Author name code: chintzoglou
ADS astronomy entries on 2022-09-14
author:"Chintzoglou, Georgios"
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Title: Predicted appearance of Magnetic Flux Rope and Sheared Magnetic
Arcade Structures before a Coronal Mass Ejection via three-dimensional
radiative Magnetohydrodynamic Modeling
Authors: Chintzoglou, Georgios; Cheung, Mark; Rempel, Matthias
Bibcode: 2022cosp...44.2406C
Altcode:
Magnetic Flux Ropes (MFRs) are free-energy-carrying, three-dimensional
magnetized plasma structures characterized by twisted magnetic field
lines and are widely considered the core structure of Coronal Mass
Ejections (CMEs) propagating in the interplanetary space. The way MFRs
form remains unclear as different theories predict that either MFRs
form during the initiation of the CME or pre-exist the onset of the
CME. The term "pre-existing structure" is synonymous with "filament
channels." On the one hand, the theories predicting on-the-fly MFR
formation require Sheared Magnetic Arcades (SMAs; low twist but
stressed magnetic structures) for the filament channel/pre-existing
magnetic structure of CMEs. On the other hand, a growing number of
works using SDO/AIA observations (combined with non-linear force-free
extrapolations; NLFFF) suggest that MFRs may be the form of filament
channels, therefore pre-existing the CME eruption. However, due to
the inability to routinely measure the 3D magnetic field in the solar
atmosphere, we cannot unambiguously interpret optical and EUV imaging
observations as projected on the plane of the sky. Therefore, a raging
debate on the nature of the pre-eruptive structure continues. It is
also possible that the filament channel/pre-eruptive structure evolves
from SMA to MFR slowly, further complicating the distinction between
these two types of structures in the solar observations. This work
presents realistic simulated optical and EUV observations synthesized
on a time-evolving radiative MURaM MHD model at different times
along the slow evolution of an SMA converting to an MFR. We discuss
the implications of our results in the context of filament channel
formation and CME initiation theory.
Title: Sun Sailing Polar Orbiting Telescope (SunSPOT): A solar polar
imaging mission design
Authors: Probst, A.; Anderson, T.; Farrish, A. O.; Kjellstrand,
C. B.; Newheart, A. M.; Thaller, S. A.; Young, S. A. Q.; Rankin, K.;
Akhavan-Tafti, M.; Chartier, A.; Chintzoglou, G.; Duncan, J.; Fritz,
B.; Maruca, B. A.; McGranaghan, R. M.; Meng, X.; Perea, R.; Robertson,
E.; Lowes, L.; Nash, A.; Romero-Wolf, A.; Team-X
Bibcode: 2022AdSpR..70..510P
Altcode:
Although the Sun has been a focus of space-based research for several
decades, there are still many open questions. One severe gap in solar
physics knowledge is the lack of detailed, long-term observations of the
solar polar regions to explore the origins of the Sun's magnetism and
other connected phenomena. To fill this gap, this paper presents
a feasibility study of a mission concept for a solar polar orbiting
imaging mission called the Sun Sailing Polar Orbiting Telescope
(SunSPOT). SunSPOT utilizes a doppler magnetograph instrument to
observe the polar magnetic structure and a large deployable solar sail
to reach high inclination orbit. The mission concept is derived from
two science objectives investigating the formation of solar active
regions and the solar dynamo. These objectives are aligned with the
science goals formulated by the National Research Council (NRC) in
the 2013 Decadal Survey in Solar and Space Physics and their science
closure is shown in the Science Traceability Matrix. The mission and
spacecraft design are explained, including a cost and risk analysis,
with a special focus on the requirements and risks of the solar
sail propulsion system. While the solar sail presents a significant
design challenge and financial risk to this and other proposed solar
polar missions, it is a necessity to achieve the orbit required for
closure of decadal science goals. Although originally conceived of as
a Discovery-class mission fitting within a 600 M budget, the solar
sail pushes the cost beyond this threshold. The work presented
here is the outcome of the NASA Heliophysics Mission Design School
(HMDS) 2020 hosted by the NASA Jet Propulsion Laboratory.
Title: Probing the Physics of the Solar Atmosphere with the Multi-slit
Solar Explorer (MUSE). II. Flares and Eruptions
Authors: Cheung, Mark C. M.; Martínez-Sykora, Juan; Testa, Paola;
De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito,
Vanessa; Kerr, Graham S.; Reeves, Katharine K.; Fletcher, Lyndsay; Jin,
Meng; Nóbrega-Siverio, Daniel; Danilovic, Sanja; Antolin, Patrick;
Allred, Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward;
Longcope, Dana; Takasao, Shinsuke; DeRosa, Marc L.; Boerner, Paul;
Jaeggli, Sarah; Nitta, Nariaki V.; Daw, Adrian; Carlsson, Mats; Golub,
Leon; The
Bibcode: 2022ApJ...926...53C
Altcode: 2021arXiv210615591C
Current state-of-the-art spectrographs cannot resolve the fundamental
spatial (subarcseconds) and temporal (less than a few tens of
seconds) scales of the coronal dynamics of solar flares and eruptive
phenomena. The highest-resolution coronal data to date are based on
imaging, which is blind to many of the processes that drive coronal
energetics and dynamics. As shown by the Interface Region Imaging
Spectrograph for the low solar atmosphere, we need high-resolution
spectroscopic measurements with simultaneous imaging to understand the
dominant processes. In this paper: (1) we introduce the Multi-slit Solar
Explorer (MUSE), a spaceborne observatory to fill this observational
gap by providing high-cadence (<20 s), subarcsecond-resolution
spectroscopic rasters over an active region size of the solar transition
region and corona; (2) using advanced numerical models, we demonstrate
the unique diagnostic capabilities of MUSE for exploring solar coronal
dynamics and for constraining and discriminating models of solar flares
and eruptions; (3) we discuss the key contributions MUSE would make
in addressing the science objectives of the Next Generation Solar
Physics Mission (NGSPM), and how MUSE, the high-throughput Extreme
Ultraviolet Solar Telescope, and the Daniel K Inouye Solar Telescope
(and other ground-based observatories) can operate as a distributed
implementation of the NGSPM. This is a companion paper to De Pontieu
et al., which focuses on investigating coronal heating with MUSE.
Title: Probing the Physics of the Solar Atmosphere with the Multi-slit
Solar Explorer (MUSE). I. Coronal Heating
Authors: De Pontieu, Bart; Testa, Paola; Martínez-Sykora, Juan;
Antolin, Patrick; Karampelas, Konstantinos; Hansteen, Viggo; Rempel,
Matthias; Cheung, Mark C. M.; Reale, Fabio; Danilovic, Sanja; Pagano,
Paolo; Polito, Vanessa; De Moortel, Ineke; Nóbrega-Siverio, Daniel;
Van Doorsselaere, Tom; Petralia, Antonino; Asgari-Targhi, Mahboubeh;
Boerner, Paul; Carlsson, Mats; Chintzoglou, Georgios; Daw, Adrian;
DeLuca, Edward; Golub, Leon; Matsumoto, Takuma; Ugarte-Urra, Ignacio;
McIntosh, Scott W.; the MUSE Team
Bibcode: 2022ApJ...926...52D
Altcode: 2021arXiv210615584D
The Multi-slit Solar Explorer (MUSE) is a proposed mission composed of
a multislit extreme ultraviolet (EUV) spectrograph (in three spectral
bands around 171 Å, 284 Å, and 108 Å) and an EUV context imager (in
two passbands around 195 Å and 304 Å). MUSE will provide unprecedented
spectral and imaging diagnostics of the solar corona at high spatial
(≤0.″5) and temporal resolution (down to ~0.5 s for sit-and-stare
observations), thanks to its innovative multislit design. By obtaining
spectra in four bright EUV lines (Fe IX 171 Å, Fe XV 284 Å, Fe XIX-Fe
XXI 108 Å) covering a wide range of transition regions and coronal
temperatures along 37 slits simultaneously, MUSE will, for the first
time, "freeze" (at a cadence as short as 10 s) with a spectroscopic
raster the evolution of the dynamic coronal plasma over a wide range of
scales: from the spatial scales on which energy is released (≤0.″5)
to the large-scale (~170″ × 170″) atmospheric response. We use
numerical modeling to showcase how MUSE will constrain the properties of
the solar atmosphere on spatiotemporal scales (≤0.″5, ≤20 s) and
the large field of view on which state-of-the-art models of the physical
processes that drive coronal heating, flares, and coronal mass ejections
(CMEs) make distinguishing and testable predictions. We describe the
synergy between MUSE, the single-slit, high-resolution Solar-C EUVST
spectrograph, and ground-based observatories (DKIST and others), and
the critical role MUSE plays because of the multiscale nature of the
physical processes involved. In this first paper, we focus on coronal
heating mechanisms. An accompanying paper focuses on flares and CMEs.
Title: Probing the Physics of the Solar Atmosphere with the Multi-slit
Solar Explorer (MUSE): II. Flares and Eruptions
Authors: Cheung, Chun Ming Mark; Martinez-Sykora, Juan; Testa, Paola;
De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito,
Vanessa; Kerr, Graham; Reeves, Katharine; Fletcher, Lyndsay; Jin,
Meng; Nobrega, Daniel; Danilovic, Sanja; Antolin, Patrick; Allred,
Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward; Longcope,
Dana; Takasao, Shinsuke; DeRosa, Marc; Boerner, Paul; Jaeggli, Sarah;
Nitta, Nariaki; Daw, Adrian; Carlsson, Mats; Golub, Leon
Bibcode: 2021AGUFMSH51A..08C
Altcode:
Current state-of-the-art spectrographs cannot resolve the fundamental
spatial (sub-arcseconds) and temporal scales (less than a few tens
of seconds) of the coronal dynamics of solar flares and eruptive
phenomena. The highest resolution coronal data to date are based on
imaging, which is blind to many of the processes that drive coronal
energetics and dynamics. As shown by IRIS for the low solar atmosphere,
we need high-resolution spectroscopic measurements with simultaneous
imaging to understand the dominant processes. In this paper: (1)
we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne
observatory to fill this observational gap by providing high-cadence
(<20 s), sub-arcsecond resolution spectroscopic rasters over an
active region size of the solar transition region and corona; (2)
using advanced numerical models, we demonstrate the unique diagnostic
capabilities of MUSE for exploring solar coronal dynamics, and for
constraining and discriminating models of solar flares and eruptions;
(3) we discuss the key contributions MUSE would make in addressing the
science objectives of the Next Generation Solar Physics Mission (NGSPM),
and how MUSE, the high-throughput EUV Solar Telescope (EUVST) and the
Daniel K Inouye Solar Telescope (and other ground-based observatories)
can operate as a distributed implementation of the NGSPM. This is a
companion paper to De Pontieu et al. (2021, also submitted to SH-17),
which focuses on investigating coronal heating with MUSE.
Title: A Mechanism Driving Recurrent Eruptive Activity on the Sun
Authors: Chintzoglou, Georgios; Cheung, Chun Ming Mark
Bibcode: 2021AGUFMSH42B..09C
Altcode:
Active Regions (ARs) in their emergence phase are known to be more flare
productive and eruptive than ARs in their decay phase. In this work,
we focus on complex emerging ARs composed of multiple bipoles. Due
to the compact clustering of the different emerging bipoles within
such complex multipolar ARs, collision and shearing between opposite
non-conjugated polarities produce collisional polarity inversion
lines (cPILs) and drive rapid photospheric cancellation of magnetic
flux. The strength and the duration of the collision, shearing, and
cancellation are defined by the natural separation of the conjugated
polarities during the emergence phase of each bipole in the AR. This
mechanism is called collisional shearing. In Chintzoglou et al (2019),
collisional shearing was demonstrated using two emerging flare- and
CME-productive ARs (NOAA AR11158 and AR12017) by measuring significant
amounts of magnetic flux canceling at the cPIL. This finding supported
the formation and energization of magnetic flux ropes before their
eruption as CMEs and the associated flare activity. Here, we provide
results from data-driven 3D modeling of the coronal magnetic field,
capturing the recurrent formation and eruption of energized structures
in support of the collisional shearing process. We discuss our results
in relation to flare and eruptive activity.
Title: Homologous Explosive Activity Driven By The Collisional
Shearing Mechanism
Authors: Chintzoglou, G.; Cheung, M. C.
Bibcode: 2021AAS...23812709C
Altcode:
Active Regions (ARs) in their emergence phase are known to be more flare
productive and eruptive than ARs in their decay phase. In this work,
we focus on complex emerging ARs composed of multiple bipoles. Due
to the compact clustering of the different emerging bipoles within
such complex multipolar ARs, collision and shearing between opposite
non-conjugated polarities produce "collisional polarity inversion lines"
(cPILs) and drive rapid photospheric cancellation of magnetic flux. The
strength and the duration of the collision, shearing, and cancellation
are defined by the natural separation of the conjugated polarities
during the emergence phase of each bipole in the AR. This mechanism
is called "collisional shearing". In Chintzoglou et al (2019), it
was demonstrated that collisional shearing occurred in two emerging
flare- and CME-productive ARs (NOAA AR11158 and AR12017) by measuring
significant amounts of magnetic flux canceling at the cPIL. This
finding supported the formation and energization of magnetic flux ropes
before their eruption as CMEs and the associated flare activity. Here,
we provide additional evidence from HINODE observations that confirm
the occurrence of strong magnetic cancellation at the cPIL of these
ARs. In addition, we provide results from data-driven 3D modeling of the
coronal magnetic field, capturing the recurrent formation and eruption
of energized structures during the collisional shearing process. We
discuss our results in relation to flare and eruptive activity.
