorithm is used to monitor the emitter's PSF
at the focal plane of the Coronagraph retrieving the Occulter position
with respect to the main spacecraft. The 3σ location target accuracy
is 300μm for lateral movement and 21cm for longitudinal movements. A
description of the characterization tests on the OPSE LED sources,
and of the design for a laboratory set-up for on ground testing is
given with a preliminary assessment of the performances expected from
the OPSE images centroiding algorithm.
Title: The satellite formation flying in lab: PROBA-3/ASPIICS
metrology subsystems test-bed
Authors: Capobianco, G.; Loreggia, D.; Fineschi, S.; Focardi, M.;
Bemporad, A.; Casti, M.; Noce, V.; Landini, F.; Baccani, C.; Pancrazzi,
M.; Romoli, M.; Massone, G.; Nicolini, G.; Buckley, S.; O'Neill, K.;
Cernica, I.; Purica, M.; Budianu, E.; Thizy, C.; Servaye, J. -S.;
Mechmech, I.; Renotte, Etienne
Bibcode: 2016SPIE.9904E..6EC
Altcode:
Formation flying is one of the most promising techniques for the
future of astronomy and astrophysics from the space. The capabilities
of the rockets strongly affect the dimensions and the weights of
telescopes and instrumentation to be launched. Telescopes composed by
several smallest satellites in formation flying, could be the key for
build big space telescopes. With this aim, the ESA PROBA-3 mission
will demonstrate the capabilities of this technology, maintaining
two satellites aligned within 1 mm (longitudinal) when the nominal
distance between the two is of around 144m. The scientific objective
of the mission is the observation of the solar corona down to 1.08
solar radii. The Coronagraph Spacecraft (CSC) will observe the Sun,
when the second spacecraft, the Occulter Spacecraft (OSC) will work
as an external occulter, eclipsing to the CSC the sun disk. The
finest metrology sub-systems, the Shadow Position Sensors (SPS) and
the Occulter Position Sensor Emitters (OPSE) identifying respectively
the CSC-Sun axis and the formation flying (i.e., CSC-OSC) axis will be
considered here. In particular, this paper is dedicated to the test-bed
for the characterization, the performance analysis and the algorithms
capabilities analysis of the both the metrology subsystems. The
test-bed is able to simulate the different flight conditions of the two
spacecraft and will give the opportunity to check the response of the
subsystems in the conditions as close as possible to the flight ones.
Title: Future space missions and ground observatory for measurements
of coronal magnetic fields
Authors: Fineschi, Silvano; Gibson, Sarah; Bemporad, Alessandro;
Zhukov, Andrei; Damé, Luc; Susino, Roberto; Larruquert, Juan
Bibcode: 2016cosp...41E.602F
Altcode:
This presentation gives an overview of the near-future perspectives for
probing coronal magnetism from space missions (i.e., SCORE and ASPIICS)
and ground-based observatory (ESCAPE). Spectro-polarimetric imaging of
coronal emission-lines in the visible-light wavelength-band provides an
important diagnostics tool of the coronal magnetism. The interpretation
in terms of Hanle and Zeeman effect of the line-polarization
in forbidden emission-lines yields information on the direction
and strength of the coronal magnetic field. As study case, this
presentation will describe the Torino Coronal Magnetograph (CorMag)
for the spectro-polarimetric observation of the FeXIV, 530.3 nm,
forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC)
Lyot filter and a LC linear polarimeter. The CorMag filter is part
of the ESCAPE experiment to be based at the French-Italian Concordia
base in Antarctica. The linear polarization by resonance scattering
of coronal permitted line-emission in the ultraviolet (UV)can be
modified by magnetic fields through the Hanle effect. Space-based
UV spectro-polarimeters would provide an additional tool for the
disgnostics of coronal magnetism. As a case study of space-borne UV
spectro-polarimeters, this presentation will describe the future upgrade
of the Sounding-rocket Coronagraphic Experiment (SCORE) to include new
generation, high-efficiency UV polarizer with the capability of imaging
polarimetry of the HI Lyman-α, 121.6 nm. SCORE is a multi-wavelength
imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and
visible-light broad-band emission of the polarized K-corona. SCORE
has flown successfully in 2009. The second lauch is scheduled in
2016. Proba-3 is the other future solar mission that would provide
the opportunity of diagnosing the coronal magnetic field. Proba-3 is
the first precision formation-flying mission to launched in 2019). A
pair of satellites will fly together maintaining a fixed configuration
as a 'large rigid structure' in space. The paired satellites will
together form a 150-m long solar coronagraph (ASPIICS) to study the
Sun's faint corona closer to the solar limb than has ever before been
achieved. High-resolution imaging in polarized visible-light of shock
waves generated by Coronal Mass Ejections would provide a diagnostics
of the magnetic field in the pre-shock ambient corona.
Title: The shadow position sensors (SPS) formation flying metrology
subsystem for the ESA PROBA-3 mission: present status and future
developments
Authors: Focardi, M.; Noce, V.; Buckley, S.; O'Neill, K.; Bemporad,
A.; Fineschi, S.; Pancrazzi, M.; Landini, F.; Baccani, C.; Capobianco,
G.; Loreggia, D.; Casti, M.; Romoli, M.; Massone, G.; Nicolini, G.;
Accatino, L.; Thizy, C.; Servaye, J. S.; Mechmech, I.; Renotte, E.
Bibcode: 2016SPIE.9904E..4ZF
Altcode:
PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed
of two formation-flying satellites, planned for their joint launch
by the end of 2018. Its main purposes have a dual nature: scientific
and technological. In particular, it is designed to observe and study
the inner part of the visible solar corona, thanks to a dedicated
coronagraph called ASPIICS (Association of Spacecraft for Polarimetric
and Imaging Investigation of the Corona of the Sun), and to demonstrate
the in-orbit formation flying (FF) and attitude control capability of
its two satellites. The Coronagraph payload on-board PROBA-3 consists
of the following parts: the Coronagraph Instrument (CI) with the Shadow
Position Sensor (SPS) on the Coronagraph Spacecraft (CSC), the Occulter
Position Sensor (OPSE) [3] [4] and the External Occulting (EO) disk
on the Occulter Spacecraft (OSC). The SPS subsystem [5] is one of the
main metrological devices of the Mission, adopted to control and to
maintain the relative (i.e. between the two satellites) and absolute
(i.e. with respect to the Sun) FF attitude. It is composed of eight
micro arrays of silicon photomultipliers (SiPMs) [6] that shall be
able to measure, with the required sensitivity and dynamic range as
asked by ESA, the penumbral light intensity on the Coronagraph entrance
pupil. With the present paper we describe the testing activities on the
SPS breadboard (BB) and Development Model (DM) as well as the present
status and future developments of this PROBA-3 metrological subsystem.
Title: Hot prominence detected in the core of a coronal mass ejection:
Analysis of SOHO/UVCS Lα and SOHO/LASCO visible-light observations
Authors: Heinzel, P.; Susino, R.; Jejčič, S.; Bemporad, A.; Anzer, U.
Bibcode: 2016A&A...589A.128H
Altcode:
Context. The paper deals with the physics of erupting prominences in
the core of coronal mass ejections (CME).
Aims: We determine the
physical parameters of an erupting prominence embedded in the core of a
CME using SOHO/UVCS hydrogen Lα and Lβ lines and SOHO/LASCO visible
light observations. In particular we analyze the CME event observed
on August 2, 2000. We develop the non-LTE (NLTE; I.e. considering
departures from the local thermodynamic equilibrium - LTE) spectral
diagnostics based on Lα and visible light observations.
Methods:
Our method is based on 1D NLTE modeling of eruptive prominences and
takes into account the effect of large flow velocities, which reach
up to 300 km s-1 for the studied event (the so-called
Doppler dimming). The NLTE radiative-transfer method can be used
for both optically thin and thick prominence structures. We combine
spectroscopic UVCS observations of an erupting prominence in the core
of a CME with visible light images from LASCO-C2 in order to derive the
geometrical parameters like projected thickness and velocity, together
with the effective temperature and column density of electrons. These
are then used to constrain our NLTE radiative transfer modeling which
provides the kinetic temperature, microturbulent velocity, gas pressure,
ionization degree, the line opacities, and the prominence effective
thickness (geometrical filling factor).
Results: Analysis was
made for 69 observational points (spatial pixels) inside the whole
erupting prominence. Roughly one-half of them show a non-negligible Lα
optical thickness for flow velocity 300 km s-1 and about
one-third for flow velocity 150 km s-1. All pixels with
Lατ0 ≤ 0.3 have been considered for further analysis,
which is presented in the form of statistical distributions (histograms)
of various physical quantities such as the kinetic temperature, gas
pressure, and electron density for two representative flow velocities
(150 and 300 km s-1) and non-zero microturbulence. For
two pixels co-temporal LASCO visible-light data are also available,
which further constrains the diagnostics of the electron density and
effective thickness. Detailed NLTE modeling is presented for various
sets of input parameters.
Conclusions: The studied CME event
shows that the erupting prominence expands to large volumes, meaning
that it is a low-pressure structure with low electron densities and
high temperatures. This analysis provides a basis for future diagnostics
using the METIS coronagraph on board the Solar Orbiter mission.
Title: Measuring coronal magnetic fields with remote sensing
observations of shock waves
Authors: Bemporad, Alessandro; Susino, Roberto; Frassati, Federica;
Fineschi, Silvano
Bibcode: 2016FrASS...3...17B
Altcode: 2016arXiv160805536B
Recent works demonstrated that remote sensing observations of shock
waves propagating into the corona and associated with major solar
eruptions can be used to derive the strength of coronal magnetic
fields met by the shock over a very large interval of heliocentric
distances and latitudes. This opinion article will summarize most
recent results obtained on this topic and will discuss the weaknesses
and strengths of these techniques to open a constructive discussion
with the scientific community.
Title: Study of sungrazing comets with space-based coronagraphs:
New possibilities offered by METIS on board Solar Orbiter
Authors: Bemporad, A.; Giordano, S.; Raymond, J. C.; Knight, M. M.
Bibcode: 2015AdSpR..56.2288B
Altcode:
Thanks to the launch of SOHO in the end of 1995 and to the continuous
monitoring of the white light (WL) corona offered by the LASCO
coronagraphs, it was discovered that sungrazing comets are much
more common than previously thought. More than 2800 comets have been
discovered so far over nearly 20 years, hence slightly less than a
comet every 2 days is observed by coronagraphs. The WL emission seen
by SOHO/LASCO and more recently also by the STEREO/SECCHI instruments
provides information not only on the comet orbits (hence on their
origin), but also on the dust-tail formation, dust-tail disconnection,
occurrence of nucleus fragmentation and nucleus disintegration
processes. Very interestingly, a few sungrazing comets have also
been observed spectroscopically in the UV by the SOHO UV Coronagraph
Spectrometer (UVCS), and the strong emission observed in the HI Lyman-
α 1216 Å line provides direct information also on the water outgassing
rate, tail chemical composition, nucleus size, and occurrence of nucleus
fragmentation. Moreover, the UV cometary emission provides a new method
to estimate physical parameters of the coronal plasma met by the comet
(like electron density, proton temperature and solar wind velocity),
so that these comets can be considered as "local probes" for the solar
corona. Unique observations of comets will be provided in the near
future by the METIS coronagraph on board the Solar Orbiter mission:
METIS will simultaneously observe the corona in WL and in UV (HI Lyman-
α), hence it will be a unique instrument capable of studying at the
same time the transiting comets and the solar corona. Previous results
and new possibilities offered by METIS on these topics are summarized
and discussed here.
Title: Future capabilities of CME polarimetric 3D reconstructions
with the METIS instrument: A numerical test
Authors: Pagano, P.; Bemporad, A.; Mackay, D. H.
Bibcode: 2015A&A...582A..72P
Altcode: 2015arXiv150805276P
Context. Understanding the 3D structure of coronal mass ejections
(CMEs) is crucial for understanding the nature and origin of solar
eruptions. However, owing to the optical thinness of the solar corona we
can only observe the line of sight integrated emission. As a consequence
the resulting projection effects hide the true 3D structure of CMEs. To
derive information on the 3D structure of CMEs from white-light (total
and polarized brightness) images, the polarization ratio technique is
widely used. The soon-to-be-launched METIS coronagraph on board Solar
Orbiter will use this technique to produce new polarimetric images.
Aims: This work considers the application of the polarization ratio
technique to synthetic CME observations from METIS. In particular we
determine the accuracy at which the position of the centre of mass,
direction and speed of propagation, and the column density of the CME
can be determined along the line of sight.
Methods: We perform a
3D MHD simulation of a flux rope ejection where a CME is produced. From
the simulation we (i) synthesize the corresponding METIS white-light
(total and polarized brightness) images and (ii) apply the polarization
ratio technique to these synthesized images and compare the results with
the known density distribution from the MHD simulation. In addition,
we use recent results that consider how the position of a single blob
of plasma is measured depending on its projected position in the plane
of the sky. From this we can interpret the results of the polarization
ratio technique and give an estimation of the error associated with
derived parameters.
Results: We find that the polarization ratio
technique reproduces with high accuracy the position of the centre
of mass along the line of sight. However, some errors are inherently
associated with this determination. The polarization ratio technique
also allows information to be derived on the real 3D direction of
propagation of the CME. The determination of this is of fundamental
importance for future space weather forecasting. In addition, we find
that the column density derived from white-light images is accurate
and we propose an improved technique where the combined use of the
polarization ratio technique and white-light images minimizes the
error in the estimation of column densities. Moreover, by applying the
comparison to a set of snapshots of the simulation we can also assess
the errors related to the trajectory and the expansion of the CME.
Conclusions: Our method allows us to thoroughly test the performance
of the polarization ratio technique and allows a determination of the
errors associated with it, which means that it can be used to quantify
the results from the analysis of the forthcoming METIS observations in
white light (total and polarized brightness). Finally, we describe a
satellite observing configuration relative to the Earth that can allow
the technique to be efficiently used for space weather predictions. A movie attached to Fig. 15 is available in electronic form at http://www.aanda.org
Title: Physical Conditions of Coronal Plasma at the Transit of a
Shock Driven by a Coronal Mass Ejection
Authors: Susino, R.; Bemporad, A.; Mancuso, S.
Bibcode: 2015ApJ...812..119S
Altcode: 2015arXiv150909131B; 2015arXiv150909131S
We report here on the determination of plasma physical parameters
across a shock driven by a coronal mass ejection using white light
(WL) coronagraphic images and radio dynamic spectra (RDS). The event
analyzed here is the spectacular eruption that occurred on 2011 June
7, a fast CME followed by the ejection of columns of chromospheric
plasma, part of them falling back to the solar surface, associated
with a M2.5 flare and a type-II radio burst. Images acquired by the
Solar and Heliospheric Observatory/LASCO coronagraphs (C2 and C3)
were employed to track the CME-driven shock in the corona between
2-12 R⊙ in an angular interval of about 110°. In this
interval we derived two-dimensional (2D) maps of electron density,
shock velocity, and shock compression ratio, and we measured the shock
inclination angle with respect to the radial direction. Under plausible
assumptions, these quantities were used to infer 2D maps of shock Mach
number MA and strength of coronal magnetic fields at the
shock's heights. We found that in the early phases (2-4 R⊙)
the whole shock surface is super-Alfvénic, while later on (i.e.,
higher up) it becomes super-Alfvénic only at the nose. This is in
agreement with the location for the source of the observed type-II
burst, as inferred from RDS combined with the shock kinematic and
coronal densities derived from WL. For the first time, a coronal shock
is used to derive a 2D map of the coronal magnetic field strength over
intervals of 10 R⊙ altitude and ∼110° latitude.
Title: The Shadow Positioning Sensors (SPS) for formation flying
metrology on-board the ESA-PROBA3 mission
Authors: Bemporad, A.; Baccani, C.; Capobianco, G.; Fineschi, S.;
Focardi, M.; Landini, F.; Loreggia, D.; Massone, G.; Nicolini, G.;
Noce, V.; Pancrazzi, M.; Romoli, M.; Buckley, S.; O'Neill, K.; Renotte,
E.; Servaye, J. S.; Thizy, C.
Bibcode: 2015SPIE.9604E..0CB
Altcode:
PROBA3 is an ESA technology mission devoted to in-orbit demonstration
of the formation flight (FF) technique, with two satellites kept at an
average inter-distance by about 144 m. The ASPIIC instrument on-board
PROBA3 will be the first ever space-based coronagraph working on
one satellite and having the external occulter located on the second
satellite, thus allowing observations of the inner solar corona with
unprecedented reduction of stray light. During the observational
periods, the FF configuration will be maintained with very high
precision and two different techniques will be implemented: the use of
Shadow Positioning Sensors (SPS) located on the Coronagraph Spacecraft
(diodes measuring the penumbral light intensity on the entrance pupil
plane) and the use of Occulter Position Sensor LEDs (OPSE) located
on the back side of the Occulter Spacecraft. This paper will review
the main instrumental requirements on the SPS needed to determine the
3-dimensional relative positioning of the two PROBA3 satellites with
high precision.
Title: OPSE metrology system onboard of the PROBA3 mission of ESA
Authors: Loreggia, D.; Bemporad, A.; Capobianco, G.; Fineschi, S.;
Focardi, M.; Landini, F.; Massone, G.; Nicolini, G.; Pancrazzi, M.;
Romoli, M.; Cernica, I.; Purica, M.; Budianu, E.; Thizy, C.; Renotte,
E.; Servaye, J. S.
Bibcode: 2015SPIE.9604E..0FL
Altcode:
In recent years, ESA has assessed several mission involving formation
flying (FF). The great interest in this topics is mainly driven by the
need for moving from ground to space the location of next generation
astronomical telescopes overcoming most of the critical problems,
as example the construction of huge baselines for interferometry. In
this scenario, metrology systems play a critical role. PROBA3 is
an ESA technology mission devoted to in-orbit demonstration of the
FF technique, with two satellites, an occulter and a main satellite
housing a coronagraph named ASPIICS, kept at an average inter-distance
by about 144m, with micron scale accuracy. The guiding proposal is
to test several metrology solution for spacecraft alignment, with the
important scientific return of having observation of Corona at never
reached before angular field. The Shadow Position Sensors (SPS), and the
Optical Position Emitters Sensors (OPSE) are two of the systems used
for FF fine tracking. The SPS are finalized to monitor the position
of the two spacecraft with respect to the Sun and are discussed in
dedicated papers presented in this conference. The OPSE will monitor
the relative position of the two satellites and consists of 3 emitters
positioned on the rear surface of the occulter, that will be observed
by the coronagraph itself. By following the evolution of the emitters
images at the focal plane the alignment of the two spacecrafts is
retrieved via dedicated centroiding algoritm. We present an overview
of the OPSE system and of the centroiding approach.
