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Author name code: panasenco
ADS astronomy entries on 2022-09-14
author:"Panasenco, Olga"
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Title: Linking Small-scale Solar Wind Properties with Large-scale
Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar
Orbiter Observations
Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca;
D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto;
Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru;
Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen,
Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone,
Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale,
Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit,
Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.;
Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David
M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli,
Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel,
Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo;
Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco,
Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto,
Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati,
Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.;
Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli,
Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio;
Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo;
Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli,
Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère,
Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella,
Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco;
Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki,
Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial,
Jean-Claude; Woch, Joachim; Zimbardo, Gaetano
2022ApJ...935..112T Altcode:
The solar wind measured in situ by Parker Solar Probe in the very
inner heliosphere is studied in combination with the remote-sensing
observation of the coronal source region provided by the METIS
coronagraph aboard Solar Orbiter. The coronal outflows observed near
the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and
6.3 R <SUB>⊙</SUB> above the eastern solar limb, can be associated
with the streams sampled by PSP at 0.11 and 0.26 au from the Sun,
in two time intervals almost 5 days apart. The two plasma flows
come from two distinct source regions, characterized by different
magnetic field polarity and intensity at the coronal base. It follows
that both the global and local properties of the two streams are
different. Specifically, the solar wind emanating from the stronger
magnetic field region has a lower bulk flux density, as expected,
and is in a state of well-developed Alfvénic turbulence, with low
intermittency. This is interpreted in terms of slab turbulence in the
context of nearly incompressible magnetohydrodynamics. Conversely,
the highly intermittent and poorly developed turbulent behavior of the
solar wind from the weaker magnetic field region is presumably due to
large magnetic deflections most likely attributed to the presence of
switchbacks of interchange reconnection origin.
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Title: Patches of Magnetic Switchbacks and Their Origins
Authors: Shi, Chen; Panasenco, Olga; Velli, Marco; Tenerani, Anna;
Verniero, Jaye L.; Sioulas, Nikos; Huang, Zesen; Brosius, A.; Bale,
Stuart D.; Klein, Kristopher; Kasper, Justin; de Wit, Thierry Dudok;
Goetz, Keith; Harvey, Peter R.; MacDowall, Robert J.; Malaspina,
David M.; Pulupa, Marc; Larson, Davin; Livi, Roberto; Case, Anthony;
Stevens, Michael
2022ApJ...934..152S Altcode: 2022arXiv220603807S
Parker Solar Probe (PSP) has shown that the solar wind in the inner
heliosphere is characterized by the quasi omnipresence of magnetic
switchbacks ("switchback" hereinafter), local backward bends of
magnetic field lines. Switchbacks also tend to come in patches, with
a large-scale modulation that appears to have a spatial scale size
comparable to supergranulation on the Sun. Here we inspect data from
the first 10 encounters of PSP focusing on different time intervals
when clear switchback patches were observed by PSP. We show that the
switchbacks modulation, on a timescale of several hours, seems to be
independent of whether PSP is near perihelion, when it rapidly traverses
large swaths of longitude remaining at the same heliocentric distance,
or near the radial-scan part of its orbit, when PSP hovers over the
same longitude on the Sun while rapidly moving radially inwards or
outwards. This implies that switchback patches must also have an
intrinsically temporal modulation most probably originating at the
Sun. Between two consecutive patches, the magnetic field is usually
very quiescent with weak fluctuations. We compare various parameters
between the quiescent intervals and the switchback intervals. The
results show that the quiescent intervals are typically less Alfvénic
than switchback intervals, and the magnetic power spectrum is usually
shallower in quiescent intervals. We propose that the temporal
modulation of switchback patches may be related to the "breathing"
of emerging flux that appears in images as the formation of "bubbles"
below prominences in the Hinode/SOT observations.
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Title: Interchange reconnection within coronal holes powers the fast
solar wind
Authors: Bale, S. D.; Drake, J. F.; McManus, M. D.; Desai, M. I.;
Badman, S. T.; Larson, D. E.; Swisdak, M.; Raouafi, N. E.; Phan, T.;
Velli, M.; McComas, D. J.; Cohen, C. M. S.; Mitchell, D.; Panasenco,
O.; Kasper, J. C.
2022arXiv220807932B Altcode:
The fast solar wind that fills the heliosphere originates from deep
within regions of open magnetic field on the Sun called coronal
holes. However the energy source responsible for accelerating the
outflowing plasma to such high speeds is still widely debated, although
there is broad evidence that it is ultimately magnetic in nature with
candidate mechanisms including Alfven wave heating and interchange
reconnection. The magnetic field near the solar surface within coronal
holes is structured on spatial scales associated with the boundaries of
meso-scale supergranulation convection cells, where descending flows
create intense bundles of magnetic field. The energy density in these
network magnetic field bundles is a likely candidate as an energy source
of the wind. Here we report measurements of two fast solar wind streams
from the Parker Solar Probe (PSP) spacecraft near its 10th perihelion
which provides strong evidence for the interchange reconnection
mechanism. Specifically, we show that supergranulation structure at
the coronal hole base remains imprinted in the near-Sun solar wind
resulting in asymmetric patches of magnetic 'switchbacks' and bursty
solar wind streams with corresponding energetic ions with power law-like
distributions extending to beyond 100 keV. Particle-in-cell simulations
of interchange reconnection between open and closed magnetic structures
support key features of the observations, including the energetic
ion spectra. Important characteristics of interchange reconnection
in the low corona are inferred from the PSP data including that the
reconnection is collisionless and that the rate of energy release is
sufficient to heat the ambient plasma and drive the fast wind.
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Title: Understanding the Solar Wind: Parker Solar Probe in the
Inner Heliosphere
Authors: Velli, Marco; Bale, Stuart; Panasenco, Olga; Tenerani, Anna;
Shi, Chen; Verniero, Jaye
2022cosp...44.1317V Altcode:
The magnetic field is fundamental to solar activity and shapes
the interplanetary environment, as clearly shown by the full three
dimensional monitoring of the heliosphere provided by the measurements
of the Helios, Ulysses, SOHO, ACE, Wind, STEREO, Hinode, IRIS, SDO,
and Voyager spacecraft. Magnetic fields are also the source for coronal
heating and the very existence of the solar wind; produced by the
sun's dynamo and emerging into the corona, magnetic fields become a
conduit for waves, act to store energy, and then propel plasma into
the heliosphere in the form of Coronal Mass Ejections (CMEs). Parker
Solar Probe was launched to carry out the first in situ exploration of
the outer solar corona and inner heliosphere. Direct measurements of
the plasma in the closest atmosphere of our star have already produced
significant surprises including switchbacks, the predominance of Alfvén
wave turbulence, magnetic reconnection in the forming heliospheric
current sheets. Here I will review both models and observations,
including progress and pitfalls in the interpretation of PSP results.
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Title: Investigating the solar sources and evolution of the Alfvénic
slow wind with a coordinated Parker Solar Probe - Solar Orbiter study
Authors: D'Amicis, Raffaella; Panasenco, Olga; Velli, Marco; Telloni,
Daniele; Perrone, Denise; Bruno, Roberto; de Marco, Rossana
2022cosp...44.1335D Altcode:
The launch of Parker Solar Probe (PSP) and Solar Orbiter (SO) started
a new era in the exploration of the inner heliosphere. Since both
missions will follow the ascending phase of the solar cycle, joint
studies will offer unprecedented opportunities to study the Alfvénic
slow wind in situ and to identify its solar source. This is extremely
important for improving the understanding of this solar wind regime,
with particular reference to its origin and evolution, and of the
general problem of solar wind acceleration. In this study, we focus on
a particular orbital configuration, occurring at the end of April 2021,
in which PSP was magnetically and then radially aligned with SO. A
Potential Field Source-Surface (PFSS) model was used to link in-situ
measurements with the corresponding solar wind source regions, mapping
PSP and SO measurements back to a pseudostreamer configuration in the
solar corona, which is of primary importance to set the conditions
for the development of the Alfvénic slow solar wind. One week after,
Earth was connected to the same pseudostreamer. This event represents
a good opportunity to study the evolution of the plasma coming from the
same source region with particular reference to its turbulent behaviour
and the Alfvénic content of the fluctuations from 0.074 AU to 1 AU.
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Title: Photospheric and low coronal sources of different types
of solar wind and transients observed by Parker Solar Probe and
Solar Orbiter
Authors: Panasenco, Olga; Bale, Stuart; Velli, Marco; Tenerani, Anna;
Shi, Chen; D'Amicis, Raffaella; Verniero, Jaye; Sioulas, Nikos
2022cosp...44.1532P Altcode:
Initial Parker Solar Probe results have shown that slow Alfvénic
solar wind intervals appear to be a frequent, if not standard,
component of the nascent solar wind inside 0.5 AU. In addition to
the strong presence of Alfvénic fluctuations propagating away from
the Sun, such intervals also display the huge oscillations known as
switchbacks, where the Alfvénic fluctuation is accompanied by a fold
in the radial magnetic field and a corresponding forward propagating
radial jet. Switchbacks often come in patches, separated by short
intervals depleted with fluctuations, and periods without switchbacks
may also show a striking quiescence, with the magnetic field remaining
mostly radial and very small amplitude velocity and magnetic field
fluctuations. These observations pose a series of questions on the
origins of the solar wind and the role of coronal structure, as well
as of the evolution of fluctuations within the solar wind. Here
we discuss how the sources of the solar wind measured in situ are
related to photospheric magnetic network and large-scale solar coronal
magnetic structures. In this presentation we use a wealth of remote
sensing and in-situ measurements to pinpoint the sources of the solar
wind observed by PSP and Solar Orbiter. We then discuss the origin and
evolution of so called slow Alfvénic wind, the origins of switchbacks
and sub-Alfvénic wind patches observed in situ at 13.3 Rs and further
during PSP Encounters 1 - 11.
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Title: Statistical study of MHD turbulence straddling the Alfven
surface.
Authors: Sioulas, Nikos; Bale, Stuart; Stevens, Michael; Kasper,
Justin; Panasenco, Olga; Velli, Marco; Reville, Victor; Tenerani,
Anna; Shi, Chen; Whittlesey, Phyllis; Livi, Roberto; Verniero, Jaye;
Bowen, Trevor; Huang, Zesen
2022cosp...44.1474S Altcode:
Driven by the internal dynamics of the Sun, the solar wind expands
into the interplanetary medium to fill the increasing volume of the
heliosphere. A point of fundamental physical significance during the
expansion is the locus at which the radial solar wind speed $V_{SW}$
equals the Alfven speed $V_{A}$, distinguishing the magnetically
dominated sub-Alfvenic, coronal flow $M_{A} \equiv V_{sw}/V_{A} \ll 1$
from the super-Alfvenic solar wind plasma by dynamical means, namely
the "Alfven region". During its latest perihelia, the Parker Solar
Probe mission has encountered several extended sub-Alfvenic regions
providing us with unprecedented in-situ measurements in the vicinity
of the Alfven-zone. These observations will ultimately enable us to
explore the consequences of the Alfven-zone in processes such as the
heating of the solar corona, as well as the generation and subsequent
acceleration of the solar wind. In this work, a statistical study
comparing the properties of turbulence straddling the Alfven surface
during encounters $ E_{8}$, $ E_{9}$ $&$ $ E_{10}$ of Parker
Solar Probe is presented. The degree of intermittency of the magnetic
and velocity field, as well as the Alfvenicity of the fluctuations,
magnetic compressibility, wavevector anisotropy, are examined.
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Title: Frustrated relaxation and instabilities in coronal heating
and solar wind formation
Authors: Velli, Marco; Panasenco, Olga
2022cosp...44.1502V Altcode:
Coronal heating modeling includes the spontaneous formation of
quasi-singular current sheets from the smooth photospheric driving. In
this presentation we discuss the difference between the corona as
describable by "smooth" force-free extrapolations and a corona that is
in a state not of passive relaxation but of what we call a state of
"frustrated relaxation": a state where relaxation is incomplete and
condemned to continuous local dynamics - and coronal heating - due to
photospheric forcing. Such a state is continuously forced and slowly
marching to the catastrophic instability or loss of equilibrium of
CMEs. Our presentation explores frustrated relaxation in the corona via
modeling, numerical simulations and observations. We will in particular
describe the process of current sheet formation as one due to a state
of magnetically dominated turbulence. But we will also describe the
loss of coronal confinement caused by Rayleigh-Taylor and ballooning
-like instability in the heated plasma around complex magnetic field
topologies, a solar wind source that has been almost neglected in the
past. We will specifically demonstate that current sheet formation
is a nonlinear process that is not simply describable in terms of
discontinuities, and also provide a path for turbulence modeling of
the corona and accelerating solar wind.
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Title: Sources of the Solar Wind and its Embedded Fluctuations as
Observed by Parker Solar Probe
Authors: Velli, Marco; Bale, Stuart; Panasenco, Olga; Reville,
Victor; Tenerani, Anna; Shi, Chen; D'Amicis, Raffaella; Sioulas,
Nikos; Huang, Zesen
2022cosp...44.1413V Altcode:
We discuss the sources of the solar wind observed by Parker Solar
Probe over its first 10 encounters (perihelia) with the Sun, and
relate their global properties to those of the embedded turbulence,
including characteristics such as overall magnitude, Alfvénicity,
relative magnitude of density fluctuations, prevalence of switchback
structures. We then describe what we have learned thanks to Parker
of the relationship of the turbulence properties to the solar wind
origins, before arguing how structures such as magnetic funnels,
isolated coronal holes, coronal hole boundaries, pseudostreamers,
helmet streamers and the nascent heliospheric current sheet contribute
to the structure of the inner heliosphere.
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Title: Kinetic effects on the evolution of Alfvenic fluctuations
and switchbacks
Authors: Tenerani, Anna; Panasenco, Olga; Velli, Marco; Shi, Chen;
Sioulas, Nikos; Gonzalez, Carlos; Matteini, Lorenzo
2022cosp...44.1422T Altcode:
Alfvénic fluctuations represent the dominant contribution to turbulent
fluctuations in the solar wind, especially, but not limited to, the
fastest streams with velocity of the order of 600-700 km/s. Observations
from the inner heliosphere to the closest regions to the sun explored
by Parker Solar Probe show that such fluctuations are characterized
by a nearly constant magnetic field amplitude, a condition which
remains largely to be understood and that may be an indication of how
fluctuations evolve and relax in the expanding solar wind. Switchbacks,
an extreme case of Alfvenic fluctuation, display similar properties,
although Parker Solar Probe measurements have revealed a non-negligible
level of compressibility in some cases. Here we will address how
coupling of broadband Alfvenic fluctuations to compressible modes is
mediated by dispersive and kinetic effects. Emphasis will be given
to the role of dispersive and kinetic effects on the stability and
long-term evolution of switchbacks, with a focus on wave-particle
interactions at steepened wave fronts.
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Title: Patches of magnetic switchbacks: hints of their origins
Authors: Shi, Chen; Bale, Stuart; Stevens, Michael; Kasper, Justin;
Panasenco, Olga; Velli, Marco; Whittlesey, Phyllis; Tenerani, Anna;
Livi, Roberto; Verniero, Jaye; Sioulas, Nikos; Huang, Zesen
2022cosp...44.1475S Altcode:
One of the most important findings made by Parker Solar Probe
(PSP) is the omni-presence of the magnetic switchbacks, which are
the local backward-bends of the magnetic field lines, in the young
solar wind. Although many studies were conducted on the properties
and dynamics of these switchbacks, how and where they are generated
are still not fully understood yet. In this study, we analyze
the data from the first seven encounters of PSP with a focus on
the properties of the switchback "patches", i.e., the large-scale
modulation of the switchbacks. We select the time intervals when clear
switchback patches were observed by PSP. We show that the appearance
of switchbacks is frequently modulated on a timescale of several hours
and this timescale seems to be independent on whether PSP is near the
perihelion or near the radial-scan part of its orbit, implying that the
patch of switchbacks likely corresponds to some transient phenomenon
in the solar corona. We find that between two consecutive patches,
the plasma and magnetic field are usually very quiescent with weak
fluctuations. We compare various parameters between the quiescent
intervals and the switchback intervals. The results show: (1) The
quiescent intervals are typically less Alfvenic than the switchback
intervals. (2) The magnetic power spectra are in general steeper in
the switchback intervals than the quiescent intervals.
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Title: Constraining Global Coronal Models with Multiple Independent
Observables
Authors: Badman, Samuel T.; Brooks, David H.; Poirier, Nicolas;
Warren, Harry P.; Petrie, Gordon; Rouillard, Alexis P.; Nick Arge,
C.; Bale, Stuart D.; de Pablos Agüero, Diego; Harra, Louise; Jones,
Shaela I.; Kouloumvakos, Athanasios; Riley, Pete; Panasenco, Olga;
Velli, Marco; Wallace, Samantha
2022ApJ...932..135B Altcode: 2022arXiv220111818B
Global coronal models seek to produce an accurate physical
representation of the Sun's atmosphere that can be used, for example, to
drive space-weather models. Assessing their accuracy is a complex task,
and there are multiple observational pathways to provide constraints
and tune model parameters. Here, we combine several such independent
constraints, defining a model-agnostic framework for standardized
comparison. We require models to predict the distribution of coronal
holes at the photosphere, and neutral line topology at the model's outer
boundary. We compare these predictions to extreme-ultraviolet (EUV)
observations of coronal hole locations, white-light Carrington maps of
the streamer belt, and the magnetic sector structure measured in situ
by Parker Solar Probe and 1 au spacecraft. We study these metrics for
potential field source surface (PFSS) models as a function of source
surface height and magnetogram choice, as well as comparing to the more
physical Wang-Sheeley-Arge (WSA) and the Magnetohydrodynamic Algorithm
outside a Sphere (MAS) models. We find that simultaneous optimization
of PFSS models to all three metrics is not currently possible, implying
a trade-off between the quality of representation of coronal holes
and streamer belt topology. WSA and MAS results show the additional
physics that they include address this by flattening the streamer belt
while maintaining coronal hole sizes, with MAS also improving coronal
hole representation relative to WSA. We conclude that this framework
is highly useful for inter- and intra-model comparisons. Integral to
the framework is the standardization of observables required of each
model, evaluating different model aspects.
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Title: Erratum: "The Role of Alfvén Wave Dynamics on the Large-scale
Properties of the Solar Wind: Comparing an MHD Simulation with Parker
Solar Probe E1 data" (2020, ApJS, 246, 24)
Authors: Réville, Victor; Velli, Marco; Panasenco, Olga; Tenerani,
Anna; Shi, Chen; Badman, Samuel T.; Bale, Stuart D.; Kasper, J. C.;
Stevens, Michael L.; Korreck, Kelly E.; Bonnell, J. W.; Case, Anthony
W.; Dudok de Wit, Thierry; Goetz, Keith; Harvey, Peter R.; Larson,
Davin E.; Livi, Roberto; Malaspina, David M.; MacDowall, Robert J.;
Pulupa, Marc; Whittlesey, Phyllis L.
2022ApJS..259...29R Altcode:
No abstract at ADS
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Title: First Solar Orbiter observation of the Alfvénic slow wind
and identification of its solar source
Authors: D'Amicis, R.; Bruno, R.; Panasenco, O.; Telloni, D.; Perrone,
D.; Marcucci, M. F.; Woodham, L.; Velli, M.; De Marco, R.; Jagarlamudi,
V.; Coco, I.; Owen, C.; Louarn, P.; Livi, S.; Horbury, T.; André,
N.; Angelini, V.; Evans, V.; Fedorov, A.; Genot, V.; Lavraud, B.;
Matteini, L.; Müller, D.; O'Brien, H.; Pezzi, O.; Rouillard, A. P.;
Sorriso-Valvo, L.; Tenerani, A.; Verscharen, D.; Zouganelis, I.
2021A&A...656A..21D Altcode:
Context. Turbulence dominated by large-amplitude, nonlinear Alfvén-like
fluctuations mainly propagating away from the Sun is ubiquitous
in high-speed solar wind streams. Recent studies have demontrated
that slow wind streams may also show strong Alfvénic signatures,
especially in the inner heliosphere. <BR /> Aims: The present study
focuses on the characterisation of an Alfvénic slow solar wind interval
observed by Solar Orbiter between 14 and 18 July 2020 at a heliocentric
distance of 0.64 AU. <BR /> Methods: Our analysis is based on plasma
moments and magnetic field measurements from the Solar Wind Analyser
(SWA) and Magnetometer (MAG) instruments, respectively. We compared
the behaviour of different parameters to characterise the stream
in terms of the Alfvénic content and magnetic properties. We also
performed a spectral analysis to highlight spectral features and
waves signature using power spectral density and magnetic helicity
spectrograms, respectively. Moreover, we reconstruct the Solar Orbiter
magnetic connectivity to the solar sources both via a ballistic
and a potential field source surface (PFSS) model. <BR /> Results:
The Alfvénic slow wind stream described in this paper resembles, in
many respects, a fast wind stream. Indeed, at large scales, the time
series of the speed profile shows a compression region, a main portion
of the stream, and a rarefaction region, characterised by different
features. Moreover, before the rarefaction region, we pinpoint several
structures at different scales recalling the spaghetti-like flux-tube
texture of the interplanetary magnetic field. Finally, we identify the
connections between Solar Orbiter in situ measurements, tracing them
down to coronal streamer and pseudostreamer configurations. <BR />
Conclusions: The characterisation of the Alfvénic slow wind stream
observed by Solar Orbiter and the identification of its solar source
are extremely important aspects for improving the understanding of
future observations of the same solar wind regime, especially as solar
activity is increasing toward a maximum, where a higher incidence of
this solar wind regime is expected.