Title: Decay Index Profile and Coronal Mass Ejection Speed
Authors: Kliem, Bernhard; Zhang, Jie; Torok, Tibor; Chintzoglou,
Georgios
Bibcode: 2021cosp...43E.997K
Altcode:
The velocity of coronal mass ejections (CMEs) is one of the primary
parameters determining their potential geoeffectiveness. A great
majority of very fast CMEs receive their main acceleration already
in the corona. We study the magnetic source region structure for
a complete sample of 15 very fast CMEs (v > 1500 km/s) during
2000--2006, originating within 30 deg from central meridian. We find
a correlation between CME speed and the decay index profile of the
coronal field estimated by a PFSS extrapolation. The correlation
is considerably weaker for an extended sample that includes slower
CMEs. We also study how the decay index profile is related to the
structure of the photospheric field distribution. This is complemented
by a parametric simulation study of flux-rope eruptions using the
analytic Titov-D\'emoulin active-region model for simple bipolar and
quadrupolar source regions. The simulations provide simple relationships
between the photospheric field distribution and the coronal decay index
profile. They also help identifying source regions which are likely to
produce slow CMEs only, thus improving the correlation for the extended
CME sample. Very fast, moderate-velocity, and even confined eruptions
are found, and the conditions for their occurrence are quantified.
Title: The Action of the Collisional Shearing Mechanism in Complex
Emerging and Developing Active Regions Revealed by SDO and Hinode
Observations and Data-Driven Modeling
Authors: Chintzoglou, Georgios; Cheung, Mark
Bibcode: 2021cosp...43E.991C
Altcode:
Active Regions (ARs) in their emergence phase are known to be more flare
productive and eruptive than ARs in their decay phase. In this work,
we focus on complex emerging ARs composed of multiple bipoles. Due
to the compact clustering of the different emerging bipoles within
such complex multipolar ARs, collision and shearing between opposite
non-conjugated polarities produces "collisional polarity inversion
lines" (cPILs) and drives rapid photospheric cancellation of magnetic
flux. The strength and the duration of the collision, shearing, and
cancellation is defined by the natural separation of the conjugated
polarities during the emergence phase of each bipole in the AR. This
mechanism is called "collisional shearing". In Chintzoglou et al (2019),
it was demonstrated that collisional shearing occurred in two emerging
flare- and CME-productive ARs (NOAA AR11158 and AR12017) by measuring
significant amounts of magnetic flux cancelling at the cPIL. This
finding supported the formation and energization of magnetic flux ropes
before their eruption as CMEs and the associated flare activity. Here,
we provide additional evidence from HINODE observations that confirm
the occurrence of strong magnetic cancellation at the cPIL of these
ARs. In addition, we provide results from data-driven 3D modeling of
the coronal magnetic field, capturing the formation and evolution of
the energized structures during the collisional shearing process. We
discuss our results in relation to flare and eruptive activity.
Title: ALMA and IRIS Observations of the Solar
Chromosphere. II. Structure and Dynamics of Chromospheric Plages
Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora,
Juan; Hansteen, Viggo; de la Cruz Rodríguez, Jaime; Szydlarski,
Mikolaj; Jafarzadeh, Shahin; Wedemeyer, Sven; Bastian, Timothy S.;
Sainz Dalda, Alberto
Bibcode: 2021ApJ...906...83C
Altcode: 2020arXiv201205970C
We propose and employ a novel empirical method for determining
chromospheric plage regions, which seems to better isolate a plage from
its surrounding regions than other methods commonly used. We caution
that isolating a plage from its immediate surroundings must be done
with care in order to successfully mitigate statistical biases that,
for instance, can impact quantitative comparisons between different
chromospheric observables. Using this methodology, our analysis suggests
that λ = 1.25 mm free-free emission in plage regions observed with
the Atacama Large Millimeter/submillimeter Array (ALMA)/Band6 may
not form in the low chromosphere as previously thought, but rather
in the upper chromospheric parts of dynamic plage features (such as
spicules and other bright structures), i.e., near geometric heights
of transition-region temperatures. We investigate the high degree of
similarity between chromospheric plage features observed in ALMA/Band6
(at 1.25 mm wavelengths) and the Interface Region Imaging Spectrograph
(IRIS)/Si IV at 1393 Å. We also show that IRIS/Mg II h and k are
not as well correlated with ALMA/Band6 as was previously thought,
and we discuss discrepancies with previous works. Lastly, we report
indications of chromospheric heating due to propagating shocks supported
by the ALMA/Band6 observations.
Title: Flare simulations with the MURaM radiative MHD code
Authors: Rempel, Matthias; Cheung, Mark; Chintzoglou, Georgios
Bibcode: 2021cosp...43E1772R
Altcode:
Over the past few years the MURaM radiative MHD code was expanded
for its capability to simulate the coupled solar atmosphere from the
upper convection zone into the lower solar corona. The code includes
the essential physics to synthesize thermal emission ranging from
the visible spectrum in the photosphere to EUV and soft X-ray from
transition region and corona. A more sophisticated treatment of the
chromosphere is currently under development. After a brief review of
the code's capabilities and limitations we present a new setup that
allows to create collisional polarity inversion lines (cPILs) and study
the coronal response including flares. In the setup we start with a
bipolar sunspot configuration and set the spots on collision course
by imposing the appropriate velocity field at the footpoints in the
subphotospheric boundary. We vary parameters such as the initial spot
separation, collision speed and collision distance. While all setups
lead to the formation of a sigmoid structure, only the cases with a
close passing of the spots cause flares and mass eruptions. The energy
release is in the $1-2\times 10^{31}$ erg range, putting the simulated
flares into the upper C to lower M-class range. While the case with the
more distant passing of the spots does not lead to a flare, the corona
is nonetheless substantially heated, suggesting non-eruptive energy
release mechanisms. We discuss the applicability/implications of our
setups for investigating the way cPILs form and produce eruptions and
present preliminary results.
Title: ALMA and IRIS Observations of the Solar Chromosphere. I. An
On-disk Type II Spicule
Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora,
Juan; Hansteen, Viggo; de la Cruz Rodríguez, Jaime; Szydlarski,
Mikolaj; Jafarzadeh, Shahin; Wedemeyer, Sven; Bastian, Timothy S.;
Sainz Dalda, Alberto
Bibcode: 2021ApJ...906...82C
Altcode: 2020arXiv200512717C
We present observations of the solar chromosphere obtained
simultaneously with the Atacama Large Millimeter/submillimeter Array
(ALMA) and the Interface Region Imaging Spectrograph. The observatories
targeted a chromospheric plage region of which the spatial distribution
(split between strongly and weakly magnetized regions) allowed the
study of linear-like structures in isolation, free of contamination
from background emission. Using these observations in conjunction with
a radiative magnetohydrodynamic 2.5D model covering the upper convection
zone all the way to the corona that considers nonequilibrium ionization
effects, we report the detection of an on-disk chromospheric spicule
with ALMA and confirm its multithermal nature.
Title: aiapy
Authors: Barnes, W. T.; Cheung, M. C. M; Bobra, M. G.; Boerner, P. F.;
Chintzoglou, G.; Leonard, D.; Mumford, S. J.; Padmanabhan, N.; Shih,
A. Y.; Shirman, N.; Stansby, D.; Wright, P. J.
Bibcode: 2020zndo...4315741B
Altcode:
aiapy is a Python package for analyzing data from the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory
spacecraft.
Title: Flare Simulations with the MURaM Radiative MHD Code
Authors: Rempel, M.; Chintzoglou, G.; Cheung, C. M. M.
Bibcode: 2020AGUFMSH0500004R
Altcode:
No abstract at ADS
Title: ALMA and IRIS Observations Highlighting the Dynamics and
Structure of Chromospheric Plage
Authors: Chintzoglou, G.; De Pontieu, B.; Martinez-Sykora, J.;
Hansteen, V. H.; de la Cruz Rodriguez, J.; Szydlarski, M.; Jafarzadeh,
S.; Wedemeyer, S.; Bastian, T.; Sainz Dalda, A.
Bibcode: 2020AGUFMSH0010009C
Altcode:
We present observations of the solar chromosphere obtained
simultaneously with the Atacama Large Millimeter/submillimeter Array
(ALMA) and the Interface Region Imaging Spectrograph (IRIS). The
observatories targeted a chromospheric plage region of which the spatial
distribution (split between strongly and weakly magnetized regions)
allowed the study of linear-like structures in isolation, free of
contamination from background emission. Using these observations
in conjunction with a radiative magnetohydrodynamic 2.5D model
covering the upper convection zone all the way to the corona
that considers non-equilibrium ionization effects, we report the
detection of an on-disk chromospheric spicule with ALMA and confirm
its multithermal nature. In addition, we discuss the strikingly high
degree of similarity between chromospheric plage features observed
in ALMA/Band6 and IRIS/\ion{Si}{4} (also reproduced in our model)
suggesting that ALMA/Band6 does not observe in the low chromosphere as
previously thought but rather observes the upper chromospheric parts
of structures such as spicules and other bright structures above plage
at geometric heights near transition region temperatures. We also show
that IRIS/\ion{Mg}{2} is not as well correlated with ALMA/Band6 as was
previously thought. For these comparisons, we propose and employ a novel
empirical method for the determination of plage regions, which seems
to better isolate plage from its surrounding regions as compared to
other methods commonly used. We caution that isolating plage from its
immediate surroundings must be done with care to mitigate statistical
bias in quantitative comparisons between different chromospheric
observables. Lastly, we report indications for chromospheric heating
due to traveling shocks supported by the ALMA/Band6 observations.
Title: A Mission Concept for a Solar Observatory in a Highly-Inclined
Heliocentric Orbit - Demystifying the Magnetic Nature and Activity
of our Star
Authors: Chintzoglou, G.; Anderson, T.; Akhavan-Tafti, M.; Chartier,
A.; Duncan, J. M.; Farrish, A.; Fritz, B. A.; Kjellstrand, C. B.;
Maruca, B.; McGranaghan, R. M.; Meng, X.; Newheart, A.; Perea, R. S.;
Probst, A.; Rankin, K.; Robertson, E.; Thaller, S.; Young, S. A. Q.;
Lowes, L. L.
Bibcode: 2020AGUFMSH0110006C
Altcode:
The 2013 Heliophysics Decadal Survey recommended an off-the-ecliptic
solar/heliospheric mission to improve our understanding of the Sun by
observing the magnetic field, meridional flows, solar irradiance,
and their dynamic activity, in the lower atmosphere corona and
inner heliosphere from the polar regions. This is necessary in
order to address the Decadal Survey's Solar and Heliospheric Physics
challenges: (1) to determine the origins of the Sun's activity and
predict the variations in the space environment; and, (2) to discover
and characterize fundamental processes that occur both within the
heliosphere and throughout the universe. Here, we provide an initial
mission concept design for a high-inclination Sun-orbiting observatory
formulated by the 2020 NASA Heliophysics Mission Design School. By
expanding our surveillance of the solar surface, this mission will
permit, for the first time, the mapping of the magnetic fields around
the Sun and its poles from a highly-inclined heliocentric orbit. With a
comprehensive instrument suite and a unique vantage point, this mission
will answer a large number of open questions studying the solar dynamo
and characterize the internal differential rotation profile across
all latitudes; measure the photospheric polar magnetic field and its
reversal; uncover the physics of the birth, evolution, and 3D structure
of solar active regions and the formation of pre-eruptive structures;
determine the global structure and evolution of the solar corona;
and will monitor solar transients and their interaction with the
solar wind. By measuring the polar field strength with in-situ and
remote sensing, this mission will constrain evolutionary models of the
global coronal and inner-heliospheric magnetic field, in addition to
providing critical input for dynamic models of the structure of the
source region and the propagation of coronal mass ejections, further
enabling the coupling of different MHD models to study the Sun-Earth
connection. With its unique vantage point, this spacecraft will fill in
the gaps in our current knowledge of the Solar-dynamo, magnetic fields,
and space weather fulfilling multiple Heliophysics science challenges.
Title: aiapy: A Python Package for Analyzing Solar EUV Image Data
from AIA
Authors: Barnes, W. T.; Cheung, M. C. M; Bobra, M. G.; Boerner, P. F.;
Chintzoglou, G.; Leonard, D.; Mumford, S. J.; Padmanabhan, N.; Shih,
A. Y.; Shirman, N.; Stansby, D.; Wright, P. J.
Bibcode: 2020zndo...4274931B
Altcode:
aiapy is a Python package for analyzing data from the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory
spacecraft.
