Author name code: muglach
ADS astronomy entries on 2022-09-14
author:"Muglach, Karin"
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Title: Evaluating current methods for establishing magnetic
connectivity across the solar atmosphere
Authors: Pinto, Rui; Kouloumvakos, Athanasios; Linker, Jon; Arge,
Charles; Reiss, Martin; Muglach, Karin; Ko, Yuan-Kuen; Henney, Carl J.
Bibcode: 2022cosp...44.3504P
Altcode:
Establishing magnetic connectivity from the solar surface to any
point in the interplanetary space is a key challenge in today's space
physics, fundamental for the determination of causal links between
different types of solar and heliospheric phenomena that take place
at large distances from each other. Solar Orbiter and Parker Solar
Probe constitute a landmark in terms of connectivity science. They led
to collective efforts to relate remote observations to in-situ data
(traditionally studied by different communities) from one or more
spacecraft, and to build tools and methods that establish connectivity
systematically. We report on the progresses of the ISWAT team S2-05
on the design of a set of case studies meant to cover a diverse set of
connectivity scenarios that can be studied using different combinations
of models and datasets, while trying to maximize the number of possible
diagnostics.
Title: Photospheric Flow Fields in a Coronal Bright Point
Authors: Peat, Aaron; Labrosse, Nicolas; Muglach, Karin
Bibcode: 2022cosp...44.2565P
Altcode:
The relationship between the flows in the photosphere and the migration
of magnetic polarity patches leading to a coronal bright point is
investigated. As seen in SDO/AIA images the formation of this coronal
bright point began end of day on 2017-09-24, with the event peaking
at approximately 10.00 on 2017-09-25, and ending 2017-09-27. In all,
the evolution of the bright point was followed over about 3 days. We
employ Fourier Local Correlation Tracking (FLCT) to recover the
photospheric flow fields in HMI Intensity images around the area in
which the bright point forms. Then, using the flow vectors produced
by FLCT, we investigate the relationship between these photospheric
flow fields and the flux emergence, and the effect they have on the
formation and evolution of the coronal bright point.
Title: Unifying the validation of ambient solar wind models in
the community
Authors: Reiss, Martin; Muglach, Karin; Chakraborty, Shibaji
Bibcode: 2022cosp...44.3505R
Altcode:
To make progress in space weather research and awareness, we need
international community strategies and procedures to assess our
modeling assets. Here we present the actions of the Ambient Solar
Wind Validation Team embedded in the COSPAR ISWAT initiative. Our
team's mission is to provide the space weather community with an
assessment of the state-of-the-art in solar wind forecasting. To do so,
we develop an open online platform that allows the community to test
the quality of solar wind models with unified metrics and document
progress over time. We discuss challenges in realizing our objectives,
present a status update, and outline future perspectives. We furthermore
highlight community activities in the ISWAT initiative that complement
our efforts by addressing key science questions related to the solar
magnetic field and solar wind origins.
Title: Velocities of an Erupting Filament
Authors: Wang, Shuo; Jenkins, Jack M.; Muglach, Karin; Martinez Pillet,
Valentin; Beck, Christian; Long, David M.; Choudhary, Debi Prasad;
McAteer, James
Bibcode: 2022ApJ...926...18W
Altcode: 2021arXiv211107830W
Solar filaments exist as stable structures for extended periods of
time before many of them form the core of a coronal mass ejection
(CME). We examine the properties of an erupting filament on 2017 May
29-30 with high-resolution He I 10830 Å and Hα spectra from the
Dunn Solar Telescope, full-disk Dopplergrams of He I 10830 Å from
the Chromospheric Telescope, and EUV and coronograph data from SDO
and STEREO. Pre-eruption line-of-sight velocities from an inversion
of He I with the HAZEL code exhibit coherent patches of 5 Mm extent
that indicate counter-streaming and/or buoyant behavior. During the
eruption, individual, aligned threads appear in the He I velocity
maps. The distribution of velocities evolves from Gaussian to strongly
asymmetric. The maximal optical depth of He I 10830 Å decreased from
τ = 1.75 to 0.25, the temperature increased by 13 kK, and the average
speed and width of the filament increased from 0 to 25 km s-1
and 10 to 20 Mm, respectively. All data sources agree that the filament
rose with an exponential acceleration reaching 7.4 m s-2
that increased to a final velocity of 430 km s-1 at 22:24
UT; a CME was associated with this filament eruption. The properties
during the eruption favor a kink/torus instability, which requires
the existence of a flux rope. We conclude that full-disk chromospheric
Dopplergrams can be used to trace the initial phase of on-disk filament
eruptions in real time, which might potentially be useful for modeling
the source of any subsequent CMEs.
Title: Information Infrastructure for the Validation of Ambient
Solar Wind Models
Authors: Muglach, Karin; Reiss, Martin; Wiegand, Chiu; Mullinix,
Richard; Kuznetsova, Maria
Bibcode: 2021AGUFMSH44C..05M
Altcode:
Over the past decades, many empirical and physics-based numerical models
for predicting the evolving ambient solar wind flow at Earth have been
developed. To evaluate the predictive skill of these models, they
are usually compared with solar wind measurements taken by in-situ
spacecraft. The activities of the Ambient Solar Wind Validation
Team embedded in the COSPAR ISWAT initiative are centered around the
validation of these solar wind models. An important part of such a
model-observation comparison is keeping track of versions of models
and model runs via their metadata. In this presentation, we show our
ambient solar wind validation platform that we have set up using the
Comprehensive Assessment of Models and Events using Library Tools
(CAMEL) framework provided by the Community Coordinated Modeling
Center (the figure included in this abstract shows an early version of
CAMEL). We discuss the CAMEL framework as well as other information
infrastructure that we utilize to make this community validation
effort possible.
Title: The Observational Uncertainty of Coronal Hole Boundaries in
Automated Detection Schemes
Authors: Reiss, Martin; Muglach, Karin; Moestl, Christian; Arge,
Charles; Bailey, Rachel; Delouille, Veronique; Garton, Tadhg; Hamada,
Amr; Hofmeister, Stefan; Illarionov, Egor; Jarolim, Robert; Kirk,
Michael; Kosovichev, Alexander; Krista, Larisza; Lee, Sangwoo; Lowder,
Chris; MacNeice, Peter; Veronig, Astrid
Bibcode: 2021AGUFMSH15G2083R
Altcode:
Solar coronal holes are the observational manifestation of the solar
magnetic field open to the heliosphere and are of pivotal importance
for understanding the origin and acceleration of the solar wind. Space
missions such as the Solar Dynamics Observatory now allow us to observe
coronal holes in unprecedented detail. Instrumental effects and other
factors, however, pose a challenge to automated detection of coronal
holes in solar imagery. The science community addresses these challenges
with a variety of detection schemes. Until now, scant attention has
been paid to assessing the disagreement between these schemes. Here
we present the first comprehensive comparison of widely-applied
automated detection schemes in solar and space science. By tying
together scientific expertise worldwide, we study a coronal hole
observed by the Atmospheric Imaging Assembly instrument on 2018 May
30. We find that the choice of detection scheme significantly affects
the location of the coronal hole boundary. Depending on the detection
scheme, the physical properties of the coronal hole including the area,
mean intensity, and mean magnetic field strength vary by a factor of
up to 4.5 between the maximum and minimum values. This presentation
discusses the implications of these findings for coronal hole research
from the past decade. We also outline future strategies on how to use
our results to diagnose and improve coronal magnetic field models.
Title: Magnetic Field Curvature In A Filament Channel Derived From
Oscillation Measurements And MHD Modeling
Authors: Kucera, T. A.; Luna, M.; Torok, T.; Muglach, K.; Downs, C.;
Sun, X.; Thompson, B.; Karpen, J.; Gilbert, H.
Bibcode: 2021AAS...23811306K
Altcode:
We have used measurements of repeated large amplitude longitudinal
oscillations (LALOs) in an active region filament to diagnose the
curvature of the magnetic field in the filament channel and compared the
results with predictions of an MHD flux-rope model based on magnetograms
of the region. In May and June of 2014 Active Region 12076 exhibited a
complex of filaments undergoing repeated oscillations over the course
of twelve days. The central filament channel exhibited emerging and then
canceling magnetic flux that resulted in multiple activations, filament
eruptions, and eight oscillation events, which we analyzed using GONG
H-alpha data. Luna and Karpen (2012) model LALOs as oscillations of
magnetized filament plasma moving along dipped magnetic field lines
with gravity as a restoring force. Under this model the period of these
oscillations can be used to estimate the curvature of the magnetic
field in the location of the filament threads. Utilizing this, we find
that the measured periods in the central filament ranging from 34-74
minutes should correspond to magnetic field curvatures of about 30-136
Mm. We also derive radii of curvature for the central filament channel
using a flux-rope model that is based on an SDO/HMI magnetogram of the
region. The rope is constructed using the analytic expressions by Titov
et al. (2018) and then numerically relaxed towards a force-free state in
the zero-beta MHD approximation, where gravity and thermal pressure are
neglected. For comparison, we also employ a nonlinear force-free field
(NLFFF) extrapolation of the active region. We compare the results
of these different ways of attempting to determine the field in the
filament channel.
Title: The Observational Uncertainty of Coronal Hole Boundaries in
Automated Detection Schemes
Authors: Reiss, Martin A.; Muglach, Karin; Möstl, Christian; Arge,
Charles N.; Bailey, Rachel; Delouille, Véronique; Garton, Tadhg M.;
Hamada, Amr; Hofmeister, Stefan; Illarionov, Egor; Jarolim, Robert;
Kirk, Michael S. F.; Kosovichev, Alexander; Krista, Larisza; Lee,
Sangwoo; Lowder, Chris; MacNeice, Peter J.; Veronig, Astrid; Cospar
Iswat Coronal Hole Boundary Working Team
Bibcode: 2021ApJ...913...28R
Altcode: 2021arXiv210314403R
Coronal holes are the observational manifestation of the solar
magnetic field open to the heliosphere and are of pivotal importance
for our understanding of the origin and acceleration of the solar
wind. Observations from space missions such as the Solar Dynamics
Observatory now allow us to study coronal holes in unprecedented
detail. Instrumental effects and other factors, however, pose a
challenge to automatically detect coronal holes in solar imagery. The
science community addresses these challenges with different detection
schemes. Until now, little attention has been paid to assessing the
disagreement between these schemes. In this COSPAR ISWAT initiative,
we present a comparison of nine automated detection schemes widely
applied in solar and space science. We study, specifically, a prevailing
coronal hole observed by the Atmospheric Imaging Assembly instrument
on 2018 May 30. Our results indicate that the choice of detection
scheme has a significant effect on the location of the coronal hole
boundary. Physical properties in coronal holes such as the area, mean
intensity, and mean magnetic field strength vary by a factor of up
to 4.5 between the maximum and minimum values. We conclude that our
findings are relevant for coronal hole research from the past decade,
and are therefore of interest to the solar and space research community.
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
Bibcode: 2021SoPh..296...70R
Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
Title: The Photospheric Footpoints of Solar Coronal Hole Jets
Authors: Muglach, K.
Bibcode: 2021ApJ...909..133M
Altcode:
We study the photospheric footpoints of a set of 35 coronal jets in a
coronal hole as observed by Hinode/EIS. We use SDO/AIA data to coalign
the spectroscopic EIS data with SDO/HMI line-of-sight magnetograms and
calculate the plane-of-sky flow field using local correlation tracking
(LCT) on SDO/HMI white light images. The jets are put into categories
according to the changes observed in the photospheric magnetic flux at
the footpoints of the coronal bright point where the jets originate:
flux cancellation, complex flux changes (flux appearance/emergence
and cancellation), and no flux changes. We also present three jets
in detail. Observed magnetic flux evolution, LCT flow field structure
and location of the jet footpoints at supergranular boundaries do not
support the flux emergence scenario used in most jet simulations and
are also not consistent with a rotational photospheric driver. Detailed
numerical jet simulations using our observed photospheric features,
in particular converging flows and flux cancellation do not currently
exist, although such models would provide a realistic eruptive event
scenario.
Title: Improving Understanding and Assessment of the Ambient
Solar Wind
Authors: Reiss, Martin; Moestl, Christian; Linker, Jon; Mullinix,
Richard; Rastaetter, Lutz; Temmer, Manuela; Arge, Charles; MacNeice,
Peter; Wiegand, Chiu; Muglach, Karin; Ko, Kuen
Bibcode: 2021cosp...43E2398R
Altcode:
The Sun's magnetic field drives the evolving ambient solar wind flow
and the magnetic field embedded within it. Thus, studying the magnetic
field configuration in the solar atmosphere is of crucial importance
for improving our understanding of and ultimately predicting space
weather from Sun to Earth. Coronal holes are regions of low intensity
emission in EUV and X-ray images. Coronal holes are closely associated
with open magnetic field lines, along which the solar wind accelerates
to supersonic speeds. Therefore, they play a central role in shaping
the structure of the heliosphere and defining key properties in
interplanetary space, such as the solar wind bulk speed, magnetic field
strength, and field orientation. Answering vital research questions
related to the ambient solar wind requires an interdisciplinary strategy
and the coordinated collaboration of international partners. Here we
present the COSPAR ISWAT activities for improving the understanding
and assessment of the evolving ambient solar wind flow embedded in
the 'Coronal Hole Boundary Working Team' and the 'Ambient Solar
Wind Validation Team'. Specifically, we present our progress in
evaluating the uncertainty of coronal hole boundary locations in
solar observations, and our progress in establishing an online hub for
validation of ambient solar wind models. In context, we demonstrate
the first application of a new online platform enabling developers
and end-users to directly assess the quality of state-of-the-art
solar wind model solutions. To conclude, we present the objectives,
current status and roadmaps of both action teams, and discuss the main
challenges we face in the realization of our objectives.
Title: Activities related to the COSPAR ISWAT Cluster: Ambient Solar
Magnetic Field, Heating and Spectral Irradiance
Authors: Reiss, Martin; Pevtsov, Alexei; Linker, Jon; Pinto, Rui;
Arge, Charles; Muglach, Karin; Henney, Carl J.
Bibcode: 2021cosp...43E2413R
Altcode:
The understanding of the magnetic field configuration in the solar
atmosphere is of crucial importance for improving the modelling and
ultimately the prediction of space weather from Sun to Earth. The
magnetic field provides the energy source that heats the solar corona
and accelerates the solar wind, and it also defines the structure of
the heliosphere. However, many related unresolved questions require
an interdisciplinary strategy and the coordinated cooperation of
international partners. Here we present the activities of the 'Ambient
Solar Magnetic Field, Heating and Spectral Irradiance' cluster embedded
in the COSPAR ISWAT initiative. The action teams in this cluster will
focus on critical scientific challenges in the space weather community
related to the construction of global solar magnetic field maps, use
of vector field synoptic maps for applied space weather modelling and
research, magnetic connectivity from the surface of the Sun to any
point in interplanetary space, magnetic topology of open field lines
along which solar wind flows accelerate to supersonic speeds, and the
solar spectral irradiance driving ionization and heating in the Earth's
upper atmosphere. We will outline the objectives of the individual
action teams and present the current status and roadmaps. To encourage
the formation of new action teams, we will also discuss additional
challenges that should be addressed by the space weather community.
Title: The COSPAR ISWAT initiative for open validation analysis for
models of the evolving ambient solar wind
Authors: Reiss, Martin; Kuznetsova, Maria; Mullinix, Richard;
Rastaetter, Lutz; Temmer, Manuela; MacNeice, Peter; Wiegand, Chiu;
Muglach, Karin
Bibcode: 2021cosp...43E2363R
Altcode:
Validation analysis plays a critical role in applied space weather
research and prediction. First and foremost to inform developers and
users of space weather models about the strengths and weaknesses of
the models, and also to provide an unbiased assessment of progress
over time. Here we present the activities of the Ambient Solar Wind
Validation Team embedded in the COSPAR ISWAT initiative. The objective
of this action team is to establish an online hub for validation
analysis of ambient solar wind models in correspondence with the
space weather community, allowing developers and end-users to directly
assess the quality of state-of-the-art model solutions. To this end,
we choose and agree on a set of comprehensive validation metrics
reflecting the community needs and integrate them into the existing
Comprehensive Assessment of Models and Events using Library Tools
(CAMEL) web application hosted by NASA's Community Coordinated Modelling
Center. CAMEL is an interactive visualization tool allowing developers
and users to compare space weather and space science model output to
observations. Specifically, we make use of CAMEL to quantitatively
assess the relationship between state-of-the-art solar wind model
solutions and observational data in terms of point-to-point statistics
and more advanced event-based validation measures. In this presentation,
we will demonstrate the first application of the new online platform
with examples of state-of-the-art model solutions. We will also discuss
the main challenges we face in the realization of our objectives,
and present the current status and the roadmap of the action team.
Title: An Adaptive Prediction System for Specifying Solar Wind
Conditions Near the Sun
Authors: Reiss, M.; MacNeice, P. J.; Muglach, K.; Arge, C. N.; Moestl,
C.; Riley, P.; Bailey, R.; Hinterreiter, J.; Weiss, A.; Owens, M. J.;
Henney, C. J.; Amerstorfer, U.; Amerstorfer, T.
