Author name code: antonucci
ADS astronomy entries on 2022-09-14
author:"Antonucci, Ester"
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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: Five Solar Cycles of Solar Corona Investigations
Authors: Antonucci, Ester
Bibcode: 2022SoPh..297...89A
Altcode:
These are the memoirs of fifty years of research in solar physics,
closely related to the history of three of the major solar space
missions, from the Solar Maximum Mission, SMM, to Solar Orbiter,
at present in navigation toward vantage points closer and closer to
the Sun. My interest in solar physics was stimulated by the studies
on cosmic rays at the University of Turin, and the research in this
field initiated at Stanford University as a postdoctoral fellow in
the team of John Wilcox with studies on the large-scale corona and
its rotation. Thanks to Alan Gabriel, during my first space mission,
SMM, I was involved in the operations and scientific data analysis
of the Soft X-ray Polychromator. Together with Giancarlo Noci and
Giuseppe Tondello, I participated in the realization of the UltraViolet
Coronagraph Spectrometer, NASA/ASI, flown on-board SOHO. After this
experience there was the opportunity to participate in the formulation
of the proposal of the Solar Orbiter mission, and to guide the team,
which for this mission developed the Metis coronagraph, up to the
delivery of the instrument to the European Space Agency in 2017.
Title: Observation of Magnetic Switchback in the Solar Corona
Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco;
Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta,
Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman;
Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia;
Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto;
Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania;
Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero;
Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati,
Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio;
Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère,
Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise;
Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna;
Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo;
Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N.
Bibcode: 2022arXiv220603090T
Altcode:
Switchbacks are sudden, large radial deflections of the solar wind
magnetic field, widely revealed in interplanetary space by the Parker
Solar Probe. The switchbacks' formation mechanism and sources are still
unresolved, although candidate mechanisms include Alfvénic turbulence,
shear-driven Kelvin-Helmholtz instabilities, interchange reconnection,
and geometrical effects related to the Parker spiral. This Letter
presents observations from the Metis coronagraph onboard Solar Orbiter
of a single large propagating S-shaped vortex, interpreted as first
evidence of a switchback in the solar corona. It originated above
an active region with the related loop system bounded by open-field
regions to the East and West. Observations, modeling, and theory provide
strong arguments in favor of the interchange reconnection origin of
switchbacks. Metis measurements suggest that the initiation of the
switchback may also be an indicator of the origin of slow solar wind.
Title: Possible Evidence for Shear-driven Kelvin-Helmholtz Instability
along the Boundary of Fast and Slow Solar Wind in the Corona
Authors: Telloni, Daniele; Adhikari, Laxman; Zank, Gary P.; Zhao,
Lingling; Sorriso-Valvo, Luca; Antonucci, Ester; Giordano, Silvio;
Mancuso, Salvatore
Bibcode: 2022ApJ...929...98T
Altcode:
This paper reports the first possible evidence for the development of
the Kelvin-Helmholtz (KH) instability at the border of coronal holes
separating the associated fast wind from the slower wind originating
from adjacent streamer regions. Based on a statistical data set
of spectroscopic measurements of the UV corona acquired with the
UltraViolet Coronagraph Spectrometer on board the SOlar and Heliospheric
Observatory during the minimum activity of solar cycle 22, high
temperature-velocity correlations are found along the fast/slow solar
wind interface region and interpreted as manifestations of KH vortices
formed by the roll-up of the shear flow, whose dissipation could lead
to higher heating and, because of that, higher velocities. These
observational results are supported by solving coupled solar wind
and turbulence transport equations including a KH-driven source
of turbulence along the tangential velocity discontinuity between
faster and slower coronal flows: numerical analysis indicates that the
correlation between the solar wind speed and temperature is large in
the presence of the shear source of turbulence. These findings suggest
that the KH instability may play an important role both in the plasma
dynamics and in the energy deposition at the boundaries of coronal
holes and equatorial streamers.
Title: Study of two interacting interplanetary coronal mass
ejections encountered by Solar Orbiter during its first perihelion
passage. Observations and modeling
Authors: Telloni, D.; Scolini, C.; Möstl, C.; Zank, G. P.;
Zhao, L. -L.; Weiss, A. J.; Reiss, M. A.; Laker, R.; Perrone, D.;
Khotyaintsev, Y.; Steinvall, K.; Sorriso-Valvo, L.; Horbury, T. S.;
Wimmer-Schweingruber, R. F.; Bruno, R.; D'Amicis, R.; De Marco,
R.; Jagarlamudi, V. K.; Carbone, F.; Marino, R.; Stangalini, M.;
Nakanotani, M.; Adhikari, L.; Liang, H.; Woodham, L. D.; Davies, E. E.;
Hietala, H.; Perri, S.; Gómez-Herrero, R.; Rodríguez-Pacheco, J.;
Antonucci, E.; Romoli, M.; Fineschi, S.; Maksimovic, M.; Souček,
J.; Chust, T.; Kretzschmar, M.; Vecchio, A.; Müller, D.; Zouganelis,
I.; Winslow, R. M.; Giordano, S.; Mancuso, S.; Susino, R.; Ivanovski,
S. L.; Messerotti, M.; O'Brien, H.; Evans, V.; Angelini, V.
Bibcode: 2021A&A...656A...5T
Altcode:
Context. Solar Orbiter, the new-generation mission dedicated to solar
and heliospheric exploration, was successfully launched on February
10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion
passage in June 2020, two successive interplanetary coronal mass
ejections (ICMEs), propagating along the heliospheric current sheet
(HCS), impacted the spacecraft.
Aims: This paper addresses the
investigation of the ICMEs encountered by Solar Orbiter on June 7−8,
2020, from both an observational and a modeling perspective. The aim is
to provide a full description of those events, their mutual interaction,
and their coupling with the ambient solar wind and the HCS.
Methods: Data acquired by the MAG magnetometer, the Energetic Particle
Detector suite, and the Radio and Plasma Waves instrument are used to
provide information on the ICMEs' magnetic topology configuration,
their magnetic connectivity to the Sun, and insights into the
heliospheric plasma environment where they travel, respectively. On
the modeling side, the Heliospheric Upwind eXtrapolation model, the
3D COronal Rope Ejection technique, and the EUropean Heliospheric
FORecasting Information Asset (EUHFORIA) tool are used to complement
Solar Orbiter observations of the ambient solar wind and ICMEs,
and to simulate the evolution and interaction of the ejecta in the
inner heliosphere, respectively.
Results: Both data analysis
and numerical simulations indicate that the passage of two distinct,
dynamically and magnetically interacting (via magnetic reconnection
processes) ICMEs at Solar Orbiter is a possible scenario, supported by
the numerous similarities between EUHFORIA time series at Solar Orbiter
and Solar Orbiter data.
Conclusions: The combination of in situ
measurements and numerical simulations (together with remote sensing
observations of the corona and inner heliosphere) will significantly
lead to a deeper understanding of the physical processes occurring
during the CME-CME interaction. Movies are available at https://www.aanda.org
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: 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: Evolution of Solar Wind Turbulence from 0.1 to 1 au during
the First Parker Solar Probe-Solar Orbiter Radial Alignment
Authors: Telloni, Daniele; Sorriso-Valvo, Luca; Woodham, Lloyd D.;
Panasenco, Olga; Velli, Marco; Carbone, Francesco; Zank, Gary P.;
Bruno, Roberto; Perrone, Denise; Nakanotani, Masaru; Shi, Chen;
D'Amicis, Raffaella; De Marco, Rossana; Jagarlamudi, Vamsee K.;
Steinvall, Konrad; Marino, Raffaele; Adhikari, Laxman; Zhao, Lingling;
Liang, Haoming; Tenerani, Anna; Laker, Ronan; Horbury, Timothy S.;
Bale, Stuart D.; Pulupa, Marc; Malaspina, David M.; MacDowall,
Robert J.; Goetz, Keith; de Wit, Thierry Dudok; Harvey, Peter R.;
Kasper, Justin C.; Korreck, Kelly E.; Larson, Davin; Case, Anthony
W.; Stevens, Michael L.; Whittlesey, Phyllis; Livi, Roberto; Owen,
Christopher J.; Livi, Stefano; Louarn, Philippe; Antonucci, Ester;
Romoli, Marco; O'Brien, Helen; Evans, Vincent; Angelini, Virginia
Bibcode: 2021ApJ...912L..21T
Altcode:
The first radial alignment between Parker Solar Probe and Solar Orbiter
spacecraft is used to investigate the evolution of solar wind turbulence
in the inner heliosphere. Assuming ballistic propagation, two 1.5 hr
intervals are tentatively identified as providing measurements of the
same plasma parcels traveling from 0.1 to 1 au. Using magnetic field
measurements from both spacecraft, the properties of turbulence
in the two intervals are assessed. Magnetic spectral density,
flatness, and high-order moment scaling laws are calculated. The
Hilbert-Huang transform is additionally used to mitigate short sample
and poor stationarity effects. Results show that the plasma evolves
from a highly Alfvénic, less-developed turbulence state near the
Sun, to fully developed and intermittent turbulence at 1 au. These
observations provide strong evidence for the radial evolution of solar
wind turbulence.
Title: The MDOR/PDOR on-line module for MISO, the planning software
of Solar Orbiter instruments
Authors: Volpicelli, Cosimo; Landini, Federico; Pancrazzi, Maurizio;
Straus, Thomas; Susino, Roberto; Nicolini, Gianalfredo; Sasso,
Clementina; Fabi, Michele; De Leo, Yara; Casini, Chiara; Naletto,
Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
Antonucci, Ester; Fineschi, Silvano; Da Deppo, Vania; Zuppella, Paola;
Frassetto, Fabio; Slemer, Alessandra; Mercier, Claude; Kouliche,
Dimitri; Caminade, Stephane; Picard, David; Buchlin, Eric; Auchère,
Frédéric; Romoli, Marco
Bibcode: 2020SPIE11452E..0SV
Altcode:
Solar Orbiter is a solar mission that will approach the Sun down to a
minimum perihelion of 0.28 AU and will increase its orbit inclination
with respect to the ecliptic up to a maximum angle of 34 deg. For
imagers aboard Solar Orbiter there will be three 10-days remote sensing
windows per orbit. Observations shall be carefully planned at least 6
months in advance. The Multi Instrument Sequence Organizer (MISO) is
a web based platform developed by the SPICE group and made available
to support Solar Orbiter instruments teams in planning observations
by assembling Mission Database sequences. Metis is the UV and visible
light coronagraph aboard Solar Orbiter. Metis is a complex instrument
characterized by a rich variety of observing modes, which required a
careful commissioning activity and will need support for potential
maintenance operations throughout the mission. In order to support
commissioning and maintenance activities, the Metis team developed
a PDOR (Payload Direct Operation Request) and MDOR (Memory Direct
Operation Request) module integrated in MISO and made available to all
Solar Orbiter instruments. An effort was made in order to interpret
the coding philosophy of the main project and to make the additional
module as homogeneous as possible both to the web interface and to the
algorithm logic, while integrating characteristics which are peculiar
to PDORs and MDORs. An user friendly web based interface allows the
operator to build the operation request and to successively modify or
integrate it with further or alternative information. In the present
work we describe the PDOR/MDOR module for MISO by addressing its logic
and main characteristics.
Title: Solar Orbiter Investigations of Solar Wind in Corona.
Authors: Antonucci, E.
Bibcode: 2020AGUFMSH031..01A
Altcode:
The study of the dynamics of the solar coronal plasma, continuously
flowing outwards and from time to time suddenly ejected in transient
events, is one of the key objectives of the future space missions
dedicated to heliophysics. In the last decades, the SOHO coronagraphs
obtained the first measurements of the velocity and acceleration of the
solar wind at coronal heights by means of spectroscopic techniques and
by tracking the motion of coronal tracers, such as coronal blobs. The
Solar Orbiter coronagraph, Metis, has been designed to further extend
the investigation of coronal expansion in order to monitor at high
temporal and spatial resolution the dynamic conditions of the full
corona as they evolve on different time-scales and to identify wind
streams with different characteristics. Coronal outflow maps are
derived by combining the simultaneous images of the corona obtained in
the visible and in the resonantly scattered ultraviolet light in order
to measure the Doppler dimming of the UV emission, which is function
of the plasma outward speed. In addition, during the spacecraft out
of ecliptic observations in the late phase of the mission, the Solar
Orbiter instruments will allow us to observe the velocity of the
nascent fast wind at the poles and to assess the longitudinal extent
of wind streams and coronal mass ejections in their propagation through
the corona.
Title: Solar Orbiter: connecting remote sensing and in situ
measurements
Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.;
Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra,
L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.;
Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter,
H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.;
Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis,
Y.; Laker, R.
Bibcode: 2020AGUFMSH038..10H
Altcode:
A key science goal of the Solar Orbiter mission is to make connections
between phenomena on the Sun and their manifestations in interplanetary
space. To that end, the spacecraft carries a carefully tailored
payload of six remote sensing instruments and four making in situ
measurements. During June 2020, while the spacecraft was around 0.5
AU from the Sun, the remote sensing instruments operated for several
days. While this was primarily an engineering activity, the resulting
observations provided outstanding measurements and represent the ideal
first opportunity to investigate the potential for making connections
between the remote sensing and in situ payloads on Solar Orbiter. We present a preliminary analysis of the available remote sensing and
in situ observations, showing how connections can be made, and discuss
the potential for further, more precise mapping to be performed as
the mission progresses.
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: Observations of the Solar Corona from Space
Authors: Antonucci, Ester; Harra, Louise; Susino, Roberto; Telloni,
Daniele
Bibcode: 2020SSRv..216..117A
Altcode:
Space observations of the atmosphere of the Sun, obtained in half a
century of dedicated space missions, provide a well established picture
of the medium and large-scale solar corona, which is highly variable
with the level of solar activity through a solar cycle and evolves
with the long-term evolution of the magnetic cycles. In this review,
we summarize the physical properties and dynamics of the medium and
large-scale corona, consisting primarily of active regions, streamers
and coronal holes; describe the dependence of coronal patterns on
the magnetic field patterns changing through the solar cycle and the
properties of the regions of open magnetic flux channeling the solar
wind; the ubiquitous presence of fluctuations in the outer corona; the
rotational properties of the large-scale corona; and the persistent
hemispheric asymmetries in the emergence of magnetic fields and the
distribution of the coronal emission.
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: The Solar Orbiter mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
Bibcode: 2020A&A...642A...1M
Altcode: 2020arXiv200900861M
Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
2015-2025 programme and a mission of international collaboration between
ESA and NASA, will explore the Sun and heliosphere from close up and
out of the ecliptic plane. It was launched on 10 February 2020 04:03
UTC from Cape Canaveral and aims to address key questions of solar and
heliospheric physics pertaining to how the Sun creates and controls
the Heliosphere, and why solar activity changes with time. To answer
these, the mission carries six remote-sensing instruments to observe
the Sun and the solar corona, and four in-situ instruments to measure
the solar wind, energetic particles, and electromagnetic fields. In
this paper, we describe the science objectives of the mission, and how
these will be addressed by the joint observations of the instruments
onboard.
Methods: The paper first summarises the mission-level
science objectives, followed by an overview of the spacecraft and
payload. We report the observables and performance figures of each
instrument, as well as the trajectory design. This is followed by a
summary of the science operations concept. The paper concludes with a
more detailed description of the science objectives.
Results:
Solar Orbiter will combine in-situ measurements in the heliosphere
with high-resolution remote-sensing observations of the Sun to address
fundamental questions of solar and heliospheric physics. The performance
of the Solar Orbiter payload meets the requirements derived from the
mission's science objectives. Its science return will be augmented
further by coordinated observations with other space missions and
ground-based observatories. ARRAY(0x207ce98)
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: Study of the Influence of the Solar Wind Energy on the
Geomagnetic Activity for Space Weather Science
Authors: Telloni, Daniele; Carbone, Francesco; Antonucci, Ester;
Bruno, Roberto; Grimani, Catia; Villante, Umberto; Giordano, Silvio;
Mancuso, Salvatore; Zangrilli, Luca
Bibcode: 2020ApJ...896..149T
Altcode:
This paper addresses the investigation of the interaction of the
solar wind energy with the Earth's magnetosphere, by studying its
correlation with the disturbance storm time (Dst) index, a proxy of
the geomagnetic activity. Some relevant parameters of the solar wind
(the bulk speed and the z-component of the interplanetary magnetic
field) are explored in the energy-Dst space. It results that (I) the
solar wind energy and the geomagnetic activity are strictly related,
with the coronal mass ejections representing the most energetic and
geoeffective driver; (II) the slow solar wind has negligible effects on
Earth regardless of its energy content, whereas high-speed streams may
induce severe geomagnetic storming depending on the advected energy;
and (III) while at low and mid energies, geomagnetic disturbances are
induced provided the magnetic reconnection between the interplanetary
and terrestrial magnetic fields occurs, high-energy solar wind plasma
can impact Earth even without reconnecting with the geomagnetic field at
the dayside magnetopause. The most significant result in the framework
of space weather science resides in the observational evidence that the
Earth's magnetosphere has a maximum response to the energetic content
of the solar wind, which leads to the derivation of an empirical law
allowing the proper forecast of the upper limit of the intensity of
any geomagnetic disturbance on the basis of the solar wind energy
derived in situ at the Lagrangian point L1.
Title: Optical design of the multi-wavelength imaging coronagraph
Metis for the solar orbiter mission
Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.;
Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro,
D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.;
Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.;
Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle,
U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki,
A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero,
A.; Castronuovo, M.
Bibcode: 2020ExA....49..239F
Altcode: 2020ExA...tmp...14F
This paper describes the innovative optical design of the Metis
coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a
multi-wavelength, externally occulted telescope for the imaging
of the solar corona in both the visible and ultraviolet wavelength
ranges. Metis adopts a novel occultation scheme for the solar disk,
that we named "inverse external occulter", for reducing the extremely
high thermal load on the instrument at the spacecraft perihelion. The
core of the Metis optical design is an aplanatic Gregorian telescope
common to both the visible and ultraviolet channels. A suitable
dichroic beam-splitter, optimized for transmitting a narrow-band in
the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband
in the visible (580-640 nm) spectral range, is used to separate the
two optical paths. Along the visible light optical path, a liquid
crystal electro-optical modulator, used for the first time in space,
allows making polarimetric measurements.
Title: Global helium abundance measurements in the solar corona
Authors: Moses, John D.; Antonucci, Ester; Newmark, Jeffrey; Auchère,
Frédéric; Fineschi, Silvano; Romoli, Marco; Telloni, Daniele;
Massone, Giuseppe; Zangrilli, Luca; Focardi, Mauro; Landini, Federico;
Pancrazzi, Maurizio; Rossi, Guglielmo; Malvezzi, Andrea M.; Wang,
Dennis; Leclec'h, Jean-Christophe; Moalic, Jean-Pierre; Rouesnel,
Frédéric; Abbo, Lucia; Canou, Aurélien; Barbey, Nicolas; Guennou,
Chloé; Laming, John M.; Lemen, James; Wuelser, Jean-Pierre; Kohl,
John L.; Gardner, Lawrence D.
Bibcode: 2020NatAs...4.1134M
Altcode: 2020NatAs.tmp..152M
Solar abundances have been historically assumed to be representative
of cosmic abundances. However, our knowledge of the solar abundance
of helium, the second most abundant element, relies mainly on
models1 and indirect measurements through helioseismic
observations2, because actual measurements of helium in the
solar atmosphere are very scarce. Helium cannot be directly measured
in the photosphere because of its high first ionization potential,
and measurements of its abundance in the inner corona have been
sporadic3,4. In this Letter, we present simultaneous global
images of the helium (out to a heliocentric distance of 3R⊙
(solar radii)) and hydrogen emission in the solar corona during
the minimum of solar activity of cycle 23 and directly derive the
helium abundance in the streamer region and surrounding corona
(out to 2.2R⊙). The morphology of the He+
corona is markedly different from that of the H corona, owing to
significant spatial variations in helium abundance. The observations
show that the helium abundance is shaped according to and modulated
by the structure of the large-scale coronal magnetic field and that
helium is almost completely depleted in the equatorial regions during
the quiet Sun. This measurement provides a trace back to the coronal
source of the anomalously slow solar wind observed in the heliosphere
at the Sun-Earth Lagrangian point L1 in 2009, during the exceptionally
long-lasting minimum of solar activity cycle 23.
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: On the Fast Solar Wind Heating and Acceleration Processes:
A Statistical Study Based on the UVCS Survey Data
Authors: Telloni, Daniele; Giordano, Silvio; Antonucci, Ester
Bibcode: 2019ApJ...881L..36T
Altcode:
The UltraViolet Coronagraph Spectrometer (UVCS) on board the SOlar and
Heliospheric Observatory has almost continuously observed, throughout
the whole solar cycle 23, the UV solar corona. This work addresses
the first-ever statistical analysis of the daily UVCS observations,
performed in the O VI channel, of the northern polar coronal hole,
between 1.5 and 3 R ⊙, during the period of low solar
activity from 1996 April to 1997 December. The study is based on the
investigation, at different heights, of the correlation between the
variance of the O VI 1031.92 Å spectral line and the O VI 1031.92,
1037.61 Å doublet intensity ratio, which are proxies of the kinetic
temperature of the O5+ ions and of the speed of the oxygen
component of the fast solar wind, respectively. This analysis allows
the clear identification of the sonic point in polar coronal holes
at the distance of 1.9 R ⊙. The results show that heat
addition below the sonic point does not lead to an increase of the
outflow speed. As a matter of fact, the coronal plasma is heated more
efficiently in the subsonic region, while its acceleration occurs
more effectively in the region of supersonic flow. So, within the
panorama of the Parker Solar Probe and Solar Orbiter missions, the
statistical analysis of the historical UVCS data appears to be very
promising in providing unique clues to some still unsolved problems,
as the coronal heating, in the solar corona.
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: OPSys: optical payload systems facility for space
instrumentation integration and calibration
Authors: Capobianco, Gerardo; Fineschi, Silvano; Massone, Giuseppe;
Landini, Federico; Casti, Marta; Bellomo, Alessandro; Deffacis,
Maurizio; Romoli, Marco; Antonucci, Ester; Andretta, Vincenzo; Naletto,
Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele
Bibcode: 2019SPIE11180E..7MC
Altcode:
The Optical Payload System (OPSys) is an INAF (italian National
Institute for Astrophysics) facility hosted by Aerospace Logistics
Technology Engineering Company (ALTEC SpA) in Turin, Italy. The facility
is composed by three clean rooms having different cleanliness levels,
a thermo-vacuum chamber (SPOCC, Space Optics calibration Chamber)
with a motorized optical bench and several light sources covering the
range from the extreme ultraviolet to the red light wavelengths. The
SPOCC has been designed having in mind the very stringent requirements
of the calibration of solar coronagraphs and the suppression of
the stray-light. The facility and the optical performances will be
described here. The calibration campaign performed on Metis space
coronagraph will be reported as a case study.
Title: Optical performance of the Metis coronagraph on the Solar
Orbiter ESA mission
Authors: Frassetto, Fabio; Da Deppo, Vania; Zuppella, Paola; Romoli,
Marco; Fineschi, Silvano; Antonucci, Ester; Nicolini, Giana; Naletto,
Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
Castronuovo, Marco; Casti, Marta; Capobianco, Gerardo; Massone,
Giuseppe; Susino, Roberto; Landini, Federico; Pancrazzi, Maurizio;
Teriaca, Luca; Schühle, Udo; Heerlein, Klaus; Uslenghi, Michela
Bibcode: 2019SPIE11180E..6YF
Altcode:
The Metis coronagraph aboard the Solar Orbiter ESA spacecraft is
expected to provide new insights into the solar dynamics. In detail,
it is designed to address three main questions: the energy deposition
mechanism at the poles (where the fast wind is originated), the
source of the slow wind at lower altitude, and how the global corona
evolves, in particular in relation to the huge plasma ejections that
occasionally are produced. To obtain the required optical performance,
not only the Metis optical design has been highly optimized, but the
alignment procedure has also been subjected to an accurate evaluation
in order to fulfill the integration specifications. The telescope
assembling sequence has been constructed considering all the subsystems
manufacturing, alignment and integration tolerances. The performance
verification activity is an important milestone in the instrument
characterization and the obtained results will assure the fulfillment
of the science requirements for its operation in space. The entire
alignment and verification phase has been performed by the Metis team in
collaboration with Thales Alenia Space Torino and took place in ALTEC
(Turin) at the Optical Payload System Facility using the Space Optics
Calibration Chamber infrastructure, a vacuum chamber especially built
and tested for the alignment and calibration of the Metis coronagraph,
and suitable for tests of future payloads. The goal of the alignment,
integration, verification and calibration processes is to measure
the parameters of the telescope, and the characteristics of the two
Metis channels: visible and ultraviolet. They work in parallel thanks
to the peculiar optical layout. The focusing and alignment performance
of the two channels must be well understood, and the results need to be
easily compared to the requirements. For this, a dedicated illumination
method, with both channels fed by the same source, has been developed;
and a procedure to perform a simultaneous through focus analysis has
been adopted. In this paper the final optical performance achieved by
Metis is reported and commented.
Title: Alignment procedure for the Gregorian telescope of the Metis
coronagraph for the Solar Orbiter ESA mission
Authors: Da Deppo, Vania; Mottini, Sergio; Naletto, Giampiero;
Frassetto, Fabio; Zuppella, Paola; Sertsu, Mewael G.; Romoli, Marco;
Fineschi, Silvano; Antonucci, Ester; Nicolini, Gianalfredo; Nicolosi,
Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Castronuovo, Marco;
Casti, Marta; Capobianco, Gerardo; Massone, Giuseppe; Susino, Roberto;
Landini, Federico; Pancrazzi, Maurizio; Casini, Chiara; Teriaca,
Luca; Uslenghi, Michela
Bibcode: 2019SPIE11180E..76D
Altcode:
Metis is a solar coronagraph mounted on-board the Solar Orbiter ESA
spacecraft. Solar Orbiter is scheduled for launch in February 2020
and it is dedicated to study the solar and heliospheric physics from a
privileged close and inclined orbit around the Sun. Perihelion passages
with a minimum distance of 0.28 AU are foreseen. Metis features two
channels to image the solar corona in two different spectral bands:
in the HI Lyman at 121.6 nm, and in the polarized visible light band
(580 - 640 nm). Metis is a solar coronagraph adopting an "inverted
occulted" configuration. The inverted external occulter (IEO) is a
circular aperture followed by a spherical mirror which back rejects
the disk light. The reflected disk light exits the instrument through
the IEO aperture itself, while the passing coronal light is collected
by the Metis telescope. Common to both channels, the Gregorian on-axis
telescope is centrally occulted and both the primary and the secondary
mirror have annular shape. Classic alignment methods adopted for on-axis
telescope cannot be used, since the on-axis field is not available. A
novel and ad hoc alignment set-up has been developed for the telescope
alignment. An auxiliary visible optical ground support equipment source
has been conceived for the telescope alignment. It is made up by four
collimated beams inclined and dimensioned to illuminate different
sections of the annular primary mirror without being vignetted by
other optical or mechanical elements of the instrument.
Title: Metis/Solar Orbiter polarimetric visible light channel
calibration
Authors: Casti, M.; Fineschi, S.; Capobianco, G.; Romoli, M.;
Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D.;
Andretta, V.; Castronuovo, M.; Massone, G.; Susino, R.; Da Deppo, V.;
Frassetto, F.; Landini, F.; Pancrazzi, M.; Teriaca, L.; Uslenghi, M.
Bibcode: 2019SPIE11180E..3CC
Altcode:
Metis is the solar coronagraph of the ESA mission Solar Orbiter. For
the first time, Metis will acquire simultaneous images of the solar
corona in linearly polarized, broadband visible light (580-640 nm) and
in the narrow-band HI Ly-α line (121.6 nm). The visible light path
includes a polarimeter, designed to observe and analyse the K-corona
linearly polarized by Thomson scattering. The polarimeter comprises a
liquid crystal Polarization Modulation Package (PMP) together with a
quarter-wave retarder and a linear polarizer. The Metis PMP consists of
two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with
their fast axis parallel with respect to each other and a pre-tilted
angle of the molecules in opposite direction. This configuration results
in an instrumental wide field of view (+/-7°). The LCVRs provide an
electro-optical modulation of the input polarized light by applying an
electric field to the liquid crystal molecules inside the cells. A given
optical retardance can be induced in the LCVRs by selecting a suitable
voltage value. This paper reports the polarimetric characterization of
the Visible-light channel for the Metis/Solar Orbiter coronagraph. The
retardance-to-voltage calibration of the electro-optical polarimeter was
characterized over the entire field of view of the coronagraph yielding
a complete "polarimetric flat-field" of the Metis Visible-light channel.
Title: Stray light calibration for the Solar Orbiter/Metis solar
coronagraph
Authors: Landini, F.; Romoli, M.; Fineschi, S.; Casini, C.; Baccani,
C.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro,
D.; Andretta, V.; Castronuovo, M.; Casti, M.; Capobianco, G.; Massone,
G.; Susino, R.; Da Deppo, V.; Frassetto, F.; Pancrazzi, M.; Teriaca,
L.; Schuehle, U.; Heerlein, K.; Uslenghi, M.
Bibcode: 2019SPIE11180E..2IL
Altcode:
The Solar Orbiter/Metis visible and UV solar coronagraph redefines
the concept of external occultation in solar coronagraphy. Classical
externally occulted coronagraphs are characterized by an occulter in
front of the telescope entrance aperture. Solar Orbiter will approach
the Sun down to 0.28 AU: in order to reduce the thermal load, the
Metis design switches the positions of the entrance aperture and the
external occulter thus achieving what is called the inverted external
occultation. The inverted external occulter (IEO) consists of a circular
aperture on the Solar Orbiter thermal shield that acts as coronagraph
entrance pupil. A spherical mirror, located 800 mm behind the IEO, back
rejects the disklight through the IEO itself. To pursue the goal of
maximizing the reduction of the stray light level on the focal plane,
an optimization of the IEO shape was implemented. The stray light
calibration was performed in a clean environment in front of the OPSys
solar disk divergence simulator (at ALTEC, in Torino, Italy), which is
able to emulate different heliocentric distances. Ground calibrations
were a unique opportunity to map the Metis stray light level thanks to
a pure solar disk simulator without the solar corona. The stray light
calibration was limited to the visible light case, being the most
stringent. This work is focused on the description of the laboratory
facility that was used to perform the stray light calibration and on
the calibration results.
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: 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: Wide field of view liquid crystals-based modulator for the
polarimeter of the Metis/Solar Orbiter
Authors: Capobianco, Gerardo; Casti, Marta; Fineschi, Silvano;
Massone, Giuseppe; Sertsu, Mewael G.; Landini, Federico; Romoli,
Marco; Antonucci, Ester; Andretta, Vincenzo; Naletto, Giampiero;
Nicolini, Gianalfredo; Spadaro, Daniele; Alvarez Herrero, Alberto;
Garcia Parejo, Pilar; Marmonti, Matteo
Bibcode: 2018SPIE10698E..30C
Altcode:
Metis is an inverted occulted coronagraph on-board the ESA/Solar
Orbiter mission. The visible light path of the instrument will observe
the "white" light (580-640 nm) linearly-polarized emission from the
solar corona. The coronal polarized brightness allows retrieval of
physical parameters such as the electron density and temperature of
the K-corona. The Metis polarimeter comprises a quarter-wave retarder,
the liquid crystal polarization modulation package (PMP) and a linear
polarizer working as polarization analyser. The PMP consists of two
Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with
the fast axes parallels one to each other and a pre-tilted angle of the
molecules in opposite direction, in order to maximize the homogeneity of
the retardance across instrumental wide field of view: +/-7 deg. This
presentation reports the characterization of the PMP breadboard
(BB), fully representative of the optical/polarimetric performances
of the flight model. This characterization consisted in determining
the performances of the device in terms of retardance as function of
the applied voltage at different temperatures, angle of incidence and
the variation of the retardance as a function of the wavelength. The
calibrations were performed by measuring the complete Mueller matrix
of the PMP-BB. The experimental results have been compared with the
parameters of the theoretical model (e.g., depolarization, effective
retardance, cells misalignment).
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: Calibration of the liquid crystal visible-light polarimeter
for the Metis/Solar Orbiter coronagraph
Authors: Casti, M.; Fineschi, S.; Capobianco, G.; Landini, F.; Romoli,
M.; Antonucci, E.; Andretta, V.; Naletto, G.; Nicolini, G.; Spadaro,
D.; Alvarez-Herrero, A.; Garcia-Parejo, P.; Marmonti, M.
Bibcode: 2018SPIE10698E..31C
Altcode:
Metis is the solar coronagraph selected for the payload of the ESA
Solar Orbiter mission. Metis will acquire simultaneous imaging in
linearly polarized, broadband visible light (580-640 nm) and in the
narrow-band HI Ly-α line (121.6 nm). The METIS visible light path
includes a polarimeter, designed to observe and analyse the K-corona
linearly polarized by Thomson scattering. The polarimeter comprises a
liquid crystal Polarization Modulation Package (PMP) together with a
quarter-wave retarder and a linear polarizer. The Metis PMP consists of
two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with
their fast axis parallel with respect to each other and a pre-tilted
angle of the molecules in opposite direction. The LCVRs provide an
electro-optical modulation of the input polarized light by applying
an electric field to the liquid crystal molecules inside the cells. A
given optical retardance can be induced in the LCVRs by selecting a
suitable voltage value. This presentation will report the polarimetric
characterization of the Flight Model of the Metis polarimeter and the
voltage-to-retardance calibration.
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: The optimization of the inverted occulter of the solar
orbiter/METIS coronagraph/spectrometer
Authors: Landini, F.; Vives, S.; Romoli, M.; Guillon, C.; Pancrazzi,
M.; Escolle, C.; Focardi, M.; Fineschi, S.; Antonucci, E.; Nicolini,
G.; Naletto, G.; Nicolosi, P.; Spadaro, D.
Bibcode: 2017SPIE10564E..0FL
Altcode:
The coronagraph/spectrometer METIS (Multi Element Telescope for Imaging
and Spectroscopy), selected to fly aboard the Solar Orbiter ESA/NASA
mission, is conceived to perform imaging (in visible, UV and EUV)
and spectroscopy (in EUV) of the solar corona. It is an integrated
instrument suite located on a single optical bench and sharing a
unique aperture on the satellite heat shield. As every coronagraph,
METIS is highly demanding in terms of stray light suppression. In
order to meet the strict thermal requirements of Solar Orbiter, METIS
optical design has been optimized by moving the entrance pupil at the
level of the external occulter on the S/C thermal shield, thus reducing
the size of the external aperture. The scheme is based on an inverted
external-occulter (IEO). The IEO consists of a circular aperture on
the Solar Orbiter thermal shield. A spherical mirror rejects back the
disk-light through the IEO. The experience built on all the previous
space coronagraphs forces designers to dedicate a particular attention
to the occulter optimization. Two breadboards were manufactured to
perform occulter optimization measurements: BOA (Breadboard of the
Occulting Assembly) and ANACONDA (AN Alternative COnfiguration for the
Occulting Native Design Assembly). A preliminary measurement campaign
has been carried on at the Laboratoire d'Astrophysique de Marseille. In
this paper we describe BOA and ANACONDA designs, the laboratory set-up
and the preliminary results.
Title: Preliminary error budget analysis of the coronagraphic
instrument metis for the solar orbiter ESA mission
Authors: Da Deppo, Vania; Poletto, Luca; Crescenzio, Giuseppe;
Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero
Bibcode: 2017SPIE10564E..3BD
Altcode:
METIS, the Multi Element Telescope for Imaging and Spectroscopy, is
the solar coronagraph foreseen for the ESA Solar Orbiter mission. METIS
is conceived to image the solar corona from a near-Sun orbit in three
different spectral bands: in the HeII EUV narrow band at 30.4 nm, in
the HI UV narrow band at 121.6 nm, and in the polarized visible light
band (590 - 650 nm). It also incorporates the capability of multi-slit
spectroscopy of the corona in the UV/EUV range at different heliocentric
heights. METIS is an externally occulted coronagraph which adopts an
"inverted occulted" configuration. The Inverted external occulter
(IEO) is a small circular aperture at the METIS entrance; the Sun-disk
light is rejected by a spherical mirror M0 through the same aperture,
while the coronal light is collected by two annular mirrors M1-M2
realizing a Gregorian telescope. To allocate the spectroscopic part,
one portion of the M2 is covered by a grating (i.e. approximately 1/8
of the solar corona will not be imaged). This paper presents the error
budget analysis for this new concept coronagraph configuration, which
incorporates 3 different sub-channels: UV and EUV imaging sub-channel,
in which the UV and EUV light paths have in common the detector and
all of the optical elements but a filter, the polarimetric visible
light sub-channel which, after the telescope optics, has a dedicated
relay optics and a polarizing unit, and the spectroscopic sub-channel,
which shares the filters and the detector with the UV-EUV imaging one,
but includes a grating instead of the secondary mirror. The tolerance
analysis of such an instrument is quite complex: in fact not only
the optical performance for the 3 sub-channels has to be maintained
simultaneously, but also the positions of M0 and of the occulters
(IEO, internal occulter and Lyot stop), which guarantee the optimal
disk light suppression, have to be taken into account as tolerancing
parameters. In the aim of assuring the scientific requirements are
optimally fulfilled for all the sub-channels, the preliminary results
of manufacturing, alignment and stability tolerance analysis for the
whole instrument will be described and discussed.