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Title: A solar source of Alfvenic magnetic field switchbacks: in
situ remnants of magnetic funnels on supergranulation scales
Authors: Bale, Stuart; Desai, Mihir; Halekas, Jasper; Horbury,
Timothy; McManus, Michael; Panasenco, Olga; Badman, Samuel; Bowen,
Trevor; Drake, James; Kasper, Justin; Laker, Ronan; Mallet, Alfred;
Matteini, Lorenzo; Raouafi, Nour; Squire, Jonathan; Velli, Marco;
Woodham, Lloyd; Woolley, Thomas
2021AGUFMSH33B..04B Altcode:
One of the more striking observations from the NASA Parker Solar Probe
(PSP) spacecraft is the prevalence in the inner heliosphere of large
amplitude, Alfvenic magnetic field reversals termed 'switchbacks'. These
dB/B~1 fluctuations occur on a range of timescales, are spherically
polarized, and occur in patches separated by intervals of more quiet,
radial solar wind magnetic field. We use measurements from the
FIELDS, SWEAP, and ISOIS instrument suites on PSP to demonstrate
that patches of magnetic field switchbacks are localized within
stable solar wind extensions of structures originating at the base
of the corona. These structures are characterized by an increase in
alpha particle abundance, Mach number, plasma beta and pressure, and
by depletions in the magnetic field magnitude and electron core and
strahl temperature. These intervals are in local pressure-balance,
which implies stationary spatial structure, and the central magnetic
field depressions are consistent with overexpanded flux tubes. The
structures are asymmetric in Carrington longitude with the leading
edge being steeper and with a small edge of hotter plasma and enhanced
magnetic field fluctuations. Some of the structures contain suprathermal
ions to ~85 keV. The structures are separated in longitude by angular
scales associated with supergranulation and chromospheric network
magnetic field. This implies both an origin of the streams and suggests
that these magnetic field switchbacks, hot plasma, alpha particles,
and suprathermal ions originate within and near the leading edge of
the diverging magnetic field funnels associated with the photospheric
network magnetic field.
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Title: Radial evolution of switchbacks in the inner heliosphere:
observations from PSP to Ulysses
Authors: Tenerani, Anna; Sioulas, Nikos; Matteini, Lorenzo; Panasenco,
Olga; Shi, Chen; Velli, Marco
2021AGUFMSH35C2092T Altcode:
We have analyzed magnetic field data from the first six encounters
of Parker Solar Probe, three fast streams observed by Helios 1
and 2, and two Ulysses south polar passes to determine the radial
evolution of switchbacks in the range of heliocentric distances
0.1 < R < 3 au. We have compared the radial evolution of the
magnetic field variances with that of the mean square amplitudes
of switchbacks. In addition, we have calculated the occurrence rate
of switchbacks at various radial distances. We find that the radial
amplitudes of switchbacks decrease faster than that of the overall
turbulent fluctuations, following the radial decrease of the mean
(radial) magnetic field. This result is consistent with the expected
saturation of amplitudes, a condition that must be satisfied by
fluctuations like switchbacks that display a constant total magnetic
field strength. Furthermore, we find that the occurrence of switchbacks
in the solar wind is scale-dependent: the fraction of longer duration
switchbacks increases with radial distance, whereas the fraction of
shorter switchbacks decreases with radial distance. Our results show
that switchbacks decay and re-form in the inner heliosphere. We confirm
that they can be generated in-situ by the expansion, although other
types of switchbacks, forming closer to the sun, cannot be ruled out.
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Title: First Solar Orbiter observation of an Alfvenic slow wind stream
Authors: D'Amicis, Raffaella; Bruno, Roberto; Panasenco, Olga;
Telloni, Daniele; Perrone, Denise; Marcucci, Maria Federica; Woodham,
Lloyd; Velli, Marco; De Marco, Rossana; Jagarlamudi, vamsee Krishna;
Coco, Igino; Owen, Christopher; Louarn, Philippe; Livi, Stefano;
Horbury, Timothy; Andre, Nicolas; Angelini, Virginia; Evans, Vincent;
Fedorov, Andrei; Genot, Vincent; Lavraud, Benoit; Matteini, Lorenzo;
Muller, Daniel; O'Brien, Helen; Pezzi, Oreste; Rouillard, Alexis;
Sorriso-Valvo, Luca; Tenerani, Anna; Verscharen, Daniel; Zouganelis,
Yannis
2021AGUFMSH21A..10D Altcode:
Alfvénic turbulence, dominated by large-amplitude Alfvénic
fluctuations mainly propagating away from the Sun, is a feature
characterizing not only the high-speed streams but also some slow
wind intervals. Within this framework, the present study focuses on
an Alfvénic slow solar wind stream observed by Solar Orbiter in July
2020 at a heliocentric distance of 0.64 AU. Using data collected from
the Solar Wind Analyzer (SWA) and the Magnetometer (MAG), we provide
a fully description of this stream from many respects identifying
different regions within the stream characterized by distinct features
using different indicators and including also a spectral analysis
to highlight spectral features and waves signature. In addition,
we pinpoint several structures at different scales recalling the
spaghetti-like flux-tube texture of the interplanetary magnetic field
and we reconstruct the Solar Orbiter magnetic connectivity to the
solar sources both via a ballistic and a potential field source surface
(PFSS) model. The characterization of the Alfvénic slow wind stream
observed by Solar Orbiter and the identification of its solar source
are extremely important for improving the understanding of future
observations of the same solar wind regime and the general problem of
solar wind acceleration. This is particularly relevant for upcoming
Solar Orbiter observations as solar activity is increasing toward a
maximum, where a higher incidence of this solar wind regime has been
observed over previous solar cycles.
---------------------------------------------------------
Title: Patches of the magnetic switchbacks: hints of their origins
Authors: Shi, Chen; Velli, Marco; Panasenco, Olga; Tenerani, Anna;
Bale, Stuart; Larson, Davin; Bowen, Trevor; Whittlesey, Phyllis;
Livi, Roberto; Halekas, Jasper; Kasper, Justin; Stevens, Michael;
Malaspina, David
2021AGUFMSH11A..01S Altcode:
One of the most important findings made by Parker Solar Probe (PSP)
is the omni-presence of the magnetic switchbacks, which are the local
backward-bends of the magnetic field lines. Although many studies were
conducted on the properties and dynamics of these switchbacks, how and
where they are generated are still not fully understood yet. In this
study, we analyze the data from the first seven encounters of PSP with a
focus on the properties of the switchback patches, i.e., the large-scale
modulation of the switchbacks. We select the time intervals when clear
switchback patches are observed by PSP. We show that the appearance
of switchbacks is frequently modulated on a timescale of several hours
and this timescale seems to be independent on whether PSP is near the
perihelion or near the radial-scan part of its orbit, implying that the
patch of switchbacks likely corresponds to some transient phenomenon
on the Sun. We find that between two consecutive patches, the magnetic
field is usually very quiet with weak fluctuations. We compare various
parameters between the quiet intervals and the switchback intervals. The
results show: (1) The quiet intervals are typically less Alfvénic
than the switchback intervals. (2) The magnetic power spectra for the
switchback intervals usually show a shallower large-scale range and
a steeper small-scale range with a break frequency at around 10-2 Hz
while the power spectra for the quiet intervals typically do not show
such a break. (3) In some intervals, an anti-correlation between the
alpha-particle abundance and the switchback patches is observed. We
calculate the magnetic footpoints of PSP using the PFSS model and
discuss the possible correlation between the switchback patches and
the supergranules.
---------------------------------------------------------
Title: Solar Filament Channels: Magnetic Forces Shaping Multi-Scale
Coronal Dynamics
Authors: Panasenco, Olga; Habbal, Shadia
2021AGUFMSH25F2148P Altcode:
The solar dynamo and plasma convection produce three main observed
structures extending from the solar surface into the corona active
regions, solar filaments (prominences when observed at the limb)
and coronal holes. Each of these three key features is interlinked
with the other two in its evolution and dynamics. Active regions,
often with underlying sunspots, can form clusters of magnetic
activity. When active regions decay, solar filaments form at their
boundaries separating opposite magnetic polarities. Alternatively,
decaying active regions can give rise to coronal holes in the presence
of the magnetic flux imbalance. Accumulation of the magnetic flux
at the coronal hole boundaries also creates conditions for filament
formations. Polar crown filaments are permanently present at the
boundaries of the polar coronal holes. Polar coronal holes and their
equatorial extensions, middle-latitude and equatorial coronal holes
can create coronal pseudostreamers when have the same polarity. The
pseudostreamer bases at the photospheric level are multipolar, often
observed as tripolar magnetic configurations with two neutral lines
where twin solar filaments can form separating coronal holes. Solar
wind properties measured in situ by multiple spacecraft show that the
soar wind from pseudostreamers could be fast, Alfvenic slow, or in
between. The resulting wind type depends on the presence or absence of
solar filament channels with or without filaments at the pseudostreamer
base. Here we discuss the energization of the solar corona at different
temporal and spatial scales. We present observations of the extended
solar corona and corresponding PFSS modeling of the coronal magnetic
field to resolve a mystery of sharp temperature boundaries between
large-scale coronal structures and their link to the presence or
absence of filament channels.
---------------------------------------------------------
Title: Comparative Study of Electric Currents and Energetic Particle
Fluxes in a Solar Flare and Earth Magnetospheric Substorm
Authors: Artemyev, Anton; Zimovets, Ivan; Sharykin, Ivan; Nishimura,
Yukitoshi; Downs, Cooper; Weygand, James; Fiori, Robyn; Zhang,
Xiao-Jia; Runov, Andrei; Velli, Marco; Angelopoulos, Vassilis;
Panasenco, Olga; Russell, Christopher T.; Miyoshi, Yoshizumi; Kasahara,
Satoshi; Matsuoka, Ayako; Yokota, Shoichiro; Keika, Kunihiro; Hori,
Tomoaki; Kazama, Yoichi; Wang, Shiang-Yu; Shinohara, Iku; Ogawa,
Yasunobu
2021ApJ...923..151A Altcode: 2021arXiv210503772A
Magnetic field line reconnection is a universal plasma process
responsible for the conversion of magnetic field energy to plasma
heating and charged particle acceleration. Solar flares and Earth's
magnetospheric substorms are two of the most investigated dynamical
systems where global magnetic field reconfiguration is accompanied by
energization of plasma populations. Such a reconfiguration includes
formation of a long-living current system connecting the primary
energy release region and cold dense conductive plasma of the
photosphere/ionosphere. In both flares and substorms the evolution
of this current system correlates with the formation and dynamics of
energetic particle fluxes (although energy ranges can be different
for these systems). Our study is focused on the similarity between
flares and substorms. Using a wide range of data sets available for
flare and substorm investigations, we qualitatively compare the
dynamics of currents and energetic particle fluxes for one flare
and one substorm. We show that there is a clear correlation between
energetic particle precipitations (associated with energy release due to
magnetic reconnection seen from riometer and hard X-ray measurements)
and magnetic field reconfiguration/formation of the current system,
whereas the long-term current system evolution correlates better with
hot plasma fluxes (seen from in situ and soft X-ray measurements). We
then discuss how data sets of in situ measurements of magnetospheric
substorms can help interpret solar flare data.
---------------------------------------------------------
Title: A Solar Source of Alfvénic Magnetic Field Switchbacks:
In Situ Remnants of Magnetic Funnels on Supergranulation Scales
Authors: Bale, S. D.; Horbury, T. S.; Velli, M.; Desai, M. I.; Halekas,
J. S.; McManus, M. D.; Panasenco, O.; Badman, S. T.; Bowen, T. A.;
Chandran, B. D. G.; Drake, J. F.; Kasper, J. C.; Laker, R.; Mallet,
A.; Matteini, L.; Phan, T. D.; Raouafi, N. E.; Squire, J.; Woodham,
L. D.; Woolley, T.
2021ApJ...923..174B Altcode: 2021arXiv210901069B
One of the striking observations from the Parker Solar Probe (PSP)
spacecraft is the prevalence in the inner heliosphere of large
amplitude, Alfvénic magnetic field reversals termed switchbacks. These
$\delta {B}_{R}/B\sim { \mathcal O }(1$ ) fluctuations occur over a
range of timescales and in patches separated by intervals of quiet,
radial magnetic field. We use measurements from PSP to demonstrate that
patches of switchbacks are localized within the extensions of plasma
structures originating at the base of the corona. These structures
are characterized by an increase in alpha particle abundance, Mach
number, plasma β and pressure, and by depletions in the magnetic
field magnitude and electron temperature. These intervals are in
pressure balance, implying stationary spatial structure, and the field
depressions are consistent with overexpanded flux tubes. The structures
are asymmetric in Carrington longitude with a steeper leading edge
and a small (~1°) edge of hotter plasma and enhanced magnetic field
fluctuations. Some structures contain suprathermal ions to ~85 keV that
we argue are the energetic tail of the solar wind alpha population. The
structures are separated in longitude by angular scales associated with
supergranulation. This suggests that these switchbacks originate near
the leading edge of the diverging magnetic field funnels associated
with the network magnetic field-the primary wind sources. We propose an
origin of the magnetic field switchbacks, hot plasma and suprathermals,
alpha particles in interchange reconnection events just above the
solar transition region and our measurements represent the extended
regions of a turbulent outflow exhaust.
---------------------------------------------------------
Title: Evolution of Switchbacks in the Inner Heliosphere
Authors: Tenerani, Anna; Sioulas, Nikos; Matteini, Lorenzo; Panasenco,
Olga; Shi, Chen; Velli, Marco
2021ApJ...919L..31T Altcode: 2021arXiv210906341T
We analyze magnetic field data from the first six encounters of Parker
Solar Probe, three Helios fast streams and two Ulysses south polar
passes covering heliocentric distances 0.1 ≲ R ≲ 3 au. We use
this data set to statistically determine the evolution of switchbacks
of different periods and amplitudes with distance from the Sun. We
compare the radial evolution of magnetic field variances with that of
the mean square amplitudes of switchbacks, and quantify the radial
evolution of the cumulative counts of switchbacks per kilometer. We
find that the amplitudes of switchbacks decrease faster than the
overall turbulent fluctuations, in a way consistent with the radial
decrease of the mean magnetic field. This could be the result of a
saturation of amplitudes and may be a signature of decay processes
of large amplitude Alfvénic fluctuations in the solar wind. We find
that the evolution of switchback occurrence in the solar wind is scale
dependent: the fraction of longer-duration switchbacks increases with
radial distance, whereas it decreases for shorter switchbacks. This
implies that switchback dynamics is a complex process involving both
decay and in situ generation in the inner heliosphere. We confirm that
switchbacks can be generated by the expansion, although other types
of switchbacks generated closer to the Sun cannot be ruled out.
---------------------------------------------------------
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
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: Alfvénic versus non-Alfvénic turbulence in the inner
heliosphere as observed by Parker Solar Probe
Authors: Shi, C.; Velli, M.; Panasenco, O.; Tenerani, A.; Réville, V.;
Bale, S. D.; Kasper, J.; Korreck, K.; Bonnell, J. W.; Dudok de Wit, T.;
Malaspina, D. M.; Goetz, K.; Harvey, P. R.; MacDowall, R. J.; Pulupa,
M.; Case, A. W.; Larson, D.; Verniero, J. L.; Livi, R.; Stevens, M.;
Whittlesey, P.; Maksimovic, M.; Moncuquet, M.
2021A&A...650A..21S Altcode: 2021arXiv210100830S
Context. Parker Solar Probe (PSP) measures the magnetic field
and plasma parameters of the solar wind at unprecedentedly close
distances to the Sun. These data provide great opportunities to study
the early-stage evolution of magnetohydrodynamic (MHD) turbulence
in the solar wind. <BR /> Aims: In this study, we make use of the
PSP data to explore the nature of solar wind turbulence focusing
on the Alfvénic character and power spectra of the fluctuations
and their dependence on the distance and context (i.e., large-scale
solar wind properties), aiming to understand the role that different
effects such as source properties, solar wind expansion, and stream
interaction might play in determining the turbulent state. <BR />
Methods: We carried out a statistical survey of the data from the first
five orbits of PSP with a focus on how the fluctuation properties at
the large MHD scales vary with different solar wind streams and the
distance from the Sun. A more in-depth analysis from several selected
periods is also presented. <BR /> Results: Our results show that as
fluctuations are transported outward by the solar wind, the magnetic
field spectrum steepens while the shape of the velocity spectrum
remains unchanged. The steepening process is controlled by the "age"
of the turbulence, which is determined by the wind speed together
with the radial distance. Statistically, faster solar wind has higher
"Alfvénicity," with a more dominant outward propagating wave component
and more balanced magnetic and kinetic energies. The outward wave
dominance gradually weakens with radial distance, while the excess of
magnetic energy is found to be stronger as we move closer toward the
Sun. We show that the turbulence properties can significantly vary
from stream to stream even if these streams are of a similar speed,
indicating very different origins of these streams. Especially, the
slow wind that originates near the polar coronal holes has much lower
Alfvénicity compared with the slow wind that originates from the
active regions and pseudostreamers. We show that structures such as
heliospheric current sheets and velocity shears can play an important
role in modifying the properties of the turbulence.
---------------------------------------------------------
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
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: Alfvénic versus non-Alfvénic turbulence in the inner
heliosphere as observed by Parker Solar Probe
Authors: Velli, Marco; Shi, Chen; Panasenco, Olga; Tenerani, Anna;
Reville, Victor; the PSP* Team
2021EGUGA..2312876V Altcode:
Parker Solar Probe (PSP) measures the magnetic field and plasma
parameters of the solar wind at unprecedentedly close distances to the
Sun, providing a great opportunity to study the early-stage evolution
of magnetohydrodynamic (MHD) turbulence in the solar wind. Here we use
PSP data to explore the nature of solar wind turbulence focusing on the
Alfvénic character and power spectra of the fluctuations and their
dependence on heliocentric distance and context (i.e., large-scale
solar wind properties), aiming to understand the role that different
effects such as source properties, solar wind expansion, and stream
interaction might play in determining the turbulent state. We carried
out a statistical survey of the data from the first five orbits of
PSP with a focus on how the fluctuation properties at the large MHD
scales vary with different solar wind streams and the distance from
the Sun. A more in-depth analysis from several selected periods is
also presented. Our results show that as fluctuations are transported
outward by the solar wind, the magnetic field spectrum steepens while
the shape of the velocity spectrum remains unchanged. The steepening
process is controlled by the age of the turbulence, which is determined
by the wind speed together with the radial distance. Statistically,
faster solar wind has higher Alfvénicity with a more dominant
outward propagating wave component and more balanced magnetic and
kinetic energies. The outward wave dominance gradually weakens with
radial distance, while the excess of magnetic energy is found to be
stronger as we move closer toward the Sun. We show that the turbulence
properties can significantly vary from stream to stream even if these
streams are of a similar speed, indicating very different origins of
these streams. Especially, the slow wind that originates near the polar
coronal holes has much lower Alfvénicity compared with the slow wind
that originates from the active regions and pseudostreamers. We show
that structures such as the heliospheric current sheet and wind stream
velocity shears can play an important role in modifying the properties
of the turbulence.*The PSP Team: Stuart D.Bale, Justin Kasper, Kelly
Korreck, J. W. Bonnell, Thierry Dudok de Wit, Keith Goetz, Peter
R. Harvey, Robert J. MacDowall, David Malaspina, Marc Pulupa, Anthony
W.Case, Davin Larson, Jenny Verniero, Roberto Livi, Michael Stevens,
PhyllisWhittlesey, Milan Maksimovic, and Michel Moncuquet
---------------------------------------------------------
Title: Radial evolution of switchbacks in the inner heliosphere:
observations from PSP to Ulysses
Authors: Tenerani, Anna; Sioulas, Nikos; Matteini, Lorenzo; Panasenco,
Olga; Shi, Chen; Velli, Marco
2021APS..DPPTO6002T Altcode:
Measurements from Parker Solar Probe have shown the ubiquitous presence
of the so-called switchbacks. These are magnetic field lines which are
strongly perturbed to the point that they lead to local inversions
of the radial magnetic field. The corresponding signature in the
velocity field is that of a local radial speed jet displaying the
well-known velocity/magnetic field correlation that characterizes
Alfvén waves propagating away from the Sun. While there is not yet a
general consensus on the origins of switchbacks and their connection
to coronal activity, a first necessary step is to understand how
they evolve and how long they can propagate undisturbed in the solar
wind. Characterizing the dynamical evolution of switchbacks in the
solar wind can help us determine whether they are generated in-situ or
not, and whether they contribute to the turbulent cascade by evolving
nonlinearly. In this work, we have analyzed magnetic field data from the
first six encounters of Parker Solar Probe, three fast streams observed
by Helios 1 and 2, and two Ulysses south polar passes, covering the
range of heliocentric distances 0.1 < R < 3 au. We have compared
the radial evolution of the magnetic energy density of switchbacks with
that of the overall turbulent fluctuations, and we have characterized
the radial evolution of the occurrence rate of switchbacks as a function
of their duration. Our results show that switchbacks both decay and
reform in-situ in the inner heliosphere, in-situ generation being more
efficient at the larger scales. Our results confirm that switchbacks
can be generated in the inner heliosphere by the expansion, although
other types of switchbacks, generated closer to the sun, cannot be ruled
out. <P />This research was supported by NASA Grant #80NSS-C18K1211.
---------------------------------------------------------
Title: The solar wind observed over the first orbits by Parker Solar
Probe : new insights into the origin of the heliosphere
Authors: Velli, Marco; Panasenco, Olga; Tenerani, Anna; Shi, Chen
2021cosp...43E.932V Altcode:
Since the launch of Parker Solar Probe (PSP) in 2018, a new window
has opened into understanding the inner heliosphere.The first
Probe encounters, with a perihelion at 35.6 Solar Radii (Rs) from
Sun-center illustrated the complexity of the mapping of the magnetic
field at the Sun even into the inner heliosphere. In Encounter (E)
1, Probe connected to a small, overexpanding coronal hole, and the
resulting slow solar wind flow was dominated by highly Alfvénic
fluctuations, including local radial magnetic field inversions
called switchbacks. Recent Encounters E4 and E5, with perihelia at
a distance of 27.8 Rs, show the importance of the mixing of spatial
and intrinsically time-dependent behavior. Here we describe the
general features of the solar wind seen by PSP in orbits 4 and 5,
with specific emphasis on the polarity of the field, the properties of
the fluctuations observed, and their association with the regions of
origin of the wind and with intrinsically time-dependent processes
at the source. We use the Potential Field Source-Surface (PFSS)
model of De Rosa and Schrijver, based on SDO/HMI magnetogram data in
conjunction photospheric transport, to extrapolate the field from the
solar surface out to an appropriate source surface, and then images
from STEREO, LASCO and SDO/AIA to compare the results with the magnetic
field and plasma seen by Probe. In situ measurements are then used
to compute plasma and turbulence properties, such as Alfvénicity,
and determine the nature of the discontinuities separating different
types of solar wind flows in situ. Probe in E4 and E5 remained very
close to the heliospheric current sheet, and traversed structures
such as pseudostreamer stalks as well as the heliospheric current
sheet itself. It observed both strongly Alfvénic wind and wind with
less clear Alfvénic character. When compared to the first encounter,
the solar wind conditions seen by Probe at the most recent E4 and E5 is
more typical of the wind seen in the ecliptic in periods of increasing
solar activity. Switchbacks are confirmed to be an intrinsic feature
of the nascent solar wind everywhere except above helmet streamers. To
conclude we will discuss how new PSP measurements change our views of
heliospheric magnetic field expansion and solar wind acceleration.