Bibcode: 2020AGUFMSM047..01R
Altcode:
Understanding Earth's space weather environment requires a clear picture
of the evolving ambient solar wind flow. Critical scientific goals in
space weather research and prediction are to develop, implement and
optimize approaches for specifying the large-scale solar wind conditions
near the Sun. Here we present an adaptive prediction system that fuses
information from in situ measurements in the vicinity of Earth into
solar wind models to better inform the inner boundary conditions of
heliospheric models. By doing so, we attempt to advance the predictive
abilities of established solar wind models such as the Wang-Sheeley-Arge
approach. We validate the resulting solar wind predictions for the years
2006 to 2015. The adaptive prediction system improves all the coronal
and heliospheric model combinations investigated by around 15 to 20
percent in terms of established validation metrics. We discuss why this
is the case, and conclude that our findings have important implications
for future developments in space weather research and prediction.
Title: Filament Oscillations in Active Region 12076
Authors: Kucera, T. A.; Muglach, K.; Luna Bennasar, M.; Karpen, J.;
Thompson, B.; Gilbert, H.
Bibcode: 2020AAS...23633004K
Altcode:
We present an analysis of repeated large amplitude longitudinal
oscillations (LALO) in filaments in Active Region 12076 in May
and June of 2014. Most of the oscillations were associated with a
region of emerging and then canceling magnetic flux that resulted
in multiple activations and filament eruptions. We analyze twelve
separate oscillations that occur in a complex of filaments in the
active region over twelve days. Luna and Karpen (2012) model LALO
in filaments oscillations of magnetized filament plasma moving along
dipped magnetic field lines with gravity as a restoring force. Under
this model the period of these oscillations can be used to estimate
the curvature of the magnetic field in the location of the filament,
providing observationally derived values to compare with models of the
magnetic field in the active region corona. Periods ranged from 26-74
minutes, corresponding to magnetic field curvatures of about 20-130 Mm.
Title: Magnetic Structure of an Erupting Filament
Authors: Wang, Shuo; Jenkins, Jack M.; Martinez Pillet, Valentin;
Beck, Christian; Long, David M.; Prasad Choudhary, Debi; Muglach,
Karin; McAteer, James
Bibcode: 2020ApJ...892...75W
Altcode: 2020arXiv200202104W
The full 3D vector magnetic field of a solar filament prior to
eruption is presented. The filament was observed with the Facility
Infrared Spectropolarimeter at the Dunn Solar Telescope in the
chromospheric He I line at 10830 Å on 2017 May 29 and 30. We inverted
the spectropolarimetric observations with the Hanle and Zeeman Light
code to obtain the chromospheric magnetic field. A bimodal distribution
of field strength was found in or near the filament. The average field
strength was 24 Gauss, but prior to the eruption we find the 90th
percentile of field strength was 435 Gauss for the observations on May
29. The field inclination was about 67° from the solar vertical. The
field azimuth made an angle of about 47°-65° to the spine axis. The
results suggest an inverse configuration indicative of a flux rope
topology. He I intensity threads were found to be coaligned with the
magnetic field direction. The filament had a sinistral configuration
as expected for the southern hemisphere. The filament was stable on
2017 May 29 and started to rise during two observations on May 30,
before erupting and causing a minor coronal mass ejection. There
was no obvious change of the magnetic topology during the eruption
process. Such information on the magnetic topology of erupting filaments
could improve the prediction of the geoeffectiveness of solar storms.
Title: Forecasting the Ambient Solar Wind with Numerical
Models. II. An Adaptive Prediction System for Specifying Solar Wind
Speed near the Sun
Authors: Reiss, Martin A.; MacNeice, Peter J.; Muglach, Karin; Arge,
Charles N.; Möstl, Christian; Riley, Pete; Hinterreiter, Jürgen;
Bailey, Rachel L.; Weiss, Andreas J.; Owens, Mathew J.; Amerstorfer,
Tanja; Amerstorfer, Ute
Bibcode: 2020ApJ...891..165R
Altcode: 2020arXiv200309336R
The ambient solar wind flows and fields influence the complex
propagation dynamics of coronal mass ejections in the interplanetary
medium and play an essential role in shaping Earth's space weather
environment. A critical scientific goal in the space weather research
and prediction community is to develop, implement, and optimize
numerical models for specifying the large-scale properties of solar wind
conditions at the inner boundary of the heliospheric model domain. Here
we present an adaptive prediction system that fuses information from
in situ measurements of the solar wind into numerical models to better
match the global solar wind model solutions near the Sun with prevailing
physical conditions in the vicinity of Earth. In this way, we attempt
to advance the predictive capabilities of well-established solar wind
models for specifying solar wind speed, including the Wang-Sheeley-Arge
model. In particular, we use the Heliospheric Upwind eXtrapolation
(HUX) model for mapping the solar wind solutions from the near-Sun
environment to the vicinity of Earth. In addition, we present the newly
developed Tunable HUX (THUX) model, which solves the viscous form of the
underlying Burgers equation. We perform a statistical analysis of the
resulting solar wind predictions for the period 2006-2015. The proposed
prediction scheme improves all the investigated coronal/heliospheric
model combinations and produces better estimates of the solar wind
state at Earth than our reference baseline model. We discuss why this
is the case and conclude that our findings have important implications
for future practice in applied space weather research and prediction.
Title: Tracking supergranulation near the poles with SDO/HMI
Authors: Attié, R.; Kirk, M. S.; Tremblay, B.; Muglach, K.; Hess
Webber, S. A.; Pesnell, W. D.; Thompson, B. J.
Bibcode: 2019AGUFMSH13B..01A
Altcode:
Due to the spherical curvature of the Sun, solar observers suffer
from an increasing loss of resolution as we move away from the solar
equator. Thus knowledge of the photospheric flows near the poles
has eluded the scope of traditional flow tracking algorithms that
are using granules as tracers of the underlying flows. Using the new
"Balltracking" framework which we adapted to the observations from
SDO/HMI, we present an unprecedented analysis of the horizontal flow
fields at latitudes beyond +/- 60 degrees. The flow fields are derived
every 4 hours at a spatial resolution of 4 Mm. Using flow segmentation
techniques, we extract geometric and spectral information on the
supergranular cells and compare them with those of the supergranulation
at lower latitude. The correlation with the dynamics of moving magnetic
features is also investigated.
Title: Searching for a Boundary Layer as a Source of the Slow
Solar Wind
Authors: Ko, Y. K.; Muglach, K.; Riley, P.; Wang, Y. M.
Bibcode: 2019AGUFMSH41F3330K
Altcode:
Recent investigations in the solar wind plasma and magnetic field
characteristics indicate a likely existence of a "boundary layer"
where the slow solar wind originates from. Such a boundary layer
resides at the coronal hole boundary where the open field lines
emanating from it expand super-radially into the corona. We select two
adjacent coronal holes that are the sources of two consecutive solar
wind streams measured by ACE. One is a low-latitude extension of the
north polar coronal hole that past the central meridian on August 18,
2015, and the other is an equatorial coronal hole that past the central
meridian on August 20. We use data from SDO/AIA, SDO/HMI and Hinode/EIS
in combination with PFSS and 3D MHD models to investigate the evolution
of the coronal and magnetic field properties at the boundary of these
coronal holes and search for signatures of such a boundary layer.
Title: Assessing the uncertainty of coronal hole boundary locations
Authors: Reiss, M.; MacNeice, P. J.; Muglach, K.; Kirk, M. S.; Arge,
C. N.; Moestl, C.
Bibcode: 2019AGUFMSM31C3182R
Altcode:
The ambient solar wind flows, and the magnetic fields embedded within
it, are driven by the Sun's magnetic field. Thus, studying the magnetic
field configuration in the solar atmosphere is of key importance for
improving understanding and ultimately predicting Earth's space weather
environment. The configuration of open magnetic field lines, commonly
known as coronal holes, is especially important for predicting key
properties in the interplanetary space such as solar wind bulk speed,
magnetic field strength, and field orientation. In addition, the dynamic
evolution of coronal hole boundaries is understood as having a critical
role in the origin of the slow solar wind. Despite the importance of
these features there has been no systematic analysis of the reliability
of established coronal hole detection techniques. The objectives of
this action team are threefold: First, to study and compare different
coronal hole detection techniques with open communication with the space
weather community. Second, to develop strategies to quantitatively
assess the spatial and temporal uncertainty of coronal hole boundary
locations. Third, to use this information to further improve the
predictive capabilities of numerical models of the evolving ambient
solar wind. We will discuss challenges towards the realization of
these objectives and present the current status and the roadmap of
the action team.
Title: The life of coronal bright points
Authors: Muglach, Karin; Leisner, Andrew
Bibcode: 2019AAS...23411703M
Altcode:
Coronal bright points are small-scale magnetic regions found all
over the solar disk. They are visible in coronal emission lines which
sample plasma at around 1-2 MK. In this study we follow the complete
lifetime of several coronal bright points, from the time they appear
in the SDO/AIA coronal filtergrams to the time they fade again into
the quiet solar background emission. In addition to the hot coronal
emission, lower temperature chromospheric filtergrams (e.g. AIA 304 Å)
sometimes show the formation of dark absorption structures similar to
filaments. From SDO/HMI we can get the accompanying evolution of the
photospheric magnetic flux density and also calculate the plane-of-sky
plasma flow field using local correlation tracking. Most of the coronal
bright points show some jet activity during their lifetime and these
data allow to us to study both the energy buildup of the coronal bright
point and the initiation of the jets.
Title: Precursors of magnetic flux emergence in the moat flows of
active region AR12673
Authors: Attie, Raphael; Kirk, Michael; Thompson, Barbara; Muglach,
Karin; Norton, Aimee
Bibcode: 2018csc..confE..34A
Altcode:
We report on observations of magnetic disturbances in active region
AR12673 between Sep. 1 and Sep. 3, 2017 seen as a disruption of the moat
flow several hours before the onset of strong flux emergence near the
main sunspot. The moat flow is commonly known as a radially oriented
strong outflow of photospheric plasma surrounding sunspots which ends
abruptly and thus shapes an annular pattern around the penumbra. Using
highly accurate methods of tracking this photospheric flow applied
to SDO/HMI data, we are able to describe the evolution of the moat
surrounding the main sunspot of AR 12673. We find that several hours
before the emergence of strong magnetic flux near the main sunspot the
moat boundaries are broken at these very same locations. This behavior
is observed both on Sep. 1st and Sep. 3rd. There is no such behavior
observed in the absence of flux emergence. These observational results
pose the question of how often they occur in other active regions and
whether the disruption of the moat flow might be, like in this case,
an indication of impending enhanced magnetic activity or simply a
coincidental event.
Title: GONG Catalog of Solar Filament Oscillations Near Solar Maximum
Authors: Luna, M.; Karpen, J.; Ballester, J. L.; Muglach, K.; Terradas,
J.; Kucera, T.; Gilbert, H.
Bibcode: 2018ApJS..236...35L
Altcode: 2018arXiv180403743L
We have cataloged 196 filament oscillations from the Global Oscillation
Network Group Hα network data during several months near the maximum
of solar cycle 24 (2014 January-June). Selected examples from the
catalog are described in detail, along with our statistical analyses of
all events. Oscillations were classified according to their velocity
amplitude: 106 small-amplitude oscillations (SAOs), with velocities
<10 {km} {{{s}}}-1, and 90 large-amplitude oscillations
(LAOs), with velocities >10 {km} {{{s}}}-1. Both SAOs
and LAOs are common, with one event of each class every two days on the
visible side of the Sun. For nearly half of the events, we identified
their apparent trigger. The period distribution has a mean value of
58 ± 15 minutes for both types of oscillations. The distribution
of the damping time per period peaks at τ/P = 1.75 and 1.25 for
SAOs and LAOs, respectively. We confirmed that LAO damping rates
depend nonlinearly on the oscillation velocity. The angle between the
direction of motion and the filament spine has a distribution centered
at 27° for all filament types. This angle agrees with the observed
direction of filament-channel magnetic fields, indicating that most
of the cataloged events are longitudinal (i.e., undergo field-aligned
motions). We applied seismology to determine the average radius of
curvature in the magnetic dips, R ≈ 89 Mm, and the average minimum
magnetic field strength, B ≈ 16 G. The catalog is available to the
community online and is intended to be expanded to cover at least 1
solar cycle.
Title: Advance detection of strong photospheric flux emergence
revealed by disruption of moat flows
Authors: Attié, Raphael; Thompson, Barbara J.; Muglach, Karin;
Norton, Aimee Ann
Bibcode: 2018tess.conf30602A
Altcode:
We report on observations of precursors of magnetic disturbances in AR
12673 seen as a disruption of the moat flow several hours before the
onset of strong flux emergence near the main sunspot. The moat flow is
commonly known as a radially oriented strong outflow of photospheric
plasma surrounding sunspots which ends abruptly and thus shapes an
annular pattern around the penumbra. Using highly accurate methods of
tracking this photospheric flow applied to SDO/HMI data, we are able
to describe the evolution of the moat surrounding the main sunspot of
AR 12673. We find that several hours before the emergence of strong
magnetic flux near the main sunspot the moat boundaries are broken at
these very same locations. Because we detect this specific behavior both
on Sep. 1st and Sep. 3rd, our observations suggest that the disruption
of the moat flow is a precursor of the enhanced magnetic activity
which, in this case, led to the strong flaring activity starting on
Sep 6th. This study is part of a broader statistical survey that
aims at characterizing emerging active regions. In light of these
new observations, our survey will also determine to what extent such
a disruption of the moat flow is followed by strong flux emergence
around sunspots, i.e., is this a peculiar response specific to AR
12673, or is it a characteristic disturbance defining a subset of
active regions prone to flaring activity?
Title: Space Weather Research and Forecasting Capabilities at the
Community Coordinated Modeling Center (CCMC)
Authors: Collado-Vega, Y. M.; Kuznetsova, M.; Mays, L.; Pulkkinen,
A.; Zheng, Y.; Muglach, K.; Thompson, B.; Chulaki, A.; Taktakishvili,
A.; CCMC Team
Bibcode: 2018LPICo2063.3090C
Altcode:
The Community Coordinated Modeling Center (CCMC) supports and enables
the research and development of the latest and future space weather
models and facilitates the deployment of the latest advances in research
of space weather operations.
Title: CCMC: bringing space weather awareness to the next generation
Authors: Chulaki, A.; Muglach, K.; Zheng, Y.; Mays, M. L.; Kuznetsova,
M. M.; Taktakishvili, A.; Collado-Vega, Y. M.; Rastaetter, L.; Mendoza,
A. M. M.; Thompson, B. J.; Pulkkinen, A. A.; Pembroke, A. D.
Bibcode: 2017AGUFMSH21A2635C
Altcode:
Making space weather an element of core education is critical for
the future of the young field of space weather. Community Coordinated
Modeling Center (CCMC) is an interagency partnership established to
aid the transition of modern space science models into space weather
forecasting while supporting space science research. Additionally, over
the past ten years it has established itself as a global space science
education resource supporting undergraduate and graduate education and
research, and spreading space weather awareness worldwide. A unique
combination of assets, capabilities and close ties to the scientific
and educational communities enable our small group to serve as a hub
for rising generations of young space scientists and engineers. CCMC
offers a variety of educational tools and resources publicly available
online and providing access to the largest collection of modern space
science models developed by the international research community. CCMC
has revolutionized the way these simulations are utilized in
classrooms settings, student projects, and scientific labs. Every
year, this online system serves hundreds of students, educators and
researchers worldwide. Another major CCMC asset is an expert space
weather prototyping team primarily serving NASA's interplanetary space
weather needs. Capitalizing on its unique capabilities and experiences,
the team also provides in-depth space weather training to hundreds of
students and professionals. One training module offers undergraduates an
opportunity to actively engage in real-time space weather monitoring,
analysis, forecasting, tools development and research, eventually
serving remotely as NASA space weather forecasters. In yet another
project, CCMC is collaborating with Hayden Planetarium and Linkoping
University on creating a visualization platform for planetariums (and
classrooms) to provide simulations of dynamic processes in the large
domain stretching from the solar corona to the Earth's upper atmosphere,
for near real-time and historical space weather events.
Title: Large-Amplitude Oscillations as a Probe of Solar Prominences
Authors: Luna Bennasar, M.; Karpen, J. T.; Gilbert, H. R.; Kucera,
T. A.; Muglach, K.
Bibcode: 2016AGUFMSH41E..01L
Altcode:
Large-amplitude oscillations in prominences are among the most
spectacular phenomena of the solar atmosphere. Such an oscillations
involve motions with velocities above 20 km/s, and large portions
of the filament that move in phase. These are triggered by energetic
disturbances as flares and jets. These oscillations are an excellent
tool to probe the not directly measurable filament morphology. In
addition, the damping of these motions can be related with the process
of evaporation of chromospheric plasma associated to coronal heating. In
these talk I will show recent observational and theoretical progress
on large-amplitude seismology on prominences.