Title: Evaluation of the stray light from the diffraction of METIS
coronagraph external occulter
Authors: Romoli, M.; Landini, F.; Moses, D.; Fineschi, S.; Pancrazzi,
M.; Focardi, M.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi,
P.; Spadaro, D.
Bibcode: 2017SPIE10564E..37R
Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy) is an
externally occulted coronagraph part of the Solar Orbiter payload. METIS
innovative occulting system, called inverted externally occulter (IEO),
consists of a circular aperture, IEO, that acts also as the entrance
pupil of the instrument, and a solar disk rejection mirror (M0),
placed at the bottom end of the coronagraph boom. M0 reflects back
through IEO the solar disk radiation, letting the coronal radiation
enter the coronagraph telescope. Light diffracted by IEO enters the
telescope and has to be minimized with a proper shape of the IEO
edge. The paper describes the theoretical results of the diffraction
analysis extended to the scattered light by the primary mirror of the
telescope onto the primary focal plane. A summary of the entire stray
light reduction capabilities of METIS is also given.
Title: Internal checkup illumination sources for METIS coronagraph
on solar orbiter
Authors: Frassetto, F.; Poletto, L.; Fineschi, S.; De Santi, C.;
Meneghini, M.; Meneghesso, G.; Antonucci, E.; Naletto, G.; Romoli,
M.; Spadaro, D.; Nicolini, G.
Bibcode: 2017SPIE10563E..5JF
Altcode:
METIS is one of the remote sensing instrument on the Solar Orbiter
mission. It will acquire coronal images from distances from the Sun
as close as 0.28 AU. The mission innovations rely not only in the
spacecraft orbit; METIS introduces many technical breakthroughs in the
optical layout and in many other areas, mainly the inverted external
occulter and the visible light (VL) polarimeter.
Title: METIS, the Multi Element Telescope for Imaging and
Spectroscopy: an instrument proposed for the solar orbiter mission
Authors: Antonucci, E.; Andretta, V.; Cesare, S.; Ciaravella, A.;
Doschek, G.; Fineschi, S.; Giordano, S.; Lamy, P.; Moses, D.; Naletto,
G.; Newmark, J.; Poletto, L.; Romoli, M.; Solanki, S.; Spadaro, D.;
Teriaca, L.; Zangrilli, L.
Bibcode: 2017SPIE10566E..0LA
Altcode:
METIS, the Multi Element Telescope for Imaging and Spectroscopy,
is an instrument proposed to the European Space Agency to be part of
the payload of the Solar Orbiter mission. The instrument design has
been conceived for performing extreme ultraviolet (EUV) spectroscopy
both on the solar disk and off-limb, and near-Sun coronagraphy
and spectroscopy. The proposed instrument suite consists of three
different interconnected elements, COR, EUS and SOCS, sharing the
same optical bench, electronics, and S/C heat shield aperture. COR is
a visible-EUV multiband coronagraph based on a classical externally
occulted design. EUS is the component of the METIS EUV disk spectrometer
which includes the telescope and all the related mechanisms. Finally,
SOCS is the METIS spectroscopic component including the dispersive
system and the detectors. The capability of inserting a small telescope
collecting coronal light has been added to perform also EUV coronal
spectroscopy. METIS can simultaneously image the visible and ultraviolet
emission of the solar corona and diagnose, with unprecedented temporal
coverage and space resolution the structure and dynamics of the full
corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙,
measured from Sun centre) at minimum (maximum) perihelion during the
nominal mission. It can also perform spectroscopic observations of the
solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region,
and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125
nm spectral band.
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: METIS-ESA solar orbiter mission internal straylight analysis
Authors: Verroi, E.; Da Deppo, V.; Naletto, G.; Fineschi, S.;
Antonucci, E.
Bibcode: 2017SPIE10563E..1NV
Altcode:
METIS is the Multi Element Telescope for Imaging and Spectroscopy
for the ESA Solar Orbiter. Its target is the solar corona from a
near-Sun orbit in two different spectral bands: the HI UV narrow
band at 121.6 nm, and the VL visible light band. METIS adopts a novel
inverted externally occulted configuration, where the disk light is
shielded by an annular occulter, and an annular aspherical mirror M1
collects the signal coming from the corona. After M1 the coronal light
passes through an internal occulter and is then reflected by a second
annular mirror M2 toward a narrow filter for the 121.6 nm HI line
selection. The visible light reflected by the filter is used to feed
a visible light (580 - 640 nm) polarimetric channel. The photospheric
light passing through the entrance aperture is back-rejected by a
spherical rejection mirror. Since the coronal light is enormously
fainter than the photospheric one, a very tough suppression is needed
for the internal stray light, in particular the requirement for the
stray light suppression is more stringent in the VL than in the UV,
because the emission of the corona with respect to the disk emission
is different in the two cases, and the requirements are a suppression
of at least 10-9 times for the VL and a suppression of at
least 10-7 times for the UV channel. This paper presents the
stray light analysis for this new coronographic configuration. The
complexity of the optomechanical design of METIS, combined with
the faintness of the coronal light with respect to the solar disk
noise, make a standard ray tracing approach not feasible because it
is not sufficient to stop at the first generation of scattered rays
in order to check the requirements. Also scattered rays down to the
fourth generation must be treated as sources of new scattering light,
to analyze the required level of accuracy. If used in a standard ray
tracing scattering analysis, this approach is absolutely beyond the
computational capabilities today available; therefore we opted for a
scattering ray generation with a Montecarlo method in which after a
father ray hits a surface, only one ray is generated, randomly selected
according to the distribution of the transmitted energy. These rays
bring with them all the energy that is otherwise distributed between
all the rays of second generation, making the model more realistic and
avoiding loss of energy due to the rays sampling. The stray light has
been studied in function of the mechanical roughness of the surfaces
and the obtained results indicate an instrument stray light blocking
performance well within the requirements in both channels.
Title: Optical measurements of the mirrors and of the interferential
filter of the Metis coronagraph on Solar Orbiter
Authors: Sandri, P.; Sarra, P.; Radaelli, P.; Morea, D.; Melich,
R.; Berlicki, A.; Antonucci, E.; Castronuovo, M. M.; Fineschi, S.;
Naletto, G.; Nicolini, G.; Romoli, M.
Bibcode: 2017SPIE10397E..16S
Altcode:
The paper describes the wavefront error measurements of the concave
ellipsoidal mirrors M1 and M2, of the concave spherical mirror M0 and
of the flat interferential filter IF of the Metis coronagraph. Metis is
an inverted occultation coronagraph on board of the ESA Solar Orbiter
mission providing a broad-band imaging of the full corona in linearly
polarized visible-light (580 - 640 nm) and a narrow-band imaging of
the full corona in the ultraviolet Lyman α (121.6 nm). Metis will
observe the solar outer atmosphere from a close distance to the Sun
as 0.28 A.U. and from up to 35deg out-of-ecliptic. The measurements of
wavefront error of the mirrors and of the interferential filter of Metis
have been performed in a ISO5 clean room both at component level and at
assembly level minimizing, during the integration, the stress introduced
by the mechanical hardware. The wavefront error measurements have been
performed with a digital interferometer for mirrors M0, M1 and M2 and
with a Shack-Hartmann wavefront sensor for the interferential filter.
Title: Investigating the behaviour of neutral hydrogen Lyα spectral
line width in polar coronal holes at solar minimum
Authors: Spadaro, D.; Susino, R.; Dolei, S.; Ventura, R.; Antonucci, E.
Bibcode: 2017A&A...603A..35S
Altcode:
We investigate the behaviour of the H I Lyα spectral line widths
measured by UVCS/SOHO in polar coronal holes at minimum of solar
magnetic activity. The line widths are reported to significantly
increase up to 3 R⊙, while above 3 R⊙
there is observational evidence of either nearly constant or slightly
decreasing values. We adopt empirical models of polar coronal holes at
solar activity minimum reported in the literature and calculate the
characteristic timescales relevant to different processes coupling
neutral hydrogen atoms and protons, which are heated and accelerated
in the outflowing plasma. This analysis leads us to believe that
the progressive decoupling of the two sets of particles below 10
R⊙, caused by the decrease of the plasma density due
to the rapid expansion of the wind, cannot explain the behaviour
of the Lyα line profile observed in polar coronal holes. We also
synthesise the intensity and profile of the Lyα line as a function
of heliocentric distance from the coronal hole models, adopting H
I densities computed in non-equilibrium ionisation with the aim of
satisfactorily reproducing the UVCS Lyα observations reported in the
literature. Our analysis shows that the coronal Lyα emission decreases
with heliocentric distance, down to values below the interplanetary
Lyα emission, owing to the decrease of the plasma density and to
non-equilibrium ionisation effects in the expanding plasma. This
can lead to the predominance of the interplanetary emission, which
is characterised by H I velocity distributions corresponding to
temperatures about one order of magnitude lower than the coronal
temperatures, and to the narrowing of the resulting coronal profile
at higher heliocentric distances. This scenario can be a plausible
explanation for the behaviour of the Lyα line profile with height
observed in polar coronal holes at solar activity minimum.
Title: SOLARIS: Solar Sail Investigation of the Sun
Authors: Appourchaux, Thierry; Auchère, Frédéric; Antonucci, Ester;
Gizon, Laurent; MacDonald, Malcolm; Hara, Hirohisa; Sekii, Takashi;
Moses, Daniel; Vourlidas, Angelos
Bibcode: 2017arXiv170708193A
Altcode:
In this paper, we detail the scientific objectives and outline
a strawman payload of the SOLAR sail Investigation of the Sun
(SOLARIS). The science objectives are to study the 3D structure
of the solar magnetic and velocity field, the variation of total
solar irradiance with latitude, and the structure of the corona. We
show how we can meet these science objective using solar-sail
technologies currently under development. We provide a tentative
mission profile considering several trade-off approaches. We also
provide a tentative mass budget breakdown and a perspective for a
programmatic implementation.
Title: A virtual appliance as proxy pipeline for the Solar
Orbiter/Metis coronagraph
Authors: Pancrazzi, M.; Straus, T.; Andretta, V.; Spadaro, D.; Haugan,
S. V.; de Groof, A.; Carr, R.; Focardi, M.; Nicolini, G.; Landini,
F.; Baccani, C.; Romoli, M.; Antonucci, E.
Bibcode: 2016SPIE.9913E..4LP
Altcode:
Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted
to the study of the Sun that will be launched in October 2018. Metis is
designed to perform imaging of the solar corona in the UV at 121.6 nm
and in the visible range where it will accomplish polarimetry studies
thanks to a variable retarder plate. Due to mission constraints, the
telemetry downlink on the spacecraft will be limited and data will be
downloaded with delays that could reach, in the worst case, several
months. In order to have a quick overview on the ongoing operations
and to check the safety of the 10 instruments on board, a high-priority
downlink channel has been foreseen to download a restricted amount of
data. These so-called Low Latency Data will be downloaded daily and,
since they could trigger possible actions, they have to be quickly
processed on ground as soon as they are delivered. To do so, a proper
processing pipeline has to be developed by each instrument. This
tool will then be integrated in a single system at the ESA Science
Operation Center that will receive the downloaded data by the Mission
Operation Center. This paper will provide a brief overview of the on
board processing and data produced by Metis and it will describe the
proxy-pipeline currently under development to deal with the Metis
low-latency data.
Title: Stray-light analyses of the METIS coronagraph on Solar Orbiter
Authors: Fineschi, S.; Sandri, P.; Landini, F.; Romoli, M.; DaDeppo,
V.; Frassetto, F.; Verroi, E.; Naletto, G.; Morea, D.; Antonucci,
E.; Spadaro, D.; Andretta, V.
Bibcode: 2015SPIE.9604E..0KF
Altcode:
The METIS coronagraph on board the Solar Orbiter mission will have the
unique opportunity of observing the solar outer atmosphere as close
to the Sun as 0.28 A.U., and from up to 35° out-of-ecliptic. The
telescope design of the METIS coronagraph includes two optical paths:
i) broad-band imaging of the full corona in linearly polarized
visible-light (VL: 580-640 nm), ii) narrow-band imaging of the full
corona in the ultraviolet (UV) Lyman α (121.6 nm). This paper describes
the stray-light analyses performed on the UV and VL channels of the
METIS Telescope with the nonsequential modality of Zemax OpticStudio. A
detailed opto-mechanical model of the METIS Telescope is simulated
by placing the CAD parts of all the sub-assemblies at the nominal
position. Each surface, mechanical and optical, is provided with a
modelled coating and BSDF reproducing the optical and the diffusing
properties. The geometric model allows for the verification of the
correct functioning of the blocking elements inside the telescope
and for an evaluation of the stray-light level due to surface
roughness. The diffraction off the inner edge of the IEO on the plane
of the IO is modelled separately from the contributor of the surface
micro-roughness. The contributors due to particle contamination and
cosmetic defects are also analysed. The results obtained are merged
together and compared to the requirements of stray-light. The results
of this analysis together with those from two different analyses based
on a Montecarlo ray-trace and a semi-analytical model are consistent
with each other and indicate that the METIS design meets the stray-light
level requirements
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: 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: Stereoscopic investigation on plasma density fluctuations in
the outer solar corona
Authors: Telloni, D.; Antonucci, E.; Dolei, S.; Romano, P.; Spadaro,
D.; Ventura, R.
Bibcode: 2014A&A...565A..22T
Altcode:
This research note extends a previous work focused on the 2D
reconstruction of the spatial distribution and temporal evolution of
the plasma density fluctuations in the outer solar corona and based
on STEREO COR1-A white-light observations. By using the corresponding
total brightness images obtained in the same observational period with
the coronagraph COR1-B onboard the "Behind" twin STEREO-B spacecraft,
and adopting the same methodological approach as for COR1-A data, it
was possible to confirm the results of the previous work and argue for
the 3D configuration of the fluctuations of the coronal plasma. This
provides further evidence in support of a scenario in which the
fluctuating features, which are recurrent and spatially coherent, are
localized along the magnetic field lines and points out the crucial
role played by the 3D magnetic field topology in the confinement and
evolution of the plasma density fluctuations.
Title: Stochasticity and Persistence of Solar Coronal Mass Ejections
Authors: Telloni, D.; Carbone, V.; Lepreti, F.; Antonucci, E.
Bibcode: 2014ApJ...781L...1T
Altcode:
The study of the statistical properties of coronal mass ejections
(CMEs) reveals that their properties depend on the period of solar
activity. In particular, when investigating the origin of the waiting
time distribution between CMEs, a significant departure from a Poisson
process during periods of high solar activity has been found, thus
suggesting the existence of at least two physical processes underlying
the origin of CMEs. One acts continuously, perhaps related to randomly
occurring magnetic reconfigurations of the solar corona at large
scales. The other plays a role only during the solar maximum, probably
due to the photospheric emergence of magnetic flux as a statistically
persistent mechanism, which generates long correlation times among CME
events strong enough not to be destroyed by the former random process.
Title: Detection of Plasma Fluctuations in White-light Images of
the Outer Solar Corona: Investigation of the Spatial and Temporal
Evolution
Authors: Telloni, D.; Ventura, R.; Romano, P.; Spadaro, D.;
Antonucci, E.
Bibcode: 2013ApJ...767..138T
Altcode: 2013arXiv1302.3382T
This work focuses on the first results from the identification and
characterization of periodic plasma density fluctuations in the outer
corona, observed in STEREO-A COR1 white-light image time series. A
two-dimensional reconstruction of the spatial distribution and temporal
evolution of the coronal fluctuation power has been performed over
the whole plane of the sky, from 1.4 to 4.0 R ⊙. The
adopted diagnostic tool is based on wavelet transforms. This technique,
with respect to the standard Fourier analysis, has the advantage of
localizing non-persistent fluctuating features and exploring variations
of the relating wavelet power in both space and time. The map of
the variance of the coronal brightness clearly outlines intermittent
spatially coherent fluctuating features, localized along, or adjacent
to, the strongest magnetic field lines. In most cases, they do not
correspond to the visible coronal structures in the brightness maps. The
results obtained provide a scenario in which the solar corona shows
quasi-periodic, non-stationary density variations characterized by
a wide range of temporal and spatial scales and strongly confined
by the magnetic field topology. In addition, structures fluctuating
with larger power are larger in size and evolve more slowly. The
characteristic periodicities of the fluctuations are comparable
to their lifetimes. This suggests that plasma fluctuations lasting
only one or two wave periods and initially characterized by a single
dominant periodicity either rapidly decay into a turbulent mixed flow
via nonlinear interactions with other plasma modes, or they are damped
by thermal conduction. The periodic non-stationary coronal fluctuations
outlined by the closed field lines at low and mid latitudes might be
associated with the existence of slow standing magneto-acoustic waves
excited by the convective supergranular motion. The fluctuating ray-like
structures observed along open field lines appear to be linked either
to the intermittent nature of the processes underlying the generation
of magnetic reconnection in the polar regions or to the oscillatory
transverse displacements of the coronal ray itself.
Title: UVCS Observations of Temperature and Velocity Profiles in
Coronal Holes
Authors: Antonucci, Ester; Abbo, Lucia; Telloni, Daniele
Bibcode: 2013mspc.book....5A
Altcode:
No abstract at ADS
Title: UVCS Observations of Temperature and Velocity Profiles in
Coronal Holes
Authors: Antonucci, Ester; Abbo, Lucia; Telloni, Daniele
Bibcode: 2012SSRv..172....5A
Altcode: 2011SSRv..tmp....9A; 2011SSRv..tmp...96A; 2011SSRv..tmp..172A;
2011SSRv..tmp..339A
The spectroscopic observations of the Ultraviolet Coronagraph
Spectrometer (UVCS), on board the SOHO observatory, allow the study and
the full characterization of the expansion of the solar atmosphere by
means of measurements of the outflow speeds and the physical properties
of the wind, directly in the region where the solar plasma is heated
and accelerated: the extended corona. During solar minimum, when the
magnetic configuration of the corona is rather simple, the open magnetic
fields emerging from the wide polar coronal holes channel toward the
heliosphere both the fast and the slow wind. The fast wind flows along
flux tubes with lower areal divergence than the slow wind which is
guided by flux tubes characterized by non-monotonic areal expansion
functions. Differences in the physical properties, such as kinetic
temperature, electron density, composition and density fluctuations,
of the fast and slow wind in the corona are discussed.
Title: Preliminary internal straylight analysis of the METIS
instrument for the Solar Orbiter ESA mission
Authors: Verroi, Enrico; Da Deppo, Vania; Naletto, Giampiero; Fineschi,
Silvano; Antonucci, Ester
Bibcode: 2012SPIE.8442E..4NV
Altcode:
METIS, the multi element telescope for imaging and spectroscopy, is
a solar coronagraph foreseen for the Solar Orbiter mission. METIS is
conceived to observe the solar corona from a near-sun orbit in three
different spectral bands: in the HeII EUV narrow band at 30.4 nm,
in the HI UV narrow band at 121.6 nm, and in the visible light band
(500 - 650 nm). The visible light from the corona is ten million times
fainter than the light emitted by the solar disk, so a very stringent
light suppression design is needed for the visible channel. METIS
adopts an “inverted occulted” configuration, where the disk light is
shielded by an annular shape occulter, after which an annular aspherical
mirror M1 collects the signal coming from the corona. The disk light
heading through M1 is back-rejected by a suitable spherical mirror
M0. This paper presents the stray light analysis for this new-concept
configuration, performed with a ray tracing simulation, to insure the
opto-mechanical design grants a stray light level below the limit of
10-9 times the coronal signal intensity. A model of the
optics and of the mechanical parts of the telescope has been realized
with ASAP (Breault Research TM); by means of a Montecarlo ray tracing,
the effect of stray light on VIS and UVEUV channels has been
simulated.
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: Optimization of the occulter for the Solar Orbiter/METIS
coronagraph
Authors: Landini, Federico; Vivès, Sébastien; Romoli, Marco; Guillon,
Christophe; Pancrazzi, Maurizio; Escolle, Clement; Focardi, Mauro;
Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero; Nicolini,
Gianalfredo; Nicolosi, Piergiorgio; Spadaro, Daniele
Bibcode: 2012SPIE.8442E..27L
Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy
investigation), selected to fly aboard the Solar Orbiter ESA/NASA
mission, is conceived to perform imaging (in visible, UV and EUV) and
spectroscopy (in EUV) of the solar corona, by means of an integrated
instrument suite located on a single optical bench and sharing the
same aperture on the satellite heat shield. As every coronagraph, METIS
is highly demanding in terms of stray light suppression. Coronagraphs
history teaches that a particular attention must be dedicated to the
occulter optimization. The METIS occulting system is of particular
interest due to its innovative concept. In order to meet the strict
thermal requirements of Solar Orbiter, METIS optical design has been
optimized by moving the entrance pupil at the level of the external
occulter on the S/C thermal shield, thus reducing the size of the
external aperture. The scheme is based on an inverted external-occulter
(IEO). The IEO consists of a circular aperture on the Solar Orbiter
thermal shield. A spherical mirror rejects back the disk-light
through the IEO. A breadboard of the occulting assembly (BOA) has
been manufactured in order to perform stray light tests in front of
two solar simulators (in Marseille, France and in Torino, Italy). A
first measurement campaign has been carried on at the Laboratoire
d'Astrophysique de Marseille. In this paper we describe the BOA design,
the laboratory set-up and the preliminary results.
Title: A prototype of the UV detector for METIS on Solar Orbiter
Authors: Uslenghi, M.; Incorvaia, S.; Fiorini, M.; Schühle, U. H.;
Teriaca, L.; Wilkinson, E.; Siegmund, O. H.; Antonucci, E.; Fineschi,
S.; Naletto, G.; Nicolini, G.; Nicolosi, G.; Romoli, M.; Focardi, M.
Bibcode: 2012SPIE.8443E..3IU
Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy) is one of
the instruments included in the science payload of the ESA mission Solar
Orbiter: a coronograph able to perform broadband polarization imaging
in the visible range, and narrow band imaging in UV (HI Lyman-α)
and EUV (HeII Lyman-α). In addition, it will acquire spectra of the
solar corona simultaneously to UV/EUV imaging. It will be equipped
with two detectors: a hybrid APS dedicated to the visible channel and
an Intensified APS for the UV/EUV channel. The spectroscopic channel
will share the same detector as the UV/EUV corona imaging, with the
spectrum imaged on a portion of the detector not used by the corona
image. We present the development of the UV/EUV detector consisting
of a CMOS APS imaging device to be coupled with a microchannel plate
intensifier. Other than constraints related to the harsh environment
(radiation, temperature, visible stray-light), the METIS UV detector has
the additional challenge of managing different count rates associated
with the three different kind of measurements (UV imaging, EUV imaging
and spectroscopy). The required dynamic range is further extended
since observations will be planned at different distances from the
Sun, varying image scale over a fixed vignetting function. We will
present the architecture of this UV detector, describing the prototype
developed in order to optimize the performance on the overall dynamic
range required by METIS.
Title: Analysis of optical efficiency of METIS coronagraph telescope
on board of the Solar Orbiter mission
Authors: Polito, V.; Corso, A. J.; Zuppella, P.; Nicolosi, P.;
Fineschi, S.; Antonucci, E.; Windt, D. L.; Pelizzo, M. G.
Bibcode: 2012SPIE.8443E..3GP
Altcode:
The Multi Element Telescope for Imaging and Spectroscopy (METIS)
coronagraph is an instrument belonging to the SOLar Orbiter(SOLO)
mission payload which will perform the imaging of the solar corona
in three different spectral ranges: 30.4 nm (He-II Lyman-α line),
121.6 nm (H-I Lyman- α line) and visible spectral range (500-650
nm). Optical coatings with high reflectance performances at the
interested wavelengths are required to collect enough light at the
detector level. Different multilayer structures based on Si/Mo couples
with appropriate capping layers have been already designed and tested to
achieve this purpose. A model has been developed in order to estimate
the efficiency's performances of the instrument on the whole field of
view (FoV) by considering the ray paths. The results shown have been
obtained taking into account of the experimental results on multilayers
structures previously tested and the optical design of the instrument.
Title: Electro-optical polarimeters for ground-based and space-based
observations of the solar K-corona
Authors: Capobianco, G.; Fineschi, S.; Massone, G.; Balboni, E.;
Malvezzi, A. M.; Crescenzio, G.; Zangrilli, L.; Calcidese, P.;
Antonucci, E.; Patrini, M.
Bibcode: 2012SPIE.8450E..40C
Altcode:
Polarimeters based on electro-optically tunable liquid crystals
(LC) represent a new technology in the field of observational
astrophysics. LC-based polarimeters are good candidates for replacing
mechanically rotating polarimeters in most ground-based and space-based
applications. During the 2006 total solar eclipse, we measured the
visible-light polarized brightness (pB) of the solar K-corona with
a LC-based polarimeter and imager (E-KPol). In this presentation,
we describe the results obtained with the E-KPol, and we evaluate its
performances in view of using a similar device for the pB imaging of
the K-corona from space-based coronagraphs. Specifically, a broad-band
LC polarimeter is planned for the METIS (Multi Element Telescope for
Imaging and Spectroscopy) coronagraph for the Solar Orbiter mission to
be launched in 2017. The METIS science driver of deriving the coronal
electron density from pB images requires an accuracy of better than 1%
in the measurement of linear polarization. We present the implications
of this requirement on the METIS design to minimize the instrumental
polarization of the broad-band visible-light (590-650 nm) polarimeter
and of the other optics in the METIS visible-light path. Finally, we
report preliminary ellipsometric measurements of the optical components
of the METIS visible-light path.
Title: The processing and power unit of the METIS coronagraph aboard
the Solar Orbiter space mission
Authors: Focardi, M.; Pancrazzi, M.; Uslenghi, M.; Nicolini, G.;
Magli, E.; Landini, F.; Romoli, M.; Antonucci, E.; Fineschi, S.;
Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.; Gennaro, C.;
Zoppo, G. P.; Stevoli, A.; Battistelli, E.; Rusconi, A.
Bibcode: 2012SPIE.8442E..4IF
Altcode:
The Multi Element Telescope for Imaging and Spectroscopy (METIS) is the
coronagraph selected for the Solar Orbiter payload, adopted in October
2011 by ESA for the following Implementation Phase. The instrument
design has been conceived by a team composed by several research
institutes with the aim to perform both VIS and EUV narrow-band
imaging and spectroscopy of the solar corona. METIS, owing to its
multi-wavelength capability, will address some of the major open issues
in understanding the physical processes in the corona and the solar
wind origin and properties, exploiting the unique opportunities offered
by the SO mission profile. The METIS Processing and Power Unit (MPPU)
is the Instrument's power supply and on-board data handling modular
electronics, designed to address all the scientific requirements of
the METIS Coronagraph. MPPU manages data and command flows, the timing
and power distribution networks and its architecture reflects several
trade-off solutions with respect to the allocated resources in order
to reduce any possible electronics single-point failure. This paper
reports on the selected HW and SW architectures adopted after the
Preliminary Design Review (PDR), performed by ESA in early 2012.
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: Imaging polarimetry with the METIS coronagraph of the Solar
Orbiter mission
Authors: Crescenzio, Giuseppe; Fineschi, Silvano; Capobianco, Gerardo;
Nicolini, Gianalfredo; Massone, Giuseppe; Malvezzi, Marco A.; Landini,
Federico; Romoli, Marco; Antonucci, Ester
Bibcode: 2012SPIE.8443E..3JC
Altcode:
METIS, the "Multi Element Telescope for Imaging and Spectroscopy", is a
coronagraph of the Solar Orbiter mission to be launched in 2017. The
METIS coronagraph includes three optical paths for i) broad-band
imaging of the full corona in polarized visible-light (590-650 nm);
ii) narrow-band coronal imaging in the UV HI Ly α (121.6 nm) and
extreme-UV He II Ly α (30.4 nm), and iii) spectroscopic observations
of the HI and He II Ly α. This presentation describes the optical
design of the METIS visible-light path for imaging polarimetry of the
K-corona. The achromatic polarimeter's requirements on polarization
sensitivity, achromatic response and instrumental polarization control
are described. The expected performances of the visible-light path
are also presented.
Title: Formation of the current sheet in a coronal streamer
Authors: Abbo, Lucia; Antonucci, Ester; Lionello, Roberto; Mikić,
Zoran; Riley, Pete
Bibcode: 2011arXiv1111.2711A
Altcode:
The present work is on the study of a coronal streamer observed
in March 2008 at high spectral and spatial resolution by the
Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO. On the
basis of a spectroscopic analysis of the O VI doublet, the solar wind
plasma parameters are inferred in the extended corona. The analysis
accounts for the coronal magnetic topology, extrapolated through
a 3D magneto-hydrodynamic model. The results of the analysis show
indications on the formation of the current sheet, one of the source
regions of the slow coronal wind.
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: OPSys: optical payload systems facility for testing space
coronagraphs
Authors: Fineschi, S.; Crescenzio, G.; Massone, G.; Capobianco, G.;
Zangrilli, L.; Antonucci, E.; Anselmi, F.
Bibcode: 2011SPIE.8148E..0WF
Altcode: 2011SPIE.8148E..28F
The Turin Astronomical Observatory, Italy, has implemented in ALTEC,
Turin, a new Optical Payload Systems (OPSys) facility for testing of
contamination sensitive optical space flight instrumentation. The
facility is specially tailored for tests on solar instruments like
coronagraphs. OPSys comprises an ISO 7 clean room for instrument
assembly and a relatively large (4.4 m3) optical test
and calibration vacuum chamber: the Space Optics Calibration Chamber
(SPOCC). SPOCC consists of a test section with a vacuum-compatible
motorized optical bench, and of a pipeline section with a sun simulator
at the opposite end of the optical bench hosting the instrumentation
under tests. The solar simulator is an off-axis parabolic mirror
collimating the light from the source with the solar angular
divergence. After vacuum conditioning, the chamber will operate at
an ultimate pressure of 10-6 mbar. This work describes
the SPOCC's vacuum system and optical design, and the post-flight
stray-light tests to be carried out on the Sounding-rocket Experiment
(SCORE). This sub-orbital solar coronagraph is the prototype of the
METIS coronagraph for the ESA Solar Orbital mission whose closest
perihelion is one-third of the Sun-Earth distance. The plans are
outlined for testing METIS in the SPOCC simulating the observing
conditions from the Solar Orbiter perihelion.
Title: Solar Orbiter. The need to go close to the Sun
Authors: Antonucci, E.
Bibcode: 2011MmSAI..82..412A
Altcode:
The key objective of the Solar Orbiter, a mission of the European
Space Agency 'Cosmic Vision' Program, is to fully understand how the
Sun creates and controls the heliosphere. The issues addressed by the
Solar Orbiter concern the solar dynamo, the origin of the solar wind,
of the coronal mass ejections which drive the heliospheric variability,
of the energetic particle radiation which fills the heliosphere. In
order to pursue these investigations a unique mission profile is
proposed. The spacecraft will approach the Sun to within 0.28 AU and
reach an orbit inclination relative to the solar equator exceeding
25 degrees. The proximity to the Sun will also have the advantage
that the spacecraft will fly in near synchronization with the Sun's
rotation. The Solar Orbiter launch is foreseen in January 2017.
Title: Characterization of the slow wind in the outer corona
Authors: Abbo, Lucia; Antonucci, Ester; Mikić, Zoran; Linker, Jon A.;
Riley, Pete; Lionello, Roberto
Bibcode: 2010AdSpR..46.1400A
Altcode: 2010arXiv1008.4452A
The study concerns the streamer belt observed at high spectral
resolution during the minimum of solar cycle 23 with the Ultraviolet
Coronagraph Spectrometer (UVCS) onboard SOHO. On the basis of
a spectroscopic analysis of the O VI doublet, the solar wind
plasma parameters are inferred in the extended corona. The analysis
accounts for the coronal magnetic topology, extrapolated through a 3D
magneto-hydrodynamic model, in order to define the streamer boundary
and to analyse the edges of coronal holes. The results of the analysis
allow an accurate identification of the source regions of the slow
coronal wind that are confirmed to be along the streamer boundary in
the open magnetic field region.
Title: HERSCHEL Sounding Rocket Mission Observations of the Helium
Corona
Authors: Newmark, Jeffrey; Moses, J.; Antonucci, E.; Fineschi, S.;
Abbo, L.; Telloni, D.; Auchere, F.; Barbey, N.; Romoli, M.
Bibcode: 2010AAS...21640721N
Altcode:
The HERSCHEL (Helium Resonant Scattering in the Corona and Heliosphere)
investigation successfully obtained unprecedented images of the helium
and hydrogen components of the solar corona out to 3 solar radii
during a suborbital flight on 14 September 2009. Preliminary analysis
of these observations indicates the spatial distribution of the helium
abundance and outflow velocity provides powerful diagnostics for the
source and dynamics of the slow solar wind during the time of solar
minimum activity. An analysis of co-temporal STEREO EUVI data to derive
the temperature of low coronal structures associated with the regions
of enhanced helium abundance observed by HERSCHEL provides evidence the
relative first ionization potential (FIP) of helium and hydrogen may
play an important role in the observed abundance distribution. NRL
was supported by the Office of Naval Research and NASA under NDPRS6598G.
Title: SOHO/UVCS Detection of Turbulence in a Coronal Mass Ejection
Authors: Telloni, D.; D'Amicis, R.; Antonucci, E.
Bibcode: 2010AIPC.1216..432T
Altcode:
The intensity of the H I Lyα line measured by the UltraViolet
Coronagraph Spectrometer (UVCS) onboard the Solar and Heliospheric
Observatory (SOHO) is used to investigate the density turbulence
within the coronal mass ejection (CME) occurred on 2006 December 24,
in the South polar coronal hole. In order to compare the spectral index
inside the CME with those found in the undisturbed coronal plasma,
we examined the CME data by applying the wavelet technique. This
temporal analysis reveals, during the whole observation time, the
existence of large-scale density fluctuations of periods from tens of
minutes to a few hours. However, during the CME, the power spectrum
becomes less steep with a spectral slope about 5/3, typical of the
turbulent regime, whilst prior to the CME and in the recovery phase
the spectral slope is about 3. The Kolmogorov-like spectrum observed
within the CME is evidence for the nearly incompressible turbulent
character of the CME plasma. This spectrum is significantly different
from that of the high-speed flow from coronal holes and the low-speed
wind originating above closed-field coronal streamers. This result is
particularly important to advance in the understanding of where the
main source of CME flux injection resides.
Title: Dynamics of the large-scale corona
Authors: Antonucci, Ester; Moses, Daniel
Bibcode: 2010cosp...38.2939A
Altcode: 2010cosp.meet.2939A
Ultraviolet spectroscopic observations, obtained throughout a
solar cycle with the UVCS coro-nagraph onboard SOHO, have revealed
the characteristics of the large-scale dynamics of the corona out
to approximately 5 solar radii, both in quiescent and in active
periods. Whilst the source and dynamics of the fast wind plasma in
coronal holes are rather well established, the source/sources of the
slow wind is/are still under debate. The UVCS observations, at least
during periods of minimum of activity, are favoring as sources of
the slow wind the edges of coronal holes, where the magnetic topology
is different and the divergence of magnetic field lines guiding the
coronal wind is higher than in the core of coronal holes. These results
are mainly based on the dynamics of the oxygen ion component. Recently
a successful launch of the SCORE coronagraph, flown as part of the
HERSCHEL payload, has provided the first map of the emission in the
He 304 line of the outer corona which indicates abundance effects
related to the dynamics in the region of interface between coronal
hole and streamer.
Title: Statistics of Density Fluctuations During the Transition from
the Outer Solar Corona to the Interplanetary Space
Authors: Telloni, D.; Bruno, R.; Carbone, V.; Antonucci, E.;
D'Amicis, R.
Bibcode: 2009ApJ...706..238T
Altcode:
This paper investigates the evolution of the plasma density
fluctuations of the fast and slow solar wind from the solar corona
into the interplanetary space. The study is performed by comparing the
low-frequency spectra and the phase correlation of the proton density
oscillations, measured in the inner heliosphere with the Helios 2
in situ instrumentation, with those due to the large-scale density
perturbations observed with UVCS/SOHO in the outer corona. We find that
the characteristics of density fluctuations of the fast solar wind
are maintained in the transition from the outer corona to the inner
heliosphere, thus suggesting a coronal imprint for the heliospheric
large-scale 1/f 2 noise spectrum. In contrast, a quick
dynamical evolution is observed in the slow wind, which, starting from
large-scale fluctuations with strong phase correlations in the outer
corona, gives rise to a Kolmogorov-like spectrum and an accumulation
of density structures at small scales at 0.3 AU. This can be explained
in the framework of nearly incompressible turbulence.
Title: The astronomical Torino Observatory: the history
Authors: Antonucci, Ester
Bibcode: 2009lnu..confE..16A
Altcode:
No abstract at ADS
Title: Preface to the Proceedings of the European General Assembly
on IHY 2007
Authors: Briand, C.; Antonucci, E.; Haubold, H. J.
Bibcode: 2009EM&P..104....1B
Altcode: 2009EM&P..tmp....3B
No abstract at ADS
Title: Persistent and Self-Similar Large-Scale Density Fluctuations
in the Solar Corona
Authors: Telloni, D.; Antonucci, E.; Bruno, R.; D'Amicis, R.