---------------------------------------------------------
Title: MHD Turbulence in the Solar Wind: Observations from First
Five Encounters of Parker Solar Probe
Authors: Shi, C.; Velli, M. C. M.; Panasenco, O.; Tenerani, A.;
Halekas, J. S.; Stevens, M. L.; Whittlesey, P. L.; Livi, R.; Bowen,
T. A.; Bale, S. D.
2020AGUFMSH033..05S Altcode:
Parker Solar Probe (PSP) has finished its first five orbits, reaching
~28 solar radii to the Sun, much lower than any previous spacecraft. The
magnetic field and plasma data collected by PSP provide us with great
opportunities to study the properties and evolution of turbulence in
the young solar wind. Here, we present a statistical analysis of the
PSP data from its first five orbits. We focus on the question that how
the MHD turbulence properties vary with different solar wind streams,
i.e. fast and slow streams. Our results show that, although the plasma
properties, e.g. ion temperature and compressibility, vary significantly
with the solar wind speed, the turbulence properties do not have a
strong wind-speed dependence. The observed faster radial steepening
of magnetic field power spectrum in the slow wind indicates that the
"age" of the turbulence, determined by the wind speed together with the
radial distance, controls the turbulence properties. We observe that as
we get closer to the Sun, the spectral slopes of the magnetic field and
velocity tend to converge to a value ~1.5 and the residual energy rises
from negative values toward 0. This result confirms that the observed
asymmetry between kinetic and magnetic energies and power spectra
beyond 0.3 AU is a result of dynamic evolution of the turbulence.
---------------------------------------------------------
Title: Sources and Evolution of the Solar Wind Seen by Parker
Solar Probe
Authors: Panasenco, O.; Velli, M. C. M.; Shi, C.; Tenerani, A.;
Réville, V.; Badman, S. T.; Bale, S. D.; D'Amicis, R.; Goetz, K.;
Harvey, P.; Korreck, K. E.; Larson, D. E.; MacDowall, R. J.; Pulupa,
M.; Halekas, J. S.; Stevens, M. B.; Livi, R.; Whittlesey, P. L.
2020AGUFMSH0290026P Altcode:
Parker Solar Probe (PSP) has made a number of important discoveries in
its exploration of the inner heliosphere/outer corona inside 36 Rs. Its
observation of ubiquitous large amplitude Alfvénic fluctuations,
regardless of solar wind speed, in all wind streams except for narrow
areas surrounding the heliospheric current sheet, together with large
s-shaped inversions of the magnetic field, called switchbacks, begin to
call into questions standard ideas of solar wind acceleration. In this
presentation we use a wealth of remote sensing and in-situ measurements
to pinpoint the sources of the wind observed by PSP. We then discuss
the origin and evolution of so-called slow Alfvénic wind, the origin
of switchbacks, and the role of magnetic reconnection in the formation
of the solar wind.
---------------------------------------------------------
Title: Solar wind Alfvénic turbulence: overcoming an old paradigm
Authors: D'Amicis, R.; Bruno, R.; Matteini, L.; Perrone, D.; Velli,
M. C. M.; Telloni, D.; Panasenco, O.
2020AGUFMSH033..01D Altcode:
Despite many decades of studies, solar wind turbulence remains an open,
unsolved problem in space plasma physics. The solar wind turbulent
behavior is in many instances dominated by the nonlinear interaction
between inward and outward propagating Alfvén waves, especially
so-called Alfvénic turbulence, that displays a high degree of v-b
correlations (and almost constant number density and magnetic field
magnitude). Also, Alfvénic turbulence is especially prominent in fast
solar wind streams. Such characteristics have strong implications
for spectral features and has motivated the turbulent community to
take a particular care of data selection, separating the streams
according to their speed. However, recent results have shown that the
slow-fast dichotomy should be overcome. Indeed, it has been found that
even slow wind can be sometimes characterized by highly Alfvénic and
high-amplitude fluctuations similar to that of the fast wind. Although
the first observation of this kind of wind dates back to Helios data at
the perihelion passage, L1 measurements during solar maximum revealed,
quite unexpectedly, a statistically significant occurrence of this
kind of wind. <P />On the other hand, recent observations by Parker
Solar Probe (PSP) show the occurrence of Alfvénic slow wind at all
the perihelion passages, putting this topic in the spotlight. In this
talk, we review the main characteristics of the Alfvénic slow wind
from L1 back to PSP closest approach, with a particular focus on the
comparison with the fast wind and the standard slow wind. The several
similarities between the two Alfvénic winds (fast and slow) suggest
a similar origin, with the slow one coming from a low latitude small
coronal hole, with a major role attributed to the super-radial expansion
responsible for the lower velocity of the slow wind. This interpretation
was confirmed by PSP observations. The upcoming Solar Orbiter data will
be of further support in characterizing this kind of slow wind and in
following the radial evolution of Alfvénicity in the inner heliosphere.
---------------------------------------------------------
Title: Constraining Global Coronal Models with Multiple Independent
Observables
Authors: Badman, S. T.; Brooks, D.; Petrie, G. J. D.; Poirier, N.;
Warren, H.; Bale, S. D.; de Pablos, D.; Harra, L.; Rouillard, A. P.;
Panasenco, O.; Velli, M. C. M.
2020AGUFMSH032..08B Altcode:
Global coronal models seek to produce an accurate physical
representation of the Sun's atmosphere which can be used to probe
the dominant plasma physics processes, to connect remote and in situ
observations and operationally to predict space weather events which
can impact the Earth. Assessing their accuracy and usefulness is a
complex task and there are multiple observational pathways to provide
constraints on such models and tune their input parameters. In this
work, we aim to combine several such independent constraints in
a systematic fashion on coronal models. We study the intervals of
Parker Solar Probe's early solar encounters to leverage the unique in
situ observations taken close to the Sun, and the wealth of supporting
observations and prior work analyzing these time intervals. We require
our coronal models to predict the distribution of coronal holes on
the solar surface, and the neutral line topology. We compare these
predictions to (1) direct Extreme Ultraviolet (EUV) observations
of coronal hole locations, (2) white light Carrington maps of the
probable neutral line location at a few solar radii, (3) the magnetic
sector structure measured in situ by Parker Solar Probe as well as
1AU assets. For each of these constraints we compute a simple metric
to evaluate model agreement and compare and contrast these metrics
to evaluate and rank the overall accuracy of the models over a range
of input parameters. Initial results using the coronal hole metric
to analyze Potential Field Source Surface (PFSS) models indicate the
optimum source surface height (Rss) parameter varied from encounter to
encounter. Rss = 1.5 - 2.0 R_sun is shown to work best for Encounters
1 and 3, but higher (2.0-2.5 R_sun) for encounter 2, in agreement with
the magnetic sector structure metric and previous work (e.g. Panasenco
et al. 2020). We discuss the extension of these results to all three
metrics, assess differences in model accuracy among input photospheric
boundary conditions and investigate models with more physics than PFSS.
---------------------------------------------------------
Title: Understanding the origins of the heliosphere: integrating
observations and measurements from Parker Solar Probe, Solar Orbiter,
and other space- and ground-based observatories
Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron,
N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.;
St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; 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.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper,
J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.;
De Groof, A.; Williams, D.
2020A&A...642A...4V Altcode:
Context. The launch of Parker Solar Probe (PSP) in 2018, followed
by Solar Orbiter (SO) in February 2020, has opened a new window in
the exploration of solar magnetic activity and the origin of the
heliosphere. These missions, together with other space observatories
dedicated to solar observations, such as the Solar Dynamics Observatory,
Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations
from WIND and ACE, and ground based multi-wavelength observations
including the DKIST observatory that has just seen first light,
promise to revolutionize our understanding of the solar atmosphere
and of solar activity, from the generation and emergence of the Sun's
magnetic field to the creation of the solar wind and the acceleration of
solar energetic particles. <BR /> Aims: Here we describe the scientific
objectives of the PSP and SO missions, and highlight the potential for
discovery arising from synergistic observations. Here we put particular
emphasis on how the combined remote sensing and in situ observations of
SO, that bracket the outer coronal and inner heliospheric observations
by PSP, may provide a reconstruction of the solar wind and magnetic
field expansion from the Sun out to beyond the orbit of Mercury in the
first phases of the mission. In the later, out-of-ecliptic portions of
the SO mission, the solar surface magnetic field measurements from SO
and the multi-point white-light observations from both PSP and SO will
shed light on the dynamic, intermittent solar wind escaping from helmet
streamers, pseudo-streamers, and the confined coronal plasma, and on
solar energetic particle transport. <BR /> Methods: Joint measurements
during PSP-SO alignments, and magnetic connections along the same
flux tube complemented by alignments with Earth, dual PSP-Earth,
and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will
allow a better understanding of the in situ evolution of solar-wind
plasma flows and the full three-dimensional distribution of the
solar wind from a purely observational point of view. Spectroscopic
observations of the corona, and optical and radio observations,
combined with direct in situ observations of the accelerating solar
wind will provide a new foundation for understanding the fundamental
physical processes leading to the energy transformations from solar
photospheric flows and magnetic fields into the hot coronal plasma
and magnetic fields and finally into the bulk kinetic energy of the
solar wind and solar energetic particles. <BR /> Results: We discuss
the initial PSP observations, which already provide a compelling
rationale for new measurement campaigns by SO, along with ground-
and space-based assets within the synergistic context described above.
---------------------------------------------------------
Title: Exploring Solar Wind Origins and Connecting Plasma Flows
from the Parker Solar Probe to 1 au: Nonspherical Source Surface
and Alfvénic Fluctuations
Authors: Panasenco, Olga; Velli, Marco; D'Amicis, Raffaella; Shi,
Chen; Réville, Victor; Bale, Stuart D.; Badman, Samuel T.; Kasper,
Justin; Korreck, Kelly; Bonnell, J. W.; Wit, Dudok de Thierry; Goetz,
Keith; Harvey, Peter R.; MacDowall, Robert J.; Malaspina, David M.;
Pulupa, Marc; Case, Anthony W.; Larson, Davin; Livi, Roberto; Stevens,
Michael; Whittlesey, Phyllis
2020ApJS..246...54P Altcode:
The magnetic field measurements of the FIELDS instrument on the
Parker Solar Probe (PSP) have shown intensities, throughout its first
solar encounter, that require a very low source surface (SS) height (
${R}_{\mathrm{SS}}\leqslant 1.8\,{R}_{\odot }$ ) to be reconciled with
magnetic field measurements at the Sun via potential field extrapolation
(PFSS). However, during PSP's second encounter, the situation
went back to a more classic SS height ( ${R}_{\mathrm{SS}}\leqslant
2.5\,{R}_{\odot }$ ). Here we use high-resolution observations of the
photospheric magnetic field (Solar Dynamics Observatory/Helioseismic
and Magnetic Imager) to calculate neutral lines and boundaries of the
open field regions for SS heights from 1.2 to 2.5 R<SUB>⊙</SUB> using
an evolving PFSS model and the measured solar wind speed to trace the
source of the wind observed by PSP to the low corona and photosphere. We
adjust R<SUB>SS</SUB> to get the best match for the field polarity
over the period 2018 October-November and 2019 March-April, finding
that the best fit for the observed magnetic field polarity inversions
requires a nonspherical SS. The geometry of the coronal hole boundaries
for different R<SUB>SS</SUB> is tested using the PSP perihelion passes,
3D PFSS models, and LASCO/C2 observations. We investigate the sources
of stronger-than-average magnetic fields and times of Alfvénic fast
and slow wind. Only some of the strongly Alfvénic slow wind streams
seen by PSP survive and are observed at 1 au: the origins and peculiar
topology of the background in which they propagate is discussed.
---------------------------------------------------------
Title: Magnetic Connectivity of the Ecliptic Plane within 0.5 au:
Potential Field Source Surface Modeling of the First Parker Solar
Probe Encounter
Authors: Badman, Samuel T.; Bale, Stuart D.; Martínez Oliveros, Juan
C.; Panasenco, Olga; Velli, Marco; Stansby, David; Buitrago-Casas,
Juan C.; Réville, Victor; Bonnell, John W.; Case, Anthony W.; Dudok
de Wit, Thierry; Goetz, Keith; Harvey, Peter R.; Kasper, Justin
C.; Korreck, Kelly E.; Larson, Davin E.; Livi, Roberto; MacDowall,
Robert J.; Malaspina, David M.; Pulupa, Marc; Stevens, Michael L.;
Whittlesey, Phyllis L.
2020ApJS..246...23B Altcode: 2019arXiv191202244B
We compare magnetic field measurements taken by the FIELDS instrument
on board Parker Solar Probe (PSP) during its first solar encounter
to predictions obtained by potential field source surface (PFSS)
modeling. Ballistic propagation is used to connect the spacecraft to the
source surface. Despite the simplicity of the model, our results show
striking agreement with PSP's first observations of the heliospheric
magnetic field from ∼0.5 au (107.5 R<SUB>⊙</SUB>) down to 0.16
au (35.7 R<SUB>⊙</SUB>). Further, we show the robustness of the
agreement is improved both by allowing the photospheric input to the
model to vary in time, and by advecting the field from PSP down to
the PFSS model domain using in situ PSP/Solar Wind Electrons Alphas
and Protons measurements of the solar wind speed instead of assuming
it to be constant with longitude and latitude. We also explore
the source surface height parameter (R<SUB>SS</SUB>) to the PFSS
model, finding that an extraordinarily low source surface height
(1.3-1.5 R<SUB>⊙</SUB>) predicts observed small-scale polarity
inversions, which are otherwise washed out with regular modeling
parameters. Finally, we extract field line traces from these models. By
overlaying these on extreme ultraviolet images we observe magnetic
connectivity to various equatorial and mid-latitude coronal holes,
indicating plausible magnetic footpoints and offering context for
future discussions of sources of the solar wind measured by PSP.
---------------------------------------------------------
Title: The Role of Alfvén Wave Dynamics on the Large-scale Properties
of the Solar Wind: Comparing an MHD Simulation with Parker Solar
Probe E1 Data
Authors: Réville, Victor; Velli, Marco; Panasenco, Olga; Tenerani,
Anna; Shi, Chen; Badman, Samuel T.; Bale, Stuart D.; Kasper, J. C.;
Stevens, Michael L.; Korreck, Kelly E.; Bonnell, J. W.; Case, Anthony
W.; de Wit, Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Larson,
Davin E.; Livi, Roberto; Malaspina, David M.; MacDowall, Robert J.;
Pulupa, Marc; Whittlesey, Phyllis L.
2020ApJS..246...24R Altcode: 2019arXiv191203777R
During Parker Solar Probe's first orbit, the solar wind plasma
was observed in situ closer than ever before, the perihelion on
2018 November 6 revealing a flow that is constantly permeated by
large-amplitude Alfvénic fluctuations. These include radial magnetic
field reversals, or switchbacks, that seem to be a persistent feature
of the young solar wind. The measurements also reveal a very strong,
unexpected, azimuthal velocity component. In this work, we numerically
model the solar corona during this first encounter, solving the MHD
equations and accounting for Alfvén wave transport and dissipation. We
find that the large-scale plasma parameters are well reproduced,
allowing the computation of the solar wind sources at Probe with
confidence. We try to understand the dynamical nature of the solar
wind to explain both the amplitude of the observed radial magnetic
field and of the azimuthal velocities.
---------------------------------------------------------
Title: The role of Alfvén wave dynamics in the large scale properties
of the solar wind: comparing 3D MHD simulation and PSP data
Authors: Réville, V.; Velli, M.; Panasenco, O.; Tenerani, A.; Shi,
C.; Rouillard, A. P.; Bale, S. D.; Kasper, J. C.; Badman, S. T.;
Korreck, K. E.; Pulupa, M.; Bonnell, J. W.; Case, A. W.; Larson,
D. E.; Livi, R.; Stevens, M. L.; Whittlesey, P. L.; Malaspina, D.;
Harvey, P.; Goetz, K.; Dudok de Wit, T.; MacDowall, R. J.
2019AGUFMSH51A..03R Altcode:
The first two encounters of Parker Solar Probe have shown features
that already challenge our understanding of the solar wind. During
E1, PSP went through a slow Alfvénic solar wind, likely coming from
equatorial regions. Large amplitude Alfvén waves are present over
many frequencies and show a spherical polarization consistent with
non-linear solutions of the MHD equations. To study this phenomenon we
use 3D MHD simulations of the solar corona, including the propagation
and the dissipation of Alfvén waves to power the solar wind. We first
check the agreement of the simulations with coronal images obtained
from EUV instruments as well as white light images obtained with WISPR
onboard PSP. We then can find the sources of the observed solar wind and
compare with simpler potential field models (PFSS). Finally, we propose
a way to interpret the differences in the properties of the simulations
and the observed data, by accounting for the wave dynamics in the large
scale (or average) solar wind properties. This could lead to important
progress regarding the open flux problem and the computation of the
solar wind angular momentum. <P />This research was supported by NASA
Parker Solar Probe Observatory Scientist grant NNX 15AF34G and by the
European Research Council (ERC) project SLOW_SOURCE - DLV-819189 .
---------------------------------------------------------
Title: Coronal Origins of the Alfvénic Slow Solar Wind
Authors: Panasenco, O.; Velli, M.; D'Amicis, R.
2019AGUFMSH44A..04P Altcode:
As demonstrated by the Ulysses mission the filling factor of the
slow wind in the heliosphere is too large to arise only from the
helmet streamer cusps, so magnetic field and plasma transport and
instabilities involving processes at coronal hole boundaries and quiet
sun must be at work. Outwardly propagating Alfvénic fluctuations are
usually hosted by fast solar wind streams, however a number of slow
solar wind periods have been identified where the turbulence is also
dominated by outward Alfvénic modes (Marsch et al. 1981, D'Amicis and
Bruno 2015 and initial Parker Solar Probe results Bale et al. 2019). 80%
of the wind at Helios was shown to be Alfvénic (Stansby et al. 2019)
and ~ 37% Alfvenic slow. Is the difference between Alfvénic slow wind
and standard slow wind associated with a different dynamics, or is
the coronal topology at the source completely different, as initial
indications seem to show? <P />Here we discuss magnetic topology
and properties of the coronal sources for the peculiar Alfvénic
slow solar wind. We illustrate the specific role played by different
coronal hole types (polar CHs, equatorial extensions of polar CHs,
isolated CHs both at high latitude and close to the equator), as well
as by solar filaments and active regions at coronal hole boundaries,
that strongly influence the magnetic topology of the lower corona and
solar wind properties. Pseudostreamers (PSs) are multipolar features,
which develop into open fields that are unipolar at greater heights
requiring the presence of two or more nearby coronal holes of the same
polarity. MHD solar wind models along magnetic field lines show that
the properties of the solar wind emanating from CHs with pseudostreamers
are different from regular CHs (Panasenco et al. 2019). Here we explain
the coronal conditions required for the development of Alfvénic slow
solar wind.
---------------------------------------------------------
Title: Magnetic connectivity of the ecliptic plane within 0.5 AU :
PFSS modelling of the early PSP encounters
Authors: Badman, S. T.; Bale, S. D.; Martinez Oliveros, J. C.;
Panasenco, O.; Velli, M.; Stansby, D.; Buitrago-Casas, J. C.; Réville,
V.; Pulupa, M.; Malaspina, D.; Bonnell, J. W.; Harvey, P.; Goetz,
K.; Dudok de Wit, T.; MacDowall, R. J.; Kasper, J. C.; Case, A. W.;
Korreck, K. E.; Larson, D. E.; Livi, R.; Stevens, M. L.; Whittlesey,
P. L.
2019AGUFMSH13C3453B Altcode:
We compare Parker Solar Probe (PSP) FIELDS early magnetic field
measurements to predictions obtained by Potential Field Source Surface
modeling (PFSS). Ballistic propagation (Parker spiral assumption)
is used to connect the spacecraft to the source surface. Despite the
simplicity of the model, our results show striking agreement with PSP's
first observations of the heliospheric magnetic field from 0.5 AU down
to 0.16 AU. Further, we show the robustness of the agreement is improved
both by allowing the photospheric input to the model to vary in time,
and by advecting the field from PSP down to the PFSS model domain
using in situ PSP/SWEAP measurements of the solar wind speed instead
of assuming it to be constant with longitude and latitude. We also
explore the source surface height parameter to the PFSS model: Overall,
we find evidence that a lower source surface height (< 2 solar radii)
provides improvements to the prediction. We find for PSP Encounter 1
(Nov. 2018) that an extraordinarily low source surface height (1.3-1.5
solar radii) predicts observed small scale polarity inversions which
are otherwise washed out with regular modeling parameters. Finally,
we extract field line traces from these models. By overlaying these
on EUV images we observe magnetic connectivity to various equatorial
and mid-latitude coronal holes, providing a sanity check and offering
context for future discussions of sources of the solar wind measured
by PSP.