Title: The Photospheric Footprints of Coronal Hole Jets
Authors: Muglach, Karin
Bibcode: 2016usc..confE...6M
Altcode:
Coronal jets are transient, collimated ejections of plasma that are
a common feature of solar X-ray and EUV image sequences. Of special
interest are jets in coronal holes due to their possible contribution
to the solar wind outflow. From a sample of 35 jet events I will
investigate the photospheric signatures at the footpoints of these
jets. White light images from the HMI on board SDO are used to derive
the plane-of-sky flow field using local correlation tracking, and
HMI magnetograms show the development of the magnetic flux. Both
the evolution of the magnetic field and flows allow one to study
the photospheric driver of these jets. One particularly interesting
example demonstrates that the untwisting jet involves a tiny filament
whose eruption is most likely triggered by the emergence of a small
magnetic bipole close to one of its legs.
Title: Correlation of Coronal Plasma Properties and Solar Magnetic
Field in a Decaying Active Region
Authors: Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren,
Harry P.; Ugarte-Urra, Ignacio
Bibcode: 2016ApJ...826..126K
Altcode:
We present the analysis of a decaying active region observed by
the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We
investigated the temporal evolution of its structure exhibited by plasma
at temperatures from 300,000 to 2.8 million degrees, and derived the
electron density, differential emission measure, effective electron
temperature, and elemental abundance ratios of Si/S and Fe/S (as a
measure of the First Ionization Potential (FIP) Effect). We compared
these coronal properties to the temporal evolution of the photospheric
magnetic field strength obtained from the Solar and Heliospheric
Observatory Michelson Doppler Imager magnetograms. We find that, while
these coronal properties all decreased with time during this decay
phase, the largest change was at plasma above 1.5 million degrees. The
photospheric magnetic field strength also decreased with time but
mainly for field strengths lower than about 70 Gauss. The effective
electron temperature and the FIP bias seem to reach a “basal” state
(at 1.5 × 106 K and 1.5, respectively) into the quiet Sun
when the mean photospheric magnetic field (excluding all areas <10 G)
weakened to below 35 G, while the electron density continued to decrease
with the weakening field. These physical properties are all positively
correlated with each other and the correlation is the strongest in
the high-temperature plasma. Such correlation properties should be
considered in the quest for our understanding of how the corona is
heated. The variations in the elemental abundance should especially
be considered together with the electron temperature and density.
Title: Converging Supergranular Flows and the Formation of Coronal
Plumes
Authors: Wang, Y. -M.; Warren, H. P.; Muglach, K.
Bibcode: 2016ApJ...818..203W
Altcode:
Earlier studies have suggested that coronal plumes are energized
by magnetic reconnection between unipolar flux concentrations and
nearby bipoles, even though magnetograms sometimes show very little
minority-polarity flux near the footpoints of plumes. Here we use
high-resolution extreme-ultraviolet (EUV) images and magnetograms
from the Solar Dynamics Observatory (SDO) to clarify the relationship
between plume emission and the underlying photospheric field. We
find that plumes form where unipolar network elements inside coronal
holes converge to form dense clumps, and fade as the clumps disperse
again. The converging flows also carry internetwork fields of both
polarities. Although the minority-polarity flux is sometimes barely
visible in the magnetograms, the corresponding EUV images almost
invariably show loop-like features in the core of the plumes, with the
fine structure changing on timescales of minutes or less. We conclude
that the SDO observations are consistent with a model in which plume
emission originates from interchange reconnection in converging flows,
with the plume lifetime being determined by the ∼1 day evolutionary
timescale of the supergranular network. Furthermore, the presence of
large EUV bright points and/or ephemeral regions is not a necessary
precondition for the formation of plumes, which can be energized
even by the weak, mixed-polarity internetwork fields swept up by
converging flows.
Title: A coronal hole jet observed with Hinode and the Solar Dynamics
Observatory
Authors: Young, Peter R.; Muglach, Karin
Bibcode: 2014PASJ...66S..12Y
Altcode: 2014PASJ..tmp..106Y; 2014arXiv1402.4389Y; 2014PASJ...66..S12Y
A small blowout jet was observed at the boundary of the south polar
coronal hole on 2011 February 8 at around 21:00 UT. Images from
the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics
Observatory (SDO) revealed an expanding loop rising from one footpoint
of a compact, bipolar bright point. Magnetograms from the Helioseismic
Magnetic Imager (HMI) on board SDO showed that the jet was triggered
by the cancelation of a parasitic positive polarity feature near
the negative pole of the bright point. The jet emission was present
for 25 min and it extended 30 Mm from the bright point. Spectra from
the Extreme Ultraviolet Imaging Spectrometer on board Hinode yielded
a temperature and density of 1.6 MK and 0.9-1.7 × 108
cm-3 for the ejected plasma. Line-of-sight velocities reached
up to 250 km s-1 and were found to increase with height,
suggesting plasma acceleration within the body of the jet. Evidence
was found for twisting motions within the jet based on variations of
the line-of-sight velocities across the jet width. The derived angular
speed was in the range (9-12) × 10-3 rad s-1,
consistent with previous measurements from jets. The density of the
bright point was 7.6 × 108 cm-3, and the peak
of the bright point's emission measure occurred at 1.3 MK, with no
plasma above 3 MK.
Title: NASA Space Weather Research Center: Addressing the Unique
Space Weather Needs of NASA Robotic Missions
Authors: Zheng, Y.; Pulkkinen, A. A.; Kuznetsova, M. M.; Maddox,
M. M.; Mays, M. L.; Taktakishvili, A.; Chulaki, A.; Thompson, B. J.;
Collado-Vega, Y. M.; Muglach, K.; Evans, R. M.; Wiegand, C.; MacNeice,
P. J.; Rastaetter, L.
Bibcode: 2014AGUFMSM31A4151Z
Altcode:
The Space Weather Research Center (SWRC) has been providing space
weather monitoring and forecasting services to NASA's robotic
missions since its establishment in 2010. Embedded within the Community
Coordinated Modeling Center (CCMC) (see Maddox et al. in Session IN026)
and located at NASA Goddard Space Flight Center, SWRC has easy access
to state-of-the-art modeling capabilities and proximity to space science
and research expertise. By bridging space weather users and the research
community, SWRC has been a catalyst for the efficient transition from
research to operations and operations to research. In this presentation,
we highlight a few unique aspects of SWRC's space weather services,
such as addressing space weather throughout the solar system, pushing
the frontier of space weather forecasting via the ensemble approach,
providing direct personnel and tool support for spacecraft anomaly
resolution, prompting development of multi-purpose tools and knowledge
bases (see Wiegand et al. in the same session SM004), and educating
and engaging the next generation of space weather scientists.
Title: The Interaction of Solar Eruptions and Large-Scale Coronal
Structures Revealed Through Modeling and Observational Analysis
Authors: Evans, R. M.; Savcheva, A. S.; Zink, J. L.; Muglach, K.;
Kozarev, K. A.; Opher, M.; van der Holst, B.
Bibcode: 2014AGUFMSH11D..05E
Altcode:
We use numerical and observational approaches to explore how
the interaction of a coronal mass ejection (CME) with preexisting
structures in the solar atmosphere influences its evolution and space
weather effects. We study two aspects of CME evolution: deflection of
the CME's propagation direction, and expansion. First, we perform a
statistical study of the influence of coronal holes on CME trajectories
for more than 50 events during years 2010-2014. Second, we use the Space
Weather Modeling Framework (SWMF) to model CME propagation in the Alfven
Wave Solar Model (AWSoM), which includes a sophisticated treatment
of the physics of coronal heating and solar wind acceleration. The
major progress in these simulations is that the initial conditions
of the eruptions are highly data-constrained. From the simulations,
we determine the CME's trajectory and expansion. We calculate the
pile-up of material along the front and sides of a CME due to its
expansion, and constrain the properties of the pile-up under a range
of conditions. Finally, we will discuss the connection between these
plasma density structures and the acceleration of protons to energies
relevant to space weather.
Title: A Statistical Study of Coronal Mass Ejections and Coronal
Holes during 2010-2014
Authors: Zink, J. L.; Evans, R. M.; Muglach, K.
Bibcode: 2014AGUFMSH53A4199Z
Altcode:
When analyzing CMEs in real time for space weather forecasting,
a lack of sufficient coronagraph images can make it difficult to
determine the CME's location. In these cases, usually the location
of significant disk signatures (for example, an associated flare)
is used to estimate the CME's location. Although this assumption
seems reasonable, observational and numerical studies have shown
that CME locations can deviate by ten or more degrees from the source
location close to the solar surface. In this work, we present a study
of more than 50 events during 2010-2014 covering a range of CME speeds,
widths, and source locations. We use the CCMC's space weather Database
Of Notifications, Knowledge, and Information (DONKI) to select events,
and use the SWPC's CME Analysis Tool to measure CMEs in the SOHO/LASCO
and STEREO/SECCHI coronagraph images. We find a range of deflections,
from less than 5 degrees to more than 15 degrees. It has been proposed
that CMEs deflect during propagation due to interactions with other
large-scale structures such as coronal holes, streamers, current
sheets, and other CMEs. In this study we focus on the influence of
coronal holes. We use a combination of SDO/AIA and SECCHI/EUVI images
to locate coronal holes near the CME source locations. We present the
calculated CME deflection angles as a function of height in the corona,
average speed, average width, and coronal hole properties. The goal
of this study is to determine appropriate ranges of latitudes and
longitudes that can be used in CME ensemble modeling. This requires
that coronal hole observations are more systematically incorporated
in real time CME analysis for space weather forecasting. J. Zink
conducted this research with support from the Undergraduate Research
Scholars Program at GMU. R. Evans is supported through an appointment
to the NASA Postdoctoral Program at GSFC, administered by Oak Ridge
Associated Universities through a contract with NASA.
Title: Observations and Implications of Large-Amplitude Longitudinal
Oscillations in a Solar Filament
Authors: Karpen, J. T.; Luna Bennasar, M.; Knizhnik, K. J.; Muglach,
K.; Gilbert, H. R.; Kucera, T. A.; Uritsky, V. M.; Asfaw, T. T.
Bibcode: 2014AGUFMSH51C4171K
Altcode:
On 20 August 2010 an energetic disturbance triggered large-amplitude
longitudinal oscillations in a large fraction of a nearby filament. The
triggering mechanism appears to be episodic jets connecting the
energetic event with the filament threads. We analyzed this periodic
motion to characterize the underlying physics of the oscillation as
well as the filament properties. The results support our previous
theoretical conclusions that the restoring force of large-amplitude
longitudinal oscillations is solar gravity, and the damping mechanism
is the ongoing accumulation of mass onto the oscillating threads. Based
on our previous work, we used the fitted parameters to determine the
magnitude and radius of curvature of the dipped magnetic field along
the filament, as well as the mass accretion rate onto the filament
threads. These derived properties are nearly uniform along the filament,
indicating a remarkable degree of homogeneity throughout the filament
channel. Moreover, the estimated mass accretion rate implies that the
footpoint heating responsible for the thread formation, according to
the thermal nonequilibrium model, agrees with previous coronal heating
estimates. We also estimated the magnitude of the energy released in
the nearby event by studying the dynamic response of the filament
threads, and concluded that the initiating event is likely to be a
microflare. Using a nonlinear force-free field extrapolation of the
photospheric magnetogram to estimate the coronal magnetic structure,
we determined the possible connectivity between the jet source and the
oscillating prominence segments. We will present the results of this
investigation and discuss their implications for filament structure
and heating. This work was supported by NASA's H-SR program.
Title: Solar Dynamics Observatory and Hinode Observations of a
Blowout Jet in a Coronal Hole
Authors: Young, P. R.; Muglach, K.
Bibcode: 2014SoPh..289.3313Y
Altcode: 2013arXiv1309.7324Y; 2014SoPh..tmp...24Y
A blowout jet occurred within the south coronal hole on 9 February
2011 at 09:00 UT and was observed by the Atmospheric Imaging Assembly
(AIA) and Helioseismic and Magnetic Imager (HMI) onboard the Solar
Dynamics Observatory, and by the EUV Imaging Spectrometer (EIS)
and X-Ray Telescope (XRT) onboard the Hinode spacecraft during
coronal-hole monitoring performed as part of Hinode Operations
Program No. 177. Images from AIA show expanding hot and cold loops
from a small bright point with plasma ejected in a curtain up to 30 Mm
wide. The initial intensity front of the jet had a projected velocity
of 200 km s−1, and the line-of-sight (LOS) velocities
measured by EIS are between 100 and 250 km s−1. The LOS
velocities increased along the jet, implying that an acceleration
mechanism operates within the body of the jet. The jet plasma had a
density of 2.7×108 cm−3 and a temperature of
1.4 MK. During the event a number of bright kernels were seen at the
base of the bright point. The kernels have sizes of ≈ 1000 km, are
variable in brightness, and have lifetimes of 1 - 15 minutes. An XRT
filter ratio yields temperatures of 1.5 - 3.0 MK for the kernels. The
bright point existed for at least ten hours, but disappeared within
two hours after the jet, which lasted for 30 minutes. HMI data reveal
converging photospheric flows at the location of the bright point,
and the mixed-polarity magnetic flux canceled over a period of four
hours on either side of the jet.
Title: Temporal Evolution of Solar Wind Ion Composition and their
Source Coronal Holes During the Declining Phase of Cycle 23
Authors: Ko, Yuan-Kuen; Muglach, Karin; Wang, Yi-Ming; Young, Peter
R.; Lepri, Susan T.
Bibcode: 2014AAS...22432366K
Altcode:
We present our analysis of the temporal trend in the solar wind
(SW) ion charge states and the properties in the associated source
coronal holes (CHs) during the declining phase of solar cycle 23. We
find that the SW ions exhibit a trend of decreasing ionization state
with time, consistent with previous studies. However the rate of
decrease is different between the slow and fast SW. The photospheric
magnetic field strength in both regions is found to exhibit similar
trend of decrease with time. On the other hand, the temporal trend is
different in the line emissions from different layers of the atmosphere
(chromosphere, transit region and corona). Within each CH, the coronal
emission generally increases toward the boundary of the CH as the
underlying photospheric magnetic field strength increases, the net
unbalanced field strength decreases and the magnetic field becomes
less unipolar. But the coronal emission averaged over the entire CH
area does not have appreciable change with time. We find that ions
which freeze-in at lower altitude in the corona, such as C and O ions,
have a stronger correlation between their ionization state and the
average photospheric magnetic field strength in the slow SW, while Fe
ions which freeze-in at higher altitude have a stronger correlation
in the fast SW. Our analyses provide important clues for how the SW is
formed, heated and accelerated in response to the long-term evolution
of the solar magnetic field at its source coronal hole.
Title: Observations and Implications of Large-Amplitude
LongitudinalOscillations in a Solar Filament
Authors: Karpen, Judith T.; Luna, Manuel; Knizhnik, Kalman J.; Muglach,
Karin; Gilbert, Holly; Kucera, Therese A.; Uritsky, Vadim
Bibcode: 2014AAS...22411106K
Altcode:
On 20 August 2010 an energetic disturbance triggered large-amplitude
longitudinal oscillations in a large fraction of a nearby filament. The
triggering mechanism appears to be episodic jets connecting the
energetic event with the filament threads. We analyzed this periodic
motion to characterize the underlying physics of the oscillation as
well as the filament properties. The results support our previous
theoretical conclusions that the restoring force of large-amplitude
longitudinal oscillations is solar gravity, and the damping mechanism
is the ongoing accumulation of mass onto the oscillating threads. Based
on our previous work, we used the fitted parameters to determine the
magnitude and radius of curvature of the dipped magnetic field along
the filament, as well as the mass accretion rate onto the filament
threads. These derived properties are nearly uniform along the filament,
indicating a remarkable degree of homogeneity throughout the filament
channel. Moreover, the estimated mass accretion rate implies that the
footpoint heating responsible for the thread formation, according to
the thermal nonequilibrium model, agrees with previous coronal heating
estimates. We also estimated the magnitude of the energy released in
the nearby event by studying the dynamic response of the filament
threads, and concluded that the initiating event is likely to be a
microflare. We will present the results of this investigation and
discuss their implications for filament structure and heating. This
work was supported by NASA’s H-SR program.
Title: Temporal Evolution of Solar Wind Ion Composition and
their Source Coronal Holes during the Declining Phase of Cycle
23. I. Low-latitude Extension of Polar Coronal Holes
Authors: Ko, Yuan-Kuen; Muglach, Karin; Wang, Yi-Ming; Young, Peter
R.; Lepri, Susan T.