Bibcode: 2009ApJ...693.1022T
Altcode:
Density fluctuations of the low and midlatitude solar corona plasma are
analyzed during the recent solar minimum period. Long time series of the
intensity of the neutral hydrogen Lyα, 1216 Å, line have been observed
with the UltraViolet Coronagraph Spectrometer/Solar and Heliospheric
Observatory at 1.7 R sun, in low-latitude streamers and
in regions where the slow solar wind is accelerated. Their frequency
composition is investigated by using three different techniques, namely
the Fourier, the Hurst, and the phase coherence analyses. The Fourier
analysis reveals the existence of low-frequency f -α power
spectra in the range from ~3 × 10-6 Hz to ~10-4
Hz, corresponding to periods from a few hours to a few days. The
coronal density fluctuations are dominated by discontinuities separating
structures with a minimum characteristic timescale of about 3 hr and
a corresponding spatial scale of about 3 × 104 km. The
nonlinear analysis technique based on the structure functions shows that
for large timescales the coronal density fluctuations are statistically
self-affine and give rise to an average Hurst exponent langHrang = 0.654
± 0.008. This indicates that the process underlying the variability of
the corona and the slow wind at coronal level is a persistent mechanism,
generating correlations among the plasma density fluctuations. Finally,
the analysis based on the phase coherence index shows a high degree
of phase synchronization of the coronal density variations for large
timescales, which shows that the solar corona is dominated by phase
coherent structures. The results of the analysis suggest a coupling
of the variability of the solar corona and the photospheric dynamics
induced by the convection at supergranular scale.
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: Investigation on the Possible Coupling Between Coronal
Variability and Photospheric Dynamics
Authors: Antonucci, E.; Telloni, D.; Bruno, R.; D'Amicis, R.
Bibcode: 2008AGUFMSH41A1601A
Altcode:
Density fluctuations are observed with the Ultraviolet Coronagraph
Spectrometer - UVCS - operating onboard the SOHO spacecraft in the
solar corona plasma of the regions of the low-latitude streamers and
where the slow solar wind is accelerated. The results of the Fourier
analysis, performed on solar minimum data, show that the coronal density
fluctuations are dominated by discontinuities with a minimum temporal
scale consistent with the lifetime of the photospheric supergranulation
cells, thus suggesting a possible coupling of the variability of the
solar corona and the dynamics of photospheric supergranulation. The
spectral power derived on the basis of a Fourier analysis decreases
with frequency as ν-2 from 10 to 100 μ Hz, in the frequency range
where the supergranular motions mainly contribute to the photospheric
intensity background, as observed for instance with VIRGO/SOHO. The
fit of the low-frequency coronal spectra, performed according to the
Harvey (1985) approach, yields a time constant of about 9×104 s,
consistent with the time scales of the supergranulation regime in the
solar noise. Furthermore, the degree of persistency of the density
variations observed in the outer corona, derived by applying the Hurst
analysis, is consistent with that inferred by Nesis et al. (1994), who
investigated the dynamics of the solar granulation, by analyzing the
photospheric intensity oscillations. The present results thus imply
that the processes underlying the photospheric dynamics and coronal
variability show common characteristics.
Title: Investigation of the solar wind outflows and joint observations
during the total solar eclipse of March 29, 2006
Authors: Abbo, Lucia; Zangrilli, Luca; Antonucci, Ester; Fineschi,
Silvano; Kohl, John; Giordano, Silvio; Massone, Giuseppe; Capobianco,
Gerardo; Calcidese, Paolo; Porcu, Francesco
Bibcode: 2008cosp...37....7A
Altcode: 2008cosp.meet....7A
During the total solar eclipse of 29 March 2006, SOHO observations of
JOP158 were coordinated with ground based instruments. In particular,
the Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO has
observed the south coronal hole in the OVI doublet emission in order
to probe the role of plume and interplume regions in the dynamics of
the fast solar wind. From the analysis of the polarized K-solar corona
measurements obtained with the EKPol polarimeter from the site of c
(desert of Sahara, Lybia), we estimate the coronal electron density
radial profiles and perform a Doppler dimming analysis of the OVI
doublet line intensities to measure the outflow velocity.
Title: Activities in Italy for the International Heliophysical Year
Authors: Antonucci, Ester
Bibcode: 2008cosp...37..106A
Altcode: 2008cosp.meet..106A
A summary of the Italian activities developed in the frame of the
International Heliophysical Year will be reported. In particular,
we present the initiatives of outreach that have included public
conferences, exhibits, courses for young researchers and activities
in the schools. Moreover, some projects with students are extended to
2008-2009 for monitoring the solar activity at the beginning of solar
cycle 24.
Title: Evidence for Power Law in the Spectrum of the Coronal
Ly-alpha Line
Authors: Telloni, Daniele; Antonucci, Ester; Bruno, Roberto; D'Amicis,
Raffaella
Bibcode: 2008cosp...37.3165T
Altcode: 2008cosp.meet.3165T
Long time series of the intensity of the hydrogen Lyα line revealed the
existence of f-2 power spectra in the corona at low and mid latitudes
and very close to the Sun, at 1.7 solar radii. These observations
are performed with the UltraViolet Coronagraph Spectrometer (UVCS)
on board the Solar and Heliospheric Observatory (SoHO). A preliminary
analysis indicates that this scaling extends for more than a decade and
terminates at higher frequencies with a flat spectrum indicating the
presence of white-noise fluctuations. The frequency corresponding to
the knee which separates these two different spectral regimes moves
to lower and lower values for observations performed at higher and
higher heliographic latitudes. Low-frequency power spectra with a f-2
dependence may be due rapid changes (jumps) in the time series. If
these coherent structures are removed from the time series, hydrogen
coronal intensity power spectra seem to show a power law following
the f-1 scaling which would suggest that 1/f interplanetary noise
originates in corona.
Title: Numerical studies on neutral solar wind flux at Solar Orbiter's
perihelion
Authors: D'Amicis, Raffaella; Mura, Alessandro; Orsini, Stefano;
Hilchenbach, Martin; Hsieh, K. C.; Telloni, Daniele; Bruno, Roberto;
Antonucci, Ester
Bibcode: 2008cosp...37..621D
Altcode: 2008cosp.meet..621D
Solar wind neutral hydrogen, flowing together with the ionized
component, has basically a different phase-space distribution
function. As a matter of fact, contrary to the ionized component,
neutrals can cover long distances on ballistic trajectories,
unmodified by magnetic and electric fields. As a consequence, once
decoupled from protons, neutral hydrogen atoms retain information on
the three-dimensional distribution of protons at the location where they
are generated. In the present study, we perform numerical simulations of
neutral hydrogen flux distribution to be measured by Solar Orbiter at a
perihelion distance of 48 solar radii (RS ), using different models of
solar wind expansion and considering neutral hydrogen coming from fast
and slow solar wind. By analysing flux distributions as a function of
energy and heliocentric distance, we find that the generation region
of neutral hydrogen is at approximately 10 RS for fast wind and at
about 20 RS for slow wind. Moreover, the differential flux in angle
shows that the signal is concentrated in a small region around the
Sun direction. The width of this region depends on the solar wind
model applied, and may be up to 10° for fast wind and up to 20° for
slow wind.
Title: Characterization of the slow solar wind in the outer corona
Authors: Abbo, Lucia; Dodero, Maria Adele; Mikic, Zoran; Riley, Pete;
Antonucci, Ester
Bibcode: 2008cosp...37....8A
Altcode: 2008cosp.meet....8A
The study concerns the streamer belt observed during the minimum of
solar activity with the Ultraviolet Coronagraph Spectrometer (UVCS)
onboard SOHO. On the basis of a spectroscopic analysis of the O
VI doublet and HI Ly α lines, the solar wind plasma parameters are
inferred in the extended corona. The analysis accounts for the coronal
magnetic topology, extrapolated through a 3D magneto-hydrodynamic
model, in order to define the streamer boundary and to analyse the
edges of coronal holes. The results of the analysis allow an accurate
identification of the source regions of the slow coronal wind that
are confirmed to be along the streamer boundary in the open magnetic
field region.
Title: Oxygen temperature anisotropy and solar wind heating above
coronal holes out to 5 R⊙
Authors: Telloni, D.; Antonucci, E.; Dodero, M. A.
Bibcode: 2007A&A...476.1341T
Altcode:
The purpose of the paper is to measure the degree of temperature
anisotropy of the oxygen ions in the outer corona. The ratio of the
Doppler dimmed O VI 1037-1032 line intensity as a function of the
velocity of the fast solar wind, computed for typical values of coronal
density, is consistent with the observed ratio, only when a significant
temperature anisotropy is established in polar coronal holes. The oxygen
ion velocity distribution is constrained to be bi-Maxwellian from 2R_⊙
to 3.7R_⊙, where the lowest degree of anisotropy compatible with the
observational data increases up to ~7 at 2.9R_⊙, proving that the
oxygen ions are accelerated across the magnetic field, in accordance
with a preferential energy deposition perpendicular to the field lines,
consistent with the process of ion-cyclotron dissipation of Alfvén
waves. The most plausible evolution of the velocity distribution of
the O+5 ions departs from the bi-Maxwellian configuration
at 2R_⊙, according to an anisotropy ratio that reaches its maximum
value T_⊥/T_∥~14 at 2.9R_⊙, and further out approaches isotropy,
at 3.7R_⊙. In response to the acceleration across the field, energy
redistribution along the magnetic field lines accelerates the oxygen
component of the solar wind to velocities of 760 km s-1 at
5R_⊙. The variation of the anisotropy ratio with the heliocentric
distance might be satisfactorily explained by theoretical models of
the fast solar wind heating based on the oxygen cyclotron instability
or the fast shock mechanism. The observations of the extended corona
analyzed in this paper are performed with the Ultraviolet Coronagraph
Spectrometer on board the Solar Heliospheric Observatory, during the
solar minimum activity period 1996-1997.
Title: Numerical studies on neutral solar wind generated at high
and low solar latitudes
Authors: D'Amicis, R.; Telloni, D.; Orsini, S.; Mura, A.; Milillo,
A.; di Lellis, A.; Antonucci, E.; Hilchenbach, M.
Bibcode: 2007AGUFMSH21A0291D
Altcode:
In this work, we examine the properties of the neutral solar wind
(NSW) emanating from the solar corona above few solar radii, at low and
high solar latitudes. It is important to study NSW because it allows
us to investigate the acceleration region of the solar wind. In fact,
neutrals retain information on the three-dimensional distribution of
hydrogen at the level where they are generated as the proton velocity
distribution is frozen within the generated neutrals and transferred
up to our observation point. NSW is flowing together with the ionized
solar wind, but it has basically different characteristics in its phase
space distribution function. In fact, contrary to the ionized component,
NSW is unmodified along the way from the originating source. In this
particular study, we will consider as our vantage point the Solar
Orbiter position.
Title: Outflow velocity of the O+5 ions in polar coronal
holes out to 5 R⊙
Authors: Telloni, D.; Antonucci, E.; Dodero, M. A.
Bibcode: 2007A&A...472..299T
Altcode:
The purpose of the paper is to extend the measurement of the kinetic
temperature and outflow velocity of the oxygen ions in the outer
corona above polar holes out to 5 R_⊙. An analytical model of the
solar corona at the minimum of activity has been employed in order
to synthesize the spectral line profiles to be fitted with the data:
the kinetic temperature of the O+5 ions on the plane of
the sky is derived from the width of the O VI 1031.9 Å line by
applying the χ2 minimization. The oxygen temperature
peaks at about 2.9 R_⊙, reaching a value of 1.5 × 108
K, and further out it is somehow flattening. The outflow velocity
of the oxygen component of the fast solar wind, derived from the
intensity ratio of the Doppler dimmed O VI doublet, increases outward
to reach 550-760 km s-1 at 5 R_⊙. The upper and lower
limits of the outflow speed are due to the fact that its measurement
depends on the velocity distribution of the oxygen ions which cannot
be directly measured along the radial direction, but only along the
line of sight. Hence the uncertainty is related to the temperature
anisotropy assumed in the analysis. For this reason in this paper
the measurement of the temperature anisotropy, found beyond 2 R_⊙
according to the previous literature on UVCS results, has been as well
extended at higher altitudes, and it is found that above 3.7 R_⊙
anisotropy can still exist but not necessarily. The observations of
the extended corona analyzed in this paper are performed with the
Ultraviolet Coronagraph Spectrometer on board the Solar Heliospheric
Observatory, during the solar minimum activity period 1996-1997.
Title: Numerical simulations of coronal hole-associated neutral
solar wind as expected at the Solar Orbiter position
Authors: D'Amicis, R.; Orsini, S.; Antonucci, E.; di Lellis, A. M.;
Hilchenbach, M.; Telloni, D.; Mura, A.; Milillo, A.; Fineschi, S.;
Bruno, R.
Bibcode: 2007JGRA..112.6110D
Altcode: 2007JGRA..11206110D
Neutral hydrogen is indicative of the behavior of the main solar wind
component formed by protons out to at least 5 R⊙. In
fact, beyond this distance, the characteristic time for charge
exchange between hydrogen atoms and protons becomes larger than the
coronal expansion timescale, causing the neutrals to decouple from
the charged solar wind. The mean free path of the neutral component
rapidly increases with the radial distance so that neutrals generated
at heliocentric distances ≥24 R⊙ fly unperturbed and
eventually are detected by Solar Orbiter (perihelion at approximately
48 R⊙), since their mean free path is long enough to
let neutrals reach the neutral solar wind detector. However, the
computation of the differential flux shows that the bulk of the flux
detected at the Solar Orbiter vantage point mainly comes from about 9
R⊙. Neutrals retain information on the three-dimensional
distribution of hydrogen at the level where they are generated as the
proton velocity distribution is frozen within the generated neutrals
and transferred up to the Solar Orbiter position. In the present study,
we report our preliminary results from our simulation of the neutral
solar wind distribution as predicted at the Solar Orbiter position and
considering the evolution of a coronal hole-emerging solar wind whose
major parameters are estimated by the Solar and Heliospheric Observatory
(SOHO) Ultraviolet Coronagraph Spectrometer (UVCS) experiment. The
synergy between corona remote sensing and in situ neutral particle
observations will enable us to infer the degree of anisotropy, if any,
in the neutral and charged coronal hydrogen close to the Sun.
Title: Wind in the Solar Corona: Dynamics and Composition
Authors: Antonucci, Ester
Bibcode: 2007sdeh.book...35A
Altcode:
No abstract at ADS
Title: S olar Orbiter Neutral Solar Wind Detector
Authors: Hilchenbach, M.; Orsini, S.; Hsieh, K. C.; Antonucci, E.;
Barabash, S.; Bamert, K.; Bruno, R.; Collier, M. R.; Czechowski,
A.; D'Amicis, R.; De Angelis, E.; Dandouras, I.; Di Lellis, A. M.;
Esser, R.; Giacalone, J.; Gruntman, M.; Habbal, S. R.; Jokipii, J. R.;
Kallio, E.; Kota, J.; Kucharek, H.; Leoni, R.; Livi, S.; Mann, I.;
Marsch, E.; Massetti, S.; Milillo, A.; Möbius, E.; Mura, A.; Sheldon,
R. B.; Schmidt, W.; Selci, S.; Szego, K.; Woch, J.; Wurz, P.; Zanza,
V.; Zurbuchen, T. H.
Bibcode: 2007ESASP.641E..46H
Altcode:
Neutral hydrogen atoms, which give rise to the prominent so lar Ly-α
corona, are closely coup led to the emerging solar-wind plasma. The
density ratio of neutral hydrogen to protons is minute, ~10-6;
therefore, the neutral atoms are tracers in the solar wind. In-situ
observations of the neutral atoms, their flight paths (imag ing),
density, and velocity distribu tions are a new tool to the understanding
of the Ly-α corona, i.e. setting limits on the plasma velocity
distribution along the solar magnetic field lines. The other goal of
the neutral solar- wind instrumentation is the in-situ observation
of the interactions between solar wind plasma and dust grains near
the Sun. We will discuss the science objectives and the potential
"zero charge" solar-wind instrument envelope onboard Solar Orbiter .
Title: Numerical Simulations Of The Neutral Solar Wind Distribution
As Expected At The Solar Orbiter Position
Authors: D'Amicis, R. D.; Orsini, S.; Antonucci, E.; Hilchenbach, M.;
Di Lellis, A. M.; Telloni, D.; Fineschi, S.; Milillo, A.; Bruno, R.;
Mura, A.; De Angelis, E.
Bibcode: 2007ESASP.641E..10D
Altcode:
Neutral hydrogen is indicative of the behavior of the main solar wind
component formed by protons out to at least 5 solar radii. In fact,
beyond this distance the characteristic time for charge exchange
between hydrogen atoms and protons becomes shorter than the coronal
expansion time scale causing the neutrals to decouple from the
charged solar wind. However they retain information on the three-
dimensional coronal distribution of hydrogen at the distance where they
are generated. Considering the great importance of neutral solar wind
(NSW) measurements to understand the evolution of the main solar wind
component after decoupling from the neutrals, a NSW detector is at the
moment one of the High Priority Augmentation instruments of the Solar
Orbiter mission. In the present study, we report our preliminary results
concerning the simulation of the NSW distribution as expected at the
Solar Orbiter position. We consider the evolution of a coronal-hole
emerging solar wind whose major parameters are estimated by the
SOHO UVCS experiment. The synergy between in- itu and remote sensing
measurements will enable us to infer the degree of anisotropy, if any,
in the neutral and charged coronal hydrogen close to the Sun.
Title: T he HERSCHEL/SCORE Visible And UV Coronagraph
Authors: Romoli, M.; Capobianco, G.; Da Deppo, V.; Fineschi, S.;
Focardi1, M.; Gherardi1, A.; Landini1, F.; Malvezzi, M. A.; Naletto,
G.; Nicolosi, P.; Pace, E.; Pancrazzi, M.; Pelizzo, M. G.; Rossi,
G.; Zangrilli, L.; Antonucci, E.
Bibcode: 2007ESASP.641E..79R
Altcode:
The Herschel (HElium Resonant Scattering in the Corona and HELiosphere)
experiment, approved by NASA in 2003 within the Living With a Star
program, to be flown on a sounding rocket, is designed to investigate
the helium coronal abundance and the solar wind acceleration region
by obtaining the first simultaneous observations of the electron,
proton and helium solar corona. The HER- SCHEL payload consists of
several instruments that image the solar corona in the EUV and in the
visible from the disk to the extended corona. SCORE (Solar CORono-
graph Experiment) is a coronagraph that has the capabil- ity of
imaging the solar corona from 1.4 to 3.5 solar radii in the EUV lines
of HI 121.6 nm and HeII 30.4 nm and in the visible broadband polarized
brightness. The SCORE coronagraph consists of an externally occulted
reflecting telescope in off-axis gregorian configuration with a novel
design in the stray light rejection. The use of multilayer mirrors
in normal incidence makes possible the observa- tions in all three
wavelength bands with the same telescope. HERSCHEL/SCORE aims also at
testing in space the performances of this design and establishing a
proof- of-principle for the Ultraviolet Coronagraph of Solar Orbiter.
Title: Slow Coronal Wind Composition
Authors: Abbo, Lucia; Antonucci, Ester; Dodero, Maria Adele; Mikić,
Zoran; Riley, Pete
Bibcode: 2006ESASP.617E..17A
Altcode: 2006soho...17E..17A
No abstract at ADS
Title: On VI Kinetic Temperature and Outflow Velocity in Solar Corona
Beyond 3R????
Authors: Telloni, D.; Antonucci, E.; Dodero, M. A.
Bibcode: 2006ESASP.617E.110T
Altcode: 2006soho...17E.110T
No abstract at ADS
Title: Oxygen Abundance and Energy Deposition in the Slow Coronal Wind
Authors: Antonucci, E.; Abbo, L.; Telloni, D.
Bibcode: 2006ApJ...643.1239A
Altcode:
Observations of the extended corona obtained with the Ultraviolet
Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric
Observatory (SOHO) during the solar minimum years 1996 and 1997 have
been analyzed to derive the oxygen abundance in the outer corona. A
comparison of the absolute coronal abundance, measured in the coronal
regions surrounding the quiescent solar minimum streamers, to the
heliospheric values confirms that these regions are the dominant sources
of the slow solar wind. However, the inferred coronal abundances are
consistent with the heliospheric values only in case the ion velocity
distribution is anisotropic and enhanced across the coronal magnetic
field. Thus this analysis also leads to the conclusion that energy is
deposited in the slow coronal wind at least up to 2.7 Rsolar
and that the efficiency of energy deposition is likely to be related
to the local coronal magnetic topology.
Title: Wind in the Solar Corona: Dynamics and Composition
Authors: Antonucci, Ester
Bibcode: 2006SSRv..124...35A
Altcode: 2007SSRv..tmp...49A
The dynamics of the solar corona as observed during solar minimum
with the Ultraviolet Coronagraph Spectrometer, UVCS, on SOHO is
discussed. The large quiescent coronal streamers existing during this
phase of the solar cycle are very likely composed by sub-streamers,
formed by closed loops and separated by open field lines that are
channelling a slow plasma that flows close to the heliospheric current
sheet. The polar coronal holes, with magnetic topology significantly
varying from their core to their edges, emit fast wind in their central
region and slow wind close to the streamer boundary. The transition
from fast to slow wind then appears to be gradual in the corona,
in contrast with the sharp transition between the two wind regimes
observed in the heliosphere. It is suggested that speed, abundance
and kinetic energy of the wind are modulated by the topology of the
coronal magnetic field. Energy deposition occurs both in the slow and
fast wind but its effect on the kinetic temperature and expansion rate
is different for the slow and fast wind.
Title: A New Way to look at Observations with EGSO
Authors: Aboudarham, J.; Scholl, I.; Fuller, N.; Csillaghy, A.;
Bentley, R. D.; Antonucci, E.; Ciminiera, L.; Finkelstein, A.; Ipson,
S.; Messerotti, M.; Pike, D.; Vial, J. C.; Zharkova, V.
Bibcode: 2006IAUS..233..229A
Altcode:
The European Grid of Solar Observations (EGSO) is a Solar virtual
observatory (see Hill et al., 2002). It has been funded through the 5th
Framework Program of the European Community. A dozen of laboratories,
mixing Solar Physics and Information Technology, in Great Britain,
France, Italy and Swiss have been involved in this project during
3 years. A grid accessing several dozens of databases and archives
scattered all around the world has been developped as well as a Solar
Event Catalogue and a Solar Feature Catalogue. The original aspect
of this work consists in the possibility not only to search through
the characteristics of observations, but also search for available
data corresponding to specific kinds of events. So it is now very
important to be able to follow the Sun 24 hours a day in order to
enrich the events database for future queries. More informations on
EGSO, catalogues and user interface can be accessd through the web
site: http://www.egso.org/
Title: European Grid of Solar Observations (EGSO)
Authors: Aboudarham, J.; Scholl, I.; Csillaghy, A.; Bentley, R. D.;
Antonucci, E.; Ciminiera, L.; Finkelstein, A.; Ipson, S.; Messerotti,
M.; Pike, D.; Vial, J. C.; Zharkova, V.
Bibcode: 2006ihy..conf...18A
Altcode:
The EGSO project addresses the problem of combining heterogeneous
data into a single "virtual" solar data resource. Wider access to
other catalogues is enabled, including both pre-existing lists and
new compilations generated using feature-recognition techniques on
existing data. Scientists are also able to perform much richer data
searches, based on solar events. Informations concerning EGSO can be
found at http://www.egso.org/
Title: Characteristics of the coronal slow wind acceleration regions
Authors: Antonucci, E.; Abbo, L.; Telloni, D.
Bibcode: 2006cosp...36.3627A
Altcode: 2006cosp.meet.3627A
Spectroscopic observations of the extended corona obtained during
solar minimum with the Ultraviolet Coronagraph Spectrometer UVCS on
board SOHO the Solar and Heliospheric Observatory have been analyzed
to derive the oxygen abundance in regions where the slow coronal wind
is observed We find that the oxygen abundance of the slow coronal wind
is consistent with that measured in the heliospheric low-speed streams
Moreover there is evidence of anisotropy of the oxygen ion velocity
distributions which is suggesting that energy is deposited across the
magnetic field in the slow coronal wind at least up to 2 7 solar radii
Title: Spectroscopic measurement of OVI kinetic temperature and
outfow velocity in a polar coronal hole
Authors: Telloni, D.; Antonucci, E.; Dodero, M. A.
Bibcode: 2006cosp...36.3600T
Altcode: 2006cosp.meet.3600T
The profile of the solar spectrum where the OVI doublet originates
is determined by the merging of intense OVI 1031 9 1037 6 AA and HI
1025 7 AA and faint lines such as HeI 515 60 AA and FeIII 1035 77 AA
These lines are broadened by the microscopic velocity distribution
of the emitting ions and atoms and macroscopically the expansion
of the solar corona in open field line regions The profile of the
observed spectrum is further shaped by the instrumental broadening
and the stray light contribution The accuracy of the results on OVI
kinetic temperature and wind velocity depends on the accuracy of the
physical parameters and structures used to describe the corona and
the heliosphere and also on the procedure adopted in the analysis In
order to take into account all this a new diagnostic method has been
developed to evaluate the OVI kinetic temperature in a polar coronal
hole observed with UVCS SOHO It reaches a maximum value of sim 2 cdot 10
8 quad K at about 2 5 R then decreases for larger heliocentric distances
furtherout r 3 3 R this quantity increases again As a consequence also
new outflow velocity values are estimated with a re-assessment of the
contribution of micro and macro velocity fields and instrument effects
it is monotonically increasing outward to reach 450-500 km s at sim 4 R
Isotropic distribution of the ions cannot explain the observed outflow
velocity and for r 2 R the anisotropic one is necessary Finally the
heating process in the polar coronal holes likely
Title: SOLARNET-Italian Solar Archive Federation. The First Italian
Virtual Observatory Application
Authors: Volpicelli, C. A.; Antonucci, E.; Cora, A.; Giordano, S.;
Messerotti, M.; Santin, A.; Zlobec, P.; Severino, G.; Oliviero, M.;
DeMarino, I.; Alvino, R.; Straus, T.; Ermolli, I.; Centrone, C.;
Perna, C.; Zuccarello, F.; Romano, P.; Spadaro, D.; Contarino, L.
Bibcode: 2006MSAIS...9..129V
Altcode:
We describe the implementation of the national project SOLARNET (SOLar
ARchive NETwork) aimed at federating the heterogeneous Italian solar
data archives into a VO (Virtual Observatory) framework as a single
integrated database, and providing users with tools to search and
retrieve specific data sets. It interoperates using the SOAP/XML
Web Services exposed by each single node and managed via a unified
Portal.This project is the first real Italian Virtual Observatory
application using the standard defined by the IVOA (International
Virtual Observatory Alliance) working groups.
Title: Solar Wind Outflow in Polar Plumes from 1.05 to 2.4
Rsolar
Authors: Gabriel, A. H.; Abbo, L.; Bely-Dubau, F.; Llebaria, A.;
Antonucci, E.
Bibcode: 2005ApJ...635L.185G
Altcode:
An earlier publication (Paper I), which measured the outflow velocity in
solar plumes out to 1.35 Rsolar using the Doppler dimming
technique, has here been extended out to 2.4 Rsolar
by including observations from SOHO UVCS. It is shown that plume
outflow velocities, greater than interplumes at lower heights, have
lower acceleration and fall below interplume velocities at heights
greater than 1.6 Rsolar. This analysis resolves what has
been an apparent disagreement between previously published work. The
mass flow rate in plumes is shown to decrease with height, presumably
through mass transfer to the interplume regions.
Title: KPol: liquid crystal polarimeter for K-corona observations
from the SCORE coronagraph
Authors: Fineschi, Silvano; Zangrilli, Luca; Rossi, Guglielmo; Gori,
Luca; Romoli, Marco; Corti, Gianni; Capobianco, Gerardo; Antonucci,
Ester; Pace, Emanuele
Bibcode: 2005SPIE.5901..389F
Altcode:
We describe the design and first calibration tests of an imaging
polarimeter based on Liquid Crystal Variable Retarders (LCVRs),
for the study of the solar K-corona. This K-polarimeter (KPol) is
part of the visible light path of the UltraViolet and Visible-light
Coronal Imager (UVCI) of the Sounding-rocket Coronagraphic Experiment
(SCORE). SCORE/UVCI is an externally occulted, off-axis Gregorian
telescope, optimized for the narrow-band (i.e., λ/▵λ ~10) imaging
of the HeII, λ 30.4 nm and HI λ 121.6 nm coronal emission. We
present some preliminary results of the application of LCVR plates
to measurements of linear polarized radiation. LCVR plates replace
mechanically rotating retarders with electro-optical devices, without
no moving parts. LCVR are variable waveplates, in which the change of
the retardance is induced by a variable applied voltage. The retardance
of a LCVR is a function of the wavelength. KPol observations of the
visible coronal continuum of the Sun (K-corona) will be made over the
450-600 nm wavelength band. We have studied the LCVR's properties in
this bandpass. We tested a LCVR plate assembled in a linear polarization
rotator configuration to measure the polarization plane rotation of
input radiation as a function of wavelength. We estimated the LCVR's
chromatic response in the KPol wavelength bandpass. The preliminary
results show reasonable achromatic behaviour at high regimes of the
driving voltage, Vd (i.e., Vd>3 volt).
Title: Space applications of Si/B4C multilayer coatings at
extreme ultra-violet region; comparison with standard Mo/Si coatings
Authors: Frassetto, F.; Garoli, D.; Monaco, G.; Nicolosi, P.;
Pascolini, M.; Pelizzo, M. G.; Mattarello, V.; Patelli, A.; Rigato,
V.; Giglia, A.; Nannarone, S.; Antonucci, E.; Fineschi, S.; Romoli, M.
Bibcode: 2005SPIE.5901..161F
Altcode:
In the extreme ultra-violet region, multilayer coatings are the only
technique to obtain high reflectivity in normal incidence optical
configurations. The interference process which regulates periodic
multilayers behavior offers narrow-band spectral filtering without the
use of additional filters, fact that makes these coatings particularly
suitable for lines emission observations. Despite the large amount of
possible materials combinations, Mo/Si multilayers are the standard
choice for space research on plasma physics in the 13 - 30 nm spectral
region. In this work Si/B4C is presented as an alternative
material couple for the 30.4 nm selection. Attractive features are the
better spectral purity and the second order reflectivity reduction. A
possible application to the Sounding CORonagraph Experiment is
described as an example. B4C thin films have been used to
characterize this material in terms of optical constants in the 40 nm -
150 nm spectral region where, currently, only few data are available.
Title: Slow wind and magnetic topology in the solar minimum corona
in 1996-1997
Authors: Antonucci, E.; Abbo, L.; Dodero, M. A.
Bibcode: 2005A&A...435..699A
Altcode:
This study examines the physical conditions of the outer solar
corona in order to identify the regions where the slow solar wind is
accelerated and to investigate the latitudinal transition from slow to
fast wind during the minimum of the solar cycle. The analysis is based
on observations of six streamers obtained during the years of solar
minimum, 1996 and 1997, with the Ultraviolet Coronagraph Spectrometer
(UVCS) onboard the Solar and Heliospheric Observatory (SOHO). The
outflow velocity of the oxygen ions and the electron density of
the coronal plasma are determined in altitude ranging from 1.5 to
3.5 solar radii (R⊙). The adopted diagnostic method,
based on spectroscopic analysis of the O VI 1032 and 1038 Å lines,
fully accounts for the large expansion factor of the magnetic field
lines expected in the regions surrounding the streamers. The analysis
leads to the conclusion that the slow coronal wind is observed (i)
in the region external to and running along the streamer boundary; and
(ii) in the region above the streamer core beyond 2.7 R_⊙, where the
transition between closed and open magnetic field lines takes place
and the heliospheric current sheet forms. Regions in the immediate
vicinity of the streamer boundary can be identified with the edges of
the large polar coronal holes that characterize solar minimum. Results
point to gradual variations of the properties of a coronal hole from
the streamer boundary to its polar core, most likely related to the
topology of the coronal magnetic field.
Title: EGSO - A maturing VO for Solar Physics
Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Aboudarham, J.;
Antonucci, E.; Gurman, J.; Hill, F.; Pike, D.; Vial, J.; Zharkova, V.
Bibcode: 2005AGUSMSH43B..01B
Altcode:
The European Grid of Solar Observations, EGSO, is a Grid test-bed
funded under the Information Societies Thematic Priority of the European
Commission's Fifth Framework Programme (FP5). In the case of EGSO, the
application chosen was the use of Grid technology to establish a virtual
observatory for solar physics, and the project addresses the generic
problem of how to provide access to a distributed, heterogeneous data
set for a scattered user community. In order to identify observations
that match a user's search criteria, EGSO has been building an
environment that will support complex searches. Because of the absence
of the metadata needed to tie the heterogeneous data together, EGSO has
placed emphasis on the provision of databases that can be accessed from
the Internet through special providers. The provision of appropriate
metadata is of extreme importance in establishing a virtual observatory,
and the approach used can be adapted to facilitate the inclusion of
any data, including non-solar data. We report on the capabilities of
EGSO and discuss experience gained in creating the facility. We also
discuss how EGSO has been working with other virtual observatories that
support the solar, heliospheric and space plasma communities in order
to try to achieve interoperability between the numerous data sets. We
highlight what we consider are the most profitable ways of doing this.
Title: The scientific possibilities for coronagraphy from the
Solar Orbiter
Authors: Antonucci, Ester
Bibcode: 2005AdSpR..36.1367A
Altcode:
This paper briefly discusses the major open issues relative to the
understanding of the solar corona and the origin of the solar wind
in the context of the opportunities offered by the Solar Orbiter,
future mission of the European Space Agency. The Solar Orbiter mission
profile offers unique opportunities for the study of the initiation and
propagation of coronal mass ejection, of the evolution of the global
corona and its restructuring in response to the abrupt changes induced
by coronal activity, and for the assessment of the role of the coronal
magnetic topology in controlling the physical parameters of the fast
and slow wind.
Title: HERSCHEL Suborbital Program: 3-D Applications for the STEREO
Mission
Authors: Moses, J. D.; Newmark, J.; McMullin, D.; Antonucci, E.;
Fineschi, S.; Gardiol, D.; Zangrilli, L.; Romoli, M.; Pace, E.; Gori,
L.; Landini, F.; Gherardi, A.; da Deppo, V.; Naletto, G.; Nicolosi, P.;
Pelizzo, M.; Malvezzi, M.; Auchere, F.; Delaboudiniere, J.; Howard, R.
Bibcode: 2004AGUFMSH23A..08M
Altcode:
The HERSCHEL (HElium Resonance Scatter in the Corona and HELiosphere)
Suborbital Program is an international collaborative program between
a consortium of Italian Universities & Observatories led by
Dr. E. Antonucci (and funded by the Italian Space Agency, ASI), the
French IAS (funded in part by CNES) and the Solar Physics Branch of
NRL (by NASA SEC and the Office of Naval Research). HERSCHEL will:
investigate the slow and fast solar wind, determine the helium
distribution and abundance in the corona, and test solar wind
acceleration models; by obtaining simultaneous observations of
the electron, proton and helium solar coronae. HERSCHEL will also
establish proof-of-principle for the Ultra-Violet Coronagraph, which
is in the ESA Solar Orbiter Mission baseline. The HERSCHEL launch date
has been linked to the STEREO launch date to allow coordinated science
between the two missions. One aspect of this scientific coordination is
establishing the 3-D structure of the inner corona. HERSCHEL provides
a third viewpoint for the inner corona covered by the A&B STEREO
SECCHI COR-1. HERSCHEL is the only scheduled, space-based asset that
could provide this third viewpoint for the critical inner corona viewed
by STEREO COR-1 (although lower resolution, ground-based cononagraphs
will make a contribution). A third viewpoint dramatically increases
one's ability to establish the 3-D structure of an optically thin object
(e.g. the metric in Fig. 7 of Davila 1994, ApJ 423, 871). HERSCHEL will
provide at least a snapshot of that viewpoint, plus a wide range of
additional information on the H and He composition of the inner corona.
Title: Solving Science Use Cases that relate to the Sun and
Heliosphere with EGSO
Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Aboudarham,
J.; Antonucci, E.; Gurman, J. B.; Hill, F.; Pike, D.; Vial, J.;
Zharkova, V.
Bibcode: 2004AGUFMSH21B0415B
Altcode:
The European Grid of Solar Observations (EGSO) is a grid testbed
funded by the European Commission's Fifth Framework Programme under
its Information Society Technologies (IST) thematic priority. The
project started in 2002 and is designed to provide enhanced access to
solar and related data around the world. The EGSO grid is composed
of two main components, Roles to set up the grid and, catalogs and
registries to allow roles to answer users queries. Catalogs are made
of lists of observations, events and features (a new service provided
by EGSO). Registries are built from these catalogs and organized in
order to enhance search capabilities. EGSO is working closely with
other virtual observatory (VO) projects in the solar physics and
related domains. This includes the US Virtual Solar Observatory (VSO)
and the Collaborative Sun-Earth Connector (CoSEC). More recently we
have been working with the Virtual Space Plasma Observatory (VSPO) and
have contact with the Virtual Heliospheric Observatory (VHO). Through
discussions with future missions, and within the new IAU Working
Group on ``International Data Access'' (Solar and Heliospheric),
the VOs are studying ways of ensuring interoperability from the
``sun to dirt''. This type of integrated access will be particularly
important to missions such as STEREO and Living Witha Star. In this
paper we will report the current status of EGSO, demonstrate how the
catalogs and registries model serves within the user interface, and
show how the user can retrieve solar and heliospheric data to match
a scientific query. EGSO Release 4 is now being Beta-tested by users
and anyone interested should view the Web page detailing all the EGSO
capabilities under http://www.egso.org/demo
Title: SPECTRE: a spectro-heliograph for the transition region
Authors: Naletto, G.; Antonucci, E.; Fineschi, S.; da Deppo, V.;
Nicolosi, P.; Romoli, M.; Zangrilli, L.; Gardiol, D.; Loreggia, D.;
Malvezzi, M.; Howard, R.; Moses, D.