Title: Design status of ASPIICS, an externally occulted coronagraph
for PROBA-3
Authors: Renotte, Etienne; Alia, Andres; Bemporad, Alessandro;
Bernier, Joseph; Bramanti, Cristina; Buckley, Steve; Capobianco,
Gerardo; Cernica, Ileana; Dániel, Vladimir; Darakchiev, Radoslav;
Darmetko, Marcin; Debaize, Arnaud; Denis, François; Desselle,
Richard; de Vos, Lieve; Dinescu, Adrian; Fineschi, Silvano;
Fleury-Frenette, Karl; Focardi, Mauro; Fumel, Aurélie; Galano,
Damien; Galy, Camille; Gillis, Jean-Marie; Górski, Tomasz; Graas,
Estelle; Graczyk, Rafał; Grochowski, Konrad; Halain, Jean-Philippe
A.; Hermans, Aline; Howard, Russ; Jackson, Carl; Janssen, Emmanuel;
Kasprzyk, Hubert; Kosiec, Jacek; Koutchmy, Serge; Kovačičinová,
Jana; Kranitis, Nektarios; Kurowski, Michał; Ładno, Michał; Lamy,
Philippe; Landini, Federico; Lapáček, Radek; Lédl, Vít.; Liebecq,
Sylvie; Loreggia, Davide; McGarvey, Brian; Massone, Giuseppe; Melich,
Radek; Mestreau-Garreau, Agnes; Mollet, Dominique; Mosdorf, Łukasz;
Mosdorf, Michał; Mroczkowski, Mateusz; Muller, Raluca; Nicolini,
Gianalfredo; Nicula, Bogdan; O'Neill, Kevin; Orleański, Piotr;
Palau, Marie-Catherine; Pancrazzi, Maurizio; Paschalis, Antonios;
Patočka, Karel; Peresty, Radek; Popescu, Irina; Psota, Pavel; Rataj,
Miroslaw; Rautakoski, Jan; Romoli, Marco; Rybecký, Roman; Salvador,
Lucas; Servaye, Jean-Sébastien; Solomon, Cornel; Stockman, Yvan;
Swat, Arkadiusz; Thizy, Cédric; Thomé, Michel; Tsinganos, Kanaris;
Van der Meulen, Jim; Van Vooren, Nico; Vit, Tomáš; Walczak, Tomasz;
Zarzycka, Alicja; Zender, Joe; Zhukov, Andrei
Bibcode: 2015SPIE.9604E..0AR
Altcode:
The "sonic region" of the Sun corona remains extremely difficult to
observe with spatial resolution and sensitivity sufficient to understand
the fine scale phenomena that govern the quiescent solar corona,
as well as phenomena that lead to coronal mass ejections (CMEs),
which influence space weather. Improvement on this front requires
eclipse-like conditions over long observation times. The space-borne
coronagraphs flown so far provided a continuous coverage of the external
parts of the corona but their over-occulting system did not permit to
analyse the part of the white-light corona where the main coronal mass
is concentrated. The proposed PROBA-3 Coronagraph System, also known
as ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun), with its novel design, will
be the first space coronagraph to cover the range of radial distances
between ~1.08 and 3 solar radii where the magnetic field plays a crucial
role in the coronal dynamics, thus providing continuous observational
conditions very close to those during a total solar eclipse. PROBA-3
is first a mission devoted to the in-orbit demonstration of precise
formation flying techniques and technologies for future European
missions, which will fly ASPIICS as primary payload. The instrument
is distributed over two satellites flying in formation (approx. 150m
apart) to form a giant coronagraph capable of producing a nearly perfect
eclipse allowing observing the sun corona closer to the rim than ever
before. The coronagraph instrument is developed by a large European
consortium including about 20 partners from 7 countries under the
auspices of the European Space Agency. This paper is reviewing the
recent improvements and design updates of the ASPIICS instrument as
it is stepping into the detailed design phase.
Title: Formation flying metrology for the ESA-PROBA3 mission:
the Shadow Position Sensors (SPS) silicon photomultipliers (SiPMs)
readout electronics
Authors: Focardi, M.; Bemporad, A.; Buckley, S.; O'Neill, K.; Fineschi,
S.; Noce, V.; Pancrazzi, M.; Landini, F.; Baccani, C.; Capobianco,
G.; Romoli, M.; Loreggia, D.; Nicolini, G.; Massone, G.; Thizy, C.;
Servaye, J. S.; Renotte, E.
Bibcode: 2015SPIE.9604E..0DF
Altcode:
The European Space Agency (ESA) is planning to launch in 2018 the PROBA3
Mission, designed to demonstrate the inorbit formation flying (FF)
attitude capability of its two satellites and to observe the inner part
of the visible solar corona as the main scientific objective. The solar
corona will be observed thanks to the presence on the first satellite,
facing the Sun, of an external occulter producing an artificial eclipse
of the Sun disk. The second satellite will carry on the coronagraph
telescope and the digital camera system in order to perform imaging
of the inner part of the corona in visible polarized light, from
1.08 R⦿ up to about 3 R⦿. One of the main
metrological subsystems used to control and to maintain the relative
(i.e. between the two satellites) and absolute (i.e. with respect to
the Sun) FF attitude is the Shadow Position Sensor (SPS) assembly. It
is composed of eight micro arrays of silicon photomultipliers (SiPMs)
able to measure with the required sensitivity and dynamic range the
penumbral light intensity on the Coronagraph entrance pupil. In the
following of the present paper we describe the overall SPS subsystem
and its readout electronics with respect to the capability to satisfy
the mission requirements, from the light conversion process on board the
silicon-based SPS devices up to the digital signal readout and sampling.
Title: Significance of the occulter diffraction for the PROBA3/ASPIICS
formation flight metrology
Authors: Landini, Federico; Bemporad, Alessandro; Focardi, Mauro;
Fineschi, Silvano; Romoli, Marco; Pancrazzi, Maurizio; Baccani,
Cristian; Capobianco, Gerardo; Loreggia, Davide; Nicolini,
Gianalfredo; Massone, Giuseppe; Noce, Vladimiro; Thizy, Cédric;
Servaye, Jean-Sébastien; Renotte, Etienne
Bibcode: 2015SPIE.9604E..0EL
Altcode:
PROBA-3/ASPIICS is a formation flying coronagraph selected by ESA and
currently in its C/D phase. It is constituted by two spacecrafts (OSC,
Occulter SpaceCraft, carrying the occulter, diameter 142 cm, and CSC,
Coronagraph SpaceCraft, with the telescope) separated by ~144 m, kept
in strict alignment by means of an active custom system. The alignment
active system most critical components are the Shadow Positioning
Sensors (SPS), a series of Si-PM (Silicon Photomultiplier) measuring
the penumbra generated by the occulter. The arrangement of the SPSs
around the telescope entrance aperture is defined as a trade-off between
mechanical constraints and maximum sensitivity to misalignments. The
signal detected by the SPSs can be approximately simulated with a
geometrical analysis based on the variation of the penumbra generated
by the external occulter. The stray light generated by the diffraction
from the external occulter may affect the SPSs signal. It is mandatory
to carefully evaluate its level in order to refine the active alignment
adjustment algorithm. This work is dedicated to the description of the
preliminary investigation performed in order to evaluate the impact
of the diffraction on the SPSs signal.
Title: Plasma Physical Parameters along CME-driven
Shocks. II. Observation-Simulation Comparison
Authors: Bacchini, F.; Susino, R.; Bemporad, A.; Lapenta, G.
Bibcode: 2015ApJ...809...58B
Altcode:
In this work, we compare the spatial distribution of the
plasma parameters along the 1999 June 11 coronal mass ejection
(CME)-driven shock front with the results obtained from a CME-like
event simulated with the FLIPMHD3D code, based on the FLIP-MHD
particle-in-cell method. The observational data are retrieved from
the combination of white-light coronagraphic data (for the upstream
values) and the application of the Rankine-Hugoniot equations (for
the downstream values). The comparison shows a higher compression
ratio X and Alfvénic Mach number MA at the shock nose,
and a stronger magnetic field deflection d toward the flanks,
in agreement with observations. Then, we compare the spatial
distribution of MA with the profiles obtained from the
solutions of the shock adiabatic equation relating MA,
X, and {θ }{Bn} (the angle between the upstream magnetic
field and the shock front normal) for the special cases of parallel
and perpendicular shock, and with a semi-empirical expression for
a generically oblique shock. The semi-empirical curve approximates
the actual values of MA very well, if the effects of a
non-negligible shock thickness {δ }{sh} and plasma-to
magnetic pressure ratio {β }u are taken into account
throughout the computation. Moreover, the simulated shock turns out to
be supercritical at the nose and sub-critical at the flanks. Finally,
we develop a new one-dimensional Lagrangian ideal MHD method based on
the GrAALE code, to simulate the ion-electron temperature decoupling
due to the shock transit. Two models are used, a simple solar wind
model and a variable-γ model. Both produce results in agreement with
observations, the second one being capable of introducing the physics
responsible for the additional electron heating due to secondary effects
(collisions, Alfvén waves, etc.).
Title: Physical properties of solar polar jets. A statistical study
with Hinode XRT data
Authors: Paraschiv, A. R.; Bemporad, A.; Sterling, A. C.
Bibcode: 2015A&A...579A..96P
Altcode: 2015arXiv150507191P
Aims: The target of this work is to investigate the physical
nature of polar jets in the solar corona and their possible contribution
to coronal heating and solar wind flow based on the analysis of
X-ray images acquired by the Hinode XRT telescope. We estimate the
different forms of energy associated with many of these small-scale
eruptions, in particular the kinetic energy and enthalpy.
Methods: Two Hinode XRT campaign datasets focusing on the two polar
coronal holes were selected to analyze the physical properties of
coronal jets; the analyzed data were acquired using a series of
three XRT filters. Typical kinematical properties (e.g., length,
thickness, lifetime, ejection rate, and velocity) of 18 jets are
evaluated from the observed sequences, thus providing information
on their possible contribution to the fast solar wind flux escaping
from coronal holes. Electron temperatures and densities of polar-jet
plasmas are also estimated using ratios of the intensities observed
in different filters.
Results: We find that the largest amount
of energy eventually provided to the corona is thermal. The energy
due to waves may also be significant, but its value is comparatively
uncertain. The kinetic energy is lower than thermal energy, while other
forms of energy are comparatively low. Lesser and fainter events seem
to be hotter, thus the total contribution by polar jets to the coronal
heating could have been underestimated so far. The kinetic energy flux
is usually around three times smaller than the enthalpy counterpart,
implying that this energy is converted into plasma heating more than in
plasma acceleration. This result suggests that the majority of polar
jets are most likely not escaping from the Sun and that only cooler
ejections could possibly have enough kinetic energy to contribute to
the total solar wind flow.
Title: Uncertainties in polarimetric 3D reconstructions of coronal
mass ejections
Authors: Bemporad, A.; Pagano, P.
Bibcode: 2015A&A...576A..93B
Altcode: 2015arXiv150300314B
Aims: The aim of this work is to quantify the uncertainties in
the three-dimensional (3D) reconstruction of the location of coronal
mass ejections (CMEs) obtained with the so-called polarization ratio
technique. The method takes advantage of the different distributions
along the line of sight of total (tB) and polarized (pB) brightnesses
emitted by Thomson scattering to estimate the average location of the
emitting plasma. This is particularly important to correctly identify
of CME propagation angles and unprojected velocities, thus allowing
better capabilities for space weather forecastings.
Methods:
To this end, we assumed two simple electron density distributions
along the line of sight (a constant density and Gaussian density
profiles) for a plasma blob and synthesized the expected tB and pB
for different distances z of the blob from the plane of the sky and
different projected altitudes ρ. Reconstructed locations of the
blob along the line of sight were thus compared with the real ones,
allowing a precise determination of uncertainties in the method.
Results: Results show that, independently of the analytical density
profile, when the blob is centered at a small distance from the plane
of the sky (i.e. for limb CMEs) the distance from the plane of the sky
starts to be significantly overestimated. Polarization ratio technique
provides the line-of-sight position of the center of mass of what we
call folded density distribution, given by reflecting and summing in
front of the plane of the sky the fraction of density profile located
behind that plane. On the other hand, when the blob is far from the
plane of the sky, but with very small projected altitudes (i.e. for
halo CMEs, ρ< 1.4R⊙), the inferred distance from that
plane is significantly underestimated. Better determination of the
real blob position along the line of sight is given for intermediate
locations, and in particular when the blob is centered at an angle of
20° from the plane of the sky.
Conclusions: These result have
important consequences not only for future 3D reconstruction of CMEs
with polarization ratio technique, but also for the design of future
coronagraphs aimed at providing a continuous monitoring of halo-CMEs
for space weather prediction purposes.
Title: ASPIICS: an externally occulted coronagraph for PROBA-3:
Design evolution
Authors: Renotte, Etienne; Baston, Elena Carmen; Bemporad,
Alessandro; Capobianco, Gerardo; Cernica, Ileana; Darakchiev,
Radoslav; Denis, François; Desselle, Richard; De Vos, Lieve;
Fineschi, Silvano; Focardi, Mauro; Górski, Tomasz; Graczyk, Rafał;
Halain, Jean-Philippe; Hermans, Aline; Jackson, Carl; Kintziger,
Christian; Kosiec, Jacek; Kranitis, Nektarios; Landini, Federico;
Lédl, Vít.; Massone, Giuseppe; Mazzoli, Alexandra; Melich, Radek;
Mollet, Dominique; Mosdorf, Michał; Nicolini, Gianalfredo; Nicula,
Bogdan; Orleański, Piotr; Palau, Marie-Catherine; Pancrazzi, Maurizio;
Paschalis, Antonis; Peresty, Radek; Plesseria, Jean-Yves; Rataj,
Miroslaw; Romoli, Marco; Thizy, Cédric; Thomé, Michel; Tsinganos,
Kanaris; Wodnicki, Ryszard; Walczak, Tomasz; Zhukov, Andrei
Bibcode: 2014SPIE.9143E..2MR
Altcode:
PROBA-3 is a mission devoted to the in-orbit demonstration of
precise formation flying techniques and technologies for future ESA
missions. PROBA-3 will fly ASPIICS (Association de Satellites pour
l'Imagerie et l'Interferométrie de la Couronne Solaire) as primary
payload, which makes use of the formation flying technique to form a
giant coronagraph capable of producing a nearly perfect eclipse allowing
to observe the sun corona closer to the rim than ever before. The
coronagraph is distributed over two satellites flying in formation
(approx. 150m apart). The so called Coronagraph Satellite carries the
camera and the so called Occulter Satellite carries the sun occulter
disc. This paper is reviewing the design and evolution of the ASPIICS
instrument as at the beginning of Phase C/D.
Title: Polarimetric calibrations and astronomical polarimetry in
the V-band with Solar Orbiter/METIS instrument
Authors: Capobianco, Gerardo; Fineschi, Silvano; Focardi, Mauro;
Andretta, Vincenzo; Massone, Giuseppe; Bemporad, Alessandro; Romoli,
Marco; Antonucci, Ester; Naletto, Giampiero; Nicolini, Gianalfredo;
Nicolosi, Piergiorgio; Spadaro, Daniele
Bibcode: 2014SPIE.9143E..4VC
Altcode:
METIS is one of the remote sensing instruments on board the ESA-
Solar Orbiter mission, that will be launched in July 2017. The Visible
Light Channel (VLC) of the instrument is composed by an achromatic
LC-based polarimeter for the study of the linearly polarized solar
K-corona in the 580-640 nm bandpass. The laboratory calibrations with
spectropolarimetric techniques and the in-flight calibrations of this
channel, using some well knows linearly polarized stars in the FoV
of the instrument with a degree of linear polarization DOLP > 10%
are here discussed. The selection of the stars and the use of other
astronomical targets (i.e. planets, comets,…) and the opportunity
of measurements of the degree of linear polarization in the visible
bandpass of some astronomical objects (i.e. Earth, comets,…) are
also objects of this paper.
Title: On-board CME detection algorithm for the Solar Orbiter-METIS
coronagraph
Authors: Bemporad, A.; Andretta, V.; Pancrazzi, M.; Focardi, M.;
Straus, T.; Sasso, C.; Spadaro, D.; Uslenghi, M.; Antonucci, E.;
Fineschi, S.; Abbo, L.; Nicolini, G.; Landini, F.; Romoli, M.; Naletto,
G.; Nicolosi, P.
Bibcode: 2014SPIE.9152E..0KB
Altcode:
The METIS coronagraph is one of the instruments part of the payload of
the ESA - Solar Orbiter mission to be launched in 2017. The spacecraft
will operate much like a planetary encounter mission, with the main
scientific activity taking place with the remote-sensing instruments
during three 10-days intervals per orbit: optimization of the different
instrument observing modes will be crucial. One of the key scientific
targets of METIS will be the study of transient ejections of mass
through the solar corona (Coronal Mass Ejections - CMEs) and their
heliospheric evolution. METIS will provide for the first time imaging of
CMEs in two different wavelengths: VL (visible light 580- 640 nm) and UV
(Lyman-α line of HI at 121.6 nm). The detection of transient phenomena
shall be managed directly by the METIS Processing and Power Unit (MPPU)
by means of both external triggers ("flags") coming from other Solar
Orbiter instruments, and internal "flags" produced directly by the METIS
on-board software. METIS on-board algorithm for the automatic detection
of CMEs will be based on running differences between consecutive images
re-binned to very low resolution and thresholded for significant changes
over a minimum value. Given the small relative variation of white light
intensity during CMEs, the algorithm will take advantage of VL images
acquired with different polarization angles to maximize the detection
capability: possible false detections should be automatically managed
by the algorithm. The algorithm will be able to provide the CME first
detection time, latitudinal direction of propagation on the plane
of the sky (within 45 degrees), a binary flag indicating whether a
"halo CME" has been detected.
Title: Three-dimensional Stereoscopic Analysis of a Coronal Mass
Ejection and Comparison with UV Spectroscopic Data
Authors: Susino, Roberto; Bemporad, Alessandro; Dolei, Sergio
Bibcode: 2014ApJ...790...25S
Altcode: 2014arXiv1406.3210S
A three-dimensional (3D) reconstruction of the 2007 May 20 partial-halo
coronal mass ejection (CME) has been made using STEREO/EUVI and
STEREO/COR1 coronagraphic images. The trajectory and kinematics of the
erupting filament have been derived from Extreme Ultraviolet Imager
(EUVI) image pairs with the "tie-pointing" triangulation technique,
while the polarization ratio technique has been applied to COR1 data
to determine the average position and depth of the CME front along the
line of sight. This 3D geometrical information has been combined for
the first time with spectroscopic measurements of the O VI λλ1031.91,
1037.61 line profiles made with the Ultraviolet Coronagraph Spectrometer
(UVCS) on board the Solar and Heliospheric Observatory. Comparison
between the prominence trajectory extrapolated at the altitude of UVCS
observations and the core transit time measured from UVCS data made
possible a firm identification of the CME core observed in white light
and UV with the prominence plasma expelled during the CME. Results on
the 3D structure of the CME front have been used to calculate synthetic
spectral profiles of the O VI λ1031.91 line expected along the UVCS
slit, in an attempt to reproduce the measured line widths. Observed
line widths can be reproduced within the uncertainties only in the
peripheral part of the CME front; at the front center, where the
distance of the emitting plasma from the plane of the sky is greater,
synthetic widths turn out to be ~25% lower than the measured ones. This
provides strong evidence of line broadening due to plasma heating
mechanisms in addition to bulk expansion of the emitting volume.
Title: In-flight UV and polarized-VL radiometric calibrations of
the solar orbiter/METIS imaging coronagraph
Authors: Focardi, M.; Capobianco, G.; Andretta, V.; Sasso, C.; Romoli,
M.; Landini, F.; Fineschi, S.; Pancrazzi, M.; Bemporad, A.; Nicolini,
G.; Pucci, S.; Uslenghi, M.; Naletto, G.; Nicolosi, P.; Spadaro, D.;
Teriaca, L.; SchuÌhle, U. H.; Antonucci, E.