Title: aiapy: A Python Package for Analyzing Solar EUV Image Data
from AIA
Authors: Barnes, Will; Cheung, Mark; Bobra, Monica; Boerner, Paul;
Chintzoglou, Georgios; Leonard, Drew; Mumford, Stuart; Padmanabhan,
Nicholas; Shih, Albert; Shirman, Nina; Stansby, David; Wright, Paul
Bibcode: 2020JOSS....5.2801B
Altcode:
No abstract at ADS
Title: Decoding the Pre-Eruptive Magnetic Field Configurations of
Coronal Mass Ejections
Authors: Patsourakos, S.; Vourlidas, A.; Török, T.; Kliem, B.;
Antiochos, S. K.; Archontis, V.; Aulanier, G.; Cheng, X.; Chintzoglou,
G.; Georgoulis, M. K.; Green, L. M.; Leake, J. E.; Moore, R.; Nindos,
A.; Syntelis, P.; Yardley, S. L.; Yurchyshyn, V.; Zhang, J.
Bibcode: 2020SSRv..216..131P
Altcode: 2020arXiv201010186P
A clear understanding of the nature of the pre-eruptive magnetic
field configurations of Coronal Mass Ejections (CMEs) is required
for understanding and eventually predicting solar eruptions. Only
two, but seemingly disparate, magnetic configurations are considered
viable; namely, sheared magnetic arcades (SMA) and magnetic flux ropes
(MFR). They can form via three physical mechanisms (flux emergence,
flux cancellation, helicity condensation). Whether the CME culprit
is an SMA or an MFR, however, has been strongly debated for thirty
years. We formed an International Space Science Institute (ISSI) team to
address and resolve this issue and report the outcome here. We review
the status of the field across modeling and observations, identify
the open and closed issues, compile lists of SMA and MFR observables
to be tested against observations and outline research activities
to close the gaps in our current understanding. We propose that the
combination of multi-viewpoint multi-thermal coronal observations
and multi-height vector magnetic field measurements is the optimal
approach for resolving the issue conclusively. We demonstrate the
approach using MHD simulations and synthetic coronal images.
Title: High-resolution observations of the solar photosphere,
chromosphere, and transition region. A database of coordinated IRIS
and SST observations
Authors: Rouppe van der Voort, L. H. M.; De Pontieu, B.; Carlsson,
M.; de la Cruz Rodríguez, J.; Bose, S.; Chintzoglou, G.; Drews, A.;
Froment, C.; Gošić, M.; Graham, D. R.; Hansteen, V. H.; Henriques,
V. M. J.; Jafarzadeh, S.; Joshi, J.; Kleint, L.; Kohutova, P.;
Leifsen, T.; Martínez-Sykora, J.; Nóbrega-Siverio, D.; Ortiz, A.;
Pereira, T. M. D.; Popovas, A.; Quintero Noda, C.; Sainz Dalda, A.;
Scharmer, G. B.; Schmit, D.; Scullion, E.; Skogsrud, H.; Szydlarski,
M.; Timmons, R.; Vissers, G. J. M.; Woods, M. M.; Zacharias, P.
Bibcode: 2020A&A...641A.146R
Altcode: 2020arXiv200514175R
NASA's Interface Region Imaging Spectrograph (IRIS) provides
high-resolution observations of the solar atmosphere through ultraviolet
spectroscopy and imaging. Since the launch of IRIS in June 2013, we
have conducted systematic observation campaigns in coordination with
the Swedish 1 m Solar Telescope (SST) on La Palma. The SST provides
complementary high-resolution observations of the photosphere and
chromosphere. The SST observations include spectropolarimetric imaging
in photospheric Fe I lines and spectrally resolved imaging in the
chromospheric Ca II 8542 Å, Hα, and Ca II K lines. We present
a database of co-aligned IRIS and SST datasets that is open for
analysis to the scientific community. The database covers a variety
of targets including active regions, sunspots, plages, the quiet Sun,
and coronal holes.
Title: aiapy
Authors: Barnes, W. T.; Cheung, M. C. M; Padmanabhan, N.; Chintzoglou,
G.; Mumford, S.; Wright, P. J.; Shih, A. Y.; Bobra, M. G.; Shirman,
N.; Kocher, M.
Bibcode: 2020zndo...4016983B
Altcode:
aiapy is a Python package for analyzing data from the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory
spacecraft.
Title: The Formation Height of Millimeter-wavelength Emission in
the Solar Chromosphere
Authors: Martínez-Sykora, Juan; De Pontieu, Bart; de la Cruz
Rodriguez, Jaime; Chintzoglou, Georgios
Bibcode: 2020ApJ...891L...8M
Altcode: 2020arXiv200110645M
In the past few years, the ALMA radio telescope has become available
for solar observations. ALMA diagnostics of the solar atmosphere are of
high interest because of the theoretically expected linear relationship
between the brightness temperature at millimeter wavelengths and
the local gas temperature in the solar atmosphere. Key for the
interpretation of solar ALMA observations is understanding where in
the solar atmosphere the ALMA emission originates. Recent theoretical
studies have suggested that ALMA bands at 1.2 (band 6) and 3 mm
(band 3) form in the middle and upper chromosphere at significantly
different heights. We study the formation of ALMA diagnostics using
a 2.5D radiative MHD model that includes the effects of ion-neutral
interactions (ambipolar diffusion) and nonequilibrium ionization
of hydrogen and helium. Our results suggest that in active regions
and network regions, observations at both wavelengths most often
originate from similar heights in the upper chromosphere, contrary to
previous results. Nonequilibrium ionization increases the opacity in the
chromosphere so that ALMA mostly observes spicules and fibrils along the
canopy fields. We combine these modeling results with observations from
IRIS, SDO, and ALMA to suggest a new interpretation for the recently
reported "dark chromospheric holes," regions of very low temperatures
in the chromosphere.
Title: The multi-thermal chromosphere. Inversions of ALMA and
IRIS data
Authors: da Silva Santos, J. M.; de la Cruz Rodríguez, J.; Leenaarts,
J.; Chintzoglou, G.; De Pontieu, B.; Wedemeyer, S.; Szydlarski, M.
Bibcode: 2020A&A...634A..56D
Altcode: 2019arXiv191209886D
Context. Numerical simulations of the solar chromosphere predict a
diverse thermal structure with both hot and cool regions. Observations
of plage regions in particular typically feature broader and brighter
chromospheric lines, which suggests that they are formed in hotter
and denser conditions than in the quiet Sun, but also implies a
nonthermal component whose source is unclear.
Aims: We revisit
the problem of the stratification of temperature and microturbulence
in plage and the quiet Sun, now adding millimeter (mm) continuum
observations provided by the Atacama Large Millimiter Array (ALMA) to
inversions of near-ultraviolet Interface Region Imaging Spectrograph
(IRIS) spectra as a powerful new diagnostic to disentangle the
two parameters. We fit cool chromospheric holes and track the fast
evolution of compact mm brightenings in the plage region.
Methods: We use the STiC nonlocal thermodynamic equilibrium (NLTE)
inversion code to simultaneously fit real ultraviolet and mm spectra
in order to infer the thermodynamic parameters of the plasma.
Results: We confirm the anticipated constraining potential of ALMA
in NLTE inversions of the solar chromosphere. We find significant
differences between the inversion results of IRIS data alone compared to
the results of a combination with the mm data: the IRIS+ALMA inversions
have increased contrast and temperature range, and tend to favor lower
values of microturbulence (∼3-6 km s-1 in plage compared
to ∼4-7 km s-1 from IRIS alone) in the chromosphere. The
average brightness temperature of the plage region at 1.25 mm is 8500
K, but the ALMA maps also show much cooler (∼3000 K) and hotter
(∼11 000 K) evolving features partially seen in other diagnostics. To
explain the former, the inversions require the existence of localized
low-temperature regions in the chromosphere where molecules such as CO
could form. The hot features could sustain such high temperatures due to
non-equilibrium hydrogen ionization effects in a shocked chromosphere
- a scenario that is supported by low-frequency shock wave patterns
found in the Mg II lines probed by IRIS.
Title: A comprehensive three-dimensional radiative magnetohydrodynamic
simulation of a solar flare
Authors: Cheung, M. C. M.; Rempel, M.; Chintzoglou, G.; Chen, F.;
Testa, P.; Martínez-Sykora, J.; Sainz Dalda, A.; DeRosa, M. L.;
Malanushenko, A.; Hansteen, V.; De Pontieu, B.; Carlsson, M.; Gudiksen,
B.; McIntosh, S. W.
Bibcode: 2019NatAs...3..160C
Altcode: 2018NatAs...3..160C
Solar and stellar flares are the most intense emitters of X-rays and
extreme ultraviolet radiation in planetary systems1,2. On
the Sun, strong flares are usually found in newly emerging sunspot
regions3. The emergence of these magnetic sunspot groups
leads to the accumulation of magnetic energy in the corona. When
the magnetic field undergoes abrupt relaxation, the energy released
powers coronal mass ejections as well as heating plasma to temperatures
beyond tens of millions of kelvins. While recent work has shed light
on how magnetic energy and twist accumulate in the corona4
and on how three-dimensional magnetic reconnection allows for rapid
energy release5,6, a self-consistent model capturing how
such magnetic changes translate into observable diagnostics has remained
elusive. Here, we present a comprehensive radiative magnetohydrodynamics
simulation of a solar flare capturing the process from emergence to
eruption. The simulation has sufficient realism for the synthesis of
remote sensing measurements to compare with observations at visible,
ultraviolet and X-ray wavelengths. This unifying model allows us to
explain a number of well-known features of solar flares7,
including the time profile of the X-ray flux during flares, origin
and temporal evolution of chromospheric evaporation and condensation,
and sweeping of flare ribbons in the lower atmosphere. Furthermore,
the model reproduces the apparent non-thermal shape of coronal X-ray
spectra, which is the result of the superposition of multi-component
super-hot plasmas8 up to and beyond 100 million K.
Title: Radiative MHD Simulation of a Solar Flare
Authors: Cheung, Mark; Rempel, Matthias D.; Chintzoglou, Georgios;
Chen, Feng; Testa, Paola; Martinez-Sykora, Juan; Sainz Dalda, Alberto;
DeRosa, Marc L.; Malanushenko, Anna; Hansteen, Viggo; Carlsson, Mats;
De Pontieu, Bart; Gudiksen, Boris; McIntosh, Scott W.
Bibcode: 2019AAS...23431005C
Altcode:
We present a radiative MHD simulation of a solar flare. The
computational domain captures the near-surface layers of the convection
zone and overlying atmosphere. Inspired by the observed evolution of
NOAA Active Region (AR) 12017, a parasitic bipolar region is imposed
to emerge in the vicinity of a pre-existing sunspot. The emergence of
twisted magnetic flux generates shear flows that create a pre-existing
flux rope underneath the canopy field of the sunspot. Following erosion
of the overlying bootstrapping field, the flux rope erupts. Rapid
release of magnetic energy results in multi-wavelength synthetic
observables (including X-ray spectra, narrowband EUV images, Doppler
shifts of EUV lines) that are consistent with flare observations. This
works suggests the super-position of multi-thermal, superhot (up
to 100 MK) plasma may be partially responsible for the apparent
non-thermal shape of coronal X-ray sources in flares. Implications
for remote sensing observations of other astrophysical objects is also
discussed. This work is an important stepping stone toward high-fidelity
data-driven MHD models.
Title: Measuring and Characterizing the Importance of Magnetic Flux
Cancellation in Solar Active Regions during their Emergence Phase
Authors: Chintzoglou, Georgios; Cheung, Mark
Bibcode: 2019AAS...23440202C
Altcode:
Active Regions (ARs) in their emergence phase are known to be more flare
productive and eruptive than ARs in their decay phase. For decaying ARs,
the flaring and eruptive activity is thought to be a consequence of
the formation of magnetic flux ropes through photospheric magnetic flux
cancellation, often occurring at the internal polarity inversion line
(PIL) of the AR. Typically, during the AR decay phase, flux cancellation
manifests itself by a clear decay of the total unsigned magnetic flux,
sometimes preceding and even accompanying the flaring and eruptive
activity. In emerging ARs, however, no cancellation can be seen in the
total unsigned magnetic flux owing to sustained flux emergence. In this
work we focus on complex emerging ARs composed of multiple bipoles. Due
to the compact clustering of the different bipoles within such complex
multipolar ARs, collision and shearing between opposite nonconjugated
polarities drives rapid photospheric cancellation. This mechanism
is called collisional shearing. In Chintzoglou et al (2019), it was
demonstrated that collisional shearing occurred in two emerging flare
and CME productive ARs (NOAA AR11158 and AR12017) and a significant
amount of cancelled flux was measured by applying the conjugate
flux deficit method (Chintzoglou et al 2019). Here, we employ a new
methodology based on a novel electric field inversion method and we
calculate the time evolution of magnetic flux through Faraday's law
at the internal PIL of emerging ARs. We compare this methodology with
the conjugate flux deficit method on magnetogram series of synthetic
and observed emerging ARs and discuss our results in relation to flare
and eruptive activity.