Bibcode: 2004ESASP.554..251N
Altcode: 2004icso.conf..251N
The SPECtro-heliograph for the Transition REgion (SPECTRE) experiment
is one of the instruments of the Solar Heliospheric Activity Research
and Prediction Program (SHARPP) suite initially foreseen aboard the
NASA mission Solar Dynamics Observa-tory (SDO) of the International
Living With a Star (ILWS) program. The scientific objective of the
SPECTRE experiment was to characterize the rapid evolution of plasma in
the transition region of the solar atmosphere, producing full-disk 1.2
arcsec-resolution images of the solar atmosphere at the very critical
63 nm OV spectral line, characterizing a solar plasma temperature of
about 250,000K. Unfortunately, NASA very recently and unexpectedly,
during the instrument Phase A study, decided not to proceed with the
realization of SHARPP. The authors of this paper think that all the
work done so far in the definition of SPECTRE should not be lost. So,
they have decided to summarize in this paper the main characteristics
of this instrument and the results of the analysis so far performed:
the hope is that in a next future this work can be used again for
realizing an instrument having similar characteristics.
Title: The European Grid of Solar Observations
Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Antonucci, E.;
Zharkova, V. V.; Abourdarham, J.; Pike, C. D.; EGSO Team
Bibcode: 2004AAS...204.5206B
Altcode: 2004BAAS...36R.754B
The European Grid of Solar Observations (EGSO) is a Grid test-bed funded
by the European Commission that will change the way users analyze solar
data. The project is tackling one of the major hurdles in the analysis
of solar data - identifying what data are available and retrieving those
that are needed. To do this, EGSO is creating new forms of metadata that
will speed the search process and for the first time provide the ability
to select data based on features,phenomena and events. The project
completed its second year in March 2004 and is now on Release 4 of the
code. Since the first release in September 2003, members of the solar
community have been involved in product testing. The constant testing
and feedback allows us to assure the usability of the system. We
will describe the capabilities of the latest release and discuss the
scientific problems that it is currently able to address.
Title: Spectroscopic measurement of the plasma electron density and
outflow velocity in a polar coronal hole
Authors: Antonucci, E.; Dodero, M. A.; Giordano, S.; Krishnakumar,
V.; Noci, G.
Bibcode: 2004A&A...416..749A
Altcode:
A new spectroscopic method, aimed to derive the plasma electron
density and outflow velocity in expanding solar coronal regions,
is discussed in this paper. The method is based on the analysis of a
pair of coronal lines emitted via collisional and radiative excitation
by the same ion, such as the O VI 1032, 1037 Å, doublet. The merit
of this technique consists in allowing us to derive at the same time
electron density and outflow velocity of the coronal plasma from nearby
lines detectable with the same instrument, provided the constraint
on mass flux conservation along the flow tube connecting solar corona
and heliosphere is taken into account. The results obtained from the
analysis of the OVI emission imply that the physical conditions of a
polar coronal hole plasma, observed during minimum activity, are the
following. The electron density decreases from 4× 105
cm-3 at 1.7 R⊙ to 2-4× 104
cm-3 at 3.1 R⊙, whereas the outflow velocity
of the oxygen ions is monotonically increasing to reach 350-500 km
s-1 at 3.1 R⊙, depending on the assumptions
on the degree of anisotropy of the velocity distribution of the
ions. These results of the velocity of expansion of the fast wind
confirm those obtained with Doppler dimming techniques when assuming
the lowest observed density values for the coronal hole plasma. This
implies that, for a rarified corona, the outflow velocity of the fast
solar wind in polar holes can be traced by the motion of the O VI ions
at least up to 2.4 R⊙. The analysis also shows that the
degree of anisotropy of the oxygen ions, due to the acceleration of
the ions across the magnetic field in a coronal hole, exhibits a steep
increase and that the geometry of the flow tube diverges very rapidly
low down in the inner corona/transition region. The observations
of the extended corona analysed in this paper are obtained with the
Ultraviolet Coronagraph Spectrometer of the SOHO space mission.
Title: CCD camera for ground- and space-based solar corona
observations
Authors: Gherardi, Alessandro; Gori, Luca; Focardi, Mauro; Pace,
Emanuele; Romoli, Marco; Fineschi, Silvano; Zangrilli, Luca; Gardiol,
Daniele; Antonucci, Ester
Bibcode: 2004SPIE.5171..247G
Altcode:
A new concept CCD camera is currently under development at the XUVLab
of the Department of Astronomy and Space Science of the University
of Florence. This CCD camera is the proposed detector for the space-
and ground-based solar corona observations. This camera will be the
detector for the polarimetric channels of the UVC coronagraph of
the HERSCHEL rocket mission to observe the solar corona in an optical
broadband. The ground-based application consists in a UVC prototype for
coronagraphic measurements from Earth in the visible range. Within this
project, a CCD camera with innovative features has been produced: the
camera controller allows the fine tuning of all the parameters related
to charge transfer and CCD readout, i.e., the use of virtually any CCD
sensor, and it implements the new concept of high level of versatility,
easy management, TCP/IP remote control and display.
Title: Outflow Velocities in Polar Coronal Holes
Authors: Gabriel, A. H.; Bely-Dubau, F.; Lemaire, P.; Antonucci, E.
Bibcode: 2004IAUS..219..635G
Altcode: 2003IAUS..219E.100G
It is well established that the fast solar wind originates during
the solar minimum from the polar coronal holes. The object is to
investigate this wind onset region to identify the solar structures
responsible. We report here the first measurements of outflow velocities
between 1.0 and 1.3 Ro in solar plumes using XUV spectral lines from
SUMER/SOHO and the Doppler dimming technique. In contrast to what has
been suggested by several other observers using SOHO data we conclude
that the wind velocity in plumes is greater than in the interplume
regions. This tendency diminishes with height so that it may vanish
or even reverse at greater distances. We show that one half of the
solar wind observed at 1 A.U. from Ulysses originates from the solar
plumes at 1.1 Ro. We are extending these observations to 4 Ro using the
UVCS/SOHO spectro-coronagraph to understand the connection with plumes
seen at greater distances. Initial indications suggest a change in the
physical nature of plumes around 2.0 Ro raising questions concerning
their relation to the frequently seen white-light plumes at large
distances. We explore the possible connection between polar plumes
the supergranule network and coronal heating in non-hole regions.
Title: The scientific possibilities for coronagraphy from the
Solar Orbiter
Authors: Antonucci, E.
Bibcode: 2004cosp...35.4009A
Altcode: 2004cosp.meet.4009A
The Solar Orbiter offers a unique opportunity to study the outer
corona, that is, that part of the solar corona observable only at
the limb passage. Two aspects of the mission profile are crucial in
order to achieve new insight into the physics of the solar atmosphere
via visible and ultraviolet coronagraphy: the phase characterized
by a spacecraft rotation approximately equal to that of the Sun,
and the late phase of the mission when the coronal remote sensing
is performed out of the ecliptic. During the co-rotation phase the
structures of the outer corona will appear as frozen at the limb for
several days providing for the first time the possibility to separate
the evolution from the rotation effects, thus allowing a direct study
of structures and phenomena with lifetime longer than the interval
of two-three days, corresponding to the passage of a coronal feature
at the limb. The out-of-ecliptic observations are on the other hand
providing an insight into the actual longitudinal extension of the
large-scale coronal features and events, such as streamers and coronal
mass ejections. Full comprehension of the large-scale, medium-term
evolution of the corona can be then achieved by observing from the
Solar Orbiter the outer layers of the solar atmosphere both in visible
light, providing information on the density structure of the corona,
and in ultraviolet light, providing information on the expansion of
the atmosphere, via Doppler dimming.
Title: A white light coronagraph for the SDO mission
Authors: Frassetto, F.; Naletto, G.; Nicolosi, P.; Antonucci, E.;
Fineschi, S.
Bibcode: 2004cosp...35.4390F
Altcode: 2004cosp.meet.4390F
The Solar Dynamic Observatory is the first mission planned within the
International Living with a Star ESA/NASA program. We have proposed for
this mission a standard heritage visible light coronagraph, and here
we describe this instrument. The main features of this coronagraph,
whose design is based on the classical externally occulted Lyot optical
configuration, are a field of view ranging from 2 and 15 solar radii,
an angular resolution of 14 arcsec (per pixel), a spectral bandpass
from 650 nm to 750 nm, and an instrument speed of about f/6. With
this instrument will be possible to study the evolutions of typical
solar phenomena like coronal mass ejections with a improved temporal
resolution and angular coverage.
Title: Spectroscopic Results with the Ultraviolet Coronagraph
Spectrometer on the Solar and Heliospheric Observatory
Authors: Antonucci, E.; Abbo, L.
Bibcode: 2004MSAIS...5...26A
Altcode:
Recent results, based on the analysis of the ultraviolet coronal
emission during the years of minimum solar activity 1996 and 1997, have
allowed the identification of the sources of the slow solar wind. The
data are obtained with the Ultraviolet Coronagraph Spectrometer (UVCS)
on board the Solar and Heliospheric Observatory (SOHO). The results
have been derived by adopting a new diagnostic method based on the
spectroscopic analysis of the O VI 1032, 1038 Å, lines, that we have
developed in order to infer the relevant parameters of the coronal
plasma. This diagnostics fully accounts for the expansion factor of the
magnetic field lines in the regions where the solar corona expands. The
coronal layer studied is in the range from 1.5 and 3.5 solar radii. The
physical conditions of the plasma flowing along the open field lines
with origin in the core and at the edges of coronal holes are compared
with the plasma in the closed magnetic field line regions characterizing
streamers and close to the heliospheric current sheet. There is evidence
for two regions where the slow coronal wind is observed: the edges
of the large polar coronal holes characterizing solar minimum and
the region along the streamer axis at heights above 2.7 solar radii,
where the heliospheric current sheet forms. This conclusion and the
fact that the fast wind is originating in the core of coronal holes,
as shown in previous papers, suggest that the plasma conditions, in
particular the outflow velocity and the preferential heating across
the magnetic field, are related to the magnetic topology, namely,
to the expansion factor of the flux tubes that changes from the edge
to the core of coronal holes. The present results also indicate that
also the degree of energy dissipation in the open field region might
be related to and regulated by the local magnetic topology.
Title: Spectral observations of the solar wind
Authors: Antonucci, E.
Bibcode: 2004cosp...35.4006A
Altcode: 2004cosp.meet.4006A
The Ultraviolet Coronagraph Spectrometer, operating on the space
solar observatory SOHO, detects the ultraviolet lines emitted from
the chromosphere and transition region and resonantly scattered in the
outer corona. The spectroscopy of the resonantly scattered light allows
a complete diagnosis of the coronal plasma. On the basis of the most
intense ultraviolet coronal lines, such as the HI Ly alpha line 1216 and
the OVI doublet, 1032, 1037, it is possible to determine at the same
time the expansion rate of the coronal plasma, via Doppler dimming,
the velocity distribution and abundance of hydrogen and oxygen ions,
and the electron density. The resulting detailed description of the
physical conditions of the outer corona allows the identification of
the regions of acceleration of the fast and slow wind as well as of
the signatures of the processes responsible for the wind acceleration.
Title: The ultraviolet spectroscopy and the sources of the slow
solar wind
Authors: Abbo, L.; Antonucci, E.
Bibcode: 2004cosp...35.1875A
Altcode: 2004cosp.meet.1875A
We analyze the physical conditions of streamers observed at high
spectral resolution during the minimum of solar cycle 23 with the
Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO, on the
basis of a new ultraviolet spectroscopic diagnostic able to derive the
coronal electron density and the oxygen abundance as a function of the
outflow velocity. In order to investigate the coronal sources of the
slow wind, the plasma parameters in the extended corona are inferred
from the spectroscopic analysis of the O VI doublet 1032, 1038 Å,
and H I Lyα emission lines, which accounts for the coronal magnetic
topology to constrain the mass flux along the flow tube connecting the
coronal regions to the heliosphere. The coronal sources and acceleration
regions of the slow wind during the minimum of solar activity result
to be the regions adjacent to the streamer boundaries.
Title: Integrated Access to Solar Data using EGSO
Authors: Bentley, R. D.; Csillaghy, A.; Scholl, I.; Vial, J. -C.;
Aboudarham, J.; Antonucci, E.; Zharkova, V. V.; Pike, C. D.
Bibcode: 2004cosp...35.3935B
Altcode: 2004cosp.meet.3935B
The European Grid of Solar Observations (EGSO) is a virtual observatory
based on Grid technology that will change the way users analyze solar
data. EGSO is funded under the IST (Information Society Technologies)
thematic priority of the European Commission's Fifth Framework Programme
(FP5). It started in March 2002 and will last for 3 years. The EGSO
Consortium comprises eleven groups from five countries in Europe
and the US, and is led by the Mullard Space Science Laboratory
of University College London. The project aims to overcome one of
the major hurdles in the analysis of solar data - finding what data
are available and retrieving those that are needed. EGSO is creating
layers of metadata catalogues that will for the first time provide the
ability to select solar data based on phenomena and events. It is also
integrating access to solar data by building a Grid including solar
archives around the world. This combination of metadata and tools for
selecting, processing and retrieving distributed and heterogeneous
solar data, will radically change the way that data are distributed
and analyzed. EGSO is collaborating closely with groups in the US who
are working on similar virtual observatory projects for the solar,
solar-terrestrial and heliospheric communities with the objective
of providing integrated access to these data. In particular, strong
synergies between the EGSO and CoSEC projects are producing innovative
ways of accessing the data that will be deployed in both projects. Since
the first release of EGSO in September 2003, members of the solar
community have been involved in product testing. The constant testing
and feedback allows us to continue to improve the quality and usability
of the system. The capabilities of the latest release (R4) will be
described, and the scientific problems that it addresses discussed.
Title: Investigation of the sources of the slow solar wind
Authors: Abbo, Lucia; Antonucci, Ester; Dodero, Maria Adele; Benna,
Carlo
Bibcode: 2003AIPC..679..238A
Altcode:
Aim of this analysis is to study the variation of the physical
conditions of the coronal plasma across the streamer boundary in order
to identify the coronal sources of the slow solar wind during the
minimum of solar activity. The analysis is based on the observations
of equatorial streamers, obtained in the outer corona during the
years 1996 and 1997 with the Ultraviolet Coronagraph Spectrometer
(UVCS) onboard SOHO. The outflow velocity, the electron density and
the oxygen abundance relative to hydrogen of the coronal plasma have
been determined, in the range between 1.6 and 3.5 solar radii (Rsolar),
by means of a spectroscopic analysis of the OVI 1032, 1037 Å and the
HI Lyα 1216 Å lines. Coronal expansion at low velocity, in the range
80-100 km/s, is observed along regions 15°-20° wide, surrounding the
streamer boundary. Evidence for coronal plasma outflows at low velocity
is also found further out in the region along the streamer axis. In
this case the outflows become significant beyond 2.7 Rsolar. Hence,
the slow solar wind during solar minimum flows just outside the denser
and brighter zone of a streamer, characterized by closed magnetic
field lines and in a lane around the heliospheric current sheet,
forming just above the closed field line region.
Title: The Ultraviolet and Visible-light Coronagraph of the HERSCHEL
experiment
Authors: Romoli, M.; Antonucci, E.; Fineschi, S.; Gardiol, D.;
Zangrilli, L.; Malvezzi, M. A.; Pace, E.; Gori, L.; Landini, F.;
Gherardi, A.; da Deppo, V.; Naletto, G.; Nicolosi, P.; Pelizzo, M. G.;
Moses, J. D.; Newmark, J.; Howard, R.; Auchere, F.; Delaboudinière,
J. P.
Bibcode: 2003AIPC..679..846R
Altcode:
The Herschel (HElium Resonant Scattering in the Corona and HELiosphere)
experiment, to be flown on a sounding rocket, will investigate the
helium coronal abundance and the solar wind acceleration from a
range of solar source structures by obtaining the first simultaneous
observations of the electron, proton and helium solar corona. The
HERSCHEL payload consists of the EUV Imaging Telescope (EIT), that
resembles the SOHO/EIT instrument, and the Ultraviolet and Visible
Coronagraph (UVC).UVC is an imaging coronagraph that will image
the solar corona from 1.4 to 4 solar radii in the EUV lines of HI
121.6 nm and the HeII 30.4 nm and in the visible broadband polarized
brightness. The UVC coronagraph is externally occulted with a novel
design as far as the stray light rejection is concerned. Therefore,
HERSCHEL will also establish proof-of-principle for the Ultraviolet
Coronagraph, which is in the ESA Solar Orbiter Mission baseline.The
scientific objectives of the experiment will be discussed, togetherwith
a description of the UVC coronagraph.
Title: Simulation of Coronal Hole-Associated Neutral Solar Wind as
Expected at the Solar Orbiter Position
Authors: D'Amicis, R.; Hilchenbach, M.; Orsini, S.; Antonucci, E.;
Bruno, R.; Milillo, A.; Fineschi, S.; di Lellis, A. M.; Massetti, S.
Bibcode: 2003EAEJA....10167D
Altcode:
Neutral atoms are closely coupled to the emerging solar wind plasma
in the solar corona. After escaping from this region, where the solar
wind plasma experiences several acceleration processes, beyond 3
solar radii the neutral atoms become more and more decoupled from the
plasma. Therefore, the neutral atoms may be considered as an in-situ
trace particle population flowing within the solar wind plasma,
since they allow the information of the acceleration regions to be
reconstructed by remote detection from any vantage point. Hence,
the actual neutral solar wind (NSW) detection allows estimates of
the emerging solar wind density, bulk velocity, temperature, and
anisotropy. In the present study, we simulate the NSW distribution
as expected at the Solar Orbiter position, considering the major
parameters of a coronal-hole emerging solar wind as estimated by the
SOHO UVCS experiment.
Title: Ultraviolet and Visible-light Coronagraphic Imager (UVCI)
Authors: Fineschi, Silvano; Antonucci, Ester; Romoli, Marco; Gardiol,
Daniele; Naletto, Giampiero; Giordano, Silvio; Malvezzi, Marco;
Da Deppo, Vania; Zangrilli, Luca; Noci, Giancarlo
Bibcode: 2003SPIE.4853..162F
Altcode:
The HERSCHEL (HElium Resonance Scattering in the Corona and HELiosphere)
Sun-Earth Sub-Orbital Program is a proposed sounding-rocket payload
designed to investigate helium coronal abundance and solar wind
acceleration from a range of solar source structures by obtaining
simultaneous observations of the electron, proton and helium solar
coronae. HERSCHEL will provide the first measurements of the coronal
helium abundance in source regions of the solar wind, thus bringing
key elements to our understanding of the Sun-Earth connections. The
HERSCHEL instrument package consists of the Extreme Ultraviolet Imaging
Telescope (EIT) for on-disk coronal observations and the Ultraviolet and
Visible-light Coronagraphic Imager (UVCI) for off-limb observations of
the corona. The UVCI is an externally occulted, reflecting coronagraph
with an off-axis Gregorian telescope. UVCI will be able to take coronal
images at heliocentric heights comprised between 1.2 to 3.5 solar radii
of a) K-corona polarized brightness (pB); b) H I Lyman-α, 121.6 nm,
line-emission; c) He II Lyman-α, 30.4 nm, line. The key element in the
UVCI instrument concept is that the mirrors with multilayer coatings
optimized for 30.4 nm still have good reflectivity at 121.6 nm and
in the visible. The optical design concept for the UVCI instrument
will be discussed, together with its expected optical and throughput
performances.
Title: Italian Space Solar Physics Programs within the International
Living with a Star Initiative
Authors: Antonucci, E.
Bibcode: 2003MSAIS...3..316A
Altcode:
The program `International Living with a Star (ILWS)' is finalized
to study the physical processes that are governing the Sun-Earth
system as an integrated entity and to perform simultaneous and
coordinated observations in the following fields: solar, heliospheric,
magnetospheric sciences, space weather and global climatology. The
main thrust is indeed on the understanding of solar variability and
its effects on the Sun-Earth system.
Title: Imaging Stokes polarimeter based on liquid crystals for the
study of the K-solar corona
Authors: Zangrilli, L.; Fineschi, S.; Loreggia, D.; Gardiol, D.;
Antonucci, E.; Cora, A.
Bibcode: 2003MmSAI..74..528Z
Altcode:
We describe the project of an imaging Stokes polarimeter based on
liquid crystals, for the study of the K-solar corona. Liquid crystals
retarders are electrically variable waveplates. The change of the
retardance, induced by a variable applied voltage, is a function of
the wavelength. As observations of the visible coronal continuum are
usually made over the band 450-600 nm, we are interested in studying
the properties of these retarders as a function of the wavelength. This
polarimeter is thought to be implemented on ground-based and space-borne
coronagraphs.
Title: SOHO Long-term ARchive: Information Retrieval Approach
Authors: Cora, A.; Antonucci, E.; Dimitoglou, G.; Volpicelli, C. A.;
Giordano, S.
Bibcode: 2003MmSAI..74..819C
Altcode:
The SOho Long-term ARchive (SOLAR) is one of the three European
data archives of the SOlar and Heliospheric Observatory (SOHO)
instruments. The SOHO archives adopt the Internet and the World Wide Web
(WWW) as the platform to search, retrieve and disseminate science data
and mission information. This paper presents the architecture and design
overview of the archive built at the Turin Astronomical Observatory and
a brief description of the available web-based Graphical User Interfaces
developed to have access to the data remotely. SOLAR is foreseen to be
operational not only during the SOHO mission (recently extended to 2007)
but also for a 10-year period following the mission end (2007-2017).
Title: UVCI for HERSCHEL: instrument description and activity
status report
Authors: Gardiol, D.; Romoli, M.; Landini, F.; Naletto, G.; Da Deppo,
V.; Malvezzi, M.; Apollonio, P.; Duchini, G.; Rusconi, E.; Santori,
A.; Antonucci, E.; Fineschi, S.; Loreggia, D.; Zangrilli, L.; Gori,
L.; Nicolosi, P.; Pelizzo, M. G.
Bibcode: 2003MmSAI..74..839G
Altcode:
The Ultraviolet and Visible light Coronagraphic Imager (UVCI) is an
imaging coronagraph that will take pictures of the solar corona from 1.4
up to 3.5 solar radii at three different wavelengths, HI Ly-alpha 121.6
nm, HeII Ly-alpha 30.4 nm, and broadband visible polarized light. It
is part of the HERSCHEL experiment (HElium Resonant Scattering in the
Corona and HELiosphere) and it will fly on a sounding rocket. The
instrument optical design consists of two twin off-axis Gregorian
externally occulted telescopes, with multilayer-coated optics optimised
respectively for the HI and HeII lines.\ We describe the instrument
structure design and the associated optical tolerances analysis. The
structure is conceived to attain high stiffness with the lowest possible
weight. Tolerances on the positioning of the optical elements, for
alignment purpose, have been evaluated through a geometrical approach
and ray-tracing method.
Title: The Italian solar data archives: national and European
perspectives
Authors: Messerotti, M.; Coretti, I.; Padovan, S.; Zlobec, P.;
Antonucci, E.; Cora, A.; Volpicelli, C. A.; Dimitoglou, G.; Reardon,
K.; Tripicchio, A.; Severino, G.; EGSO Team
Bibcode: 2003MmSAI..74..391M
Altcode:
We discuss the present status of the solar data archives geographically
distributed in the Italian Astronomical Observatories of the National
Institute for Astrophysics (INAF). In particular, we describe the
national project SOLARNET (SOLAR NETwork) aimed at federating all the
Italian solar archives as a distributed database, the first step toward
an Italian Virtual Solar Observatory (IVSO), and the European Grid
for Solar Observations (EGSO) project, which is under implementation
to construct the basis for a large solar archive federation based on
the Grid architecture to provide the scientific user with advanced
resources such as a solar feature catalogue.
Title: Acceleration region of the slow solar wind in corona
Authors: Abbo, L.; Antonucci, E.; Mikić, Z.; Riley, P.; Dodero,
M. A.; Giordano, S.
Bibcode: 2003MmSAI..74..733A
Altcode:
We present the results of a study concerning the physical parameters of
the plasma of the extended corona in the low-latitude and equatorial
regions, in order to investigate the sources of the slow solar wind
during the minimum of solar activity. The equatorial streamer belt has
been observed with the Ultraviolet Coronagraph Spectrometer (UVCS)
onboard SOHO from August 19 to September 1, 1996. The spectroscopic
diagnostic technique applied in this study, based on the OVI 1032,
1037 Ålines, allows us to determine both the solar wind velocity and
the electron density of the extended corona. The main result of the
analysis is the identification of the acceleration region of the slow
wind, whose outflow velocity is measured in the range from 1.7 up to
3.5 solar radii.
Title: SOHO Long-term ARchive (SOLAR)
Authors: Cora, A.; Volpicelli, C. A.; Antonucci, E.; Dimitoglou, G.
Bibcode: 2003MmSAI..74..462C
Altcode:
The SOHO Long-term Archive (SOLAR) is one of the three European
archives for the Solar and Heliospheric Observatory (SOHO) ESA/NASA
data. SOLAR is foreseen to be operational during the SOHO mission
(recently extended to 2007) and for a 10-year period following the
mission end (2007-2017). This paper presents an architectural overview
of the archive implemented at the Astronomical Observatory of Turin,
and gives a brief description of the web-based Graphical User Interface
used to remotely access the data.
Title: EGSO - The European Grid of Solar Observations
Authors: Reardon, K.; Antonucci, E.; Giordano, S.; Severino, G.;
Messerotti, M.; EGSO Team
Bibcode: 2003MmSAI..74..823R
Altcode:
The European Grid of Solar Observations (EGSO) project aims to
produce the framework for a coordinated community-wide resource for
obtaining and reducing solar observations. The EGSO will be capable of
sharing resources coming from all types of providers, while ensuring
scalability, security, and compatibility among all datasets. The user
will be provided with a customizable search interface from which to
simultaneously browse or data mine a range of solar and heliospheric
data archives. In essence, the EGSO will create the fabric of a virtual
solar observatory.
Title: MAGRITTE / SPECTRE : the Solar Atmospheric Imaging Assembly
(AIA) aboard the Solar Dynamics Observatory
Authors: Rochus, P.; Defise, J. M.; Halain, J. P.; Mazy, E.; Jamar, C.;
Clette, F.; Cugnon, P.; Berghmans, D.; Hochedez, J. F.; Delaboudiniere,
J. P.; Artzner, G.; Auchere, F.; Mercier, R.; Ravet, M. F.; Delmotte,
M.; Idir, M.; Fineschi, S.; Antonucci, E.; Harrison, R. A.; Howard,
R. A.; Moses, J. D.; Newmark, J. S.
Bibcode: 2002AGUFMSH21C..05R
Altcode:
The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar
Dynamics Observatory will characterize the dynamical evolution of
the solar plasma from the chromosphere to the corona, and will follow
the connection of plasma dynamics with magnetic activity throughout
the solar atmosphere. The AIA consists of 7 high resolution imaging
telescopes in the following spectral bandpasses: 1215 \x8F Ly-a, 304
\x8F He II, 629 \x8F OV, 465 \x8F Ne VII, 195 \x8F Fe XII (includes Fe
XXIV), 284 \x8F Fe XV, and 335 \x8F Fe XVI. The telescopes are grouped
by instrumental approach: the Magritte Filtergraphs (R. Magritte,
famous 20th Century Belgian Surrealistic Artist), five multilayer EUV
channels with bandpasses ranging from 195 to 1216 \x8F, and the SPECTRE
Spectroheliograph with one soft-EUV channel at OV 629 \x8F. They will
be simultaneously operated with a 10-second imaging cadence. These two
instruments, the electronic boxes and two redundant Guide Telescopes
(GT) constitute the AIA suite. They will be mounted and coaligned on a
dedicated common optical bench. The GTs will provide pointing jitter
information to the whole SHARPP assembly. This poster presents the
selected technologies, the different challenges, the trade-offs to be
made in phase A, and the model philosophy. From a scientific viewpoint,
the unique combination high temporal and spatial resolutions with the
simultaneous multi-channel capability will allow Magritte/SPECTRE
to explore new domains in the dynamics of the solar atmosphere, in
particular the fast small-scale phenomena. We show how the spectral
channels of the different instruments were derived to fulfill the
AIA scientific objectives, and we outline how this imager array will
address key science issues, like the transition region and coronal waves
or flare precursors, in coordination with other SDO experiments. We
finally describe the real-time solar monitoring products that will be
made available for space-weather forecasting applications.
Title: EGSO in need for a global schema
Authors: Hill, Frank; Csillaghy, Andre; Bentley, Robert D.; Aboudarham,
Jean; Antonucci, Ester; Finkelstein, Anthony; Ciminiera, Luigi;
Gurman, Joseph B.; Scholl, Isabelle; Pike, Dave; Zharkova, Valentin
Bibcode: 2002SPIE.4846...35H
Altcode:
The European Grid of Solar Observations (EGSO) is a project to develop
a virtual observatory for the solar physics community. Like in all
such projects, a vital component is a schema that adequately describes
the data in the distributed data sets. Here, we discuss the schema in
general terms, and present a draft example of a portion of a possible
XML schema.
Title: The streamer boundary and the source of the slow wind
Authors: Abbo, Lucia; Antonucci, Ester
Bibcode: 2002ESASP.508..477A
Altcode: 2002soho...11..477A
The source of the slow solar wind that dominates the low latitude
heliosphere during the minimum of solar activity has not yet been fully
identified. We present preliminary results of a study concerning the
streamer boundary regions in order to investigate the streamer-wind
transition in the extended corona. The coronal plasma physical
conditions, such as kinetic temperature of ions, electron density,
abundance of oxygen and outflow velocity, are determined across the
boundary of streamers. The study, based on data obtained with the
Ultraviolet Coronagraph Spectrometers (UVCS) onboard SOHO, concern
streamers observed at mid-low latitudes in the years 1996 and 1997,
during the recent solar minimum. The analysis is based on ad-hoc
diagnostic techniques developed to obtain the solar wind velocity,
the electron density and the oxygen abundance of the extended corona,
based on the O VI 1032, 1037 Å and the H I Ly&alpha 1216 Å lines.
Title: HElium Resonance Scattering in the Corona and HELiosphere
(HERSCHEL)
Authors: Moses, J. D.; Newmark, J.; Howard, R.; Auchere, F.; Antonucci,
E.; Fineschi, S.; Romoli, M.
Bibcode: 2002AGUSMSH21B..03M
Altcode:
The proposed HERSCHEL (HElium Resonance Scattering in the Corona and
HELiosphere) program will investigate coronal heating and solar wind
acceleration from a range of solar source structures by obtaining
simultaneous observations of the electron, proton and helium solar
coronae. The HERSCHEL will establish proof-of-principle for the
Ultra-Violet Coronagraph (UVC), which is in the ESA Solar Orbiter
Mission baseline. The NRL Solar Physics Branch is joining with the
Italian UVC Consortium to address the objectives of the International
Living With a Star program with this combination of NASA suborbital
program and ESA Solar Orbiter flight opportunities. Indeed, while
the Solar Orbiter flight is still many years away, the 3 year program
being proposed here is essential in order to prove the validity of this
exciting new concept before the Solar Orbiter instrument selection is
finalized. This proposal aims to develop instrumentation that for the
first time will directly image and characterize on a global coronal
scale the two must abundant elements, hydrogen and helium. This will
directly address three outstanding questions in the Sun-Earth Connection
theme: 1) Origin of the slow solar wind, 2) Acceleration mechanisms of
the fast solar wind, and 3) Variation of Helium abundance in coronal
structures. Additionally, by establishing proof of concept for the
UVC on Solar Orbiter, this will facilitate future investigations
of CME's kinematics, and solar cycle evolution of the electron,
proton, and helium coronae. Lastly, this mission fits the goals of
the International Living With a Star (ILWS) program. This work has
been supported by the Office of Naval Research.
Title: Coronal hole-streamer interface in the extended corona
Authors: Abbo, L.; Antonucci, E.
Bibcode: 2002ESASP.477..323A
Altcode: 2002scsw.conf..323A
Coronal holes are known to be the source of the fast, relatively
homogeneous solar wind. A more variable slow solar wind emerges from the
corona adjacent to these fast streams and dominates the low latitude
heliosphere during the minimum of solar activity. The objective of
this paper is the study of the coronal hole-streamer interface and
of the physical conditions (i.e. kinetic temperature of oxygen ions,
abundance of oxygen, outflow velocity) inside and at the boundary
of a streamer, in order to investigate the source of the slow solar
wind. The data used in the analysis are obtained with the Ultraviolet
Coronagraph Spectrometer (UVCS) onboard SOHO and concern streamers at
mid-low latitudes observed in 1996, during the solar minimum.
Title: Solar orbiter, a high-resolution mission to the sun and
inner heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Langevin, Y.; Marsden, R.; Pace, O.; Schwenn,
R.; Vial, J. -C.
Bibcode: 2002AdSpR..29.2027M
Altcode:
The scientific rationale of the Solar Orbiter is to provide, at high
spatial (35 km pixel size) and temporal resolution, observations of the
solar atmosphere and unexplored inner heliosphere. Novel observations
will be made in the almost heliosynchronous segments of the orbits at
heliocentric distances near 45 R⊙ and out of the ecliptic plane at
the highest heliographic latitudes of 30° - 38°. The Solar Orbiter
will achieve its wide-ranging aims with a suite of sophisticated
instruments through an innovative design of the orbit. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. Over extended periods
the Solar Orbiter will deliver the first images of the polar regions
and the side of the Sun invisible from the Earth.
Title: Solar Orbiter: a high-resolution mission to the sun and
inner heliosphere
Authors: Fleck, Bernhard; Marsch, E.; Antonucci, Ester; Bochsler,
Peter A.; Bougeret, J. L.; Harrison, R.; Marsden, R. P.; Coradini,
M.; Pace, Oscar; Schwenn, Rainer; Vial, Jean-Claude
Bibcode: 2001SPIE.4498....1F
Altcode:
The key mission objective of the Solar Orbiter is to study the Sun
from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar
rotation in order to examine the solar surface and the space above from
a co-rotating vantage point at high spatial resolution. Solar Orbiter
will also provide images of the Sun's polar regions from heliographic
latitudes as high as 38 degrees. The strawman payload encompasses
two instrument packages: Solar remote-sensing instruments: EUV
full-sun and high resolution imager, high-resolution EUV spectrometer,
high-resolution and full-sun visible light telescope and magnetograph,
EUV and visible-light coronagraphs, radiometers. Heliospheric
instruments: solar wind analyzer, radio and plasma wave analyzer,
magnetometer, energetic particle detectors, interplanetary dust
detector, neutral particle detector, solar neutron detector. To
reach its novel orbit, Solar Orbiter will make use of low-thrust
solar electric propulsion (SEP) interleaved by Earth and Venus gravity
assists. Solar Orbiter was selected by ESA's Science Programme Committee
(SPC) in October 2000 as a Flexi-mission, to be implemented after the
BepiColombo cornerstone mission to Mercury before 2013. This paper
summarizes the science to be addressed with the Solar Orbiter, followed
by brief descriptions of the strawman payload, the mission profile,
and the spacecraft and ground segment designs.
Title: Stray light evaluation of the Ultraviolet and Visible-light
Coronagraph Imager (UVCI) rocket prototype
Authors: Romoli, Marco; Landini, Federico; Fineschi, Silvano; Gardiol,
Daniele; Naletto, Giampiero; Malvezzi, Marco; Tondello, Giuseppe;
Noci, Giancarlo C.; Antonucci, Ester
Bibcode: 2001SPIE.4498...27R
Altcode:
The Ultraviolet and Visible-light Coronagraph Imager (UVCI) proposed
for the European Space Agency (ESA) Solar Orbiter mission, is designed
to image the visible and the ultraviolet coronal emissions, in order to
diagnose the solar corona. The UVCI is an externally occulted reflection
coronagraph that obtains monochromatic images in the neutral hydrogen
HI 121.6 nm and in the single ionized helium HeII 30.4 nm lines, and
measures the polarized brightness (pB) of the K-corona in broadband
visible light. One of the most stringent requirements in the design
of a coronagraph is the stray light rejection. The stray light is
produced by solar disk radiation which is several order of magnitude
brighter than the coronal radiation in both visible and UV. The solar
disk radiation enters the instrument through the external aperture and
stray light is produced by diffraction off the edges of the apertures
and of the optical components, non-specular reflections off the mirror
surfaces, and scattering off the mechanical structure. In this paper,
the features in the optical design that contribute to the stray light
reduction are described, and an analysis of all possible stray light
contributions is performed on the optical configuration of the UVCI
sounding rocket prototype (UVC-SR). From this analysis, a stray light
model has been developed and its results are compared with the minimum
measurable signal expected from the solar corona.