---------------------------------------------------------
Title: Large-scale Magnetic Funnels in the Solar Corona
Authors: Panasenco, Olga; Velli, Marco; Panasenco, Aram
2019ApJ...873...25P Altcode:
We describe open coronal magnetic fields with a specific
geometry—large-scale coronal magnetic funnels—that are found to play
an important role in coronal dynamics. Coronal magnetic funnels can be
attributed to three main factors: (i) the presence of pseudostreamer(s),
(ii) the presence of filament channels, and (iii) the presence of
active regions in the close vicinity of a pseudostreamer. The geometry
of magnetic funnels displays a strongly nonmonotonic expansion below 2
R <SUB>⊙</SUB>. We present a detailed study of a funnel arising from
a double pseudostreamer near the equator, formed between a triplet of
coronal holes of the same polarity. By following the evolution of these
coronal holes we find that the pseudostreamer and, therefore, funnel
topology, changes when two coronal holes have merged together. The
funnel geometry of the open magnetic field becomes smoother, with
a monotonic expansion factor, after this merging. The presence of
magnetic funnels is indirectly confirmed by the appearance of coronal
cloud prominences in the solar corona, typically in the 304 Å passband,
as a result of colder plasma debris falling back toward the Sun in the
wake of eruptions in the surrounding atmosphere. The coronal clouds
appear suspended at heights of 1.2-1.3 R <SUB>⊙</SUB>, coinciding
with the region of strongest gradients in the magnetic field. By
studying the evolution of funnel open magnetic fields over several
solar rotations we find a direct relation between the presence of
coronal clouds high in the solar corona and the coincident existence
of funnel magnetic fields below them.
---------------------------------------------------------
Title: Observations of Solar Wind from Earth-directed Coronal
Pseudostreamers
Authors: Wang, Y. -M.; Panasenco, O.
2019ApJ...872..139W Altcode:
Low-speed (≲450 km s<SUP>-1</SUP>) solar wind is widely considered
to originate from streamer loops that intermittently release their
contents into the heliosphere, in contrast to high-speed wind, which
has its source in large coronal holes. To account for the presence of
slow wind far from the heliospheric current sheet (HCS), it has been
suggested that “pseudostreamers” rooted between coronal holes
of the same polarity continually undergo interchange reconnection
with the adjacent open flux, producing a wide band of slow wind
centered on the separatrix/plasma sheet that extends outward from
the pseudostreamer cusp. Employing extreme-ultraviolet images and
potential-field source-surface extrapolations, we have identified 10
Earth-directed pseudostreamers during 2013-2016. In situ measurements
show wind speeds ranging from ∼320 to ∼600 km s<SUP>-1</SUP> in the
days immediately preceding and following the predicted pseudostreamer
crossings, with the proton densities and O<SUP>7+</SUP>/O<SUP>6+</SUP>
ratios tending to be inversely correlated with the bulk speed. We also
identify examples of coronal holes that straddle the solar equator and
give rise to wind speeds of order 400 km s<SUP>-1</SUP>. Our results
support the idea that the bulk of the slow wind observed more than a
few degrees from the HCS originates from just inside coronal holes.
---------------------------------------------------------
Title: Pseudostreamers and widely distributed SEP events
Authors: Panasenco, Olga; Panasenco, Aram; Velli, Marco
2018cosp...42E2565P Altcode:
Our analysis of the pseudostreamer magnetic topology reveals new
interesting implications for understanding SEP acceleration in
CMEs. The possible reasons for the wide distribution of some SEP
events can be the presence of pseudostreamers in the vicinity of the
SEP source region which creates conditions for the existence of strong
longitudinal spread of energetic particles as well as an anomalous
longitudinal solar wind magnetic field component. We reconstructed
the 3D magnetic configurations of pseudostreamers with a potential
field source surface (PFSS) model, which uses as a lower boundary
condition the magnetic field derived from an evolving surface-flux
transport model. In order to estimate the possible magnetic connections
between the spacecraft and the SEP source region, we used the Parker
spiral, ENLIL and PFSS models. We found that in cases of the wide SEP
distributions a specific configuration of magnetic field appears to
exist at low solar latitudes all the way around the sun, we named this
phenomenon a pseudostreamers belt. It appears that the presence of the
well developed pseudostreamer or, rather multiple pseudostreamers,
organized into the pseudostreamer belt can be considered as a very
favorable condition for wide SEP events.
---------------------------------------------------------
Title: In situ categorization and coronal origins of different slow
solar wind types
Authors: Panasenco, Olga; Tenerani, Anna; Velli, Marco; Panasenco, Aram
2018shin.confE.236P Altcode:
The slow solar wind is not as regular as the fast wind, and a number
of periods have been identified where the turbulence is essentially
Alfvénic (Marsch et al. 1981, D'Amicis and Bruno, 2015). What creates
the difference between “standard" and Alfvénic slow wind? Is the
---------------------------------------------------------
Title: Large-Scale Magnetic Funnels in the Solar Corona
Authors: Panasenco, Olga; Panasenco, Aram; Velli, Marco
2018cosp...42E2566P Altcode:
The existence of open coronal magnetic fields with peculiar geometry -
large-scale coronal magnetic funnels - can be attributed to two main
factors: (i) the presence of two or more coronal holes of the same
polarity forming coronal pseudostreamers, (ii) specific configurations
of closed magnetic field in the low corona - filament channels. The
important property of magnetic funnels is their strongly non-monotonic
expansion factor below 2 solar radii. In the case study presented here
we consider a double pseudostreamer near the equator, formed between a
triplet of isolated coronal holes of the same polarity, and harboring
two pairs of twin filaments in its base. Following the evolution of
these coronal holes we find that the pseudostreamer and, therefore,
magnetic funnel topology, changes when two coronal holes have merged
together. Using a potential field source-surface (PFSS) extrapolation
to compute the coronal field from photospheric maps (SDO/HMI), we show
that the funnel - like geometry of the open magnetic field changes
to a regular one with monotonic expansion factor after the merging
of coronal holes. The presence of coronal magnetic funnels becomes
directly visible when sufficient plasma accumulates inside them:
when the plasma density grows to become observable, coronal cloud
prominences appear in the corona, mostly in 304 A spectral line. We
study the evolution of the funnel - like open magnetic fields during
several solar rotations and find a direct relation between magnetic
funnels and the presence of coronal clouds at great heights in the
solar corona. 1D numerical analysis of pseudostreamers with funnel
topology shows that the properties of the solar wind from coronal
magnetic funnels depend on the presence/absence of filament channels,
number of channels and chirality at the pseudostreamer base low in
the solar corona.
---------------------------------------------------------
Title: Deprojected Trajectory of Blobs in the Inner Corona
Authors: López-Portela, C.; Panasenco, O.; Blanco-Cano, X.;
Stenborg, G.
2018SoPh..293...99L Altcode:
We have carried out a statistical analysis of the kinematical behavior
of small white-light transients (blobs) as tracers of the slow solar
wind. The characterization of these faint white-light structures gives
us insight on the origin and acceleration of the slow solar wind. The
vantage observing points provided by the SECCHI and LASCO instruments
on board the STEREO and SOHO spacecraft, respectively, allow us to
reconstruct the 3D trajectories of these blob-like features and hence
calculate their deprojected kinematical parameters. We have studied 44
blobs revealed in LASCO C2/C3 and SECCHI COR2 data from 2007 to 2008,
a period within the solar minimum between Solar Cycles 23 and 24. We
found that the blobs propagate along approximately constant position
angles with accelerations from 1.40 to 15.34 ms−<SUP>2</SUP> between
3.42 R<SUB>⊙</SUB> and 14.80 R<SUB>⊙</SUB>, their radial sizes
ranging between 0.57 R<SUB>⊙</SUB> and 1.69 R<SUB>⊙</SUB>. We also
studied the global corona magnetic field morphology for a subset of
blobs using a potential field source surface model for cases where blob
detachments persist for two to five days. The study of localized blob
releases indicates that these plasma structures start their transit
at a distance of ∼3.40 R<SUB>⊙</SUB> and their origin is connected
either with the boundaries of weak coronal holes or with streamers at
equatorial latitudes.
---------------------------------------------------------
Title: SAFARI: Solar Activity Far Side Investigation
Authors: Velli, Marco C. M.; Hassler, Don; Jefferies, Stuart; Murphy,
Neil; Panasenco, Olga
2018tess.conf40341V Altcode:
The Solar Activity Far Side Investigation, or SAFARI, is a small mission
concept, or an element of a larger mission, devoted to exploring the
origins of solar magnetic activity by carrying out observations of the
velocity and magnetic fields at the solar surface from a vantage point
widely separated from Earth in longitude and latitude. SAFARI images
the Sun from orbits trailing/leading the Earth at 1 AU (SAFARI-S),
with important excursion in latitude, while at the same time the
Sun is imaged from the Earth (SAFARI-E). SAFARI carries out these
observations using a compact Doppler magnetograph based on a simple,
robust design with magneto-optical filters. SAFARI's ground based
component, SAFARI-E, uses a similar observational technique, allowing
precise inter-calibration of magnetograms and providing an opportunity
to implement the novel technique of stereoscopic helioseismology,
probing flows and structural heterogeneities deep in the convection
zone, reaching below the tachocline and opening a new observational
window into the Sun. The combined measurements of solar magnetic fields
from Earth and spacecraft viewpoints extends the longitudinal and
latitudinal coverage of the solar disk allowing extended simultaneous
observations permitting the full study of active region development and
decay that cannot be observed in its entirety from a single point due to
solar rotation. In addition, the structure and depths of sunspots can
be addressed with stereoscopic local helioseismology. Combined scalar
magnetic field measurements from multiple vantage points provide the
vector magnetic field; combined LOS velocity field measurements frm
different vantage points provide the vector velocity field: fundamental
measurements to understand solar activity.
---------------------------------------------------------
Title: Widely distributed SEP events and pseudostreamers
Authors: Panasenco, O.; Panasenco, A.; Velli, M.
2017AGUFMSH33C..07P Altcode:
Our analysis of the pseudostreamer magnetic topology reveals new
interesting implications for understanding SEP acceleration in
CMEs. The possible reasons for the wide distribution of some SEP
events can be the presence of pseudostreamers in the vicinity of the
SEP source region which creates conditions for the existence of strong
longitudinal spread of energetic particles as well as an anomalous
longitudinal solar wind magnetic field component. We reconstructed
the 3D magnetic configurations of pseudostreamers with a potential
field source surface (PFSS) model, which uses as a lower boundary
condition the magnetic field derived from an evolving surface-flux
transport model. In order to estimate the possible magnetic connections
between the spacecraft and the SEP source region, we used the Parker
spiral, ENLIL and PFSS models. We found that in cases of the wide SEP
distributions a specific configuration of magnetic field appears to
exist at low solar latitudes all the way around the sun, we named this
phenomenon a pseudostreamers belt. It appears that the presence of the
well developed pseudostreamer or, rather multiple pseudostreamers,
organized into the pseudostreamer belt can be considered as a very
favorable condition for wide SEP events.
---------------------------------------------------------
Title: The Solar Wind from Pseudostreamers and their Environs:
Opportunities for Observations with Parker Solar Probe and Solar
Orbiter
Authors: Panasenco, O.; Velli, M.; Panasenco, A.; Lionello, R.
2017AGUFMSH23D2703P Altcode:
The solar dynamo and photospheric convection lead to three main types of
structures extending from the solar surface into the corona - active
regions, solar filaments (prominences when observed at the limb) and
coronal holes. These structures exist over a wide range of scales,
and are interlinked with each other in evolution and dynamics. Active
regions can form clusters of magnetic activity and the strongest
overlie sunspots. In the decay of active regions, the boundaries
separating opposite magnetic polarities (neutral lines) develop specific
structures called filament channels above which filaments form. In the
presence of flux imbalance decaying active regions can also give birth
to lower latitude coronal holes. The accumulation of magnetic flux at
coronal hole boundaries also creates conditions for filament formation:
polar crown filaments are permanently present at the boundaries of
the polar coronal holes. Mid-latitude and equatorial coronal holes -
the result of active region evolution - can create pseudostreamers
if other coronal holes of the same polarity are present. While
helmet streamers form between open fields of opposite polarities,
the pseudostreamer, characterized by a smaller coronal imprint,
typically shows a more prominent straight ray or stalk extending
from the corona. The pseudostreamer base at photospheric heights
is multipolar; often one observes tripolar magnetic configurations
with two neutral lines - where filaments can form - separating the
coronal holes. Here we discuss the specific role of filament channels
on pseudostreamer topology and on solar wind properties. 1D numerical
analysis of pseudostreamers shows that the properties of the solar wind
from around PSs depend on the presence/absence of filament channels,
number of channels and chirality at thepseudostreamer base low in the
corona. We review and model possible coronal magnetic configurations
and solar wind plasma properties at different distances from the solar
surface that may be observed by Parker Solar Probe and Solar Orbiter.
---------------------------------------------------------
Title: 2010 August 1-2 Sympathetic Eruptions. II. Magnetic Topology
of the MHD Background Field
Authors: Titov, Viacheslav S.; Mikić, Zoran; Török, Tibor; Linker,
Jon A.; Panasenco, Olga
2017ApJ...845..141T Altcode: 2017arXiv170707773T
Using a potential field source-surface (PFSS) model, we recently
analyzed the global topology of the background coronal magnetic field
for a sequence of coronal mass ejections (CMEs) that occurred on
2010 August 1-2. Here we repeat this analysis for the background field
reproduced by a magnetohydrodynamic (MHD) model that incorporates plasma
thermodynamics. As for the PFSS model, we find that all three CME source
regions contain a coronal hole (CH) that is separated from neighboring
CHs by topologically very similar pseudo-streamer structures. However,
the two models yield very different results for the size, shape,
and flux of the CHs. We find that the helmet-streamer cusp line,
which corresponds to a source-surface null line in the PFSS model,
is structurally unstable and does not form in the MHD model. Our
analysis indicates that, generally, in MHD configurations, this line
instead consists of a multiple-null separator passing along the edge
of disconnected-flux regions. Some of these regions are transient
and may be the origin of the so-called streamer blobs. We show that
the core topological structure of such blobs is a three-dimensional
“plasmoid” consisting of two conjoined flux ropes of opposite
handedness, which connect at a spiral null point of the magnetic
field. Our analysis reveals that such plasmoids also appear in
pseudo-streamers on much smaller scales. These new insights into the
coronal magnetic topology provide some intriguing implications for solar
energetic particle events and for the properties of the slow solar wind.
---------------------------------------------------------
Title: Predicting the Orientation of the B<SUB>z</SUB> Component
of CMEs
Authors: Panasenco, O.; Velli, M.
2016AGUFMSH14A..02P Altcode:
We present a step-by-step procedure to forecast the magnetic field
vector B and more specifically the Bz component associated with the
passage of the Coronal Mass Ejections (CMEs) at 1 AU via observational
and modeling efforts. This is a fundamental component in determining
the geo-effectiveness of Interplanetary (I)CMEs. We discuss a detailed
observational and modeling investigation of pre-eruptive filament
channels and filaments (prominences at the limb), the source regions of
CMEs on the sun, to determine the direction of the tangential component
of the magnetic field in the source region before CMEs (chirality), its
evolution during CME deflection and rotation when filaments erupt. We
analyze the local and global magnetic background near the CME source
region to predict the possible changes in the CME orientation during
the essential early stages of the eruption when magnetic pressure and
tension of the surrounding field are still significant compared to that
in the CME. The question we will answer: What is the direction of the
magnetic field vector B in a pre-eruptive system, with emphasis on the
axial field, and how does it evolve in the early stages of eruption
in the low corona?
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Title: Filament Structure and Stability in the Solar Corona
Authors: Tomlinson, S. M.; Velli, M. C. M.; Panasenco, O.
2016AGUFMSH51B2597T Altcode:
We summarize and critically evaluate the basic theories for solar
filaments and prominences presented up to date, as well as their
stability. In particular we will discuss the role of the various current
systems that may be present in determining equilibrium and stability
properties, including those responsible for the torus instability and
loss of equilibrium. We will then attempt to introduce some additional
elements, such as the possible role of the longitudinal magnetic field
evolution in the stability of prominences, as well as the consequences
of their intrinsically dynamic nature.
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Title: Solar Wind Origins, Heating and Turbulence Evolution with
Solar Probe Plus: The First Three Perihelia
Authors: Velli, M. C. M.; Panasenco, O.; Rappazzo, A. F.; Tenerani,
A.; Bale, S. D.; Fox, N. J.; Howard, R.; Kasper, J. C.; McComas, D. J.
2016AGUFMSH54A..07V Altcode:
In this presentation we will focus on some of the early science return
made possible by the Solar Probe Plus mission, and more specifically
the returns from the first three perihelia at 35.66 solar radii (Rs),
just over half the distance from the Sun of the previous closest
approaching spacecraft, Helios (62.4 Rs). The increased exploration of
the inner heliosphere will allow important new measurements on slow and
fast solar wind turbulent fluctuations, their spectra, and therefore
the origin and dynamics of the so-called Alfvénic turbulence, with
fundamental implications on both the acceleration and heating of the
wind. Will the Alfvénic turbulence cause further bursty jetting in
fast wind streams? How will the anisotropy of the particle distribution
functions eveolve and how will this impact our understanding of the
role plasma instabilities in the wind? During these first encounters,
the Solar Probe Plus spacecraft will already achieve sufficient speeds
to cross the corotation orbit at perihelion: we will therefore also
focus on the questions of the different origins of the slow and fast
solar wind, and specifically the role of the heliospheric current sheet,
the s-web, and coronal streamers and pseudo-streamers in influencing
the different plasma velocities, temperatures and fluctuation properties
in the solar wind inside 40 Rs.
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Title: Morphology of Pseudostreamers and Solar Wind Properties
Authors: Panasenco, Olga; Velli, Marco
2016SPD....47.0324P Altcode:
The solar dynamo and photospheric convection lead to three main types of
structures extending from the solar surface into the corona - active
regions, solar filaments (prominences when observed at the limb) and
coronal holes. These structures exist over a wide range of scales,
and are interlinked with each other in evolution and dynamics. Active
regions can form clusters of magnetic activity and the strongest
overlie sunspots. In the decay of active regions, the boundaries
separating opposite magnetic polarities (neutral lines) develop the
specific structures called filament channels above which filaments
form. In the presence of flux imbalance decaying active regions can
also give birth to lower latitude coronal holes. The accumulation of
magnetic flux at coronal hole boundaries also creates the conditions
for filament formation: polar crown filaments are permanently present
at the boundaries of the polar coronal holes. Middle-latitude and
equatorial coronal holes - the result of active region evolution
- can create pseudostreamers (PSs) if other coronal holes of the
same polarity are present. While helmet streamers form between open
fields of opposite polarities, the pseudostreamer, characterized by
a smaller coronal imprint, typically shows a more prominent straight
ray or stalk extending from the corona. The pseudostreamer base
at photospheric heights is multipolar; often one observes tripolar
magnetic configurations with two neutral lines - where filaments can
form - separating the coronal holes. Here we discuss the specific role
of filament channels on pseudostreamer topology and on solar wind
properties. 1D numerical analysis of PSs shows that the properties
of the solar wind from around PSs depend on the presence/absence of
filament channels, number of channels and chirality at the PS base
low in the corona.
---------------------------------------------------------
Title: Formation and Evolution of Large-Scale Magnetic Funnels in
the Solar Corona
Authors: Panasenco, Olga; Velli, Marco
2016SPD....4740204P Altcode:
The existence of open coronal magnetic fields with peculiar geometry -
large-scale magnetic funnels - can be attributed to three factors:
(i) the presence of two or more corona holes of the same polarity
(or pseudostreamers - PSs), (ii) specific configurations of closed
magnetic field in the low corona up to 1.3 Rs (filament channels) and
(iii) the presence of strong active regions in the vicinity of the
pseudostreamer. The important property of magnetic funnels is their
strongly non-monotonic expansion factor below 2 Rs. The case study
presented here is a pseudostreamer near the equator, formed between
two isolated coronal holes of the same polarity, and harboring a
pair of twin filaments in its base. Following the evolution of these
coronal holes we find that the PS topology changes when two coronal
holes merged together. Using a potential field source-surface (PFSS)
extrapolation to compute the coronal field from photospheric maps
(SDO/HMI), we show that the funnel-like geometry of the open magnetic
field changes to a regular one with monotonic expansion factor after
the merging of coronal holes. The presence of coronal magnetic funnels
becomes directly visible when sufficient plasma accumulates inside
them: when the plasma density grows to become observable coronal cloud
prominences appear in the corona. The plasma suspension at heights
of 0.3 Rs coincides with the largest gradients in the field which
naturally leads to a diamagnetic hypothesis for the force counteracting
gravity. We study the evolution of the funnel-like open fields during
several solar rotations and find a direct relation between funnels
and the presence of coronal clouds at great heights in the solar corona.
---------------------------------------------------------
Title: Filament Channels: Isolated Laboratories of Plasma Heating
in the Solar Corona
Authors: Panasenco, O.; Velli, M.
2015AGUFMSH13C2454P Altcode:
Solar filament channels are complex systems comprising photospheric,
chromospheric and coronal components. These components include
magnetic neutral lines, supergranule cells, fibrils (spicules),
filaments (prominences when observed on the limb), coronal cells,
filament cavities and their overlying coronal arcades. Filaments are
very highly structured and extend in height from the photosphere to
the corona. Filament cores have chromospheric temperatures - 10,000 K
(even at coronal heights ~ 100 Mm), surrounded by hotter plasma with
temperature up to ~50,000 K. The whole filament is isolated from
the rest of the solar corona by an envelope - the filament channel
cavity - with temperatures of about 2,000,000 K. The filament channel
cavity is even hotter than the solar corona outside the filament
channel arcade. The compactness and big temperature variations make
filament channels unique ready-to-go laboratories of coronal plasma
heating and thermodynamics. In this work we discuss possible sources
and mechanisms of heating in the filament channel environment. In
particular, we address the mechanisms of magnetic canceling and current
sheet dissipation.
---------------------------------------------------------
Title: Observations and Analysis of the Non-Radial Propagation of
Coronal Mass Ejections Near the Sun
Authors: Liewer, Paulett; Panasenco, Olga; Vourlidas, Angelos;
Colaninno, Robin
2015SoPh..290.3343L Altcode: 2015SoPh..tmp..177L
The trajectories of coronal mass ejection (CME) are often observed
to deviate from radial propagation from the source while within the
coronagraph field of view (R<15 -30 Rsu<SUB>n</SUB>). To better
understand nonradial propagation within the corona, we first analyze the
trajectories of five CMEs for which both the source and 3D trajectory
(latitude, longitude, and velocity) can be well determined from solar
imaging observations, primarily using observations from the twin
Solar TErrestrial RElations Observatory (STEREO) spacecraft. Next we
analyze the cause of any nonradial propagation using a potential field
source surface (PFSS) model to determine the direction of the magnetic
pressure forces exerted on the CME at various heights in the corona. In
two cases, we find that the CME deviation from radial propagation
primarily occurs before it reaches the coronagraph field of view
(below 1.5 solar radii). Based on the observations and the magnetic
pressure forces calculated from the PFSS model, we conclude that for
these cases the deviation is the result of strong active-region fields
causing an initial asymmetric expansion of the CME that gives rise
to the apparent rapid deflection and nonradial propagation from the
source. Within the limitations of the PFSS model, the magnetic fields
for all five cases appear to guide the CMEs out of the corona through
the weak-field region around the heliospheric current sheet even when
the current sheet is inclined and warped.