Bibcode: 2014SPIE.9144E..09F
Altcode:
METIS is an innovative inverted occulted solar coronagraph capable of
obtaining for the first time simultaneous imaging of the full corona
in linearly polarized visible-light (580-640 nm) and narrow-band
(+/- 10 nm) ultraviolet H I Ly-α (121.6 nm). It has been selected to
fly aboard the Solar Orbiter1 spacecraft, whose launch is
foreseen in July 2017. Thanks to its own capabilities and exploiting
the peculiar opportunities offered by the Solar Orbiter planned orbit,
METIS will address some of the still open issues in understanding the
physical processes in the corona and inner heliosphere. The Solar
Orbiter Nominal Mission Phase (NMP) will be characterized by three
scientific observing windows per orbit and METIS will perform at least
one in-flight calibration per observing window. The two imaging channels
of METIS will be calibrated on ground and periodically checked, verified
and re-calibrated in-flight. In particular, radiometric calibration
images will be needed to determine the absolute brightness of the solar
corona. For UV radiometric calibration a set of targets is represented
by continuum-emitting early type bright stars (e.g. A and B spectral
types) whose photospheres produce a bright far-ultraviolet continuum
spectrum stable over long timescales. These stars represent an important
reference standard not only for METIS in-flight calibrations but
also for other Solar Orbiter instruments and they will be crucial for
instruments cross-calibrations as well. For VL radiometric calibration,
a set of linearly polarized stars will be used. These targets shall
have a minimum degree of linear polarization (DoLP > 5%) and a
detectable magnitude, compatible with the instrument integration times
constrained by the desired S/N ratio and the characteristics of the
spacecraft orbit dynamics.
Title: Hardware and software architecture on board solar
orbiter/METIS: an update
Authors: Pancrazzi, M.; Focardi, M.; Nicolini, G.; Andretta, V.;
Uslenghi, M.; Magli, E.; Ricci, M.; Bemporad, A.; Spadaro, D.; Landini,
F.; Romoli, M.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolosi,
P.; Teriaca, L.
Bibcode: 2014SPIE.9144E..3FP
Altcode:
METIS, is one of the ten instruments selected to be part of the Solar
Orbiter payload; it is a coronagraph that will investigate the inner
part of the heliosphere performing imaging in the visible band and in
the hydrogen Lyman α line @ 121.6 nm. METIS has recently undergone
throughout a revision to simplify the instrument design. This paper
will provide an overview of the updated hardware and software design of
the coronagraph as presented at the Instrument Delta-Preliminary Design
Review occurred in April 2014. The current configuration foresees two
detectors, an Intensified APS for the UV channel and an APS for the
visible light equipped with a Liquid Crystal Variable Retarder (LCVR)
plate to perform broadband visible polarimetry. Each detector has a
proximity electronics generating the control and readout signals for
the sensor but the operations of the two devices are in charge of a
centralized unit, the METIS Processing and Power Unit (MPPU). The MPPU
operates the remaining electrical subsystems supplying them with power
and providing on board storage and processing capabilities. Its design
foresees the redundancy of the most critical parts, thus mitigating the
effects of possible failures of the electronics subsystems. The central
monitoring unit is also in charge of providing the communication with
the S/C, handling the telemetry and telecommand exchange with the
platform. The data acquired by the detectors shall undergo through
a preliminary on-board processing to maximize the scientific return
and to provide the necessary information to validate the results on
ground. Operations as images summing, compression and cosmic rays
monitoring and removal will be fundamental not only to mitigate the
effects of the main sources of noise on the acquired data, but also to
maximize the data volume to be transferred to the spacecraft in order to
fully exploit the limited bandwidth telemetry downlink. Finally, being
Solar Orbiter a deep-space mission, some METIS procedures have been
designed to provide the instrument an efficient autonomous behavior
in case of an immediate reaction is required as for the arising of
transient events or the occurrence of safety hazards conditions.
Title: On-board detection and removal of cosmic ray and solar
energetic particle signatures for the Solar Orbiter-METIS coronagraph
Authors: Andretta, V.; Bemporad, A.; Focardi, M.; Grimani, C.;
Landini, F.; Pancrazzi, M.; Sasso, C.; Spadaro, D.; Straus, T.;
Uslenghi, M. C.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolini,
G.; Nicolosi, P.; Romoli, M.
Bibcode: 2014SPIE.9152E..2QA
Altcode:
METIS is part of the science payload of Solar Orbiter. It is a
coronagraph designed to obtain images of the outer solar corona both in
the visible 580-640 nm band and in the UV, in a narrow band centered
around the hydrogen Lyman-α line. We describe the main features of
the procedures to remove signatures due to cosmic rays (CRs) and to
solar energetic particles (SEPs) comparing them with alternatives in
other contexts and in other solar coronagraphic missions. Our analysis
starts from a realistic assessment of the radiation environment where
the instrument is expected to operate, which is characteristic of the
interplanetary space of the inner solar system, but quite unusual for
most solar missions.
Title: Plasma Physical Parameters along Coronal-mass-ejection-driven
Shocks. I. Ultraviolet and White-light Observations
Authors: Bemporad, A.; Susino, R.; Lapenta, G.
Bibcode: 2014ApJ...784..102B
Altcode: 2014arXiv1403.0870B
In this work, UV and white-light (WL) coronagraphic data are combined
to derive the full set of plasma physical parameters along the front of
a shock driven by a coronal mass ejection. Pre-shock plasma density,
shock compression ratio, speed, and inclination angle are estimated
from WL data, while pre-shock plasma temperature and outflow velocity
are derived from UV data. The Rankine-Hugoniot (RH) equations for
the general case of an oblique shock are then applied at three
points along the front located between 2.2 and 2.6 R ⊙
at the shock nose and at the two flanks. Stronger field deflection
(by ~46°), plasma compression (factor ~2.7), and heating (factor ~12)
occur at the nose, while heating at the flanks is more moderate (factor
1.5-3.0). Starting from a pre-shock corona where protons and electrons
have about the same temperature (Tp ~ Te ~ 1.5 ×
106 K), temperature increases derived with RH equations could
better represent the proton heating (by dissipation across the shock),
while the temperature increase implied by adiabatic compression (factor
~2 at the nose, ~1.2-1.5 at the flanks) could be more representative
of electron heating: the transit of the shock causes a decoupling
between electron and proton temperatures. Derived magnetic field vector
rotations imply a draping of field lines around the expanding flux
rope. The shock turns out to be super-critical (sub-critical) at the
nose (at the flanks), where derived post-shock plasma parameters can
be very well approximated with those derived by assuming a parallel
(perpendicular) shock.
Title: Measurements with STEREO/COR1 data of drag forces acting on
small-scale blobs falling in the intermediate corona
Authors: Dolei, S.; Bemporad, A.; Spadaro, D.
Bibcode: 2014A&A...562A..74D
Altcode: 2014arXiv1401.7984D
In this work we study the kinematics of three small-scale (0.01
R⊙) blobs of chromospheric plasma falling back to the
Sun after the huge eruptive event of June 7, 2011. From a study of
3D trajectories of blobs made with the Solar TErrestrial RElations
Observatory (STEREO) data, we demonstrate the existence of a significant
drag force acting on the blobs and calculate two drag coefficients, in
the radial and tangential directions. The resulting drag coefficients
CD are between 0 and 5, comparable in the two directions,
making the drag force only a factor of 0.45-0.75 smaller than the
gravitational force. To obtain a correct determination of electron
densities in the blobs, we also demonstrate how, by combining
measurements of total and polarized brightness, the Hα contribution
to the white-light emission observed by the COR1 telescopes can be
estimated. This component is significant for chromospheric plasma,
being between 95 and 98% of the total white-light emission. Moreover,
we demonstrate that the COR1 data can be employed even to estimate
the Hα polarized component, which turns out to be in the order of a
few percent of Hα total emission from the blobs. If the drag forces
acting on small-scale blobs reported here are similar to those that
play a role during the CME propagation, our results suggest that the
magnetic drag should be considered even in the CME initiation modelling.
Title: HeMISE (Helio-Magnetism Investigation from the Sun to Earth):
a twin spacecraft mission at the Sun-Earth Lagrangian points L4 and L5
Authors: Bemporad, Alessandro; Fineschi, Silvano; Focardi, Mauro;
Landini, Federico; Romoli, Marco; Pancrazzi, Maurizio
Bibcode: 2014cosp...40E.275B
Altcode:
The Sun-Earth environment is a much more dynamic and eventful system
than the common-life experience of looking at the sky can suggest and
severe disturbances on the Earth magnetic field called geomagnetic
storms often occur. These sudden disturbances can adversely affect
the health of humans in space and in high altitude commercial
flights. Further advancing in our forecasting capabilities of these
storms will necessary requires a much deeper understanding of the
origin on the Sun and propagation in the interplanetary medium of
these disturbances. This means that we need a better understanding
of how magnetic fields are generated in the solar interior, how
their emergence through the photosphere, their storage and release
in the lower corona, and the final connection with our planet: a
mission specifically dedicated to this objective is needed. So far
measurements of the solar magnetic field are mostly restricted to the
low layers of the solar atmosphere. Extrapolation techniques underlying
numerous assumptions are used to estimate the magnetic field in the
transition region from the chromospheres to the corona and in the corona
itself. More recently, ground-based spectropolarimetry has proven to
be very useful to provide information of the coronal magnetic fields on
the plane of the sky, but there are no spacecraft providing at the same
time measurement of photospheric fields responsible for the coronal
configuration. The solution will be offered by a multi-spacecraft
mission designed to study at the same time photospheric and coronal
magnetic fields and the interplanetary evolution of generated solar
transients propagating along the Sun-Earth line. The HeMISE mission
will investigate the emission and its polarization from the extreme
ultraviolet to the white light wavelengths regimes. This will be done
by 2 twin spacecraft, carrying remote sensing and in situ instruments,
located in stable orbits around L4 and L5 Lagrangian points. Twin
spacecraft with photospheric and coronal magnetometers will open the
possibility for stereoscopic global helioseismology and will allow
for the first time to combine photospheric fields measured by one
spacecraft with coronal fields measured by the second spacrecraft
in quasi-quadrature, thus providing for the first time a continuous
coverage of solar magnetic fields through the solar atmosphere. The
main concepts of this mission will be illustrated here.
Title: A study of H I Lyman-alpha emission from prominences erupting
in the intermediate corona and possible future applications for
Solar Orbiter/METIS data
Authors: Bemporad, Alessandro; Heinzel, Petr; Jejcic, Sonja; Susino,
Roberto
Bibcode: 2014cosp...40E.273B
Altcode:
Over almost the last 20 years hundreds of Coronal Mass Ejections
(CME) have been observed by the UV Coronagraph Spectrometer (UVCS)
onboard SOHO. For many of these events a significant emission in the HI
Lyman-alpha lambda 1216 Å line was sampled during the transit across
the slit of the erupting prominences embedded in the core of CMEs. The
origin of this emission is completely different from what is typically
observed by UVCS: because of the higher density and lower temperatures
of such plasmas, the number of neutral H atoms is much larger than
under typical coronal conditions, and the plasma is generally not
optically thin at these wavelengths, as it is usually true for other
coronal structures. Hence, the observed H I Lyman-alpha emission can be
explained only if a radiative transport treatment across a moving plasma
structure is considered. Once the proper boundary conditions are derived
from the UV data, in combination with white light (WL) coronagraphic
observations (from LASCO), we will show how the temperature and
density of the erupting prominence could be derived even at large
altitudes (typically larger than 0.6 solar radii above the limb),
thus providing information on heating/cooling and ionization of the
CME core during the eruption. These results are very important in the
light of coronagraphic observations that will be provided by the METIS
instrument onboard the Solar Orbiter: because METIS will contemporary
observe the solar corona in WL and in UV (HI Lyman-alpha), it will be
possible to derive, with a technique similar to what is shown here,
very important information on prominence plasmas embedded in the core
of CMEs and crossing the METIS instrument field of view.
Title: Space- and Ground-based Coronal Spectro-Polarimetry
Authors: Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan;
Capobianco, Gerardo
Bibcode: 2014cosp...40E.868F
Altcode:
This presentation gives an overview of the near-future perspectives of
ultraviolet and visible-light spectro-polarimetric instrumentation
for probing coronal magnetism from space-based and ground-based
observatories. Spectro-polarimetric imaging of coronal emission-lines
in the visible-light wavelength-band provides an important diagnostics
tool of the coronal magnetism. The interpretation in terms of Hanle and
Zeeman effect of the line-polarization in forbidden emission-lines
yields information on the direction and strength of the coronal
magnetic field. As study case, this presentation will describe the
Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric
observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag
- consisting of a Liquid Crystal (LC) Lyot filter and a LC linear
polarimeter - has been recently installed on the Lomnicky Peak
Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag
will be presented. The linear polarization by resonance scattering
of coronal permitted line-emission in the ultraviolet (UV)can be
modified by magnetic fields through the Hanle effect. Space-based
UV spectro-polarimeters would provide an additional tool for the
disgnostics of coronal magnetism. As a case study of space-borne
UV spectro-polarimeters, this presentation will describe the future
upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to
include the capability of imaging polarimetry of the HI Lyman-alpha,
121.6 nm. SCORE is a multi-wavelength imager for the emission-lines,
HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission
of the polarized K-corona. SCORE has flown successfully in 2009. This
presentation will describe how in future re-flights SCORE could observe
the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.
Title: Investigation of CME-driven shocks with coronagraphic white
light and UV data
Authors: Bemporad, Alessandro; Susino, Roberto
Bibcode: 2014cosp...40E.272B
Altcode:
Recent studies of shocks driven by Coronal Mass Ejections have shown
that unique information on coronal plasma are provided by a combination
of white light (WL) and UV data analyses. On one hand, coronagraphic
WL images (like those provided by SOHO/LASCO) can be used to infer the
pre-shock coronal density and shock compression ratio, together with
other kinematical properties like shock projected speed and inclination
of the shock surface. On the other hand, UV intensities (like those
provided by SOHO/UVCS) provide the pre-shock plasma temperature and
outflow velocity. Then, by applying the Rankine-Hugoniot equations
for the general case of an oblique shock it is possible to infer the
pre- and post-shock magnetic field strengths and rotations of field
vector induced by the shock transit on the plane of the sky, together
with post-shock plasma temperatures and outflow velocities. The
compression ratio turns out to maximize at the shock nose, where
the shock is also supercritical, suggesting that this could be the
location for more efficient particle acceleration. The transit of the
shock surface corresponds to very strong plasma heating (factors 8 -
12), much weaker at the shock flanks: this likely represents heating
of coronal protons (whose kinetic energy is dissipated at the shock),
while electrons could be heated by adiabatic compression alone, leading
to a decoupling of temperatures across the shock. This technique seems
also very promising for applications to UV (H I Lyman-alpha) and WL
coronagraphic images that will be provided by the METIS coronagraph
onboard the future ESA-Solar Orbiter mission.
Title: Characteristics of polar coronal hole jets
Authors: Chandrashekhar, K.; Bemporad, A.; Banerjee, D.; Gupta, G. R.;
Teriaca, L.
Bibcode: 2014A&A...561A.104C
Altcode: 2013arXiv1310.8106C
Context. High spatial- and temporal-resolution images of coronal hole
regions show a dynamical environment where mass flows and jets are
frequently observed. These jets are believed to be important for the
coronal heating and the acceleration of the fast solar wind.
Aims: We studied the dynamics of two jets seen in a polar coronal hole
with a combination of imaging from EIS and XRT onboard Hinode. We
observed drift motions related to the evolution and formation of
these small-scale jets, which we tried to model as well.
Methods: Stack plots were used to find the drift and flow speeds
of the jets. A toymodel was developed by assuming that the observed
jet is generated by a sequence of single reconnection events where
single unresolved blobs of plasma are ejected along open field lines,
then expand and fall back along the same path, following a simple
ballistic motion.
Results: We found observational evidence that
supports the idea that polar jets are very likely produced by multiple
small-scale reconnections occurring at different times in different
locations. These eject plasma blobs that flow up and down with a motion
very similar to a simple ballistic motion. The associated drift speed of
the first jet is estimated to be ≈27 km s-1. The average
outward speed of the first jet is ≈171 km s-1, well below
the escape speed, hence if simple ballistic motion is considered, the
plasma will not escape the Sun. The second jet was observed in the south
polar coronal hole with three XRT filters, namely, C-poly,
Al-poly, and Al-mesh filters. Many small-scale
(≈3″-5″) fast (≈200-300 km s-1) ejections of
plasma were observed on the same day; they propagated outwards. We
observed that the stronger jet drifted at all altitudes along the
jet with the same drift speed of ≃7 km s-1. We also
observed that the bright point associated with the first jet is a
part of sigmoid structure. The time of appearance of the sigmoid
and that of the ejection of plasma from the bright point suggest
that the sigmoid is the progenitor of the jet.
Conclusions:
The enhancement in the light curves of low-temperature EIS lines in
the later phase of the jet lifetime and the shape of the jet's stack
plots suggests that the jet material falls back, and most likely cools
down. To further support this conclusion, the observed drifts were
interpreted within a scenario where reconnection progressively shifts
along a magnetic structure, leading to the sequential appearance of
jets of about the same size and physical characteristics. On this
basis, we also propose a simple qualitative model that mimics the
observations. Movies 1-3 are available in electronic form at http://www.aanda.org
Title: Study of sungrazing comets with space-based coronagraphs:
new possibilities offered by METIS on boar Solar Orbiter
Authors: Bemporad, Alessandro
Bibcode: 2014cosp...40E.274B
Altcode:
Thanks to the launch of SOHO in the end of 1995 and to the continuous
monitoring of the white light (WL) corona offered by the LASCO
coronagraphs, it was discovered that sungrazing comets are much
more common than previously thought. More than 2500 comets have been
discovered over about 17 years, hence slightly less than a comet every
2 days is observed by coronagraphs. The white light emission seen
by SOHO/LASCO and more recently also by the STEREO/SECCHI instruments
provides information not only on the comet orbits (hence on its origin),
but also on the dust-tail formation, dust-tail disconnection, occurrence
of nucleus fragmentation and nucleus disintegration processes. Very
interestingly, a few sungrazing comets have been also observed in
the UV spectra by the SOHO UV Coronagraph Spectrometer (UVCS) and
the strong emission observed in the H I Lyman-alpha lambda 1216 Å
line provided direct information also on the water outgassing rate,
tail chemical composition, nucleus size and occurrence of nucleus
fragmentations. Moreover, the UV cometary emission provides a new method
to estimate physical parameters of the coronal plasma met by the comet
(like electron density, proton temperature and solar wind velocity),
in a way that these comets can be considered as “local probes” for
the solar corona. Unique observations of comets will be provided in
the next future by the METIS coronagraph on board the Solar Orbiter
mission: METIS will contemporary observe the corona in WL and in UV
(HI Lyman-alpha), hence will be a unique instrument to study at the
same time the transiting comets and the solar corona being crossed by
the comets. Previous results and new possibilities offered by METIS
on these topics are summarized and discussed here.
Title: Solar-Sail CubeSats for Space Weather Monitoring from
Earth-Sun L-points
Authors: Fineschi, Silvano; Bemporad, Alessandro; Landini, Federico;
Vola, Nicole; Circi, Christian; Viscio, Maria Antonietta; Fumenti,
Federico
Bibcode: 2014cosp...40E.870F
Altcode:
This presentation describes the possibilities for space weather
monitoring that solar-sail CubeSats would enable from the Sun-Earth
L-points. The mission proposed consists of a 6U CubeSats system with
solar-sail propulsion to reach and orbit the L4 and L5 Earth-Sun
Lagragian points. The payload would include compact "in-situ"
instrumentation (e.g., radiation dosimeters) and a miniature
visible-light, wide-angle coronagraph (WACor). The WACor observations
of Coronal Mass Ejections (CMEs) travelling along the the Earth-Sun
interplanetary space would allow early warning of geo-effective solar
storms. This presentation will illustrate the mission profile and
the solar-sail orbit at the L-points, and will describe the expected
performances of the miniature WACor in detecting fast (>1000 km/s),
Earth-directed CMEs.