Title: Oxygen abundance in the extended corona at solar minimum
Authors: Antonucci, Ester; Giordano, Silvio
Bibcode: 2001AIPC..598...77A
Altcode: 2001sgc..conf...77A
We present a study on the abundance of oxygen relative to hydrogen
in the solar minimum corona and for the first time we measure this
quantity in polar coronal holes. The results are derived from the
observations of the extended corona obtained with the Ultraviolet
Coronagraph Spectrometer (UVCS) on SOHO. The diagnostic method used
to obtain the oxygen abundance is based on the resonant components
of the O VI 1032 Å and HI 1216 Å emission lines. This method fully
accounts for the effects of the outflow velocity of the solar wind,
which can be determined through Doppler dimming, and of the width of
the absorbing profiles of the coronal ions or neutral atoms involved in
resonant scattering. The oxygen abundance is higher in the polar coronal
hole regions, where the fast wind is accelerated, than in the streamer
belt. In the polar regions the observed oxygen abundance is consistent
with the photospheric value and with the composition results obtained
with Ulysses for the fast wind. The oxygen abundance values derived
with UVCS suggest that the plasma remains substantially contained in
quiescent streamers, that therefore do not contribute significantly
to the solar wind. .
Title: Coronal and solar wind elemental abundances
Authors: Raymond, J. C.; Mazur, J. E.; Allegrini, F.; Antonucci, E.;
Del Zanna, G.; Giordano, S.; Ho, G.; Ko, Y. -K.; Landi, E.; Lazarus,
A.; Parenti, S.; Poletto, G.; Reinard, A.; Rodriguez-Pacheco, J.;
Teriaca, L.; Wurz, P.; Zangrilli, L.
Bibcode: 2001AIPC..598...49R
Altcode: 2001sgc..conf...49R
Coronal elemental abundances, as compared with abundances in the solar
wind and solar energetic particles, provide the means for connecting
solar wind gas with its coronal source. Comparison of coronal abundances
with photospheric values shows fractionation with the ionization
potential of the atom, providing important, though not yet fully
understood, information about the exchange of material between corona
and chromosphere. Fractionation due to gravitational settling provides
clues about flows within the corona. In this paper, we discuss the
uncertainties of abundance determinations with spectroscopic techniques
and in situ measurements, we survey the ranges of abundance variations
in both the corona and solar wind, and we discuss the progress in
correlating solar wind features with their coronal sources. .
Title: Solar Orbiter, a high-resolution mission to the Sun and
inner heliosphere
Authors: Marsch, E.; Harrison, R.; Pace, O.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Fleck, B.; Langevin, Y.; Marsden, R.; Schwenn,
R.; Vial, J. -C.
Bibcode: 2001ESASP.493D..11M
Altcode: 2001sefs.workD..11M
Solar Orbiter will provide, at very high spatial (35 km pixel size)
and temporal resolution, novel observations of the solar atmosphere
and unexplored inner heliosphere. It will achieve its wide-ranging
scientific aims with a suite of sophisticated instruments through an
innovative orbit design. Unprecedented observations will be made in
the heliosynchronous segments of the orbits at heliocentric distances
near 45 Rsolar and out of the ecliptic plane at the highest
heliographic latitudes of 30° - 38°. The first near-Sun interplanetary
measurements together with concurrent remote-sensing observations of
the Sun and its corona will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in the source regions on the Sun. Solar Orbiter will deliver
the first images of the polar regions and the far side of the Sun
invisible from the Earth.
Title: Extended UV corona imaging from the Solar Orbiter: the
Ultraviolet and Visible-light Coronagraph (UVC)
Authors: Fineschi, Silvano; Antonucci, Ester; Gardiol, Daniele; da
Deppo, Vania; Naletto, Giampiero; Romoli, Marco; Cacciani, Alessandro;
Malvezzi, Marco
Bibcode: 2001ESASP.493..217F
Altcode: 2001sefs.work..217F
No abstract at ADS
Title: Coronagraph instrumentation - report of Payload Splinter
Group 2
Authors: Antonucci, Ester
Bibcode: 2001ESASP.493..145A
Altcode: 2001sefs.work..145A
This brief report gives an account of the main points discussed during
the Payload Splinter Group meetings dedicated to the coronagraphic
instrumentation on the Solar Orbiter. In particular this report
presents the main scientific goals that can be achieved through a
combination of ultraviolet and visible light coronagraphy by taking
advantage of the unique characteristics of the Solar Orbiter mission,
the observations and the instrumentation required to reach these goals,
the complementarity of the coronagraphic instrumentation to the other
remote-sensing and in situ Solar Orbiter instruments and to the other
space programs foreseen when the Orbiter will operate.
Title: The Sun's global corona in 3D
Authors: Antonucci, Ester
Bibcode: 2001ESASP.493...43A
Altcode: 2001sefs.work...43A
The Solar Orbiter will perform the first out-of-ecliptic and the first
heliosynchronous observations of the solar corona, thus allowing unique
science investigations. Co-rotation will freeze for many days the corona
in the plane of the sky, and this will ensure the most favourable
conditions to investigate the evolution of coronal structures. For
instance, the study of the evolution of coronal streamers is essential
to determining the role of magnetic reconnection as one of the possible
processes leading to the formation of the slow wind. On the other hand,
the study of the evolution of elemental compositon in streamers will
provide insight in the processes of gravitational settling and dynamic
fractionation that may occur within a streamer. The out-of-ecliptic
observations will allow for the first time a unique view of the
low-latitude and equatorial coronal plasma and solar wind. These
observations are essential to measuring the longitudinal extent of
streamers and mass ejections and to determining the mass and magnetic
flux carried by plasmoids and eruptions in the heliosphere.
Title: Coronal hole boundaries from the Sun to the Heliosphere:
Constraints on the sources and structure of the solar wind
Authors: Zurbuchen, T. H.; Von Steiger, R.; Riley, P.; Raymond, J.;
Geiss, J.; Antonucci, E.; Abbo, L.
Bibcode: 2001AGUSM..SH21B06Z
Altcode:
Coronal holes are known to be a source of fast, relatively homogenous
solar wind. A more variable slow solar wind emerges from the corona
adjacent to these fast streams and dominates the low latitude
heliosphere. The relation between these two qualitatively different
solar wind types is best studied by investigating in detail the
structure and evolution of the coronal hole boundaries from the
low atmosphere of the Sun, through the corona and into the deep
heliosphere. We present a comprehensive data-study combining data from
He I 10830A, EIT, UVCS and in situ plasma and composition measurements
from SWICS on Ulysses and ACE. First, the location and structure of the
coronal hole boundary is determined in each of the remote data-sets. We
then project the in situ plasma and composition measurements to 30
Rs using a sophisticated 2D MHD tracing technique. This technique
then allows a direct comparison of solar and in situ coronal hole
boundaries. We particularly concentrate on UVCS and SWICS data of heavy
ions in the solar wind that allow the most rigorous comparisons of solar
and in situ data, using the same measurement in the corona as in the
solar wind. We will then discuss these data in the context of models
and theories of the structure of the three-dimensional structure of
the corona and the solar wind. We will also compare the observations
with an 3D MHD calculation that predicts super-radial expansion of the
fast solar wind associated with coronal holes. This paper is a report
of an ISSI International Team on coronal hole boundaries.
Title: Oxygen abundance in coronal streamers during solar minimum
Authors: Marocchi, D.; Antonucci, E.; Giordano, S.
Bibcode: 2001AnGeo..19..135M
Altcode:
We present a study of the oxygen abundance relative to hydrogen in
the equatorial streamer belt of the solar corona during the recent
period of activity minimum. The oxygen abundance is derived from
the spectroscopic observations of the outer corona performed during
1996 with the Ultraviolet Coronagraph Spectrometer (SOHO) in the
ultra-violet region. This study shows that the depletion of oxygen, by
almost one order of magnitude with respect to the photospheric values,
found in the inner part of streamers by Raymond et al. (1997a) is a
common feature of the solar minimum streamer belt, which exhibits an
abundance structure with the following characteristics. In the core
of streamers the oxygen abundance is 1.3 × 10-4 at 1.5 R
Title: Solar Orbiter, a High-Resolution Mission to the Sun and
Inner Heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Marsden, R.; Schwenn, R.; Vial, J. -C.
Bibcode: 2001IAUS..203..565M
Altcode:
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rodot and
out-of-ecliptic at the highest heliographic latitudes of 38 degrees. The
SO will achieve its many and varied aims with a suite of small and
innovative instruments through a clever choice of orbits. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind and
energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. The SO will, during
the high-latitude orbital passes, provide the first observations of
the Sun's polar regions as seen from outside the ecliptic and also
measure the magnetic field at the poles.
Title: Ultraviolet and visible-light coronagraph for the Solar
Orbiter mission
Authors: Antonucci, Ester; Fineschi, Silvano; Gardiol, Daniele; Noci,
Giancarlo C.; Romoli, Marco; Naletto, Giampiero; Tondello, Giuseppe;
Zattarin, Marco; Malvezzi, Andrea M.; Cesare, Stefano
Bibcode: 2000SPIE.4139..378A
Altcode:
The Ultraviolet and Visible-light Coronagraph (UVC) is one of the
solar remote-sensing instruments proposed for the model payload of the
Solar Orbiter mission. The Solar Orbiter is one of the two 'Flexible'
missions selected in September 2000 by the European Space Agency (ESA)
for the definition study phase. A novel orbital design takes the orbiter
as close as 0.21 astronomical units (AU) to the Sun, with heliographic
latitudes as high as 38 degrees for observations of the solar polar
regions at very high spatial resolution. From this vantage point,
the UVC can, at the same time, image the visible and ultraviolet
coronal emissions and diagnose, with unprecedented temporal and
spatial resolution (down to 1200 km) the full solar corona. The UVC's
optical design, presented here, consists of an externally occulted,
off-axis Gregorian with multilayer-coated optics. The UVC can obtain
monochromatic images in the neutral hydrogen HI Lyman (alpha) , (lambda)
121.6 nm, and single-ionized helium HEII Lyman (alpha) , (lambda) 30.4
nm, lines and measure the polarized brightness (pB) of the visible
K-corona. The ultraviolet Lyman (alpha) lines are separated with two
multilayer coatings mirror and an extreme-ultraviolet transmission
filter. The mirrors' coating optimized for 30.4 nm still has a good
reflectivity at 121.6 nm and visible. The optical performances,
resulting from ray-tracing calculations, are presented here, along
with the expected system response to the coronal signal.
Title: Fast Solar Wind Velocity in a Polar Coronal Hole during
Solar Minimum
Authors: Antonucci, Ester; Dodero, Maria Adele; Giordano, Silvio
Bibcode: 2000SoPh..197..115A
Altcode:
We present a study of the outflow velocity of the fast wind in the
northern polar coronal hole observed on 21 May 1996, during the minimum
of solar activity, in the frame of a joint observing program of the
SOHO (Solar Heliospheric Observatory) mission. The outflow velocity
is inferred from an analysis of the Doppler dimming of the intensities
of the O vi λ1032, 1037 and H i Lα λ1216 lines observed between 1.5
R⊙ and 3.5 R⊙ with the Ultraviolet Coronagraph
Spectrometer (UVCS), operating onboard SOHO. The analysis shows that
for a coronal plasma characterized by low density, as derived for a
polar hole at solar minimum by Guhathakurta et al. (1999), and low
temperature, as directly measured at the base of this coronal hole by
David et al. (1998), the oxygen outflow speed derived spectroscopically
is consistent with that implied by the proton flux conservation. The
hydrogen outflow is also consistent with flux conservation if the
deviation from isotropy of the velocity distribution of the hydrogen
atoms is negligible. Hence, for this cool and tenuous corona,
the oxygen ions and neutral hydrogen atoms flow outward roughly at
the same speed, which increases from 40 km s−1 at 1.5
R⊙ to 360 km s−1 at 3.1 R⊙,
with an average acceleration of the order of ∼4.5×103
cm s−2. The highly anisotropic velocity distributions of
the O vi ions found in the analysis confirm that the process which is
heating the oxygen ions acts preferentially across the magnetic field.
Title: Solar Orbiter --- A High Resolution Mission to the Sun and
Inner Heliosphere
Authors: Fleck, B.; Marsch, E.; Schwenn, R.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Harrison, R. A.; Marsden, R.; Vial, J. -C.
Bibcode: 2000SPD....31.0296F
Altcode: 2000BAAS...32..828F
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rsun and
out-of-ecliptic at heliographic latitudes of up to 38o. By
going to 45 Rsun the SO will allow remote sensing of the
solar atmosphere with unprecedented spatial resolution, and the almost
heliosynchronous orbit segments will permit us to disentangle spatial
and temporal variations in the solar wind in close linkage with the
plasma and radiation conditions in the source regions of the Sun. The
strawman payload encompasses two instrument packages: Heliospheric
Instruments --- high-res visible light telescope and magnetograph
(<40 km), high-res X-ray/EUV imager (<30 km), high-res EUV
spectrometer (<100 km), EUV and visible-light coronagraphs, solar
neutron and γ -ray detectors, radiometers. Heliospheric Instruments
--- solar wind analyzer, magnetometer, energetic particle detectors, IP
dust detector, plasma wave analyser, radio experiment, neutral particle
detector. Using solar electric propulsion (SEP) in conjunction with
multiple planet swing-by manoeuvres, it will take SO two years to reach
a perihelion of 45 Rsun at an orbital period of 149 days,
with an inclination ranging from 6.7o to 23.4o
w.r.t. the ecliptic. During an extended mission phase of about 2
years the inclination will increase to 31.7o, leading to
a maximum heliographic latitude of 38.3o. The SO was one
of the about 40 responses to the Call for Proposals for the next two
"flexi-missions" (F2 and F3) within ESA's Scientific Programme. At
its meeting on 1 March 2000, ESA's Space Science Advisory Committee
recommended the Solar Orbiter among 5 other proposals for an assessment
study. Launch is expected by the end of the decade.
Title: Identification of the Coronal Sources of the Fast Solar Wind
Authors: Giordano, S.; Antonucci, E.; Noci, G.; Romoli, M.; Kohl, J. L.
Bibcode: 2000ApJ...531L..79G
Altcode: 2000astro.ph..1257G
The present spectroscopic study of the ultraviolet coronal emission in a
polar hole, detected on 1996 April 6-9 with the Ultraviolet Coronagraph
Spectrometer aboard the Solar and Heliospheric Observatory spacecraft,
identifies the interplume lanes and background coronal hole regions
as the channels in which the fast solar wind is preferentially
accelerated. In interplume lanes, at heliocentric distance 1.7
Rsolar, the corona expands at a rate between 105 and 150 km
s-1, that is, much faster than in plumes in which the outflow
velocity is between 0 and 65 km s-1. The wind velocity is
inferred from the Doppler dimming of the O VI λλ1032, 1037 lines,
within a range of values, whose lower and upper limit corresponds to
anisotropic and isotropic velocity distribution of the oxygen coronal
ions, respectively.
Title: Solar and Heliospheric Observatory Observations of a Helical
Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Thompson, B. J.; van
Ballegooijen, A.; Strachan, L.; Li, J.; Gardner, L.; O'Neal, R.;
Antonucci, E.; Kohl, J.; Noci, G.
Bibcode: 2000ApJ...529..575C
Altcode:
The EUV Imaging Telescope (EIT), Large Angle Spectrometric Coronagraph
(LASCO), and Ultraviolet Coronagraph Spectrometer (UVCS) instruments
aboard the SOHO satellite observed a prominence eruption (coronal mass
ejection) on 1997 December 12. Ejected plasma moved at about 130 km
s-1 in the plane of the sky and showed Doppler shifts between
-350 and +30 km s-1. The eruption appeared as a strongly
curved arch in EIT images low in the corona. Emission in ions ranging
from Si III to O VI in the UVCS spectra indicates a temperature range
between 104.5 and 105.5 K. The morphology of the
bright emission regions seen by all three instruments suggests several
strands of a helical structure of moderate pitch angle. A reasonable
fit to the spatial structure and the velocity evolution measured by
UVCS is provided by a left-handed helix untwisting at a rate of about
9×10-4 radians s-1.
Title: Oxygen Outflow Velocities in a Polar Coronal Hole
Authors: Giordano, S.; Antonucci, E.; Dodero, M. A.
Bibcode: 2000AdSpR..25.1927G
Altcode:
The expansion velocity of the solar corona in a polar coronal hole
during the minimum of solar activity is inferred from an analysis of
the intensities and profiles of the O VI λ 1032, 1037 lines observed
with the Ultraviolet Coronagraph Spectrometer (UVCS), operating onboard
the Solar Heliospheric Observatory (SOHO). The outflow velocity of
the oxygen ions carried by the solar wind reaches values >= 300 km
s-1 above 2.1 Rsolar This is evidence for ion acceleration
primarily near 1.6-2.1 Rsolar. This analysis also shows that beyond
1.8 Rsolar the velocity distribution of the oxygen ions in the frame
of reference of the solar wind is highly anisotropic, that is, this
distribution is much broader along the line of sight than along the
radial. The velocity anisotropy found in the region of acceleration
of the fast solar wind is evidence for a heating process operating
preferentially in the direction perpendicular to the magnetic field
Title: Hydrogen and Oxygen Temperatures in Coronal Holes
Authors: Antonucci, E.; Giordano, S.; Dodero, M. A.
Bibcode: 2000AdSpR..25.1923A
Altcode:
The analysis of the O VI λ 1032 and 1037 and H I Ly⋋a ⋋l 1216
line profiles, observed with the Ultraviolet Coronagraph Spectrometer
(UVCS) onboard the Solar Heliospheric Observatory (SOHO) in a polar
coronal hole within 1.5 Rsolar and 3.5 Rsolar during the solar activity
minimum, indicates the existence of a large anisotropy in the velocity
distribution of the oxygen ions across the magnetic field lines. This
is evidence for temperatures across the field lines that at 3.1 Rsolar
exceed by >=1.6-1.7 × 108 K the oxygen temperature
inferred along the radial direction, which is ~107 K. The
upper limit for the neutral hydrogen/proton temperature is 2.4-3.0 ×
106 K. The bulk motions across the magnetic field lines,
due to wave motions and nonradial coronal expansion, cannot exceed
-170 km s-1. The results of the present analysis imply
that oxygen ions are heated much more effectively than protons in the
first solar radius of the solar atmosphere and that protons can be
heated more efficiently than electrons. Furthermore, in addition to
the process which heats the oxygen ions to 107 K, a very
strong acceleration operating only perpendicularly to the magnetic
field has to be invoked to justify the temperature excess, of the
order of 108 K, in this direction
Title: Solar Wind Acceleration Region
Authors: Antonucci, E.
Bibcode: 1999ESASP.446...53A
Altcode: 1999ESASP.446...53S; 1999soho....8...53S
No abstract at ADS
Title: An Empirical Model of a Polar Coronal Hole at Solar Minimum
Authors: Cranmer, S. R.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Strachan, L.; Panasyuk, A. V.;
Gardner, L. D.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond,
J. C.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Benna, C.;
Ciaravella, A.; Giordano, S.; Habbal, S. R.; Karovska, M.; Li, X.;
Martin, R.; Michels, J. G.; Modigliani, A.; Naletto, G.; O'Neal,
R. H.; Pernechele, C.; Poletto, G.; Smith, P. L.; Suleiman, R. M.
Bibcode: 1999ApJ...511..481C
Altcode:
We present a comprehensive and self-consistent empirical model
for several plasma parameters in the extended solar corona above
a polar coronal hole. The model is derived from observations
with the SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO)
during the period between 1996 November and 1997 April. We compare
observations of H I Lyα and O VI λλ1032, 1037 emission lines
with detailed three-dimensional models of the plasma parameters and
iterate for optimal consistency between measured and synthesized
observable quantities. Empirical constraints are obtained for
the radial and latitudinal distribution of density for electrons,
H0, and O5+, as well as the outflow velocity
and unresolved anisotropic most probable speeds for H0 and
O5+. The electron density measured by UVCS/SOHO is consistent
with previous solar minimum determinations of the white-light coronal
structure; we also perform a statistical analysis of the distribution
of polar plumes using a long time series. From the emission lines we
find that the unexpectedly large line widths of H0 atoms
and O5+ ions at most heights are the result of anisotropic
velocity distributions. These distributions are not consistent with
purely thermal motions or the expected motions from a combination of
thermal and transverse wave velocities. Above 2 Rsolar,
the observed transverse most probable speeds for O5+ are
significantly larger than the corresponding motions for H0,
and the outflow velocities of O5+ are also significantly
larger than the corresponding velocities of H0. Also, the
latitudinal dependence of intensity constrains the geometry of the
wind velocity vectors, and superradial expansion is more consistent
with observations than radial flow. We discuss the constraints and
implications on various theoretical models of coronal heating and
acceleration.
Title: Ultraviolet and Optical Observations of a Coronal Transient
with SOHO
Authors: Ciaravella, A.; Raymond, J. C.; Strachan, L.; Thompson,
B. J.; Cyr, O. C. St.; Gardner, L.; Modigliani, A.; Antonucci, E.;
Kohl, J.; Noci, G.
Bibcode: 1999ApJ...510.1053C
Altcode:
A coronal transient was observed on 1997 March 6 at 1.6
Rsolar over an active region on the east limb. We observed
both the edge of horizontally compressed gas and the diffuse curtain of
coronal material. The region was monitored for 4 hr, and the H I Lyα,
O VI λλ1031.91, 1037.61, N V λλ1242.80, 1238.80, and O V] λ1218.35
lines were detected during the ejection evolution. The density,
velocity, temperature, and oxygen abundance of the ejected plasma have
been obtained from the observed spectra. Intermediate temperature lines
of N V, O VI, and O V show a large enhancement, suggesting a quite
narrow range of plasma temperature around 4×105 K. Doppler
shifts of the ejected material evolve from an initial blueshift of 100
km s-1 to a redshift of 145 km s-1. The outflow
velocity, as determined by Doppler dimming analysis of the O VI doublet,
is only about 20 km s-1.
Title: Flare dynamics.
Authors: Antonucci, E.; Alexander, D.; Culhane, J. L.; de Jager, C.;
MacNeice, P.; Somov, B. V.; Zarro, D. M.
Bibcode: 1999mfs..conf..331A
Altcode:
The following topics were dealt with: results from soft X-ray spectra,
chromospheric evaporation, nature of nonthermal line broadening,
flare modelling.
Title: Multilayer grating spectrometer for solar observations
Authors: Antonucci, E.; Ciminiera, Luigi; Malvezzi, Andrea M.;
Tondello, Giuseppe
Bibcode: 1998SPIE.3443...75A
Altcode:
A stigmatic spectrograph in the 17 - 23 nm region for observations of
the solar disk and corona based on multilayer mirror and grating is
described. Its main scientific use is global surveying of the disk
with approximately equal 10 arcsec2 resolution. Spectral
resolution is used to monitor temperature- and density-sensitive
spectral lines thus obtaining solar temperature and density maps in
the 105 - 107 degrees Kelvin, 1013
- 1018 cm-3 ranges, respectively. The use
of off-axis paraboloidal telescope coupled with a toroidal grating
results in spectral resolving powers of the order of 1000 and angular
resolution of approximately equal 10 arcsec throughout an instantaneous
field-of-view of 10 arcsec X 40 arcmin. Temporal resolution of the
order of 0.1 second is expected which can be of use in observations
of high brilliance events. The system is also equipped with a visible
channel to correlate XUV events with ground observations.
Title: Solar Wind Velocity and Anisotropic Coronal Kinetic Temperature
Measured with the O VI Doublet Ratio
Authors: Dodero, M. A.; Antonucci, E.; Giordano, S.; Martin, R.
Bibcode: 1998SoPh..183...77D
Altcode:
Doppler dimming of the O vi resonance lines (λ1032 Å, λ1037 Å) in
an expanding corona is calculated including the pumping effect on the
O vi λ1037.61 Å of both C ii lines at λ1036.34 Å and λ1037.02 Å,
and the effect of the width of the absorption profiles of the coronal
oxygen ions along the incident radiation. The pumping effect of the
C ii line at λ1036.34 Å allows us to extend to approximately 450 km
s−1 the measurement of solar wind velocities with the O vi line ratio
technique. Since the emissivity ratio of the O vi doublet depends on
the width of the oxygen coronal absorbing profiles, this ratio can
provide an accurate measurement of the solar wind velocity in the
case that the width of the absorbing profile along the direction of
the incident radiation is independently determined. However, if on
the one hand the ratio of the emissivities of the O vi doublet has
limitations in probing the wind velocity, on the other hand it can be
used as a diagnostics for inferring the velocity distribution of the
coronal O vi ions along the radial, and detecting possible velocity
anisotropies. This diagnostics, applied to recent observational results,
allows us to infer that the velocity distribution of the oxygen ions
is much broader in the direction perpendicular to the magnetic field
direction, and that the acceleration of the fast solar wind in the
first 2 solar radii is high.
Title: UVCS/SOHO Empirical Determinations of Anisotropic Velocity
Distributions in the Solar Corona
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Cranmer, S. R.; Strachan, L.; Panasyuk, A. V.; Gardner,
L. D.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond, J. C.;
Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Benna, C.; Ciaravella,
A.; Giordano, S.; Habbal, S. R.; Karovska, M.; Li, X.; Martin, R.;
Michels, J. G.; Modigliani, A.; Naletto, G.; O'Neal, R. H.; Pernechele,
C.; Poletto, G.; Smith, P. L.; Suleiman, R. M.
Bibcode: 1998ApJ...501L.127K
Altcode:
We present a self-consistent empirical model for several plasma
parameters of a polar coronal hole near solar minimum, derived from
observations with the Solar and Heliospheric Observatory Ultraviolet
Coronagraph Spectrometer. The model describes the radial distribution of
density for electrons, H0, and O5+ and the outflow
velocity and unresolved most probable velocities for H0
and O5+ during the period between 1996 November and 1997
April. In this Letter, we compare observations of H I Lyα and O
VI λλ1032, 1037 emission lines with spatial models of the plasma
parameters, and we iterate for optimal consistency between measured and
synthesized observable quantities. The unexpectedly large line widths
of H0 atoms and O5+ ions at most radii are the
result of anisotropic velocity distributions, which are not consistent
with purely thermal motions or the expected motions from a combination
of thermal and transverse wave velocities. Above 2 Rsolar,
the observed transverse, most probable speeds for O5+ are
significantly larger than the corresponding motions for H0,
and the outflow velocities of O5+ are also significantly
larger than the corresponding velocities of H0. We discuss
the constraints and implications on various theoretical models of
coronal heating and acceleration.
Title: Empirical Models of Temperature, Densities, and Velocities
in the Solar Corona
Authors: Fludra, A.; Strachan, L.; Alexander, D.; Bagenal, F.;
Biesecker, D. A.; Dobrzycka, D.; Galvin, A. B.; Gibson, S.; Hassler,
D.; Yo, Y. -K.; Panasyuk, A. V.; Thompson, B.; Warren, H.; del Zanna,
G.; Zidowitz, S.; Antonucci, E.; Bromage, B. J. I.; Giordano, S.
Bibcode: 1998EOSTr..79..278F
Altcode:
We present empirical results for temperatures, densities, and outflow
velocities of constituents of the solar corona from 1 to 3 Ro in
polar coronal holes and an equatorial streamer. Data were obtained
from a variety of space and ground-based instruments during August
1996 as part of the SOHO Whole Sun Month Campaign. From white light
data obtained with the SOHO/LASCO/C2 and HAO/Mauna Loa coronagraphs,
we determine electron densities and compare them to those determined
from the density-sensitive EUV line ratio of Si IX 350/342 Angstroms
observed by the SOHO/Coronal Diagnostic Spectrometer (CDS). Moreover,
from the white light density profiles we calculate temperature profiles
and compare to temperature diagnostic information from EUV lines and
soft X-ray images from Yohkoh. H I Ly alpha and O VI 1032/1037 Angstrom
intensities from the SOHO Ultraviolet Coronagraph Spectrometer (UVCS)
are used to estimate both the direction and magnitude of plasma outflow
velocities in coronal holes and streamers above 1.5 Ro. The velocities
are derived using densities from white light coronagraph data and
coronal electron temperature estimates derived from Ulysses/SWICS
ion composition data. Near the base of the corona we find the white
light and spectral analysis produce consistent density and temperature
information. In the extended corona we find results consistent with
high outflow velocities and a superradial outflow geometry in polar
coronal holes.
Title: Tomographic Reconstructions of the Corona from UVCS/SOHO
Synoptic Observations
Authors: Panasyuk, A. V.; Strachan, L.; Finesehi, S.; Gardner, L. D.;
Raymond, J.; Kohl, J. L.; Antonucci, E.; Giordano, S.; Romoli, M.
Bibcode: 1998ASPC..140..407P
Altcode: 1998ssp..conf..407P
No abstract at ADS
Title: Scientific Achievements of SOHO: Outer Corona
Authors: Antonucci, E.
Bibcode: 1998ESASP.417...25A
Altcode: 1998cesh.conf...25A
The Solar Heliospheric Observatory (SOHO) has broadened our capability
to observe the outer solar corona by gaining access to an unexplored
electromagnetic domain, the ultraviolet region, with the Ultraviolet
Coronagraph Spectrometer (UVCS), and to a much larger field of view,
30 solar radii, and better temporal coverage in visible light with
the Large Angle Spectroscopic Coronagraoph (LASCO). The main results
obtained with the SOHO coronagraphs concern the identification of the
sources and regions of acceleration of the slow and fast solar wind,
of possible signatures of the mechanisms of coronal expansion, and of
instabilities leading to coronal transients.
Title: Ultraviolet Spectroscopy of a Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Fineschi, S.; Romoli,
M.; Benna, C.; Gardner, L.; Giordano, S.; Michels, J.; O'Neal, R.;
Antonucci, E.; Kohl, J.; Noci, G.
Bibcode: 1998ASPC..150..370C
Altcode: 1998npsp.conf..370C; 1998IAUCo.167..370C
No abstract at ADS
Title: Doppler dimming of the O VI 1032, 1037 doublet in the solar
corona
Authors: Dodero, M. A.; Antonucci, E.; Martin, R.
Bibcode: 1998MmSAI..69..757D
Altcode:
No abstract at ADS
Title: Velocity Fields in the Solar Corona during Mass Ejections as
Observed with UVCS-SOHO
Authors: Antonucci, E.; Kohl, J. L.; Noci, G.; Tondello, G.; Huber,
M. C. E.; Gardner, L. D.; Nicolosi, P.; Giordano, S.; Spadaro, D.;
Ciaravella, A.; Raymond, C. J.; Naletto, G.; Fineschi, S.; Romoli, M.;
Siegmund, O. H. W.; Benna, C.; Michels, J.; Modigliani, A.; Panasyuk,
A.; Pernechele, C.; Smith, P. L.; Strachan, L.; Ventura, R.
Bibcode: 1997ApJ...490L.183A
Altcode:
This Letter presents the observations of the first two coronal mass
ejections (CMEs) obtained with the Ultraviolet Coronagraph Spectrometer
of SOHO. Both CMEs were observed at high spectral resolution in the
ultraviolet domain. The first event on 1996 June 6-7 was observed in H I
Lyα λ1216 and Lyβ λ1026, O VI λλ1032 and 1037, Si XII λλ499 and
521 and imaged within 1.5 and 5 Rsolar. The second event on
1996 December 23 was observed in several H I lines and cool lines such
as C III λ977, N III λλ990-992, and O V λ630. The analysis of line
profiles has allowed us to determine the line-of-sight velocities of the
extended corona during a mass ejection. In particular there is evidence
for mass motions consistent with untwisting magnetic fields around an
erupted flux tube in one of the events and line of sight velocities of
200 km s-1 in the early phase of the second event presumably
related to the expansion of the leading arch of the transient.
Title: Solar Wind Acceleration in the Solar Corona
Authors: Giordano, S.; Antonucci, E.; Benna, C.; Kohl, J. L.; Noci,
G.; Michels, J.; Fineschi, S.
Bibcode: 1997ESASP.415..327G
Altcode: 1997cpsh.conf..327G
No abstract at ADS
Title: Determination of 3D Coronal Structures from UVCS/SOHO Synoptic
Observations
Authors: Strachan, L.; Panasyuk, A. V.; Fineschi, S.; Gardner, L. D.;
Raymond, J. C.; ANtonucci, E.; Giordano, S.; Romoli, M.; Noci, G.;
Kohl, J. L.
Bibcode: 1997ESASP.415..539S
Altcode: 1997cpsh.conf..539S
No abstract at ADS
Title: Ultraviolet Observations of Coronal Mass Ejections
Authors: Ciaravella, A.; Raymond, J. C.; Benna, C.; Fineschi, S.;
Gardner, L. D.; Giordano, S.; O'Neal, R. H.; Reale, F.; Romoli, M.;
Michels, J.; Antonucci, E.; Kohl, J. L.; Noci, G.
Bibcode: 1997ESASP.415..543C
Altcode: 1997cpsh.conf..543C
No abstract at ADS
Title: Ultraviolet Coronagraph Spectrometer Observation of the 1996
December 23 Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Fineschi, S.; Romoli,
M.; Benna, C.; Gardner, L.; Giordano, S.; Michels, J.; O'Neal, R.;
Antonucci, E.; Kohl, J.; Noci, G.
Bibcode: 1997ApJ...491L..59C
Altcode:
The Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar
and Heliospheric Observatory (SOHO) observed a spectacular coronal
mass ejection (CME) caused by a prominence eruption on 1996 December
23. The evolution of the ejected prominence material was followed for
1 hr and 50 minutes. The observation consists of a series of 5 minute
exposures, at a fixed heliocentric distance of 1.5 Rsolar
in several spectral ranges. The Lyman lines of hydrogen brighten
more than 2 orders of magnitude during the CME. The C III 977.02 Å
line is very bright, and many other low-temperature lines have been
detected. Line intensities and profiles provide important diagnostics
for the physical and dynamical parameters of the ejected plasma. Lines
widths show nonthermal line broadening due to a plasma expansion with
velocity larger than 50 km s-1. The Lyα inside the CME
region shows red and blue shifts, up to 0.2 Å (50 km s-1)
and 0.8 Å (200 km s-1), respectively. A preliminary estimate
shows a flat emission measure distribution 3 or 4 orders of magnitude
smaller than typical prominence emission measures. Essentially the same
structure in space and velocity is seen in the Lyman lines, in C III
(105 K) and in O VI (3×105 K).
Title: The Sun and its atmosphere. Proceedings. E2.1 Symposium of
COSPAR Scientific Commission E held during the Thirty-first COSPAR
Scientific Assembly, Birmingham (UK), 14 - 21 Jul 1996.
Authors: Antonucci, E.; Shea, M. A.
Bibcode: 1997AdSpR..20R....A
Altcode:
The following topics were dealt with: early observation of SOHO
instruments, spectral diagnosis of the solar atmosphere, modelling of
coronal processes, observations of flares and the quiet Sun, prediction
of solar activity.
Title: Composition of Coronal Streamers from the SOHO Ultraviolet
Coronagraph Spectrometer
Authors: Raymond, J. C.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi,
S.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella,
A.; Cranmer, S.; Giordano, S.; Karovska, M.; Martin, R.; Michels, J.;
Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto,
G.; Smith, Peter L.; Suleiman, R. M.; Strachan, L.
Bibcode: 1997SoPh..175..645R
Altcode:
The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers
the 940-1350 Å range as well as the 470-630 Å range in second
order. It has detected coronal emission lines of H, N, O, Mg, Al, Si,
S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance
scattering of emission lines from the solar disk dominates the
intensities of a few lines, but electron collisional excitation produces
most of the lines observed. Resonance, intercombination and forbidden
lines are seen, and their relative line intensities are diagnostics
for the ionization state and elemental abundances of the coronal gas.
Title: First Results from the SOHO Ultraviolet Coronagraph
Spectrometer
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Gardner, L. D.; Nicolosi, P.; Strachan, L.; Fineschi, S.;
Raymond, J. C.; Romoli, M.; Spadaro, D.; Panasyuk, A.; Siegmund,
O. H. W.; Benna, C.; Ciaravella, A.; Cranmer, S. R.; Giordano, S.;
Karovska, M.; Martin, R.; Michels, J.; Modigliani, A.; Naletto, G.;
Pernechele, C.; Poletto, G.; Smith, P. L.
Bibcode: 1997SoPh..175..613K
Altcode:
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being
used to observe the extended solar corona from 1.25 to 10 R⊙ from
Sun center. Initial observations of polar coronal holes and equatorial
streamers are described. The observations include measurements of
spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å,
Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx
610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been
observed. Preliminary results for derived H0, O5+,
Mg9+, and Fe11+ velocity distributions and initial
indications of outflow velocities for O5+ are described. In
streamers, the H0 velocity distribution along the line of
sight (specified by the value at e-1, along the line of
sight) decreases from a maximum value of about 180 km s-1
at 2 R⊙ to about 140 km s-1 at 8 R⊙. The value for
O5+ increases with height reaching a value of 150 km
s-1 at 4.7 R⊙. In polar coronal holes, the O5+
velocity at e-1 is about equal to that of H0
at 1.7 R⊙ and significantly larger at 2.1 R⊙. The O5+
in both streamers and coronal holes were found to have anisotropic
velocity distributions with the smaller values in the radial direction.
Title: Evidence of untwisting magnetic fields in the Coronal Mass
Ejections of June 7, 1996
Authors: Antonucci, E.; Giordano, S.; Noci, G.; Kohl, J. K.; Spadaro,
D.; Benna, C.
Bibcode: 1997BAAS...29R1120A
Altcode:
No abstract at ADS
Title: Global Sun Study: line broadening in the extended corona
Authors: Giordano, S.; Antonucci, E.; Benna, C.; Kohl, J. K.; Noci, G.