---------------------------------------------------------
Title: Observations and Analysis of the Non-Radial Propagation of
Coronal Mass Ejections Near the Sun
Authors: Liewer, Paulett C.; Colaninno, Robin; Panasenco, Olga;
Vourlidas, Angelos
2015TESS....111405L Altcode:
Coronal Mass Ejection (CME) trajectories are often observed to deviate
from radial propagation from the source while within the coronagraph
fields-of-view (R < 15-30 R<SUB>sun</SUB>). To better understand
non-radial propagation within the corona, we analyze the trajectories
of five CMEs for which both the source and 3-D trajectory can be
well determined from solar imaging observations, primarily using
observations from the twin Solar TErrestrial RElations Observatory
(STEREO) spacecraft. A potential field source surface model is used
to determine the direction of the magnetic pressure force exerted
on the CMEs at various heights in the corona. One case shows the
familiar gradual deflection of a polar crown filament CME towards
the heliospheric current sheet and streamer belt by the large-scale
coronal magnetic fields. In two cases, we find that strong active
region fields cause an initial asymmetric expansion of the CME that
gives rise to apparent rapid deflection and non-radial propagation from
the source. For all five cases, within the limitations of the potential
field source surface model, the coronal magnetic fields appear to guide
the CMEs out through the weak field region around the heliospheric
current sheet even when the current sheet is highly inclined and warped.
---------------------------------------------------------
Title: Magnetic Topology of the Global MHD Configuration on 2010
August 1-2
Authors: Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J.; Panasenco, O.
2014AGUFMSH23A4148T Altcode:
It appears that the global magnetic topology of the solar corona
predetermines to a large extent the magnetic flux transfer during
solar eruptions. We have recently analyzed the global topology for
a source-surface model of the background magnetic field at the time
of the 2010 August 1-2 sympathetic CMEs (Titov et al. 2012). Now we
extend this analysis to a more accurate thermodynamic MHD model of
the solar corona. As for the source-surface model, we find a similar
triplet of pseudo-streamers in the source regions of the eruptions. The
new study confirms that all these pseudo-streamers contain separatrix
curtains that fan out from a basic magnetic null point, individual
for each of the pseudo-streamers. In combination with the associated
separatrix domes, these separatrix curtains fully isolate adjacent
coronal holes of the like polarity from each other. However, the size
and shape of the coronal holes, as well as their open magnetic fluxes
and the fluxes in the lobes of the separatrix domes, are very different
for the two models. The definition of the open separator field lines,
where the (interchange) reconnection between open and closed magnetic
flux takes place, is also modified, since the structurally unstable
source-surface null lines do not exist anymore in the MHD model. In
spite of all these differences, we reassert our earlier hypothesis
that magnetic reconnection at these nulls and the associated separators
likely plays a key role in coupling the successive eruptions observed
by SDO and STEREO. The results obtained provide further validation of
our recent simplified MHD model of sympathetic eruptions (Török et
al. 2011). Research supported by NASA's Heliophysics Theory and LWS
Programs, and NSF/SHINE and NSF/FESD.
---------------------------------------------------------
Title: Sympathetic solar eruptions in quadrupolar magnetic
configurations
Authors: Torok, T.; Titov, V. S.; Panasenco, O.
2014AGUFMSH23A4146T Altcode:
Observations by SDO/AIA have renewed the interest in sympathetic
solareruptions, i.e., of eruptions that occur simultaneously (or in
shortsuccession) at different source regions in the corona. Recently,
Toroket al. (2011) developed an idealized numerical model for
the triggermechanisms of sympathetic eruptions in so-called
pseudo-streamers, whichconsist of a tri-polar magnetic configuration
with a parasitic polarityin their center. Here we extend the work
by Torok et al. by investigating sympathetic eruptions in (the
topologically somewhat more complex) quadrupolar configurations,
using MHD simulations. We consider both symmetric and asymmetric
initial configurations that contain two or three flux ropes within the
quadrupole. We find, differentto Torok et al. (2011), that magnetic
reconnection induced by a firsteruption cannot just trigger, but also
prevent subsequent eruptions. In addition, a (relatively modest)
asymmetry of the configuration may fully suppress the occurrence
of successive full eruptions, i.e., of coronal mass ejections. We
discuss the implications of these results for our understanding of
sympathetic eruptions.
---------------------------------------------------------
Title: 3D Location of Small Solar Wind Tracers
Authors: Lopez-Portela, C.; Blanco-Cano, X.; Panasenco, O.; Gibson,
S. E.
2014AGUFMSH21B4126L Altcode:
The so-called "blobs" as defined in Sheeley et al., 1997, are
small-scale structures embedded in the continuously expanding
white-light solar corona and are considered to be tracers of the
slow solar wind. As blobs are very faint structures, we considered
long periods (around 2 to 5 days) where there were no coronal mass
ejections (CME). The scarce presence of CMEs during the extended past
solar minimum has permitted the identification of continuous blobs
detachments, allowing us to estimate their un-projected trajectories
between 2 and 15 solar radii (Mierla et al., 2008). In agreement with
the idea that blobs are liberated from the cusps of helmet steamers
(Wang et al., 1998), we constrained the observing region of interest
in the coronagraphs field of view to ±30° from the Sun's equator. We
studied cases where blobs were detected by the coronagraphs C2/LASCO
and COR2/SECCHI, and inferred their source locations using two
packages that implement the 3D potential field source surface (PFSS)
model: (1) PFSS developed by De Rosa (2010) and (2) PFSS (De Rosa)
in FORWARD (people.hao.ucar.edu/sgibson/FORWARD/). The locations of
the origin of blobs that we find, support previous results that track
down the origin of the slow solar wind to regions near the helmet
streamers and pseudostreamers (Wang et al., 2012, Riley&Luhmann,
2012). Additionally, we found that in some cases blobs are coming
from the boundaries of growing or decaying equatorial coronal holes,
where the interchange reconnection issupposed to be faster.
---------------------------------------------------------
Title: Pseudostreamers: Formation, Magnetic Topology and Plasma
Properties
Authors: Panasenco, O.; Velli, M. M. C.
2014AGUFMSH33A4121P Altcode:
A traditional view of the origins of the solar wind states that slow
wind streams arise from coronal hole boundaries due to the larger
expansion factor. It is hard in this explanation to understand why the
slow wind occupies so much space in the heliosphere. Pseudostreamers
are multipolar features which develop into fields that are unipolar
at greater heights. There is debate as to the speed and nature of the
wind from pseudostreamers: it could be fast, slow, or in between. And,
in general, they might form a network of slow wind which may or may
not connect in the heliosphere to slow wind coming from around the
heliospheric current sheet. Here we discuss the relationship between
the expansion factor along PFSS extrapolated magnetic field lines of
pseudostreamers and wind speed and plasma properties calculated with
numeral modeling. We demonstrate how the resulting wind type depends on
the stage of pseudostreamer development in the context of the global
coronal environment: factors in determining wind speed include the
height of the pseudostreamer null point, the presence or absence of
filament channels, and the expansion of coronal magnetic field lines
in the neighborhood of the pseudostreamer spine. This study helps
to better understand the sources of slow and fast solar wind for the
Solar Probe Plus mission.
---------------------------------------------------------
Title: Apparent Solar Tornado-Like Prominences
Authors: Panasenco, Olga; Martin, Sara F.; Velli, Marco
2014SoPh..289..603P Altcode: 2013arXiv1307.2303P
Recent high-resolution observations from the Solar Dynamics Observatory
(SDO) have reawakened interest in the old and fascinating phenomenon
of solar tornado-like prominences. This class of prominences was
first introduced by Pettit (Astrophys. J.76, 9, 1932), who studied
them over many years. Observations of tornado prominences similar to
the ones seen by SDO had already been documented by Secchi (Le Soleil,
1877). High-resolution and high-cadence multiwavelength data obtained
by SDO reveal that the tornado-like appearance of these prominences is
mainly an illusion due to projection effects. We discuss two different
cases where prominences on the limb might appear to have a tornado-like
behavior. One case of apparent vortical motions in prominence spines
and barbs arises from the (mostly) 2D counterstreaming plasma motion
along the prominence spine and barbs together with oscillations along
individual threads. The other case of apparent rotational motion is
observed in a prominence cavity and results from the 3D plasma motion
along the writhed magnetic fields inside and along the prominence cavity
as seen projected on the limb. Thus, the "tornado" impression results
either from counterstreaming and oscillations or from the projection
on the plane of the sky of plasma motion along magnetic-field lines,
rather than from a true vortical motion around an (apparent) vertical or
horizontal axis. We discuss the link between tornado-like prominences,
filament barbs, and photospheric vortices at their base.
---------------------------------------------------------
Title: Origins of Rolling, Twisting, and Non-radial Propagation of
Eruptive Solar Events
Authors: Panasenco, Olga; Martin, Sara F.; Velli, Marco; Vourlidas,
Angelos
2013SoPh..287..391P Altcode: 2012arXiv1211.1376P; 2012SoPh..tmp..321P
We demonstrate that major asymmetries in erupting filaments and CMEs,
namely major twists and non-radial motions are typically related to
the larger-scale ambient environment around eruptive events. Our
analysis of prominence eruptions observed by the STEREO, SDO, and
SOHO spacecraft shows that prominence spines retain, during the
initial phases, the thin ribbon-like topology they had prior to
the eruption. This topology allows bending, rolling, and twisting
during the early phase of the eruption, but not before. The combined
ascent and initial bending of the filament ribbon is non-radial
in the same general direction as for the enveloping CME. However,
the non-radial motion of the filament is greater than that of the
CME. In considering the global magnetic environment around CMEs,
as approximated by the Potential Field Source Surface (PFSS) model,
we find that the non-radial propagation of both erupting filaments and
associated CMEs is correlated with the presence of nearby coronal holes,
which deflect the erupting plasma and embedded fields. In addition,
CME and filament motions, respectively, are guided towards weaker
field regions, namely null points existing at different heights in
the overlying configuration. Due to the presence of the coronal hole,
the large-scale forces acting on the CME may be asymmetric. We find
that the CME propagates usually non-radially in the direction of least
resistance, which is always away from the coronal hole. We demonstrate
these results using both low- and high-latitude examples.
---------------------------------------------------------
Title: Using Coronal Cells to Infer the Magnetic Field Structure
and Chirality of Filament Channels
Authors: Sheeley, N. R., Jr.; Martin, S. F.; Panasenco, O.; Warren,
H. P.
2013ApJ...772...88S Altcode: 2013arXiv1306.2273S
Coronal cells are visible at temperatures of ~1.2 MK in Fe XII
coronal images obtained from the Solar Dynamics Observatory and Solar
Terrestrial Relations Observatory spacecraft. We show that near a
filament channel, the plumelike tails of these cells bend horizontally
in opposite directions on the two sides of the channel like fibrils
in the chromosphere. Because the cells are rooted in magnetic flux
concentrations of majority polarity, these observations can be used
with photospheric magnetograms to infer the direction of the horizontal
field in filament channels and the chirality of the associated magnetic
field. This method is similar to the procedure for inferring the
direction of the magnetic field and the chirality of the fibril pattern
in filament channels from Hα observations. However, the coronal cell
observations are easier to use and provide clear inferences of the
horizontal field direction for heights up to ~50 Mm into the corona.
---------------------------------------------------------
Title: Analysis of the Deflection of CMEs by Coronal Magnetic Fields
Authors: Liewer, Paulett C.; Panasenco, O.; Vourlidas, A.
2013SPD....4410103L Altcode:
Understanding coronal influences on the direction of propagation
of CMEs is important for space weather prediction. It is well known
that CMEs often propagate non-radially, e.g., they do not move out
radially from the location of the solar source (see, e.g., Cremades
and Bothmer, A&A, 2004; Panasenco et al., Sol. Phys. 2013). There
is evidence that most CMEs exit the corona in the minimum field
region surrounding the coronal/heliospheric current sheet (HCS). If
this is the case, then the degree of deflection should reflect the
distance of the source region from the current sheet region. Here
we study the observed deflection in latitude of four CMEs using
STEREO/SECCHI’s EUV and white light observations to trace the
deflection. A potential-field source surface (PFSS) model (Schrijver
& DeRosa, Sol. Phys. 2003) is used to give information on the
magnetic forces acting on the CME at different heights in the lower
corona. This model, as well as the PFSS model results at the GONG
website (http://gong.nso.edu/data/magmap/archive.html) and the
coronal observations from STEREO, are used to try to determine the
location of the HCS. For the events studied, we find cases when the
deflection is gradual (occurring between the surface at several solar
radii) and cases where the deflection is immediate (within ~1.5 solar
radii). There are many cases in the literature where CMEs originating
at high latitude are deflected towards the ecliptic and eventually
impact Earth. Several of the CMEs we analyzed were later detected in
situ at ~1 AU and we compare the near-Sun trajectory information to
the trajectory information determine from the in situ information.
---------------------------------------------------------
Title: Coronal pseudostreamers: Source of fast or slow solar wind?
Authors: Panasenco, Olga; Velli, Marco
2013AIPC.1539...50P Altcode: 2012arXiv1211.6171P
We discuss observations of pseudostreamers and their 3D magnetic
configuration as reconstructed with potential field source surface
(PFSS)models to study their contribution to the solar wind. To
understand the outflow from pseudostreamers the 3D expansion factor must
be correctly estimated. Pseudostreamers may contain filament channels
at their base in which case the open field lines diverge more strongly
and the corresponding greater expansion factors lead to slower wind
outflow, compared with pseudostreamers in which filament channels
are absent. In the neighborhood of pseudostreamers the expansion
factor does not increase monotonically with distance from the sun,
and doesn't simply depend on the height of the pseudostreamer null
point but on the entire magnetic field configuration.
---------------------------------------------------------
Title: Pseudo-Streamer Structures in the 2010 August 1-2 CMEs:
PFSS verses MHD model.
Authors: Titov, Viacheslav S.; Mikić, Zoran; Török, Tibor; Linker,
Jon A.; Panasenco, Olga
2013shin.confE.130T Altcode:
We upgrade our previous potential field source-surface (PFSS) model of
the background magnetic field in the 2010 August 1-2 sympathetic CMEs
to a more accurate thermodynamic MHD model of the solar corona. For
this new model, we verify our earlier results on the structure of the
large-scale magnetic field, making a similar topological analysis of the
field as before. We identify the similarities and differences between
the two configurations, particularly, for the eruptive regions with
three pseudo-streamers that we have found before. The new study confirms
that all these pseudo-streamers indeed contain vertical separatrix
surfaces located between two adjacent disconnected coronal holes. Of
special interest to us are the magnetic null points and separator
field lines belonging to such separatrix surfaces. These topological
features exist in both PFSS and MHD models, albeit in different
forms. We reassert our earlier hypothesis that magnetic reconnection
at these nulls and separators likely plays a key role in establishing
a physical connection between the successive eruptions observed by
SDO and STEREO. The results obtained provide further validation of
our recent simplified MHD model of sympathetic eruptions (Török et
al. 2011). <P />Work supported by Lockheed Martin, NASA's Heliophysics
Theory and SR&T programs, and SHINE NSF Grant AGS-1156119.
---------------------------------------------------------
Title: Formation of the Coronal Cloud Prominences Inside Magnetic
Funnels
Authors: Panasenco, Olga; Velli, Marco; Martin, Sara F.
2013enss.confE..94P Altcode:
We describe observations of coronal cloud prominences with the Solar
Dynamics Observatory and STEREO. Observations of this phenomenon
during the month of September 2012, in similar locations but over
widely separated periods, are used to investigate the reasons for
the appearance of coronal cloud prominces at different times in the
same location. In particular, we focus on the large scale structure of
the background magnetic field. Using a potential field source-surface
extrapolation to compute the coronal field from photospheric maps, we
find that coronal cloud prominences always form after filament eruptions
and CMEs have occurred nearby. The location of the cloud prominence
coincides with a magnetic field region which appears to be open but
rapidly expanding, an open field with a funnel structure. Part of the
plasma from the neighboring eruption falling back towards the sun is
captured and accumulates in these field regions of strong expansion
of the field. The plasma suspension at heights of 0.3 Rs, coinciding
with the largest gradients in the field naturally lead to a diamagnetic
hypothesis for the force counteracting gravity. We study the evolution
of the funnel-like open fields during several solar rotations and find
a direct relation between funnels and the presence of coronal clouds
at great heights in the solar corona.
---------------------------------------------------------
Title: Solar Tornado Prominences: Plasma Motions Along Filament Barbs
Authors: Panasenco, Olga; Velli, Marco; Martin, Sara F.; Rappazzo,
Franco
2013enss.confE..93P Altcode:
Recent high-resolution observations from the Solar Dynamic Observatory
(SDO) have reawakened interest in the old and fascinating phenomenon
of solar tornado prominences. This class of prominences was first
introduced by E. Pettit in 1932, who studied them over many years
up to 1950. High resolution and high cadence multi-wavelength data
obtained by SDO reveal that the tornado-like properties of these
prominences are mainly an illusion due to projection effects. We
show that counterstreaming plasma motions with projected velocities
up to +/- 45 km/sec along the prominence spine and barbs create a
tornado-like impression when viewed at the limb. We demonstrate that
barbs are often rooted at the intersection between 4-5 supergranular
cells. We discuss the observed oscillations along the vertical parts
of barbs and whether they may be related to vortex flows coming
from the convection downdrafts at the intersection of supergranules
(and possibly smaller convective cells) in the photosphere and their
entrained magnetic field. The unwinding of magnetic threads near the
photosphere via reconnection might be a source of the waves which are
observed as oscillations in prominence barbs.
---------------------------------------------------------
Title: Stereoscopic Analysis of the 31 August 2007 Prominence Eruption
and Coronal Mass Ejection
Authors: Liewer, P. C.; Panasenco, O.; Hall, J. R.
2013SoPh..282..201L Altcode: 2012SoPh..tmp..278L
The spectacular prominence eruption and CME of 31 August 2007 are
analyzed stereoscopically using data from NASA's twin Solar Terrestrial
Relations Observatory (STEREO) spacecraft. The technique of tie pointing
and triangulation (T&T) is used to reconstruct the prominence (or
filament when seen on the disk) before and during the eruption. For
the first time, a filament barb is reconstructed in three-dimensions,
confirming that the barb connects the filament spine to the solar
surface. The chirality of the filament system is determined from
the barb and magnetogram and confirmed by the skew of the loops of
the post-eruptive arcade relative to the polarity reversal boundary
below. The T&T analysis shows that the filament rotates as it
erupts in the direction expected for a filament system of the given
chirality. While the prominence begins to rotate in the slow-rise phase,
most of the rotation occurs during the fast-rise phase, after formation
of the CME begins. The stereoscopic analysis also allows us to analyze
the spatial relationships among various features of the eruption
including the pre-eruptive filament, the flare ribbons, the erupting
prominence, and the cavity of the coronal mass ejection (CME). We find
that erupting prominence strands and the CME have different (non-radial)
trajectories; we relate the trajectories to the structure of the coronal
magnetic fields. The possible cause of the eruption is also discussed.
---------------------------------------------------------
Title: Pseudo-Streamer Magnetic Topologies in the 2010 August 1-2 CMEs
Authors: Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J. A.;
Panasenco, O.
2012AGUFMSH51A2211T Altcode:
We upgrade our previous source-surface model of the background magnetic
field in the 2010 August 1-2 sympathetic CMEs to a more accurate
thermodynamic MHD model of the solar corona. For this new model,
we verify our earlier results on the structure of the large-scale
magnetic field, making a similar topological analysis of the field
as before. We identify the similarities and differences between the
two configurations, particularly, for the eruptive regions with three
pseudo-streamers that we have found before. The new study confirms
that all these pseudo-streamers indeed contain vertical separatrix
surfaces located between two adjacent disconnected coronal holes. Of
special interest to us are the magnetic null points and separator field
lines belonging to such separatrix surfaces. We reassert our earlier
hypothesis that magnetic reconnection at these nulls and separators
likely plays a key role in establishing a physical connection between
the successive eruptions observed by SDO and STEREO. The results
obtained provide further validation of our recent simplified MHD
model of sympathetic eruptions (Török et al. 2011). Work supported
by NASA's Heliophysics Theory and SR&T programs, and SHINE NSF
Grant AGS-1156119.
---------------------------------------------------------
Title: The Build-Up to Eruptive Solar Events Viewed as the Development
of Chiral Systems
Authors: Martin, S. F.; Panasenco, O.; Berger, M. A.; Engvold, O.;
Lin, Y.; Pevtsov, A. A.; Srivastava, N.
2012ASPC..463..157M Altcode: 2012arXiv1212.3646M
When we examine the chirality or observed handedness of the
chromospheric and coronal structures involved in the long-term build-up
to eruptive events, we find that they evolve in very specific ways to
form two and only two sets of large-scale chiral systems. Each system
contains spatially separated components with both signs of chirality,
the upper portion having negative (positive) chirality and the lower
part possessing positive (negative) chirality. The components within
a system are a filament channel (represented partially by sets of
chromospheric fibrils), a filament (if present), a filament cavity,
sometimes a sigmoid, and always an overlying arcade of coronal
loops. When we view these components as parts of large-scale chiral
systems, we more clearly see that it is not the individual components
of chiral systems that erupt but rather it is the approximate upper
parts of an entire evolving chiral system that erupts. We illustrate the
typical pattern of build-up to eruptive solar events first without and
then including the chirality in each stage of the build-up. We argue
that a complete chiral system has one sign of handedness above the
filament spine and the opposite handedness in the barbs and filament
channel below the filament spine. If the spine has handedness, the
observations favor its having the handedness of the filament cavity and
coronal loops above. As the separate components of a chiral system form,
we show that the system appears to maintain a balance of right-handed
and left-handed features, thus preserving an initial near-zero net
helicity. We further argue that the chiral systems allow us to identify
key sites of energy transformation and stored energy later dissipated in
the form of concurrent CMEs, erupting filaments and solar flares. Each
individual chiral system may produce many successive eruptive events
above a single filament channel. Because major eruptive events
apparently do not occur independent of, or outside of, these unique
chiral systems, we hypothesize that the development of chiral systems:
(1) are fundamental to the occurrence of eruptive solar events and (2)
preserve an approximate balance between positive and negative helicity
(right and left-handed chirality) while preparing to release energy
in the form of CMEs, erupting filaments, and flares.