Title: Plasma Heating in a Post Eruption Current Sheet: A Case Study
Based on Ultraviolet, Soft, and Hard X-Ray Data
Authors: Susino, R.; Bemporad, A.; Krucker, Säm
Bibcode: 2013ApJ...777...93S
Altcode: 2013arXiv1310.2853S
Off-limb observations of the solar corona after coronal mass ejections
(CMEs) often show strong, compact, and persistent UV sources behind the
eruption. They are primarily observed by the SOHO/UVCS instrument in the
"hot" [Fe XVIII] λ974 line and are usually interpreted as a signature
of plasma heating due to magnetic reconnection in the post-CME current
sheet (CS). Nevertheless, the physical process itself and the altitude
of the main energy release are currently not fully understood. In
this work, we study the evolution of plasma heating after the CME of
2004 July 28 by comparing UV spectra acquired by UVCS with soft and
hard X-ray (SXR, HXR) images of the post-flare loops taken by GOES/SXI
and RHESSI. The X-ray data show a long-lasting extended source that is
rising upward, toward the high-temperature source detected by UVCS. UVCS
data show the presence of significant non-thermal broadening in the
CS (a signature of turbulent motions) and a strong density gradient
across the CS region. The thermal energy released in the HXR source
is on the order of ~1032 erg, a factor ~2-5 larger than
the energy required to explain the high-temperature plasma sampled
by UVCS. Nevertheless, the very different time evolutions of SXR and
HXR sources compared with the UV emission suggest that reconnection
occurring above the post-eruption arcades is not directly responsible
for the high-temperature plasma sampled higher up by UVCS. We conclude
that an additional plasma heating mechanism (such as turbulent
reconnection) in the CS is likely required.
Title: Study of a Coronal Mass Ejection with SOHO/UVCS and STEREO data
Authors: Susino, Roberto; Bemporad, Alessandro; Dolei, Sergio;
Vourlidas, Angelos
Bibcode: 2013AdSpR..52..957S
Altcode:
We study the 3-D kinematics of a Coronal Mass Ejection (CME) using
data acquired by the LASCO C2 and UVCS instruments on board SOHO, and
the COR1 coronagraphs and EUVI telescopes on board STEREO. The event,
which occurred on May 20, 2007, was a partial-halo CME associated
with a prominence eruption. This is the first CME studied with UVCS
data that occurred in the STEREO era. The longitudinal angle between
the STEREO spacecrafts was ∼7.7° at that time, and this allowed us
to reconstruct via triangulation technique the 3-D trajectory of the
erupting prominence observed by STEREO/EUVI. Information on the 3-D
expansion of the CME provided by STEREO/COR1 data have been combined
with spectroscopic observations by SOHO/UVCS. First results presented
here show that line-of-sight velocities derived from spectroscopic
data are not fully in agreement with those previously derived via
triangulation technique, thus pointing out possible limitations of
this technique.
Title: Super- and sub-critical regions in shocks driven by radio-loud
and radio-quiet CMEs
Authors: Bemporad, Alessandro; Mancuso, Salvatore
Bibcode: 2013JAdR....4..287B
Altcode: 2012arXiv1211.2567B
White-light coronagraphic images of Coronal Mass Ejections (CMEs)
observed by SOHO/LASCO C2 have been used to estimate the density jump
along the whole front of two CME-driven shocks. The two events are
different in that the first one was a "radio-loud" fast CME, while
the second one was a "radio quiet" slow CME. From the compression
ratios inferred along the shock fronts, we estimated the Alfvén Mach
numbers for the general case of an oblique shock. It turns out that
the "radio-loud" CME shock is initially super-critical around the
shock center, while later on the whole shock becomes sub-critical. On
the contrary, the shock associated with the "radio-quiet" CME is
sub-critical at all times. This suggests that CME-driven shocks could be
efficient particle accelerators at the shock nose only at the initiation
phases of the event, if and when the shock is super-critical, while
at later times they lose their energy and the capability to accelerate
high energetic particles.
Title: SWIFF: Space weather integrated forecasting framework
Authors: Lapenta, Giovanni; Pierrard, Viviane; Keppens, Rony; Markidis,
Stefano; Poedts, Stefaan; Šebek, Ondřej; Trávníček, Pavel M.;
Henri, Pierre; Califano, Francesco; Pegoraro, Francesco; Faganello,
Matteo; Olshevsky, Vyacheslav; Restante, Anna Lisa; Nordlund, Åke;
Trier Frederiksen, Jacob; Mackay, Duncan H.; Parnell, Clare E.;
Bemporad, Alessandro; Susino, Roberto; Borremans, Kris
Bibcode: 2013JSWSC...3A..05L
Altcode:
SWIFF is a project funded by the Seventh Framework Programme of the
European Commission to study the mathematical-physics models that
form the basis for space weather forecasting. The phenomena of space
weather span a tremendous scale of densities and temperature with
scales ranging 10 orders of magnitude in space and time. Additionally
even in local regions there are concurrent processes developing at
the electron, ion and global scales strongly interacting with each
other. The fundamental challenge in modelling space weather is the
need to address multiple physics and multiple scales. Here we present
our approach to take existing expertise in fluid and kinetic models to
produce an integrated mathematical approach and software infrastructure
that allows fluid and kinetic processes to be modelled together. SWIFF
aims also at using this new infrastructure to model specific coupled
processes at the Solar Corona, in the interplanetary space and in the
interaction at the Earth magnetosphere.
Title: The role of streamers in the deflection of coronal mass
ejections: comparison between STEREO 3D reconstructions and numerical
simulations
Authors: Zuccarello, F. P.; Bemporad, A.; Jacobs, C.; Mierla, M.;
Poedts, S.; Zuccarello, F.
Bibcode: 2012AGUFMSH31A2200Z
Altcode:
On 2009 September 21, a filament eruption and the associated Coronal
Mass Ejection (CME) was observed by the %coronographs on board of the
STEREO spacecraft. The CME originated from the southern hemisphere and
showed a deflection of about 15o towards the heliospheric
current sheet (HCS) during the propagation in the COR1 field-of-view
(FOV). The CME source region was near the central meridian, but no
on-disk CME signatures could be seen from the Earth. The aim of this
paper is to provide a physical explanation for the strong deflection
of the CME observed on 2009 September 21. The two-sided view of the
STEREO spacecraft allows us to reconstruct the three dimensional (3D)
travel path of the CME and the evolution of the CME source region. The
observations are combined with a magnetohydrodynamic (MHD) simulation,
starting from a magnetic field configuration closely resembling the
extrapolated potential field for that date. %The amount of helicity
injected in the coronal volume is similar in both the observation
and the simulation. By applying localized shearing motions, a CME is
initiated in the simulation, showing a similar non-radial evolution,
structure, and velocity as the observed event. The CME gets deflected
towards the current sheet of the larger northern helmet streamer, due
to an imbalance in the magnetic pressure and tension forces and finally
it gets into the streamer. This study shows that during solar minima,
even CMEs originating from high latitude can be easily deflected towards
the heliospheric current sheet, eventually resulting in geoeffective
events. How rapidly they undergo this latitudinal migration depends
on the strength of both the large scale coronal magnetic field and
the magnetic flux of the erupting filament.
Title: Study of Multiple Coronal Mass Ejections at Solar Minimum
Conditions
Authors: Bemporad, A.; Zuccarello, F. P.; Jacobs, C.; Mierla, M.;
Poedts, S.
Bibcode: 2012SoPh..281..223B
Altcode: 2012SoPh..tmp..153B
The aim of this work is to provide a physical explanation for the
genesis of multiple coronal mass ejections (CMEs) in an asymmetric
coronal field configuration. We analyze STEREO observations of a
multiple eruption and compare the results from the data analysis with
predictions provided by magnetohydrodynamic (MHD) simulations. To this
end, the multiple CMEs (MCMEs) observed on 21 - 22 September 2009 were
selected. Both eruptions originated from the same source region and
showed approximately the same latitudinal deflection, by more than
15 degrees, toward the heliospheric current sheet (HCS) during their
propagation in the COR1 field of view. Numerical MHD simulations of
the MCMEs have been performed, starting from an asymmetric coronal
field configuration that mimics the potential field source surface
extrapolation for 21 September 2009. The results demonstrate that,
by shearing the footpoints at the base of the southern arcade,
we were able to reproduce the observed dynamics of the MCMEs. Both
CMEs are deflected toward the HCS due to an imbalance in the magnetic
pressure and tension forces; the global field strength turns out to
be a crucial parameter in order to release two subsequent eruptions,
and hence to reproduce the observed evolution.
Title: Multi Element Telescope for Imaging and Spectroscopy (METIS)
coronagraph for the Solar Orbiter mission
Authors: Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero;
Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Nicolosi,
Piergiorgio; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro;
Auchère, Frédéric; Berlicki, Arkadiusz; Bruno, Roberto; Capobianco,
Gerardo; Ciaravella, Angela; Crescenzio, Giuseppe; Da Deppo, Vania;
D'Amicis, Raffaella; Focardi, Mauro; Frassetto, Fabio; Heinzel,
Peter; Lamy, Philippe L.; Landini, Federico; Massone, Giuseppe;
Malvezzi, Marco A.; Moses, J. Dan; Pancrazzi, Maurizio; Pelizzo,
Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
Bibcode: 2012SPIE.8443E..09A
Altcode:
METIS, the “Multi Element Telescope for Imaging and Spectroscopy”,
is a coronagraph selected by the European Space Agency to be part of
the payload of the Solar Orbiter mission to be launched in 2017. The
unique profile of this mission will allow 1) a close approach to the
Sun (up to 0.28 A.U.) thus leading to a significant improvement in
spatial resolution; 2) quasi co-rotation with the Sun, resulting in
observations that nearly freeze for several days the large-scale outer
corona in the plane of the sky and 3) unprecedented out-of-ecliptic
view of the solar corona. This paper describes the experiment concept
and the observational tools required to achieve the science drivers
of METIS. METIS will be capable of obtaining for the first time: •
simultaneous imaging of the full corona in polarized visible-light
(590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); •
monochromatic imaging of the full corona in the extreme ultraviolet
He II Lyman α (30.4 nm); • spectrographic observations of the HI
and He II Ly α in corona. These measurements will allow a complete
characterization of the three most important plasma components of
the corona and the solar wind, that is, electrons, hydrogen, and
helium. This presentation gives an overview of the METIS imaging and
spectroscopic observational capabilities to carry out such measurements.
Title: MESSI: the METIS instrument software simulator
Authors: Nicolini, G.; Andretta, V.; Abbo, L.; Antonucci, E.; Bemporad,
A.; Capobianco, G.; Crescenzio, G.; Fineschi, S.; Focardi, M.; Magli,
E.; Naletto, G.; Nicolosi, G.; Pancrazzi, M.; Ricci, M.; Romoli, M.;
Uslenghi, M.; Volpicelli, A.
Bibcode: 2012SPIE.8449E..1LN
Altcode:
Instrument software simulators are becoming essential both for
supporting the instrument design and for planning the future
operations. In this paper we present the Software Simulator developed
for the METIS coronagraph, an instrument of the Solar Orbiter ESA
mission. We describe its architecture and the modules it is composed
of, and how they interchange data to simulate the whole acquisition
chain from the photons entering the front window to the stream
of telemetry? data received and analysed on ground. Each software
module simulates an instrument subsystem by combining theoretical
models and measured subsystem properties. A web-based application
handles the remote user interfaces of the Institutions of the METIS
Consortium, allowing users from various sites to overview and interact
with the data flow, making possible for instance input and output at
intermediate nodes. Description of the modes of use of the simulator,
both present and future, are given with examples of results. These
include not only design-aid tasks, as the evaluation and the tuning
of the image compression algorithms, but also those tasks aimed to
plan the in-flight observing sequences, based on the capability of
the simulator of performing end to end simulations of science cases.
Title: METIS: a novel coronagraph design for the Solar Orbiter mission
Authors: Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero;
Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Abbo, Lucia;
Andretta, Vincenzo; Bemporad, Alessandro; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.;
Moses, J. Dan; Nicolosi, Piergiorgio; Pancrazzi, Maurizio; Pelizzo,
Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
Bibcode: 2012SPIE.8443E..3HF
Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy) METIS,
the “Multi Element Telescope for Imaging and Spectroscopy”,
is a coronagraph selected by the European Space Agency to be part
of the payload of the Solar Orbiter mission to be launched in
2017. The mission profile will bring the Solar Orbiter spacecraft
as close to the Sun as 0.3 A.U., and up to 35° out-of-ecliptic
providing a unique platform for helio-synchronous observations of
the Sun and its polar regions. METIS coronagraph is designed for
multi-wavelength imaging and spectroscopy of the solar corona. This
presentation gives an overview of the innovative design elements of
the METIS coronagraph. These elements include: i) multi-wavelength,
reflecting Gregorian-telescope; ii) multilayer coating optimized for
the extreme UV (30.4 nm, HeII Lyman-α) with a reflecting cap-layer
for the UV (121.6 nm, HI Lyman-α) and visible-light (590-650); iii)
inverse external-occulter scheme for reduced thermal load at spacecraft
peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror
to feed a 1st and 4th-order spherical varied
line-spaced (SVLS) grating placed on a section of the secondary mirror;
v) liquid crystals electro-optic polarimeter for observations of the
visible-light K-corona. The expected performances are also presented.
Title: The role of streamers in the deflection of coronal mass
ejections
Authors: Zuccarello, F. P.; Bemporad, A.; Jacobs, C.; Mierla, M.;
Poedts, S.; Zuccarello, F.
Bibcode: 2012IAUS..286..134Z
Altcode:
On 2009 September 21, a filament eruption and the associated Coronal
Mass Ejection (CME) was observed by the STEREO spacecraft. The CME
originated from the southern hemisphere and showed a deflection of about
15° towards the heliospheric current sheet (HCS) during its propagation
in the COR1 field-of-view (FOV). The aim of this paper is to provide a
physical explanation for the strong deflection of the CME. We first use
the STEREO observations in order to reconstruct the three dimensional
(3D) trajectory of the CME. Starting from a magnetic configuration that
closely resembles the potential field extrapolation for that date, we
performed numerical magneto-hydrodynamics (MHD) simulations. By applying
localized shearing motions, a CME is initiated in the simulation,
showing a similar non-radial evolution, structure, and velocity as the
observed event. The CME gets deflected towards the current sheet of the
larger northern helmet streamer, due to an imbalance in the magnetic
pressure and tension forces and finally it gets into the streamer and
propagates along the heliospheric current sheet.
Title: Deflection of Multiple Coronal Mass Ejections: STEREO
observations and MHD simulations
Authors: Bemporad, Alessandro; Jacobs, Carla; Zuccarello, Francesco;
Mierla, Marilena
Bibcode: 2012cosp...39..138B
Altcode: 2012cosp.meet..138B
In this work we focus on the physical explanation for the deflection
of a couple of Multiple Coronal Mass Ejections (MCMEs) observed between
September 21-22, 2009. For the first event, STEREO/EUVI and /COR1 data
allowed us to reconstruct the 3-D trajectory of the prominence eruption
via triangulation technique and of the resulting CME via polarization
ratio method. Results show that the first MCME originated from the
southern hemisphere and showed a deflection of about 15 degrees
toward the heliospheric current sheet during the propagation in the
COR1 field of view. This trajectory is similar to the one followed
by the second MCME, occurring 8 hours later, originating from the
same source region (as also shown by Forward Modelling technique),
not associated with a prominence eruption. Magneto-hydrodynamic (MHD)
simulations, starting from an asymmetric coronal field configuration
that mimics the potential field source surface extrapolation, were
performed. By applying localized shearing motions, a first MCME is
initiated in the simulation, with similar structure and kinematic
as the observed event. The CME gets deflected toward the current
sheet of the larger northern helmet streamer due to an imbalance in
the magnetic pressure and tension forces and finally gets into the
streamer. In a second simulation, the second MCME is also reproduced
simply by changing the strength of the global dipole, demonstrating
that the overlying field strenght is a crucial parameter in order to
reproduce the observed evolution.
Title: Spectroscopic Signature of Alfvén Waves Damping in a Polar
Coronal Hole up to 0.4 Solar Radii
Authors: Bemporad, A.; Abbo, L.
Bibcode: 2012ApJ...751..110B
Altcode: 2012arXiv1204.2544A
Between 2009 February 24 and 25, the EUV Imaging Spectrometer (EIS)
spectrometer on board the Hinode spacecraft performed special "sit and
stare" observations above the south polar coronal hole continuously over
more than 22 hr. Spectra were acquired with the 1'' slit placed off-limb
covering altitudes up to 0.48 R ⊙ (3.34 × 102
Mm) above the Sun surface, in order to study with EIS the non-thermal
spectral line broadenings. Spectral lines such as Fe XII λ186.88,
Fe XII λ193.51, Fe XII λ195.12, and Fe XIII λ202.04 are observed
with good statistics up to high altitudes and they have been analyzed
in this study. Results show that the FWHM of the Fe XII λ195.12 line
increases up to ~= 0.14 R ⊙, then decreases higher up. EIS
stray light has been estimated and removed. Derived electron density
and non-thermal velocity profiles have been used to estimate the
total energy flux transported by Alfvén waves off-limb in the polar
coronal hole up to ~= 0.4 R ⊙. The computed Alfvén wave
energy flux density fw progressively decays with altitude
from fw ~= 1.2 × 106 erg cm-2
s-1 at 0.03 R ⊙ down to fw ~=
8.5 × 103 erg cm-2 s-1 at 0.4 R
⊙, with an average energy decay rate of Δfw
/Δh ~= -4.5 × 10-5 erg cm-1. Hence, this result
suggests energy deposition by Alfvén waves in a polar coronal hole,
thus providing a significant source for coronal heating.
Title: A decade of coronagraphic and spectroscopic studies of
CME-driven shocks
Authors: Vourlidas, Angelos; Bemporad, Alessandro
Bibcode: 2012AIPC.1436..279V
Altcode: 2012arXiv1207.1603V
Shocks driven by Coronal Mass Ejections (CMEs) are primary agents of
space weather. They can accelerate particles to high energies and
can compress the magnetosphere thus setting in motion geomagnetic
storms. For many years, these shocks were studied only in-situ when
they crossed over spacecraft or remotely through their radio emission
spectra. Neither of these two methods provides information on the
spatial structure of the shock nor on its relationship to its driver,
the CME. In the last decade, we have been able to not only image
shocks with coronagraphs but also measure their properties remotely
through the use of spectroscopic and image analysis methods. Thanks to
instrumentation on STEREO and SOHO we can now image shocks (and waves)
from the low corona, through the inner heliosphere, to Earth. Here,
we review the progress made in imaging and analyzing CME-driven shocks
and show that joint coronagraphic and spectrscopic observations are
our best means to understand shock physics close to the Sun.
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: The Role of Streamers in the Deflection of Coronal Mass
Ejections: Comparison between STEREO Three-dimensional Reconstructions
and Numerical Simulations
Authors: Zuccarello, F. P.; Bemporad, A.; Jacobs, C.; Mierla, M.;
Poedts, S.; Zuccarello, F.