Bibcode: 2014ApJ...787..121K
Altcode:
We analyzed 27 solar wind (SW) intervals during the declining phase
of cycle 23, whose source coronal holes (CHs) can be unambiguously
identified and are associated with one of the polar CHs. We found that
the SW ions have a temporal trend of decreasing ionization state,
and such a trend is different between the slow and fast SW. The
photospheric magnetic field, both inside and at the outside boundary
of the CH, also exhibits a trend of decrease with time. However,
EUV line emissions from different layers of the atmosphere exhibit
different temporal trends. The coronal emission inside the CH generally
increases toward the CH boundary as the underlying field increases in
strength and becomes less unipolar. In contrast, this relationship is
not seen in the coronal emission averaged over the entire CH. For C
and O SW ions that freeze-in at lower altitude, stronger correlation
between their ionization states and field strength (both signed and
unsigned) appears in the slow SW, while for Fe ions that freeze-in
at higher altitude, stronger correlation appears in the fast SW. Such
correlations are seen both inside the CH and at its boundary region. On
the other hand, the coronal electron temperature correlates well with
the SW ion composition only in the boundary region. Our analyses,
although not able to determine the likely footpoint locations of the
SW of different speeds, raise many outstanding questions for how the
SW is heated and accelerated in response to the long-term evolution
of the solar magnetic field.
Title: Photospheric Signatures of Coronal Hole Jets
Authors: Muglach, Karin; Young, Peter R.
Bibcode: 2014AAS...22432333M
Altcode:
Coronal jets are transient, collimated ejections of plasma that are
a common feature of solar X-ray and EUV image sequences. Of special
interest is the contribution that coronal hole jets make to the
solar wind outflow. A new class of coronal hole jets, termed "dark
jets", has been identified with the EUV Imaging Spectrometer (EIS)
on board Hinode. The jets are identified in EUV spectral lines with
line-of-sight velocities of 50-100 km/s and enhanced line widths, yet
they show little or no intensity signature in image sequences from the
Atmospheric Imaging Assembly on board the Solar Dynamics Observatory
(SDO) or the X-Ray Telescope on board Hinode.In this contribution we
will investigate the photosphere at the footpoint of these jets. White
light images from the Helioseismic Magnetic Imager (HMI) on board SDO
are used to derive the plane-of-sky flow field using local correlation
tracking, and HMI magnetograms show the evolution of the magnetic
flux. Both the evolution of the magnetic field and flows allow us to
study the photospheric driver of these jets.
Title: Characterization of Near-Sun Coronal Mass Ejection Deflection
using Coronagraph Image Sequences
Authors: Zink, Jenna; Evans, Rebekah M.; Muglach, Karin
Bibcode: 2014shin.confE.167Z
Altcode:
When analyzing CMEs in real time for space weather forecasting,
a lack of sufficient coronagraph images can make it difficult to
determine the CME"s longitude. In these cases, usually the location
of significant disk signatures (for example, an associated flare)
is used to estimate the CME"s location. Although this assumption
seems reasonable, observational and numerical studies have shown
that CME locations can deviate by ten or more degrees from the source
location close to the solar surface. An accurate determination of the
CME location is essential for CME arrival predictions. For example,
results from CME ensemble modeling carried out by the NASA/GSFC Space
Weather Research Center have shown that a variation of a CME"s position
by 10 degrees can change the arrival time at 1 AU by 8 hours.
Title: Observations and Implications of Large-amplitude Longitudinal
Oscillations in a Solar Filament
Authors: Luna, M.; Knizhnik, K.; Muglach, K.; Karpen, J.; Gilbert,
H.; Kucera, T. A.; Uritsky, V.
Bibcode: 2014ApJ...785...79L
Altcode: 2014arXiv1403.0381L
On 2010 August 20, an energetic disturbance triggered large-amplitude
longitudinal oscillations in a nearby filament. The triggering mechanism
appears to be episodic jets connecting the energetic event with the
filament threads. In the present work, we analyze this periodic motion
in a large fraction of the filament to characterize the underlying
physics of the oscillation as well as the filament properties. The
results support our previous theoretical conclusions that the restoring
force of large-amplitude longitudinal oscillations is solar gravity,
and the damping mechanism is the ongoing accumulation of mass onto
the oscillating threads. Based on our previous work, we used the
fitted parameters to determine the magnitude and radius of curvature
of the dipped magnetic field along the filament, as well as the mass
accretion rate onto the filament threads. These derived properties are
nearly uniform along the filament, indicating a remarkable degree of
cohesiveness throughout the filament channel. Moreover, the estimated
mass accretion rate implies that the footpoint heating responsible
for the thread formation, according to the thermal nonequilibrium
model, agrees with previous coronal heating estimates. We estimate the
magnitude of the energy released in the nearby event by studying the
dynamic response of the filament threads, and discuss the implications
of our study for filament structure and heating.
Title: Evidence for Two Separate Heliospheric Current Sheets of
Cylindrical Shape During Mid-2012
Authors: Wang, Y. -M.; Young, P. R.; Muglach, K.
Bibcode: 2014ApJ...780..103W
Altcode:
During the reversal of the Sun's polar fields at sunspot maximum,
outward extrapolations of magnetograph measurements often predict the
presence of two or more current sheets extending into the interplanetary
medium, instead of the single heliospheric current sheet (HCS) that
forms the basis of the standard "ballerina skirt" picture. By comparing
potential-field source-surface models of the coronal streamer belt
with white-light coronagraph observations, we deduce that the HCS
was split into two distinct structures with circular cross sections
during mid-2012. These cylindrical current sheets were centered near
the heliographic equator and separated in longitude by roughly 180° a
corresponding four-sector polarity pattern was observed at Earth. Each
cylinder enclosed a negative-polarity coronal hole that was identifiable
in extreme ultraviolet images and gave rise to a high-speed stream. The
two current sheet systems are shown to be a result of the dominance
of the Sun's nonaxisymmetric quadrupole component, as the axial dipole
field was undergoing its reversal during solar cycle 24.
Title: Large-amplitude longitudinal oscillations in solar prominences
Authors: Luna, Manuel; Karpen, Judith; Díaz, Antonio; Knizhnik,
Kalman; Muglach, Karin; Gilbert, Holly; Kucera, Therese
Bibcode: 2014IAUS..300..155L
Altcode:
Large-amplitude longitudinal (LAL) prominence oscillations consist of
periodic mass motions along a filament axis. The oscillations appear
to be triggered by an energetic event, such as a microflare, subflare,
or small C-class flare, close to one end of the filament. Observations
reveal speeds of several tens to 100 km/s, periods of order 1 hr,
damping times of a few periods, and displacements equal to a significant
fraction of the prominence length. We have developed a theoretical model
to explain the restoring force and the damping mechanism. Our model
demonstrates that the main restoring force is the projected gravity in
the flux tube dips where the threads oscillate. Although the period
is independent of the tube length and the constantly growing mass,
the motions are strongly damped by the steady accretion of mass onto
the threads. We conclude that the LAL movements represent a collective
oscillation of a large number of cool, dense threads moving along
dipped flux tubes, triggered by a nearby energetic event. Our model
yields a powerful seismological method for constraining the coronal
magnetic field strength and radius of curvature at the thread locations.
Title: Observational Study of Large Amplitude Longitudinal
Oscillations in a Solar Filament
Authors: Knizhnik, Kalman; Luna, Manuel; Muglach, Karin; Gilbert,
Holly; Kucera, Therese; Karpen, Judith
Bibcode: 2014IAUS..300..428K
Altcode: 2013arXiv1310.7657K
On 20 August 2010 an energetic disturbance triggered damped
large-amplitude longitudinal (LAL) oscillations in almost an entire
filament. In the present work we analyze this periodic motion in
the filament to characterize the damping and restoring mechanism of
the oscillation. Our method involves placing slits along the axis
of the filament at different angles with respect to the spine of the
filament, finding the angle at which the oscillation is clearest, and
fitting the resulting oscillation pattern to decaying sinusoidal and
Bessel functions. These functions represent the equations of motion
of a pendulum damped by mass accretion. With this method we determine
the period and the decaying time of the oscillation. Our preliminary
results support the theory presented by Luna and Karpen (2012) that
the restoring force of LAL oscillations is solar gravity in the tubes
where the threads oscillate, and the damping mechanism is the ongoing
accumulation of mass onto the oscillating threads. Following an earlier
paper, we have determined the magnitude and radius of curvature of
the dipped magnetic flux tubes hosting a thread along the filament,
as well as the mass accretion rate of the filament threads, via the
fitted parameters.
Title: A Spectroscopic Survey of Coronal Hole Jets
Authors: Young, Peter R.; Muglach, K.
Bibcode: 2013SPD....44...19Y
Altcode:
Coronal hole jets have been suggested to make a significant contribution
to the solar wind, but spectroscopic measurements - which provide
the best means of measuring the mass flux - have been rare due to
the difficulty of capturing jets with narrow slit spectrometers. A
continuous two day coronal hole measurement made with the Hinode/EIS
instrument is reported, which has revealed over 30 jets seen in
the coronal Fe XII 195.12 (1.5 MK) emission line. More than half of
the events have no clear signature in SDO/AIA or Hinode/XRT images
and thus represent a separate class of jet events not previously
reported. The jets show a wide range of morphologies, ranging from
classic columnar features to mini-CME events. Statistics of the events
will be presented: their relation to bright points and the coronal hole
boundary; durations; and repeated occurrence. Velocity, density and
temperature measurements derived from the EIS spectra will be presented,
and mass flux estimated. The photospheric signatures of the jets,
as determined from SDO/HMI, will be shown in a separate presentation
(Muglach & Young).
Title: Photospheric signatures of coronal hole jets
Authors: Muglach, Karin; Young, P. R.
Bibcode: 2013SPD....44...20M
Altcode:
Jets in EUV and X-ray images have been observed for several
decades. Many of them originate in coronal holes which have received
special interest as possible contributors to the solar wind. A new
class of CH jets are observed with Hinode/EIS which show pronounced
signatures in EUV spectral lines. Coronal velocities of up to 200 km/s
and enhancements in line width are measured. On the other hand these
jets are hardly visible in imaging data like SDO/AIA and Hinode/XRT
(see contribution by Young and Muglach). In this contribution we
will investigate the photospheric signatures at the footpoint of
these jets. We use SDO/HMI magnetograms to show the evolution of the
magnetic flux. From SDO white light images we derive the plane-of-sky
flow field using local correlation tracking. Both the evolution of
the magnetic field and the flows allow us to study the photospheric
drivers of these jets.
Title: Transient Brightenings Along Filament Channels as Observed
with SDO/AIA and HMI
Authors: Muglach, Karin; Wang, Y.
Bibcode: 2013SPD....4410503M
Altcode:
Filament channels coincide with large-scale polarity inversion lines of
the photospheric magnetic field, where flux cancellation continually
takes place. High-cadence Solar Dynamics Observatory (SDO) images
recorded in He II 30.4 nm and Fe IX 17.1 nm in August 2010 reveal
numerous transient brightenings occurring along the edge of a filament
channel within a decaying active region, where SDO line-of-sight
magnetograms show strong opposite-polarity flux in close contact. The
brightenings are elongated along the direction of the filament
channel, with linear extents of several arcseconds, and typically
last a few minutes; they sometimes have the form of multiple two-sided
ejections with speeds on the order of 100 km/s. Remarkably, some of the
brightenings rapidly develop into larger scale events, forming sheetlike
structures that are eventually torn apart by the diverging flows in the
filament channel and ejected in opposite directions. In some cases,
the flow patterns that develop in the channel may bring successive
horizontal loops together and cause a cascade to larger scales. One
of these brightening events was the initiation of a large-amplitude
longitudinal oscillation of the filament. We interpret the brightenings
as resulting from reconnections among filament-channel field lines
having one footpoint located in the region of canceling flux.
Title: The velocity signature of coronal jets as observed with
Hinode/EIS
Authors: Muglach, K.; Young, P. R.
Bibcode: 2013enss.confE..59M
Altcode:
In this contribution we show preliminary results of a study of jets
in coronal holes. We use Hinode/EIS to investigate the spectroscopic
signatures of the jets and SDO/AIA and HMI to derive additional
information on the plasma and magnetic field evolution. EIS was
scanning a low latitude coronal hole and tracking it for about 2
days as it rotated over the solar disk. The coronal jets are best
revealed through Doppler and line width maps of Fe XII 195.1 A (formed
at 1.5 MK), and have sizes of 10-100 arcsec. Higher spatial and time
resolution is provided by SDO: coronal and chromospheric images from
AIA show the time evolution of the jet and line-of-sight magnetograms
show the evolution of the magnetic footpoints of the jet. We present
several examples of these extended jets and describe their properties
as derived from the diagnostics we have available.
Title: Transient Brightenings Associated with Flux Cancellation
along a Filament Channel
Authors: Wang, Y. -M.; Muglach, K.
Bibcode: 2013ApJ...763...97W
Altcode:
Filament channels coincide with large-scale polarity inversion
lines of the photospheric magnetic field, where flux cancellation
continually takes place. High-cadence Solar Dynamics Observatory
(SDO) images recorded in He II 30.4 nm and Fe IX 17.1 nm during 2010
August 22 reveal numerous transient brightenings occurring along
the edge of a filament channel within a decaying active region,
where SDO line-of-sight magnetograms show strong opposite-polarity
flux in close contact. The brightenings are elongated along the
direction of the filament channel, with linear extents of several
arcseconds, and typically last a few minutes; they sometimes have
the form of multiple two-sided ejections with speeds on the order of
100 km s-1. Remarkably, some of the brightenings rapidly
develop into larger scale events, forming sheetlike structures that are
eventually torn apart by the diverging flows in the filament channel
and ejected in opposite directions. We interpret the brightenings as
resulting from reconnections among filament-channel field lines having
one footpoint located in the region of canceling flux. In some cases,
the flow patterns that develop in the channel may bring successive
horizontal loops together and cause a cascade to larger scales.
Title: Properties of a Decaying Sunspot
Authors: Balthasar, H.; Beck, C.; Gömöry, P.; Muglach, K.; Puschmann,
K. G.; Shimizu, T.; Verma, M.
Bibcode: 2013CEAB...37..435B
Altcode: 2013arXiv1301.1562B
A small decaying sunspot was observed with the Vacuum Tower Telescope
(VTT) on Tenerife and the Japanese Hinode satellite. We obtained
full Stokes scans in several wavelengths covering different heights
in the solar atmosphere. Imaging time series from Hinode and the
Solar Dynamics Observatory (SDO) complete our data sets. The spot is
surrounded by a moat flow, which persists also on that side of the
spot where the penumbra already had disappeared. Close to the spot,
we find a chromospheric location with downflows of more than 10 km
s^{-1} without photospheric counterpart. The height dependence of
the vertical component of the magnetic field strength is determined
in two different ways that yielded different results in previous
investigations. Such a difference still exists in our present data,
but it is not as pronounced as in the past.
Title: A Preliminary Study of Active Region Canopies With AIA
Authors: Lucchini, Scott; Saar, S.; Muglach, K.
Bibcode: 2013AAS...22115905L
Altcode:
Active region canopies are areas frequently accompanying active regions
which have extensive horizontal magnetic fields. The large-scale
canopy fields have a significant effect on the kinds of structures
which can exist beneath them, and how they evolve. Using data
from the Atmospheric Imaging Assembly (AIA), we developed methods
to automatically identify these regions. A Differential Emission
Measure (DEM) analysis is consistent with the idea that the long,
hotter active region loops overlie quite cool, small-scale features
("fibrils"). We suggest that the overlying loops restrict the growth
of underlying structures to mostly very short, cool features. We also
studied evolution of canopy regions over time. In several cases, a
large quiescent filament formed out of the former canopy region over the
course of a few solar rotations, confirming previous suggestions. The
canopy remains visible for several rotations after its active regions
have begun to decay; in this time, the fibril magnetic fields gradually
align in such a way as to form a filament channel. Further analysis
of our large canopy database should uncover more information on the
frequency and characteristics of these canopy-to-filament evolutions,
as well as other canopy properties. This work is supported by the NSF
REU program at SAO (grant ATM-0851866) and contract SP02H1701R from
Lockheed Martin to SAO for SDO research.
Title: A Long-Lived Equatorial Coronal Hole and the Associated
Solar Wind
Authors: Ko, Y.; Young, P. R.; Muglach, K.; Wang, Y.; Lepri, S. T.;
Laming, J. M.; Popecki, M.
Bibcode: 2012AGUFMSH53A2261K
Altcode:
We study an equatorial coronal hole that came back rotation after
rotation in a course of eight months from July 2007 to March 2008. This
coronal hole was also one of the source regions of the solar wind
measured by ACE during this period. The associated solar wind speed
profiles for the 10 solar rotations are similar that start with a fast
wind above 600 km/s and gradually lower down to below 400 km/s. The ion
composition data indicate a decreasing trend in the ionization states
of heavy ions, especially for the Fe ions. This recurring coronal hole
presents a good opportunity for studying the relations between the solar
wind at a range of speeds and the solar source that produces it. We
present a detailed study of the solar wind from this coronal hole,
concentrating on the ion charge and elemental composition properties,
and the variation in the magnetic and spectroscopic properties in this
source coronal hole. We discuss implications in the solar wind formation
based on the relations between these properties of the source coronal
hole and the associated solar wind.
Title: Evidence for Two Separate But Interlaced Components of the
Chromospheric Magnetic Field
Authors: Muglach, Karin; Reardon, K.; Wang, Y.; Warren, H.