Title: Sheared Magnetic Arcades and the Pre-eruptive Magnetic
Configuration of Coronal Mass Ejections: Diagnostics, Challenges
and Future Observables
Authors: Patsourakos, Spiros; Vourlidas, A.; Anthiochos, S. K.;
Archontis, V.; Aulanier, G.; Cheng, X.; Chintzoglou, G.; Georgoulis,
M. K.; Green, L. M.; Kliem, B.; Leake, J.; Moore, R. L.; Nindos, A.;
Syntelis, P.; Torok, T.; Yardley, S. L.; Yurchyshyn, V.; Zhang, J.
Bibcode: 2019shin.confE.194P
Altcode:
Our thinking about the pre-eruptive magnetic configuration of Coronal
Mass Ejections has been effectively dichotomized into two opposing
and often fiercely contested views: namely, sheared magnetic arcades
and magnetic flux ropes. Finding a solution to this issue will have
important implications for our understanding of CME initiation. We
first discuss the very value of embarking into the arcade vs. flux rope
dilemma and illustrate the corresponding challenges and difficulties to
address it. Next, we are compiling several observational diagnostics of
pre-eruptive sheared magnetic arcades stemming from theory/modeling,
discuss their merits, and highlight potential ambiguities that could
arise in their interpretation. We finally conclude with a discussion
of possible new observables, in the frame of upcoming or proposed
instrumentation, that could help to circumvent the issues we are
currently facing.
Title: Detection of Strong Photospheric Downflows Accompanying
Magnetic Cancellation in Collisional Polarity Inversion Lines of
Flare- and CME-Productive Active Regions
Authors: Chintzoglou, Georgios; Cheung, Mark C. M.
Bibcode: 2019shin.confE..38C
Altcode:
Individual events of cancellation of small magnetic features in
the quiet Sun seen in photospheric magnetogram observations can be
attributed to either the submergence of Omega-loops or the emergence
of U-loop structures through the solar photosphere. As the opposite
polarities of these small features converge and cancel, they form
very compact polarity inversion lines (PILs). In Active Regions (ARs)
cancellation of such small opposite polarity features is typically
seen to occur during the decay phase of ARs. However, compact PILs can
form earlier in an AR’s lifetime, e.g. in complex and developing
multipolar ARs, as a result of the collision between at least two
emerging flux tubes nested within the same AR. This process is called
collisional shearing, as to emphasize that the shearing and flux
cancellation develop owing to the collision. High spatial and temporal
resolution observations from the Solar Dynamics Observatory for two
emerging ARs, AR 11158 and AR 12017, show the continuous cancellation
at the collisional PIL for as long as the collision persists. The flux
cancellation is accompanied by a succession of solar flares and CMEs,
products of magnetic reconnection along the collisional PIL. Here,
we use high spatial resolution magneto grams and Doppler observations
from HINODE/SP to confirm that the cancellation is consistent with
the submergence of Omega-loops, resulting to a twisted magnetic flux
rope in the corona. Such confirmation with HINODE/SP is important
to elucidate the role of the collisional shearing process on the
formation of magnetic flux ropes. This finding has implications in
our understanding of extreme solar activity.
Title: The Origin of Major Solar Activity: Collisional Shearing
between Nonconjugated Polarities of Multiple Bipoles Emerging within
Active Regions
Authors: Chintzoglou, Georgios; Zhang, Jie; Cheung, Mark C. M.;
Kazachenko, Maria
Bibcode: 2019ApJ...871...67C
Altcode: 2018arXiv181102186C
Active regions (ARs) that exhibit compact polarity inversion
lines (PILs) are known to be very flare productive. However, the
physical mechanisms behind this statistical inference have not been
demonstrated conclusively. We show that such PILs can occur owing to
the collision between two emerging flux tubes nested within the same
AR. In such multipolar ARs, the flux tubes may emerge simultaneously
or sequentially, each initially producing a bipolar magnetic region
(BMR) at the surface. During each flux tube’s emergence phase, the
magnetic polarities can migrate such that opposite polarities belonging
to different BMRs collide, resulting in shearing and cancellation of
magnetic flux. We name this process “collisional shearing” to
emphasize that the shearing and flux cancellation develop owing to
the collision. Collisional shearing is a process different from the
known concept of flux cancellation occurring between polarities of a
single bipole, a process that has been commonly used in many numerical
models. High spatial and temporal resolution observations from the Solar
Dynamics Observatory for two emerging ARs, AR 11158 and AR 12017, show
the continuous cancellation of up to 40% of the unsigned magnetic flux
of the smallest BMR, which occurs at the collisional PIL for as long
as the collision persists. The flux cancellation is accompanied by a
succession of solar flares and CMEs, products of magnetic reconnection
along the collisional PIL. Our results suggest that the quantification
of magnetic cancellation driven by collisional shearing needs to be
taken into consideration in order to improve the prediction of solar
energetic events and space weather.
Title: The Origin of Major Solar Activity - Collisional Shearing
Between Nonconjugated Polarities of Different Bipoles Nested Within
Active Regions
Authors: Chintzoglou, Georgios; Zhang, Jie; Cheung, Mark C. M.;
Kazachenko, Maria
Bibcode: 2018csc..confE..18C
Altcode:
Active Regions (ARs) that exhibit compact Polarity Inversion
Lines (PILs) are known to be very flare-productive. However, the
physical mechanisms behind this statistical inference have not been
demonstrated conclusively. We show that such PILs can occur due to
the collision between two emerging flux tubes nested within the same
AR. In such multipolar ARs, the flux tubes may emerge simultaneously
or sequentially, each initially producing a bipolar magnetic region
(BMR) at the surface. During each flux tube's emergence phase, the
magnetic polarities can migrate such that opposite polarities belonging
to different BMRs collide, resulting in shearing and cancellation
of magnetic flux. We name this process "collisional shearing" to
emphasize that the shearing and flux cancellation develops due to
the collision. Collisional shearing is a process different from the
known concept of flux cancellation occurring between polarities of a
single bipole, a process that has been commonly used in many numerical
models. High spatial and temporal resolution observations from the
Solar Dynamics Observatory for two emerging ARs, AR11158 and AR12017,
show the continuous cancellation of up to 25% of the unsigned magnetic
flux of the smallest BMR, which occurs at the collisional PIL for as
long as the collision persists. The flux cancellation is accompanied by
a succession of solar flares and CMEs, products of magnetic reconnection
along the collisional PIL. Our results suggest that the quantification
of magnetic cancellation driven by collisional shearing needs to be
taken into consideration in order to improve the prediction of solar
energetic events and space weather.
Title: The Origin of Major Solar Activity - Magnetic Flux Cancellation
due to Collisional Shearing Between Polarities of Different Bipoles
Nested Within Active Regions
Authors: Chintzoglou, Georgios; Zhang, Jie; Cheung, Mark C. M.;
Kazachenko, Maria
Bibcode: 2018shin.confE.146C
Altcode:
Active Regions (ARs) that exhibit compact Polarity Inversion Lines
(PILs) are known to be very flare-productive. However, the basis for
this statistical inference has not been demonstrated conclusively. We
show that such PILs can occur due to the collision between two emerging
flux tubes nested within the same AR. In such multipolar ARs, the
flux tubes may emerge simultaneously or sequentially, each initially
producing a bipolar magnetic region (BMR) at the surface. During each
flux tube's emergence phase, the magnetic polarities can migrate in
such ways that opposite polarities belonging to different BMRs collide,
resulting in shearing and cancellation of magnetic flux. We name this
process 'collisional shearing' to emphasize that the shearing and flux
cancellation develops due to the collision. Collisional shearing is a
process different from the known concept of flux cancellation occurring
between conjugated polarities of a single bipole, a process that has
been commonly used in many numerical models. High spatial and temporal
resolution observations from the Solar Dynamics Observatory for two
emerging ARs, AR11158 and AR12017, show the continuous cancellation of
up to 25% of the unsigned magnetic flux, which occurs at the collisional
PIL for as long as the collision persists. The flux cancellation is
accompanied by a succession of solar flares and CMEs, products of
magnetic reconnection along the collisional PIL. Our results suggest
that the quantification of magnetic cancellation driven by collisional
shearing needs to be taken into consideration for the improvement of
predicting solar energetic events and space weather.
Title: The Origin of Major Solar Activity - Collisional Shearing
Between Nonconjugated Polarities in Solar Active Regions
Authors: Chintzoglou, Georgios; Zhang, Jie
Bibcode: 2018cosp...42E.636C
Altcode:
We present observations suggestive of a new scenario for
the origin of activity in solar Active Regions (ARs). ARs that
exhibit compact Polarity Inversion Lines (PILs) are known to be very
flare-productive. However, the basis for this statistical inference has
not been demonstrated conclusively. We show that such PILs can occur due
to the collision between two emerging flux tubes within the same AR. The
flux tubes may emerge simultaneously or sequentially, initially each
producing two opposite conjugated polarities at the surface. The proper
motions of the polarities lead the nonconjugated opposite polarities
into a collision course, producing shearing and cancellation of opposite
flux. We name this process "collisional shearing" to emphasize that
the shearing develops due to the collision. Collisional shearing is
a process different from the concept of flux cancellation occurring
between conjugated polarities of a single emerging flux tube, a process
that has been commonly used in many numerical models. High spatial and
temporal resolution observations from the Solar Dynamics Observatory
for two emerging ARs show the continuous cancellation of up to 20%
of their unsigned magnetic flux, which occurs at the collisional
PIL for as long as the sunspot collision persists. The cancellation
is accompanied by a succession of solar flares and CMEs, products of
magnetic flux cancellation along the contact layer. Our results strongly
suggest that magnetic cancellation driven by collisional shearing is
a primary process that needs to be taken into consideration for the
improvement of predicting solar energetic events and space weather.
Title: Compound Solar Eruptions and the Causes
Authors: Zhang, Jie; Chintzoglou, Georgios; Dhakal, Suman
Bibcode: 2018cosp...42E3830Z
Altcode:
A compound solar eruption is a phenomenon of successive eruptions of
two or more magnetic structures within a short period of time. The
eruption of one magnetic structure may affect the other one through
the interconnection of magnetic field in the corona. This is in
contrast of singular eruptions, the concern of most theoretical and
numerical models of solar eruptions. In this presentation, we will
report a detailed study of the compound eruption occurred on 2012
March 10 from NOAA AR 11429. The eruption produced a GOES M8.4 flare
that contained two distinct peaks with a separation of 12 minutes
during the impulsive phase of the flare. The data from SDO, STEREO-A
and GOES help identify that the two peaks are caused by eruption of
two pre-existing magnetic flux bundles lying along a same polarity
inversion line. The stereoscopic observations of pre-existing filaments
show that these flux bundles are lying one above the other, separated
by 12 Mm in height, in a so-called ``double-decker" configuration. The
high-lying flux bundle became unstable and erupted first, showing as a
high-temperature hot channel in EUV wavelengths. About 12 minutes later,
the low-lying flux bundle also started to erupt and moved at a faster
speed. The two erupting flux bundles interacted with each other and
appeared as a single coronal mass ejection in white-light coronagraph
images in the outer corona. The "double-decker" configuration is likely
to be caused by strong shearing motion and fast flux cancellation along
a strong-gradient polarity inversion line. The successive eruption of
two separate but coupled magnetic flux bundles, possibly in the form of
magnetic flux ropes, lead to the compound solar eruption. The study of
the compound eruption provides us a unique opportunity of revealing the
formation process of erupting structures and the initiation mechanism
of solar eruptions in general.
Title: A Study of a Compound Solar Eruption with Two Consecutive
Erupting Magnetic Structures
Authors: Dhakal, Suman K.; Chintzoglou, Georgios; Zhang, Jie
Bibcode: 2018ApJ...860...35D
Altcode: 2018arXiv180700206D
We report a study of a compound solar eruption that was associated with
two consecutively erupting magnetic structures and correspondingly
two distinct peaks, during impulsive phase, of an M-class flare
(M8.5). Simultaneous multi-viewpoint observations from SDO, GOES
and STEREO-A show that this compound eruption originated from two
pre-existing sigmoidal magnetic structures lying along the same polarity
inversion line. Observations of the associated pre-existing filaments
further show that these magnetic structures are lying one on top of the
other, separated by 12 Mm in height, in a so-called “double-decker”
configuration. The high-lying magnetic structure became unstable and
erupted first, appearing as an expanding hot channel seen at extreme
ultraviolet wavelengths. About 12 minutes later, the low-lying structure
also started to erupt and moved at an even faster speed compared to the
high-lying one. As a result, the two erupting structures interacted and
merged with each other, appearing as a single coronal mass ejection in
the outer corona. We find that the double-decker configuration is likely
caused by the persistent shearing motion and flux cancellation along the
source active region’s strong-gradient polarity inversion line. The
successive destabilization of these two separate but closely spaced
magnetic structures, possibly in the form of magnetic flux ropes, led to
a compound solar eruption. The study of the compound eruption provides
a unique opportunity to reveal the formation process, initiation,
and evolution of complex eruptive structures in solar active regions.
Title: Erratum: “A First Comparison of Millimeter Continuum and
Mg II Ultraviolet Line Emission from the Solar Chromosphere”
(2017, ApJL,
845, L19)
Authors: Bastian, T. S.; Chintzoglou, G.; De Pontieu, B.; Shimojo,
M.; Schmit, D.; Leenaarts, J.; Loukitcheva, M.