Bibcode: 2012ApJ...744...66Z
Altcode:
On 2009 September 21, a filament eruption and the associated
coronal mass ejection (CME) were observed by the Solar Terrestrial
Relations Observatory (STEREO) spacecraft. The CME originated from the
southern hemisphere and showed a deflection of about 15° toward the
heliospheric current sheet (HCS) during the propagation in the COR1
field of view. The CME source region was near the central meridian,
but no on-disk CME signatures could be seen from the Earth. The aim
of this paper is to provide a physical explanation for the strong
deflection of the CME observed on 2009 September 21. The two-sided view
of the STEREO spacecraft allows us to reconstruct the three-dimensional
travel path of the CME and the evolution of the CME source region. The
observations are combined with a magnetohydrodynamic simulation,
starting from a magnetic field configuration closely resembling the
extrapolated potential field for that date. By applying localized
shearing motions, a CME is initiated in the simulation, showing a
similar non-radial evolution, structure, and velocity as the observed
event. The CME gets deflected toward the current sheet of the larger
northern helmet streamer due to an imbalance in the magnetic pressure
and tension forces and finally gets into the streamer. This study shows
that during solar minima, even CMEs originating from high latitude can
be easily deflected toward the HCS, eventually resulting in geoeffective
events. How rapidly they undergo this latitudinal migration depends
on the strength of both the large-scale coronal magnetic field and
the magnetic flux of the erupting filament.
Title: Rotation of an erupting filament observed by STEREO EUVI and
COR1 instruments (Corrigendum)
Authors: Bemporad, A.; Mierla, M.; Tripathi, D.
Bibcode: 2012A&A...537C...1B
Altcode:
Present Address: inter-University Centre for Astronomy and Astrophysics,
Post Bag 4, Ganeshkhind, 411007 Pune, India.
Title: Identification of Super- and Subcritical Regions in Shocks
Driven by Coronal Mass Ejections
Authors: Bemporad, A.; Mancuso, S.
Bibcode: 2011ApJ...739L..64B
Altcode: 2011arXiv1108.3783B
In this work, we focus on the analysis of a coronal mass ejection (CME)
driven shock observed by the Solar and Heliospheric Observatory/Large
Angle and Spectrometric Coronagraph Experiment. We show that white-light
coronagraphic images can be employed to estimate the compression ratio X
= ρ d /ρ u all along the front of CME-driven
shocks. X increases from the shock flanks (where X ~= 1.2) to the
shock center (where X ~= 3.0 is maximum). From the estimated X values,
we infer the Alfvén Mach number for the general case of an oblique
shock. It turns out that only a small region around the shock center
is supercritical at earlier times, while higher up in the corona the
whole shock becomes subcritical. This suggests that CME-driven shocks
could be efficient particle accelerators at the initiation phases of
the event, while at later times they progressively loose energy, also
losing their capability to accelerate high-energy particles. This result
has important implications on the localization of particle acceleration
sites and in the context of predictive space weather studies.
Title: The solar orbiter METIS coronagraph data signal processing
chain
Authors: Pancrazzi, M.; Focardi, M.; Uslenghi, M.; Nicolini, G.;
Magli, E.; Landini, F.; Romoli, M.; Bemporad, A.; Antonucci, E.;
Fineschi, S.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.
Bibcode: 2011SPIE.8167E..2CP
Altcode: 2011SPIE.8167E..66P
METIS, the Multi Element Telescope for Imaging and Spectroscopy,
is one of the instruments selected in 2009 by ESA to be part of the
payload of the Solar Orbiter mission. The instrument design has been
conceived to perform both multiband imaging and UV spectroscopy of
the solar corona. The two sensors of the detecting system will produce
images in visible light and in two narrow UV bands, at 121.6 and 30.4
nm. The instrument is constituted by several subunits that have to be
properly controlled and synchronized in order to provide the expected
performances. Moreover, the large amount of data collected by METIS has
to be processed by the on board electronics to reduce the data volume
to be delivered to ground by telemetry. These functionalities will be
realized by a dedicated electronics, the Main Power and Processing Unit
(MPPU). This paper will provide an overview of the METIS data handling
system and the expected on board data processing.
Title: Liquid crystals Lyot filter for solar coronagraphy
Authors: Fineschi, S.; Capobianco, G.; Massone, G.; Baur, T.; Bemporad,
A.; Abbo, L.; Zangrilli, L.; Dadeppo, V.
Bibcode: 2011SPIE.8148E..08F
Altcode: 2011SPIE.8148E...7F
The "Association de Satellites Pour l'Imagerie et l'Interférométrie
de la Couronne Solaire", ASPIICS, is a solar coronagraph to be flown on
the PROBA 3 Technology mission of the European Space Agency. ASPIICS
heralds the next generation of coronagraphs for solar research,
exploiting formation flying to gain access to the inner corona under
eclipse-like conditions in space. The science goal is high spatial
resolution imaging and two-dimensional spectrophotometry of the Fe
XIV, 530.3 nm, emission line. This work describes a liquid crystal
Lyot tunable-filter and polarimeter (LCTP) that can implement this
goal. The LCTP is a bandpass filter with a full width at half maximum
of 0.15 nm at a wavelength of 530.3 nm. The center wavelength of the
bandpass is tunable in 0.01 nm steps from 528.64 nm to 533.38 nm. It
is a four stage Lyot filter with all four stages wide-fielded. The
free spectral range between neighboring transmission bands of the
filter is 2.7 nm. The wavelength tuning is non-mechanical using
nematic liquid crystal variable retarders (LCVR's). A separate LCVR
of the Senarmont design, in tandem with the filter, is used for the
polarimetric measurements. A prototype of the LCTP has been built and
its measured performances are presented here.
Title: Rotation of an erupting filament observed by the STEREO EUVI
and COR1 instruments
Authors: Bemporad, A.; Mierla, M.; Tripathi, D.
Bibcode: 2011A&A...531A.147B
Altcode:
On August 31, 2007, a prominence eruption was observed by the Solar
TErrestrial RElations Observatory (STEREO) in the Extreme-UltraViolet
Imager (EUVI) 304 images and later on, as the core of a three-part
coronal mass ejection (CME) in images acquired by the inner STEREO
coronagraph (COR1). Because they were covered by both STEREO
spacecraft from right vantage points, these observations provide an
excellent opportunity to perform a three-dimensional (3D) prominence
reconstruction and study its evolution. We employed the tie-pointing
technique to reconstruct the 3D shape and trajectory of the prominence,
which has been followed from an heliocentric distance of ~1.3 up to ~2.4
R⊙ during the first 1.3 h of eruption. Data show evidence
for a progressive clockwise prominence rotation by ~90° occurring
not only in the early phase of the eruption sampled by EUVI, but also
at larger heliocentric distances as seen by COR1. Interestingly,
a counter-clockwise rotation of the filament was observed in Hα
images in the week before the eruption; the filament does not show a
twisted shape. In the same period, the potential field extrapolated at
different times shows a clockwise rotation of closed lines overlying the
filament. This suggests that a magnetic helicity storage occurred not in
the filament itself, but in the global magnetic field configuration
of the surrounding corona. Moreover, close inspection to the
high-resolution EUVI images revealed a small scale helical feature along
the erupting prominence. The sense of rotation of this helix agrees with
the observed prominence rotation, providing evidence for the conversion
of twist into writhe. The observed rotation of an erupting prominence,
if representative of the flux rope rotation, may have a strong impact
on the definition of geo-effectiveness of CMEs for space weather
forecasting purposes. Two movies are available in electronic form
at http://www.aanda.org
Title: Prominence 3D reconstruction in the STEREO era: A review
Authors: Bemporad, A.
Bibcode: 2011JASTP..73.1117B
Altcode:
Since the launch of the STEREO mission (October 2006) the determination
of the real prominence shapes and trajectories during eruptions in
three dimensions (3D) became easily viable, thanks to the stereoscopic
observations, available for the first time, acquired by the twin STEREO
spacecraft. These data give us now a unique capability to identify
twisted or ribbon-like structures, helical or planar motions, and to
investigate the existence of a real critical height for prominence
eruptions without projection effects. All these parameters are of
fundamental importance for understanding the physical phenomena
triggering the eruption and affecting their early evolution. Many
different techniques have been developed and employed after the
beginning of the "STEREO era", but important information on the 3D
structure of prominences was also derived before STEREO. Hence,
the present paper is aimed at reviewing different reconstruction
techniques developed both before and after the availability of
stereoscopic observations and discusses the advancement made so far
on these issues thanks to the pre- and post-STEREO data.
Title: First Complete Determination of Plasma Physical Parameters
Across a Coronal Mass Ejection-driven Shock
Authors: Bemporad, A.; Mancuso, S.
Bibcode: 2010ApJ...720..130B
Altcode:
We report on the study of a fast coronal mass ejection (CME)-driven
shock associated with the solar eruption of 2002 March 22. This
event was observed in the intermediate corona both in white light and
the extreme ultraviolet (EUV) by the LASCO and UVCS instruments on
board the Solar and Heliospheric Observatory, as well as in metric
and decametric wavelengths through space- and ground-based radio
observatories. Clear signatures of shock transit are (1) strong type
II emission lanes observed after the CME initiation, (2) strong O VI
λλ1032, 1037 line profile broadenings (up to ~2 × 107 K)
associated with the shock transit across the UVCS slit field of view,
and (3) a density enhancement located in LASCO images above the CME
front. Since the UVCS slit was centered at 4.1 R sun, in
correspondence with the flank of the expanding CME, this observation
represents the highest UV detection of a shock obtained so far with
the UVCS instrument. White-light and EUV data have been combined in
order to estimate not only the shock compression ratio and the plasma
temperature, but also the strength of the involved coronal magnetic
fields, by applying the Rankine-Hugoniot equations for the general
case of oblique shocks. Results show that, for a compression ratio
X = 2.06 as derived from LASCO data, the coronal plasma is heated
across the shock from an initial temperature of 2.3 × 105
K up to 1.9 × 106 K, while at the same time the magnetic
field undergoes a compression from a pre-shock value of ~0.02 G up to
a post-shock field of ~0.04 G. Magnetic and kinetic energy density
increases at the shock are comparable (in agreement with the idea
of equipartition of energy), and both are more than two times larger
than the thermal energy density increase. This is the first time that
a complete characterization of pre- and post-shock plasma physical
parameters has been derived in the solar corona.
Title: Side Magnetic Reconnections Induced by Coronal Mass Ejections:
Observations and Simulations
Authors: Bemporad, A.; Soenen, A.; Jacobs, C.; Landini, F.; Poedts, S.
Bibcode: 2010ApJ...718..251B
Altcode:
Over the last few years coronagraphic and spectroscopic observations
have demonstrated that small-scale eruptions, such as "jets," "narrow
coronal mass ejections (CMEs)," "mini CMEs," "streamer puffs," "streamer
detachments," and others, occur ubiquitously on the Sun. Nevertheless,
the origin of small-scale eruptive events and how these are interrelated
with larger scale CMEs have been poorly investigated so far. In this
work, we study a series of small-scale side eruptions that occurred
during and after a large-scale CME. Observations show that a CME can
be associated not only with a single reconnection process, leading to
the large-scale phenomenon, but also with many other side reconnections
occurring at different locations and times around the main flux rope,
possibly induced by the CME expansion in the surrounding corona. White
light and EUV observations of a slow CME acquired by the SOHO/LASCO and
SOHO/UVCS instruments are analyzed here to characterize the locations
of side reconnections induced by the CME. The magnetic reconnection
rate M has been estimated from the UVCS data from the ratio between
the inflows and outflows observed around the reconnection region, and
from the LASCO data from the observed aperture angles between the slow
mode shocks (SMSs) associated with the reconnection. It turns out that
M ~= 0.05 at the heliocentric distance of 1.8 R sun, while
between ~2.5 and 5.5 R sun, M values progressively decrease
with time/altitude from M ~ 1 down to M ~ 0.3. Such large values of
M are theoretically acceptable only if flux pile-up reconnection is
envisaged. The observed occurrence of multiple reconnections associated
with a CME is verified by numerical simulations of an eruption occurring
within multiple helmet streamers. The simulations confirm that small
side reconnections are a consequence of CME expansion against the
surrounding coronal streamers. The simulated and observed evolution of
aperture angles between the SMSs are in good agreement as well. These
results demonstrate the effect of the global coronal magnetic field
in the occurrence of small-scale eruptions due to lateral reconnection
in a preceding CME event.
Title: Alfven waves in a polar coronal hole from HINODE/EIS off
limb observations
Authors: Bemporad, Alessandro; Abbo, Lucia
Bibcode: 2010cosp...38.2941B
Altcode: 2010cosp.meet.2941B
Between February 24-25, 2009, the EIS spectrometer onboard HINODE
performed for the first time more than 22h of continuous "sit &
stare" observations over the South polar coronal hole, with an exposure
time of 500s. Spectra were acquired with the 1" slit placed off-limb
in order to cover altitudes up to 0.48 solar radii (3.3 × 105 km)
above the limb. Spectral lines such as FeXII λ186.88, FeXII λ193.51,
FeXII λ195.12, FeXIII λ202.04, HeII λ256.32, and CaXVII λ192.81
have been observed with good statistics up to different altitude
ranges. From the observed Fe line intensities and line profile widths
we estimate the electron density and ion kinetic temperatures up to
∼ 0.4 solar radii above the limb. FeXII 195 line profiles show an
increase of non-thermal velocities up to ∼ 0.2 solar radii, followed
by a decrease above this altitude. In the hypothesis that the observed
non-thermal broadening is a spectroscopic signature of Alfv`n waves,
results show a good agreement with the theoretical curve for the
propagation of undamped waves up to ∼ 0.2 solar radii, while above
this altitude waves energy deposition occurs.
Title: Multi-wavelength study of a CME-driven shock at 4.1 solar radii
Authors: Bemporad, Alessandro; Mancuso, Salvatore
Bibcode: 2010cosp...38.3021B
Altcode: 2010cosp.meet.3021B
We report on the analysis of a peculiar fast CME-driven shock associated
to the eruption of March 22, 2002. The event was observed by the
SOHO/UVCS instrument at 4.1 solar radii, with the spectrometer slit
placed in correspondence of the flank of the expanding CME. Signatures
of a strong MHD shock are observed in radio data (where a type-II radio
burst was observed), white light SOHO/LASCO images (where a spherical
density gradient located above the expanding CME front was observed) and
in SOHO/UVCS spectra (where strong line broadenings are observed). UVCS,
LASCO and radio data have been coupled to estimate not only the shock
compression ratio and the pre-and post-shock plasma temperatures, but
also, by applying the Rankine-Hugoniot equations for the general case of
an oblique shock, the strength of the involved coronal magnetic fields.
Title: An Erupting Filament and Associated CME Observed by Hinode,
STEREO and SOHO
Authors: Bemporad, A.; Del Zanna, G.; Andretta, V.; Magrí, M.;
Poletto, G.; Ko, Y. -K.
Bibcode: 2009ASPC..415..385B
Altcode:
A multi-spacecraft campaign was set up in May 2007 to observe the
off-limb corona with Hinode, STEREO and SOHO instruments (Hinode
HOP 7). During this campaign, a filament eruption and a coronal
mass ejection (CME) occurred on May 9 from NOAA 10953 at the West
limb. The filament eruption starts around 13:40 UT and results in a
CME at 4°SW latitude. Remarkably, the event was observed by STEREO
(EUVI and COR1) and by the Hinode/EIS and SOHO/UVCS spectrometers. We
present results from all these instruments. High-cadence data from
Stereo/EUVI A and B in the He II λ304 line were used to study the
3-D expansion of the filament. A slow rising phase, during which the
filament moved southward, was followed by an impulsive phase during
which the filament appeared to change direction and then contribute
to the westward-expanding CME as seen in STEREO/COR 1. Hinode/EIS was
scanning with the 2'' slit the region where the filament erupted. The
EIS spectra show remarkable non-thermal broadening in lines emitted at
different temperatures at the location of the filament eruption. The
CME was also observed by the SOHO/UVCS instrument: the spectrograph
slit was centered at 1.7 solar radii, at a latitude of 5°SW and
recorded a sudden increase in the O VI λλ 1032-1037 and Si XI λ520
spectral line intensities. We discuss the overall morphology of this
interesting eruptive event, and provide a preliminary assessment of
its temperature and density structure.
Title: Multi-Instrument Campaigns to Observe the Off-Limb Corona
Authors: Del Zanna, G.; Andretta, V.; Poletto, G.; Teriaca, L.; Ko,
Y. -K.; Mason, H. E.; Vourdilas, A.; Bemporad, A.; Magri, M.
Bibcode: 2009ASPC..415..315D
Altcode:
We briefly describe two multi-instrument campaigns we coordinated to
observe the off-limb corona in 2007, with some preliminary results. The
first one (Hinode HOP 7) was a SOHO/Hinode/TRACE/STEREO/Ulysses
week-long campaign during the SOHO-Ulysses quadrature in 2007 May. We
could not achieve all of our goals, however we were very fortunate in
that the ``Del Zanna'' active region appeared on the Sun at the right
longitude, and that a filament eruption and a CME were observed. Of
particular significance is the finding of large (100 km s-1)
non-thermal broadenings in all coronal lines observed by Hinode/EIS
in the region where the filament was erupting. The second campaign
(Hinode HOP 44) involved SOHO (CDS, SUMER, UVCS), Hinode, and TRACE to
measure the physical parameters of plume/interplume regions in the polar
coronal holes from the low corona to 1.7 solar radii, on 30/10-4/11. We
obtained a good set of observations, however various instrumental
constraints and the lack of fully developed plumes limited our goals.
Title: The role of lateral magnetic reconnection in solar eruptive
events
Authors: Soenen, A.; Bemporad, A.; Jacobs, C.; Poedts, S.
Bibcode: 2009AnGeo..27.3941S
Altcode:
On 10-11 December 2005 a slow CME occurred in between two coronal
streamers in the Western Hemisphere. SOHO/MDI magnetograms show a
multipolar magnetic configuration at the photosphere consisting of a
complex of active regions located at the CME source and two bipoles
at the base of the lateral coronal streamers. White light observations
reveal that the expanding CME affects both of the lateral streamers and
induces the release of plasma within or close to them. These transient
phenomena are possibly due to magnetic reconnections induced by the
CME expansion that occurs either inside the streamer current sheet or
between the CME flanks and the streamer. Our observations show that
CMEs can be associated to not only a single reconnection process
at a single location in the corona, but also to many reconnection
processes occurring at different times and locations around the flux
rope. Numerical simulations are used to demonstrate that the observed
lateral reconnections can be reproduced. The observed secondary
reconnections associated to CMEs may facilitate the CME release by
globally decreasing the magnetic tension of the corona. Future CME
models should therefore take into account the lateral reconnection
effect.
Title: Multispacecraft observations of a prominence eruption
Authors: Bemporad, A.; Del Zanna, G.; Andretta, V.; Poletto, G.;
Magrí, M.
Bibcode: 2009AnGeo..27.3841B
Altcode:
On 9 May 2007 a prominence eruption occurred at the West
limb. Remarkably, the event was observed by the STEREO/EUVI telescopes
and by the HINODE/EIS and SOHO/UVCS spectrometers. We present results
from all these instruments. High-cadence (~37 s) data from STEREO/EUVI
A and B in the He II λ304 line were used to study the 3-D shape and
expansion of the prominence. The high spatial resolution EUVI images
(~1.5"/pixel) have been used to infer via triangulation the 3-D shape
and orientation of the prominence 12 min after the eruption onset. At
this time the prominence has mainly the shape of a "hook" highly
inclined southward, has an average thickness of 0.068 R⊙,
a length of 0.43 R⊙ and lies, in first approximation,
on a plane. Hence, the prominence is mainly a 2-D structure and there
is no evidence for a twisted flux rope configuration. HINODE/EIS was
scanning with the 2" slit the region where the filament erupted. The
EIS spectra show during the eruption remarkable non-thermal broadening
(up to ~100 km s-1) in the region crossed by the filament
in spectral lines emitted at different temperatures, possibly with
differences among lines from higher Fe ionization stages. The CME was
also observed by the SOHO/UVCS instrument: the spectrograph slit was
centered at 1.7 R⊙, at a latitude of 5° SW and recorded
a sudden increase in the O VI λλ1032-1037 and Si XII λ520 spectral
line intensities, representative of the CME front transit.