Bibcode: 2012AAS...22012403M
Altcode:
Chromospheric fibrils are generally thought to trace out horizontal
magnetic fields that fan out from flux concentrations in the
photosphere. A high-resolution (0.2") image taken in the core of the
Ca II 854.2 nm line shows the dark fibrils within an active region
remnant as fine, looplike features that are aligned parallel to each
other and have lengths on the order of a supergranular diameter ( 30
Mm). Comparison with a line-of-sight magnetogram confirms that the
fibrils are centered above intranetwork areas, with one end rooted
just inside the neighboring plage or strong unipolar network
but the other endpoint less clearly defined. Focusing on a particular
arcade-like structure lying entirely on one side of a filament channel
(large-scale polarity inversion), we find that the total amount of
positive-polarity flux underlying this ``fibril arcade'' is 50 times
greater than the total amount of negative-polarity flux. Thus, if the
fibrils represent closed loops, they must consist of very weak fields
(in terms of flux density), which are interpenetrated by a more vertical
field that contains most of the flux. This surprising result suggests
that the fibrils in unipolar regions connect the network to the nearby
intranetwork flux, while the bulk of the network flux is diverted
upward into the corona and connects to remote regions of the opposite
polarity. We conclude that the chromospheric field near the edge of
the network has an interlaced structure resembling that in sunspot
penumbrae, with the fibrils representing the low-lying horizontal flux
that remains trapped within the highly nonpotential chromospheric layer.
Title: An Exploration of the Emission Properties of X-ray Bright
Points Seen With SDO
Authors: Saar, Steven H.; Elsden, T.; Muglach, K.
Bibcode: 2012AAS...22020713S
Altcode:
We present preliminary results of a study of X-ray Bright Point (XBP)
EUV emission and its dependence on other properties. The XBPs were
located using a new, automated XBP finder for AIA developed as
part of the Feature Finding Team for SDO Computer Vision. We analyze
XBPs near disk center, comparing AIA EUV fluxes, HMI LOS magnetic
fields, and photospheric flow fields (derived from HMI data) to look
for relationships between XBP emission, magnetic flux, velocity fields,
and XBP local environment. We find some evidence for differences in the
mean XBP temperature with environment. Unsigned magnetic flux is
correlated with XBP emission, though other parameters play a role. The
majority of XBP footpoints are approaching each other, though at
a slight angle from head-on on average. We discuss the results in the
context of XBP heating.
Title: A First Look at Magnetic Field Data Products from SDO/HMI
Authors: Liu, Y.; Scherrer, P. H.; Hoeksema, J. T.; Schou, J.; Bai,
T.; Beck, J. G.; Bobra, M.; Bogart, R. S.; Bush, R. I.; Couvidat,
S.; Hayashi, K.; Kosovichev, A. G.; Larson, T. P.; Rabello-Soares,
C.; Sun, X.; Wachter, R.; Zhao, J.; Zhao, X. P.; Duvall, T. L., Jr.;
DeRosa, M. L.; Schrijver, C. J.; Title, A. M.; Centeno, R.; Tomczyk,
S.; Borrero, J. M.; Norton, A. A.; Barnes, G.; Crouch, A. D.; Leka,
K. D.; Abbett, W. P.; Fisher, G. H.; Welsch, B. T.; Muglach, K.;
Schuck, P. W.; Wiegelmann, T.; Turmon, M.; Linker, J. A.; Mikić,
Z.; Riley, P.; Wu, S. T.
Bibcode: 2012ASPC..455..337L
Altcode:
The Helioseismic and Magnetic Imager (HMI; Scherrer & Schou 2011)
is one of the three instruments aboard the Solar Dynamics Observatory
(SDO) that was launched on February 11, 2010 from Cape Canaveral,
Florida. The instrument began to acquire science data on March 24. The
regular operations started on May 1. HMI measures the Doppler velocity
and line-of-sight magnetic field in the photosphere at a cadence of
45 seconds, and the vector magnetic field at a 135-second cadence,
with a 4096× 4096 pixels full disk coverage. The vector magnetic
field data is usually averaged over 720 seconds to suppress the p-modes
and increase the signal-to-noise ratio. The spatial sampling is about
0".5 per pixel. HMI observes the Fe i 6173 Å absorption line, which
has a Landé factor of 2.5. These data are further used to produce
higher level data products through the pipeline at the HMI-AIA Joint
Science Operations Center (JSOC) - Science Data Processing (Scherrer et
al. 2011) at Stanford University. In this paper, we briefly describe the
data products, and demonstrate the performance of the HMI instrument. We
conclude that the HMI is working extremely well.
Title: Decorrelation Times of Photospheric Fields and Flows
Authors: Welsch, B. T.; Kusano, K.; Yamamoto, T. T.; Muglach, K.
Bibcode: 2012ApJ...747..130W
Altcode: 2011arXiv1110.6117W
We use autocorrelation to investigate evolution in flow fields
inferred by applying Fourier local correlation tracking (FLCT) to a
sequence of high-resolution (0farcs3), high-cadence (sime 2 minute)
line-of-sight magnetograms of NOAA active region (AR) 10930 recorded
by the narrowband filter imager of the Solar Optical Telescope aboard
the Hinode satellite over 2006 December 12 and 13. To baseline the
timescales of flow evolution, we also autocorrelated the magnetograms,
at several spatial binnings, to characterize the lifetimes of active
region magnetic structures versus spatial scale. Autocorrelation of
flow maps can be used to optimize tracking parameters, to understand
tracking algorithms' susceptibility to noise, and to estimate flow
lifetimes. Tracking parameters varied include: time interval Δt between
magnetogram pairs tracked, spatial binning applied to the magnetograms,
and windowing parameter σ used in FLCT. Flow structures vary over a
range of spatial and temporal scales (including unresolved scales), so
tracked flows represent a local average of the flow over a particular
range of space and time. We define flow lifetime to be the flow
decorrelation time, τ. For Δt > τ, tracking results represent
the average velocity over one or more flow lifetimes. We analyze
lifetimes of flow components, divergences, and curls as functions
of magnetic field strength and spatial scale. We find a significant
trend of increasing lifetimes of flow components, divergences, and
curls with field strength, consistent with Lorentz forces partially
governing flows in the active photosphere, as well as strong trends
of increasing flow lifetime and decreasing magnitudes with increases
in both spatial scale and Δt.
Title: On the Solar Wind Ion Composition Properties With Source
Regions from Low-Latitude and Polar Coronal Holes of Opposite Polarity
Authors: Ko, Y.; Muglach, K.; Wang, Y.; Young, P. R.; Lepri, S. T.;
Laming, J. M.; Popecki, M.
Bibcode: 2011AGUFMSH43F..04K
Altcode:
During Years 2004-2007 there were frequent appearances of low-latitude
coronal holes (CHs) and low-latitude extension of polar CHs. These
CHs were the source regions of the solar wind measured in-situ at
L1. We find that the ion composition has distinct properties between
solar wind originating from CHs of opposite polarity. Specifically, the
charge states measured by ACE/SWICS were systematically lower-ionized
for solar wind ions from CHs of positive polarity (the 'south CH') than
those of negative polarity (the 'north CH'), regardless of the solar
wind speed. Such differentiation is apparent only in the low-latitude
extension of polar CHs and those non-polar CHs with predicted footpoints
at latitude higher than 15 degrees. Interestingly, earlier work based
on Ulysses fast wind data during the declining/minimum phase of Cycle
22 found that it was the north polar CH that was associated with lower
solar wind charge states, opposite to what we found in the following
solar cycle. We present these results and search for solar properties
that may be factors that govern this north-south difference.
Title: Evidence for Two Separate but Interlaced Components of the
Chromospheric Magnetic Field
Authors: Reardon, K. P.; Wang, Y. -M.; Muglach, K.; Warren, H. P.
Bibcode: 2011ApJ...742..119R
Altcode:
Chromospheric fibrils are generally thought to trace out low-lying,
mainly horizontal magnetic fields that fan out from flux concentrations
in the photosphere. A high-resolution (~0farcs1 pixel-1)
image, taken in the core of the Ca II 854.2 nm line and covering
an unusually large area, shows the dark fibrils within an active
region remnant as fine, looplike features that are aligned parallel
to each other and have lengths comparable to a supergranular
diameter. Comparison with simultaneous line-of-sight magnetograms
confirms that the fibrils are centered above intranetwork areas
(supergranular cell interiors), with one end rooted just inside the
neighboring plage or strong unipolar network but the other endpoint
less clearly defined. Focusing on a particular arcade-like structure
lying entirely on one side of a filament channel (large-scale polarity
inversion), we find that the total amount of positive-polarity flux
underlying this "fibril arcade" is ~50 times greater than the total
amount of negative-polarity flux. Thus, if the fibrils represent closed
loops, they must consist of very weak fields (in terms of total magnetic
flux), which are interpenetrated by a more vertical field that contains
most of the flux. This surprising result suggests that the fibrils in
unipolar regions connect the network to the nearby intranetwork flux,
while the bulk of the network flux links to remote regions of the
opposite polarity, forming a second, higher canopy above the fibril
canopy. The chromospheric field near the edge of the network thus has
an interlaced structure resembling that in sunspot penumbrae.
Title: Tracking Vector Magnetograms from the Solar Dynamics
Observatory
Authors: Schuck, P. W.; Sun, X.; Muglach, K.; Hoeksema, J. T.; HMI
Vector Field Team
Bibcode: 2011sdmi.confE..36S
Altcode:
The differential affine velocity estimator for vector magnetograms
(DAVE4VM) has been developed for estimating photospheric
velocities. The accuracy of this technique has been demonstrated
on synthetic magnetograms from MHD simulations. The algorithm was
initially formulated in Cartesian coordinates. Thus, for best results,
solar vector magnetograms must be transformed from the image plane
into a Mercator map or some other Cartesian-like projection before
applyng DAVE4VM. Recently, DAVE4VM has been modified to incorporate
directly the projected spherical geometry of Helioprojective-Cartesian
coordinates, thus permitting direct application of the method to image
plane vector magnetograms. We will discuss the new algorithm and tests
of the modified method and present first results of DAVE4VM applied
to Solar Dynamics Observatory vector magnetograms.
Title: On the ion composition properties in the solar wind from the
north and south polar coronal holes
Authors: Ko, Yuan-Kuen; Muglach, Karin; Wang, Yi-Ming; Young, Peter
R.; Lepri, Susan T.; Laming, J. Martin; Popecki, Mark A.
Bibcode: 2011shin.confE.158K
Altcode:
During Years 2005-2007 in the declining phase of Cycle 23 there
were frequent appearances of equatorial coronal holes (CHs) and
low-latitude extension of polar CHs that were the source regions of
the solar wind measured in-situ at L1 a few days after these CHs
past the central meridian. We find that the solar wind heavy ions
emanating from the south and north polar CHs have distinct composition
properties. Specifically, the charge states measured by ACE/SWICS
were systematically lower for solar wind ions from the south polar
CHs than those from the north polar CHs, regardless of the solar
wind speed. Interestingly, earlier work based on Ulysses data during
the declining/minimum phase of Cycle 22 found that it was the north
polar CH that was associated with lower solar wind charge states,
opposite to what we found in the following solar cycle. We present
these results and search for solar properties that may be factors
that govern this north-south difference. Implications in solar wind
formation are discussed.
Title: The Evolution of Dark Canopies Around Active Regions
Authors: Wang, Y. -M.; Robbrecht, E.; Muglach, K.
Bibcode: 2011ApJ...733...20W
Altcode: 2011arXiv1103.4373W
As observed in spectral lines originating from the chromosphere,
transition region, and low corona, active regions are surrounded by an
extensive "circumfacular" area which is darker than the quiet Sun. We
examine the properties of these dark moat- or canopy-like areas using Fe
IX 17.1 nm images and line-of-sight magnetograms from the Solar Dynamics
Observatory. The 17.1 nm canopies consist of fibrils (horizontal fields
containing extreme-ultraviolet-absorbing chromospheric material)
clumped into featherlike structures. The dark fibrils initially
form a quasiradial or vortical pattern as the low-lying field lines
fanning out from the emerging active region connect to surrounding
network and intranetwork elements of opposite polarity. The area
occupied by the 17.1 nm fibrils expands as supergranular convection
causes the active-region flux to spread into the background medium;
the outer boundary of the dark canopy stabilizes where the diffusing
flux encounters a unipolar region of opposite sign. The dark fibrils
tend to accumulate in regions of weak longitudinal field and to become
rooted in mixed-polarity flux. To explain the latter observation,
we note that the low-lying fibrils are more likely to interact with
small loops associated with weak, opposite-polarity flux elements
in close proximity, than with high loops anchored inside strong
unipolar network flux. As a result, the 17.1 nm fibrils gradually
become concentrated around the large-scale polarity inversion lines
(PILs), where most of the mixed-polarity flux is located. Systematic
flux cancellation, assisted by rotational shearing, removes the field
component transverse to the PIL and causes the fibrils to coalesce
into long PIL-aligned filaments.
Title: Studying Solar Active Regions with HMI Data
Authors: Liu, Yang; Hoeksema, J.; Hayashi, K.; Sun, X.; Schuck, P.;
Muglach, K.
Bibcode: 2011SPD....42.2102L
Altcode: 2011BAAS..43S.2102L
Full disk field of view, continuous time coverage, high temporal
and spatial resolutions, and consistent data quality, these
specifications of the HMI observational data allows us to study
in detail the evolution of solar active regions during the course
from emerging to decaying. Using the HMI vector magnetic field data
(test version), we study the magnetic energy and helicity in emerging
active regions. First, we apply the code DAVE4VM (Schuck 2008) to the
time-series vector magnetic field data to derive the plasma velocity;
then we break down the energy and helicity fluxes into two components,
one due to vertical advection of the magnetic field through the
photosphere, and the other due to the horizontal motion that shears
the field lines. We analyze the roles these two processes play in
accumulating the energy and helicity in the corona, and explore their
correlations with the evolution of active regions.
Title: The Photospheric Velocity Field of Active Regions Derived
from SDO/HMI Vector Magnetograms
Authors: Muglach, Karin; Schuck, P.; HMI vector magnetogram Team
Bibcode: 2011SPD....42.2112M
Altcode: 2011BAAS..43S.2112M
We present a first analysis of solar active regions observed with the
Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory
(SDO). Since HMI continuously observes the complete solar disk at a good
spatial resolution we are able to follow active regions over several
days, providing the opportunity to study the evolution of the flow field
during the various stages of development of the active regions. HMI
measures the photospheric vector magnetic field at a cadence of 12
min. To determine the velocity field we use the optical flow technique
DAVE4VM (differential affine velocity estimator for vector magnetograms)
and apply it to the vector magnetic field data from SDO/HMI.
Title: The Evolution of Dark Canopies Around Active Regions
Authors: Muglach, Karin; Wang, Y. M.; Robbrecht, E.
Bibcode: 2011SPD....42.1718M
Altcode: 2011BAAS..43S.1718M
As observed in spectral lines originating from the chromosphere,
transition region, and low corona, active regions are surrounded
by an extensive 'circumfacular' area which is darker than the quiet
Sun. We examine the properties of these dark moat- or canopy-like areas
using Fe IX 17.1 nm images and line-of-sight magnetograms from the
Solar Dynamics Observatory. The 17.1 nm canopies consist of fibrils
(horizontal fields containing EUV-absorbing chromospheric material)
clumped into featherlike structures. The dark fibrils initially
form a quasiradial or vortical pattern as the low-lying field lines
fanning out from the emerging active region connect to surrounding
network and intranetwork elements of the opposite polarity. The area
occupied by the 17.1 nm fibrils expands as supergranular convection
causes the active region flux to spread into the background medium;
the outer boundary of the dark canopy stabilizes where the diffusing
flux encounters a unipolar region of the opposite sign. The dark fibrils
tend to accumulate in regions of weak longitudinal field and to become
rooted in mixed-polarity flux. To explain the latter observation,
we note that the low-lying fibrils are more likely to interact with
small loops associated with weak, opposite-polarity flux elements
in close proximity, than with high loops anchored inside strong
unipolar network flux. As a result, the 17.1 nm fibrils gradually
become concentrated around the large-scale polarity inversion lines
(PILs), where most of the mixed-polarity flux is located. Systematic
flux cancellation, assisted by rotational shearing, removes the field
component transverse to the PIL and causes the fibrils to coalesce
into long PIL-aligned filaments.
Title: The Evolution of Photospheric Flows in Active Regions
Authors: Muglach, K.; Schuck, P. W.; Hoeksema, J. T.; Sun, X.; Liu, Y.
Bibcode: 2010AGUFMSH11A1605M
Altcode:
We will present first results of an analysis of the photospheric flow
field in and around active region AR 11066. It emerged on 2nd May,
2010 near central meridian and developed into a small active region
with simple bipolar structure. We will use SDO/HMI data to estimate
the photospheric flow field applying the optical flow technique DAVE4VM
(differential affine velocity estimator for vector magnetograms). Using
both line-of-sight and vector magnetograms we will study the evolution
of the photospheric flow velocity during the early stage of development
of the active region.