Bibcode: 2018ApJ...860L..16B
Altcode:
No abstract at ADS
Title: Bridging the Gap: Capturing the Lyα Counterpart of a Type-II
Spicule and Its Heating Evolution with VAULT2.0 and IRIS Observations
Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora,
Juan; Pereira, Tiago M. D.; Vourlidas, Angelos; Tun Beltran, Samuel
Bibcode: 2018ApJ...857...73C
Altcode: 2018arXiv180303405C
We present results from an observing campaign in support of the
VAULT2.0 sounding rocket launch on 2014 September 30. VAULT2.0 is a Lyα
(1216 Å) spectroheliograph capable of providing spectroheliograms at
high cadence. Lyα observations are highly complementary to the IRIS
observations of the upper chromosphere and the low transition region
(TR) but have previously been unavailable. The VAULT2.0 data provide new
constraints on upper-chromospheric conditions for numerical models. The
observing campaign was closely coordinated with the IRIS mission. Taking
advantage of this simultaneous multi-wavelength coverage of target
AR 12172 and by using state-of-the-art radiative-MHD simulations of
spicules, we investigate in detail a type-II spicule associated with
a fast (300 km s-1) network jet recorded in the campaign
observations. Our analysis suggests that spicular material exists
suspended high in the atmosphere but at lower temperatures (seen in
Lyα) until it is heated and becomes visible in TR temperatures as a
network jet. The heating begins lower in the spicule and propagates
upwards as a rapidly propagating thermal front. The front is then
observed as fast, plane-of-the-sky motion typical of a network jet,
but contained inside the pre-existing spicule. This work supports
the idea that the high speeds reported in network jets should not be
taken as real mass upflows but only as apparent speeds of a rapidly
propagating heating front along the pre-existing spicule.
Title: Toward Understanding the 3D Structure and Evolution of Magnetic
Flux Ropes in an Extremely Long Duration Eruptive Flare
Authors: Zhou, Zhenjun; Zhang, Jie; Wang, Yuming; Liu, Rui;
Chintzoglou, Georgios
Bibcode: 2017ApJ...851..133Z
Altcode:
In this work, we analyze the initial eruptive process of an extremely
long duration C7.7-class flare that occurred on 2011 June 21. The flare
had a 2 hr long rise time in soft X-ray emission, which is much longer
than the rise time of most solar flares, including both impulsive and
gradual ones. Combining the facts that the flare occurred near the disk
center as seen by the Solar Dynamic Observatory (SDO) but near the
limb as seen by two Solar Terrestrial Relations Observatory (STEREO)
spacecraft, we are able to track the evolution of the eruption in 3D in
a rare slow-motion manner. The time sequence of the observed large-scale
EUV hot channel structure in the Atmospheric Imaging Assembly (AIA)
high-temperature passbands of 94 and 131 Å clearly shows the process
of how the sigmoid structure prior to the eruption was transformed
into a near-potential post-eruption loop arcade. We believe that the
observed sigmoid represents the structure of a twisted magnetic flux
rope (MFR), which has reached a height of about 60 Mm at the onset of
the eruption. We argue that the onset of the flare precursor phase is
likely triggered by the loss of the magnetohydrodynamic equilibrium of
a preexisting MFR, which leads to the slow rise of the flux rope. The
rising motion of the flux rope leads to the formation of a vertical
current sheet underneath, triggering the fast magnetic reconnection
that in turn leads to the main phase of the flare and fast acceleration
of the flux rope.
Title: Observations and Modeling of Transition Region and Coronal
Heating Associated with Spicules
Authors: De Pontieu, B.; Martinez-Sykora, J.; De Moortel, I.;
Chintzoglou, G.; McIntosh, S. W.
Bibcode: 2017AGUFMSH43A2793D
Altcode:
Spicules have been proposed as significant contributorsto the coronal
energy and mass balance. While previous observationshave provided
a glimpse of short-lived transient brightenings in thecorona that
are associated with spicules, these observations have beencontested
and are the subject of a vigorous debate both on the modelingand
the observational side so that it remains unclear whether plasmais
heated to coronal temperatures in association with spicules. We use
high-resolution observations of the chromosphere and transition region
with the Interface Region Imaging Spectrograph (IRIS) and ofthe corona
with the Atmospheric Imaging Assembly (AIA) onboard theSolar Dynamics
Observatory (SDO) to show evidence of the formation of coronal
structures as a result of spicular mass ejections andheating of
plasma to transition region and coronaltemperatures. Our observations
suggest that a significant fraction of the highly dynamic loop fan
environment associated with plage regions may be the result of the
formation of such new coronal strands, a process that previously had
been interpreted as the propagation of transient propagating coronal
disturbances (PCD)s. Our observationsare supported by 2.5D radiative
MHD simulations that show heating tocoronal temperatures in association
with spicules. Our results suggest that heating and strong flows play
an important role in maintaining the substructure of loop fans, in
addition to the waves that permeate this low coronal environment. Our
models also matches observations ofTR counterparts of spicules and
provides an elegant explanation forthe high apparent speeds of these
"network jets".
Title: Bridging the Gap: Capturing the Lyα Counterpart of a Type-II
Spicule and its Heating Evolution with VAULT2.0 and IRIS Campaign
Observations
Authors: Chintzoglou, G.; De Pontieu, B.; Martinez-Sykora, J.; Mendes
Domingos Pereira, T.; Vourlidas, A.; Tun Beltran, S.
Bibcode: 2017AGUFMSH43A2794C
Altcode:
We present the analysis of data from the observing campaign in support
to the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0
is a Lyα (1216 Å) spectroheliograph capable of providing fast
cadence spectroheliograms of high-spectral purity. High resolution
Lyα observations are highly complementary with the IRIS observations
of the upper chromosphere and the low transition region but have
previously been unavailable. The VAULT2.0 data provide critical, new
upper-chromospheric constraints for numerical models. The observing
campaign was closely coordinated with the IRIS mission. Taking
advantage of this simultaneous multi-wavelength coverage of target
AR 12172 and by using state-of-the-art radiative-MHD simulations of
spicules, we are able to perform a detailed investigation of a type-II
spicule associated with a fast apparent network jet recorded in the
campaign observations during the VAULT2.0 flight. Our unique analysis
suggests that spicular material exists suspended in lower temperatures
until it rapidly gets heated and becomes visible in transition-region
temperatures as an apparent network jet.
Title: What Causes the High Apparent Speeds in Chromospheric and
Transition Region Spicules on the Sun?
Authors: De Pontieu, Bart; Martínez-Sykora, Juan; Chintzoglou,
Georgios
Bibcode: 2017ApJ...849L...7D
Altcode: 2017arXiv171006803D
Spicules are the most ubuiquitous type of jets in the solar
atmosphere. The advent of high-resolution imaging and spectroscopy
from the Interface Region Imaging Spectrograph (IRIS) and ground-based
observatories has revealed the presence of very high apparent motions of
order 100-300 km s-1 in spicules, as measured in the plane of
the sky. However, line of sight measurements of such high speeds have
been difficult to obtain, with values deduced from Doppler shifts in
spectral lines typically of order 30-70 km s-1. In this work,
we resolve this long-standing discrepancy using recent 2.5D radiative
MHD simulations. This simulation has revealed a novel driving mechanism
for spicules in which ambipolar diffusion resulting from ion-neutral
interactions plays a key role. In our simulation, we often see that
the upward propagation of magnetic waves and electrical currents
from the low chromosphere into already existing spicules can lead to
rapid heating when the currents are rapidly dissipated by ambipolar
diffusion. The combination of rapid heating and the propagation of these
currents at Alfvénic speeds in excess of 100 km s-1 leads
to the very rapid apparent motions, and often wholesale appearance,
of spicules at chromospheric and transition region temperatures. In
our simulation, the observed fast apparent motions in such jets are
actually a signature of a heating front, and much higher than the
mass flows, which are of order 30-70 km s-1. Our results
can explain the behavior of transition region “network jets” and
the very high apparent speeds reported for some chromospheric spicules.
Title: A First Comparison of Millimeter Continuum and Mg II
Ultraviolet Line Emission from the Solar Chromosphere
Authors: Bastian, T. S.; Chintzoglou, G.; De Pontieu, B.; Shimojo,
M.; Schmit, D.; Leenaarts, J.; Loukitcheva, M.
Bibcode: 2017ApJ...845L..19B
Altcode: 2017arXiv170604532B
We present joint observations of the Sun by the Atacama Large
Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging
Spectrograph (IRIS). Both millimeter/submillimeter-λ continuum emission
and ultraviolet (UV) line emission originate from the solar chromosphere
and both have the potential to serve as powerful and complementary
diagnostics of physical conditions in this enigmatic region of the solar
atmosphere. The observations were made of a solar active region on 2015
December 18 as part of the ALMA science verification effort. A map of
the Sun’s continuum emission was obtained by ALMA at a wavelength of
1.25 mm (239 GHz). A contemporaneous map was obtained by IRIS in the
Mg II h doublet line at 2803.5 Å. While a clear correlation between
the 1.25 mm brightness temperature TB and the Mg II h
line radiation temperature Trad is observed, the slope
is <1, perhaps as a result of the fact that these diagnostics
are sensitive to different parts of the chromosphere and that the
Mg II h line source function includes a scattering component. There
is a significant difference (35%) between the mean TB
(1.25 mm) and mean Trad (Mg II). Partitioning the maps
into “sunspot,” “quiet areas,” and “plage regions” we
find the relation between the IRIS Mg II h line Trad and
the ALMA TB region-dependent. We suggest this may be the
result of regional dependences of the formation heights of the IRIS
and ALMA diagnostics and/or the increased degree of coupling between
the UV source function and the local gas temperature in the hotter,
denser gas in plage regions.
Title: Realistic radiative MHD simulation of a solar flare
Authors: Rempel, Matthias D.; Cheung, Mark; Chintzoglou, Georgios;
Chen, Feng; Testa, Paola; Martinez-Sykora, Juan; Sainz Dalda, Alberto;
DeRosa, Marc L.; Viktorovna Malanushenko, Anna; Hansteen, Viggo H.;
De Pontieu, Bart; Carlsson, Mats; Gudiksen, Boris; McIntosh, Scott W.
Bibcode: 2017SPD....4840001R
Altcode:
We present a recently developed version of the MURaM radiative
MHD code that includes coronal physics in terms of optically thin
radiative loss and field aligned heat conduction. The code employs
the "Boris correction" (semi-relativistic MHD with a reduced speed
of light) and a hyperbolic treatment of heat conduction, which allow
for efficient simulations of the photosphere/corona system by avoiding
the severe time-step constraints arising from Alfven wave propagation
and heat conduction. We demonstrate that this approach can be used
even in dynamic phases such as a flare. We consider a setup in which
a flare is triggered by flux emergence into a pre-existing bipolar
active region. After the coronal energy release, efficient transport
of energy along field lines leads to the formation of flare ribbons
within seconds. In the flare ribbons we find downflows for temperatures
lower than ~5 MK and upflows at higher temperatures. The resulting
soft X-ray emission shows a fast rise and slow decay, reaching a peak
corresponding to a mid C-class flare. The post reconnection energy
release in the corona leads to average particle energies reaching 50
keV (500 MK under the assumption of a thermal plasma). We show that
hard X-ray emission from the corona computed under the assumption of
thermal bremsstrahlung can produce a power-law spectrum due to the
multi-thermal nature of the plasma. The electron energy flux into the
flare ribbons (classic heat conduction with free streaming limit) is
highly inhomogeneous and reaches peak values of about 3x1011
erg/cm2/s in a small fraction of the ribbons, indicating
regions that could potentially produce hard X-ray footpoint sources. We
demonstrate that these findings are robust by comparing simulations
computed with different values of the saturation heat flux as well as
the "reduced speed of light".
Title: 3D Collision of Active Region-Sized Emerging Flux Tubes in
the Solar Convection Zone and its Manifestation in the Photospheric
Surface
Authors: Chintzoglou, Georgios; Cheung, Mark; Rempel, Matthias D.
Bibcode: 2017SPD....4830004C
Altcode:
We present observations obtained with the Solar Dynamics Observatory’s
Helioseismic Magnetic Imager (SDO/HMI) of target NOAA Active Regions
(AR) 12017 and 12644, which initially were comprised of a simple bipole
and later on became quadrupolar via parasitic bipole emergence right
next to their leading polarities. Once these ARs became quadrupolar,
they spewed multiple Coronal Mass Ejections (CMEs) and a multitude
of highly energetic flares (a large number of M class flares). The
proximity of the parasitic bipole to one of the two pre-existing
sunspots forms a compact polarity inversion line (PIL). This type of
quadrupolar ARs are known to be very flare- and CME-productive due
to the continuous interaction of newly emerging non-potential flux
with pre-existing flux in the photosphere. We show that well before
the emergence of the parasitic bipole, the pre-existing polarity
(typically a well-developed sunspot) undergoes interesting precursor
dynamic evolution, namely (a) displacement of pre-existing sunspot’s
position, (b) progressive and significant oblateness of its initially
nearly-circular shape, and (c) opposite polarity enhancement in the
divergent moat flow around the sunspot. We employ high-resolution
radiative-convective 3D MHD simulations of an emerging parasitic bipole
to show that all these activity aspects seen in the photosphere are
associated with the collision of a parasitic bipole with the nearby
pre-existing polarity below the photospheric surface. Given the rich
flare and CME productivity of this class of ARs and the precursor-like
dynamic evolution of the pre-existing polarity, this work presents
the potential for predicting inclement space weather.