Title: Stereoscopic Reconstruction from STEREO/EUV Imagers Data of
the Three-dimensional Shape and Expansion of an Erupting Prominence
Authors: Bemporad, A.
Bibcode: 2009ApJ...701..298B
Altcode:
On 2007 May 9, a prominence eruption was observed in the He II
λ304 filter by the two EUV Imagers (EUVI) telescopes aboard
the STEREO A and B spacecrafts. The high spatial resolution
(~1farcs5 pixel-1) EUVI images have been used to infer
via triangulation the three-dimensional (3D) shape and orientation
of the prominence sime12 minutes after the beginning (13:40 UT) of
the eruption. At this time, the prominence has the shape of a "hook"
with the base anchored at the Sun. The "hook" prominence is highly
inclined southward with respect to the radial direction, has an average
thickness of 0.061 R sun, a length of 0.43 R sun,
and lies in first approximation on a plane inclined by ~54fdg5 with
respect to the line of sight. Thanks to the very high temporal cadence
(~37 s) of EUVI observations it has been possible also to infer the 3D
early eruption trajectory. In the following ~20 minutes the prominence
rotates westward, undergoing a strong latitudinal acceleration, ~3
times larger than the radial acceleration. In this time interval,
the prominence expands in a direction mainly parallel to the plane of
the sky; the total volume occupied by the plasma increases by a factor
of ~8, while the prominence thickness increases only by ~12%. This is
related to the fact that the early prominence expansion is anisotropic
and occurs mainly on a plane parallel to the plane of the sky. Even if
the small-scale spatial distribution of the erupting material observed
in the He II EUVI images is quite complex, both the approximately planar
shape and the successive planar expansion suggest that on larger spatial
scales the prominence can be globally approximated as a two-dimensional
"ribbon-like" feature, instead of a 3D twisted flux tube.
Title: Interpretation of the SOHO/UVCS observations of two CME-driven
shocks
Authors: Mancuso, Salvatore; Bemporad, Alessandro
Bibcode: 2009AdSpR..44..451M
Altcode:
We report on the analysis of two fast CME-driven shocks observed with
the UltraViolet Coronagraph Spectrometer (UVCS) on board the Solar and
Heliospheric Observatory (SOHO). The first event, detected on 2002 March
22 at 4.1 R⊙ with the UVCS slit placed in correspondence
with the flank of the expanding CME surface, represents the highest UV
detection of a shock obtained so far with the UVCS instrument in the
corona. The second one, detected on 2002 July 23 at 1.6 R⊙
with the UVCS slit placed in correspondence with the front of the
expanding CME surface, shows an anomalous deficiency of ion heating
with respect to what observed in previous CME/shocks observed by UVCS,
possibly reflecting the effect of different coronal plasma conditions
over the solar cycle. From the two different sets of observations we
derived an estimate for the shock compression ratio X, which turns out
to be X = 2.4 ± 0.2 and X = 2.2 ± 0.1, respectively, for the first and
second event. Comparison between the two events provides complementary
perspectives on the dynamical evolution of CME-driven shocks.
Title: Morphology and density structure of post-CME current sheets
Authors: Vršnak, B.; Poletto, G.; Vujić, E.; Vourlidas, A.; Ko,
Y. -K.; Raymond, J. C.; Ciaravella, A.; Žic, T.; Webb, D. F.;
Bemporad, A.; Landini, F.; Schettino, G.; Jacobs, C.; Suess, S. T.
Bibcode: 2009A&A...499..905V
Altcode: 2009arXiv0902.3705V
Context: Eruption of a coronal mass ejection (CME) drags and “opens”
the coronal magnetic field, presumably leading to the formation
of a large-scale current sheet and field relaxation by magnetic
reconnection.
Aims: We analyze the physical characteristics
of ray-like coronal features formed in the aftermath of CMEs, to
confirm whether interpreting this phenomenon in terms of a reconnecting
current sheet is consistent with observations.
Methods: The study
focuses on measurements of the ray width, density excess, and coronal
velocity field as a function of the radial distance.
Results: The
morphology of the rays implies that they are produced by Petschek-like
reconnection in the large-scale current sheet formed in the wake of
CME. The hypothesis is supported by the flow pattern, often showing
outflows along the ray, and sometimes also inflows into the ray. The
inferred inflow velocities range from 3 to 30 km s-1, and
are consistent with the narrow opening-angle of rays, which add up to a
few degrees. The density of rays is an order of magnitude higher than
in the ambient corona. The density-excess measurements are compared
with the results of the analytical model in which the Petschek-like
reconnection geometry is applied to the vertical current sheet, taking
into account the decrease in the external coronal density and magnetic
field with height.
Conclusions: The model results are consistent
with the observations, revealing that the main cause of the density
excess in rays is a transport of the dense plasma from lower to higher
heights by the reconnection outflow.
Title: The Role of Lateral Magnetic Reconnections in Solar Eruptive
Events
Authors: Soenen, Alexander; Poedts, S.; Bemporad, A.
Bibcode: 2009SPD....40.2210S
Altcode:
On December 10-11, 2005 a slow CME occurred in between two coronal
streamers in the Western hemisphere. SOHO/MDI magnetograms show a
multipolar magnetic configuration at the photosphere consisting of a
complex of active regions located at the CME source and two bi-poles
at the base of the lateral coronal streamers. White light observations
reveal that the expanding CME affects both of the lateral streamers and
induces the release of plasma within or close to them. These transient
phenomena are possibly due to magnetic reconnections induced by the
CME expansion that occurs either inside the streamer current sheet or
between the CME flanks and the streamer. Our observations show
that CMEs can be associated to not only a single reconnection process
at a single location in the corona, but also to many reconnection
processes occurring at different times and locations around the flux
rope. Numerical simulations are used to demonstrate that the observed
lateral reconnections can be reproduced. These simulations suggest that
the shear to be applied to the erupting arcade decreases as the number
of lateral induced reconnections increases. The observed secondary
reconnections associated to CMEs facilitate the CME release by globally
decreasing the magnetic tension of the corona. Future CME models should
therefore take into account the lateral reconnection effect.
Title: Comparison of Large-Scale Density Fluctuations in the Outer
Corona and in the Inner Heliosphere for Both Fast and Slow Solar Wind
Authors: Telloni, D.; Bruno, R.; Antonucci, E.; D'Amicis, R.;
Bemporad, A.
Bibcode: 2008AGUFMSH13B1544T
Altcode:
The low frequency spectra of the proton density of fast and slow
solar wind streams, measured in the inner heliosphere with the
HELIOS 2 in-situ instrumentation, are compared with those due to
the large-scale density fluctuations observed with the Ultraviolet
Coronagraph Spectrometer, UVCS/SOHO, in the outer corona where the
streams are accelerated. The interplanetary and coronal data have
been detected during solar minimum of different activity cycles. The
density fluctuations exhibit the same low-frequency spectral dependence,
1/f2, both in the corona and in the inner heliosphere, thus suggesting
that the discontinuities resulting in the 1/f2 noise, observed in the
interplanetary space, are likely to have a coronal origin. The present
study shows that in the outer corona the fast wind plasma is mainly
consisting of Alfvén fluctuations as in the inner heliosphere. Coherent
structures, on the other hand, are mainly found in the slow coronal
wind. In addition, a high degree of phase synchronization is observed
in the slow solar wind fluctuations both at coronal and heliospheric
levels. This is an indication that the phase coherent structures
observed in the interplanetary medium in the low-speed streams are
likely to be advected directly from the acceleration regions of the
slow solar wind, rather than resulting as a product of stream-stream
dynamic interactions in the heliosphere.
Title: Spectroscopic Detection of Turbulence in Post-CME Current
Sheets
Authors: Bemporad, A.
Bibcode: 2008ApJ...689..572B
Altcode:
Plasma in post-CME current sheets (CSs) is expected to be highly
turbulent because of the tearing and coalescence instability and/or
local microscopic instabilities. For this reason, in the last decade
the inconsistency between the observed (~104-105
km) and the expected (~1-10 m) CS thickness has been tentatively
explained in many MHD models as a consequence of plasma turbulence
that should be able to significantly broaden the CS. However, from the
observational point of view, little is known about this subject. A few
post-CME CSs have been observed in UVCS spectra as a strong emission
in the high-temperature [Fe XVIII] line, usually unobservable in the
solar corona. In this work, published data on post-CME CSs observed
by UVCS are reanalyzed, concentrating for the first time on the
evolution of turbulence derived from the nonthermal broadening of the
[Fe XVIII] line profiles. Derived turbulent speeds are on the order
of ~60 km s-1 a few hours after the CME and slowly decay
down to ~30 km s-1 in the following 2 days. From this
evolution the anomalous diffusivity due to microinstabilities has been
estimated, and the scenario of multiple small-scale reconnections is
tested. Results show that the existence of many (~10-11
to 10-17 μCS m-3) microscopic CSs (μCSs) of
small sizes (~10-104 m) could explain not only the high CS
temperatures but also the much larger observed thickness of macroscopic
CSs, thanks to turbulent broadening.
Title: Reconnection in a slow Coronal Mass Ejection
Authors: Poletto, G.; Bemporad, A.; Landini, F.; Romoli, M.
Bibcode: 2008AnGeo..26.3067P
Altcode:
This paper aims at studying reconnection occurring in the aftermath
of the 28 May 2004, CME, first imaged by the LASCO (Large Angle and
Spectrometric Coronagraph) C2 at 11:06 UT. The CME was observed in
White Light and UV radiation: images acquired by the LASCO C2 and C3
coronagraphs and spectra acquired by UVCS (Ultraviolet Coronagraph
Spectrometer) allowed us to identify the level at which field lines,
stretched outwards by the CME ejection, reconnect below the CME
bubble. As the CME propagates outwards, reconnection occurs at
increasingly higher levels. The process goes on at a low pace for
several hours: here we give the profile of the reconnection rate
vs. heliocentric distance over a time interval of ≍14 h after the CME
onset, extending estimates of the reconnection rate to larger distances
than previously inferred by other authors. The reconnection rate appears
to decrease with time/altitude. We also calculate upper and lower limits
to the density in the diffusion region between 4 and 7 R⊙
and conclude by comparing estimates of the classical and anomalous
resistivity in the diffusion region with the value inferred from the
data. The latter turns out to be ≥5 order of magnitudes larger than
predicted by classical or anomalous theories, pointing to the need of
identifying the process responsible for the observed value.
Title: Magnetic reconnection processes induced by a CME expansion
Authors: Bemporad, A.; Poletto, G.; Landini, F.; Romoli, M.
Bibcode: 2008AnGeo..26.3017B
Altcode:
On 10 11 December 2005 a slow CME occurred in the Western Hemisphere
in between two coronal streamers. SOHO/MDI magnetograms show a
multipolar magnetic configuration at the photosphere: a complex of
active regions located at the CME source and two bipoles at the base of
the lateral coronal streamers. White light observations reveal that the
CME expansion affects both of them and induces the release of plasma
within or close to the nearby streamers. These transient phenomena are
possibly due to magnetic reconnections induced by the CME expansion and
occurring inside the streamer current sheet or between the CME flanks
and the streamer. These events have been observed by the SOHO/UVCS
with the spectrometer slit centered at 1.8 R⊙ over about
a full day. In this work we focus on the interaction between the CME
and the streamer: the UVCS spectral interval included UV lines from
ions at different temperatures of maximum formation such as O VI,
Si XIII and Al Xi. These data gave us the opportunity to infer the
evolution of plasma temperature and density at the reconnection site
and adjacent regions. These are relevant to characterize secondary
reconnection processes occurring during a CME development.
Title: Low-Frequency Lyα Power Spectra Observed by UVCS in a Polar
Coronal Hole
Authors: Bemporad, A.; Matthaeus, W. H.; Poletto, G.
Bibcode: 2008ApJ...677L.137B
Altcode:
The occurrence of f-1 noise in interplanetary magnetic fields
(in the 1 × 10-5 to 1 × 10-4 Hz band) and other
plasma parameters has now been known for about 20 years and has been
recently identified also in the photospheric magnetic fields. However,
the relationship between interplanetary and solar fluctuation spectra
and the identification of their sources at the Sun are problems
that still need to be addressed. Moreover, interplanetary density
and magnetic field power spectra show a f-2 interval at
frequencies smaller that ~6 × 10-4 Hz whose source on the
Sun is at present not fully understood. In this work we report on the
first study of low-frequency density fluctuations in the solar corona
at 2.1 R⊙. In 2006 June the Ultraviolet Coronagraph
Spectrometer (SOHO UVCS) observed over a period of about 9.2 days
H Lyα intensity fluctuations at 2.1 R⊙ over a polar
coronal hole. The Lyα intensity power spectra S(f) (related mainly to
density fluctuations) showed a S(f) propto f-2 frequency
interval between 2.6 × 10-6 and 3.0 × 10-5
Hz and a S(f) propto f-1 frequency interval between 3.0
× 10-5 and 1.3 × 10-4 Hz. The detection of a
f-2 interval, in agreement with interplanetary density and
magnetic field power spectra, has been also predicted in solar wind
models as a consequence of phase-mixing mechanisms of waves propagating
in coronal holes. High-latitude power spectra show a f-1
band approximately in the same frequency interval where f-1
noise has been detected in interplanetary densities, and interplanetary
and photospheric magnetic fields, providing a connection between
photospheric, coronal, and interplanetary f-1 noises.
Title: Interpretation of the UVCS/SoHO observations of the 2002
March 22 and July 23 CME-driven shocks
Authors: Mancuso, Salvatore; Bemporad, A.
Bibcode: 2008cosp...37.1898M
Altcode: 2008cosp.meet.1898M
We report on the analysis of two peculiar fast CME-driven shocks
observed with the UltraViolet Coronagraph Spectrometer (UVCS)
on board the Solar and Heliospheric Observatory (SoHO). The first
event, detected on 2002 March 22 at 4.1 solar radii with the UVCS
slit placed in correspondence with the flank of the expanding CME
surface, represents the highest UV detection of a shock obtained so
far with the UVCS instrument in the corona. The second one, detected
on 2002 July 23 at 1.6 solar radii with the UVCS slit placed in
correspondence with the front of the expanding CME surface, shows an
anomalous deficiency of ion heating with respect to what observed in
previous CME/shocks observed by UVCS, possibly reflecting the effect
of different coronal plasma conditions over the solar cycle. The two
different sets of observations yield complementary perspectives on
the dynamical evolution of CME-driven shocks.
Title: A study of Lyman-alpha power spectra observed by UVCS over
a polar coronal hole
Authors: Bemporad, Alessandro; Matthaeus, W. H.; Poletto, G.
Bibcode: 2008cosp...37..239B
Altcode: 2008cosp.meet..239B
First results from the Hinode/SOT instrument demonstrated that
the upper chromosphere is permeated by Alfvén waves that, despite
reflections occurring in the transition region, propagate e into
the corona. However, it is at present not fully understood how this
propagation occurs and if these waves are eventually suppressed or
enhanced in the solar wind before their detection in the interplanetary
medium. In this work we start addressing some of these questions by
carrying out a power spectral analysis of the Hydrogen Lyman-α line
intensity fluctuations observed by the SOHO/UVCS instrument over a polar
coronal hole. Data were acquired at 2.1 R over a period of about 9.2
days with a time resolution of 300 s between latitudes of 54° S and
90° S. Lyman-α power spectra, in first approximation representative
of density fluctuations, show two spectral bands: a lower frequency
f -2 band and a higher frequency f -1 band. In particular, the f -1
band is present approximately in the same frequency interval where f -1
noise has been detected in interplanetary densities, and interplanetary
and photospheric magnetic fields; this provides for the first time a
strong connection between photospheric, coronal and interplanetary f
-1 noises. Future developments of this work are also outlined.
Title: Are CMEs globally affecting the corona by reconnection
occurring on different scales?
Authors: Bemporad, Alessandro
Bibcode: 2008cosp...37..238B
Altcode: 2008cosp.meet..238B
First results from the Hinode/XRT and SOT observations revealed
that X-ray jets on polar coronal holes are much more frequent than
previously detected from Yohkoh data and that small jets, similar
to the X-ray anemone jets, are occurring even above active regions
in the chromosphere. This confirms that magnetic reconnection,
a fundamental process in flare-CME models, is an ubiquitous
phenomenon occurring on the Sun on very different spatial and temporal
scales. Previous SOHO/LASCO, EIT and UVCS observations showed that,
during the development of CMEs, the magnetic reconnection occurring at
chromospheric and low coronal levels is responsible for the formation of
the post-eruption loops connected with the CME bubble via an elongated
current sheet. More recent LASCO and UVCS observations presented here
reveal that the CME expansion may globally affect the surrounding
solar corona being responsible for further reconnection processes
occurring on larger spatial scales along the nearby streamer current
sheets or between the CME flanks and the streamer boundaries, leading
to secondary eruptions. From these observations we have been able to
derive informations on the physical conditions at the reconnection
regions and to infer the evolution of the magnetic reconnection rate:
possible transitions from the small scale Petschek-type to the larger
scale Sweet & Parker type reconnections, envisaged in some current
sheet models, are also discussed.
Title: A review of SOHO/UVCS observations of sungrazing comets
Authors: Bemporad, A.; Poletto, G.; Raymond, J.; Giordano, S.
Bibcode: 2007P&SS...55.1021B
Altcode:
In the last 10 years more than 1000 sungrazing comets have been
discovered by the LASCO coronagraphs aboard SOHO the spacecraft; from
this huge amount of data it has been possible to study the common origin
of these comets and to explain some of the main peculiarities observed
in their lightcurves. Moreover, the UV Coronagraph Spectrometer (UVCS)
aboard SOHO allowed EUV spectroscopy of sungrazers in the final stage
of their trajectory (i.e. between 1.4 and 10 solar radii), but a few
sungrazers have been observed with this instrument. In this paper
we review the main results from the UVCS observation of sungrazers
C/1996 Y1, C/2000 C6 and C/2001 C2, discussing also the first possible
detection of two fragments and the determination of the pyroxene dust
grain number density in the latter one. Preliminary results on the
UVCS data interpretation of a sungrazer observed in 2002 (C/2002 S2)
are also presented here.
Title: Density and Magnetic Field Signatures of Interplanetary
1/f Noise
Authors: Matthaeus, W. H.; Breech, B.; Dmitruk, P.; Bemporad, A.;
Poletto, G.; Velli, M.; Romoli, M.
Bibcode: 2007ApJ...657L.121M
Altcode:
We investigate the occurrence of 1/f noise in the interplanetary
density and the magnetic field at varying heliocentric latitudes. The
characteristic spectral amplitudes can be found in Ulysses density
and magnetic data in the expected frequency ranges at all available
latitudes, ranging from the ecliptic plane to more than 80°. Average
spectra indicate a latitudinal variation, with a 1/f density signal
becoming more pronounced in higher latitude bands. Azimuthal spectral
analysis of solar magnetogram data using the SOHO Michelson Doppler
Interferometer also shows 1/f noise in the photospheric magnetic field,
most clearly at high latitude. Accordingly, we discuss possibilities
that the 1/f signal arises at varying altitudes, possibly surviving
coronal dynamics. This raises questions that may be addressed in future
studies using spectroscopic, white light, and radio scintillation data.
Title: Results from recent studies of CMEs with SOHO/UVCS .
Authors: Bemporad, A.