Title: Tracking Vector Magnetograms from the Solar Dynamics
Observatory
Authors: Schuck, P. W.; Sun, X.; Muglach, K.; Hoeksema, J. T.
Bibcode: 2010AGUFMSH14A..07S
Altcode:
The differential affine velocity estimator for vector magnetograms
(DAVE4VM) has been developed for estimating photospheric
velocities. The accuracy of this technique has been demonstrated
on synthetic magnetograms from MHD simulations. The algorithm was
initially formulated in Cartesian coordinates. Thus, for best results,
solar vector magnetograms must be transformed from the image plane
into a Mercator map or some other Cartesian-like projection before
applyng DAVE4VM. Recently, DAVE4VM has been modified to incorporate
directly the projected spherical geometry of Helioprojective-Cartesian
coordinates, thus permitting direct application of the method to image
plane vector magnetograms. We will discuss the new algorithm and tests
of the modified method and present first results of DAVE4VM applied
to Solar Dynamics Observatory vector magnetograms.
Title: Correlation Times of Solar Active Regions
Authors: Muglach, Karin; Schuck, P. W.; Linton, M. G.
Bibcode: 2010AAS...21640213M
Altcode: 2010BAAS...41..875M
The aim of this project is to determine the photospheric velocity
field in solar magnetic regions. A systematic characterization of
the flow field can provide important insight into the formation of
active regions and filaments as well as the development of unstable
magnetic configurations that lead to the initation of flares and
coronal mass ejections. We plan to derive the flow fields from
vector magnetograms obtained with the Stokes Polarimeter (SP) onboard
the Hinode satellite and using the new optical flow technique DAVE4VM
(differential affine velocity estimator for vector magnetograms). All
local correlation tracking methods rely on comparing images (taken at
different times) and deriving the spatial displacement of structures
found in these images via a generalized cross-correlation. If the
structures undergo significant development during the time the images
are taken, the cross-correlation will not give meaningful results. As
we will use magnetogram data for the tracking, we need to evaluate
the temporal evolution and correlation times of the magnetic field
vector B. We will determine the correlation times of the longitudinal
and transverse components of the magnetic field vector in regions
of different magnetic field strength and structure. This allows us
to find the optimal cadence necessary for a good performance of the
DAVE4VM code.
Title: Understanding Solar Eruptions with SDO/HMI Measuring
Photospheric Flows, Testing Models, and Steps Towards Forecasting
Solar Eruptions
Authors: Schuck, Peter W.; Linton, M.; Muglach, K.; Hoeksema, T.
Bibcode: 2010AAS...21640214S
Altcode: 2010BAAS...41Q.875S
The Solar Dynamics Observatory (SDO) is carrying the first full-disk
imaging vector magnetograph, the Helioseismic and Magnetic Imager (HMI),
into an inclined geosynchronous orbit. This magnetograph will provide
nearly continuous measurements of photospheric vector magnetic fields
at cadences of 90 seconds to 12 minutes with 1" resolution, precise
pointing, and unfettered by atmospheric seeing. The enormous data
stream of 1.5 Terabytes per day from SDO will provide an unprecedented
opportunity to understand the mysteries of solar eruptions. These
ground-breaking observations will permit the application of a new
technique, the differential affine velocity estimator for vector
magnetograms (DAVE4VM), to measure photospheric plasma flows in active
regions. These measurements will permit, for the first time, accurate
assessments of the coronal free energy available for driving CMEs and
flares. The details of photospheric plasma flows, particularly along
magnetic neutral-lines, are critical to testing models for initiating
coronal mass ejections (CMEs) and flares. Assimilating flows and
fields into state-of-the art 3D MHD simulations that model the highly
stratified solar atmosphere from the convection zone to the corona
represents the next step towards achieving NASA's Living with a Star
forecasting goals of predicting "when a solar eruption leading to a
CME will occur." Our presentation will describe these major science
and predictive advances that will be delivered by SDO/HMI.
Title: Doppler-shift, Intensity, and Density Oscillations Observed
with the Extreme Ultraviolet Imaging Spectrometer on Hinode
Authors: Mariska, John T.; Muglach, K.
Bibcode: 2010ApJ...713..573M
Altcode: 2010arXiv1003.0420M
Low-amplitude Doppler-shift oscillations have been observed in
coronal emission lines in a number of active regions with the EUV
Imaging Spectrometer (EIS) on the Hinode satellite. Both standing
and propagating waves have been detected and many periods have been
observed, but a clear picture of all the wave modes that might be
associated with active regions has not yet emerged. In this study,
we examine additional observations obtained with EIS in plage near an
active region on 2007 August 22-23. We find Doppler-shift oscillations
with amplitudes between 1 and 2 km s-1 in emission lines
ranging from Fe XI 188.23 Å, which is formed at log T = 6.07, to Fe XV
284.16 Å, which is formed at log T = 6.32. Typical periods are near 10
minutes. We also observe intensity and density oscillations for some
of the detected Doppler-shift oscillations. In the better-observed
cases, the oscillations are consistent with upwardly propagating slow
magnetoacoustic waves. Simultaneous observations of the Ca II H line
with the Hinode Solar Optical Telescope Broadband Filter Imager show
some evidence for 10 minute oscillations as well.
Title: The three-dimensional structure of sunspots. II. The moat
flow at two different heights
Authors: Balthasar, H.; Muglach, K.
Bibcode: 2010A&A...511A..67B
Altcode: 2009arXiv0912.3661B
Aims: Many sunspots are surrounded by a radial outflow called
the moat flow. We investigate the moat flow at two different heights
of the solar atmosphere for a sunspot whose magnetic properties were
reported in the first paper of this series.
Methods: We use
two simultaneous time series taken with the Transition Region And
Coronal Explorer (TRACE) in white light and in the UV at 170 nm. The
field-of-view is centered on the small sunspot NOAA 10886 located near
disk center. Horizontal velocities are derived by applying two different
local correlation tracking techniques.
Results: Outflows are
found everywhere in the moat. In the inner moat, the velocities from
the UV series are larger than those from white light, whereas in the
outer part of the moat we find the converse result.
Conclusions:
The results imply that the white light velocities represent a general
outflow of the quiet sun plasma in the moat, while UV velocities are
dominated by small bright points that move faster than the general
plasma flow.
Title: The Electron Temperature of the Solar Transition Region as
Derived from EIS and SUMER
Authors: Muglach, K.; Landi, E.; Doschek, G. A.
Bibcode: 2010ApJ...708..550M
Altcode:
We use UV and extreme-UV emission lines observed in quiet regions on the
solar disk with the Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) instrument and the Extreme Ultraviolet Imaging Spectrometer
(EIS) to determine the electron temperature in solar transition region
plasmas. Prominent emission lines of O IV and O VI are present in
the solar spectrum, and the measured intensity line ratios provide
electron temperatures in the range of log T = 5.6-6.1. We find that the
theoretical O IV and O VI ion formation temperatures are considerably
lower than our derived temperatures. The line ratios expected from
a plasma in ionization equilibrium are larger by a factor of about
2-5 than the measured line ratios. A careful cross-calibration of
SUMER and EIS has been carried out, which excludes errors in the
relative calibration of the two instruments. We checked for other
instrumental and observational effects, as well as line blending,
and can exclude them as a possible source of the discrepancy between
theoretical and observed line ratios. Using a multi-thermal quiet-Sun
differential emission measure changes the theoretical line ratio by
up to 28% which is not sufficient as an explanation. We also explored
additional excitation mechanisms. Photoexcitation from photospheric
blackbody radiation, self-absorption, and recombination into excited
levels cannot be a possible solution. Adding a second Maxwellian to
simulate the presence of non-thermal, high-energy electrons in the
plasma distribution of velocities also did not solve the discrepancy.
Title: Evidence for Mixed Helicity in Erupting Filaments
Authors: Muglach, K.; Wang, Y. -M.; Kliem, B.
Bibcode: 2009ApJ...703..976M
Altcode: 2009arXiv0907.4446M
Erupting filaments are sometimes observed to undergo a rotation
about the vertical direction as they rise. This rotation of the
filament axis is generally interpreted as a conversion of twist into
writhe in a kink-unstable magnetic flux rope. Consistent with this
interpretation, the rotation is usually found to be clockwise (as viewed
from above) if the post-eruption arcade has right-handed helicity, but
counterclockwise if it has left-handed helicity. Here, we describe two
non-active-region filament events recorded with the Extreme-Ultraviolet
Imaging Telescope on the Solar and Heliospheric Observatory in which
the sense of rotation appears to be opposite to that expected from
the helicity of the post-event arcade. Based on these observations,
we suggest that the rotation of the filament axis is, in general,
determined by the net helicity of the erupting system, and that the
axially aligned core of the filament can have the opposite helicity sign
to the surrounding field. In most cases, the surrounding field provides
the main contribution to the net helicity. In the events reported here,
however, the helicity associated with the filament "barbs" is opposite
in sign to and dominates that of the overlying arcade.
Title: Endpoint Brightenings in Erupting Filaments
Authors: Wang, Y. -M.; Muglach, K.; Kliem, B.
Bibcode: 2009ApJ...699..133W
Altcode:
Two well known phenomena associated with erupting filaments are
the transient coronal holes that form on each side of the filament
channel and the bright post-event arcade with its expanding double
row of footpoints. Here we focus on a frequently overlooked signature
of filament eruptions: the spike- or fan-shaped brightenings that
appear to mark the far endpoints of the filament. From a sample of
non-active-region filament events observed with the Extreme-Ultraviolet
Imaging Telescope on the Solar and Heliospheric Observatory, we find
that these brightenings usually occur near the outer edges of the
transient holes, in contrast to the post-event arcades, which define
their inner edges. The endpoints are often multiple and are rooted
in and around strong network flux well outside the filament channel,
a result that is consistent with the axial field of the filament being
much stronger than the photospheric field inside the channel. The
extreme ultraviolet brightenings, which are most intense at the
time of maximum outward acceleration of the filament, can be used to
determine unambiguously the direction of the axial field component from
longitudinal magnetograms. Their location near the outer boundary of
the transient holes suggests that we are observing the footprints of
the current sheet formed at the leading edge of the erupting filament,
as distinct from the vertical current sheet behind the filament which
is the source of the post-event arcade.
Title: Doppler Shift Oscillations Observed with the EUV Imaging
Spectrometer on Hinode
Authors: Mariska, John T.; Muglach, K.
Bibcode: 2009SPD....40.1301M
Altcode:
The EUV Imaging Spectrometer (EIS) on Hinode is capable of measuring
Doppler shift fluctuations with amplitudes of less than 0.5 km/s. This,
coupled with EIS's improved sensitivity over previous EUV spectrometers,
has expanded the range of coronal oscillatory phenomena available
for detailed study. For example, both kink mode and slow mode coronal
loop oscillations have already been detected with EIS. We report on
additional observations of Doppler shift and intensity oscillations
in an active region observed in 2007 August. An initial periodogram
analysis of portions of the data shows periods in the Doppler shift
data of 9 to 10 minutes in emission lines with temperatures of
formation from 1.2 to 2.1 MK. Periods of 8 to 12 minutes are seen
in the detrended intensity data over the same temperature range. The
EIS observations include density-sensitive emission lines from Fe XII
and Fe XIII, allowing us to quantify density fluctuations. The Solar
Optical Telescope on Hinode made simultaneous Ca II observations,
which we have co-aligned with the EIS data to understand better the
chromospheric environment in the oscillating region. This work
was supported by the NASA Hinode program.
Title: Physical Properties In An Equatorial Coronal Hole And Its
Connection To The Solar Wind Properties
Authors: Ko, Yuan-Kuen; Young, P. R.; Lepri, S.; Popecki, M.; Muglach,
K.; Wang, Y.; Laming, J. M.
Bibcode: 2009SPD....40.1405K
Altcode:
We analyze the physical properties in an equatorial coronal hole
that was observed by Hinode/EIS in two consecutive solar rotations in
February and March of 2009. This coronal hole is the obvious source
region for the solar wind measured in-situ by ACE and STEREO that
exhibits the typical fast-to-slow characteristics in proton speed. We
determine the electron density and temperature structures at several
locations in the coronal hole that may correspond to the footpoints
of the solar wind measured in-situ. We discuss the variations of such
properties between locations as well as between the two rotations. We
compare and discuss such variations in the coronal hole with the
properties in the solar wind, in particular, the ion charge composition.
Title: Endpoint Brightenings in Erupting Filaments
Authors: Muglach, Karin; Wang, Y.; Kliem, B.
Bibcode: 2009SPD....40.2109M
Altcode:
Two well-known phenomena associated with erupting filaments are
the transient coronal holes that form on each side of the filament
channel and the bright post-event arcade with its expanding double
row of footpoints. Here we focus on a frequently overlooked signature
of filament eruptions: the spike- or fan-shaped brightenings that
appear to mark the far endpoints of the filament. From a sample of
non-active-region filament events observed with the Extreme-Ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO), we find that these brightenings usually occur near the outer
edges of the transient holes, in contrast to the post-event arcades,
which define their inner edges. The endpoints are often multiple
and are rooted in and around strong network flux well outside the
filament channel, a result that is consistent with the axial field of
the filament being much stronger than the photospheric field inside
the channel. The EUV brightenings, which are most intense at the
time of maximum outward acceleration of the filament, can be used to
determine unambiguously the direction of the axial field component from
longitudinal magnetograms. Their location near the outer boundary of
the transient holes suggests that we are observing the footprints of
the current sheet formed at the leading edge of the erupting filament,
as distinct from the vertical current sheet behind the filament which
is the source of the post-event arcade.
Title: Characterizing Solar Wind and its Source Regions as Empirical
Constraints for Investigating Solar Wind Formation
Authors: Ko, Y.; Wang, Y.; Muglach, K.; Lepri, S. T.; Laming, J. M.;
Popecki, M.
Bibcode: 2008AGUFMSH43B..06K
Altcode:
We use ACE solar wind data during years 2004-2007 and characterize
the properties of the solar wind that originates from equatorial and
low-latitude coronal holes. Such coronal holes have been observed to
produce fast solar wind streams often followed by a smooth transition
into slow wind streams. We investigate solar wind properties of
such origin, particularly the ion charge composition and elemental
abundances, and their relation to the properties at their source
regions. These types of coronal holes and the associated solar wind
have frequent occurrences in the past and current solar cycles, and
have great advantages in investigating a wide variety of the solar
wind properties and its sources at the Sun because of the diversity
in their size, location, as well as the magnetic and plasma properties
in the coronal hole and the surrounding closed field structures.
Title: Explosive Events and the Evolution of the Photospheric
Magnetic Field
Authors: Muglach, K.
Bibcode: 2008ApJ...687.1398M
Altcode: 2008arXiv0808.1091M
Transition region explosive events have long been suggested as direct
signatures of magnetic reconnection in the solar atmosphere. In seeking
further observational evidence to support this interpretation, we study
the relation between explosive events and the evolution of the solar
magnetic field as seen in line-of-sight photospheric magnetograms. We
find that about 38% of events show changes of the magnetic structure
in the photosphere at the location of an explosive event over a time
period of 1 hr. We also discuss potential ambiguities in the analysis
of high-sensitivity magnetograms.
Title: Flows and Nonthermal Velocities in Solar Active Regions
Observed with the EUV Imaging Spectrometer on Hinode: A Tracer of
Active Region Sources of Heliospheric Magnetic Fields?
Authors: Doschek, G. A.; Warren, H. P.; Mariska, J. T.; Muglach, K.;
Culhane, J. L.; Hara, H.; Watanabe, T.
Bibcode: 2008ApJ...686.1362D
Altcode: 2008arXiv0807.2860D
From Doppler velocity maps of active regions constructed from spectra
obtained by the EUV Imaging Spectrometer (EIS) on the Hinode spacecraft
we observe large areas of outflow (20-50 km s-1) that can
persist for at least a day. These outflows occur in areas of active
regions that are faint in coronal spectral lines formed at typical
quiet-Sun and active region temperatures. The outflows are positively
correlated with nonthermal velocities in coronal plasmas. The bulk
mass motions and nonthermal velocities are derived from spectral line
centroids and line widths, mostly from a strong line of Fe XII at
195.12 Å. The electron temperature of the outflow regions estimated
from an Fe XIII to Fe XII line intensity ratio is about (1.2-1.4) ×
106 K. The electron density of the outflow regions derived
from a density-sensitive intensity ratio of Fe XII lines is rather low
for an active region. Most regions average around 7 × 108
cm-3, but there are variations on pixel spatial scales
of about a factor of 4. We discuss results in detail for two active
regions observed by EIS. Images of active regions in line intensity,
line width, and line centroid are obtained by rastering the regions. We
also discuss data from the active regions obtained from other orbiting
spacecraft that support the conclusions obtained from analysis of the
EIS spectra. The locations of the flows in the active regions with
respect to the longitudinal photospheric magnetic fields suggest that
these regions might be tracers of long loops and/or open magnetic
fields that extend into the heliosphere, and thus the flows could
possibly contribute significantly to the solar wind.