Bibcode: 1997BAAS...29.1120G
Altcode:
No abstract at ADS
Title: The Sun and its role in the heliosphere. Proceedings. E2.2
Symposium of COSPAR Scientific Commission E held during the
Thirty-first COSPAR Scientific Assembly, Birmingham (UK), 14 -
21 Jul 1996.
Authors: Antonucci, E.; Page, D. E.
Bibcode: 1997AdSpR..20Q....A
Altcode:
The following topics were dealt with: solar corona, solar wind,
structure, composition and variations, solar wind plasma, Ulysses
measurements, heliospheric magnetic fields, interplanetary medium,
interplanetary plasma and shocks, and energetic particle fluxes.
Title: Empirical Models of the Extended Solar Corona
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Ciaravella, A.;
Cranmer, S.; Dobrzycka, D.; Fineschi, S.; Gardner, L. D.; Huber,
M. C. E.; Panasyuk, A.; Raymond, J. C.; Strachan, L.
Bibcode: 1997SPD....28.0303K
Altcode: 1997BAAS...29..907K
Ultraviolet spectroscopy is being used to produce self consistent
empirical models of polar coronal holes and equatorial streamers in the
extended solar corona. The models are intended to provide experimental
values for many of the primary plasma parameters of the extended corona,
which can then be used to constrain theoretical coronal and solar
wind models. The empirical models are based on synoptic observations
and other measurements of spectral line profiles and intensities of
H I Lyalpha , O VI 1032 Angstroms and 1037 Angstroms, Fe XII 1242
Angstroms, Mg X 625 Angstroms and several others. Information about
velocity distributions, outflow velocities, densities and elemental
abundances as derived from the observations are specified in the
models. The models used to specify the empirically derived parameters
include a description of well established theoretical processes such
as those controlling ionization balance, collisional excitation,
and resonant scattering. They do not include any descriptions of
less well established processes such as heating functions, transverse
wave motions or direct momentum deposition by waves. The intent is to
provide, to the maximum extent possible, empirical descriptions that
can be used, together with theoretical models, to help identify the
dominant physical processes responsible for coronal heating, solar wind
acceleration and the chemical composition of the solar wind. This work
is supported by NASA Grant NAG5-3192 to the Smithsonian Astrophysical
Observatory, the Italian Space Agency and Swiss funding sources.
Title: UVCS/SOHO Synoptic Observations of the Extended Corona during
the Whole Sun Month Campaign
Authors: Strachan, L.; Fineschi, S.; Gardner, L. D.; Panasyuk, A. V.;
Kohl, J. L.; Antonucci, E.; Giordano, S.; Romoli, M.
Bibcode: 1997SPD....28.0122S
Altcode: 1997BAAS...29..883S
Daily synoptic observations were made with UVCS/SOHO during the Whole
Sun Month (10 August to 8 September 1996) in order to characterize
the large-scale spatial distributions of plasma parameters in the
solar corona from 1.5 to 3 solar radii. We use observed line profiles
and intensities of H I Lyman alpha and O VI 1032/1037 Angstroms,
and white light polarized brightness measurements to derive physical
properties of the plasma in the solar wind acceleration region. Line of
sight velocity distributions and bulk outflow velocities for neutral
hydrogen and for O({5) +}, and electron densities can be derived from
these measurements. We show some results from the on-going effort and
present some of these data as synoptic maps. The ultimate goal of this
work is to produce a data set that can be used in developing empirical
models that describe the solar minimum conditions of the extended
corona. This work is supported by NASA under Grant NAG5-3192 to the
Smithsonian Astrophysical Observatory, by the Italian Space Agency,
and by Swiss funding sources.
Title: Ultraviolet Spectroscopy of Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Fineschi, S.; Romoli, M.;
Antonucci, E.
Bibcode: 1997SPD....28.0121C
Altcode: 1997BAAS...29..883C
The Ultraviolet Coronagraph Spectrometer (UVCS) observed a spectacular
coronal mass ejection (CME) on December 23 1996, caused by a prominence
eruption. The evolution of the ejected plasma was followed for about 2h
in both ultraviolet and visible light channels. The observation consists
of a series of 5 minutes exposures, at heliocentric distance of 1.5
R_sun. Excursions of more than two orders of magnitude are detected in
the Lyalpha (1216 Angstroms/), Lybeta (1026 Angstroms/), Lygamma (972
Angstroms/) and Lydelta (949 Angstroms/) lines of hydrogen. The C III
(977 A) is very bright during the CME evolution, but many other more
weak low temperature lines, like N III (991 Angstroms/, 991 Angstroms/),
N II (1085 Angstroms/), N V (1242 Angstroms/), have been detected. Line
intensities and profiles have been measured providing important
diagnostics for a very detailed study of physical and dynamical
parameters of CME. Lines widths show non-thermal line broadening due
to an expansion of plasma with velocity larger than 50 km/sec. The
Lyalpha spatial pattern of the line shift appears very structured with
red and blue shifts, along the line of sight, up to 0.2 Angstroms/
( 50km/sec) and 1 Angstroms ( 200 km/sec) respectively. The data also
provide the emission measure in the LogT range 4.0 - 5.5. A variation
of one order of magnitude has been observed in the polarized brightness.
Title: Absolute Elemental Abundances in Streamers
Authors: Raymond, J. C.; Kohl, J.; Suleiman, R.; Ciaravella, A.;
Fineschi, S.; Gardner, L.; Panasyuk, A.; Strachan, L.; Noci, G.;
Antonucci, E.; Nicolosi, P.; Naletto, G.; Giordano, S.; Benna, C.
Bibcode: 1997SPD....28.0114R
Altcode: 1997BAAS...29..881R
The UVCS instrument aboard the SOHO satellite has measured the
intensities of emission lines of H, N, O, Mg, Al, S, Ar, Ca ,Fe and Ni
at 1.5 solar radii in a quiescent equatorial helmet streamer and in an
active region streamer. The First Ionization Potential (FIP) effect is
clearly seen. Low FIP elements show nearly photospheric abundances above
the active region and along the edges of the equatorial streamer, while
high FIP elements are depleted by a factor of 2-3. Near the center of
the streamer, presumably the closed field region, the low-FIP elements
are at about 1/3 photospheric abundances, and the high FIP elements
are near 1/10 their photospheric values.
Title: A Comparison of Radio Axis with Host Galaxy Plane Axis in
Seyfert Galaxies
Authors: Schmitt, Henrique R.; Kinney, Anne L.; Storchi-Bergmann,
Thaisa; Antonucci; Robert
Bibcode: 1997ApJ...477..623S
Altcode: 1996astro.ph.11169S
We use the radio axis as an indicator of the orientation of the
obscuring torus in Seyfert galaxies and analyze the difference between
the position angles of extended radio structures and host galaxy major
axis of Seyfert 1 and Seyfert 2 galaxies. We find that Seyfert 1's are
less likely to have extended radio structures along the host galaxy
major axis while Seyfert 2's have these structures distributed in most
directions. We also find a zone of avoidance in the distribution of
position angles: both Seyfert 1's and Seyfert 2's seem to avoid close
alignment between the radio axis and the host galaxy plane axis. These
results are analyzed from the point of view of a model in which Seyfert
1's have their obscuring torus axis aligned preferentially along the
host galaxy disk axis and Seyfert 2's have their torus axis lying at
an intermediate angle between the galaxy disk and its axis.
Title: Preface
Authors: Antonucci, E.; Shea, M. A.
Bibcode: 1997AdSpR..20.2205A
Altcode:
No abstract at ADS
Title: Plume and interplume regions and solar wind acceleration in
polar coronal holes between 1.5 and 3.5 R
Authors: Giordano, S.; Antonucci, E.; Benna, C.; Romoli, M.; Noci,
G.; Kohl, J. L.; Fineschi, S.; Michels, J.; Naletto, G.
Bibcode: 1997ESASP.404..413G
Altcode: 1997cswn.conf..413G
No abstract at ADS
Title: Ultraviolet spectroscopy of a coronal mass ejection with UVCS
Authors: Ciaravella, A.; Raymond, J.; Fineschi, S.; Romoli, M.; Benna,
C.; Gardner, L.; Giordano, S.; O'Neal, R.; Michels, J.; Antonucci,
E.; Noci, G.; Kohl, J.
Bibcode: 1997ESASP.404..279C
Altcode: 1997cswn.conf..279C
No abstract at ADS
Title: Signature of open magnetic field lines in the extended solar
corona and of solar wind acceleration
Authors: Antonucci, E.; Giordano, S.; Benna, C.; Kohl, J. L.; Noci,
G.; Michels, J.; Fineschi, S.
Bibcode: 1997ESASP.404..175A
Altcode: 1997cswn.conf..175A
No abstract at ADS
Title: Spectroscopic observations of the extended corona during the
SOHO whole sun month
Authors: Strachan, L.; Raymond, J. C.; Panasyuk, A. V.; Fineschi,
S.; Gardner, L. D.; Antonucci, E.; Giordano, S.; Romoli, M.; Noci,
G.; Kohl, J. L.
Bibcode: 1997ESASP.404..691S
Altcode: 1997cswn.conf..691S
No abstract at ADS
Title: Measurements of H I and O VI velocity distributions in the
extended solar corona with UVCS/SOHO and UVCS/Spartan 201
Authors: Kohl, J. H.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi, S.; Raymond, J. C.;
Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella,
A.; Cranmer, S. R.; Giordano, S.; Karovska, M.; Martin, R.; Michels,
J.; Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto,
G.; Smith, P. L.; Strachan, L.
Bibcode: 1997AdSpR..20....3K
Altcode:
The Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric
Observatory, UVCS/SOHO, and the Ultraviolet Coronal Spectrometer on
the Spartan 201 satellite, UVCS/Spartan, have been used to measure
H I 1215.67 A˚ line profiles in polar coronal holes of the Sun at
projected heliocentric heights between 1.5 and 3.0 R_solar. UVCS/SOHO
also measured line profiles for H I 1025.72 A˚, O VI 1032/1037 A˚,
and Mg X 625 A˚. The reported UVCS/SOHO observations were made between
5 April and 21 June 1996 and the UVCS/Spartan observations were made
between 11 and 12 April 1993. Both sets of measurements indicate that a
significant fraction of the protons along the line of sight in coronal
holes have velocities larger than those for a Maxwellian velocity
distribution at the expected electron temperature. Most probable
speeds for O^5+ velocity distributions along the lines of sight are
smaller than those of H^0 at 1.5 R_solar, are comparable at about 1.7
R_solar and become significantly larger than the H^0 velocities above
2 R_solar. There is a tendency for the O^5+ line of sight velocity
distribution in concentrations of polar plumes to be more narrow than
those in regions away from such concentrations. UVCS/SOHO has identified
31 spectral lines in the extended solar corona.
Title: First Results from UVCS: Dynamics of the Extended Corona
Authors: Antonucci, E.; Noci, G.; Kohl, J. L.; Tondello, G.; Huber,
M. C. E.; Giordano, S.; Benna, C.; Ciaravella, A.; Fineschi, S.;
Gardner, L. D.; Martin, R.; Michels, J.; Naletto, G.; Nicolosi, P.;
Panasyuk, A.; Raymond, C. J.; Romoli, M.; Spadaro, D.; Strachan, L.;
van Ballegooijen, A.
Bibcode: 1997ASPC..118..273A
Altcode: 1997fasp.conf..273A
The Ultraviolet Coronagraph Spectrometer (UVCS) started to observe
the Sun at the end of January 1996. Here we present a selection of
results obtained with the UVCS in the first months of operation. UV
spectral line profiles in coronal holes, and in general in regions
with open magnetic field lines, are much broader than in closed
field line regions; that is, line-of-sight velocities are much
larger in open field lines . Polar plumes have narrower profiles
than interplume regions. The O VI ratio diagnostics indicates that in
polar coronal holes the outflow velocity is progressively increasing
with heliodistance and exceeds 100 km/sec near 2--2.5 solar radii. A
coronal mass ejection observation has revealed line--of--sight plasma
motions of 100 km/sec and a complex dynamics.
Title: First results from UVCS/SOHO
Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.;
Raymond, J. C.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.;
Ciaravella, A.; Giordano, S.; Michels, J.; Modigliani, A.; Panasyuk,
A.; Pernechele, C.; Poletto, G.; Smith, P. L.; Strachan, L.
Bibcode: 1997AdSpR..20.2219N
Altcode:
We present here the first results obtained by the Ultraviolet
Coronagraph Spectrometer (UVCS) operating on board the SOHO
satellite. The UVCS started to observe the extended corona at the end
of January 1996; it routinely obtains coronal spectra in the 1145 A˚ -
1287 A˚, 984 A˚ - 1080 A˚ ranges, and intensity data in the visible
continuum. Through the composition of slit images it also produces
monocromatic images of the extended corona. The performance of the
instrument is excellent and the data obtained up to now are of great
interest. We briefly describe preliminary results concerning polar
coronal holes, streamers and a coronal mass ejection, in particular: the
very large r.m.s. velocities of ions in polar holes (hundreds km/sec
for OVI and MgX); the puzzling difference between the HI Ly-alpha
image and that in the OVI resonance doublet, for most streamers; the
different signatures of the core and external layers of the streamers
in the width of the ion lines and in the OVI doublet ratio, indicating
larger line-of-sight (l.o.s.) and outflow velocities in the latter.
Title: The quiescent corona and slow solar wind
Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Fineschi, S.; Gardner, L. D.; Korendyke, C. M.; Nicolosi,
P.; Romoli, M.; Spadaro, D.; Maccari, L.; Raymond, J. C.; Siegmund,
O. H. W.; Benna, C.; Ciaravella, A.; Giordano, S.; Michels, J.;
Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto,
G.; Smith, P. L.; Strachan, L.
Bibcode: 1997ESASP.404...75N
Altcode: 1997cswn.conf...75N; 1997soho....5...75N
No abstract at ADS
Title: Future Space Instrumentation for Solar Physics
Authors: Antonucci, E.; Simnett, G. M.
Bibcode: 1997LNP...489..261A
Altcode: 1997shpp.conf..261A
We review the space instrumentation that is currently being developed
for studies of the Sun. Currently the main solar physics mission
is SOHO, which has support from Yohkoh, Coronas I and a variety of
"particles and fields" spacecraft such as Polar, Wind, Geotail and
Interball. The principal new facility will be the TRACE mission, which
is scheduled for launch in 1997/1998. For the medium term future,
missions such as the Solar Probe, Coronas-F and Foton, plus the
successor to Yohkoh are likely to be realised, at least in part. Other
missions are in a definition phase, such as HESSI, SIMURIS and a STEREO
mission of some form. New particle instruments which can detect solar
emissions, such as ACE, will be launched before the year 2000. The
ESA Horizon 2000+ program has some medium missions, yet to be defined,
which should be devoted to solar studies.
Title: Preface
Authors: Antonucci, Ester; Page, D. Edgar
Bibcode: 1997AdSpR..20....1A
Altcode:
No abstract at ADS
Title: Stray light, radiometric, and spectral characterization of
UVCS/SOHO: laboratory calibration and flight performance
Authors: Gardner, Larry D.; Kohl, J. L.; Daigneau, P. S.; Dennis,
E. F.; Fineschi, Silvano; Michels, J.; Nystrom, George U.;
Panasyuk, Alexander; Raymond, John C.; Reisenfeld, D. J.; Smith,
Peter L.; Strachan, Leonard; Suleiman, R.; Noci, G. C.; Romoli, Marco;
Ciaravella, A.; Modigliani, A.; Huber, Martin C.; Antonucci, E.; Benna,
C.; Giordano, S.; Tondello, Giuseppe; Nicolosi, Piergiorgio; Naletto,
Giampiero; Pernechele, Claudio; Spadaro, D.; Siegmund, Oswald H.;
Allegra, A.; Carosso, Paolo A.; Jhabvala, Murzy D.
Bibcode: 1996SPIE.2831....2G
Altcode:
The Ultraviolet Coronagraph Spectrometer is one of the instruments
on board the Solar and Heliospheric Observatory spacecraft, which
was launched in December, 1995. The instrument is designed to make
ultraviolet spectrometric measurements and visible polarimetric
measurements of the extended solar corona. Prior to launch laboratory
measurements were carried out to determine system level values for
many of the key performance parameters. Further measurements on
instrument performance have been carried out since launch. Presented
are descriptions of measurement techniques and representative results.
Title: In-Flight Performance of the SOHO Ultraviolet Coronagraph
Spectrometer
Authors: Gardner, L. D.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Ciaravella, A.; Fineschi, S.; Giordano,
S.; Moran, T.; Naletto, G.; Nicolosi, P.; Romoli, M.; Strachan,
L.; Benna, C.; Pernechele, C.; Raymond, J. C.; Siegmund, O. H. W.;
Spadaro, D.; Smith, P. L.
Bibcode: 1996AAS...188.3705G
Altcode: 1996BAAS...28..878G
The in-flight performance of the SOHO Ultraviolet Coronagraph
Spectrometer (UVCS/SOHO) is consistent with the pre-launch
characterization and meets all planned observational
requirements. Measurements of the key UVCS/SOHO performance
characteristics have been performed. This paper describes the
measurement techniques and the results. In-flight values for the
spectral and spatial resolutions, wavelength scales, the flat
fields, the geometric distortions, radiometric calibrations,
and stray light levels for the two ultraviolet channels have been
determined. Comparisons will be made to pre-flight measurements at both
the component level and system level. This work is supported by NASA
under contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
by the Italian Space Agency and by Switzerland.
Title: Spectroscopic Diagnostic Techniques with the SOHO Ultraviolet
Coronagraph Spectrometer
Authors: Romoli, M.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello,
G.; Huber, M. C. E.; Fineschi, S.; Karovska, M.; Moran, T.; Strachan,
L.; Ciaravella, A.; Benna, C.; Gardner, L. D.; Giordano, S.; Naletto,
G.; Nicolosi, P.; Raymond, J. C.; Siegmund, O. H. W.; Spadaro, D.;
Smith, P. L.
Bibcode: 1996AAS...188.3703R
Altcode: 1996BAAS...28R.877R
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) uses
spectroscopic diagnostic techniques and polarimetry to determine
velocity distributions, temperatures, outflow velocities and densities
of protons, electrons, and several minor ions in the extended solar
corona. This paper describes the initial use of these techniques with
UVCS/SOHO. Velocity distributions are derived from the observed spectral
line profiles. In some cases, grating scans are used to improve the
spectral resolution. The Doppler dimming method is used to determine
radial outflow velocities and spectral line shifts are used for line of
sight velocity measurements. The electron densities are derived from
visible polarized radiance measurements. The status of attempts to
derive electron temperatures from observations of electron scattered
HI Lyman-alpha will be presented. This research is supported by NASA
Contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
by the Italian Space Agency and by Switzerland.
Title: Ultraviolet Imaging of the Extended Solar Corona with the
SOHO Ultraviolet Coronagraph Spectrometer
Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Strachan, L.; Giordano, S.; Panasyuk, A.; Benna, C.;
Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi,
P.; Raymond, J. C.; Romoli, M.; Siegmund, O. H. W.; Spadaro, D.;
Smith, P. L.
Bibcode: 1996AAS...188.3701N
Altcode: 1996BAAS...28..877N
Spectroscopic observations of the extended solar corona with the SOHO
Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) can be used to produce
images of the extended solar corona in several ultraviolet spectral
lines. The images are produced by scanning coronal images across the
spectrometer entrance slits. The slits intercept a 40 arcminute slice of
the corona parallel to the limb tangent. Telescope mirror motions can
be used to scan from about 1.25 to 10 R_⊙. The instrument is rolled
about its Sun-center axis to obtain images of the full corona. The
spatial resolution depends on the selected slit width and the combined
resolution of the spectrometer and XDL detectors. It is limited by
diffraction for observations near the Sun where only a narrow strip of
the telescope mirror is unvignetted by the external occulter. Images
of equatorial streamers in HI Lyman-alpha and beta, and in O VI 103.2
nm will be presented. Ultraviolet images of polar plumes will also be
provided. In some cases, interpolation techniques are used to fill-in
gaps in the raster pattern. This research is supported by NASA Contract
NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian
Space Agency and by Switzerland.
Title: Coordinated SOHO Observations of Polar Plumes: Ultraviolet
Spectroscopy with UVCS
Authors: Fineschi, S.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Giordano, S.; Romoli,
M.; Benna, C.; Ciaravella, A.; Naletto, G.; Nicolosi, P.; Raymond,
J. C.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.
Bibcode: 1996AAS...188.3704F
Altcode: 1996BAAS...28..877F
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) observed polar
plumes at the south polar coronal hole on 7 March 1996. Observations
were made in H I Ly-alpha, Ly-beta and O VI 103.2 and 103.7
nm. Heliocentric heights from 1.5 to 3.2 R_⊙ were observed. In
addition, HI Ly-alpha observations with 60 sec time resolution were
obtained at a heliocentric height of 1.6 solar radii. The polar plumes
are clearly distinguishable in both H I Ly-alpha and O VI. These
measurements were made in coordination with time resolved magnetograms
by the Michelson Doppler Imager (MDI) and time resolved XUV images
by the Extreme-Ultraviolet Imaging Telescope (EIT). This work is
supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical
Observatory, by the Italian Space Agency and by Switzerland.
Title: First Results from the SOHO Ultraviolet Coronagraph
Spectrometer
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.;
Giordano, S.; Karovska, M.; Michels, J.; Naletto, G.; Nicolosi, P.;
Poletto, G.; Pernechele, C.; Raymond, J. C.; Romoli, M.; Siegmund,
O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.
Bibcode: 1996AAS...188.4906K
Altcode: 1996BAAS...28R.897K
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used
to observe the extended solar corona from 1.25 to 10 R_⊙ from Sun
center. Initial observations of polar coronal holes, polar plumes,
equatorial streamers and the diffuse mid-latitude corona will be
presented. The observations include measurements of spectral line
profiles for HI Lyman alpha and beta, and O VI 103.2 and 103.7
nm. Line intensities for Mg X 61.0 nm, Si XII 49.9 and 52.0 nm,
S X 119.6 nm, Fe XII 124.2 nm and several other minor ions have been
observed. Observations with moderate time resolution (about 1 minute) at
one strip of the corona will also be presented. Preliminary results for
derived proton and O VI velocity distributions and initial indications
of outflow velocities for protons, and O VI will be discussed as
well as preliminary results for other spectroscopic diagnostics
techniques. This research is supported by NASA Contract NAS5-31250 to
the Smithsonian Astrophysical Observatory, by the Italian Space Agency
and by Switzerland.
Title: Coronal Emission Lines with UVCS
Authors: Raymond, J. C.; Noci, G.; Kohl, J. L.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Benna, C.; Ciaravella, A.; Fineschi, S.;
Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Romoli, M.;
Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.; Martin, R.
Bibcode: 1996AAS...188.3702R
Altcode: 1996BAAS...28Q.877R
The Ultraviolet Coronagraph Spectrometer aboard the SOHO satellite has
observed the extended solar corona in H I Lyalpha and O VI lines for
coronal diagnostics, but other, fainter, lines are also present. We
discuss a spectral atlas obtained from emission in equatorial streamers
and above solar active regions, pointing out lines which are especially
useful for determining the elemental abundances, ionization state,
and density of the emitting plasma. This work is supported by NASA
under contract NAS5-31250 to the Smithsonian Astrophysical Observatory.
Title: Intercalibration and Co-Registration of the LASCO, UVCS and
SUMER instruments on SOHO
Authors: Michels, J.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello,
G.; Huber, M. C. E.; Curdt, W.; Hollandt, J.; Lemaire, P.; Schuhle,
U.; Wilhelm, K.; Korendyke, C.; Moran, T.; Raymond, J. C.; Romoli,
M.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano,
S.; Naletto, G.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Smith,
P. L.; Strachan, L.
Bibcode: 1996AAS...188.3706M
Altcode: 1996BAAS...28..878M
Joint observations of equatorial streamers by three SOHO instruments
have been used for radiometric intercalibration, co-registration and
other spectroscopic comparisons. The results are used to track the
stability of the radiometric calibrations of the Ultraviolet Coronagraph
Spectrometer (UVCS) and the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) experiment at overlapping wavelenghs. Observations
of equatorial streamers at heliocentric heights from 1.25 to 1.5
R_⊙ are used for the intercalibrations. The results are compared to
pre-launch laboratory calibrations and to observations of stars. The
first stellar observation was for 38 AQI. These UV observations are
compared to coronal green line (Fe XIV) observations obtained with the
Large Angle Spectrometric Coronagraph (LASCO) C1 coronagraph obtained
in the same time frame. Intercomparisons of spectral line profiles
among LASCO, SUMER, and UVCS are also planned. The LASCO research is
supported by NASA Grant NDPR S92835D; the UVCS research is supported by
NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
by the Italian Space Agency and by Switzerland, and SUMER is financially
supported by BMFT/DARA, CNES, NASA and PRODEX (Swiss Contribution).
Title: Non-thermal velocities in flare plasmas
Authors: Antonucci, E.; Benna, C.; Dodero, M. A.; Martin, R.
Bibcode: 1996AdSpR..17d..47A
Altcode: 1996AdSpR..17...47A
The analysis of the profile and intensity of the soft X-ray lines
formed in the wavelength range from 1.8 Angstroms to 20 Angstroms,
observed with the Soft X-ray Polychromator of the Solar Maximum Mission
(SMM), shows that solar flare plasmas are characterized by non-thermal
velocities. Flare plasmas in general consist of two components at
different temperatures: 5-8 10^6 K and 16-25 10^6 K, respectively. The
non-thermal mass motions observed in the hotter component are affected
by higher velocities and they depend on temperature in a way which is
varying with the flare phase. The results obtained for flare plasmas
are consistent with the functional relationship between temperature
and non-thermal velocity derived for the lower temperature regimes
existing in the upper chromosphere, in the transition region and in
the non-flaring corona.
Title: SIMURIS: a UV and XUV Mission for high resolution solar physics
Authors: Damé, L.; Derrien, M.; Kozlowski, M.; Antonucci, E.;
Ragazzoni, R.; Tondello, G.
Bibcode: 1996AdSpR..17d.377D
Altcode: 1996AdSpR..17..377D
Advances in electronics and servo-control allow to envisage extremely
high spatial resolution observations of the Sun through the use of
a compact array of phased telescopes. We present the SIMURIS Mission
(Solar Interferometric Mission for Ultrahigh Resolution Imaging and
Spectroscopy) which is the first to propose high resolution ultraviolet
imaging coupled to high time and spectral resolutions through the
use of an interferometric array of five 20 cm telescopes feeding a
subtractive double monochromator tunable over a large spectral range
and providing narrow band filtergrams. In addition to the ultraviolet
imaging interferometer SIMURIS has soft X-ray and EUV imagers and
spectrometers for complete coverage of the solar atmosphere.
Title: Interpretation of the Observed Plasma ``Turbulent'' Velocities
as a Result of Magnetic Reconnection in Solar Flares
Authors: Antonucci, Ester; Benna, Carlo; Somov, Boris V.
Bibcode: 1996ApJ...456..833A
Altcode:
One of the distinctive features of magnetic reconnection in current
sheets, which has been proposed as the primary energy source in
solar flares, is the presence of fast plasma outflows, or jets, whose
velocities are nearly equal to the Alfvén speed and depend mainly on
the electron and ion temperatures inside the current sheet. We briefly
discuss the outflows that originate during the reconnection process in
the high-temperature turbulent current sheet (HTTCS) approximation,
both for preflare and "hot" phase conditions. Outflows can give rise
to plasma velocity distributions with equal and opposite components
along the line of sight, and therefore they can, in this way, create
a symmetric, nonthermal broadening in the soft X-ray lines observed
during solar flares. A comparison of the nonthermal profiles of the
Fe xxv emission lines observed at flare onset with the predictions of
the HTTCS model suggests that the observed nonthermal broadenings are
consistent with the presence in the flare region of several small-scale
or one (or a few) curved, large-scale reconnecting current sheets
with internal temperature ≤8 x 107 K. The velocities of
the outflows at the emergence of the reconnecting current sheets are
inferred to be ≤ 1100 km s-1.
Title: The Ultraviolet Coronagraph Spectrometer for the Solar and
Heliospheric Observatory
Authors: Kohl, J. L.; Esser, R.; Gardner, L. D.; Habbal, S.; Daigneau,
P. S.; Dennis, E. F.; Nystrom, G. U.; Panasyuk, A.; Raymond, J. C.;
Smith, P. L.; Strachan, L.; Van Ballegooijen, A. A.; Noci, G.;
Fineschi, S.; Romoli, M.; Ciaravella, A.; Modigliani, A.; Huber,
M. C. E.; Antonucci, E.; Benna, C.; Giordano, S.; Tondello, G.;
Nicolosi, P.; Naletto, G.; Pernechele, C.; Spadaro, D.; Poletto, G.;
Livi, S.; Von Der Lühe, O.; Geiss, J.; Timothy, J. G.; Gloeckler,
G.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, O. H. W.;
Fowler, W.; Fisher, R.; Jhabvala, M.
Bibcode: 1995SoPh..162..313K
Altcode:
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is composed of
three reflecting telescopes with external and internal occultation and
a spectrometer assembly consisting of two toric grating spectrometers
and a visible light polarimeter. The purpose of the UVCS instrument is
to provide a body of data that can be used to address a broad range
of scientific questions regarding the nature of the solar corona and
the generation of the solar wind. The primary scientific goals are
the following: to locate and characterize the coronal source regions
of the solar wind, to identify and understand the dominant physical
processes that accelerate the solar wind, to understand how the coronal
plasma is heated in solar wind acceleration regions, and to increase the
knowledge of coronal phenomena that control the physical properties of
the solar wind as determined byin situ measurements. To progress toward
these goals, the UVCS will perform ultraviolet spectroscopy and visible
polarimetry to be combined with plasma diagnostic analysis techniques
to provide detailed empirical descriptions of the extended solar corona
from the coronal base to a heliocentric height of 12 solar radii.
Title: Ultraviolet Coronagraph Spectrometer for the Solar and
Heliospheric Observatory: instrument description and calibration
overview
Authors: Kohl, J. L.; Esser, R.; Gardner, Larry D.; Habbal, S.;
Daigneau, P. S.; Nystrom, George U.; Raymond, John C.; Strachan,
Leonard; van Ballegooijen, A. A.; Noci, G.; Fineschi, Silvano; Romoli,
Marco; Ciaravella, A.; Modigliani, A.; Huber, Martin C.; Antonucci, E.;
Benna, C.; Giordano, S.; von der Luehe, Oskar; Tondello, Giuseppe;
Nicolosi, Piergiorgio; Naletto, Giampiero; Pernechele, Claudio;
Geiss, J.; Gloeckler, G.; Poletto, G.; Spadaro, D.; Allegra, A.;
Basile, G.; Brusa, R.; Wood, B.; Siegmund, Oswald H.
Bibcode: 1995SPIE.2517...40K
Altcode:
The SOHO ultraviolet coronagraph spectrometer (UVCS/SOHO) is
composed of three reflecting telescopes with external and internal
occultation and a spectrometer assembly consisting of two toric grating
spectrometers and a visible light polarimeter. The UVCS will perform
ultraviolet spectroscopy and visible polarimetry to be combined with
plasma diagnostic analysis techniques to provide detailed empirical
descriptions of the extended solar corona from the coronal base to a
heliographic height of 12 R. In this paper, the salient features of
the design of the UVCS instrument are described. An overview of the
UVCS test and calibration activities is presented. The results from
the calibration activity have demonstrated that the UVCS can achieve
all its primary scientific observational goals.
Title: Differential Emission Measure and Iron-to-Calcium Abundance
in Solar Flare Plasmas
Authors: Antonucci, Ester; Martin, Renato
Bibcode: 1995ApJ...451..402A
Altcode:
The temperature distribution of the coronal plasma during solar flares
is studied for a set of energetic events of class M and X observed
with the bent crystal spectrometer (BC S) flown on the Solar Maximum
Mission (SMM) satellite. From the analysis of Ca XIX and Fe XXV spectra,
emitted in the regions from 3.165 to 3.231 Å and from 1.840 to 1.894
Å, respectively, we can derive different indicators of the thermal
conditions of the flare plasma: the temperature TCa,Fe,
derived from the ratio of the intensities of the Ca XIX and Fe XXV
resonance lines, and the temperatures Tca and TFe
obtained from the ratio of the dielectronic satellites to the resonance
line in the Ca XIX and Fe XXV spectrum. In most of the analyzed
flares, the temperature indicators TCa,Fe, Tca,
and TFe are considerably different. Our study shows that
a difference in Tca, and TFe is a signature of
departure from quasi-isothermal conditions and the variability from
flare to flare of the quantity TCa,Fe is a signature of the
variability of the iron to calcium relative abundance. We develop a
model of plasma differential emission measure which allows us to account
for the enhancements of TFe with respect to Tca by
assuming the presence of a "superhot" component at temperature greater
than 20 × 106 K. The difference of the observed value of
TCa,Fe and that derived from the model can be accounted for
by varying the relative abundance of iron to calcium. By applying this
model to the observations in a few relevant cases, we infer that the
"superhot" component in the flare plasma can be at temperatures within
7.3-8.0 in log T, and that the iron to calcium relative abundance with
respect to the photospheric Fe/Ca abundance ratio is within 0.4 and
2.3. Hence, on the basis of their chemical abundances we can identify
Fe-rich flares and Ca-rich flares.
Title: Variations in iron and calcium abundances during solar flares
Authors: Antonucci, E.; Martin, R.
Bibcode: 1995AdSpR..15g..37A
Altcode: 1995AdSpR..15...37A
Evidence for variations in iron and calcium abundances during the
impulsive phase of solar flares has been obtained by analyzing the Ca
XIX and Fe XXV spectra, detected with the Bent Crystal Spectrometer
of the Solar Maximum Mission. The plasma thermal conditions have been
investigated by considering different temperature indicators: namely,
the temperatures T_Ca and T_Fe, derived from the intensity ratios of
the dielectronic recombination satellites to the resonance line, and
the temperature T_Ca,Fe, calculated from the ratio of the resonance
lines of Ca XIX and Fe XXV, which is also depending on the Fe/Ca
abundance ratio. The observed values of T_Ca and T_Fe can be ascribed
to the specific characteristics of the plasma thermal distribution,
the corresponding values of T_Ca,Fe can be explained by allowing
also for variations in the Fe/Ca abundance ratio relative to the
photospheric ratio by a factor within 0.2 and 2.4. According to the
observed abundance variations, the events analyzed can be divided in
Ca-rich and Fe-rich flares.
Title: The Ultraviolet Coronagraph Spectrometer for the Solar and
Hellospheric Observatory
Authors: Raymond, J. C.; Kohl, J. L.; Esser, R.; Gardner, L. D.;
Habbal, S.; Strachan, L.; van Ballegooijen, A. A.; Noci, G.; Fineschi,
S.; Romoli, M.; Huber, M. C. E.; Antonucci, E.; Benna, C.; von der
Luhe, O.; Naletto, G.; Nicolosi, P.; Pernechele, C.; Tondello, G.;
Geiss, J.; Gloeckler, G.; Spadaro, D.; Daigneau, P. S.; Nystrom,
G. U.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, O. H. W.
Bibcode: 1995SPD....26..720R
Altcode: 1995BAAS...27..970R
No abstract at ADS
Title: Study of the reflectivity in the XUV domain of normal incidence
multilayer mirrors
Authors: Dodero, M. A.; Antonucci, E.; Marocchi, D.; Martin, R.
Bibcode: 1995NCimD..17..999D
Altcode:
No abstract at ADS
Title: The Ultraviolet Coronagraph Spectrometer
Authors: Noci, G.; Kohl, J. L.; Huber, M. C. E.; Antonucci, E.;
Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Raymond,
J. C.; Romoli, M.; Spadaro, D.; Strachan, L.; Tondello, G.; van
Ballegooijen, A.
Bibcode: 1995LNP...444..261N
Altcode: 1995cmer.conf..261N
The Ultraviolet Coronagraph Spectrometer (UVCS) is an instrument onboard
the Solar and Heliospheric (SOHO) spacecraft, a joint ESA/NASA mission
to be launched in 1995. The UVCS will provide ultraviolet spectroscopic
measurements to determine the primary plasma parameters of the solar
corona (temperatures, densities, velocities), from its base to as high
as 10 R⊙. We review briefly, here, its science objectives
and give an instrument description.
Title: Temperature Dependence of Nonthermal Motions in Solar Flare
Plasmas Observed with the Flat Crystal Spectrometer on SMM
Authors: Antonucci, Ester; Dodero, Maria Adele
Bibcode: 1995ApJ...438..480A
Altcode:
We have analyzed the intensities and profiles of a number of soft
X-ray lines, O VIII, Ne IX, Mg XI, Si XIII, S XV, Ca XIX, Fe XXV,
which have been observed during solar flares with the Flat Crystal
Spectrometer (FCS) of the Solar Maximum Mission (SMM). These lines
are emitted in the temperature range from 3 x 106 K to 5 x
107 K. The temperature distribution of the flare plasma,
phi (T), computed on basis of the FCS line intensities, consists of
two plasma components at different temperatures, 5-8 x 106
K and 16-25 x 106 K, respectively, in agreement with
previous studies. Significant nonthermal motions in the flare plasma
are inferred from the presence of nonthermal broadenings in the
observed lines. The broadening is deduced by comparing observed
profiles to synthetic ones derived using the differential emission
measure calculated from a series of FCS line intensities. The Doppler
temperature TD inferred from the observed line width is found
to exceed systematically the average temperature of line formation,
Te, characterizing the width of the reconstructed thermal
lines. Lines formed predominatly in the lower temperature, 'quasi-hot'
plasma component yield an average nonthermal velocity vnt
= 64 +/- 3 km/s, which is independent, within the statistical errors,
of the temperature of line formation. The nonthermal motions found
in the higher temperature, 'hot' flare plasma are characterized by
a higher velocity with a value which is an increasing function of
temperature. There is a tendency for the temperature dependence of
the nonthermal velocities to be stronger earlier in the flare and to
decrease during the flare decay. We also find that the increase of
nonthermal motions with temperature is a more general characteristic of
the solar atmosphere. The law vnt = 0.41 x T0.32
km/s is valid from the velocity of the nonthermal plasma motions and
temperature, indicating a positive correlation both locally in flare
plasmas and throughout the solar atmosphere, supports the idea that
nonthermal velocities are very likely a manifestation of the heating
process.
