explanation blue bibcodes open ADS page with paths to full text
Author name code: martin
ADS astronomy entries on 2022-09-14
=author:"Martin, Sara F." OR =author:"Martin, S.F."
---------------------------------------------------------
Title: Evolving Classifications of Solar Prominences
Authors: Martin, Sara F.
2018cosp...42E2187M Altcode:
Classification schemes with main classes and subclasses began with
Sechi in 1875 who categorized prominences mostly from their shapes. With
the aid of spectroheliograms and photography, the number of different
categories of prominences maximized with Petit from 1925-1950 who
added classes according their dynamics, and relationships to active
regions and solar flares. With the recognition that not all prominences
seen at the limb corresponded to features seen against the disk, many
observers began referring to disk prominences as "filaments." With
the greater abundance of data enabled by the use of birefringent,
interference filters and time-lapse photography, many attempts
were made through the 1960s to created physically significant
prominence (filament) classifications as cited in the two books
on solar prominences by Tandberg-Hanssen. Reversal of the trend for
increasingly complex classifications began in the 1950s after invention
of the magnetograph. Filaments in Hα_ were all found to lie between
areas of opposite polarity, line-of-sight magnetic fields. Features,
such as flare loops, spicules, and surges acquired separate identities
and no longer needed to be classified as prominences. Observations with
increased spatial resolution allowed the identity of fine thread-like
structure within the basic spine and barb structure of filaments. The
recognition of chirality in the threads of filaments and of fibrils in
their filament channels enabled the unifying of all filaments under
the name channel filaments (channel prominences). 304Å observations
aided detection of greater numbers of coronal cloud prominences,
funnel prominences, and coronal rain. Funnel prominences and coronal
cloud prominence are deduced to be the same basic structures seen from
different perspectives but not all coronal rain comes from coronal
cloud prominences. Therefore, prominence classifications are reduced
to three physically-different phenomena: channel prominences, coronal
cloud prominences and coronal rain. An open question is whether all
features called coronal rain are fundamentally the same.
---------------------------------------------------------
Title: Observational Evidence of Shallow Origins for the Magnetic
Fields of Solar Cycles - a review
Authors: Martin, Sara F.
2018FrASS...5...17M Altcode:
Observational evidence for the origin of active region magnetic fields
has been sought from published information on extended solar cycles,
statistical distributions of active regions and ephemeral regions,
helioseismology results, positional relationships to supergranules,
and fine-scale magnetic structure of active regions and their sunspots
during their growth. Statistical distributions of areas of ephemeral and
active regions blend together to reveal a single power law. The shape of
the size distribution in latitude of all active regions is independent
of time during the solar cycle, yielding further evidence that active
regions of all sizes belong to the same population. Elementary bipoles,
identified also by other names, appear to be the building blocks of
active regions; sunspots form from elementary bipoles and are therefore
deduced to develop from the photosphere downward, consistent with
helioseismic detection of downflows to 3-4 Mm below sunspots as well as
long-observed downflows from chromospheric/coronal arch filaments into
sunspots from their earliest appearance. Time-distance helioseismology
has been effective in revealing flows related to sunspots to depths
of 20 Mm. Ring diagram analysis shows a statistically significant
preference for upflows to precede major active region emergence and
downflows after flux emergence but both are often observed together
or sometimes not detected. From deep-focus helioseismic techniques for
seeking magnetic flux below the photosphere prior major active regions,
there is evidence of acoustic travel-time perturbation signatures
rising in the limited range of depths of 42-75 Mm but these have
not been verified or found at more shallow depths by helioseismic
holographic techniques. The development of active regions from
clusters of elementary bipoles appears to be the same irrespective
of how much flux an active region eventually develops. This property
would be consistent with the magnetic fields of large active regions
being generated in the same way and close the same depth as small
active regions in a shallow zone below the photosphere. All evidence
considered together, understanding the origins of the magnetic fields
of solar cycles boils down to learning how and where elementary bipoles
are generated beneath the photosphere.
---------------------------------------------------------
Title: A Survery of the Correlation between Filament Chirality and
Sigmoid Handedness
Authors: V, A.; Hazra, S.; Martin, S. F.; Martens, P. C.
2017AGUFMSH51C2498V Altcode:
Sigmoid regions on the Sun are often the regions that cause Coronal
Mass Ejections (CMEs). Large CMEs most often have filaments that
erupt with them. This study focuses on the statistical relevance of
the shape of the sigmoid and the chirality of the filament residing in
these sigmoids. The study further extends to the relation between the
directionality of filaments and the Earth-directed CMEs. Sigmoid data
from Savcheva et al. (2014) between 2007 and 2012 and a compilation of
data using the HEK Sigmoid Sniffer (Martens et al. 2012) along with
Hinode XRT Soft X-ray images were used for analyzing data between
2013 and 2017. Hence this dataset consists of almost one solar cycle
of data. A similar study done previously by Martens et al. (2013)
analysed data for a solar cycle using an Advanced Automated Filament
Detection & Characterization Code (Bernasconi, Rust & Hakim
2005). Considering that automated chirality detection is not foolproof,
we present this study which uses manual determination of chirality
for accuracy using high resolution chromospheric images. Mainly full
disk images of soft X-ray obtained from Hinode XRT (X-Ray Telescope)
have been used to find and ensure the S or Z shape of sigmoids. H-alpha
images obtained from BBSO and Kanzelhohe Solar Observatory (KSO) are
used in determining the chirality of filaments. The resolutions of BBSO
and KSO data are 1k and 4k respectively. A comparison of the analysis of
the chirality of filaments using both data will be presented. Although
KSO gives a 4k resolution, it is still difficult to determine the
chirality of small filaments. For this reason, high resolution images of
H-alpha chromospheric filaments obtained from Helio Research and Solar
Observing Optical Network (SOON) have been used for further analysis
of chirality of those filaments that were undeterminable using the
BBSO or KSO full disk images. The results of the comparison using
the different resolutions are shown. The results of the correlation
between sigmoid shape and filament chirality are also shown. Further,
these results are used in determining the correlation with Earth
directed CMEs and those that cause geo-magnetic storms. Savacheva,
A. S., McKillop, S. C., McCauley, P. I., et al., 2014, 289Bernasconi,
P. N., Rust, D. M., & Hakim, D., 2005, Sol. Phys., 228, 97 Martens,
P., Yeates, A., & Pillai, K., 2013, IAU, 3000
---------------------------------------------------------
Title: Transequatorial Coronal Cloud Prominences Versus
Transequatorial Channel Prominence
Authors: Martin, S. F.; Daga, K.