---------------------------------------------------------
Title: The Solar Wind From Pseudostreamers And Their Immediate
Environment
Authors: Panasenco, O.; Velli, M. M.; Panasenco, A.; Lionello, R.
2012AGUFMSH53A2257P Altcode:
Beyond the very large-scale relationship of fast solar wind streams
to coronal holes, the connection between coronal structures and their
solar wind counterparts remains largely mysterious. Here we study the
three-dimensional expansion of the solar wind from open field lines in
the immediate neighborhood of coronal pseudostreamers, including the
pseudostreamer spine. To this effect, we use a PFSS extrapolation of
the photospheric magnetic field out to 2.5 solar radii, and assume the
field expands radially beyond that. Different types of pseudostreamers
exist, with a complex inner structure which depends on the number
of polarities embedded in the closed regions below. In addition
pseudostreamers may also harbor filament channels, often occurring
in pairs (twin filament channels). In the latter case, the strongly
sheared field of the channel magnetic structures and the skew of the
coronal arcade above the channels dictate the way the coronal field
expands in the neighborhood of pseudostreamers. Here we integrate the
time dependent 1D MHD equations along the PFSS extrapolated magnetic
field, in the presence of gravity, and including the effect of an
Alfvén wave pressure term, and determine the dependence of wind
speed on different types of observed pseudostreamers. There is no
simple relationship between pseudostreamers and wind speed, rather the
resulting wind type is a function of the global coronal environment,
including the height of the pseudostreamer null point, the presence
or absence of filament channels, and therefore the expansion of the
coronal magnetic field in the neighborhood of the pseudostreamer spine.
---------------------------------------------------------
Title: The Model Magnetic Configuration of the Extended Corona in
the Solar Wind Formation Region
Authors: Veselovsky, Igor; Panasenco, Olga
2012arXiv1212.5310V Altcode:
The coupling between small and large scale structures and processes
on the Sun and in the heliosphere is important in the relation to the
global magnetic configuration. Thin heliospheric current sheets play
the leading role in this respect. The simple analytical model of the
magnetic field configuration is constructed as a superposition of the
three sources: 1) a point magnetic dipole in the center of the Sun, 2)
a thin ring current sheet with the azimuthal current density j_{\varphi}
~ r^{-3} near the equatorial plane and 3) a magnetic quadrupole in
the center of the Sun. The model reproduces, in an asymptotically
correct manner, the known geometry of the field lines during the
declining phase and solar minimum years near the Sun (the dipole term)
as well as at large distances in the domain of the superalfvenic solar
wind in the heliosphere, where the thin current sheet dominates and
|B_{r}(\theta)|=const according to Ulysses observations (Balogh et
al., 1995; Smith et al., 1995). The model with the axial quadrupole
term is appropriate to describe the North-South asymmetry of the field
lines. The model may be used as a reasonable analytical interpolation
between the both extreme asymptotic domains (inside the region of the
intermediate distances ~ (1-10)R_sun) when considering the problems
of the solar wind dynamics and cosmic ray propagation theories.
---------------------------------------------------------
Title: Magnetic reconnection, shear flow and the axial filament
channel magnetic field
Authors: Velli, M. M.; Rappazzo, F.; Panasenco, O.
2012AGUFMSH33D2251V Altcode:
The same processes leading to coronal heating also structure the global
corona. Among these one of the most fascinating is the formation
of filament channels. Here we discuss the formation and evolution
of the axial magnetic field of filament channels as a result of
the photospheric transport of magnetic field footpoints with flows
converging to the neutral line leading to magnetic reconnection as
well as some shearing of the magnetic field along the neutral line.The
focus here is not on the large-scale 3D simulation of the formation
of prominences or filaments but on the magnetic reconnection process
itself, and its dependence on photospheric motions, stratification,
and shear. Previous numerical simulations and models are used as a
guide to setup numerical simulations and analytical calculations of
tearing and reconnection leading to the enhancement of the coronal
axial magnetic field. We generalize previous work by taking full
account of recent advances in MHD turbulence and reconnection theory
(plasmoid instability, reconnection rates, current sheet thicknesses)
to associate the rate of enhancement of the axial magnetic field with
observed photospheric flows and the consequent matter flows through
the chromosphere up into the corona along the filament.
---------------------------------------------------------
Title: 2010 August 1-2 Sympathetic Eruptions. I. Magnetic Topology
of the Source-surface Background Field
Authors: Titov, V. S.; Mikic, Z.; Török, T.; Linker, J. A.;
Panasenco, O.
2012ApJ...759...70T Altcode: 2012arXiv1209.5797T
A sequence of apparently coupled eruptions was observed on 2010 August
1-2 by Solar Dynamics Observatory and STEREO. The eruptions were closely
synchronized with one another, even though some of them occurred at
widely separated locations. In an attempt to identify a plausible reason
for such synchronization, we study the large-scale structure of the
background magnetic configuration. The coronal field was computed from
the photospheric magnetic field observed at the appropriate time period
by using the potential field source-surface model. We investigate the
resulting field structure by analyzing the so-called squashing factor
calculated at the photospheric and source-surface boundaries, as well as
at different coronal cross-sections. Using this information as a guide,
we determine the underlying structural skeleton of the configuration,
including separatrix and quasi-separatrix surfaces. Our analysis
reveals, in particular, several pseudo-streamers in the regions where
the eruptions occurred. Of special interest to us are the magnetic
null points and separators associated with the pseudo-streamers. We
propose that magnetic reconnection triggered along these separators
by the first eruption likely played a key role in establishing the
assumed link between the sequential eruptions. The present work
substantiates our recent simplified magnetohydrodynamic model of
sympathetic eruptions and provides a guide for further deeper study
of these phenomena. Several important implications of our results for
the S-web model of the slow solar wind are also addressed.
---------------------------------------------------------
Title: Pseudostreamers and Twin Filaments in the Solar Corona
Authors: Panasenco, Olga; Velli, Marco
2012shin.confE.163P Altcode:
Pseudostreamer configurations appear in globally unipolar regions
above multiple polarity reversal boundaries, and are a generic feature
which seems to be important for coronal physics. On small scales
pseudostreamer configurations can support jets, or polar plumes. On
large scales, some of these polarity reversal boundaries can be filament
channels, and when this is the case they always occur as twin filament
channels often containing twin filaments of the same chirality. The
magnetic structure of pseudostreamers for cases with and without twin
filaments lying at their base, as reconstructed with a PFSS model,
is significantly different. Branches of pseudostreamers on opposite
sides of the separatrix surface diverge when filaments are present,
in association with the strong horizontal component of the field
present in filament channels. Here we analyze possible magnetic field
configurations of the complete pseudostreamer system and study the
links between its separate parts, which include open field lines of
pseudostreamers, filament channels, filaments, cavities, overlying
filament arcades. Following the dynamical changes in the coronal
pseudostreamer, we analyze the twin filament eruption due to new
flux emergence and how the topology of the pseudostreamer gradually
changes during the pre-eruptive and erupting phases. The presence
of well developed filaments of the same chirality at the base of
pseudostreamers implies sheared fields, which in the PFSS model are
current-free, but are more generally consistent with the presence of
a vertical pseudostreamer field-aligned current sheet. We discuss the
3D magnetic topology of the filament, filament cavity and overlying
filament arcades for these twin systems and its implications on the
theories for filaments, filament eruptions and CMEs.
---------------------------------------------------------
Title: Magnetic Topology of Pseudo-Streamers in the 2010 August 1-2
Eruption Events
Authors: Titov, Viacheslav S.; Mikic, Zoran; Torok, Tibor; Linker,
Jon A.; Panasenco, Olga
2012shin.confE.160T Altcode:
A sequence of apparently coupled eruptions was observed on 2010 August
1-2 by SDO and STEREO. The eruptions were closely synchronized, even
though some of them occurred very far from each other. Trying to
identify a plausible reason for such synchronization, we study the
large-scale structure of the background magnetic field. The latter
was computed from the photospheric magnetic field observed at the
appropriate time period by using the potential field source-surface
model.For the resulting configuration, we determine its structural
skeleton, which includes all separatrix and quasi-separatrix
surfaces. Analyzing them, we reveal three pseudo-streamers in the
regions where the eruptions occurred. Of special interest to us are
the magnetic null points and separator field lines associated with
these pseudo-streamers. We propose that magnetic reconnection at
such nulls and separators played likely a key role in establishing
the physical link between the successive eruptions. Work supported
by NASA's Heliophysics Theory and SR&T programs, and SHINE NSF
Grant AGS-1156119.
---------------------------------------------------------
Title: Sympathetic Eruptive Events and Pseudostreamers
Authors: Panasenco, Olga; Titov, Viacheslav; Mikić, Zoran; Török,
Tibor; de Toma, Giuliana; Velli, Marco
2012shin.confE.162P Altcode:
Sequences of apparently coupled CMEs triggered by sympathetic eruptions
of solar filaments are usually observed when the initial coronal
magnetic configuration above the source region contains at least
one coronal pseudostreamer. We study in detail an example of such a
sympathetic event observed on 27-28 July 2011 by SDO and STEREO. This
involved five filaments and caused four individual filament eruptions
and one partial eruption. The eruptions were closely synchronized,
even though some occurred at widely separated locations. In an attempt
to identify a plausible reason of such a synchronization, we study the
large-scale structure of the background PFSS magnetic fields, computed
from the observed photospheric magnetic field (SDO/HMI) during the
appropriate time period. We investigate the magnetic connectivities in
these configurations by calculating and analyzing the distributions of
the so-called squashing factor at the photospheric and source-surface
boundaries, as well as other cross-sections at different heights. This
allows us to get a comprehensive understanding of the underlying
structural skeleton of the magnetic configuration. In particular,
our analysis reveals two pseudostreamer magnetic configurations in the
region where the eruptions occurred. Of special interest to us are the
magnetic null points and separators located at the intersection of the
separatrix domes and curtains of the pseudostreamers. We assume that
magnetic reconnection induced by the first eruption at these locations
played likely a major role in establishing the postulated link between
the different eruptions in sequence. The close relationship between the
sympathetic eruptions and pseudostreamer configurations are supported
by a statistical study covering the SDO era (2010-2012).
---------------------------------------------------------
Title: Solar Tornados - Myth or Reality?
Authors: Panasenco, Olga
2012shin.confE.215P Altcode:
Resent high-resolution observations from the Solar Dynamic Observatory
have reawakened interest in an old and fascinating phenomenon of "solar
tornados". This class of prominences was first introduced by E. Pettit
in 1932, who studied them over many years up to 1950. Observations of
solar tornados similar to the ones seen by SDO were already documented
in 1875 by Secchi in his famous "Le Soleil". So, what are solar tornados
- myth or reality? Thanks to SDO high resolution and high cadence
multi-wavelength data, we can now answer this question. We introduce two
types of solar tornados, types I and II. We show that a Type I tornado
is the projection on the solar limb of the mostly 2D counter-streaming
plasma motion along prominence spine and barbs. Type II tornados,
on the other hand, consist in more 3D plasma motion following the
sheared magnetic fields inside and along the prominence cavity, also
projected on the limb. In other words, the "tornado" impression types
results from the projection of plasma motions along magnetic lines,
rather than a general vortical motion around a vertical or radial axis.
---------------------------------------------------------
Title: Pseudostreamers and Twin Filaments in the Solar Corona
Authors: Panasenco, Olga; Velli, M.
2012AAS...22020212P Altcode:
Pseudostreamer configurations appear in globally unipolar regions
above multiple polarity reversal boundaries, and are a generic feature
which seems to be important for coronal physics. On small scales
pseudostreamer configurations can support jets, or polar plumes. On
large scales, some of these polarity reversal boundaries can be filament
channels, and when this is the case they always occur as twin filament
channels often containing twin filaments of the same chirality. The
magnetic structure of pseudostreamers for cases with and without twin
filaments lying at their base, as reconstructed with a PFSS model,
is significantly different. Branches of pseudostreamers on opposite
sides of the separatrix surface diverge when filaments are present,
in association with the strong horizontal component of the field
present in filament channels. Here we analyze possible magnetic field
configurations of the complete pseudostreamer system and study the
links between its separate parts, which include open field lines of
pseudostreamers, filament channels, filaments, cavities, overlying
filament arcades. Following the dynamical changes in the coronal
pseudostreamer, we analyze the twin filament eruption due to new
flux emergence and how the topology of the pseudostreamer gradually
changes during the pre-eruptive and erupting phases. The presence
of well developed filaments of the same chirality at the base of
pseudostreamers implies sheared fields, which in the PFSS model are
current-free, but are more generally consistent with the presence of
a vertical pseudostreamer field-aligned current sheet. We discuss the
3D magnetic topology of the filament, filament cavity and overlying
filament arcades for these twin systems and its implications on the
theories for filaments, filament eruptions and CMEs.
---------------------------------------------------------
Title: Coronal Holes, Filament Channels And Filaments: Observations
Of The Self-organization Of The Coronal Magnetic Field Over Solar
Cycles 23 And 24
Authors: Panasenco, Olga; Martin, S. F.; Velli, M.; Berger, M. A.
2012AAS...22020202P Altcode:
The aim of this work is to understand the relationship between coronal
holes, coronal hole boundaries and one of the other main features
of the coronal magnetic field, namely filament channels, regions
of highly sheared magnetic fields overlying photospheric polarity
reversal boundaries. The well-developed filament channel is a necessary
ingredient for filament formation. Polar coronal holes and polar crown
filament channels always seem to exist together, and even during periods
of weakest activity, when nothing indicates the presence of polar crown
channels on the solar disk, polar crown prominences appear at the limb
proving their existence. Does a similar symbiotic relationship exist
also for other coronal holes? There is some indication that for middle
and low latitude coronal holes different configurations occur depending
on the polarity of the hole relative to the pole. If the polarity is
the same, then a coronal pseudostreamer configuration can form with
twin filament channels at its base, while if the polarity is opposite,
the right conditions for the development of the filament channels
and filaments following the hemispheric helicity rule arise. Using
SOHO/EIT and MDI, STEREO/EUVI, SDO/AIA and HMI instruments we trace the
formation and mutual evolution of coronal holes and their symbiotic
filament channels up to and including filament formations, eruptions
and subsequent reformations during period 1998-2012 (solar cycles 23
and 24).
---------------------------------------------------------
Title: Observations and simulations of the sympathetic eruptions on
2010 August 1
Authors: Torok, T.; Mikic, Z.; Panasenco, O.; Titov, V. S.; Reeves,
K. K.; Velli, M.; Linker, J. A.; de Toma, G.
2012EGUGA..14.3270T Altcode:
During the rise of the new solar cycle, the Sun has produced a number
of so-called sympathetic eruptions, i.e., eruptions that occur close in
time in different source regions. While it has become clear in recent
years that in many of such events the individual eruptions must be
magnetically connected, the exact nature of these connections is not
yet understood. A particularly beautiful case, which consisted of half
a dozen individual eruptions, was observed by STEREO and SDO on 2010
August 1. Here we focus on a subset of two large, consecutive filament
eruptions that were preceded by a nearby CME. We first summarize the
main features of these events and then present 3D MHD simulations
that were designed to model such a chain of eruptions. The simulations
suggest that the two filament eruptions were triggered by two successive
reconnection events, each of which was induced by the previous eruption,
and thus provide a new mechanism for sympathetic eruptions.
---------------------------------------------------------
Title: Coronal Mass Ejections from Magnetic Systems Encompassing
Filament Channels Without Filaments
Authors: Pevtsov, Alexei A.; Panasenco, Olga; Martin, Sara F.
2012SoPh..277..185P Altcode:
Well-developed filament channels may be present in the solar atmosphere
even when there is no trace of filament material inside them. Such
magnetic systems with filament channels without filaments can result
in coronal mass ejections that might appear to have no corresponding
solar surface source regions. In this case study, we analyze CMEs on
9 August 2001 and 3 March 2011 and trace their origins to magnetic
systems with filament channels containing no obvious filament material
on the days around the eruptions.
---------------------------------------------------------
Title: Coronal Holes and Filaments: Life in Symbiosis
Authors: Panasenco, O.; Velli, M.; Martin, S. F.; Berger, M. A.
2011AGUFMSH12A..05P Altcode:
The aim of this work is to understand the relationship between
coronal holes, coronal hole boundaries and one of the other main
features of the coronal magnetic field, namely filament channels,
regions of highly sheared magnetic fields overlying photospheric
polarity reversal boundaries. The well developed filament channel
is a necessary ingredient for the filament formation. Polar coronal
holes and polar crown filament channels always seem to exist together,
and even during periods of weakest activity, when nothing indicates
the presence of polar crown channels on the solar disk, polar crown
prominences appear at the limb proving their existence. Does a similar
symbiotic relationship exist also for other coronal holes? There is
some indication that for middle and low latitude coronal holes different
configurations occur depending on the polarity of the hole relative to
the pole. If the polarity is the same, then a coronal pseudostreamer
configuration can form with twin filament channels at its base, while if
the polarity is opposite, the right conditions for the development of
the filament channels and filaments following the hemispheric helicity
rule arise. Using STEREO/EUVI, SDO/AIA and HMI instruments we trace the
formation and mutual evolution of coronal holes and their symbiotic
filament channels up to and including filament formations, eruptions
and subsequent reformations during many solar rotations in 2010-2011.
---------------------------------------------------------
Title: The Disappearing Solar Filament of 2003 June 11: A Three-body
Problem
Authors: Balasubramaniam, K. S.; Pevtsov, A. A.; Cliver, E. W.;
Martin, S. F.; Panasenco, O.
2011ApJ...743..202B Altcode:
The eruption of a large quiescent filament on 2003 June 11 was preceded
by the birth of a nearby active region—a common scenario. In this
case, however, the filament lay near a pre-existing active region
and the new active region did not destabilize the filament by direct
magnetic connection. Instead it appears to have done so indirectly
via magnetic coupling with the established region. Restructuring
between the perturbed fields of the old region and the filament
then weakened the arcade overlying the midpoint of filament, where
the eruption originated. The inferred rate (~11° day<SUP>-1</SUP>)
at which the magnetic disturbance propagates from the mature region
to destabilize the filament is larger than the mean speed (~5º-6°
day<SUP>-1</SUP>) but still within the scatter obtained for Bruzek's
empirical relationship between the distance from a newly formed
active region to a quiescent filament and the time from active region
appearance to filament disappearance. The higher propagation speed in
the 2003 June 11 case may be due to the "broadside" (versus ”end-on")
angle of attack of the (effective) new flux to the coronal magnetic
fields overlying a central section of the axis of the filament.
---------------------------------------------------------
Title: Magnetic Topology of the Sympathetic CMEs Observed on 27 July
2011 and 1 August 2010
Authors: Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J. A.;
Panasenco, O.
2011AGUFMSH43B1949T Altcode:
Two fascinating sequences of apparently coupled CMEs were observed
on 27-28 July 2011 and 1-2 August 2010 by SDO and STEREO. The latter
sequence has recently been described at length by Schrijver &
Title (2011). In both CME sequences, the individual eruptions were
closely synchronized with one another, even though some of them
occurred at widely separated locations. In an attempt to identify a
plausible reason of such a synchronization, we study the large-scale
structure of the background PFSS magnetic fields that were computed
from the observed photospheric magnetic field at the appropriate
time period. We investigate the magnetic connectivities in these
configurations by calculating and analyzing the distributions of the
so-called squashing factor at the photospheric and source-surface
boundaries, as well as at different cross-sections. This allows us
to get a comprehensive understanding of the underlying structural
skeleton of the magnetic configuration. In particular, our analysis
reveals several pseudo-streamers in the regions where the eruptions
occurred. Of special interest to us are the magnetic null points and
separators located at the intersection of the separatrix domes and
curtains of the pseudo-streamers. We assume that magnetic reconnection
induced by the first eruption at these locations played likely a major
role in establishing the postulated link between the eruptions in both
CME sequences. Our recent simplified MHD model of sympathetic eruptions
supports this assumption (Török et al. 2011). In the present study,
we try to further verify it by comparing the background magnetic
topologies of the two sequences of CMEs. Work supported by NASA and
the Center for Integrated Space Weather Modeling (an NSF Science and
Technology Center).
---------------------------------------------------------
Title: A Model for Magnetically Coupled Sympathetic Eruptions
Authors: Török, T.; Panasenco, O.; Titov, V. S.; Mikić, Z.; Reeves,
K. K.; Velli, M.; Linker, J. A.; De Toma, G.
2011ApJ...739L..63T Altcode: 2011arXiv1108.2069T
Sympathetic eruptions on the Sun have been observed for several decades,
but the mechanisms by which one eruption can trigger another remain
poorly understood. We present a three-dimensional MHD simulation that
suggests two possible magnetic trigger mechanisms for sympathetic
eruptions. We consider a configuration that contains two coronal flux
ropes located within a pseudo-streamer and one rope located next to
it. A sequence of eruptions is initiated by triggering the eruption of
the flux rope next to the streamer. The expansion of the rope leads
to two consecutive reconnection events, each of which triggers the
eruption of a flux rope by removing a sufficient amount of overlying
flux. The simulation qualitatively reproduces important aspects of the
global sympathetic event on 2010 August 1 and provides a scenario for
the so-called twin filament eruptions. The suggested mechanisms are
also applicable for sympathetic eruptions occurring in other magnetic
configurations.