Bibcode: 2007MmSAI..78..600B
Altcode:
In this work we review recent results obtained in the study of Coronal
Mass Ejections (CMEs) from analysis of data acquired by the UltraViolet
Coronagraph Spectrometer (UVCS) on SOHO. These studies gave us the
opportunity to identify, during an event observed on November 2002,
the presence of a Current Sheet (CS) formed as a consequence of the
post-CME magnetic reconnection. We derived the temporal evolution of
CS physical parameters, at present not completely known and essential
for the development of better CME models. In a second study, based
both on UV and white light pB observations of an event occurred on
January 2000, we inferred the density and temperature distribution
in the core of a CME and in the surrounding region. In a further
research area we studied CME events characterized by a small angular
extension (narrow CMEs): in a first work we proposed a mechanism for
their production, while in a second work we derived physical parameters
of the plasma ejected in a series of homologous events. At present
other studies are in progress, focussing on the CSs development from
the time they first appear at lower coronal levels up to the time they
reach higher heliocentric and interplanetary distances, where these
structures are observed by respectively white light coronagraphs in
in situ instruments.
Title: A Comprehensive Study of the Initiation and Early Evolution
of a Coronal Mass Ejection from Ultraviolet and White-Light Data
Authors: Bemporad, A.; Raymond, J.; Poletto, G.; Romoli, M.
Bibcode: 2007ApJ...655..576B
Altcode:
In this work we analyze simultaneous UV and white-light (WL)
observations of a slow CME that occurred on 2000 January 31. Unlike
most CMEs studied in the UV so far, this event was not associated
with a flare or filament eruption. Based on vector magnetograph
data and magnetic field models, we find that field disruption in an
active region (AR) was driven by flux emergence and shearing motions,
leading to the CME and to post-CME arcades seen in the EUV. WL images,
acquired by the Mark IV coronagraph at the Mauna Loa Observatory,
allowed us to identify the CME front, bubble, and core shortly
(about 1 hr) after the CME ejection. From polarized brightness (pB)
Mauna Loa data we estimated the mass and electron densities of the
CME. The CME mass increases with time, indicating that about 2/3 of
the mass originates above 1.6 Rsolar. Analysis of the UV
spectra, acquired by the Solar and Heliospheric Observatory Ultraviolet
Coronagraph Spectrometer (SOHO UVCS) at 1.6 and 1.9 Rsolar,
allowed us to derive the electron temperature distribution across the
CME. The temperature maximizes at the CME core and increases between
1.6 and 1.9 Rsolar. This event was unusual, in that the
leading edge and the CME core were hotter than the ambient corona. We
discuss magnetic heating and adiabatic compression as explanations
for the high temperatures in the core and leading edge, respectively.
Title: SOHO UVCS and Mauna Loa Mark IV Observations of a Slow CME
below 2 Solar Radii
Authors: Bemporad, A.; Poletto, G.; Raymond, J. C.
Bibcode: 2006ESASP.617E..24B
Altcode: 2006soho...17E..24B
No abstract at ADS
Title: Current Sheet Evolution in the Aftermath of a CME Event
Authors: Bemporad, A.; Poletto, G.; Suess, S. T.; Ko, Y. -K.;
Schwadron, N. A.; Elliott, H. A.; Raymond, J. C.
Bibcode: 2006ApJ...638.1110B
Altcode:
We report on SOHO UVCS observations of the coronal restructuring
following a coronal mass ejection (CME) on 2002 November 26, at the
time of a SOHO-Ulysses quadrature campaign. Starting about 1.5 hr
after a CME in the northwest quadrant, UVCS began taking spectra
at 1.7 Rsolar, covering emission from both cool and hot
plasma. Observations continued, with occasional gaps, for more than
2 days. Emission in the 974.8 Å line of [Fe XVIII], indicating
temperatures above 6×106 K, was observed throughout the
campaign in a spatially limited location. Comparison with EIT images
shows the [Fe XVIII] emission to overlie a growing post-flare loop
system formed in the aftermath of the CME. The emission most likely
originates in a current sheet overlying the arcade. Analysis of the [Fe
XVIII] emission allows us to infer the evolution of physical parameters
in the current sheet over the entire span of our observations: in
particular, we give the temperature versus time in the current sheet
and estimate its density. At the time of the quadrature, Ulysses was
directly above the location of the CME and intercepted the ejecta. High
ionization state Fe was detected by the Ulysses SWICS throughout the
magnetic cloud associated with the CME, although its rapid temporal
variation suggests bursty, rather than smooth, reconnection in the
coronal current sheet. The SOHO-Ulysses data set provided us with the
unique opportunity of analyzing a current sheet structure from its
lowest coronal levels out to its in situ properties. Both the remote
and in situ observations are compared with predictions of theoretical
CME models.
Title: Lyman-α Observations of Sungrazing Comets with the SOHO/UVCS
Instrument
Authors: Bemporad, A.; Poletto, G.; Raymond, J.; Giordano, S.
Bibcode: 2006aogs....3..171B
Altcode:
The Large angle and spectrometric coronagraphs aboard the Solar
and helio-spheric observatory (SOHO) spacecraft observed a large
(more than 1000) number of sungrazers. This led to many studies which
tried to explain their origin and the peculiar shape of the observed
cometary lightcurves. However, in the last years a few sungrazers
have been observed also in the hydrogen Lyman-α spectral line by
the UV coronagraph spectrometer on SOHO. This instrument allowed to
perform UV spectroscopical observations of sungrazing comets on their
final stage of life at projected heliocentric distances between 1.4
and 10 solar radii. Ultra violet coronagraph spectrometer (UVCS)
detected in the sungrazer UV spectra mainly the Lyman-α spectral
line. Typically, emission in this line originates in the hydrogen cloud
produced by the water photodis-sociation, but, at these low heights,
it is necessary to take into account also strong interaction processes
(e.g., mass-loading and charge exchange) between the solar wind and
the outgassed materials. From these observations, it has been possible
to estimate cometary parameters such as the outgassing rates and the
nucleus sizes, as well as parameters of the coronal plasma encountered
by the comet. In this work we review the main results derived from the
UVCS observations of sungrazing comets: the detection of a “hidden”
mass below ∼6R⊙, the indirect and direct evidences for
the occurrence of fragmentation processes and a tentative estimate
for the pyroxene dust grain number density. Moreover, we present here
preliminary results on the UVCS data interpretation of a sungrazer
observed in 2002.
Title: Evidence for pyroxene dust grains in C/2001 C2 sungrazing comet
Authors: Bemporad, A.; Poletto, G.; Raymond, J. C.
Bibcode: 2006AdSpR..38.1972B
Altcode:
In this paper we analyze SOHO/UVCS data of the sungrazing comet C/2001
C2, a member of the Kreutz family, that was observed on February 7,
2001, at the heliocentric distances of 4.98 and 3.60 solar radii. This
comet splits in a main nucleus and a fragment which have been
identified in UV data. A study of the cometary Hydrogen Lyα emission
from these two objects revealed that the Lyα signal from the fragment
decays exponentially with time, while the signal from the main object
consists of an exponentially decaying term superposed onto a constant
background. The latter emission has been ascribed to the sublimation of
pyroxene dust grains, whose end products neutralize coronal protons via
charge exchange processes. This interpretation allowed us to estimate,
for the first time, the number density of pyroxene dust grains in a
sungrazing comet.
Title: Recursive Narrowcmes Within a Coronal Streamer
Authors: Bemporad, A.; Sterling, A. C.; Moore, R. L.; Poletto, G.
Bibcode: 2005ESASP.600E.153B
Altcode: 2005ESPM...11..153B; 2005dysu.confE.153B
No abstract at ADS
Title: A New Variety of Coronal Mass Ejection: Streamer Puffs from
Compact Ejective Flares
Authors: Bemporad, A.; Sterling, Alphonse C.; Moore, Ronald L.;
Poletto, G.
Bibcode: 2005ApJ...635L.189B
Altcode:
We report on SOHO UVCS, LASCO, EIT, and MDI observations of a
series of narrow ejections that occurred at the solar limb. These
ejections originated from homologous compact flares whose source
was an island of included polarity located just inside the base of
a coronal streamer. Some of these ejections result in narrow CMEs
(``streamer puffs'') that move out along the streamer. These streamer
puffs differ from ``streamer blowout'' CMEs in that (1) while the
streamer is transiently inflated by the puff, it is not disrupted, and
(2) each puff comes from a compact explosion in the outskirts of the
streamer arcade, not from an extensive eruption along the main neutral
line of the streamer arcade. From the observations, we infer that
each streamer puff is produced by means of the inflation or blowing
open of an outer loop of the arcade by ejecta from the compact-flare
explosion in the foot of the loop. So, in terms of their production,
our streamer puffs are a new variety of CME.
Title: Early Evolution of a CME from White Light and UV Observations
Authors: Bemporad, A.; Poletto, G.; Raymond, J. C.
Bibcode: 2005ESASP.592..711B
Altcode: 2005ESASP.592E.143B; 2005soho...16E.143B
No abstract at ADS
Title: Current Sheet Evolution in the Aftermath of a CME
Authors: Bemporad, A.; Poletto, G.; Suess, S. T.; Ko, Y. -K.;
Schwadron, N. A.; Elliott, H. A.; Raymond, J. C.
Bibcode: 2005ESASP.592..715B
Altcode: 2005soho...16E.144B; 2005ESASP.592E.144B
No abstract at ADS
Title: UVCS Observation of Sungrazer C/2001 C2: Possible Comet
Fragmentation and Plasma-Dust Interactions
Authors: Bemporad, A.; Poletto, G.; Raymond, J. C.; Biesecker, D. A.;
Marsden, B.; Lamy, P.; Ko, Y. -K.; Uzzo, M.
Bibcode: 2005ApJ...620..523B
Altcode:
In this paper we analyze SOHO Ultraviolet Coronagraph Spectrometer
(UVCS) observations of the sungrazing comet C/2001 C2, a member of the
Kreutz family, observed on 2001 February 7 at heliocentric distances
of 4.98 and 3.60 Rsolar. This comet apparently went through
sequential fragmentation events along its path: further indication of
fragmentation processes is provided by UVCS observations, which show
the presence of two separate tails in the 4.98 Rsolar data
set, which we interpret as two fragments unresolved by LASCO images,
one of which sublimates before reaching 3.60 Rsolar. The
cometary hydrogen Lyα signal, decaying exponentially with time,
has been interpreted in terms of the H2O outgassing rate
and the interactions of coronal protons with atoms created by the
photodissociation of water. However, one of the fragments shows an
additional Lyα contribution, constant with time, which adds to the
temporally decaying signal. This contribution has been ascribed to
the sublimation of pyroxene dust grains, whose end products neutralize
coronal protons via charge exchange processes. Hence, the two fragments
have different composition; differences throughout the comet body may
have been the primary cause for the comet fragmentation.
Title: Post-CME events: cool jets and current sheet evolution
Authors: Bemporad, A.; Poletto, G.; Suess, S. T.
Bibcode: 2005IAUS..226...77B
Altcode:
In this work we focus on UVCS data acquired during the November 2002
SOHO-Ulysses quadrature, at an altitude of 1.7 R⊙ over a
range of latitudes centered around 27 °N in the western quadrant. A
couple of hours before our observations started, a CME event (November
26, 15:30 UT) originating at about 27 °N, disrupted the coronal
configuration of the region. In the ∼ 2.3 days following the event
UVCS detected emission in the neutral H Ly β and Ly γ lines as well
as in lines from both high and low ionization ions such as C iii, O vi,
Si viii, ix and xii, Fe x and xviii. Enhanced emission from the hot
Fe xviii ion (log Tmax = 6.7), lasting nearly to the end of
our observations and originating in a region between 10 °N and 30 °N,
has been identified with a post-CME current sheet. Our interpretation
is supported by EIT Fe xii images which show a system of loops at
increasingly higher altitudes after the event. Northward of the CME,
UVCS observed repeated, sudden and short lived emission peaks in the
"cool" Ly β, Ly γ, C iii and O vi lines. These events seem to be
the extension at higher altitudes of the chromospheric plasma jets
observed in the EIT He ii images. Electron temperatures of both the
hot and cool region will be presented here and their time evolution
will also be illustrated.
Title: A Detection of the Same Hot Plasma in the Corona - During a
CME - and Later at Ulysses
Authors: Suess, S. T.; Poletto, G.; Bemporad, A.
Bibcode: 2004AGUFMSH21B0402S
Altcode:
We show direct evidence for the same very hot plasma being detected
remotely from SOHO in the corona and subsequently, in situ, at Ulysses
in the solar wind. This is, to our knowledge, the first time that
such an unambiguous identification has been made in the case of hot
plasma. This detection complements studies correlating other plasma
and field properties observed in situ to the properties measured
at the source in the corona. This observation takes advantage
of a SOHO-Sun-Ulysses quadrature, during which the Sun-Ulysses
included angle is 90o and it is possible to observe in
situ with Ulysses instruments the same plasma that has previously
been remotely observed with SOHO instruments in the corona on the
limb of the Sun. The identification builds on an existing base of
separate SOHO and interplanetary detections of hot plasma. SOHO/UVCS
has found evidence for very hot coronal plasma in current sheets
in the aftermath of CMEs (Ciaravella et al., 2002; Raymond et al.,
2003; Ko et al., 2002) in the [Fe XVIII] λ 974 Å line, implying a
temperature on the order of 6 × 106 K. This temperature
is unusually high even for active regions, but is compatible with the
high temperature predicted in current sheets. In the solar wind, ACE
data from early 1998 to middle 2000 revealed high frozen-in Fe charge
state (Fe16+)in many cases to be present in interplanetary
plasma (Lepri et al., 2004). These identifications were associated with
ICMEs. Ciaravella, A., Raymond, J. C., Li, J., Reiser, P., Gardner,
L. D., Ko, Y.-K., & Fineschi, S. 2002, Astrophys. J., 575, 1116 Ko,
Y.-K., Raymond, J. C., Li, J., Ciaravella, A., Michels, J., Fineschi,
S., & Wu, R. 2002, Astrophys. J., 578, 979 Lepri, S. T., &
Zurbuchen, T. H. 2004, J. Geophys. Res., 109(A1), A01112 Raymond,
J. C., Ciaravella, A., Dobrzycka, D., Strachan, L., Ko, Y.-K., &
Uzzo, M. 2003, Astrophys. J., 597, 1106
Title: Evidence for the Same Hot Plasma after Coronal Mass Ejection
Events, in Both Remote and In Situ Observations
Authors: Poletto, G.; Suess, Steven T.; Bemporad, Alessandro;
Schwadron, Nathan A.; Elliott, Heather A.; Zurbuchen, Thomas H.; Ko,
Y. -K.
Bibcode: 2004ApJ...613L.173P
Altcode:
We present here evidence for highly ionized Fe observed both in the
corona, in the aftermath of a coronal mass ejection, and, after
propagation, in situ. The apparent source temperature is greater
than 6 MK. To our knowledge, this is the first time that such an
unambiguous identification has been made. This detection complements
studies correlating other properties of plasma observed in situ to the
same properties of the same plasma remotely observed at its source in
the corona.
Title: A slow streamer blowout at the Sun and Ulysses
Authors: Suess, S. T.; Bemporad, A.; Poletto, G.
Bibcode: 2004GeoRL..31.5801S
Altcode: 2004GeoRL..3105801S
On 10 June 2000 a streamer on the southeast limb slowly disappeared from
LASCO/C2 over ~10 hours. A small CME was reported in C2. A substantial
interplanetary CME (ICME) was later detected at Ulysses, which was at
quadrature with the Sun and SOHO at the time. This detection illustrates
the properties of an ICME for a known solar source and demonstrates
that the identification can be done even beyond 3 AU. Slow streamer
blowouts such as this have long been known but are little studied.
Title: Evidence for pyroxene dust grains in C/2001 C2 sungrazing comet
Authors: Bemporad, A.; Poletto, G.; Raymond, J.
Bibcode: 2004cosp...35.3526B
Altcode: 2004cosp.meet.3526B
In this paper we analyze SOHO/UVCS data of the sungrazing comet C/2001
C2, a member of the Kreutz family, observed on February 7, 2001, at
the heliocentric distances of 4.94 and 3.44 solar radii. As confirmed
also by LASCO/C3 images, this comet splits in a main nucleus and a
fragment which have been identified also in our UV data. A study of
the cometary Hydrogen Lyα emission from these two objects showed
a different behaviour: the Lyα signal from the fragment decays
exponentially with time, as expected in terms of the H_2O outgassing
rate and of the charge transfer between the coronal protons and atoms
created by the photodissociation of water. On the contrary the signal
from the main object consists of an exponentially decaying term plus
a constant background. This secondary component has been ascribed to
the sublimation of pyroxene dust grains, whose end products neutralize
coronal protons via charge exchange processes. Hence, the two fragments
have a different composition; differences throughout the comet body
may have been the primary cause for the comet fragmentation.
Title: Preliminary analysis of a CME observed by SOHO and Ulysses
experiments
Authors: Bemporad, A.; Poletto, G.; Romoli, M.; Suess, S. T.
Bibcode: 2003ESASP.535..567B
Altcode: 2003iscs.symp..567B
Over the last week of November 2002 SOHO/LASCO observed several Coronal
Mass Ejections, most of which occurring in the NW quadrant. At that
time SOHO/UVCS was involved in a SOHO-Sun-Ulysses quadrature campaign,
making observations off the west limb of the Sun, at a northern latitude
of 27°. Here we focus on data taken at 1.7 solar radii, over a time
interval of ≍7 hours, on 26/27 November, 2002, when a large streamer
disruption was imaged by LASCO C2 and C3 coronagraphs. UVCS spectra
revealed the presence of lines from both high and low ionization ions,
such as C III, O VI, Si VIII, IX and XII, Fe X and XVIII, which brighten
at different times, with a different time scale and at different
positions and are apparently related to different phenomena. In
particular, the intensity increase and fast disappearance of the C
III 977 Å line represents the passage through the UVCS slit of cold
material released in a jet imaged by EIT in the He II 304 Å line. The
persistent presence of the Fe XVIII 974 Å line is not easily related
to any special feature crossing the UVCS slit. We suggest to interpret
this behavior in terms of the reconnection events which lead to the
formation of loops observed in the EIT He II 304 Å line.
Title: Temporal Evolution of a Streamer Complex: Coronal and in Situ
Plasma Parameters
Authors: Bemporad, A.; Poletto, G.; Suess, S. T.; Ko, Y. K.; Parenti,
S.; Riley, P.; Romoli, M.; Zurbuchen, T. Z.
Bibcode: 2003ApJ...593.1146B
Altcode:
We report on observations acquired by the Ultraviolet Coronagraph
Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory
(SOHO), from 2000 June 10 to June 17 at the time of a SOHO-Sun-Ulysses
quadrature. UVCS took data at 1.6 and 1.9 Rsolar with a slit
normal to the solar radius and centered along the radial to Ulysses. A
streamer complex was sampled by UVCS throughout the quadrature
campaign, giving us the opportunity to derive plasma parameters
in different streamers and to compare them with plasma properties
measured in situ. Large Angle Spectroscopic Coronagraph images above 2
Rsolar helped us understand the temporal evolution of the
streamer complex. We derive densities, temperatures, and elemental
abundances in two streamers, which have different temperatures and
element abundances. In spite of these differences, both structures
have the same first ionization potential (FIP) bias. The Fe/O ratio,
which may be considered a proxy for the FIP effect, was measured in
situ by the Solar Wind Ion Composition Spectrometer aboard the Ulysses
spacecraft. Values of Fe/O measured in the corona at the sites where
in situ plasma originated agree with in situ Fe/O values.
Title: Physical parameters of coronal streamers near the maximum
phase of solar cycle
Authors: Bemporad, A.; Poletto, G.; Romoli, M.