Title: Magnetic Flux Rope Shredding By a Hyperbolic Flux Tube:
The Detrimental Effects of Magnetic Topology on Solar Eruptions
Authors: Chintzoglou, Georgios; Vourlidas, Angelos; Savcheva, Antonia;
Tassev, Svetlin; Tun Beltran, Samuel; Stenborg, Guillermo
Bibcode: 2017ApJ...843...93C
Altcode: 2017arXiv170600057C
We present the analysis of an unusual failed eruption captured in high
cadence and in many wavelengths during the observing campaign in support
of the Very high Angular resolution Ultraviolet Telescope (VAULT2.0)
sounding rocket launch. The refurbished VAULT2.0 is a Lyα (λ 1216 Å)
spectroheliograph launched on 2014 September 30. The campaign targeted
active region NOAA AR 12172 and was closely coordinated with the Hinode
and IRIS missions and several ground-based observatories (NSO/IBIS,
SOLIS, and BBSO). A filament eruption accompanied by a low-level
flaring event (at the GOES C-class level) occurred around the VAULT2.0
launch. No coronal mass ejection was observed. The eruption and its
source region, however, were recorded by the campaign instruments in
many atmospheric heights ranging from the photosphere to the corona
in high cadence and spatial resolution. This is a rare occasion
that enabled us to perform a comprehensive investigation on a failed
eruption. We find that a rising Magnetic Flux Rope (MFR)-like structure
was destroyed during its interaction with the ambient magnetic field,
creating downflows of cool plasma and diffuse hot coronal structures
reminiscent of “cusps.” We employ magnetofrictional simulations to
show that the magnetic topology of the ambient field is responsible for
the destruction of the MFR. Our unique observations suggest that the
magnetic topology of the corona is a key ingredient for a successful
eruption.
Title: On the First Eruption of Emerging Active Regions
Authors: Nikou, Eleni; Zhang, Jie; Chintzoglou, Georgios
Bibcode: 2017shin.confE.161N
Altcode:
Using newly emerging active regions during a five year period we
try to examine what triggers solar flares and coronal mass ejections
(CMEs) based on the idea that a simple bipole does not produce any
events. Our list consists of active regions which gave a variety of C,
M or X class flares and/ or CMEs. In this study we focus on the trigger
of M or X class flares and CMEs and also on the time elapsed after the
formation of the active region to the first flare event. In the cases
in which we had no M or X class flares we used the first C class flare,
without taking into account the B class flares. In order to figure out
whether the trigger was flux emergence, flux cancellation or shearing
motions, we use magnetograms taken by the HMI instrument aboard the SDO
spacecraft. Moreover in order to have a better idea of the morphology
of each event, we use EUV images at 131 … taken by the AIA instrument,
aboard the SDO spacecraft, while the flare locations are given by GOES.
Title: Magnetic Source Region Characteristics Influencing the Velocity
of Solar Eruptions in the Corona
Authors: Kliem, B.; Chintzoglou, G.; Torok, T.; Zhang, J.; Downs, C.
Bibcode: 2016AGUFMSH13B2292K
Altcode:
The velocity of coronal mass ejections (CMEs) is one of the primary
parameters determining their potential geoeffectiveness. The great
majority of very fast CMEs receive their main acceleration already in
the corona. We study the magnetic source region structure for a complete
sample of 15 very fast CMEs (v > 1500 km/s) during 2000-2006,
originating within 30 deg from central meridian and find a correlation
between CME speed and the decay index profile of the coronal field
estimated by a PFSS extrapolation. Such a correlation is not found
for a comparison sample of slower CMEs. We also study how the decay
index profile is related to the structure of the photospheric field
distribution. This is complemented by a parametric simulation study
of flux rope eruptions using the analytic Titov-Demoulin active-region
model for simple bipolar and quadrupolar source regions, which provide
simple relationships between the photospheric field distribution and
the coronal decay index profile. Very fast, moderate-velocity, and even
confined eruptions are found. Detailed, data-constrained MHD modeling
of a very fast and a relatively slow CME, including a comparison of
their source region characteristics, will also be presented. Support
by NSF and NASA's LWS program is acknowledged.
Title: An observationally-driven kinetic approach to coronal heating
Authors: Moraitis, K.; Toutountzi, A.; Isliker, H.; Georgoulis, M.;
Vlahos, L.; Chintzoglou, G.
Bibcode: 2016A&A...596A..56M
Altcode: 2016arXiv160307129M; 2016arXiv160307129T
Aims: Coronal heating through the explosive release of magnetic
energy remains an open problem in solar physics. Recent hydrodynamical
models attempt an investigation by placing swarms of "nanoflares" at
random sites and times in modeled one-dimensional coronal loops. We
investigate the problem in three dimensions, using extrapolated coronal
magnetic fields of observed solar active regions.
Methods: We
applied a nonlinear force-free field extrapolation above an observed
photospheric magnetogram of NOAA active region (AR) 11 158. We then
determined the locations, energy contents, and volumes of "unstable"
areas, namely areas prone to releasing magnetic energy due to locally
accumulated electric current density. Statistical distributions of
these volumes and their fractal dimension are inferred, investigating
also their dependence on spatial resolution. Further adopting a
simple resistivity model, we inferred the properties of the fractally
distributed electric fields in these volumes. Next, we monitored the
evolution of 105 particles (electrons and ions) obeying
an initial Maxwellian distribution with a temperature of 10 eV,
by following their trajectories and energization when subjected
to the resulting electric fields. For computational convenience,
the length element of the magnetic-field extrapolation is 1 arcsec,
or 725 km, much coarser than the particles' collisional mean free
path in the low corona (0.1-1 km).
Results: The presence of
collisions traps the bulk of the plasma around the unstable volumes,
or current sheets (UCS), with only a tail of the distribution gaining
substantial energy. Assuming that the distance between UCS is similar
to the collisional mean free path we find that the low active-region
corona is heated to 100-200 eV, corresponding to temperatures exceeding
2 MK, within tens of seconds for electrons and thousands of seconds for
ions.
Conclusions: Fractally distributed, nanoflare-triggening
fragmented UCS in the active-region corona can heat electrons and ions
with minor enhancements of the local resistivity. This statistical
result is independent from the nature of the extrapolation and the
spatial resolution of the modeled active-region corona. This finding
should be coupled with a complete plasma treatment to determine whether
a quasi-steady temperature similar to that of the ambient corona can be
maintained, either via a kinetic or via a hybrid, kinetic and fluid,
plasma treatment. The finding can also be extended to the quiet solar
corona, provided that the currently undetected nanoflares are frequent
enough to account for the lower (compared to active regions) energy
losses in this case.
Title: Investigation of the role of magnetic cancellation in
triggering solar eruptions in NOAA AR12017
Authors: Chintzoglou, G.; Cheung, M. C. M.; De Pontieu, B.
Bibcode: 2016usc..confE.121C
Altcode:
During its evolution, NOAA AR12017 was the source of 3 Coronal Mass
Ejections (CMEs) and a multitude of energetic flares. In its early
stages of its evolution it appeared to emerge as a single bipole, which
was followed by the emergence of a smaller (secondary) bipole near
its pre-existing leading polarity, forming a new polarity inversion
line (PIL) between the non-conjugated opposite polarities as well as
an evolving magnetic topology in the solar corona. Using photospheric
magnetic field observations from SDO/HMI, spectra and imaging from IRIS
covering the photosphere and transition region, coronal observations
from SDO/AIA and flare centroids from RHESSI, we investigate the
cause(s) of activity associated with the new PIL. The time range of
the observations spans several hours prior and up to the time of the
X1.0 flare (associated with a CME eruption). Continuous photospheric
cancellation correlates with flaring activity in the X-rays right at
the new PIL, which suggests that cancellation is dominant mechanism
for the activity of this extremely flare-productive AR.
Title: Magnetic Flux Rope Shredding by Quasi-Separatrix Layers:
The Detrimental Effects of Magnetic Topology on Solar Eruptions
Authors: Chintzoglou, Georgios; Stenborg, Guillermo; Savcheva, Antonia;
Vourlidas, Angelos; Tassev, Svetlin; Tun Beltran, Samuel
Bibcode: 2016cosp...41E.348C
Altcode:
We present the analysis of an unusual failed eruption event observed in
high cadence and in many wavelengths during the campaign in support of
the VAULT2.0 sounding rocket launch. The refurbished Very high Angular
resolution Ultraviolet Telescope (VAULT2.0) is a Lyalpha (1216AA)
spectroheliograph launched on September 30, 2014. The objective of the
VAULT2.0 project is the study of the chromosphere-corona interface. The
observing campaign targeted active region AR 12172 and was closely
coordinated with the textsl{Hinode/} and textsl{IRIS/} missions and
several ground-based observatories (NSO/IBIS an SOLIS, and BBSO)
). A filament eruption accompanied by small level heating (at the
GOES C-class level) occurred around the VAULT2.0 launch. No CME was
observed. The eruption and its source region, however, was recorded by
the campaign instruments in all atmospheric heights ranging from the
photosphere to the corona in high cadence and spatial resolution. This
is a rare occasion which enables us to perform a comprehensive
investigation on a failed eruption. We find that a rising Magnetic
Flux Rope-like (MFR) structure was destroyed during its interaction
with the overlying magnetic field creating downflows of cool plasma and
diffuse hot coronal structures reminiscent of 'spines'. We employ MHD
simulations to show that the magnetic topology of the overlying field
is responsible for the destruction of the MFR. Our unique observations
suggest that the magnetic topology of the corona is a key ingredient
for a successful eruption.
Title: A Study of Solar Magnetic Fields Below the Surface, at the
Surface, and in the Solar Atmosphere - Understanding the Cause of
Major Solar Activity
Authors: Chintzoglou, Georgios
Bibcode: 2016SPD....4730503C
Altcode:
The fundamental processes regarding the origin, emergence and evolution
of solar magnetic fields as well as the generation of solar activity
are largely unknown or remain controversial. In this dissertation,
multiple important issues regarding solar magnetism and activities are
addressed, based on advanced observations obtained by the AIA and HMI
instruments aboard the SDO spacecraft.This dissertation addresses the
3D magnetic structure of complex emerging Active Regions (ARs). In
ARs the photospheric fields might show all aspects of complexity,
from simple bipolar regions to extremely complex multipolar surface
magnetic distributions. Here, we introduce a novel technique to infer
the subphotospheric configuration of emerging magnetic flux tubes
forming ARs on the surface. Using advanced 3D visualization tools with
this technique on a complex flare and CME productive AR, we found that
the magnetic flux tubes forming the complex AR may originate from a
single progenitor flux tube in the SCZ. The complexity can be explained
as a result of vertical and horizontal bifurcations that occurred on
the progenitor flux tube.In addition, this dissertation proposes a new
scenario on the origin of major solar activity. When more than one flux
tubes are in close proximity to each other while they break through
the photospheric surface, collision and shearing may occur as they
emerge. Once this collisional shearing occurs between nonconjugated
sunspots (opposite polarities not belonging to the same bipole),
major solar activity is triggered. The collision and shearing occur
due to the natural separation of polarities in emerging bipoles. In
this continuous collision, more poloidal flux is added to the system
effectively creating an expanding MFR into the corona, accompanied
by filament formation above the PIL together with flare activity and
CMEs. Our results reject two popular scenarios on the possible cause
of solar eruptions (1) shearing motion between conjugate polarities,
(2) bodily emergence of an MFR.