---------------------------------------------------------
Title: Origins of Rolling, Twisting and Non-radial Propagation of
Eruptive Solar Events
Authors: Martin, Sara F.; Panasenco, Olga
2011sdmi.confE.105M Altcode:
We demonstrate that major asymmetries in erupting filaments and CMEs
are not only related to each other but that major twists and non-radial
motions typically are related to the larger, more global environment
around eruptive events. This overarching result grew out of a number of
earlier studies that we now encapsulate within the bigger picture. If
a filament erupts non-radially, as frequently happens, the top of
its spine first bends to one side and evolves into a sideways rolling
motion. As shown by 304 Angstrom observations from SOHO and STEREO and
earlier H alpha Doppler observations, the rolling motion propagates
down the legs of erupting filaments resulting in the large scale
twists commonly observed in them. The initial rolling initiates twist
of opposite chirality in the two legs. In addition to the observed
absence of twist in the pre-eruptive state, further evidence that
the energy creating the twist comes from above was found in Doppler
shifts; the rotational motions in the legs of erupting filaments are
not only opposite in sign to each other but the twists in both legs
are opposite in sign to that required if the observed sense of twist
were generated at the feet or in the legs of the erupting filament. We
next demonstrate that the combined ascent and initial bending is
non-radial in the same general direction as for the surrounding
CME. However, the non-radial motion of the filament is greater than
that of the CME. In considering the global environment around CMEs,
as can be approximated by the Potential Field Source Surface (PFSS)
Model, we found that both erupting filaments and their surrounding
CMEs are non-radial only in the direction away from a nearby coronal
hole and toward local and global null points. Due to the presence of
the coronal hole, the global forces on the CME are asymmetric. The CME
propagates non-radially in the direction of least resistance and that
is always away from the coronal hole as we demonstrate by comparing low
latitude and high latitude examples. Through modeling and comparison
with observed events, we anticipate that major twists and non-radial
motions in erupting prominences and CMEs will become predictable to
the extent that their environments are well-defined and measurable.
---------------------------------------------------------
Title: Demonstration of HelioFlux: an IDL tool applied to calculation
of magnetic flux or intensity of solar features
Authors: Panasenco, Aram; Panasenco, Olga; Martin, Sara
2011shin.confE.171P Altcode:
HelioFlux, a user-friendly IDL based tool developed at Helio Research,
facilitates the measurement of changes in magnetic flux or spectral
brightness over an assigned region on the solar surface, using data
sets from SOHO, STEREO, SDO and ground based observatories. HelioFlux
aids in extracting new science results from enormous data sets such as
those delivered by SDO and future solar missions. <P />As an example
we applied HelioFlux to track the evolution of magnetic flux between
a coronal hole and a filament channel over 8 solar rotations. In this
time multiple filament eruptions occurred from this channel at the
average rate of 2 per solar rotation. In addition, using potential
field source surface extrapolation (PFSS), we calculated time series of
the distribution of the open magnetic field lines in the coronal hole
starting before the birth of the long-lived filament channel up until
after the channel was completely destroyed by the emergence a super
cluster of active regions. We found evidence of the mutual influence
between the coronal hole and filament channel which allow them to
survive together for more than a half year. The data and measurements
are consistent with the view that coronal hole magnetic fields are
generated and organized by hydromagnetic transport processes at/near
the solar surface.
---------------------------------------------------------
Title: A model for sympathetic eruptions
Authors: Torok, Tibor; Panasenco, O.; Titov, V. S.; Mikic, Z.; Velli,
M.; Linker, J.; De Toma, G.
2011shin.confE.125T Altcode:
Apart from single eruptions originating in localized source regions,
the Sun sometimes produces so-called sympathetic events, which consist
of several individual eruptions occurring almost simultaneously
in different source regions. The close temporal correlation of the
individual eruptions in such events indicates a causal link between
them, but the mechanisms by which one eruption can trigger another
one remain largely a mystery. <P />A particularly beautiful example
of a global sympathetic event was recently observed by the Solar
Dynamics Observatory (SDO) on 1 August 2010. It included a small
filament eruption and CME that was shortly after followed by the
nearby subsequent eruptions of two large adjacent (twin) filaments,
indicating that these three eruptions were physically connected. A
coronal potential field extrapolation reveals that the twin filaments
were located in the lobes of a so-called pseudostreamer prior to
their eruptions. <P />Here we present a 3D MHD simulation of the
successive eruption of two magnetic flux ropes in such a pseudostreamer
configuration. The two eruptions are triggered by the simulated eruption
of a third flux rope in the vicinity of the pseudostreamer. The
simulation qualitatively reproduces the CME and subsequent twin
filament eruption on 1 August 2010 and suggests that these events
were indeed physically connected. Furthermore, it provides a generic
scenario for the frequently observed twin filament eruptions in coronal
pseudostreamers and suggests a mechanism by which such eruptions can
be triggered in the first place. Our results thus provide an important
step for a better understanding of sympathetic eruptions.
---------------------------------------------------------
Title: CMEs from emptied filament channels
Authors: Panasenco, Olga; Martin, Sara; Feynman, Joan
2011shin.confE..31P Altcode:
Using SDO, SOHO and STEREO data we analyze several CMEs originating
from emptied filament channels. The CMEs occurred 2 to 4 days after
the original filament plasma appeared to drain away leaving the
channels empty. Observed on the limb, these CMEs appeared to be very
faint and without one of the three well known components - the bright
core. For one case, the CME of May 23, 2010, we traced changes in the
photospheric magnetic flux inside and neighboring the filament channel
from before to after the filament plasma had drained. We found that
the emptying process was associated with relatively fast changes in
the magnetic flux. The magnetic flux changes were due to localized
photospheric cancellation, which we believe caused an increase in
the magnetic flux trapped in the filament cavity, by the same process
that creates filament channels in the first place. Using a PFSS model,
we also traced changes in the magnetic field configuration overlying
the filament channel from May 20 through May 25, 2010. We found that
the connectivity of coronal loops overlying the arcade changed as a
result of the emergence of a new active region, which resulted in a
reduction of flux density in the overlying arcade and the subsequent
complete eruption of the coronal arcade system with the filament cavity
it encompassed. We interpret this sequence of events in terms of a
continuous removal, via reconnection with the fields of the newly
emerging active region, of the field lines in the arcade overlying
the filament channel, which together with the increase of the fields
inside the cavity rapidly lead to the complete destabilization of the
configuration and the birth of the CME. We view this case as a classic
example of the tether-cutting model of CME initiation.
---------------------------------------------------------
Title: Rolling motion in erupting prominences observed by STEREO
Authors: Panasenco, Olga; Martin, Sara; Joshi, Anand D.; Srivastava,
Nandita
2011JASTP..73.1129P Altcode:
We analyze the large-scale dynamical forms of three erupting prominences
(filaments) observed by at least one of the two STEREO spacecraft
and which reveal evidence of sideways rolling motion beginning at
the crest of the erupting filament. We find that all three events
were also highly non-radial and occurred adjacent to large coronal
holes. For each event, the rolling motion and the average non-radial
outward motion of the erupting filament and associated CME were away
from a neighboring coronal hole. The location of each coronal hole
was adjacent to the outer boundary of the arcade of loops overlying
the filaments. The erupting filaments were all more non-radial than
the CMEs but in the same general direction. From these associations,
we make the hypothesis that the degree of the roll effect depends on
the level of force imbalances inside the filament arcade related to
the coronal hole and the relative amount of magnetic flux on each side
of the filament, while the non-radial motion of the CME is related
to global magnetic configuration force imbalances. Our analyses of
the prominence eruption best observed from both STEREO-A and STEREO-B
shows that its spine retained the thin ribbon-like topology that it
had prior to the eruption. This topology allows bending, rolling,
and twisting during the early phase of the eruption.
---------------------------------------------------------
Title: 3d Mhd Simulation Of Sympathetic Eruptions On 1 August 2010
Authors: Torok, Tibor; Panasenco, O.; Titov, V.; Mikic, Z.; Reeves,
K.; Velli, M.; Linker, J.; de Toma, G.
2011SPD....42.0908T Altcode: 2011BAAS..43S.0908T
Apart from single eruptions originating in localized source regions, the
Sun sometimes produces so-called sympathetic events, which consist of
<P />several individual eruptions occurring <P />almost simultaneously
in different source regions. The close temporal vicinity of the
individual eruptions in such events indicates the <P />existence of
a causal link between them, but the mechanisms by which one eruption
can trigger another one remain largely a mystery. A particularly
beautiful example of a global sympathetic event was recently observed
by the Solar Dynamics Observatory (SDO) on 1 August 2010. It included
a small filament eruption and CME that was closely followed by the
eruptions of two large adjacent (twin) filaments, indicating that these
three eruptions were physically connected. A coronal potential field
extrapolation revealed that the twin filaments were located in the
lobes of a so-called pseudostreamer prior to their eruptions. Here we
present a 3D MHD simulation of the successive eruption of two magnetic
flux ropes in such a pseudostreamer configuration. The two eruptions are
triggered by the simulated eruption of a third flux rope in the vicinity
of the pseudostreamer. The simulation qualitatively reproduces the CME
and subsequent twin filament eruption on 1 August 2010 and suggests that
these events were indeed physically connected. Furthermore, it provides
a generic scenario for the frequently observed twin filament eruptions
in coronal pseudostreamers and suggests a mechanism by which such
eruptions can be triggered in the first place. Our results thus provide
an important step for a better understanding of sympathetic eruptions.
---------------------------------------------------------
Title: Magnetic Structure of Twin Filaments Inside Pseudostreamers
Authors: Panasenco, O.; Velli, M. M.
2010AGUFMSH51A1663P Altcode:
Among the large scale coronal structures, pseudostreamers appear in
unipolar regions above multiple polarity reversal boundaries. Some of
these polarity reversal boundaries can be filament channels, and when
this is the case they always occur as twin filament channels often
containing twin filaments. The magnetic structure of pseudostreamers
with and without twin filaments lying at their base is significantly
different. Branches of pseudostreamers on opposite sides of the
separatrix surface diverge when filaments are present. Here we analyze
possible current and magnetic field configurations of the complete
pseudostreamer system and study the links between its separate parts,
which include open field lines of pseudostreamers, filament channels,
filaments, cavities, overlying filament arcades. The presence of well
developed filaments of the same chirality at the base of pseudostreamers
implies the presence of a vertical current sheet, which divides and
repeal branches of the pseudostreamer field lines in 3D. We discuss the
3D magnetic topology of the filament, filament cavity and overlying
filament arcades for these twin systems and its implications on the
theories for filaments an filament eruptions.
---------------------------------------------------------
Title: Stereoscopic Analysis of 31 August 2007 Erupting Prominence
Authors: Liewer, P. C.; Hall, J. R.; de Jong, E. M.; Martin, S. F.;
Panasenco, O.
2010AGUFMSH51A1658L Altcode:
The dramatic prominence eruption of 31 August 2007 and the associated
CME were well observed by both STEREO spacecraft, separated by 28° at
that time. The eruption occurred as the filament reach the West limb
as seen by STEREO B; the filament, the coronal cavity and the CME
were all clearly observed. We use tie-pointing and triangulation to
determine the 3D trajectories of the erupting filament (seen in EUVI
and COR1) and the associated CME and cavity (seen in COR1 and COR2)
and we compare these trajectories. From the EUVI 304 data, it can
be seen that the prominence footpoints change loctions during the
early stages of the eruption and, using stereoscopy, we find that
the new footpoints correspond to locations of EUVI 171 “endpoint
brightenings” discussed by Wang, Muglach and Kleim (ApJ, 2009) as
marking the outer edge of the transient coronal holes. Our observations
are consistent with their interpretation of the brightenings resulting
from magnetic reconnection between the erupting prominence magnetic
field and the overlying coronal arcade.
---------------------------------------------------------
Title: Coronal Mass Ejections from Empty Filament Channels
Authors: Pevtsov, A. A.; Panasenco, O.
2010AGUFMSH51A1659P Altcode:
Well-developed filament channels may be present in solar atmosphere
even when there is no trace of filament material inside it. When
erupted, such “empty” filament channels could result in coronal
mass ejections that might appear having no corresponding solar surface
source region. We analyze the magnetic field configuration and eruption
of a complete filament system, which includes magnetic neutral line,
filament channel, and the coronal cavity, but without the filament
material inside. We show that the presence of filament visible in
H-alpha or He II 304 A is not necessary for the eruption of magnetic
systems with "empty" filament channels.
---------------------------------------------------------
Title: Non-radial and Non-coaligned Propagation of Erupting Filaments
and CMEs
Authors: Panasenco, Olga; Velli, Marco
2010shin.confE.134P Altcode:
In the initial phases of a prominence eruption, the filament material
is seen to 'roll' sideways compared to the local vertical or radial
direction. The degree of the non-radial motion of a CME and the
degree and direction of the rolling motion of the filament plasma are
evidence of the global and local force imbalances occurring during
the eruption. Differences in the force at different positions and the
consequent deflections will produce the non-coaligned propagation of
erupting filament and corresponding CME. Generally speaking, above
and beyond the tendency of the eruption to move towards the weak
magnetic regions surrounding the null points above the structure,
there will also be a lateral deflection due to the lack of symmetry
in the local magnetic fields around the polarity reversal boundary
associated with the corresponding filament channel. We show examples of
lateral deflection due to the presence of a coronal hole on one side
of the filament channel and present magnetic intensity maps from pfss
modeling of the pre-existing coronal field. Though the pfss model by
definition has zero magnetic stresses, the intensity map gives a good
indication of where the forces will be strongest when the currents
associated with the eruption come into play.
---------------------------------------------------------
Title: How New Active Regions Trigger Erupting Filaments and
Associated Coronal Mass Ejections (CMEs)
Authors: Panasenco, Olga; Martin, Sara; Feynman, Joan
2010shin.confE..96P Altcode:
We initiated a study to learn why a quiescent or intermediate filament
has a strong tendency to erupt within 1-4 days of the appearance
of a new active region in its extended vicinity. To accomplish
this, we analyzed the evolution of new active regions that appeared
within 30 heliographic degrees of the center of quiescent filaments
or intermediate filaments in the decaying active regions or on the
periphery of active regions. To date we have studied 15 cases. Using
the potential-field source-surface (PFSS) model with Rss = 2.5Rsun,
we calculated time series of coronal loop changes from before the
birth of the new active regions until after the eruption of the nearby
filaments. We observed that the active regions gradually influence
increasingly larger areas around their initial sites apparently by
magnetic reconnection with pre-existing magnetic flux. Also, the
connectivity of coronal loops in adjacent areas was often greatly
changed. When the new extended fields, linked to an active region,
interacted with an adjacent coronal loop system overlying a filament,
often the result was a reduction in the density of loops around the
filament. In other words, the fields initially encompassing a filament
were reconfigured to connect to other adjacent areas on the Sun. This
reduction of the density of loops overlying a filament eventually
resulted in its complete eruption along with its enveloping cavity
and its surrounding coronal loops system. We surmise that the final
instability was driven by coronal magnetic reconnection beneath the
filament that resulted in a solar flare or flare-like brightening as
the eruption culminated. We suggest, however, that the eruption would
not occur in association with the reduced density of coronal loops over
filaments unless the magnetic field of the filament and/or the filament
cavity continuously exerted outward pressure on the loop system.
---------------------------------------------------------
Title: Magnetic Fields and Hα Filament Formation during Solar Minimum
Authors: Panasenco, O.; Pevtsov, A.
2010ASPC..428..123P Altcode:
We use multi-instrument observations taken during April 2007, a period
of extremely low sunspot activity, to investigate the properties
of magnetic fields and their potential role in the formation of
chromospheric filaments. For one studied case, we found that some of the
necessary conditions for forming a filament are: (1) a well-developed
filament channel exists, and (2) an overlying arcade is present, but
apparently there is insufficient material in Hα in the chromosphere to
form an enduring filament. Furthermore, when plasma observed in He II
304 Å is injected into the filament channel, we do see an Hα filament
appearing for a short period of time. Therefore, we conclude that the
main reason for the absence of filaments in Hα is that a mechanism
supplying material for a filament into the filament channel does not
work as efficiently as in other periods of the solar activity cycle.
---------------------------------------------------------
Title: Spicules and prominences: their life together .
Authors: Panasenco, O.
2010MmSAI..81..673P Altcode:
Spicules (fibrils against the disk) and filament channels are
fundamental parts of the solar chromosphere. What happens to fibrils
that are captured in a filament channel? It has been suggested
that "fibrils are associated with spicules" and that filaments
and fibrils are different in nature. However, those fibrils and
filaments living together in the same filament channel have to
follow the same magnetic topology rules. This allows us to trace
the structure of the magnetic field in the filament channel at
the chromospheric level. Spicules/fibrils inside a filament channel
represent a basement structure of the whole building of a filament and
filament cavity above. Therefore, understanding the magnetic pattern of
spicules/fibrils in the filament environment will help construct correct
filament/prominence models and resolve some old filament puzzles,
such as the bright rim observed near the feet of filaments/prominences.
---------------------------------------------------------
Title: On dynamical properties of filament channels
Authors: Martin, S. F.; Panasenco, O.
2010MmSAI..81..662M Altcode:
We discuss some of the least understood properties of filament
channels. This includes the three-dimensional rotational configuration
at their centers and the importance of cancelling magnetic fields
to their configuration. Intranetwork magnetic fields play a role
by interacting with network magnetic fields and these interactions
probably provide the ubiquitous fibrils of the chromosphere which
continuously adjust to the configurations of the dominant network
magnetic fields. Supergranules play a role by severely restricting the
intermingling of opposite polarity magnetic fields and controlling the
diffusion rates whereby opposite polarities network magnetic fields
slowly converge and form long and long-lived, polarity reversal
boundaries where filaments can form.
---------------------------------------------------------
Title: Plasma Motions in Prominences Observed by Hinode/SOT
Authors: Panasenco, O.; Velli, M.
2009ASPC..415..196P Altcode:
We analyze the plasma motions inside prominences observed by Hinode/SOT
during 2006-2007 with focus on the two spectacular examples from
25 April 2007 in Hα line and 30 November 2006 in the CaH line. It
is now well-known that most filaments (prominences on the limb) are
composed of fine threads of similar dimensions. Recent observations of
counter-streaming motions together with oscillations along the threads
provide strong evidence that the threads are field aligned. To more
correctly interpret the nature of observed downward flows of dense and
cool plasma as well as the upward dark flows of less dense plasma,
we take into account the geometry of the prominence structures and
the viewing angle. Basic plasma physical considerations lead one to
conclude that the magnetic field for the SOT observations considered
above must be mainly orthogonal to the plane of the sky.
---------------------------------------------------------
Title: Filaments, filament channels and their visibility during the
present solar minimum
Authors: Panasenco, O.; Martin, S. F.; Panasenco, A.
2009AGUFMSH11A1494P Altcode:
An unexpected aspect of the current long solar minimum between solar
cycles 23 and 24 is that polar crown prominences have been observed
nearly continuously above the solar limb. However, many of the same
polar crown prominences have had only small sections visible against the
chromosphere in H-alpha and these sections change from day to day. The
presence of much more extensive mass than seen in H-alpha is certain
because filaments are seen against the disk much more completely in 304A
than in H-alpha. These differences in filament visibility offer a good
opportunity to test our concepts of the relationship between filament
mass seen in H-alpha and the rate of cancelling magnetic fields in
the photosphere. We know from previous observations and theory over
more than 20 years that the existence of filaments is closely related
to canceling magnetic fields observed at the photosphere. We have made
the hypothesis that there is a threshold in the rate of canceling fields
below which filaments are not visible against the solar disk in H-alpha
but this concept has not been tested. We are testing this hypothesis
by calculating the rates of canceling magnetic flux for the different
filaments during their passing across the disk for the current minimum
and previous maximum of 23rd solar cycle. In our analyses we use data
sets from SOHO/MDI, SOHO/EIT, STEREO and ground based observatories.
---------------------------------------------------------
Title: Relating a Prominence Observed from the Solar Optical Telescope
on the Hinode Satellite to Known 3-D Structures of Filaments
Authors: Martin, S. F.; Panasenco, O.; Agah, Y.; Engvold, O.; Lin, Y.
2009ASPC..415..183M Altcode:
We address only a first step in relating limb and disk observations
by illustrating and comparing the spines and barbs of three different
quiescent prominences and filaments observed in Hα by three different
telescopes. Although the appearance of the three quiescent prominences
is quite different, we show that each consists of a spine, barbs
extending from the spine, and arcs at the base of some of the curtains
of barb threads.
---------------------------------------------------------
Title: Erupting Chromospheric Filaments
Authors: Balasubramaniam, K. S.; Cliver, E.; Pevtsov, A.; Martin,
S.; Panasenco, O.
2009SPD....40.1010B Altcode:
Erupting filaments are commonly associated with coronal mass
ejections. They represent the chromospheric structures most closely tied
to the underlying photospheric magnetic fields. We present an analysis
of the eruption of an unusually large filament on the SE quadrant of the
solar disc on 2003 June 11. The data are drawn from USAF/NSO Improved
Solar Observing Optical Network, Solar and Heliospheric Observatory,
and ground-based telescopes at NSO. The filament rises with an initial
slow speed of 6-7 km/s over a period of 2 hours and later erupts by
rapidly accelerating to 170 km/s second in the following 30 minutes. The
filament eruption is accompanied by a flare in a neighboring active
region. We trace morphological and topological changes in the filament
and overlying arcade before and during its eruption, and interpret
these changes in terms of physical structure of the filament and whole
filament system. The destabilization of the filament and its overlying
coronal arcade are related to interactions with a new emerging active
region, and adjacent active region.
---------------------------------------------------------
Title: Fine-Structured Plasma Flows in Prominences
Authors: Panasenco, O.; Velli, M.; Landi, S.
2008AGUFMSH41A1613P Altcode:
Plasmas in prominences (filaments against the disk) exhibit a very
wide spectrum of different kind of motions. Here we analyze the plasma
motions inside prominences observed by Hinode/SOT during 2006-2007 with
focus on two spectacular examples from 25 April 2007 in Halpha line
and 30 November 2006 in CaH line and then carry out some simulations
of the possible dynamics. Most filaments are composed of fine threads
of similar dimensions rooted in the chromosphere/photosphere. Recent
observations of counter-streaming motions together with oscillations
along the threads provide strong evidence that the threads are field
aligned. To more correctly interpret the nature of observed downward
flows of dense and cool plasma as well as the upward dark flows of
less dense plasma, we take into account the geometry of the prominence
structures and the viewing angle. The dark upflows exhibit turbulent
patterns such as vortex formation and shedding that are consistent
with the motions predicted by instabilities of the interchange
type. Sometimes an appearance of dark motions is generated by dark
voids opened in the prominence sheet after initiation of nearby
downflow streams, implying mass drainage in the downflows. Based on
304 A observations, there is more filament mass in prominences than is
visible in either the Halpha or CaH lines. The source of the downward
moving plasma may be located either higher above the visible upper edge
of the prominence or on the far end of the prominence spine. The bright
downward motions of the more cool and dense plasma may be partly due
to the counter-streaming motion along the magnetic fields lines and
also to the presence of Rayleigh-Taylor type or ballooning/interchange
instabilities in the upper regions of the prominence. Transverse motions
of filament threads caused by magnetic instabilities constantly provide
the conditions for reconnection in the low part of the corona and the
chromosphere. We suggest that the combination of flows along field
lines, shear, and unstable stratification may provide the answers to
the intriguingly elegant motions seen in prominences.