Title: UV lines emitted from plasma accelerated during magnetic
reconnection
Authors: Antonucci, E.; Dodero, M. A.; Somov, B. V.; Verneta
Bibcode: 1995NCimD..17.1149A
Altcode:
No abstract at ADS
Title: UVCS Science from SOHO
Authors: Antonucci, E.; Kohl, J. L.; Noci, G.; Huber, M. C. E.;
Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Pernechele,
C.; Raymond, J. C.; Romoli, M.; Spadaro, Daniele; Strachan, L.;
Tondello, G.; van Ballegooijen, A.
Bibcode: 1995jena.conf...80A
Altcode:
The ultraviolet Coronagraph Spectrometer (UVCS), to be launched on
board SOHO in 1995, has been designed to determine the primary plasma
parameters in order to obtain a far more complete description of the
coronal plasma than presently exists. This will be accomplished by
obtaining ultraviolet spectroscopic observations in some EUV lines (HI
Ly Alpha, O VI, Mg X, Si XII, Fe XII) and in the visible continuum,
form the base of the solar corona to as high as 12 solar radii. The
profiles and intensities of the measured UV lines are sensitive
to effective temperature of protons, minor ions and electrons; ion
densities; chemical abundances; and outflow velocities of protons and
ions into the solar wind. The electron density is determined by means
of white light observations. The UVCS data will be used to address a
broad range of scientific questions concerning the nature of the solar
corona and the generation of the solar wind. The primary scientific
objectives are in fact those of identifying the source regions of the
slow and fast solar wind, understanding the dominant processes that
accelerate the solar wind, and the mechanisms for heating the coronal
plasma in the extended corona.
Title: Nonequilibrium ionization and electron density in the coronal
plasma during solar flares
Authors: Marocchi, D.; Antonucci, E.; McWhirter, R. P. W.
Bibcode: 1995NCimD..17.1139M
Altcode:
No abstract at ADS
Title: UVCS/SOHO capability for determining coronal conditions before,
during and after CMEs
Authors: Strachan, L.; Raymond, J. C.; Kohl, J. L.; Noci, G.;
Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Gardner,
L. D.; Nicolosi, P.; Romoli, M.
Bibcode: 1994ESASP.373..421S
Altcode: 1994soho....3..421S
No abstract at ADS
Title: Manifestation of magnetic reconnection in coronal streamer
current sheets
Authors: Verneta, A. I.; Antonucci, E.; Marocchi, D.
Bibcode: 1994SSRv...70..299V
Altcode:
We investigate the possibility of observing the effects of magnetic
reconnection inside a current sheet forming in a coronal streamer in
the extended corona. In particular we study the possibility to observe
with the UVCS of SOHO the excitation of the tearing instability in
the current sheet.
Title: Book-Review - Solar Corona and Solar Wind
Authors: Antonucci, E.; Somov, B. V.; Phillips, K.
Bibcode: 1994Obs...114..238A
Altcode:
No abstract at ADS
Title: SOHO contribution to the understanding of mass supply and
flows in the solar corona
Authors: Antonucci, E.
Bibcode: 1994SSRv...70..149A
Altcode:
We expect a variety of dynamic phenomena in the ‘quiescent’
non-flaring corona. Plasma flows, such as siphon flows or convective
flows of chromospheric material evaporating into the corona, are
expected whenever a pressure differences is established either between
the footpoints or between the coronal and chromospheric segments of a
coronal loop. Such flows can induce phenomena of spatial and temporal
brightness variability of the corona. In particular, evaporation induces
a net mass input into the corona and consequently coronal density
enhancements. Flows are also expected in the regions where energy is
released during magnetic reconnection. From the observational point
of view the dynamics of the solar atmosphere has been investigated
in great detail mostly in the lower transition region with the HRTS,
and during flares with theSolar Maximum Mission andYohkoh. The high
spectral, temporal and spatial resolution of theSOHO ultraviolet
spectrometers should enable us in the near future to fill the gap
providing a continuous coverage from the chromosphere to the corona,
in the 104 106 K domain, and therefore to best
study the dynamics throughout the solar atmosphere.
Title: Non-Thermal Line Broadenings as Signature of Magnetic
Reconnection in Solar Flares
Authors: Antonucci, E.; Dodero, M. A.; Somov, B. V.
Bibcode: 1994xspy.conf..333A
Altcode:
No abstract at ADS
Title: Variations of the Coronal Radiation in X-ray Related to
Coronal Holes, Active Region Loop Systems, Bright Points
Authors: Antonucci, E.
Bibcode: 1994svsp.coll..159A
Altcode: 1994IAUCo.143P.159A
No abstract at ADS
Title: Simulations of the CA XIX Spectral Emission from a Flaring
Solar Coronal Loop. II. Impulsive Heating by Accelerated Electrons
Authors: Antonucci, E.; Dodero, M. A.; Martin, R.; Peres, G.; Reale,
F.; Serio, S.
Bibcode: 1993ApJ...413..786A
Altcode:
In this paper we analyze the response of the plasma inside a coronal
loop to the passage of a beam of accelerated electrons and study it
systematically as a function of the parameters and temporal profile
of the beam, as well as of the initial conditions of the corona. Our
approach consists in computing the spectral emission from an impulsively
heated loop in the Ca XIX line complex in the range 3.165-3.231 A and
in analyzing the simulated spectra with the same technique used for
the observations. This allows a direct comparison of the simulations
with the results of the spectral observations of the Bent Crystal
Spectrometer on board the SMM. While in some cases the values and
evolution of average plasma properties, as derived from the analysis
of spectra, are reproduced with good accuracy, the detailed shape of
the Ca XIX lines cannot be accurately reproduced by this kind of model
of flares heated by nonthermal electron beams.
Title: Plasma Temperature Distribution during the Impulsive Phase
of Solar Flares
Authors: Martin, R.; Antonucci, E.; Somov, B. V.
Bibcode: 1993ASSL..183..175M
Altcode: 1993pssc.symp..175M
No abstract at ADS
Title: Non-Thermal Line Profiles in Solar Flares
Authors: Antonucci, E.; Dodero, M. A.; Somov, B. V.
Bibcode: 1993ASSL..183..179A
Altcode: 1993pssc.symp..179A
No abstract at ADS
Title: Soft X-ray Line Shifts as Signature of the Flare Heating
Process
Authors: Antonucci, E.; Dodero, M. A.; Peres, G.; Reale, F.; Serio,
S.; Somov, B. V.
Bibcode: 1993ASSL..183..159A
Altcode: 1993pssc.symp..159A
No abstract at ADS
Title: A diagnostic method for reconnecting magnetic fields in the
solar corona.
Authors: Antonucci, Ester; Somov, Boris V.
Bibcode: 1992ESASP.348..293A
Altcode: 1992cscl.work..293A
One of the distinctive features of reconnecting magnetic fields in a
current sheet in the solar corona is the presence of plasma outflows,
whose velocity depends on the plasma temperature inside the current
sheet itself. The outflowing plasma is characterized by a symmetric
velocity distribution along the line-of-sight. Therefore the ultimate
observational effect of magnetic reconnection is a non-thermal
broadening in the emission spectral lines. If reconnection occurs
in a pre-flare active region, one expects an observable non-thermal
boradening in the XUV lines formed at a few million degrees. The
non-thermal profile of the individual spectral lines observed with
SOHO can be computed as a function of the temperature inside the
current sheet.
Title: EUV complementary instrumentation for SIMURIS.
Authors: Antonucci, Ester
Bibcode: 1992ESASP.344..215A
Altcode: 1992spai.rept..215A
High resolution imaging of the high-temperature solar atmosphere can be
achieved by the X-ray Ultraviolet Imager, a normal incidence telescope
with mirrors coated with multilayers, designed to provide observations
at the sub-arcsecond spatial resolution in the X-ray/XUV domain. The
X-ray Ultraviolet Imager is a multimirror telescope with a number of
independent channels imaging at different wavelengths. Each channel
is optimized to select a narrow spectroscopic band in the 40 - 400 A
region, which is rich in diagnostic lines formed at quite different
temperatures. The number of channels is chosen in such a way to cover
the entire temperature range observed in the solar outer atmosphere,
from 105 to a few 107K. The instrument consists
of two complementary imaging systems: a high resolution telescope with
sub-arcsecond resolution on a limited field of view, and a wide field
telescope imaging the whole sun within 2.5 Rsun.
Title: The X-ray ultraviolet imager for the orbiting solar laboratory
Authors: Antonucci, Ester; Malvezzi, Marco; Ciminiera, Luigi; Angrilli,
Francesco; Bruner, Marilyn E.; Perona, Giovanni; Adele Dodero, Maria;
Evans, Brian L.; Golub, Leon; Landini, Massimo; Noci, Giancarlo;
McWhirter, Peter; Fossi, Brunella Monsignori; Poletto, Giannina;
Neidig, Donald F.; Schmidt, Wolfgang K. H.; Thomas, Roger J.;
Tondello, Giuseppe
Bibcode: 1992AIPC..267..126A
Altcode: 1992ecsa.work..126A
A normal incidence multimirror telescope, the X-ray Ultraviolet
Imager, for high resolution imaging of the solar atmosphere in the
soft X-ray/XUV region, is being developed as part of the scientific
payload of the NASA Orbiting Solar Laboratory. The X-ray Ultraviolet
Imager is formed by two units: a high resolution telescope (0.25
arcsec pixel size and 8×8 arcmin2 field of view) and a wide field one
(2.3 arcsec pixel size and 5×5 solar radii2 field of view). The two
systems complement each other and allow a full coverage of solar
features from the small scale (200 km on the sun) to the global
phenomena. Each system consists of 8 channels with multilayer mirrors,
imaging at different wavelengths. In each channel the mirror coating
is optimized to select a narrow spectroscopic window corresponding to
an intense line in the region 40-400 A˚. In order to provide imaging
and temperature diagnostics from the chromosphere to the upper corona,
8 wavelengths are chosen to cover the broad temperature range from 105
to 107 K. Four images, two high resolution and two full disk ones,
are simultaneously obtained by the X-ray Ultraviolet Imager, at a
cadence which in flares can be of 0.4-1 s.
Title: Solar corona and solar wind. Proceedings. Symposium 9 of the
COSPAR 28. Plenary Meeting: Solar corona and solar wind, The Hague
(Netherlands), 25 Jun - 6 Jul 1990.
Authors: Antonucci, E.; Somov, B. V.
Bibcode: 1991AdSpR..11a....A
Altcode: 1991AdSpR..11Q....A
This publication is an attempt to summarize our present knowledge of the
physics of the solar corona from both the theoretical and experimental
points of view and to present the future space experiments for the
observation of the corona. The first part is a review of the current
status of coronal physics. This is followed by a discussion of the
development of diagnostic methods to measure the plasma conditions in
the corona, and of the new coronagraphic techniques to be used in the
experiments planned for the space missions of the 1990's. Last is a
report, although not complete, of the space experiments planned for
the next decade to study the physics of the solar corona, the inner
heliosphere and the solar wind.
Title: Velocity-Temperature Distribution in the Evaporating Plasma
during the Impulsive Phase of Solar Flares: Erratum
Authors: Antonucci, E.; Dodero, M. A.; Martin, R.
Bibcode: 1990ApJS...74..830A
Altcode:
No abstract at ADS
Title: Rotation of the Photospheric Magnetic Fields: A North-South
Asymmetry
Authors: Antonucci, E.; Hoeksema, J. T.; Scherrer, P. H.
Bibcode: 1990ApJ...360..296A
Altcode:
During most of solar cycle 21 the large-scale photospheric field rotated
more rapidly in the Northern Hemisphere than in the southern. The
large-scale northern field rotated with a 26.9 day period (synodic),
was centered at 15 degrees N, and covered a latitude zone about 24
degrees wide. The large-scale southern field rotated with a periodicity
of 28.1 days, was centered at 26 degrees S, and covered a latitude
zone about 32 degrees wide. Our analysis showed rotational power at
only a few discrete latitudes and frequencies in each hemisphere. The
center of each peak lies near to the sunspot differential rotation
curve. The largest scale field contributes to the configuration of the
coronal and interplanetary magnetic field (IMF). The strength of the
first harmonic of the northern field suggests that this structure may
be related to the 4-sector pattern observed in the IMF polarity. The
southern field had much lower power at the first harmonic of the solar
rotation rate and so would contribute only to a 2-sector structure
in the IMF. These results were discovered in Fourier analysis of
photospheric synoptic charts obtained at the Wilcox Solar Observatory
from 1976 to 1986 and confirmed in higher resolution maps from the
National Solar Observatory. Mt. Wilson magnetic field measurements
from solar cycle 20 show a similar north-south asymmetry.
Title: Velocity-Temperature Distribution in the Evaporating Plasma
during the Impulsive Phase of Solar Flares
Authors: Antonucci, E.; Dodero, M. A.; Martin, R.
Bibcode: 1990ApJS...73..147A
Altcode:
A combined analysis of the Ca SIS and Fe SSV spectra obtained by the
SMM bent crystal spectrometer is used to study the velocity-temperature
distribution in the plasma evaporating from the chromosphere during
the impulsive phase of solar flares. The velocity distributions
from the Ca XIX spectra have a maximum velocity of 500 km/s, while
those from the Fe XXV spectra extend to a maximum of 800 km/s. It
is shown that the evaporating plasma is not in isothermal conditions
and that the material flowing at higher velocity is characterized by
higher temperatures. Observed and simulated velocity distributions
are compared. The results imply that high evaporation velocities are
caused by chromospheric heating with an energy flux which exceeds 10
to the 10th ergs/sq cm s.
Title: High-Velocity Evaporation during the Impulsive Phase of the
1984 April 24 Flare
Authors: Antonucci, E.; Dodero, M. A.; Martin, R.
Bibcode: 1990ApJS...73..137A
Altcode:
An analysis is given of the soft X-ray emission, detected with the
bent crystal spectrometer of the SMM, during the initial part of the
impulsive phase of the April 24, 1984 flare. In this period, soft X-rays
are emitted uniquely by a moving source, which can be identified with
plasma evaporating from the chromosphere with velocities between 100
and 800 km/s, and they can be characterized by temperatures between 1.5
x 10 to the 7th and 4 x 10 to the 7th K. Three successive injections
of evaporating plasma can be clearly distinguished. A mass and energy
balance analysis ensures that plasma is almost continuously injected
in the flaring loops during the period of observation of upflows.
Title: The XUV imager for the OSL.
Authors: Landini, M.; Noci, G.; Antonucci, E.; Bruner, M. E.; Evans,
B. L.; Golub, L.; Malvezzi, M.; McWhirter, R. W.; Monsignori Fossi,
B. C.; Poletto, G.; Neidig, D.; Perona, G.; Thomas, R.; Tondello, G.
Bibcode: 1990BAAS...22.1148L
Altcode:
No abstract at ADS
Title: X-ray spectral synthesis in hydrodynamic flare models
Authors: Serio, S.; Antonucci, E.; Dodero, M. A.; Peres, G.; Reale, F.
Bibcode: 1990hrxr.conf..126S
Altcode: 1990IAUCo.115..126S
Compact solar flares are triggered by sudden energy release in
magnetically confined plasma. This class of flares is well suited
to be studied with numerical hydrodynamic models. In particular,
it is possible to compare the evolution of observed and synthetic
X-ray spectra, computed under various assumptions for the mechanism
of impulsive energy deposition, to constrain theoretical models and
their parameter space. Recent results on solar flares along this line,
nonthermal to models of energy depositions by relativistic electron
beams are discussed. Possible applications of X-ray spectral synthesis
to stellar flares are also discussed.
Title: Observations of energy conversion in the solar flare plasma
Authors: Antonucci, E.; Dodero, M. A.; Martin, R.
Bibcode: 1990AdSpR..10i..91A
Altcode: 1990AdSpR..10...91A
Soft x-ray spectroscopic observations give evidence for magnetic
energy conversion in the solar atmosphere during flares. Non-thermal
broadenings and blue-shifted components, observed in hot emission
lines during the impulsive phase of flares, can be interpreted as a
manifestation of magnetic energy conversion and of energy transport from
the primary energy release site to the chromosphere, respectively. Large
non-thermal broadenings in soft x-ray lines emitted from the coronal
plasma are observed in the period immediately preceding the onset
of solar flares and during the flare impulsive phase, suggesting a
relation to the initiation of the primary process of energy release
and particle acceleration. Non-thermal broadenings can be interpreted
as turbulent mass motions in the regions where magnetic reconnection
occurs. Blue wings in soft x-ray lines appear at the onset of flares,
as evidence for chromospheric evaporation, in coincidence with the
onset of the impulsive phase of energy release. The dynamics of the
evaporating plasma depends on the mechanism of chromospheric heating,
and, in turn, on the form of energy which is predominant in the
coronal loops as a result of the primary energy release. The observed
evaporation velocities suggest that particle beams play a dominant
role in transferring energy along the loop, at least in large flares.
Title: Rotation of the photospheric magnetic fields: A north-south
asymmetry
Authors: Antonucci, E.; Hoeksema, J. T.; Scherrer, P. H.
Bibcode: 1989STIN...9014177A
Altcode:
During most of solar cycle 21 the large-scale photospheric field rotated
more rapidly in the Northern Hemisphere than in the southern. The
large-scale northern field rotated with a 26.9 day period (synodic),
was centered at 15 degress N, and covered a latitude zone about 24
degrees wide. The large-scale southern field rotated with a periodicity
of 28.1 days, was centered at 26 degrees S, and covered a latitude zone
about 32 degrees wide. Our analysis showed rotational power at only a
few discrete latitudes and frequencies in each hemisphere. The center
of each peak lies near the sunspot differential rotation curve. The
largest scale field contributes to the configuration of the coronal
and interplanetary magnetic field (IMF). The strength of the first
harmonic of the northern field suggests that this structure may be
related to the 4-sector pattern observed in the IMF polarity. The
southern field had much lower power at the first harmonic of the solar
rotation rate and so would contribute only to a 2-sector structure
in the IMF. These results were discovered in Fourier analysis of
photospheric synoptic charts obtained at the Wilcox Solar Observatory
from 1976 to 1986 and confirmed in higher resolution maps from the
National Solar Observatory. Mt. Wilson magnetic field measurements
from solar cycle 20 show a similar north-south asymmetry.
Title: Solar flare spectral diagnosis: Present and future
Authors: Antonucci, Ester
Bibcode: 1989SoPh..121...31A
Altcode: 1989IAUCo.104...31A
New perspectives in solar diagnosis have been opened in recent years
with the advent of high-resolution soft X-ray spectroscopy for plasmas
forming at temperatures above 107 K. The spectra obtained
with the soft X-ray spectrometers flown during the last solar maximum
on the major space missions dedicated to flares have allowed detailed
studies of the hydrodynamic response of coronal loops to impulsive
energy deposition and of the formation of the high-temperature plasma
as a consequence of such dynamic effects. These studies are possible
since high-resolution spectrometers give an accurate measure of
both line intensities and profiles in important spectral regions,
covering the emission of highly ionized heavy ions, which allow
a direct determination of most of the crucial plasma parameters in
the flare region. In response to the impulsive energy release in the
flare region, while the intensity of soft X-ray lines increases, line
profiles show large non-thermal broadenings and strong blue-asymmetries.
Title: UVCS: An Ultraviolet Coronagraph Spectrometer for SOHO
Authors: Kohl, J. L.; Hartmann, L. W.; van Ballegooijen, A. A.;
Withbroe, G. L.; Rayomnd, J. C.; Weiser, H.; Noci, G.; Antonucci,
E.; Geiss, J.; Gloeckler, G.
Bibcode: 1989ESASP1104...49K
Altcode:
The UltraViolet Coronagraph Spectrometer (UVCS) of SOHO (solar
and heliospheric observatory) provides ultraviolet spectroscopic
observations of the solar corona out to ten solar radii from
suncenter. This capability is expected to greatly expand the
number of plasma parameters that can be specified by remote sensing
techniques. Plasma diagnostic techniques are expected to provide a
sufficient number of empirically derived parameters to significantly
constrain theories of solar wind acceleration, coronal heating, and
solar wind composition. The spectral line profiles and intensities
are sensitive to random velocity distributions and to the effective
temperatures of protons, minor ions, and electrons. Ion densities,
chemical abundances, and outflow velocities of coronal protons and
ions into the solar wind are also taken into consideration.
Title: Chromospheric explosions.
Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng,
C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.;
MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust,
D. M.; Shine, R. A.
Bibcode: 1989epos.conf..303D
Altcode:
The work of this team addressed the question of the response and
relationship of the flare chromosphere and transition region to the
hot coronal loops that reach temperatures of about 107K
and higher. Flare related phenomena such as surges and sprays were
also discussed. The team members debate three main topics: 1) whether
the blue-shifted components of X-ray spectral lines are signatures of
"chromospheric evaporation"; 2) whether the excess line broadening of UV
and X-ray lines is accounted for by "convective velocity distribution"
in evaporation; and 3) whether most chromospheric heating is driven by
electron beams. These debates illustrated the strengths and weaknesses
of our current observations and theories.
Title: UVCS: an Ultraviolet Coronagraph Spectrometer for SOHO
Authors: Kohl, J. L.; Hartmann, L. W.; van Ballegooijen, A. A.;
Withbroe, G. L.; Raymond, J. C.; Weiser, H.; Noci, G.; Antonucci,
E.; Geiss, J.; Gloeckler, G.
Bibcode: 1988sohi.rept...49K
Altcode:
The UltraViolet Coronagraph Spectrometer (UVCS) of SOHO (solar
and heliospheric observatory) provides ultraviolet spectroscopic
observations of the solar corona out to ten solar radii from
sun-center. This capability is expected to greatly expand the
number of plasma parameters that can be specified by remote sensing
techniques. Plasma diagnostic techniques are expected to provide a
sufficient number of empirically derived parameters to significantly
constrain theories of solar wind acceleration, coronal heating, and
solar wind composition. The spectral line profiles and intensities
are sensitive to random velocity distributions and to the effective
temperatures of protons, minor ions, and electrons. Ion densities,
chemical abundances, and outflow velocities of coronal protons and
ions into the solar wind are also taken into consideration.
Title: The SOHO Project.
Authors: Antonucci, E.
Bibcode: 1988ASSL..142..419A
Altcode: 1988mosg.proc..419A
The model payload of the Solar and Heliospheric Observatory (SOHO),
part of the first cornerstone of the long-term ESA scientific program,
includes a package of instruments whose primary scientific goal is
the investigation of the processes leading to the formation of a
hot solar atmosphere and the generation of the solar wind. The SOHO
instrumentation will allow to establish in great detail the density and
temperature structure of the solar atmosphere and the velocity fields,
including the flow velocity of the expanding coronal plasma, from the
base of the corona up to 6 solar radii. The combined remote and 'in
situ' observations are expected to have as a result the identification
of the processes at the base of the solar wind generation.
Title: Calcium ionization balance and argon/calcium abundance in
solar flares
Authors: Antonucci, E.; Marocchi, D.; Gabriel, A. H.; Doschek, G. A.
Bibcode: 1987A&A...188..159A
Altcode:
An earlier analysis of solar flare calcium spectra from XRP and P78-1
aimed at measuring the calcium ionization balance resulted in an
ambiguity due to a line blend between the calcium q line and an Ar
XVII line. In the present work the calcium line 'r' is included in
the analysis in order to resolve this problem. It is shown that the
correct calcium ionization balance is that indicated in the earlier
paper as corresponding to an argon/calcium abundance ratio of 0.2. The
argon/calcium abundance ratio in the group of solar flares studied
is shown to be 0.2 + or - 0.2. It is further argued that while the
abundance of heavy elements may be enhanced in energetic flare events,
this enhancement is less for argon than for calcium, leading to an
argon/calcium ratio smaller than that present in the quiet sun.
Title: Simulations of the CA XIX Spectral Emission from a Flaring
Solar Crornal Loop. I. Thermal Case
Authors: Antonucci, E.; Dodero, M. A.; Peres, G.; Serio, S.; Rosner, R.
Bibcode: 1987ApJ...322..522A
Altcode:
Spectral profiles synthesized from the results of numerical simulations
of solar coronal loop plasma are compared with the observed line
profiles, and the sensitivity of this comparison to variations in
the parameter values is tested. The comparison allows the procedures
commonly adopted for obtaining temperatures and velocities directly
from the bent crystal spectrometer observations, as well as the
interpretation of parameters obtained from hydrodynamical calculations,
to be independently validated. The characteristic spectral signatures
of different models for the deposition of impulsive thermal energy
in the loop are derived assuming two distinct spatial distributions
of thermal heating: in one case, the heating function peaks near the
apex of the loop, while in the second, energy is deposited directly
in the lower atmosphere.
Title: The North-South Asymmetry in the Rotation of the Photospheric
Magnetic Field During Solar Cycles 21 and 20
Authors: Scherrer, P. H.; Hoeksema, J. T.; Antonucci, E.
Bibcode: 1987BAAS...19S.935S
Altcode:
No abstract at ADS
Title: Ionization balance for iron XXV, XXIV and XXIII derived from
solar flare X-ray spectra
Authors: Antonucci, E.; Dodero, M. A.; Gabriel, A. H.; Tanaka, K.;
Dubau, J.
Bibcode: 1987A&A...180..263A
Altcode:
An analysis has been carried out using over 300 spectra of solar
flares from both the XRP instrument on SMM and the SOX instrument on
Hinotori. The helium-like iron and associated dielectronic satellite
spectra were used in order to derive a revised ionization balance for
Fe XXIV/Fe XXV. This is found to lie between the theoretical curves
based upon ECIP ionization rates, and those using Lotz formalism, with
a tendency to be closer to the former. An extension of the analysis
to include Fe XXIII is subject to a somewhat larger uncertainty in
the interpretation. However it indicates a similar effect for this
ion. Using all three ions, a revised ionization balance for iron
is presented.
Title: Line Broadening and Magnetic Reconnection at Flare Onset
Authors: Antonucci, E.; Rosner, R.; Tsinganos, K.
Bibcode: 1987sman.work...37A
Altcode:
The onset of solar flares is characterized by large non-thermal
soft X-ray line broadening, which can be attributed to isotropic
plasma flows within localized regions of reconnecting magnetic
fields; the reconnection in turn reflects structural instability
of the quasi-equilibrium magnetohydrodynamic structure in the flare
region. The authors show these hypotheses to be consistent with solar
flare data obtained with the Solar Maximum Mission (SMM) instruments.
Title: Chromospheric explosions
Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng,
C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.;
MacNeice, P.; McWhirter, R. W. P.
Bibcode: 1986epos.conf..4.1D
Altcode: 1986epos.confD...1D
Three issues relative to chromospheric explosions were debated. (1)
Resolved: The blue-shifted components of x-ray spectral lines are
signatures of chromospheric evaporation. It was concluded that
the plasma rising with the corona is indeed the primary source of
thermal plasma observed in the corona during flares. (2) Resolved:
The excess line broading of UV and X-ray lines is accounted for by a
convective velocity distribution in evaporation. It is concluded that
the hypothesis that convective evaporation produces the observed
X-ray line widths in flares is no more than a hypothesis. It is
not supported by any self-consistent physical theory. (3) Resolved:
Most chromospheric heating is driven by electron beams. Although it
is possible to cast doubt on many lines of evidence for electron
beams in the chromosphere, a balanced view that debaters on both
sides of the question might agree to is that electron beams probably
heat the low corona and upper chromosphere, but their direct impact
on evaporating the chromosphere is energetically unimportant when
compared to conduction. This represents a major departure from the
thick-target flare models that were popular before the Workshop.
Title: On Magnetic Field Stochasticity and Nonthermal Line Broadening
in Solar Flares
Authors: Antonucci, E.; Rosner, R.; Tsinganos, K.
Bibcode: 1986ApJ...301..975A
Altcode:
Observations of nonthermal line broadening seen in solar flares by the
Solar Maximum Mission satellite are discussed in light of recent results
on the generation of magnetic field stochasticity. It is shown that a
consistent model for the data can be constructed by assuming that the
observations signal the destruction of an ambient magnetohydrodynamic
equilibrium.
Title: Coronal response to energy release during solar flares.
Authors: Antonucci, E.
Bibcode: 1986HiA.....7..731A
Altcode:
The observations obtained with high resolution spectrometers flown
in the past solar maximum, in the years 1979 - 1981, have shown that
the soft X-ray plasma during the impulsive phase of solar flares is
characterized by upflows, as well as by isotropic flows, at velocities
of a few hundred km s-1. Isotropic flows can be directly
related to the primary energy release process. While, upflows are an
indication of chromospheric material heated to coronal temperatures and
evaporating along the magnetic fluxtubes; they are therefore related
to the development of the coronal soft X-ray source in the flare region.
Title: Chromospheric explosions.
Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng,
C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.;
MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust,
D. M.; Shine, R. A.
Bibcode: 1986NASCP2439....4D
Altcode:
The work of this team addressed the question of the response and
relationship of the flare chromosphere and transition region to the
hot coronal loops that reach temperatures of about 107K
and higher. Flare related phenomena such as surges and sprays are
also discussed. The team members debated three main topics: 1. whether
the blue-shifted components of X-ray spectral lines are signatures of
"chromospheric evaporation"; 2. whether the excess line broadening of UV
and X-ray lines is accounted for by "convective velocity distribution"
in evaporation; and 3. whether most chromospheric heating is driven
by electron beams.
Title: Flare onsets in hard and soft X-rays
Authors: Machado, Marcos E.; Orwig, Larry E.; Antonucci, Ester
Bibcode: 1986AdSpR...6f.101M
Altcode: 1986AdSpR...6..101M
We show that the onset of solar flares, within <= 2 minutes before
the impulsive peaks, is characterized by an increase in high energy
emission at E < 100 keV, and strong broadening of soft X-ray lines
characteristic of the 107 K plasma already present at this
stage. The observations are interpreted in terms of the early signature
of energy release, during a phase preceding the instability that leads
to strong particle acceleration.
Title: Hydrodynamics of coronal loops: A comparison of observed and
simulated spectra emitted from flaring coronal loops
Authors: Antonucci, E.; Dodero, M. A.; Peres, G.; Serio, S.
Bibcode: 1986AdSpR...6f.151A
Altcode: 1986AdSpR...6..151A
The data obtained at high temporal and spectral resolution with
the Bent Crystal Spectrometer of the Solar Maximum Mission have
shown that the soft x-ray spectra emitted by highly ionized heavy
ions are characterised during the impulsive phase of flares by
blue-shifted components. The blue emission has been interpreted as
due to convective plasma flows from the chromosphere, which in flare
conditions is heated to coronal temperatures. In the present study,
the properties of the Ca XIX solar spectra are compared with the
results of numerical calculations simulating the behaviour of coronal
plasma subject to impulsive heating. The plasma hydrodynamic response
to transient heating is modeled in the assumption of a fluid confined
in a semicircular loop of uniform cross-section. Two different forms
of heating are considered: direct thermal heating, and heating due to
injection in the loop of non-thermal electrons.
Title: Dynamic conditions of thermal plasma in large flares.
Authors: Antonucci, Ester; Dodero, Maria Adele
Bibcode: 1986lasf.conf..363A
Altcode: 1986lasf.symp..363A
The authors present the results of a study on the dynamic conditions of
the thermal plasma at the onset of a very energetic flare observed on
April 24, 1984. The event of April 24, 1984 is an excellent case for a
study, at high time resolution (11.3 seconds), of the dynamic conditions
during flares of the high temperature plasma, since the emission is
intense even in the pre-flash phase. The information obtained from
the Ca XIX line profiles confirms the general picture of the plasma
conditions at flare onset. While the study of the Fe XXV lines shows
that it is possible to distinguish during the impulsive phase several
successive phases of injection of chromospheric material in the flare
loops, with higher velocities predominating at higher temperatures.
Title: Multiwavelength Analysis of a Well Observed Flare from Solar
Maximum Mission
Authors: MacNeice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.;
Antonucci, E.; Shine, R. A.; Rust, D. M.; Jordan, C.; Dennis, B. R.
Bibcode: 1985SoPh...99..167M
Altcode:
We describe and analyse observations of an M1.4 flare which began at 17:
00 UT on 12 November, 1980. Ground based Hα and magnetogram data have
been combined with EUV, soft and hard X-ray observations made with
instruments on-board the Solar Maximum Mission (SMM) satellite. The
preflare phase was marked by a gradual brightening of the flare site
in Ov and the disappearance of an Hα filament. Filament ejecta were
seen in Ov moving southward at a speed of about 60 km s−1,
before the impulsive phase. The flare loop footpoints brightened in Hα
and the CaXIX resonance line broadened dramatically 2 min before the
impulsive phase. Non-thermal hard X-ray emission was detected from the
loop footpoints during the impulsive phase while during the same period
blue-shifts corresponding to upflows of 200-250 km s−1
were seen in Ca XIX. Evidence was found for energy deposition in both
the chromosphere and corona at a number of stages during the flare. We
consider two widely studied mechanisms for the production of the high
temperature soft X-ray flare plasma in the corona, i.e. chromospheric
evaporation, and a model in which the heating and transfer of material
occurs between flux tubes during reconnection.
Title: On the heliolatitude distribution of galactic cosmic rays
Authors: Antonucci, E.; Attolini, M. R.; Cecchini, S.; Galli, M.
Bibcode: 1985JGR....90.7623A
Altcode:
An analysis of the annual and semiannual variation of the galactic
cosmic ray intensity has been performed for the period 1953-1979 by
using the data from the Climax and Dourbes neutron monitors. This
analysis, based on a method developed for searching periodicities and
recurrences in the cosmic ray intensity, has confirmed the existence of
such variations and their phase changes associated with the reversals
of the solar magnetic dipole. Hence the importance in the cosmic ray
transport of transverse diffusion arising from drift effects due to
the curvature and gradient of the interplanetary magnetic field is
confirmed, since this is the mechanism which can explain the dependence
on the solar magnetic cycle. Such a mechanism is effective when the
polarity configuration of the interplanetary magnetic field is well
defined and stable. A phase advance of the semiannual variation
is observed, which can be explained through the modulation of the
heliolatitude distribution of cosmic rays by the activity of the solar
magnetic regions migrating in both hemispheres toward the equator,
during the 11-year cycle of solar activity. A residual annual variation,
detectable when averaging out the effects of the magnetic cycle or when
the polarity configuration of the interplanetary magnetic field is
not well defined, probably indicates the existence of a preferential
azimuthal direction for the access of low-energy galactic cosmic rays
into the heliosphere, along the galactic magnetic field.
Title: Initial Phase of Chromospheric Evaporation in a Solar Flare
Authors: Antonucci, E.; Dennis, B. R.; Gabriel, A. H.; Simnett, G. M.
Bibcode: 1985SoPh...96..129A
Altcode:
In this paper we discuss the initial phase of chromospheric evaporation
during a solar flare observed with instruments on the Solar Maximum
Mission on May 21, 1980 at 20:53 UT. Images of the flaring region
taken with the Hard X-Ray Imaging Spectrometer in the energy bands from
3.5 to 8 keV and from 16 to 30 keV show that early in the event both
the soft and hard X-ray emissions are localized near the footpoints,
while they are weaker from the rest of the flaring loop system. This
implies that there is no evidence for heating taking place at the
top of the loops, but energy is deposited mainly at their base. The
spectral analysis of the soft X-ray emission detected with the Bent
Crystal Spectrometer evidences an initial phase of the flare, before
the impulsive increase in hard X-ray emission, during which most of
the thermal plasma at 107 K was moving toward the observer
with a mean velocity of about 80 km s-1. At this time
the plasma was highly turbulent. In a second phase, in coincidence
with the impulsive rise in hard X-ray emission during the major
burst, high-velocity (370 km s-1) upward motions were
observed. At this time, soft X-rays were still predominantly emitted
near the loop footpoints. The energy deposition in the chromosphere by
electrons accelerated in the flare region to energies above 25 keV,
at the onset of the high-velocity upflows, was of the order of 4 ×
1010 erg s-1 cm-2. These observations
provide further support for interpreting the plasma upflows as the
mechanism responsible for the formation of the soft X-ray flare,
identified with chromospheric evaporation. Early in the flare soft
X-rays are mainly from evaporating material close to the footpoints,
while the magnetically confined coronal region is at lower density. The
site where upflows originate is identified with the base of the loop
system. Moreover, we can conclude that evaporation occurred in two
regimes: an initial slow evaporation, observed as a motion of most of
the thermal plasma, followed by a high-speed evaporation lasting as
long as the soft X-ray emission of the flare was increasing, that is
as long as plasma accumulation was observed in corona.