Bibcode: 2003MmSAI..74..721B
Altcode:
During june 10-17, 2000 the Ultraviolet Coronograph Spectrometer
(UVCS) aboard the Solar and Heliospheric Observatory observed a
streamer complex. Data were acquired at the time of a SOHO-Sun-Ulysses
quadrature. We identify two streamers for which we derive electron
densities, temperatures and elemental abundances and we point out
differences and analogies between the two structures. We also derive
the coronal Fe/O, which we consider a proxy for the FIP effect and we
compare it with Fe/O values measured in situ by SWICS.
Title: Spatial and temporal behavior of the oxygen abundance in a
streamer complex
Authors: Bemporad, A.; Poletto, G.; Romoli, M.
Bibcode: 2002ESASP.506..545B
Altcode: 2002svco.conf..545B; 2002ESPM...10..545B
The determination of the abundance of trace elements in different solar
structures and in the solar wind may be crucial for the identification
of the solar wind sources. In the last few years, SOHO data allowed
an evaluation of the oxygen abundance at previously unattainable
coronal levels (Zangrilli et al., 2001). Analyses of streamer
data taken at the minimum of the solar activity cycle raised the
question of whether streamers' legs might be the site where slow wind
originates, because the oxygen abundance in the lateral branches of the
streamer, at coronal levels, turned out to be similar to the slow wind
abundance. In this work we analyse UVCS streamers observations, taken
at 1.6Rsolar, near the maximum phase of the activity cycle,
to check whether the behavior found at minimum is shared by streamers at
maximum. We derive also the abundance of oxygen in different streamers
and, within a streamer, across its axis, to get more information on
the spatial variability of the oxygen abundance. Our results show
that the oxygen abundance in different streamers may be significantly
different, implying that a more thorough analysis is needed before
drawing conclusions about the site where slow wind originates.
Title: Correnti stellari risultante del catalogo
astrografico. (Contribu. astrofisico, no 17, Oss. di Catania)
Authors: Bemporad, A.
Bibcode: 1935C&T....51...34B
Altcode:
No abstract at ADS
Title: Procedimenti di controllo per le effemeride
astronomiche. (Contribu. astrofisico, no 19, Oss. di Catania)
Authors: Bemporad, A.
Bibcode: 1935C&T....51R..35B
Altcode:
No abstract at ADS
Title: L'addensamento stellare in varie regioni del catalogo
astrofisico, no 20
Authors: Bemporad, A.
Bibcode: 1935C&T....51Q..35B
Altcode:
No abstract at ADS
Title: Misure di stelle doppoie
Authors: Bemporad, A.
Bibcode: 1934AN....254...37B
Altcode: 1935AN....254...37B
No abstract at ADS
Title: Occultazione di Venere da parte della Luna del 10 Aprile 1934
Authors: Bemporad, A.
Bibcode: 1934AN....252..265B
Altcode:
No abstract at ADS
Title: Misure di stelle doppie eseguite nel corso dei calcoli per
il Catalogo Astrografico di Catania
Authors: Bemporad, A.
Bibcode: 1932AN....246...23B
Altcode:
No abstract at ADS
Title: Misure di stelle doppie eseguite nel corso dei calcoli per
il Catalogo Astrografico di Catania
Authors: Bemporad, A.
Bibcode: 1932AN....244..353B
Altcode:
No abstract at ADS
Title: Eclisse totale di Luna del 26 settembre 1931
Authors: Bemporad, A.
Bibcode: 1932AN....244..359B
Altcode:
No abstract at ADS
Title: Mouvements propres qui ressortent des plaques du Catalogue
astrographique de Catane
Authors: Bemporad, A.
Bibcode: 1930JO.....13..136B
Altcode:
No abstract at ADS
Title: Sullo stato dei lavori del Catalogo Astrografico di Catania
Authors: Bemporad, A.
Bibcode: 1925MmSAI...3..166B
Altcode:
No abstract at ADS
Title: Circa un nuovo metodo di studio su i risultati di esperienze
Authors: Bemporad, A.
Bibcode: 1925MmSAI...3..414B
Altcode:
No abstract at ADS
Title: Giuseppe Piazzi (commemorazione)
Authors: Bemporad, A.
Bibcode: 1925MmSAI...3..396B
Altcode:
No abstract at ADS
Title: Recensione di una nota di Brown
Authors: Bemporad, A.
Bibcode: 1925MmSAI...3..553B
Altcode:
No abstract at ADS
Title: Necrologia di pasquale Moreno
Authors: Bemporad, A.
Bibcode: 1921MmSAI...2...95B
Altcode:
No abstract at ADS
Title: Necrologia di Bortolo Viaro
Authors: Bemporad, A.
Bibcode: 1921MmSAI...2..304B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche di 32 Geminorum
Authors: Bemporad, A.
Bibcode: 1921MmSAI...2...42B
Altcode:
No abstract at ADS
Title: Periodo di W-Ursae majoris
Authors: Bemporad, A.
Bibcode: 1921MmSAI...2..133B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche di 32 Geminorum
Authors: Bemporad, A.
Bibcode: 1920MmSAI...1...88B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche e studio del periodo della variabile
T Monocerotis
Authors: Bemporad, A.
Bibcode: 1920MmSAI...1..229B
Altcode:
No abstract at ADS
Title: Variabilità di 32 Geminorum
Authors: Bemporad, A.
Bibcode: 1920MmSAI...1...29B
Altcode:
No abstract at ADS
Title: Studio Dell'estinzione Atmosferica per Stelle Di Diversi
Tipi Spettrali
Authors: Bemporad, A.
Bibcode: 1918MmSS....7...94B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite Nel 1911-12
Nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1917MmSS....6..122B
Altcode:
No abstract at ADS
Title: Sullo Studio Fotometrico Delle Variabili
Authors: Bemporad, A.
Bibcode: 1916MmSS....5...57B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche eseguite nel 1911-12
nell'osservatorio astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1916MmSS....5...37B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche eseguite nel 1911-12
nell'Osservatorio astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1916MmSS....5..111B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel 1911 - 12
Nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1916MmSS....5..198B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel 1911-12
nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1916MmSS....5...69B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche eseguite nel 1911-12
nell'Osservatorio Astrofiscico di Catania
Authors: Bemporad, A.
Bibcode: 1916MmSS....5..125B
Altcode:
No abstract at ADS
Title: Anormalita del Massimo di Mira Ceti
Authors: Bemporad, A.
Bibcode: 1915MmSS....4...45B
Altcode:
No abstract at ADS
Title: Misure Assolute e Misure Differenziali Della Estinzione
Atmosferica
Authors: Bemporad, A.
Bibcode: 1915MmSS....4..135B
Altcode:
No abstract at ADS
Title: Sulla curva di luce di U Cephei
Authors: Bemporad, A.
Bibcode: 1914AN....199..217B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche di Mira Ceti eseguite a Capodimonte
Authors: Bemporad, A.
Bibcode: 1914AN....199...43B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche di RZ Cassiopeiae eseguite nel
R. Osservatorio di Catania
Authors: Bemporad, A.
Bibcode: 1913AN....195....1B
Altcode:
No abstract at ADS
Title: Sulla Curva di Luce Della Variabile RZ Cassiopeiae
Authors: Bemporad, A.
Bibcode: 1913MmSS....2..153B
Altcode:
No abstract at ADS
Title: Estinzione della luce a Catania
Authors: Bemporad, A.
Bibcode: 1912AN....192...99B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche di Mira Ceti eseguite nel
R. Osservatorio astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1912AN....192...69B
Altcode:
No abstract at ADS
Title: Stella sospetta di variabilita 22.1912 Geminorum
Authors: Bemporad, A.
Bibcode: 1912AN....191..151B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche della cometa 1911 c (Brooks)
Authors: Bemporad, A.
Bibcode: 1911AN....190..129B
Altcode: 1912AN....190..129B
No abstract at ADS
Title: Nuova variable 42.1911 Hydrae
Authors: Bemporad, A.
Bibcode: 1911AN....189..225B
Altcode:
No abstract at ADS
Title: Osservazioni fotometriche della Mira Ceti eseguite a Catania
dall'Ottobre 1909 al Marzo 1911.
Authors: Bemporad, A.
Bibcode: 1911AN....188..301B
Altcode:
No abstract at ADS
Title: Misure Fotometriche del Nucleo della Cometa di Halley eseguite
nel R. Osservatorio di Catania. II. Discussione dei risultati.
Authors: Bemporad, A.
Bibcode: 1911MmSSI..40..193B
Altcode:
No abstract at ADS
Title: Misure Fotometriche del Nucleo della Cometa di Halley Eseguite
nel R. Osservatorio di Catania. I. Le osservazioni.
Authors: Bemporad, A.
Bibcode: 1911MmSSI..40..163B
Altcode:
No abstract at ADS
Title: Nuova Variabile 42 1911 Hydrae
Authors: Bemporad, A.
Bibcode: 1911MmSSI..40..152B
Altcode:
No abstract at ADS
Title: Misure fotometriche del nucleo della cometa di Halley
Authors: Bemporad, A.
Bibcode: 1911AN....187....1B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche eseguite nel R. Osservatorio
astrofisico di Catania nel 1909
Authors: Bemporad, A.
Bibcode: 1910MmSSI..39...24B
Altcode:
No abstract at ADS
Title: La Teoria della Refrazione Astronomica Direttamenta Fondata
sui Risultati della Fisica dell'Atmosfera
Authors: Bemporad, A.
Bibcode: 1910MmSSI..39...79B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche eseguite nel R. Osservatorio
astrofisico di Catania nel 1909
Authors: Bemporad, A.
Bibcode: 1910MmSSI..39...55B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel R. Osservatorio
Astrofisico di Catania nel 1907 da A. Bemporad e A. Cavasino
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38....9B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel R. Osservatorio
Astrofisico di Catania nel 1907
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38...21B
Altcode:
No abstract at ADS
Title: Il Comparatore di Lastre in Uso nell'Osservatorio Astrofisico
di Catania
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38...56B
Altcode:
No abstract at ADS
Title: Sull'Assorbimento Subito dalla Radiazione Solare negli Strati
Atmosferici a Vari Altezze sull'Etna
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38...76B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel R. Osservatorio
Astrofisico di Catania nel 1908
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38..114B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel R. Osservatorio
Astrofisico di Catania nel 1908
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38..147B
Altcode:
No abstract at ADS
Title: 3. Osservazioni Fotometriche della Cometa 1908 c Morehouse
Authors: Bemporad, A.
Bibcode: 1909MmSSI..38...47B
Altcode:
No abstract at ADS
Title: Sulla curva diurna della radiazione solare
Authors: Bemporad, A.
Bibcode: 1908AN....179..305B
Altcode: 1909AN....179..305B
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel Triennio 1904-1906
nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1908MmSSI..37...90B
Altcode:
No abstract at ADS
Title: N. 3. Misure Fotometriche del Nucleo della Cometa Daniel
(1907 d)
Authors: Bemporad, A.; Cavasino, A.
Bibcode: 1908MmSSI..37...76B
Altcode:
No abstract at ADS
Title: La Curva Diurna delle Radiazione in Relazione alla Cosiddetta
Costante Solare
Authors: Bemporad, A.
Bibcode: 1908MmSSI..37..159B
Altcode:
A Proposito della Memoria del Prof J Scheiner: Untersuchungen uber
die Solar-konstante und die Temperatur der Sonnenphotosphare
Title: Osservazioni Alla Nota del Prof. Angström sull'Assorbimento
dei Gas
Authors: Bemporad, A.
Bibcode: 1908MmSSI..37..174B
Altcode:
No abstract at ADS
Title: Nuova variabile 33.1907 Persei (BD +49°499)
Authors: Bemporad, A.
Bibcode: 1907AN....175....5B
Altcode:
No abstract at ADS
Title: L'Assorbimento Selettivo delle Radiazioni Calorifiche Dedotto
da le Osservazioni Eseguite negli Osservatori di Catania e dell'Etna
nel Settembre 1904
Authors: Bemporad, A.; Mendola, L.
Bibcode: 1907MmSSI..36..165B
Altcode:
No abstract at ADS
Title: Misure Attinometriche Eseguite nel R. Osservatorio di Catania
dal Luglio 1904 all'Agosto 1905
Authors: Bemporad, A.; Cavasino, A.
Bibcode: 1907MmSSI..36....7B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel Triennio 1904-1905
nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36...89B
Altcode:
No abstract at ADS
Title: Variabilità di B. D. + 49°, 499
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36...70B
Altcode:
No abstract at ADS
Title: Saggio di Applicazione dei Metodi di Calcolo dell'Astronomia
Teorica a Problemi di Fisica Matematica. A Proposito della Memoria
del Prof. A. Garbasso sul Miraggio.
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36...79B
Altcode:
No abstract at ADS
Title: Sopra una Nuova Disposizione dei Valore della Precessione e
della Variazione Secolare pei Cataloghi Stellari Disposti in Zone
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36...27B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche Eseguite nel Triennio 1904-1906
nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36..145B
Altcode:
No abstract at ADS
Title: Su Alcune Sospette di Variabilità, Moto Proprio od Altro
Risultanti dalla Reduzione delle Lastre del Catalogo Fotografico
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36..206B
Altcode:
No abstract at ADS
Title: Su Alcune Stelle Sospette di Variabilità, Moto Proprio od
Altro Risultanti dalla Riduzione delle Lastre del Catalogo Fotografico
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36..198B
Altcode:
No abstract at ADS
Title: Osservazioni Fotometriche eseguite nel Triennio 1904-1905
nell'Osservatorio Astrofisico di Catania
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36..183B
Altcode:
No abstract at ADS
Title: Nuove Tavole per la Trasformazione delle Coordinate Equatoriali
(A. R. E. Decl.) in Coordinate Rettilinee della Fotografia Celeste
Authors: Bemporad, A.
Bibcode: 1907MmSSI..36...45B
Altcode:
No abstract at ADS
Title: Notizia riguardante la stella AG. Harvard 1461
Authors: Bemporad, A.
Bibcode: 1906AN....170..299B
Altcode:
No abstract at ADS
Title: Sul Modo di Variare della Radiazione Solare Durante le Fasi
di un' Eclisse
Authors: Bemporad, A.
Bibcode: 1906MmSSI..35...89B
Altcode:
No abstract at ADS
Title: Sul Calcolo degli Spessori Atmosferici per Astri Depressi
Sotto l'Orizzonte con speciale riguardo all'Osservatorio Etneo
Authors: Bemporad, A.
Bibcode: 1906MmSSI..35..175B
Altcode:
No abstract at ADS
Title: N. 4. Relazione sulle Fotografie delle fasi Eseguite
nell'Osservatorio di Catania
Authors: Bemporad, A.; Mazzarella, U.
Bibcode: 1906MmSSI..35...65B
Altcode:
No abstract at ADS
Title: Sopra una Nuova Disposizione dei Valori della Precessione Annua
e della Variazione Secolare pei Cataloghi Stellari Disposti in Zone
Authors: Bemporad, A.
Bibcode: 1906MmSSI..35..203B
Altcode:
No abstract at ADS
Title: N. 3 Relazione Sulle Osservazioni Attinometriche
Authors: Bemporad, A.
Bibcode: 1906MmSSI..35...17B
Altcode:
No abstract at ADS
Title: Bibliografia
Authors: Bemporad, A.
Bibcode: 1906MmSSI..35...85B
Altcode:
Dr. H. Kobold— Der Bau des Fixsternsystems mid besonderer
Berücksichtigung der photometrischen Resultaten
Title: Moto Proprio della stella A. G. Cambr. Mass. 1461
Authors: Bemporad, A.
Bibcode: 1906MmSSI..35....8B
Altcode:
No abstract at ADS
Title: Sulla Riduzione Fotometrica delle Lastre della Fotografia
Stellare
Authors: Bemporad, A.
Bibcode: 1905MmSSI..34...21B
Altcode:
No abstract at ADS
Title: Sulla Teoria della Refrazione Astronomica
Authors: Bemporad, A.
Bibcode: 1905MmSSI..34..233B
Altcode:
No abstract at ADS
Title: Sulla Teoria della Refrazione Astronomica
Authors: Bemporad, A.
Bibcode: 1905MmSSI..34..191B
Altcode:
No abstract at ADS
Title: Sulla Teoria della Refrazione Astronomica
Authors: Bemporad, A.
Bibcode: 1905MmSSI..34..217B
Altcode:
No abstract at ADS
Title: Nuove Tavole per la Trasformazione delle Coordinate Equatoriali
(A. R. E Declin) in Coordinate Equatoriali Rettilinee della Fotografia
Celeste
Authors: Bemporad, A.
Bibcode: 1905MmSSI..34..166B
Altcode:
No abstract at ADS
Title: Tavole Ausiliarie per la Determinazione di Archi Piccoli dal
Log Sin o Log Tang
Authors: Bemporad, A.
Bibcode: 1905MmSSI..34...91B
Altcode:
No abstract at ADS
Title: Saggi di Riduzione Fotometrica delle Lastre del Catalogo
Stellare Fotografico (Zona di Catania)
Authors: Mazzarella, U.; Bemporad, A.
Bibcode: 1905MmSSI..34...53M
Altcode:
No abstract at ADS
Title: Tavole Ausiliarie per Esperienze Sull'Assorbimento Atmosferico
fra l'Osservatorio Astrofisico di Catania e l'Osservatorio Etneo
Authors: Bemporad, A.
Bibcode: 1904MmSSI..33..213B
Altcode:
Appendice: Notizia preliminare circa la diminuzione del potere assobente
dell'atmosfera coll'altezza
Title: La Teoria della Estinzione Atmosferica nella Ipotesi di un
Decrescimento Uniforme della Temperatura dell'Aria coll'Altezza
Authors: Bemporad, A.
Bibcode: 1904MmSSI..33...31B
Altcode:
No abstract at ADS
Title: Sulla Riduzione delle Lastre della Fotografia Stellare
Authors: Bemporad, A.
Bibcode: 1904MmSSI..33..120B
Altcode:
No abstract at ADS
Title: Sulla Teoria della Estinzione Atmosferica
Authors: Bemporad, A.
Bibcode: 1903MmSSI..32...97B
Altcode:
No abstract at ADS
Title: Sulla Teoria della Estinzione Atmosferica
Authors: Bemporad, A.
Bibcode: 1903MmSSI..32...49B
Altcode:
No abstract at ADS
Title: Aufsuchungsephemeride für den Planeten (254) Augusta
Authors: Bemporad, A.
Bibcode: 1902AN....158..127B
Altcode:
No abstract at ADS
Title: Fortsetzung der Ephemeride des Planeten (254) Augusta
Authors: Bemporad, A.
Bibcode: 1902AN....158R.189B
Altcode:
No abstract at ADS
Title: Nuova Riduzione delle Osservazioni Fotometriche eseguite dal
Prof. G. Müller al Säntis
Authors: Bemporad, A.
Bibcode: 1902MmSSI..31..171B
Altcode:
No abstract at ADS
Title: Sopra un Nuovo Sviluppo dell'Integrale della Estinzione
Atmosferica
Authors: Bemporad, A.
Bibcode: 1902MmSSI..31..131B
Altcode:
No abstract at ADS
Title: Una Osservazione alla Teoria di Refrazione di Bessel
Authors: Bemporad, A.
Bibcode: 1902MmSSI..31..278B
Altcode:
No abstract at ADS
Title: Sulla Teoria d'Estinzione di Bouguer
Authors: Bemporad, A.
Bibcode: 1901MmSSI..30..217B
Altcode:
No abstract at ADS
Title: Geschichte des Fixternhimmels (Sitzungsberichte der Berliner
Akad. der Viss). Relazione di A. Auwers.
Authors: Bemporad, A.
Bibcode: 1901MmSSI..30..111B
Altcode:
No abstract at ADS