Title: The Moat Flow in Two Different Heights
Authors: Balthasar, H.; Muglach, K.
Bibcode: 2008ESPM...12.2.26B
Altcode:
We investigate time series obtained with the Transition Region And
Coronal Explorer (TRACE) simultaneously in two wavelength ranges, in
whitelight (WL) and in the ultraviolet at 170 nm (UV). In the quiet
sun, the UV is most sensitive to layers just below the temperature
minimum. The field-of-view was centered on a small sunspot passing
the central meridian. Horizontal velocities are determined by
local correlation techniques (LCT), and we compare two different
LCT-methods. We find an extended outflow in the moat. We detect the
outflow up to four times the radius of the spot. For both wavelength
ranges the outer boundary of the flow is located at the same distance
from the center of the spot. In the inner moat velocities are higher
in the UV, indicating higher velocities in the upper layers. In the
outer moat higher velocities are detected in WL.
Title: The Electron Temperature of the Solar Transition Region
Authors: Muglach, K.; Landi, E.; Doschek, G. A.
Bibcode: 2008AGUSMSP43C..05M
Altcode:
There are few spectroscopic measurements of electron temperature
in the solar transition region (the temperature region from about
2×104 K to 8×105 K). This is because UV and EUV spectral lines
from which temperature sensitive intensity ratios can be formed
are usually far separated in wavelength and cannot be observed
by a single instrument. Therefore, temperatures inferred for the
transition region are usually obtained from experimentally untested
theory that furthermore depends on the assumption of ionization
equilibrium. However, between 30 March 2007 and 14 April 2007 there
was a joint campaign between the SUMER spectrometer on SOHO and the
EIS spectrometer on Hinode. The EIS spectrometer operates in two
narrow wavelength bands: 170 — 210 and 250 — 290 Å. The SUMER
spectrometer operates roughly between about 500 and 1610 Å. Both SUMER
and EIS jointly observed portions of quiet Sun and active regions and
obtained spectra that include lines from a number of the same transition
region ions. The ratios of some of these lines from the same ion are
temperature sensitive and provide an unprecedented opportunity to
measure the temperatures of ion formation in the transition region and
to compare these temperatures with the values obtained from theoretical
ionization equilibrium calculations. A good example is the lines of
O VI at 183.94, 184.12 Å (EIS) and 1031.92, 1037.61 Å (SUMER). We
discuss temperatures derived for quiet Sun and active region transition
regions from joint spectra obtained during the SUMER/EIS campaign.
Title: Observations of Low-Latitude Coronal Plumes
Authors: Wang, Y. -M.; Muglach, K.
Bibcode: 2008SoPh..249...17W
Altcode: 2008SoPh..tmp...71W
Using Fe IX/X 17.1 nm observations from the Extreme-Ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO), we have identified many coronal plumes inside low-latitude
coronal holes as they transited the solar limb during the late
declining phase of cycle 23. These diffuse, linear features appear
to be completely analogous to the familiar polar plumes. By tracking
them as they rotate from the limb onto the disk (or vice versa),
we confirm that EUV plumes seen against the disk appear as faint,
diffuse blobs of emission surrounding a brighter core. When the EIT
images are compared with near-simultaneous magnetograms from the SOHO
Michelson Doppler Imager (MDI), the low-latitude, on-disk plumes are
found to overlie regions of mixed polarity, where small bipoles are in
contact with unipolar flux concentrations inside the coronal hole. The
birth and decay of the plumes are shown to be closely related to the
emergence of ephemeral regions, their dispersal in the supergranular
flow field, and the cancellation of the minority-polarity flux against
the dominant-polarity network elements. In addition to the faint polar
and nonpolar plumes associated with ephemeral regions, we note the
existence of two topologically similar coronal structures: the giant
plume-like features that occur above active regions inside coronal
holes, and the even larger scale "pseudostreamers" that separate
coronal holes of the same polarity. In all three cases, the basic
structure consists of open field lines of a given polarity overlying
a photospheric region of the opposite polarity; ongoing interchange
reconnection at the X-point separating the open field domains from
the underlying double-arcade system appears to result in the steady
evaporation of material from the closed into the open region.
Title: The Formation of Filament Channels
Authors: Muglach, K.; Wang, Y.
Bibcode: 2008AGUSMSP53A..02M
Altcode:
Hα fibrils are generally thought to trace out the horizontal component
of the chromospheric magnetic field. They can be oriented at any angle
relative to the polarity inversion line (PIL), where the line--of--sight
component of the photospheric field changes sign. Filaments are
found where the fibrils invariably run almost parallel to the PIL,
forming a filament channel. We present three examples showing Hα
fibrils that change their orientation, over one or two days, from
nearly perpendicular to nearly parallel to the PIL. Comparing the Hα
filtergrams with magnetograms from the Michelson Doppler Imager, we find
that the fibrils become aligned with the PIL as supergranular convection
brings opposite-polarity magnetic flux together; shearing motions along
the PIL, when present, act mainly to accelerate the rate of diffusive
annihilation. We conclude that the reorientation of the fibrils is due
to the cancellation and submergence of the transverse field component
(B⊥), leaving behind the preexisting axial field component B∥).
Title: Photospheric Source Regions of Coronal Mass Ejections
Authors: Muglach, K.
Bibcode: 2008ASPC..383..347M
Altcode:
Many source regions of coronal mass ejections (CMEs) show
signatures of magnetic flux changes prior to the CME onset
tep{KM-2005IAUS..226..179M}. In this paper we present a detailed study
of the evolution of the photospheric structures using data taken with
MDI onboard SOHO. Magnetograms and Dopplergrams are used to characterize
the flux changes that happen in connection with the CMEs. We discuss
the implications of our findings on the initiation of CMEs.
Title: On the Formation of Filament Channels
Authors: Wang, Y. -M.; Muglach, K.
Bibcode: 2007ApJ...666.1284W
Altcode:
From the Hα archive of the Big Bear Solar Observatory (BBSO) we
have selected three examples showing fibril structures that change
their orientation, over 1 or 2 days, from nearly perpendicular to
nearly parallel to the polarity inversion line (PIL). In one case,
the filament channel forms within a single decaying bipole; in the
other two cases, it forms along the boundary between an active
region and its surroundings. Comparing the Hα filtergrams with
magnetograms from the Michelson Doppler Imager (MDI), we find that
the fibrils become aligned with the PIL as supergranular convection
brings opposite-polarity magnetic flux together; shearing motions
along the PIL, when present, act mainly to accelerate the rate of
diffusive annihilation. We conclude that the reorientation of the
fibrils is due to the cancellation and submergence of the transverse
field component (B⊥), leaving behind the preexisting axial
field component (B∥). The latter may have been generated
by photospheric differential rotation over longer timescales, or
else was already present when the flux emerged. The filament channel
forms slowly if B∥/B⊥ is initially small,
as along the internal neutral line of a newly emerged bipole, but
may appear within hours if this ratio is initially substantial,
as where the dipole-like loops of an active region curve around its
periphery. In all of our examples, filaments form within a day or so
after the fibrils become aligned with the PIL, while barbs appear at
a later stage, as flux elements continue to diffuse across the PIL
and cancel with the majority-polarity flux on the other side.
Title: Transition Region Explosive Events and their Relation to the
Solar Magnetic Field
Authors: Muglach, Karin; Dere, K.
Bibcode: 2007AAS...210.9118M
Altcode: 2007BAAS...39..207M
Magnetic field restructuring by reconnection is pervasive in solar
physics. It can potentially provide the energy to heat and accelerate
the plasma in the solar atmosphere. We will investigate the role
of small-scale magnetic reconnection in the formation of transition
region explosive events. These events are defined by strong transient
enhancements of the wings of spectral lines that form at transition
region temperatures (between 20 000 - 200 000 K).Using SUMER data
we are able to identify EEs by their spectral signature. With MDI we
can continuously map the photospheric magnetic field and search for a
manifestation of the reconnection in the lower solar atmosphere. We
have analysed several dozens of explosive events and will show how
the underlying magnetic field evolves during these events.
Title: High Frequency Oscillations in Solar Magnetic Regions
Authors: Muglach, Karin
Bibcode: 2006SPD....37.1901M
Altcode: 2006BAAS...38Q.247M
This contribution is intended to be an observationalcounterpart to
recent MHD simulation and radiative transferresearch undertaken to
study the propagation of wavesin magnetized solar atmospheres.We will
present the results of an observational studyof the presence of high
frequency oscillations (f>15mHz)in various magnetic regions.These
high frequency waves are thought to play an importantrole in the
heating of the upper solar atmosphere.We will apply standard Fourier
techniquesas well as wavelet transforms to identify theoscillations
and perform statistical teststo determine their significance.
Title: Influence of Instrumental Effects on High Frequency
Oscillations Observed with Trace
Authors: Muglach, K.; Balthasar, H.
Bibcode: 2005ESASP.596E..76M
Altcode: 2005ccmf.confE..76M
No abstract at ADS
Title: Dynamics of solar active regions. II. Oscillations observed
with MDI and their relation to the magnetic field topology
Authors: Muglach, K.; Hofmann, A.; Staude, J.
Bibcode: 2005A&A...437.1055M
Altcode:
We present new results of an international joint observing campaign,
which was carried out in September 2000 to study the oscillatory
behaviour of solar active regions. We concentrate on oscillations
in the lower layers of the solar atmosphere as observed with the
Michelson Doppler Imager (MDI, Scherrer et al. 1995, Sol. Phys., 162,
129). The resulting photospheric oscillation power maps are compared
with chromospheric maps from simultaneous UV continuum data (taken with
the TRACE instrument). From a magnetic field extrapolation of the MDI
magnetograms we infer that the reduction in chromospheric high frequency
power and enhancement of photospheric high frequency power may be
explained by the interaction of acoustic waves with the magnetic canopy.
Title: Active Region Oscillations and Their Relation to the Magnetic
Field Topology
Authors: Muglach, K.; Hofmann, A.; Staude, J.
Bibcode: 2005AGUSMSH13C..03M
Altcode:
In this contribution we present an analysis of time sequences of MDI
intensity and Doppler velocity together with simultaneous filtergrams
taken by TRACE at 1700A in an active region. The high frequency
halos found in MDI velocity and the deficiency of high frequency
power sampled at the height of the TRACE UV filter around the active
region can be explained by an interaction of the acoustic wave field
with the magnetic field of the active region. From a magnetic field
extrapolation we calculate the plasma β for the complete TRACE FOV
up to the base of the corona. The contours giving the location of β
approximately 1 where h=500 km agree very well with the decrease in
1700A high frequency power.
Title: The Evolution of Photospheric Source Regions of CMEs
Authors: Muglach, K.; Dere, K.
Bibcode: 2005IAUS..226..179M
Altcode:
In this presentation we determine the source regions of CMEs that
were observed with SoHO/LASCO during times of solar activity maximum
(Feb./Mar. 2000) and during the declining phase of the solar cycle
(Nov./Dec. 2002). The CMEs were traced back onto the disk and EIT
EUV images were used for identifying the sources. With the help of
MDI synoptic magnetograms we follow the evolution of the photospheric
magnetic flux about 24h before and 12h after the event. We find that
about 87% of the identified CME source regions show small-scale
flux changes before the event, usually flux emergence and/or flux
disappearance. In 13% of the cases we find no signature of photospheric
flux changes.
Title: The Evolution of Photospheric Source Regions of CMEs
Authors: Muglach, K.; Dere, K.
Bibcode: 2004AAS...204.3808M
Altcode: 2004BAAS...36..713M
In this presentation we determine the source regions of CMEs that
were observed with SOHO/LASCO during times of solar activity maximum
(Feb./Mar. 2000) and during the declining phase of the solar cycle
(Nov./Dec. 2002). The CMEs were traced back onto the disk and EIT EUV
images were used for identifying the sources. With the help of MDI
synoptic and high cadence magnetograms we follow the evolution of the
photospheric magnetic flux about 12 h before and after the event. We
find that 80% of the identified CMEs (29 out of a total of 36 events)
show small--scale flux changes before the event, usually flux emergence
or flux disappearance. In 20% of the cases we find no signature of
photospheric flux changes.
Title: Sunspot Umbral Oscillations: Results from SOHO JOP097
Authors: O'Shea, E.; Muglach, K.; Fleck, B.
Bibcode: 2003csss...12..601O
Altcode:
We present results of an ongoing analysis of time series data, which
were obtained in the context of the Joint Observing Program (JOP) 97 of
the year 2000. This JOP included the Coronal Diagnostic Spectrometer
(CDS) and the Michelson Doppler Imager (MDI) instrument, both part of
SOHO, the TRACE satellite and various ground based observatories. We
show evidence for apparently upwardly propagating in a sunspot umbra
which we suggest are due to magnetoacoustic waves. These waves manifest
themselves as oscillations in lines ranging in temperature from the
upper photosphere/chromosphere to the corona. To our knowledge this
is the first time umbral oscillations have been conclusively seen in
coronal lines. This research is part of the European Solar Magnetometry
Network (ESMN) supported by the EU through the TMR programme.
Title: A Search for High Frequency Oscillations with TRACE
Authors: Muglach, Karin
Bibcode: 2003ANS...324...14M
Altcode: 2003ANS...324..B10M
No abstract at ADS
Title: Dynamics of solar active regions. I. Photospheric and
chromospheric oscillations observed with TRACE
Authors: Muglach, K.
Bibcode: 2003A&A...401..685M
Altcode:
I present results of an international joint observing campaign,
which was carried out in September 1999 and 2000, to study the
oscillatory behaviour of active regions (ARs). In this contribution
I will concentrate on oscillations in the higher layers of the solar
atmosphere as observed with the UV filters of the Transition Region and
Coronal Explorer (TRACE). I present the distribution of oscillatory
power of two extended active regions. I find a number of well-known
chromospheric dynamic phenomena such as running penumbral waves,
enhanced 5 min power in the plage and network regions and additional
3 min power in the internetwork. In addition, I find that the 3 min
power in the surroundings of the AR is decreased, an effect that has
not been observed before. From the topology of the magnetic field I
infer that this can be explained by an interaction of the acoustic
wavefield with the expanding magnetic field of the active region.
Title: Ultraviolet Observations of Periodic Annular Intensity
Fluctuations Propagating around Sunspots
Authors: Georgakilas, A. A.; Muglach, K.; Christopoulou, E. B.
Bibcode: 2002ApJ...576..561G
Altcode:
We analyze UV observations of an isolated sunspot taken with the
Transition Region and Coronal Explorer. We produced ``space/time
slice images,'' which reveal periodic, inward-propagating, intensity
fluctuations in the inner photospheric penumbra and periodic,
outward-propagating, annular intensity fluctuations in the outer
penumbra and the area around the sunspot. The average propagation
velocity of the inward- and outward-propagating intensity flows is about
0.5 and 1 km s-1, respectively, and the distance between
subsequent crests is about 2500 km. Using observations obtained with
the Michelson Doppler Imager, we found propagating magnetic field
enhancements that present a spatial and temporal coherence with the
UV intensity fluctuations. We have not observed any waves similar or
related to the chromospheric 5 minute waves. Based on observations
taken with the Transition Region and Coronal Explorer and the Michelson
Doppler Imager (MDI) on board the Solar and Heliospheric Observatory.
Title: Temporal and spatial variations of the magnetic field vector
in sunspots
Authors: Settele, A.; Sigwarth, M.; Muglach, K.
Bibcode: 2002A&A...392.1095S
Altcode:
In order to look for magnetic field vector oscillations in sunspots we
used data measured with the Advanced Stokes Polarimeter at the Dunn
Solar Telescope. We analyzed two time series of 65 and 110 min that
were taken by scanning repeatedly a 6" 24 x 75" field of view, while
obtaining the full Stokes vector in the lines FeI 630.15 nm and 630.25
nm. An inversion was carried out and a Fast Fourier Transform (FFT)
analysis was used to find oscillatory phenomena. We discuss possible
unwanted effects that lead to apparent magnetic field oscillations and
find an average amplitude of (B, psi ) 5.8 G/0.23o rms by
excluding these effects, which also means that only 6% and 22% of the
two sunspot umbrae respectively remained for analysis. If we smooth
the power spectra over 2x2 pixels, all significant power disappears.
Title: Oscillations above sunspots: Evidence for propagating waves?
Authors: O'Shea, E.; Muglach, K.; Fleck, B.