Title: The energetics of chromospheric evaporation in solar flares
Authors: Antonucci, E.; Gabriel, A. H.; Dennis, B. R.
Bibcode: 1984ApJ...287..917A
Altcode:
The Solar Maximum Mission (SMM) spacecraft has provided high time
resolution observational data regarding the soft X-ray emission from
solar-flare plasma during 1980. The present investigation is concerned
with the characteristics of a soft X-ray flare and the energetics of
the impulsive phase on the basis of the data collected with the aid of
two of the instruments on board the SMM, taking into account the Hard
X-ray Burst Spectrometer (HXRBS) and the Bent Crystal Spectrometer
(BCS). Attention is given to an analysis of soft X-ray flare spectra,
the relative motion of the soft X-ray sources, the phenomenology of
the soft X-ray flare, energy and mass transport during the impulsive
phase, and energy deposition in the chromosphere during evaporation.
Title: Solar Maximum Mission results on the energetics of the
impulsive phase of solar flares.
Authors: Antonucci, E.; Gabriel, A. H.
Bibcode: 1984ESASP.220..279A
Altcode: 1984ESPM....4..279A
The presence of chromospheric material evaporating in response
to localized heating to coronal temperatures is inferrred from the
observations of systematic plasma upflows during the rise of the soft
X-ray emission in solar flares.
Title: Oscillations in Extreme Ultraviolet Emission Lines during a
Loop Brightening
Authors: Antonucci, E.; Gabriel, A. H.; Patchett, B. E.
Bibcode: 1984SoPh...93...85A
Altcode:
Oscillations in the emission in the ultraviolet lines of CII, OIV, and
Mg X, detected by the Harvard College Observatory EUV spectroheliometer
on Skylab are observed on August 7, 1973, during a loop brightening. The
intensity of the EUV lines varies with a period of 141 s during the
time of enhanced intensity of the coronal loop, lasting 10 min. The
periodic oscillation is not only localized in the loop region but
extends over a larger area of the active region, maintaining the same
phase. We suggest that the intensity fluctuation of the EUV lines is
caused by small-amplitude waves, propagating in the plasma confined
in the magnetic loop and that size of the loop might be important in
determining its perferential heating in the active region.
Title: Derivation of ionization balance for calcium XVIII/XIX using
XRP solar X-ray data
Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G.; Dubau, J.;
Faucher, P.; Jordan, C.; Veck, N.
Bibcode: 1984A&A...133..239A
Altcode:
Spectra of calcium from solar flares are used in an attempt to derive
an ionization balance for Ca XVIII/Ca XIX. The isothermal assumption
inherent in this derivation is shown not to introduce errors, by
modelling a number of hypothetical nonisothermal plasmas. The unresolved
blend of calcium and argon lines prevents a definitive determination of
the results, owing to uncertainties in the ratio of abundances of these
elements. The resulting ionization balance curves are presented as a
function of the solar argon/calcium abundance ratio. The theoretical
ionization balance of Doyle and Raymond is consistent with the data. To
within the expected accuracy of the atomic theories, there is no reason
to assume that the flare plasma is other than close to steady-state
ionization balance.
Title: Origin and location of chromospheric evaporation in flares
Authors: Antonucci, E.; Marocchi, D.; Simnett, G. M.
Bibcode: 1984AdSpR...4g.111A
Altcode: 1984AdSpR...4..111A
Observation of two flares obtained with the Solar Maximum Mission
spectrometers indicate that at flare onset the emission in soft (3.5 -
8 keV) and hard (16 - 30 keV) X-rays is predominant at the footpoints of
the flaring loops. Since, at the same time, blue-shifts are observed in
the soft X-ray spectra from the plasma at temperature of 107
K, we infer that material is injected at high velocity into the coronal
loops from the footpoints. These areas are also the sites of energy
deposition, since their emission in hard X-rays is due to non-thermal
electrons penetrating in the denser atmosphere. Hence, chromospheric
evaporation occurs where energy is deposited. During the impulsive
phase, the configuration of the flare region changes indicating that
the flaring loop is progressively filled by hot plasma.
Title: Space programs of solar physics
Authors: Antonucci, E.
Bibcode: 1984MmSAI..55..543A
Altcode:
ESA and NASA plans for space-based observations of the sun,
primarily during its quiescent phase, are surveyed, and some results
of previous missions are summarized. Consideration is given to the
Solar and Heliospheric Observatory (SOHO) which represents the main
ESA contribution to the International Solar-Terrestrial Physics
program, the UV coronal spectrometer and other SOHO instruments,
the accomplishments of the NASA SMM spacecraft in high-energy solar
physics, lower-energy measurements being performed by SMM since its
in-orbit repair in April 1984, and the NASA Solar Optical Telescope
to be flown on several 7-10-day Shuttle missions beginning in 1992.
Title: Line broadenings and shifts during the impulsive phase
of flares
Authors: Antonucci, E.
Bibcode: 1984MmSAI..55..699A
Altcode:
A comprehensive treatment is presented of the Soft X-ray (SXR) spectral
data obtained by the Bent Crystal Spectrometer component of the
Soft X-ray Polychromator flown on the SMM satellite, with reference
to observations obtained on previous missions and in other X-ray
experiments. The topics discussed include: (1) various experiments
for flare plasma observations conducted on SMM and other satellites;
(2) high-temperature SXR spectra during the impulsive phase of plasma
flares, with particular reference to the Ca XIX spectrum; (3) general
properties of the plasma motions, as deduced from the observations
of the blue shifted components and the nonthermal line broadenings;
(4) the location of mass motions at flare onset; (5) energetics of the
impulsive phase upflows; (6) numerical simulations of the hydrodynamic
response of a coronal loop to impulsive heating; and (7) the origin
of nonthermal line profiles.
Title: Derivation of the Ionization Balance for Iron Xxiv/xxv and
Xxiii/xxiv Using Solar X-Ray Data
Authors: Antonucci, E.; Dodero, M. A.; Gabriel, A. H.; Tanaka, K.
Bibcode: 1984uxsa.coll...13A
Altcode: 1984uxsa.conf...13A; 1984IAUCo..86...13A
No abstract at ADS
Title: Microwave, ultraviolet, and soft X-Ray observations of hale
region 16898
Authors: Shibasaki, K.; Chiuderi-Drago, F.; Melozzi, M.; Slottje,
C.; Antonucci, E.
Bibcode: 1983SoPh...89..307S
Altcode:
Hale region 16898 was observed by the Westerbork Synthesis
Radio Telescope at 6 cm and by the Ultraviolet Spectrometer and
Polarimeter and the X-Ray Spectrometer on the Solar Maximum Mission
satellite. Optical pictures of the same active region were taken at
Sacramento Peak, Big Bear, and Meudon Observatories. The radio emission
mechanisms are identified by comparing radio data with ultraviolet
and soft X-ray data. The height of the radio sources and the magnetic
field strength at that height are deduced. A radio source above a large
sunspot shows a crescent shaped depression of circular polarization and
a high brightness temperature. The emission mechanism is identified
as gyroresonance at the second and the third harmonic layers and it
is found that the second harmonic layer, where the magnetic field
strength is 900 G, must be in the corona. An extended loop-like source
connecting the leading and the following part of the active region
as well as the sources associated with small spots are mainly due
to thermal free-free emission by hot and dense plasma which is also
observed in ultraviolet and soft X-ray radiation. The calculated radio
brightness temperature, using the physical parameters deduced from the
ultraviolet and soft X-ray line intensities, agrees with the observed
brightness temperature. The height of the low brightness temperature
sources above the small spots is 6000 ± 3000 km and that above the
large spot is less than 3000 km: the source above the large spot
does not show any shift relative to the sunspot due to the projection
effect. Very strong radio emission was found which was associated with
the merging of a group of small spots into the large sunspot. In the
same day, warm (≤ 106 K) and dense matter was present
above the large spot. Evidence for nonthermal emission is presented.
Title: Non-thermal and non-equilibrium effects in soft X-ray flare
spectra
Authors: Gabriel, A. H.; Antonucci, E.; Steenman-Clark, L.
Bibcode: 1983SoPh...86...59G
Altcode:
Processes leading to the excitation of soft X-ray line spectra are
discussed in relation to their thermal or non-thermal nature. Through
analysis of calcium spectra from the XRP experiment on SMM, it is
shown that the ionization balance during the gradual phase of flares is
effectively in the steady-state. A search of suitable complex flares
with multiple impulsive features has shown indications of soft X-ray
line intensity anomalies, consistent with the presence of a non-thermal
electron component.
Title: Observation of Chromospheric Evaporation during the Solar
Maximum Mission
Authors: Antonucci, E.; Dennis, B. R.
Bibcode: 1983SoPh...86...67A
Altcode:
A sample of flares detected in 1980 with the Bent Crystal Spectrometer
and the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission
satellite has been analysed to study the upward motions of part of the
soft X-ray emitting plasma. These motions are inferred from the presence
of secondary blue-shifted lines in the Ca XIX and Fe XXV spectral
regions during the impulsive phase of disk flares. Limb flares do not
show such blue-shifted lines indicating that the direction of the plasma
motion is mainly radial and outward. The temporal association of these
upward motions with the rise of the thermal phase and with the impulsive
hard X-ray burst, as well as considerations of the plasma energetics,
favour the interpretation of this phenomenon in terms of chromospheric
evaporation. The two measureable parameters of the evaporating plasma,
emission measure and velocity, depend on parameters related to the
energy deposition and to the thermal phase. The evaporation velocity
is found to be correlated with the spectral index of the hard X-ray
flux and with the rise time of the thermal emission measure of the
coronal plasma. The emission measure of the rising plasma is found to
be correlated with the total energy deposited by the fast electrons
in the chromosphere by collisions during the impulsive phase and with
the maximum emission measure of the coronal plasma.
Title: Dielectronic satellite spectra for highly-charged helium-like
ions. VII - Calcium spectra: Theory and comparison with SMM
observations
Authors: Bely-Dubau, F.; Faucher, P.; Steenman-Clark, L.; Dubau, J.;
Loulergue, M.; Gabriel, A. H.; Antonucci, E.; Volonte, S.; Rapley,
C. G.
Bibcode: 1982MNRAS.201.1155B
Altcode:
The atomic theory, developed in earlier papers in this series for
iron, has been applied to the spectra from calcium. This includes
the production of satellite lines by dielectronic recombination and
inner-shell excitation, as well as the production of helium-like spectra
by excitation, radiative and dielectronic recombination and through
cascades. Two methods are described for fitting observed spectra,
to determine the plasma physical parameters. The results are applied
to the observations from the soft X-ray Polychromator of the flare on
1980 May 21. The good agreement between computed and observed spectra
gives support to the accuracy of the theory presented. Analysis of
the time variations shows that the flare is close to steady-state
ionization balance throughout.
Title: Multiple Wavelength Observations of a Solar Active Region
Authors: Chiuderi-Drago, F.; Bandiera, R.; Willson, R. F.; Slottje,
C.; Falciani, R.; Antonucci, E.; Lang, K. R.; Shibasaki, K.
Bibcode: 1982SoPh...80...71C
Altcode:
The Solar Maximum Mission Satellite, the Sacramento Peak Vacuum
Tower Telescope, the Very Large Array and the Westerbork Synthesis
Radio Telescope have been used to observe active region AR 2490 on
two consecutive days at soft X-ray, ultraviolet, optical and radio
wavelengths (2, 6, and 20 cm), with comparable angular resolution
(2″ to 15″) and field of view (4' × 4'). The radio emissions at
λ = 6 cm and 20 cm show a double structure in which one component is
associated with bright Hα plage, C IV and soft X-ray emission, and
the other component is associated only with sunspots. No radiation at
λ = 2 cm is detected in this latter component. Coronal temperature
and emission measure derived from X-ray lines indicate that the
dominant radiation mechanism of the plage-associated component is
due to thermal bremsstrahlung while the gyroresonance absorption
coefficient must be invoked to account for the high brightness
temperature (Tb≈2×106K) observed in the
sunspot associated component. The high magnetic field strength needed
(600 G at a level where T∼2×106K) is explained assuming
a thin transition zone, in order to reach a high electron temperature
close to the sunspot, where the magnetic fields are stronger. A higher
temperature gradient above sunspots is also consistent with the absence
of detectable C IV emission.
Title: Soft X-Ray Discriminators of Flare Classification
Authors: Antonucci, E.
Bibcode: 1982Obs...102..121A
Altcode:
No abstract at ADS
Title: Impulsive Phase of Flares in Soft X-Ray Emission
Authors: Antonucci, E.; Gabriel, A. H.; Acton, L. W.; Culhane, J. L.;
Doyle, J. G.; Leibacher, J. W.; Machado, M. E.; Orwig, L. E.; Rapley,
C. G.
Bibcode: 1982SoPh...78..107A
Altcode:
Observations using the Bent Crystal Spectrometer instrument on the
Solar Maximum Mission show that turbulence and blue-shifted motions
are characteristic of the soft X-ray plasma during the impulsive phase
of flares, and are coincident with the hard X-ray bursts observed
by the Hard X-ray Burst Spectrometer. A method for analysing the
Ca XIX and Fe XXV spectra characteristic of the impulsive phase
is presented. Non-thermal widths and blue-shifted components in the
spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent
velocities exceeding 100 km s-1 and upward motions of
300-400 km s-1.
Title: Bright point study
Authors: Tang, F.; Harvey, K.; Bruner, M.; Kent, B.; Antonucci, E.
Bibcode: 1982AdSpR...2k..65T
Altcode: 1982AdSpR...2...65T
Transition region and coronal observations of bright points by
instruments aboard the Solar Maximum Mission were accompanied
by high resolution photospheric magnetograph observations on
September 11, 1980. In the photosphere a total of 31 bipolar
ephemeral regions were observed from birth in 9.3 hours of combined
magnetograph observations from three observatories. The Ultraviolet
Spectrometer-Polarimeter observed 2 of the 3 ephemeral regions present
in its field of view in the C IV 1548Å line. The unobserved ephemeral
region was the shortest-lived (2.5 hr) and lowest in magnetic flux
density (13G) of the three. In the O VIII 18.969Å line, the
Flat Crystal Spectrometer detected only low level signals that are
not statistically significant to be positively identified with any
of the 16 ephemeral regions observed in the photosphere. The
SMM data shows that at any given time there lacked a one-to-one
correspondence between observable bright points and photospheric
ephemeral regions. More ephemeral regions were observed than their
counterparts in the transition region and the corona.
Title: Chromospheric evaporation in soft X-ray flares
Authors: Antonucci, E.
Bibcode: 1982MmSAI..53..495A
Altcode:
The chromospheric evaporation process, as observed with Doppler velocity
measurements in the soft X-ray emission by the X-Ray Polychromator
of the Solar Maximum Mission, is discussed. Plasma at a temperature
exceeding 1 times 10 to the 7th K, starts flowing into the coronal
region of a flare at the onset of the impulsive phase. The flow
persists during the period of the main hard X-ray emission and lasts
approximately until the peak of the thermal phase is reached. It is
suggested that the evaporation process represents the main mechanism for
transferring to the coronal region the mass and energy responsible for
the soft X-ray emission during the thermal phase of flares. The values
of density and temperature of the evaporating plasma, sufficient to
account for the increase in the density and temperature of the coronal
thermal plasma during the impulsive phase, are derived.
Title: Observations of transitions of hydrogen-like Fe XXVI in solar
flare spectra
Authors: Parmar, A. N.; Culhane, J. L.; Rapley, C. G.; Antonucci,
E.; Gabriel, A. H.; Loulergue, M.
Bibcode: 1981MNRAS.197P..29P
Altcode:
Observations of solar flare spectra over the wavelength range
1.769-1.796 A with the Bent Crystal Spectrometer on the NASA
Solar Maximum Mission satellite are presented. The 2P3/2, 2P1/2
and associated satellite transitions of Fe XXVI are identified,
their intensities and widths estimated and the results compared with
theoretical predictions. For two spectra, which include the isolated n
= 2 satellite features, the observations can be reproduced by plasma
temperatures of 24,000,000 and 28,400,000 K. Linewidth measurements
show evidence for nonthermal velocities of up to 150 km/s. Emission
measures derived from the Fe XXVI observations are compared with those
from lower temperature Ca XIX and Fe XXV measurements and an emission
measure decreasing with temperature is found.
Title: X-ray line widths and coronal heating
Authors: Acton, L. W.; Wolfson, C. J.; Joki, E. G.; Culhane, J. L.;
Rapley, C. G.; Bentley, R. D.; Gabriel, A. H.; Phillips, K. J. H.;
Hayes, R. W.; Antonucci, E.
Bibcode: 1981ApJ...244L.137A
Altcode:
Preliminary results of spectroscopy and imaging of a solar active region
and flare plasma in soft X-ray emission lines are presented. Observed
X-ray line widths in a nonflaring active region are broader than the
Doppler width corresponding to the local electron temperature. An
analysis of 41 soft X-ray flares within a single active region reveals
a preference for flares to occur at locations that already show
enhanced X-ray emission and to favor magnetic complexity over high
gradient. However, flares do not appear to be directly responsible
for the heating and X-ray production of the active regions.
Title: Observations of the limb solar flare on 1980 April 30 with
the SMM X-ray polychromator
Authors: Gabriel, A. H.; Phillips, K. J. H.; Acton, L. W.; Wolfson,
C. J.; Culhane, J. L.; Rapley, C. G.; Bentley, R. D.; Kayat, M. A.;
Jordan, C.; Antonucci, E.
Bibcode: 1981ApJ...244L.147G
Altcode:
No abstract at ADS
Title: X-ray spectra of solar flares obtained with a high-resolution
bent crystal spectrometer
Authors: Culhane, J. L.; Rapley, C. G.; Bentley, R. D.; Gabriel,
A. H.; Phillips, K. J.; Acton, L. W.; Wolfson, C. J.; Catura, R. C.;
Jordan, C.; Antonucci, E.
Bibcode: 1981ApJ...244L.141C
Altcode:
Preliminary results obtained for three solar flares with the bent
crystal spectrometer on the SMM are presented. Resonance and satellite
lines of Ca XIX and XVIII and Fe XXV and XXIV are observed together
with the Fe XXVI Lyman-alpha line. Plasma properties are deduced from
line ratios and evidence is presented for changes of line widths
coincident with the occurrence of a hard X-ray impulsive burst. Fe
K-alpha spectra from a disk center and a limb flare agree with the
predictions of a fluorescence excitation model. However, a transient
Fe K-alpha burst observed in a third flare may be explained by the
collisional ionization of cool iron by energetic electrons.
Title: Solar maximum mission experiment: Early results from the soft
X-ray polychromator experiment
Authors: Gabriel, A. H.; Antonucci, E.; Phillips, K. J. H.; Culhane,
J. L.; Bentley, R. D.; Parmar, A. N.; Rapley, C. G.; Acton, L. W.;
Leibacher, J. W.; Wolfson, C. J.; Strong, K. T.; Jordan, C.
Bibcode: 1981AdSpR...1m.267G
Altcode: 1981AdSpR...1Q.267G
The X-Ray Polychromator experiment has been in operation on the
SMM satellite for over three months. It is observing flares and
active regions in the wavelength range 1Å to 23Å using a number
of different modes. These include polychromatic imaging, high
resolution line profiles, high dispersion spectra, and light curves
with high time-resolution. Data are described together with some of
the preliminary analysis and interpretation.
Title: Solar Maximum Mission experiment: early results from the soft
X-ray polychromator experiment.
Authors: Gabriel, A. H.; Culhane, J. L.; Acton, L. W.; Antonucci,
E.; Bentley, R. D.; Jordan, C.; Leibacher, J. W.; Parmar, A. N.;
Phillips, K. J. H.; Rapley, C. G.; Wolfson, C. J.; Strong, K. T.
Bibcode: 1981hea..conf..267G
Altcode:
No abstract at ADS
Title: Soft X-ray Emission During the Impulsive Phase of a Flare
Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G.
Bibcode: 1980BAAS...12..900A
Altcode:
No abstract at ADS
Title: The Spatial Dependence of UV and X-Ray Phenomena Occurring
During the Impulsive Phase of a Flare
Authors: Frost, K. J.; Dennis, B. R.; Orwig, L. E.; Kiplinger, A. L.;
Leibacher, J.; Antonucci, E.; Parmar, A. N.; Woodgate, B.; Shine,
R.; Cheng, C. -C.
Bibcode: 1980BAAS...12..905F
Altcode:
No abstract at ADS
Title: Interpretation of the Ca XIX, Fe XXV and Fe XXVI BCS Spectra
Authors: Gabriel, A. H.; Antonucci, E.; Dubau, J.
Bibcode: 1980BAAS...12..912G
Altcode:
No abstract at ADS
Title: Preliminary Results from Calcium and Iron Solar Flare Spectra
from a Bent Crystal Spectrometer
Authors: Antonucci, Ester
Bibcode: 1980BAAS...12..533A
Altcode:
No abstract at ADS
Title: Comment on 'The annual and semiannual variations of the cosmic
radiation' by H. P. Khor, K. W. Kwok, and A. J. Owens
Authors: Antonucci, E.; Marocchi, D.; Perona, G. E.
Bibcode: 1980JGR....85..797A
Altcode:
The phase changes of the annual and seniannual variations of the cosmic
ray intensity through two colar cycles and its relationship to the
22-year solar magnetic cycle have been observed and reported by us. The
phase of the yearly cosmic ray modulation reverses at the reversals
of the polarity of the solar polar magnetic fields. The significance
of this effect cannot be dismissed on the basis of an analysis on
an insufficient data set, in fact, during the period 1960-1975 used
by Khor et al. [1979], the solar magnetic configuration is steadily
the same except that for the 4 years 1972-1975, which, however, do
correspond to a variable interplanetary magnetic dipolar configuration.
Title: Chromospheric rotation. II. Dependence on the size of
chromospheric features.
Authors: Antonucci, E.; Azzarelli, L.; Casalini, P.; Cerri, S.;
Denoth, F.
Bibcode: 1979SoPh...63...17A
Altcode:
The dependence of solar rotation on the size of the chromospheric
tracers is considered. On the basis of an analysis of Ca II
K3 daily filtergrams taken in the period 8 May-14 August,
1972, chromospheric features can be divided into two classes according
to their size. Features with size falling into the range 24 000-110
000 km can be identified with network elements, while those falling
into the range 120 000-300 000 km with active regions, or brightness
features of comparable size present at high latitudes. The rotation
rate is determined separately for the two families of chromospheric
features by means of a cross-correlation technique which directly yields
the average daily displacement of tracers due to rotation. Before
computing the cross-correlation functions, chromospheric brightness
data have been filtered with appropriate bandpass and highpass filters
for separating spatial periodicities whose wavelengths fall into the
two ranges of size, characteristic of the network pattern and of the
activity centers. A difference less than 1% of the rotation rate of
the two families of chromospheric features has been found. This is
an indication for a substantial corotation at chromospheric levels
of different short-lived features, both related to solar activity and
controlled by the convective supergranular motions.
Title: Rotation and lifetime of coronal features.
Authors: Antonucci, E.; Dodero, M. A.
Bibcode: 1979SoPh...62..107A
Altcode:
A study on the differences of rotation properties, based on the lifetime
of coronal features, has been performed for the period 1972-1974. The
short-lived component of the green corona associated with solar activity
is differentially rotating, while long-lived coronal features persisting
more than one synodic rotation period, show little or no differential
rotation. These two components coexist at a same latitude within a
wide latitude range at least in one of the solar hemispheres.
Title: Chromospheric rotation. I: Dependence on the lifetime of
chromospheric features.
Authors: Antonucci, E.; Azzarelli, L.; Casalini, P.; Cerri, S.;
Denoth, F.
Bibcode: 1979SoPh...61....9A
Altcode:
In this paper the dependence of the rotation rate of chromospheric
features on their lifetime is discussed. The angular velocity of short
lived emission features at chromospheric level has been determined by
analyzing daily filtergrams in the Ca II K3 line, obtained
at the Anacapri Observatory, in the period 8 May-14 August 1972. An
accurate method of analysis has been developed in order to evaluate the
average daily displacement of chromospheric tracers, by computing an
`average crosscorrelation' of chromospheric brightness features for
consecutive days at constant latitude. This method yields the average
rotation rate for short-lived K3 chromospheric features
(lifetime ⩾ 1 day). These results are compared with the determinations
of the rotation rate of long-lived chromospheric features (lifetime ⩾
27 days) obtained by using the same kind of data. Long-lived tracers
are rotating rigidly in years of declining activity, while short-lived
ones rotate differentially. Short-lived chromospheric features rotate
at the same rate as the chromospheric plasma, i.e. faster than the
photospheric plasma.
Title: Mappe coronali nei periodi di sole quieto.
Authors: Antonucci, E.; Dodero, M. A.; Marocchi, D.
Bibcode: 1979RSAI...22..163A
Altcode:
No abstract at ADS
Title: Dependence of cosmic-ray transport on the orientation of the
solar magnetic dipole.
Authors: Antonucci, E.; Marocchi, D.; Perona, G. E.
Bibcode: 1978NCimC...1..395A
Altcode:
The dependence of cosmic-ray transport in the interplanetary space on
the polarity configuration of the solar and interplanetary magnetic
fields is discussed. The diffusion mechanism is not only related to
the irregularities present in the interplanetary magnetic field, but
also to its regular structure, because of the curvature and gradient
drifts of the particles. Hence diffusion is affected by the polarity
reversals of the interplanetary magnetic dipole which are related to
the reversals of the solar dipole. As a consequence a phase reversal of
both the annual and semi-annual variations in the cosmic-ray intensity
occurs. This effect has been studied throughout the period 1954-1976, by
analyzing the Climax neutron monitor data. In addition, the latitudinal
distribution of the average solar activity itself in this period changes
simultaneously to the polarity reversals of the solar polar fields.
Title: Phase reversals in the polar magnetic fields of the sun and
in the annual and semiannual variations in cosmic ray intensity.
Authors: Antonucci, E.; Marocchi, D.; Perona, G. E.
Bibcode: 1978ApJ...220..712A
Altcode:
Annual and semiannual variations in galactic-cosmic-ray intensity have
been computed for the period 1954-1973. These variations show a fairly
constant phase over several years. However, an abrupt reversal of
the direction of both vectors, representing the annual and semiannual
variations, is associated with reversal of the polarities of the solar
polar magnetic fields, which occurs near sunspot maximum. Furthermore,
it is well known that the annual and semiannual variations may be
related to the first- and second-order derivatives, with respect to
solar latitude, of the cosmic-ray density. Consequently, the cosmic-ray
gradient perpendicular to the solar equatorial plane regularly changes
its direction at the solar-activity maximum, displaying a 22-year
periodicity.
Title: Rotation of the Solar Chromosphere
Authors: Antonucci, E.
Bibcode: 1978pfsl.conf...73A
Altcode: 1978ESPM....2...73A
No abstract at ADS
Title: Raggi cosmici durante i brillamenti solari.
Authors: Antonucci, E.
Bibcode: 1978MmSAI..48..257A
Altcode:
No abstract at ADS
Title: Chromospheric rotation during 1972 73, years of declining
activity
Authors: Antonucci, E.; Azzarelli, L.; Casalini, P.; Cerri, S.
Bibcode: 1977SoPh...53..519A
Altcode:
The rotational behaviour of the chromosphere, observed in the Ca II
K3 line, is studied during 1972-1973, years of decreasing
solar activity. Daily chromospheric filtergrams, detected at the
Anacapri Observatory, are digitized by means of a flying-spot
photometer, controlled by computer. The time series of the daily
chromospheric data detected at central meridian, relative to 30
consecutive latitude zones, are analyzed to determine the recurrence
tendency due to the rotation of long-lived chromospheric features. The
computed rotation rate is independent of latitude, in agreement with
the results obtained for the green corona during the years before
sunspot minimum. Namely both chromospheric and coronal features,
with lifetime exceeding one solar rotation, are almost not affected
by differential rotation before sunspot minimum.
Title: Coronal rotation dependence on the solar cycle phase.
Authors: Antonucci, E.; Dodero, M. A.
Bibcode: 1977SoPh...53..179A
Altcode:
A study of the green corona rotation rate, during the period 1970-1974,
confirms that the differential rotation degree varies systematically
through a solar cycle and that the corona rotates in an almost rigid
manner before sunspot minimum. During the first two years, 1970-1971,
the differential rotation degree, characteristic of high solar activity
periods is detected. While during the years of declining activity,
1972-1974, a drastic decrease of the differential rotation degree
occurs and the green corona rotates almost rigidly, as the coronal
holes observed in the same period. These conclusions are valid only
for the rotation of coronal features with lifetime of at least one
solar rotation.
Title: Cosmic rays during solar flares
Authors: Antonucci, E.
Bibcode: 1977MmSAI..48..257A
Altcode:
A brief review is presented of recent literature on the solar cosmic ray
phenomenon. Consideration is given to pulsed solar-particle events, and
a classification of solar flares is presented in terms of corpuscular
emission. The composition of solar particles is examined and attention
is given to the nuclear-reaction mechanism for the production of solar
cosmic rays.
Title: Cosmic ray perpendicular gradient during 1962-1972
Authors: Antonucci, Ester; Marocchi, Daniela
Bibcode: 1976JGR....81.4626A
Altcode:
No abstract at ADS
Title: Cosmic ray perpendicular gradient during 1962-1972
Authors: Antonucci, Ester; Marocchi, Daniela
Bibcode: 1976JGR....81.4627A
Altcode:
An analysis of the perpendicular gradient of galactic cosmic rays
performed on the basis of the estimate of the annual and semiannual
variations of the cosmic ray intensity is reported. The daily cosmic
ray intensity data detected by the Deep River neutron monitors have
been used for the period 1962-1972. The perpendicular gradient can be
separated into two components which are asymmetrical and symmetrical,
respectively, with respect to the solar equatorial plane. The
asymmetrical gradient component is quasi-stationary over the whole
period, while the symmetrical one reverses its direction once. Then
in northern and southern regions of the solar modulating cavity the
perpendicular gradient displays different characteristics in both
value and direction which depend on the solar cycle phase.
Title: A theoretical analysis of the semiannual component in the
heliocentric dependence of high-energy galactic cosmic rays.
Authors: Perona, G. E.; Antonucci, E.
Bibcode: 1976ApJ...207..989P
Altcode:
Annual and semiannual variations of the galactic cosmic rays and
estimates of their radial derivatives have been used to determine the
most significant terms at 1 AU in the convection-diffusion equation. It
turns out that both the changes in sign and the absolute value of
the semiannual variation may be explained through the interplay of
convection, diffusion across magnetic field lines, and drift. Indeed,
such sign changes seem to be associated with reversals of the sign in
the predominant polarity of the interplanetary magnetic field.
Title: Rigidly rotating component of the solar corona.
Authors: Antonucci, E.
Bibcode: 1975NCimB..25..513A
Altcode:
Autocorrelation analyses of green-line intensity data for the period
1947-70 at latitudes up to plus or minus 60 deg have been performed to
determine the recurrence period of the time series, interpreted as the
synodic rotation period of the corona at a given latitude. Long-lived
coronal structures have been shown to exist, with the following
characteristics: (1) rigid rotation up to plus or minus 60 deg latitude,
and (2) correlation with the large-scale solar magnetic pattern. These
features develop essentially as longitudinally persistent phenomena,
close to the boundaries of the solar magnetic sectors.
Title: Heliographic-latitude dependence of the cosmic-ray intensity
Authors: Antonucci, E.; Marocchi, D.
Bibcode: 1974GeoRL...1..302A
Altcode:
Evidence for a semi-annual variation in the galactic cosmic-ray
intensity is presented. This effect can be associated with the
heliographic latitude excursion of the earth during its orbital
motion. Therefore the phase evaluation of the semi-annual variation can
be used to infer the direction of the cosmic-ray gradient perpendicular
to the solar equatorial plane through the solar cycle.
Title: Solar cycle variation of large-scale coronal structures
Authors: Antonucci, E.; Duvall, T. L.
Bibcode: 1974SoPh...38..439A
Altcode:
A green line intensity variation is associated with the interplanetary
and photospheric magnetic sector structure. This effect depends on the
solar cycle and occurs with the same amplitude in the latitude range
60° N-60° S. Extended longitudinal coronal structures are suggested,
which indicate the existence of closed magnetic field lines over the
neutral line, separating adjacent regions of opposite polarities on
the photospheric surface.
Title: Green Corona and Solar Sector Structure
Authors: Antonucci, Ester; Svalgaard, Leif
Bibcode: 1974SoPh...36..115A
Altcode:
Analysis of the green line corona for the interval 1947-1970 suggests
the existence of largescale organization of the emission. The green
line emission at high northern latitudes (≈ 40°-60°) is correlated
with the emission at high southern latitudes 6, 15 and 24 days later,
while the low latitude green corona seems to be correlated on both
sides of the equator with no time lag. These coronal features are
recurrent with a 27-day period at all latitudes between ± 60 °,
and we associate these large-scale structures with the solar magnetic
sector structure. The high correlation between northern and southern
high-latitude emission at 15 days time lag is explained as a signature
of a two-sector structure, while four sectors are associated with the
6 and 24 day peaks.
Title: Rigid and Differential Rotation of the Solar Corona
Authors: Antonucci, Ester; Svalgaard, Leif
Bibcode: 1974BAAS....6S.284A
Altcode:
No abstract at ADS
Title: Eleven-Years Inversion of the Green Corona Emission
Authors: Antonucci, Ester
Bibcode: 1974SoPh...34..471A
Altcode:
A cross-correlation analysis of coronal green line intensity (5303 Å)
and interplanetary magnetic field polarity for the period 1947-1970
shows that the coronal features are organized in a constant pattern
with respect to the 4-sector structure through the solar cycle. A
sudden inversion of the coronal pattern with respect to the sector
structure takes place at the solar minima. The high emission regions of
the green corona are located near the solar magnetic sector boundaries
having polarities (−, +), (+, −), (−, +) during cycles 18, 19,
20 respectively in the northern hemisphere, and (+, −), (−, +),
(+, −) in the southern hemisphere.
Title: Rigid and Differential Rotation of the Solar Corona
Authors: Antonucci, Ester; Svalgaard, Leif
Bibcode: 1974SoPh...34....3A
Altcode:
The rotation of the solar corona has been studied using recurrence
properties of the green coronal line (5303 Å) for the interval
1947-1970. Short-lived coronal activity is found to show the same
differential rotation as short-lived photospheric magnetic field
features. Long-lived recurrences show rigid rotation in the latitude
interval ±57°.5. It is proposed that at least part of the variability
of rotational properties of the solar atmosphere may be understood as
a consequence of coexistence of differential and rigid solar rotation.
Title: Diurnal anisotropies of the cosmic ray intensity underground
during maximum solar activity
Authors: Antonucci, E.; Castagnoli, G. Cini; Dodero, M. A.; Giraud, C.
Bibcode: 1973JGR....78.7174A
Altcode:
The diurnal variations of underground cosmic ray intensities are
analyzed on a day-to-day basis. At the depths of the London and Torino
stations an anisotropy in the direction of the interplanetary magnetic
field is observed in addition to the corotation effect, which varies
in relation to the perturbations produced by the sun. This effect is
not recorded in the Hobart data during the same period of observation.
Title: The Diurnal Anisotropies of the Cosmic Ray Intensity
Underground
Authors: Antonucci, E.; Cini Castagnoli, G.; Dodero, M. A.; Giraud, C.
Bibcode: 1973ICRC....2..982A
Altcode: 1973ICRC...13..982A
No abstract at ADS
Title: Effects of Active Solar Regions on the Galactic Cosmic Ray
Intensity
Authors: Antonucci, E.; Castagnoli, G. Cini; Dodero, M. A.
Bibcode: 1971SoPh...20..497A
Altcode:
During the year 1969 two long-lived centres were active on the Sun
at Carrington longitudes 50° < L < 100° and 250° < L <
300°. About 80% of the flares of importance ⩾ 1B, produced during
this period, originated in these zones.
Title: Solar Effects on the Cosmic Ray Intensity Observed at 70
M. W. E. Underground
Authors: Antonucci, E.; Castagnoli, G. Cini; Dodero, M. A.
Bibcode: 1971SoPh...17..491A
Altcode:
We have correlated intensity decreases in the galactic component of
cosmic rays observed at the Earth with solar phenomena. We have found
that there exist intensity decreases detected underground, which are
probably associated with long-lived interplanetary streams and which
are not directly associated with single flares. We expect to detect the
streams with underground monitors before the arrival of the streams
at the Earth. The early detection will be in the northern or in the
southern hemisphere, depending on the sign of the interplanetary field.
Title: Underground Cosmic Ray Intensity Modulation and Interplanetary
Structures During 1969-1970.
Authors: Antonucci, E.; Cini Castagnoli, G.; Dodero, M. A.
Bibcode: 1971ICRC....2..629A
Altcode: 1971ICRC...12..629A
No abstract at ADS
Title: Effects of Long Lived Solar Centres on the Galactic Cosmic
Ray Intensity.
Authors: Antonucci, E.; Cini Castagnoli, G.; Dodero, M. A.
Bibcode: 1971ICRC....2..623A
Altcode: 1971ICRC...12..623A
No abstract at ADS
Title: On the diurnal variations of the cosmic ray intensity observed
70 m. w. e. underground
Authors: Antonucci, E.; Cini Castagnoli, G.; Dodero, M. A.
Bibcode: 1970ICRC....2..157A
Altcode: 1970ICRC...11b.157A
No abstract at ADS