---------------------------------------------------------
Title: The Unique 3D Magnetic Structure of Filaments
Authors: Lin, Y.; Engvold, O.; Martin, S.; Panasenco, O.
2008AGUSMSH23A..05L Altcode:
Filaments in active regions most clearly have the form of long
thin ribbons as seen in Hα. The ribbon structure is also readily
demonstrated for quiescent filaments when seen from an end view as
a filament is transported across the east or west limb due to solar
rotation. In addition to the primary ribbon structure, filaments
also have shorter, secondary structures called barbs which connect
some threads of the main ribbon structure to the chromosphere;
these are also seen in the end view of filaments at the limb. This
connection with the chromosphere is corroborated in high resolution
images of filaments recorded against the disk at the 1-meter Swedish
Solar Telescope (SST). In these high resolution Hα movies, the lower
parts of all threads are recognizable because they move less freely
than the higher parts. The connection of the ends of the threads of
the main filament ribbon and the ends of the filament barbs to the
chromosphere/photosphere is strong evidence alone that filaments have
their own magnetic fields separate from surrounding coronal magnetic
fields. The chirality (handedness) of filaments provides further
evidence that filaments have their own magnetic fields. The two forms of
dextral and sinistral chirality are generally manifest in the relative
direction of the deviation of barbs from the main ribbon. However, the
sign of chirality is most clear in the thread structure of all barbs
seen in Hα images from the SST. From a number of characteristics of
the observed mass motions of filament threads of the order of several
to tens of kilometers per second, we have previously concluded that
filament threads are field-aligned. Therefore we use the threads
and their mass motions to construct the 3D configuration of filament
magnetic fields. We end this presentation with movies of filaments
from STEREO/SECCHI/EUVI consistent with our thread model of filaments.
---------------------------------------------------------
Title: Topological Analyses of Symmetric Eruptive Prominences
Authors: Panasenco, O.; Martin, S. F.
2008ASPC..383..243P Altcode:
Erupting prominences (filaments) that we have analyzed from Hα
Doppler data at Helio Research and from SOHO/EIT 304 Å, show strong
coherency between their chirality, the direction of the vertical and
lateral motions of the top of the prominences, and the directions
of twisting of their legs. These coherent properties in erupting
prominences occur in two patterns of opposite helicity; they constitute
a form of dynamic chirality called the “roll effect." Viewed from
the positive network side as they erupt, many symmetrically-erupting
dextral prominences develop rolling motion toward the observer along
with right-hand helicity in the left leg and left-hand helicity in
the right leg. Many symmetricaly-erupting sinistral prominences, also
viewed from the positive network field side, have the opposite pattern:
rolling motion at the top away from the observer, left-hand helical
twist in the left leg, and right-hand twist in the right leg. We have
analysed the motions seen in the famous movie of the “Grand Daddy"
erupting prominence and found that it has all the motions that define
the roll effect. From our analyses of this and other symmetric erupting
prominences, we show that the roll effect is an alternative to the
popular hypothetical configuration of an eruptive prominence as a
twisted flux rope or flux tube. Instead we find that a simple flat
ribbon can be bent such that it reproduces nearly all of the observed
forms. The flat ribbon is the most logical beginning topology because
observed prominence spines already have this topology prior to eruption
and an initial long magnetic ribbon with parallel, non-twisted threads,
as a basic form, can be bent into many more and different geometrical
forms than a flux rope.
---------------------------------------------------------
Title: Chromospheric and coronal manifestations of photospheric
cancelling magnetic fields
Authors: Panasenco, Olga; Martin, Sara F.; Engvold, Oddbjorn
2008cosp...37.2336P Altcode: 2008cosp.meet.2336P
We discuss observable changes in solar features interpreted as
evidences of the transfer of magnetic fields from the photosphere
to the chromosphere and corona. In the photospheric level, new
or decayed active region magnetic fields of opposite polarity
encounter each other and cancel along a pre-existing polarity
reversal boundary. Concurrently, in the chromospheric level of
the solar atmosphere, the cancelling fields appear to lead to the
creation and maintenance of a filament channel. The channel is
identified by systematic changes in the orientation of fibrils
in the chromosphere. We deduce that invisible extensions of the
magnetic fields of the chromospheric fibrils into the corona could
represent the beginning of the formation of a filament cavity in the
low corona, before and/or during the initial appearance of a filament
threads. When the filament channel is fully developed, such that there
is a local magnetic field aligned with the polarity reversal boundary,
the cancelling fields are then associated with the transfer of plasma,
as well as magnetic field, into the low corona. We suggest this plasma
is observed as new filament threads.
---------------------------------------------------------
Title: Vertical plasma motions in prominence sheets observed by Hinode
Authors: Panasenco, Olga; Velli, Marco; Berger, Thomas
2008cosp...37.2337P Altcode: 2008cosp.meet.2337P
We analyze the approximately vertical motions inside prominence plasma
observed by Hinode on 25 April 2007 in Hα line and 30 November 2006 in
CaH line. Well-established observational facts are that all filaments
(prominences on the limb) are composed of fine threads of similar
dimensions, rooted in the photosphere and presumably tracing magnetic
field lines, and that continuous counter-streaming motions occur
along threads. We take into account the geometry of the prominence
sheet and the viewing angle to reduce possible projection effect and
more correctly interpret the nature of observational downward flows
of denser and cooler plasma as well as the upward flow of hotter
plasma which appears dark in the Hα and CaH spectral lines. The dark
upflows exhibit turbulent flow properties such as vortex formation and
shedding that are consistent with the properties of thermal starting
plumes. Sometimes an illusion of dark upward motion is generated by
rarefactions in the plasma sheet caused by the cooler denser downward
flows. On both dates, we suspect there is probably more filament mass
in the prominence that is visible in either the Hα or CaH lines. The
source of the downward moving plasma may be located either higher
above the visible upper edge of the prominence or on the far end of
the prominence spine. The bright downward motions of the more cool
and dense plasma may be partly due to the counter-streaming motion
along the magnetic fields lines, or it may be due to the presence of
rayleigh-taylor type or ballooning/interchange instabilities in the
upper regions of the prominence, which are then stabilized lower down
where the magnetic field is stronger and the plasma beta lower.
---------------------------------------------------------
Title: Chromospheric observations of erupting filaments with the
Optical Solar Patrol Network (OSPaN) telescope
Authors: Cliver, Edward; Balasubramaniam, K. S.; Cliver, E. W.;
Engvold, O.; Pevtsov, A.; Martin, S.; Panasenco, O.
2008cosp...37..562C Altcode: 2008cosp.meet..562C
Using AFRL/NSO OSPaN telescope chromospheric images, we present movies
and analyses of the eruption of a quiescent filament (11 June 2003)
and an active region filament (13 May 2005). In both cases, widely
separated regions of the solar surface were affected by the eruptions,
either via the Moreton waves they generated (inferred from winking
filaments) or through direct magnetic connection (manifested by
sequential chromospheric brightenings). We investigate the topology
of the magnetic fields in which these eruptions occur and use Doppler
measurements to understand the dynamics of the eruptions.
---------------------------------------------------------
Title: STEREO 3D Data of the Fast Formation of the Ribbon-Like
Prominences and Their Dynamics During Eruption
Authors: Panasenco, O.; Martin, S. F.
2007AGUFMSH41B..07P Altcode:
We have analyzed STEREO/SECCHI/EUVI Helium 304Å data and created
3-dimensional geometrical models for the two erupting prominences
observed by STEREO. 3D STEREO movies, made by combining views from
the two spacecraft, allow us to understand the true 3D structure of
the prominences before and during eruption. In a movie from 12 May
2007 we can see the fast filling of the existing filament channel
by plasma. This fast formation of the prominence allows us to trace
in time and space the appearance of the main structural parts of the
prominence: the barbs and the flat ribbon shape of the whole body of
the prominence. We have analyzed the formation and development these
structures before eruption and the motion of the erupting part of the
prominence during eruption. We found that the motion of the erupting
prominence shows the roll effect of the top of prominence. The STEREO
movie from 16 May 2007 shows us another clear example of the roll effect
during prominence eruption. The observed fast filling of the existing
filament channel by plasma and the quick formation of the prominence
with the ribbon-like geometrical structure, followed by the partial
eruption with the obvious roll effect are the clear evidence of non flux
rope magnetic nature of prominences. Our qualitative model of prominence
formation by cancelling of magnetic flux at the photosphere and magnetic
reconnection in the chromosphere and corona is in agreement with the
STEREO observational facts of formation and eruption of prominences.
---------------------------------------------------------
Title: Coronal mass ejection and solar flare initiation processes
without appreciable changes of the large-scale magnetic field topology
Authors: Veselovsky, I. S.; Panasenco, O. A.
2006AdSpR..37.1305V Altcode:
We demonstrate that spurious three-dimensional re-constructions from
two-dimensional images and movies of solar flares and coronal mass
ejections can arise as a result of viewing conditions and projection
effects, which are not always properly taken into account in the
current literature. Theory and observations indicate that eruptions can
proceed with or without large-scale topological changes of prominences
and coronal magnetic fields. Electric currents and plasma drifts in
crossed electric and magnetic fields play not negligible, but important
role. This means that large-scale magnetic reconnections understood as
topological transitions in the magnetic field are not always necessary
for eruptions. The scenario of expanding and rising non-planar systems
of preexisting loops and arcades, which are deforming when shearing
at bottom parts, twisting and rotating at summits, satisfactory fits
available observations. Movies are presented demonstrating this type
of behavior with a preserved magnetic connectivity.
---------------------------------------------------------
Title: On the Statistics of the Seasonal Geomagnetic Variations.
Authors: Panasenco, O.; Veselovsky, I.
2005AGUFMSM51B1300P Altcode:
We analyze the data sets of daily average Dst (1957-2005) and Ap
(1932-2005) indices. Differential and integral statistical distribution
functions of geomagnetic perturbations versus their strength
constructed. First moments of the distributions calculated. Asymptotic
behavior of the distributions at extremely low and high magnetic
activity as well as around mean and most probable states obtained
for the whole data sets and for the selected periods of time (spring
and autumn, summer and winter) around equinoxes and solstices. We
confirm and extend the results of some previous studies. Absolute and
relative amplitudes of seasonal geomagnetic variations interpreted as
a consequence of the non-linear magnetospheric response to the solar
and heliospheric drivers.
---------------------------------------------------------
Title: Solar origins of intense geomagnetic storms in 2002 as seen
by the CORONAS-F satellite
Authors: Panasenco, O.; Veselovsky, I. S.; Dmitriev, A. V.; Zhukov,
A. N.; Yakovchouk, O. S.; Zhitnik, I. A.; Ignat'ev, A. P.; Kuzin,
S. V.; Pertsov, A. A.; Slemzin, V. A.; Boldyrev, S. I.; Romashets,
E. P.; Stepanov, A.; Bugaenco, O. I.; Bothmer, V.; Koutchmy, S.;
Adjabshirizadeh, A.; Fazel, Z.; Sobhanian, S.
2005AdSpR..36.1595P Altcode:
We analyze solar origins of intense geomagnetic perturbations recorded
during 2002. All of them were related to coronal mass ejections
(CMEs). The initiation of CMEs was documented using the SPIRIT
instrument (SPectrohelIographic Soft X-Ray Imaging Telescope) onboard
the CORONAS-F satellite. Monochromatic full Sun images taken in the Mg
XII doublet at 8.418 and 8.423 Å showed the appearance of free energy
release sites at altitudes up to 0.4 solar radii. CMEs were initiated
at these sites and propagated in interplanetary space under appropriate
local conditions including the geometry of the magnetic fields.
---------------------------------------------------------
Title: Solar and Heliospheric Phenomena in October-November 2003:
Causes and Effects
Authors: Veselovsky, I. S.; Panasyuk, M. I.; Avdyushin, S. I.;
Bazilevskaya, G. A.; Belov, A. V.; Bogachev, S. A.; Bogod, V. M.;
Bogomolov, A. V.; Bothmer, V.; Boyarchuk, K. A.; Vashenyuk, E. V.;
Vlasov, V. I.; Gnezdilov, A. A.; Gorgutsa, R. V.; Grechnev,
V. V.; Denisov, Yu. I.; Dmitriev, A. V.; Dryer, M.; Yermolaev,
Yu. I.; Eroshenko, E. A.; Zherebtsov, G. A.; Zhitnik, I. A.;
Zhukov, A. N.; Zastenker, G. N.; Zelenyi, L. M.; Zeldovich,
M. A.; Ivanov-Kholodnyi, G. S.; Ignat'ev, A. P.; Ishkov, V. N.;
Kolomiytsev, O. P.; Krasheninnikov, I. A.; Kudela, K.; Kuzhevsky,
B. M.; Kuzin, S. V.; Kuznetsov, V. D.; Kuznetsov, S. N.; Kurt, V. G.;
Lazutin, L. L.; Leshchenko, L. N.; Litvak, M. L.; Logachev, Yu. I.;
Lawrence, G.; Markeev, A. K.; Makhmutov, V. S.; Mitrofanov, A. V.;
Mitrofanov, I. G.; Morozov, O. V.; Myagkova, I. N.; Nusinov, A. A.;
Oparin, S. N.; Panasenco, O. A.; Pertsov, A. A.; Petrukovich, A. A.;
Podorol'sky, A. N.; Romashets, E. P.; Svertilov, S. I.; Svidsky, P. M.;
Svirzhevskaya, A. K.; Svirzhevsky, N. S.; Slemzin, V. A.; Smith, Z.;
Sobel'man, I. I.; Sobolev, D. E.; Stozhkov, Yu. I.; Suvorova, A. V.;
Sukhodrev, N. K.; Tindo, I. P.; Tokhchukova, S. Kh.; Fomichev, V. V.;
Chashey, I. V.; Chertok, I. M.; Shishov, V. I.; Yushkov, B. Yu.;
Yakovchouk, O. S.; Yanke, V. G.
2004CosRe..42..435V Altcode:
We present new observational data on the phenomena of extremely
high activity on the Sun and in the heliosphere that took place
in October-November 2003. A large variety of solar and heliospheric
parameters give evidence that the interval under consideration is unique
over the entire observation time. Based on these data, comparing them
with similar situations in the past and using available theoretical
concepts, we discuss possible cause-and-effect connections between
the processes observed. The paper includes the first results and
conclusions derived by the collaboration “Solar Extreme Events-2003”
organized in Russia for detailed investigations of these events. As a
result of our consideration, it is beyond question that the physical
causes of solar and heliospheric phenomena in October-November 2003
are not exclusively local and do not belong only to the active regions
and solar atmosphere above them. The energy reservoirs and driving
forces of these processes have a more global nature. In general, they
are hidden from an observer, since ultimately their sources lie in
the subphotospheric layers of the Sun, where changes that are fast
and difficult to predict can sometimes take place (and indeed they
do). Solar flares can serve as sufficiently good tracers of these sudden
changes and reconstructions on the Sun, although one can still find
other diagnostic indicators among the parameters of magnetic fields,
motions of matter, and emission characteristics.
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Title: Dynamics of the loop prominence and coronal mass ejection
observed on March 2, 2002
Authors: Panasenco, O.; Veselovsky, I. S.; Zhukov, A. N.; Yakovchouk,
O. S.; Koutchmy, S.; Delaboudiniere, J. -P.
2004cosp...35.2974P Altcode: 2004cosp.meet.2974P
SOHO/EIT and LASCO data are used for the case study of the coronal mass
ejection initiation and development. The shape, velocity and temperature
of the loop prominence before and during the ejection as well as the
new arcade formation are well documented. The prominence consisted of
two spirals interweaved on the semi-torus. Both spirals are clearly
seen during the initial stage of the expansion with a velocity about
300 km/s. Than, one of them is rapidly heated, when other remained
cool. The number of curls is conserved during the expansion. The
main axis of the torus is initially represented by the planar curve
resembling a semi-circle. After some time, the summit of the torus
is twisted in the manner that the main axis looks not planar at the
top in the field of view of LASCO C3 when the velocity attains about
1000 km/s. The topological connectivity of the loops to the Sun is
preserved for more than three hours even after the new arcade formation.
---------------------------------------------------------
Title: Solar origins of intense geomagnetic storms in 2002 as seen
by the CORONAS-F satellite.
Authors: Panasenco, O.; Panasenco Team
2004cosp...35.3005P Altcode: 2004cosp.meet.3005P
The initiation of coronal mass ejections responsible for intense
heliospheric perturbations and strong geomagnetic storms was observed
by the SPIRIT (Spectro-heliographic soft X-ray imaging telescope)
onboard CORONAS-F satellite. Monochromatic full Sun images in MgXII
doublet 8,418 and 8,423Å revealed the appearance of the free energy
releases at altitudes up to 0,4 R<SUB>⊙</SUB>. Sometimes complex
situations on the Sun and in the heliosphere arise. The continuous
monitoring of the solar images with a time resolution of minutes could
be a useful tool for "space weather" application.
---------------------------------------------------------
Title: Non-local dissipative structures in the solar corona:
flaring loops
Authors: Veselovsky, Igor S.; Panasenco, O. A.
2002ESASP.508..461V Altcode: 2002soho...11..461V
Several dimensionless parameters are described for the non-local
multi-scale coronal processes. The quantitative measures are indicated
for the openness degree of solar structures. Flare-like and CME-like
energy releases are delimited.
---------------------------------------------------------
Title: Global asymmetry of the Sun observed in the extreme ultraviolet
radiation
Authors: Zhukov, A. N.; Veselovsky, I. S.; Hochedez, J. -F.; Clette,
F.; Panasenco, O. A.; Cugnon, P.
2002ESASP.508..189Z Altcode: 2002soho...11..189Z
We report on the observations of the solar luminosity variations in
four SOHO/EIT bandpasses over the period 1996 - 2001. Contributions
of coronal holes, intermediate brightness features, active regions
and bright points are evaluated. We find that during the epoch of low
activity a significant contribution to the longitudinal asymmetry, and
thus to the 27-day variability of the solar EUV radiation, is produced
by the numerous intermediate brightness elements that are globally
distributed over large areas (up to 2/3 of the whole surface of the Sun)
and generally correspond to the "quiet Sun". During the activity minimum
the contribution of this component is comparable to the active regions
contribution. The "quiet Sun" average brightness exhibits rotational
modulation throughout half of the solar cycle observed by SOHO.
---------------------------------------------------------
Title: Reversal of Heliospheric Magnetic Field Polarity: Theoretical
Model
Authors: Veselovsky, I. S.; Zhukov, A. N.; Panasenco, O. A.
2002SoSyR..36...80V Altcode:
A simple analytical model of the reversal of the heliospheric magnetic
field is suggested. The shape of the heliospheric current sheet is found
for each instant of time using a kinematic approximation. Calculation
results are illustratively presented in graphic and animated forms,
showing a 3-D dynamic picture of the reversal of the heliospheric
magnetic field throughout a 22-year solar cycle.
---------------------------------------------------------
Title: Heliospheric magnetic field polarity reversal: theoretical
model
Authors: Veselovsky, I.; Panasenco, O.; Zhukov, A.
2002cosp...34E.376V Altcode: 2002cosp.meetE.376V
We have developed the kinematic model of the heliospheric magnetic field
reversal taking into account the time-dependent boundary conditions at
the rotating Sun and the radial solar wind outflow. The heliospheric
current sheet shape is calculated when projected from the source
surface. In the simplest case only the dipole-like term is retained
for illustrative purposes. We consider two possible scenarios:
slow and fast reversals. In the first scenario the turn-over lasts
longer than a transit time which is about one year. The resulting
Archimedian pattern is gradually changing its inclination against
the solar rotation axis during this quasistationary process. In the
second scenario the transient current sheet shape represents the
double spiral pattern. Based on this model, we interpret the recent
Ulysses measurements during the maximum of the 23-rd solar activity
cycle. The movie demonstration of the model is available at the web
page: http://dec1.npi.msu.su/english/lse.
---------------------------------------------------------
Title: Multi-scale electric currents and their volume convolutions
in the solar corona and the heliosphere
Authors: Veselovsky, I.; Panasenco, O.; Zhukov, A.
2002cosp...34E.415V Altcode: 2002cosp.meetE.415V
We present observational evidences of the global electric circuit on
the Sun and in the heliosphere. The intermediate scale macroscopic
structure and dynamics of this circuit manifests in active regions,
coronal cavities and streamers, filaments and prominences, flares and
ejections. Unresolved MHD and kinetic processes are nonlinearly coupled
to larger scales producing direct and inverse cascades documented in
the turbulent convective and wave spectra. Heliospheric current sheets
and flux ropes represent the sites of the free electromagnetic energy
concentrations, which are responsible for geomagnetic perturbations. The
dimensionless scaling approach is used to evaluate the orders of
magnitudes and physical regimes for dissipative MHD and kinetic
structures associated with different morphological features produced
by electric currents. Conserved and evolving volume integrals including
electric currents are considered for isolated and open externally driven
system. The electric currents produce important non-local couplings
between different elements in the solar atmosphere, heliosphere and
interiors, which can be parameterized by dimensionless Trieste numbers
including internal, external and linking parameters. The usefulness of
the integral quantities like partial and total currents, magnetic fields
and fluxes, free magnetic energy, electric current and magnetic field
helicities is considered both from theoretical and observational points
of view. The better observational knowledge is needed of the interplay
between different space-time scales and structures of concentrated
current sheets and strong linear currents for the understanding of
the cause - sequence chains in dynamical solar events.