Bibcode: 2002A&A...387..642O
Altcode:
We present results of an analysis of time series data observed in
sunspot umbral regions. The data were obtained in the context of
the SOHO Joint Observing Program (JOP) 97 in September 2000. This
JOP included the Coronal Diagnostic Spectrometer (CDS) and the
Michelson Doppler Imaging (MDI) instrument, both part of SOHO, the
TRACE satellite and various ground based observatories. The data
was analysed by using both Fourier and wavelet time series analysis
techniques. We find that oscillations are present in the umbra at all
temperatures investigated, from the temperature minimum as measured by
TRACE 1700 Å up to the upper corona as measured by CDS Fe Xvi 335 Å
(log T=6.4 K). Oscillations are found to be present with frequencies in
the range of 5.4 mHz (185 s) to 8.9 mHz (112 s). Using the techniques
of cross-spectral analysis time delays were found between low and high
temperature emission suggesting the possibility of both upward and
downward wave propagation. It is found that there is typically a good
correlation between the oscillations measured at the different emission
temperatures, once the time delays are taken into account. We find
umbral oscillations both inside and outside of sunspot plume locations
which indicates that umbral oscillations can be present irrespective
of the presence of these sunspot plumes. We find that a number of
oscillation frequencies can exist co-spatially and simultaneously
i.e. for one pixel location three different frequencies at 5.40,
7.65 and 8.85 mHz were measured. We investigate the variation of the
relative amplitudes of oscillation with temperature and find that
there is a tendency for the amplitudes to reach a maximum at the
temperature of O Iii (and less typically O V and Mg Ix) and then to
decrease to reach a minimum at the temperature of Mg X (log T=6.0 K),
before increasing again at the temperature of Fe Xvi. We discuss a
number of possible theoretical scenarios that might explain these
results. From a measurement of propagation speeds we suggest that
the oscillations we observe are due to slow magnetoacoustic waves
propagating up along the magnetic field lines.
Title: Height and dynamics of the quiet solar chromosphere at the limb
Authors: Muglach, K.; Schmidt, W.
Bibcode: 2001A&A...379..592M
Altcode:
In this paper we present observations of He I 1083.0 nm, He D_3
587.6 nm and Hβ 486.1 nm taken at various positions at the solar
limb. We determine and compare the emission of the lines in terms
of line-parameters. The height of the chromosphere as seen in the
helium lines varies in space and time and reaches values between
1100 and 1800 km above the continuum and is the same for both helium
lines within the errors of the measurement. From a time-sequence of
slit-spectra of about 23 min we study the oscillation signature of
the chromosphere near the solar limb. We find velocity oscillations
in He I 1083.0 nm that do not drop to zero near the limb as would be
expected of vertically oriented oscillations, we even get horizontal
oscillations in the off-limb emission data of both helium lines.
Title: Active Region Oscillations: Results from SOHO JOP 097
Authors: O'Shea, E.; Fleck, B.; Muglach, K.; Sütterlin, P.
Bibcode: 2001AGUSM..SH41A02O
Altcode:
We present here an analysis of data obtained in a sunspot region,
using the Coronal Diagnostic Spectrometer (CDS) on SOHO. These data
were obtained in the context of the Joint Observing Program (JOP)
97 which, together with CDS, included the Michelson Doppler Imaging
(MDI) instrument on SOHO, the TRACE satellite and various ground
based observatories, e.g. the DOT on La Palma. Using the lines of
Fe XVI 335, Mg IX 368, He I 584, O III 599, Mg X 624 and O V 624 of
CDS time series data were obtained in the pore and plage regions of
sunspots associated with active regions AR 9166, 9166 and 9169 between
September 19-29 2000. In addition to the time series datasets we also
obtained 240 arcsec x 240 arcsec raster images of the sunspot regions
examined. Using different time series analysis techniques we analyse
the different periods of oscillation found in time series datasets and
present the results here. This research is part of the European Solar
Magnetometry Network supported by the EC through the TMR programme.
Title: Magnetic field oscillations in sunspots and active regions
Authors: Balthasar, Horst; Collados, Manuel; Muglach, Karin
Bibcode: 2001ESASP.464..163B
Altcode: 2001soho...10..163B
In order to investigate the oscillatory behaviour of the magnetic
field in sunspots and pores, full Stokes measurements of 1.56 μm
iron lines have been performed using the Tenerife Infrared Polarimeter
(TIP) at the German Vacuum Tower Telescope on Tenerife. As expected,
velocity oscillations have power peaks at five minutes. First results
for temporal variations of the magnetic field show that they occur in
locally restricted areas in sunspots. Periods in the five minute range
are preferred. In addition, we investigate magnetograms taken with
the Michelson Doppler Imager (MDI) on SOHO. Intensity images in white
light and around 160 nm were obtained with TRACE as well. Intensity
power is strongly with TRACE as well. Intensity power is strongly
suppressed in the sunspot area, although we find powerpeaks in the
five and three minute ranges.
Title: Inversion of Stokes Profiles with Artificial Neural Networks
Authors: Carroll, T. A.; Balthasar, H.; Muglach, K.; Nickelt, I.
Bibcode: 2001ASPC..236..511C
Altcode: 2001aspt.conf..511C
No abstract at ADS
Title: Free-fall Downflow Observed in HE I 1083.0 Nanometers and Hβ
Authors: Schmidt, W.; Muglach, K.; Knölker, M.
Bibcode: 2000ApJ...544..567S
Altcode:
In a short time sequence of simultaneously observed slit spectra
of He I 1083.0 nm and Hβ we find the signature of material flowing
toward the solar surface with up to 42 km s-1, in addition
to material which is almost at rest. The constant acceleration of the
moving material is about 200 m s-2. These multiple velocities
occur in a small region of about 5'' in a plage region. We
observe a highly dynamical phenomenon which lasts a few minutes. The
duration and constant acceleration suggest free fall of matter
unobstructed by magnetic structures or along vertical field lines.
Title: Oscillations in a solar pore
Authors: Balthasar, H.; Collados, M.; Muglach, K.
Bibcode: 2000AN....321..121B
Altcode:
Temporal variations of a solar pore were observed at the ground based
Vacuum Tower Telescope (VTT) on Tenerife and with the satellite
TRACE. At the VTT Stokes I and V of the iron line at 1.56 mu m,
originating in the deep photosphere, was measured. TRACE delivered
UV images at 170 nm which show chromospheric continuum. In a part of
the pore we find oscillations of the magnetic field in the 5 minute
range. Velocities derived from shifts of the Stokes V profiles show
5 minutes everywhere in the pore, but the coherence of magnetic field
and velocities is low. The intensity at 170 nm varies with 3 minutes,
and for a part of the whole time series additionally with 4 minutes.
Title: Dynamics of Chromiospheric and Transition Region Lines Observed
with SOHO/SUMER and the GCT/Tenerife
Authors: Muglach, K.; Fleck, B.; Schühle, U.; Stolpe, F.; Foing,
B. H.; Wilhelm, K.
Bibcode: 2000AdSpR..25.1731M
Altcode:
High-resolution spectroscopic observations of the quiet Sun have been
carried out in September 1996 at the German Gregory Coudé Telescope
(GCT) in Tenerife and in May 1997 with the SUMER instrument onboard
SOHO. Time sequences of spectra in the visible and near infrared
as well as in the ultraviolet have been taken, covering a range of
heights from the solar photosphere up into the transition region. In
this contribution we present the dynamical behaviour observed at the
various heights in the solar atmosphere
Title: Waves in the Quiet Sun's Chromosphere
Authors: Muglach, K.; Fleck, B.
Bibcode: 1999ESASP.446..499M
Altcode: 1999soho....8..499M
High resolution spectroscopic observations of the quiet sun have been
carried out in May 1997 with the SUMER instrument onboard of SOHO. Nine
hour time sequences at disk center in various UV lines have been taken,
covering a range of height between the solar chromosphere and the
transition region. In this contribution we will present the dynamics we
find in the various heights/temperature regimes in the solar atmosphere.
Title: Scientific highlights from the Solar and Heliospheric
Observatory
Authors: Martens, P. C. H.; Muglach, K.
Bibcode: 1999ASSL..243..325M
Altcode: 1999sopo.conf..325M
No abstract at ADS
Title: Simultaneous Observations with the GCT and SoHO: High Velocity
Events in the Upper Chromosphere
Authors: Muglach, K.; Sütterlin, P.
Bibcode: 1998ASPC..155..341M
Altcode: 1998sasp.conf..341M
No abstract at ADS
Title: Polar plumes and streamers from 1994 and 1998 eclipses
Authors: Foing, B. H.; Duvet, L.; Muglach, K.; Wiik, J. E.; Beaufort,
T.; Maurice, E.
Bibcode: 1998ESASP.421..273F
Altcode: 1998sjcp.conf..273F
No abstract at ADS
Title: The Helium Spectrum in the Quiet Sun: The January 16/17 and
May 7-13 1997 Coordinated SOHO/Ground-Based Observational Campaigns
Authors: Andretta, Vincenzo; Jordan, Stuart D.; Muglach, Karin;
Garcia, Adriana; Jones, Harrison P.; Penn, Matthew J.; Soltau, Dirk
Bibcode: 1998ASPC..155..336A
Altcode: 1998sasp.conf..336A
No abstract at ADS
Title: Investigating the Formation of the Helium Spectrum in the
Solar Atmosphere
Authors: Andretta, Vincenzo; Jordan, Stuart D.; Muglach, Karin;
Garcia, Adriana; Jones, Harrison P.; Soltau, Dirk
Bibcode: 1998ASPC..154..559A
Altcode: 1998csss...10..559A
We present the first results of coordinated observations with SOHO
(Solar Heliospheric Observatory) and ground-based observatories aimed
at investigating the mechanisms responsible for the formation of helium
lines in the quiescent solar atmosphere. The observations described
here were taken on 7-13 May 1997; the SOHO instruments involved were
CDS, SUMER and EIT, while ground-based support was provided by the
German Vacuum Tower Telescope on Tenerife (He 1 lambda10830 and Ca 2
lambda8498 spectra-spectroheliograms), Coimbra Solar Observatory (Hα
spectroheliograms), and NASA/NSO Vacuum Tower Telescope on Kitt Peak
(Ca 2 lambda8542 spectra-spectroheliograms and polarimetry).
Title: Solar Oscillations in CO at 4.6 Microns
Authors: Livingston, W.; Solanki, S.; Muglach, K.; Wallace, L.
Bibcode: 1998ASPC..135..186L
Altcode: 1998hcsp.conf..186L
The fundamental band lines of CO originate in the solar temperature
minimum and lower cool parts of the chromosphere. We have observed
velocity and intensity oscillations in the quiet sun disk center
and extreme limb, sunspots, and plage. We have also looked for CO
oscillations in the Sun-as-a-star (but detect nothing). We compare the
power spectra of these various features, noting well separated 3 min and
5 min peaks. We interpret our observations in terms of the models of
Carlsson and Stein (1995), and Solanki, et al., (1994). Active Region
Seismology: Results from TON Project Bala Balachandran (Dept. Physics,
National Tsing Hua University, Hsinchu, Taiwan 30043, R.O.C.) Taiwan
Oscillation Network (TON) is a ground based observation facility
for the study of solar oscillations. The data consists of full-disc
K-line images taken at every minute. Using the 512 images time series,
we have tried to infer the location of the magnetic field below the
photosphere using the property of the active regions to absorb the
p-mode power. Two consecutive days, one just when the magnetic flux
appears on the surface and the other the day before the emergence, were
analysed. For this, an annular region of 15 deg. around the region of
emerging flux was chosen for the analysis. The modes were decomposed
into incoming and outgoing waves and the absorption coefficient was
calculated as the fractional difference of the two types. We found
that the absorption is stronger after the emergence of the flux and
the flux was at a depth of about 4000 km below the surface just before
its appearance on the surface; that is about 15 hrs before. It was also
reported earlier by other groups that the quiet sun exhibits acoustic
emission. It is believed to be an observational effect and the cause is
yet to find out. We have carried out a systematic analysis of the quiet
sun emission using 512 images. The analysis is similar to the active
region study, but the region of interest is the solar disc centre. We
found that there exists negative absoption or emission for most modes
and the negative absorption increases with the angular distance from
the centre of the sun.
Title: Multiple velocities observed in HeI 1083 nm
Authors: Muglach, K.; Schmidt, W.; Knölker, M.
Bibcode: 1997SoPh..172..103M
Altcode: 1997SoPh..172..103S; 1997ESPM....8..103M
We present a time sequence of slit spectra of Hei 1083.03 nm (and Hβ)
taken with the German Vacuum Tower Telescope at Tenerife. We find the
signature of an onset of a downflow accelerating up to 42 km/s . The
Hei 1083.03 nm line splits into two well separated components during
the event, one of which shows the usual absorption profile of material
which is almost at rest. We calculate the velocity, line depth and
area of both line profiles. Possible explanations for these observed
multiple velocities are discussed.
Title: The beat of the solar chromosphere's cold heart.
Authors: Solanki, S. K.; Livingston, W.; Muglach, K.; Wallace, L.
Bibcode: 1996A&A...315..303S
Altcode:
The cold heart of the solar chromosphere is best investigated using
fundamental band lines of carbon monoxide, CO, at 4.7μm. We have
obtained time series of CO spectra in the quiet sun and in active-region
plage at the solar limb and at disk centre. In addition, we have
recorded time series in sunspot umbrae located near disk centre. The
power spectra and RMS amplitudes of the quiet-sun oscillations at
disk centre and at the limb are not compatible with a generally
hot chromosphere which is periodically cooled, but support recent
suggestions that the low chromosphere is pervasively cool, interspersed
with hot, possibly shocked material. In the plage the CO oscillations
provide indirect evidence for the expansion of hot material (probably
inside magnetic elements) with height. In umbrae the CO lines exhibit
well-separated 3min and 5min peaks. We also present spectra of the phase
shift between velocity and intensity oscillations of CO lines. At disk
centre in the quiet sun the phase shift is on the whole similar to that
seen in atomic lines formed near the classical temperature minimum,
although with some properties peculiar to CO. In plages the quality
of the phase shift is marginal, but suggests either large radiative
damping or propagating waves in the 4 mHz frequency range. Finally,
in sunspots the phase shift resembles that of atomic chromospheric
lines in some umbrae.
Title: Polarimetry of Solar Pores
Authors: Sütterlin, P.; Schröter, E. H.; Muglach, K.
Bibcode: 1996SoPh..164..311S
Altcode:
We address the magnetic field structure of solar pores. The data
were obtained at the Gregory Coudè telescope at Izaña using
the AT1 CCD camera system to observe pores with three spectral
lines: one magnetically sensitive line, recording all 4 Stokes
profiles, and two g = 0 lines where only the intensity profiles
were measured. The data reduction included the standard procedure
(removing dark current and flatfielding) as well as destretching of
the polarimetric spectra and removing the non-magnetic straylight by
means of a 2-d deconvolution of the observed intensity variation using
a Lucy-Richardson restoration algorithm. In the following analysis we
first determined the temperature- and pressure stratification of the
pore using the g = 0 lines and then applied an inversion of the Stokes
profiles to get the parameters of the magnetic field. Across the pore
we find a strong variation of the resulting field strength as well as
of the inclination and the azimuth, consistent with the assumption of
a canopy forming in the higher atmosphere.
Title: Oscillations in Active Plage Regions as Observed in 1.56
Micron Lines
Authors: Muglach, K.; Solanki, S. K.; Livingston, W. C.
Bibcode: 1995itsa.conf..387M
Altcode:
No abstract at ADS
Title: Preliminary properties of pores derived from 1.56 micron lines
Authors: Muglach, K.; Solanki, S. K.; Livingston, W. C.
Bibcode: 1994ASIC..433..127M
Altcode:
No abstract at ADS
Title: Infrared lines as probes of solar magnetic features. I -
A many-line analysis of a network region
Authors: Muglach, K.; Solanki, S. K.
Bibcode: 1992A&A...263..301M
Altcode:
The results are presented of an analysis of a Fourier transform
spectrometer Stokes I and V spectrum in the H band of a solar network
region. From a many-line statistical analysis of the measured Stokes F
profiles, it is concluded that there is no evidence for s systematic
up or downflow greater than 200-300 m/s within the magnetic element
of the observed region. The Stokes V profiles in the H band show
a blue-red asymmetry having the same sign as in the visible, but
a smaller magnitude. The lines with g(eff) greater than about 1.5
are more or less completely Zeeman split in the observed region, and
only lines with g(eff) values well below unity can be considered to
be in the weak-field regime. An analysis based on radiative transfer
calculations of 16 selected spectral lines in a flux tube model shows
that a thin tube with a field strength of 2050 G at tau (1.6) = 1 ,
corresponding to 1500 G at z = 0, fits the profiles best.
Title: Flux tube diagnostics based on the Stokes V profiles of
infrared H-band lines.
Authors: Muglach, K.; Solanki, S. K.
Bibcode: 1991sopo.work..489M
Altcode:
Stokes V profiles of the unblended Fe I lines in the wavelength range
1.5 - 1.8 μ (H-band) observed in the solar network are analysed. The
data are consistent with an absence of stationary flows larger than
0.3 km s-1. The infrared Stokes V profiles are asymmetric
in the same sense as lines in the visible, but tend to be of smaller
magnitude, in particular the area asymmetry. The widths of the Stokes
V profiles are consistent with kG field strengths. Finally, model
calculations allow an upper limit of 2 to be set on the continuum
intensity of small magnetic features relative to the quiet Sun.
Title: Flux tube diagnostics based on infrared H-band lines.
Authors: Muglach, K.; Solanki, S. K.
Bibcode: 1990AGAb....5...45M
Altcode:
No abstract at ADS