Title: A study of solar magnetic fields below the surface, at the
surface, and in the solar atmosphere – understanding the cause of
major solar activity
Authors: Chintzoglou, Georgios
Bibcode: 2016PhDT........14C
Altcode:
Magnetic fields govern all aspects of solar activity from the 11-year
solar cycle to the most energetic events in the solar system, such as
solar flares and Coronal Mass Ejections (CMEs). As seen on the surface
of the sun, this activity emanates from localized concentrations of
magnetic fields emerging sporadically from the solar interior. These
locations are called solar Active Regions (ARs). However, the
fundamental processes regarding the origin, emergence and evolution
of solar magnetic fields as well as the generation of solar activity
are largely unknown or remain controversial. In this dissertation,
multiple important issues regarding solar magnetism and activities
are addressed, based on advanced observations obtained by AIA and HMI
instruments aboard the SDO spacecraft. First, this work investigates the
formation of coronal magnetic flux ropes (MFRs), structures associated
with major solar activity such as CMEs. In the past, several theories
have been proposed to explain the cause of this major activity, which
can be categorized in two contrasting groups (a) the MFR is formed in
the eruption, and (b) the MFR pre-exists the eruption. This remains
a topic of heated debate in modern solar physics. This dissertation
provides a complete treatment of the role of MFRs from their genesis
all the way to their eruption and even destruction. The study has
uncovered the pre-existence of two weakly twisted MFRs, which formed
during confined flaring 12 hours before their associated CMEs. Thus,
it provides unambiguous evidence for MFRs truly existing before the
CME eruptions, resolving the pre-existing MFR controversy. Second,
this dissertation addresses the 3-D magnetic structure of complex
emerging ARs. In ARs the photospheric fields might show all aspects of
complexity, from simple bipolar regions to extremely complex multi-polar
surface magnetic distributions. In this thesis, we introduce a novel
technique to infer the subphotospheric configuration of emerging
magnetic flux tubes while forming ARs on the surface. Using advanced
3D visualization tools and applying this technique on a complex flare
and CME productive AR, we found that the magnetic flux tubes involved
in forming the complex AR may originate from a single progenitor
flux tube in the SCZ. The complexity can be explained as a result of
vertical and horizontal bifurcations that occurred on the progenitor
flux tube. Third, this dissertation proposes a new scenario on the
origin of major solar activity. When more than one flux tubes are in
close proximity to each other while they break through the photospheric
surface, collision and shearing may occur as they emerge. Once this
collisional shearing occurs between nonconjugated sunspots (opposite
polarities not belonging to the same bipole), major solar activity
is triggered. The collision and the shearing occur due to the natural
separation of polarities in emerging bipoles. This is forcing changes in
the connectivity close to the photosphere (up to a few local pressure
scale heights above the surface) by means of photospheric reconnection
and subsequent submergence of small bipoles at the collision interface
(polarity inversion line; PIL). In this continuous collision, more
poloidal flux is added to the system effectively creating an expanding
MFR into the corona, explaining the observation of filament formation
above the PIL together with flare activity and CMEs. Our results reject
two popular scenarios on the possible cause of solar eruptions (1)
eruption occurs due to shearing motion between conjugate polarities,
and, (2) bodily emergence of an MFR.
Title: Investigation of the Chromosphere-Corona Interface with the
Upgraded Very High Angular Resolution Ultraviolet Telescope (VAULT2.0)
Authors: Vourlidas, Angelos; Beltran, Samuel Tun; Chintzoglou,
Georgios; Eisenhower, Kevin; Korendyke, Clarence; Feldman, Ronen;
Moser, John; Shea, John; Johnson-Rambert, Mary; McMullin, Don;
Stenborg, Guillermo; Shepler, Ed; Roberts, David
Bibcode: 2016JAI.....540003V
Altcode:
Very high angular resolution ultraviolet telescope (VAULT2.0) is a
Lyman-alpha (Lyα; 1216Å) spectroheliograph designed to observe
the upper chromospheric region of the solar atmosphere with high
spatial (<0.5‧‧) and temporal (8s) resolution. Besides being
the brightest line in the solar spectrum, Lyα emission arises at
the temperature interface between coronal and chromospheric plasmas
and may, hence, hold important clues about the transfer of mass and
energy to the solar corona. VAULT2.0 is an upgrade of the previously
flown VAULT rocket and was launched successfully on September 30, 2014
from White Sands Missile Range (WSMR). The target was AR12172 midway
toward the southwestern limb. We obtained 33 images at 8s cadence at
arc second resolution due to hardware problems. The science campaign
was a resounding success, with all space and ground-based instruments
obtaining high-resolution data at the same location within the AR. We
discuss the science rationale, instrument upgrades, and performance
during the first flight and present some preliminary science results.
Title: The Major Geoeffective Solar Eruptions of 2012 March 7:
Comprehensive Sun-to-Earth Analysis
Authors: Patsourakos, S.; Georgoulis, M. K.; Vourlidas, A.; Nindos,
A.; Sarris, T.; Anagnostopoulos, G.; Anastasiadis, A.; Chintzoglou,
G.; Daglis, I. A.; Gontikakis, C.; Hatzigeorgiu, N.; Iliopoulos, A. C.;
Katsavrias, C.; Kouloumvakos, A.; Moraitis, K.; Nieves-Chinchilla, T.;
Pavlos, G.; Sarafopoulos, D.; Syntelis, P.; Tsironis, C.; Tziotziou,
K.; Vogiatzis, I. I.; Balasis, G.; Georgiou, M.; Karakatsanis, L. P.;
Malandraki, O. E.; Papadimitriou, C.; Odstrčil, D.; Pavlos, E. G.;
Podlachikova, O.; Sandberg, I.; Turner, D. L.; Xenakis, M. N.; Sarris,
E.; Tsinganos, K.; Vlahos, L.
Bibcode: 2016ApJ...817...14P
Altcode:
During the interval 2012 March 7-11 the geospace experienced a
barrage of intense space weather phenomena including the second
largest geomagnetic storm of solar cycle 24 so far. Significant
ultra-low-frequency wave enhancements and relativistic-electron dropouts
in the radiation belts, as well as strong energetic-electron injection
events in the magnetosphere were observed. These phenomena were
ultimately associated with two ultra-fast (>2000 km s-1)
coronal mass ejections (CMEs), linked to two X-class flares launched
on early 2012 March 7. Given that both powerful events originated from
solar active region NOAA 11429 and their onsets were separated by less
than an hour, the analysis of the two events and the determination
of solar causes and geospace effects are rather challenging. Using
satellite data from a flotilla of solar, heliospheric and magnetospheric
missions a synergistic Sun-to-Earth study of diverse observational
solar, interplanetary and magnetospheric data sets was performed. It was
found that only the second CME was Earth-directed. Using a novel method,
we estimated its near-Sun magnetic field at 13 R⊙ to be
in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun
CME magnetic field are required to match the magnetic fields of the
corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream
solar-wind conditions, as resulting from the shock associated with the
Earth-directed CME, offer a decent description of its kinematics. The
magnetospheric compression caused by the arrival at 1 AU of the shock
associated with the ICME was a key factor for radiation-belt dynamics.
Title: Triggering an Eruptive Flare by Emerging Flux in a Solar
Active-Region Complex
Authors: Louis, Rohan E.; Kliem, Bernhard; Ravindra, B.; Chintzoglou,
Georgios
Bibcode: 2015SoPh..290.3641L
Altcode: 2015arXiv150608035L; 2015SoPh..tmp...81L
A flare and fast coronal mass ejection originated between solar active
regions NOAA 11514 and 11515 on 2012 July 1 (SOL2012-07-01) in response
to flux emergence in front of the leading sunspot of the trailing
region 11515. Analyzing the evolution of the photospheric magnetic flux
and the coronal structure, we find that the flux emergence triggered
the eruption by interaction with overlying flux in a non-standard
way. The new flux neither had the opposite orientation nor a location
near the polarity inversion line, which are favorable for strong
reconnection with the arcade flux under which it emerged. Moreover,
its flux content remained significantly smaller than that of the arcade
(≈40 % ). However, a loop system rooted in the trailing active region
ran in part under the arcade between the active regions, passing over
the site of flux emergence. The reconnection with the emerging flux,
leading to a series of jet emissions into the loop system, caused a
strong but confined rise of the loop system. This lifted the arcade
between the two active regions, weakening its downward tension force and
thus destabilizing the considerably sheared flux under the arcade. The
complex event was also associated with supporting precursor activity in
an enhanced network near the active regions, acting on the large-scale
overlying flux, and with two simultaneous confined flares within the
active regions.
Title: Formation of Magnetic Flux Ropes during a Confined Flaring
Well before the Onset of a Pair of Major Coronal Mass Ejections
Authors: Chintzoglou, Georgios; Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2015ApJ...809...34C
Altcode: 2015arXiv150701165C
NOAA active region (AR) 11429 was the source of twin super-fast
coronal mass ejections (CMEs). The CMEs took place within an hour
from each other, with the onset of the first taking place in the
beginning of 2012 March 7. This AR fulfills all the requirements for
a “super active region” namely, Hale's law incompatibility and a
δ-spot magnetic configuration. One of the biggest storms of Solar
Cycle 24 to date ({D}{st}=-143 nT) was associated with
one of these events. Magnetic flux ropes (MFRs) are twisted magnetic
structures in the corona, best seen in ∼10 MK hot plasma emission
and are often considered the core of erupting structures. However,
their “dormant” existence in the solar atmosphere (i.e., prior to
eruptions), is an open question. Aided by multi-wavelength observations
by the Solar Dynamics Observatory (SDO) and by the Solar Terrestrial
Relations Observatory (STEREO) and a nonlinear force-free model for the
coronal magnetic field, our work uncovers two separate, weakly twisted
magnetic flux systems which suggest the existence of pre-eruption MFRs
that eventually became the seeds of the two CMEs. The MFRs could have
been formed during confined (i.e., not leading to major CMEs) flaring
and sub-flaring events which took place the day before the two CMEs
in the host AR 11429.
Title: Investigation of a failed Filament Eruption During the VAULT2.0
Campaign Observations
Authors: Chintzoglou, Georgios; Vourlidas, Angelos; Tun-Beltran,
Samuel; Stenborg, Guillermo
Bibcode: 2015TESS....130217C
Altcode:
We report the first results from an observing campaign in support of
the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0 is
a Lya (1216Å) spectroheliograph capable of 0.4” (~300 km) spatial
resolution. The objective of the VAULT2.0 project is the study of the
chromosphere-corona interface. VAULT2.0 observations probe temperatures
between 10000 and 50000 K, a regime not accessible by Hinode or
SDO. Lyα observations are, therefore, ideal, for filling in this
gap. The observing campaign was closely coordinated with the Hinode
and IRIS missions. Several ground-based observatories also provided
important observations (IBIS, BBSO, SOLIS). Taking advantage of this
simultaneous multi-wavelength coverage of target AR 12172 we are able
to perform a detailed investigation on a failed eruption of a Magnetic
Flux Rope-like structure that was recorded in the joint observations,
starting before VAULT2.0's flight.
Title: The Physical Processes of Eruptive Flares Revealed By An
Extremely-Long-Duration Event
Authors: Zhou, Zhenjun; Zhang, Jie; Chintzoglou, Georgios
Bibcode: 2015TESS....121005Z
Altcode:
In this work, we report the physical processes of eruptive flares
inferred from an extremely- long-duration event occurred on June 21,
2011. The flare, peaked at C7.5 level, had a two-hour-long rise time
in soft X-rays; this rise time is much longer than the usual rise
time of solar flares that last for only about ten minutes. Combining
the fact that the flare occurred near the disk center as seen by SDO,
but near the limbs as seen by STEREO A and B, we are able to track
the evolution of the eruption in 3-D as well as in a rare slow-motion
manner. The time sequence of temperature maps, constructed from six
corona-temperature passbands of AIA, clearly shows process of how the
highly-twisted sigmoid structure prior to the eruption is transformed
into a near-potential post-eruption loop arcade. The observed sigmoid
is likely to be the structure of a twisted magnetic flux rope, which
reached a height of about 60 Mm at the onset of the eruption. The onset
is likely triggered by the instability (or loss of equilibrium) of the
flux rope as indicated by the slow rise motion prior to the impulsive
phase. We also find that the complex evolution of footprints of the
eruption as seen from AIA transition region images is consistent with
the magnetic evolution in the corona, which is the consequence of the
combined effects of the expansion of the magnetic flux rope and the
magnetic reconnection of surrounding magnetic fields. The 3-D magnetic
structure inferred from NLFFF extrapolation will be compared with that
inferred from observations.
Title: A Tale of Two Super-Active Active Regions: On the Magnetic
Origin of Flares and CMEs
Authors: Zhang, Jie; Dhakal, Suman; Chintzoglou, Georgios
Bibcode: 2015TESS....140801Z
Altcode:
From a comparative study of two super-active active regions, we find
that the magnetic origin of CMEs is different from that of flares. NOAA
AR 12192 is one of the largest active regions in the recorded history
with a sunspot number of 66 and area of 2410 millonths. During its
passage through the front disk from Oct. 14-30, 2014, the active
region produced 93 C-class, 30 M-class and 6 X-class flares. However,
all six X-class flares are confined; in other words, none of them
are associated with CMEs; most other flares are also confined. This
behavior of low-CME production rate for such as a super active region
is rather peculiar, given the usual hand-on-hand occurrence of CMEs
with flares. To further strengthen this point, we also investigated the
super-active NOAA AR 11429, which had a sunspot number of 28 and area of
1270 millionths. During its passage from March 02-17, 2012, the active
region produced 47 C-class, 15 M-class and 3 X-class flares. In this
active region, all three X-class flares were accompanied by CMEs, and
the same for most M-class flares. Given the relative sizes of the two
active regions, the production rates of flares are comparable. But the
CME production rates are not. Through a careful study of the magnetic
configuration on the surface and the extrapolated magnetic field in
the corona, we argue that the generation of flares largely depends on
the amount of free energy in the active region. On the other hand,
the generation of CMEs largely depends on the complexity, such as
measured by magnetic helicity. In particular, we argue that the high CME
generation rate in the smaller active region is caused by the emergence
and continuous generation of magnetic flux ropes in the region.
Title: Independent CMEs from a Single Solar Active Region - The Case
of the Super-Eruptive NOAA AR11429
Authors: Chintzoglou, Georgios; Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2014AAS...22432328C
Altcode:
In this investigation we study AR 11429, the origin of the twin
super-fast CME eruptions of 07-Mar-2012. This AR fulfills all the
requirements for the 'perfect storm'; namely, Hale's law incompatibility
and a delta-magnetic configuration. In fact, during its limb-to-limb
transit, AR 11429 spawned several eruptions which caused geomagnetic
storms, including the biggest in Cycle 24 so far. Magnetic Flux Ropes
(MFRs) are twisted magnetic structures in the corona, best seen in
~10MK hot plasma emission and are often considered as the culprit
causing such super-eruptions. However, their 'dormant' existence in
the solar atmosphere (i.e. prior to eruptions), is a matter of strong
debate. Aided by multi-wavelength and multi-spacecraft observations
(SDO/HMI & AIA, HINODE/SOT/SP, STEREO B/EUVI) and by using a
Non-Linear Force-Free (NLFFF) model for the coronal magnetic field,
our work shows two separate, weakly-twisted magnetic flux systems
which suggest the existence of possible pre-eruption MFRs.
Title: An Innovative Technique of Reconstructing 3-D magnetic Field
Structure in the Sub-photosphere and the Corona of the Sun
Authors: Zhang, Jie; Chintzoglou, Georgios
Bibcode: 2014cosp...40E3782Z
Altcode:
We present an innovative technique of reconstructing 3-D magnetic
structure of emerging active regions in both the sub-photosphere
and the corona. This technique takes the full advantage of the
advanced observations of SDO/HMI instrument, which provides full disk
photospheric vector magnetic field measurement in every 12 minutes
and the line-of-sight field measurement in every 45 seconds. This
unprecedented cadence allows continuous stacking of images in time,
producing a 3-D data cube that preserves the necessary detail for 3-D
reconstruction analysis. The validity of the technique is based on
the reasonable assumption that, for newly emerging active regions, the
time variation on the photosphere is dominated by the spatial variation
along the vertical direction of an emerging 3-D structure. Among many
important applications of this method, we will focus on the topic of the
true 3-D magnetic structure of complex active regions that have many
magnetic poles, delta configuration and complicated shearing motion
on the surface; these regions are usually the sources of severe space
weather events Our analysis shows that such complex active regions
could be the consequence of the emergence of a giant magnetic tube
that is subjected to both horizontal and vertical splitting during
its rise motion through the convection zone. Other applications will
be also discussed.
Title: Reconstructing the Subsurface Three-dimensional Magnetic
Structure of a Solar Active Region Using SDO/HMI Observations
Authors: Chintzoglou, G.
Bibcode: 2013hell.conf....5C
Altcode:
A solar active region (AR) is a three-dimensional (3D) magnetic
structure formed in the convection zone, whose property is fundamentally
important for determining the coronal structure and solar activity
when emerged. However, our knowledge of the detailed 3D structure
prior to its emergence is rather poor, largely limited by the low
cadence and sensitivity of previous instruments. Here, using the 45 s
high-cadence observations from the Helioseismic and Magnetic Imager
on board the Solar Dynamics Observatory, we are able for the first
time to reconstruct a 3D data cube and infer the detailed subsurface
magnetic structure of NOAA AR 11158, and to characterize its magnetic
connectivity and topology. This task is accomplished with the aid of
the image-stacking method and advanced 3D visualization. We find that
the AR consists of two major bipoles or four major polarities. Each
polarity in 3D shows interesting tree-like structure, i.e., while
the root of the polarity appears as a single tree-trunk-like tube,
the top of the polarity has multiple branches consisting of smaller
and thinner flux tubes which connect to the branches of the opposite
polarity that is similarly fragmented. The roots of the four polarities
align well along a straight line, while the top branches are slightly
noncoplanar. Our observations suggest that an active region, even
appearing highly complicated on the surface, may originate from a
simple straight flux tube that undergoes both horizontal and vertical
bifurcation processes during its rise through the convection zone.
Title: Time Dependence of Joy's Law for Emerging Active Regions
Authors: Chintzoglou, Georgios; Zhang, J.; Liu, Y.
Bibcode: 2013SPD....44..107C
Altcode:
Joy's law governs the tilt of Active Regions (ARs) with respect to
their absolute heliographic latitude. Together with Hale's law of
hemispheric polarity, it is essential in constraining solar dynamo
models. However, previous studies on Joy's law show only a weak
positive trend between AR tilt angles and latitudes. In this study,
we are focusing on the time dependence of Joy's law, for the cases of
emerging ARs of Solar Cycle 24. We selected 40 ARs that emerge on the
East hemisphere, effectively maximizing the observing time for each
AR. Then, by converting the helioprojective maps into heliographic,
we determine the geometrical as well as the magnetic-flux-weighted
centroids for each emergence case. That way we are able to track the
temporal evolution of their physical properties, including locations,
fluxes of positive and negative polarities, as well as the tilt angles
of these regions in a continuous manner until emergence stops and the
ARs assume their final state.
Title: Time Dependence of Joy's Law for Emerging Active Regions
Authors: Chintzoglou, Georgios
Bibcode: 2013shin.confE..93C
Altcode:
Joy's law governs the tilt of Active Regions (ARs) with respect to
their absolute heliographic latitude. Together with Hale's law of
hemispheric polarity, it is essential in constraining solar dynamo
models. However, previous studies on Joy's law show only a weak
positive trend between AR tilt angles and latitudes. In this study,
we are focusing on the time dependence of Joyś law, for the cases of
emerging ARs of Solar Cycle 24. We selected ARs that emerge on the
East hemisphere, effectively maximizing the observing time for each
AR. Then, by converting the helioprojective maps into heliographic,
we determine the geometrical as well as the magnetic-flux-weighted
centroids for each emergence case. That way we are able to track the
temporal evolution of their physical properties, including locations,
fluxes of positive and negative polarities, as well as the tilt angles
of these regions in a continuous manner until emergence stops and the
ARs assume their final state.
Title: "Reconstructing the Subsurface Three-Dimensional Magnetic
Structure of A Solar Active Region Using SDO/HMI Observations"
Authors: Chintzoglou, Georgios; Zhang, Jie
Bibcode: 2013enss.confE...5C
Altcode:
A solar active region (AR) is a three-dimensional magnetic structure
formed in the convection zone, whose property is fundamentally
important for determining the coronal structure and solar activity when
emerged. However, our knowledge on the detailed 3-D structure prior
to its emergence is rather poor, largely limited by the low cadence
and sensitivity of previous instruments. Here, using the 45-second
high-cadence observations from the Helioseismic and Magnetic Imager
(HMI) onboard the Solar Dynamics Observatory (SDO), we are able for
the first time to reconstruct a 3-D Datacube and infer the detailed
subsurface magnetic structure of NOAA AR 11158 and to characterize its
magnetic connectivity and topology. This task is accomplished with the
aid of the image-stacking method and advanced 3-D visualization. We
find that the AR consists of two major bipoles, or four major
polarities. Each polarity in 3-D shows interesting tree-like structure,
i.e. while the root of the polarity appears as a single tree-trunk-like
tube, the top of the polarity has multiple branches consisting of
smaller and thinner flux-tubes which connect to the branches of the
opposite polarity that is similarly fragmented. The roots of the four
polarities align well along a straight line, while the top branches are
slightly non-coplanar. Our observations suggest that an active region,
even appearing most complicated on the surface, may originate from a
simple straight flux-tube that undergoes both horizontal and vertical
bifurcation processes during its rise through the convection zone.
Title: Reconstructing the Subsurface Three-dimensional Magnetic
Structure of a Solar Active Region Using SDO/HMI Observations
Authors: Chintzoglou, Georgios; Zhang, Jie
Bibcode: 2013ApJ...764L...3C
Altcode: 2013arXiv1301.4651C
A solar active region (AR) is a three-dimensional (3D) magnetic
structure formed in the convection zone, whose property is fundamentally
important for determining the coronal structure and solar activity
when emerged. However, our knowledge of the detailed 3D structure
prior to its emergence is rather poor, largely limited by the low
cadence and sensitivity of previous instruments. Here, using the 45 s
high-cadence observations from the Helioseismic and Magnetic Imager
on board the Solar Dynamics Observatory, we are able for the first
time to reconstruct a 3D data cube and infer the detailed subsurface
magnetic structure of NOAA AR 11158, and to characterize its magnetic
connectivity and topology. This task is accomplished with the aid of
the image-stacking method and advanced 3D visualization. We find that
the AR consists of two major bipoles or four major polarities. Each
polarity in 3D shows interesting tree-like structure, i.e., while
the root of the polarity appears as a single tree-trunk-like tube,
the top of the polarity has multiple branches consisting of smaller
and thinner flux tubes which connect to the branches of the opposite
polarity that is similarly fragmented. The roots of the four polarities
align well along a straight line, while the top branches are slightly
non-coplanar. Our observations suggest that an active region, even
appearing highly complicated on the surface, may originate from a
simple straight flux tube that undergoes both horizontal and vertical
bifurcation processes during its rise through the convection zone.
Title: The Three-Dimensional Reconstruction of the AR 11158 During
its Emergence Phase Using SDO/HMI Observations
Authors: Chintzoglou, Georgios; Zhang, J.
Bibcode: 2012AAS...22020624C
Altcode:
A solar active region (AR) is a three dimensional magnetic structure
formed in the convection zone, whose property is fundamentally
important for determining coronal structure and solar activity when
emerged. However, our knowledge on the detailed 3-D structure prior
to its emergence is rather poor. Previous observational work on AR
emergence has been limited by instrumental capabilities - low fidelity,
low-cadence magnetograms. At the same time, our theoretical knowledge
relies on overly simplified assumptions based on MHD simulations or
the thin flux tube approximation. Here, we are able to observationally
determine and reconstruct the three-dimensional magnetic structure of
AR 11158 during the emergence phase and to characterize its magnetic
connectivity and topology. This task is accomplished with the aid of
the time-stacking method and advanced 3-D visualization, applied on
magnetograph observations from the HMI instrument of the SDO mission,
taking full advantage of its unprecedented temporal resolution. We
find that the AR consists of two major dipoles. The two polarities of
each dipole show interesting tree-like structure, i.e. while the bottom
of the polarity appears as a single trunk-like flux tube, the top of
the polarity has multiple branches, consisting of smaller and thinner
flux tubes which connect to the branches of the opposite polarity. The
four roots of the two dipoles align well along a straight line, while
the top branches are slightly non-coplanar. The detailed 3-D topology
and connectivity of AR 11158 will be presented in this meeting.
Title: A Revisit of Hale's and Joy's Laws of Active Regions Using
SOHO MDI Observations
Authors: Chintzoglou, Georgios; Zhang, Jie
Bibcode: 2011shin.confE..66C
Altcode:
Hale's law of polarity defines the rule of opposite direction
of two polarities of solar bipolar Active Regions in the two
hemispheres. Another law, Joy's law, governs the tilt of ARs with
respect to their heliographic latitudes. Both laws are essential for
constraining solar dynamo models. In this study we attempt to examine
these laws in great detail using a large sample of ARs. With the help of
an automatic AR detection algorithm (based on morphological analysis,
Zhang et. al, 2010), we have processed high resolution SOHO/MDI
synoptic magnetograms over the entire solar cycle 23, we identified
all active regions in a uniform and objective way and determined
their physical properties, including locations, fluxes of positive
and negative polarities, as well as the orientation angles of these
regions. Among 1084 bipolar ARs detected, the majority of them (87%)
follow Hale's polarity law, while the other 13% of ARs do not. We
attribute this deviation to the complexity of AR emergence from the
turbulent convection zone. Regarding the Joy's law, we find that there
is only a weak positive trend between AR tilt angles and latitudes. On
the other hand, the tilt angle has a broad Gaussian-like distribution,
with the peak centered around 8.4 degree, and a width of 19.5 degrees
at half maximum.
Title: A Revisit of Hale's and Joy's Laws of Active Regions Using
SOHO MDI Obsevations
Authors: Chintzoglou, Georgios; Zhang, J.
Bibcode: 2011SPD....42.1710C
Altcode: 2011BAAS..43S.1710C
Hale's law of polarity defines the rule of opposite direction
of two polarities of solar bipolar Active Regions in the two
hemispheres. Another law, Joy's law, governs the tilt of ARs with
respect to their heliographic latitudes. Both laws are essential for
constraining solar dynamo models. In this study we attempt to examine
these laws in great detail using a large sample of ARs. With the
help of an automatic AR detection algorithm (based on morphological
analysis, Zhang et. al, 2010), we have processed high resolution
SOHO/MDI synoptic magnetograms over the entire solar cycle 23, we
identified all active regions in a uniform and objective way and
determined their physical properties, including locations, fluxes of
positive and negative polarities ,as well as the direction angles of
these regions. Among 1084 bipolar ARs detected, the majority of them
(87%) follow Hale's polarity law, while the other 13% of ARs do not. We
attribute this deviation to the complexity of AR emergence from the
turbulent convection zone. Regarding the Joy's law, we find that there
is only a weak positive trend between AR tilt angles and latitudes. On
the other hand, the tilt angle has a broad Gaussian-like distribution,
with the peak centered around zero degree, and a width of about 20
degree at half maximum. Implications of these results on solar dynamo
theory will be discussed.