2016AGUFMSH43C2584M Altcode:
Seven transequatorial channel prominences were identified in the
McCauley et al. catalog of erupting prominences from June 2010
- Sep 2014 (2015 Solar Phys. 290, 1703). A comparable number of
transequatorial coronal cloud prominences were identified in the Martin
et al. study of coronal cloud prominences from May 2010 - April 2012
(IAU Symposium 320, 2016, p. 276). The similar locations of these two
subsets of two primary prominence classifications make them nearly
ideal candidates for comparison of their properties. Coronal rain is an
integral dynamic in coronal cloud prominences whereas counterstreaming
motion is characteristic of channel prominences. The two subsets are
representative of the the differing magnetic structure, mass origin,
evolution, and environmental properties of coronal cloud prominences
and channel prominences in general. These samples illustrate how
coronal cloud prominences require different models than channel
prominences. However, both types of prominences appear to be dependent
upon pre-existing environments that largely control their structure
and dynamics.
---------------------------------------------------------
Title: The Chirality and Lifetime of Filaments and Filament Channels
Authors: Daga, Komal; Martin, Sara F.
2016shin.confE.139D Altcode:
Two of the most useful properties of individual filaments are not
adequately understood. These are chirality and lifetime. The goal
in this study is to analyze chirality and lifetime of filament and
filament channels over a period of 2 years during the rise of current
solar cycle 24 from May 2010 to May 2012. Here we report on the results
of cataloging for the initial months. <P />Systematic documentation of
filament chirality will greatly help in forecasting the related helicity
of CMEs and their interaction with the magnetic field of Earth. Better
knowledge of filament lifetime is needed to anticipate their eruption
along with the occurrence of CMEs. We are documenting lifetimes of
filaments because their durations are much shorter than previously
reported. By studying their lifetimes we gain a better understanding
of the close relationship between filament evolution and CME buildup
because they evolve and erupt hand-in-hand. <P />We have determined the
chirality of filaments using direct and indirect methods. The direct
method is based on the slant of filament barbs observed in Hα. The
main indirect method employs the chirality of filament channels as
seen in coronal cells in 193 Å images. Another indirect method is
based on the skew of flare loops and coronal loops. By comparing these
different techniques we are able to learn which method or combination
of methods is most effective. <P />We find very few exceptions to the
hemispheric pattern of dextral filaments in the northern hemisphere
and sinistral filaments in the southern hemisphere. The exceptions
to the hemispheric pattern is primarily due to differential rotation
acting on active regions whose relative locations are more north-south
than east-west of each other. Most exceptions are recognizable at the
time filaments develop. We confirm the overall orientation of CME flux
ropes in space can be anticipated from their associated filaments.
---------------------------------------------------------
Title: Distinguishing between coronal cloud prominences and channel
prominences and their associations with solar and stellar flares
Authors: Martin, Sara F.; Engvold, Oddbjorn; Lin, Yong; da Silva,
Jacqueline Alves
2016IAUS..320..278M Altcode:
To better understand the differences between coronal cloud prominences
and channel prominences, we systematically identified and analyzed
coronal cloud prominences recorded in SDO/AIA images at 304 Å from
2010 May 20 through 2012 April 28. For the 225 cases identified,
their numbers vary directly with the sunspot number. Their durations
are typically less than 3 days. Their most frequent maximum height is
90,000 + and - 10,000 km. We offer our hypothesis that many coronal
cloud prominences originate from some of the mass of previously erupted
filaments ejected high out of their filament channels; subsequently part
of this mass falls and collects in leaky magnetic troughs among coronal
magnetic fields which constrain the leaked mass to slowly drain downward
along curved trajectories where it appears as coronal rain. Currently
there is inadequate evidence for a convincing correspondence between
either coronal cloud prominences or channel prominences with stellar
prominences detected to date.
---------------------------------------------------------
Title: Distinguishing Between Different Types of Prominences
Associated with Solar Flares
Authors: Martin, Sara F.; Engvold, Oddbjorn; Lin, Yong
2015IAUGA..2255962M Altcode:
In the early days of solar astronomy, any feature that extended above
the solar limb was called a prominence. However, many such coronal
features have been sufficiently studied to justify more specific
names such as flare loops, surges, and flaring arches. Each of these
named phenomena has different properties and involves different
physical processes from other solar prominences. If we exclude
these well-identified phenomena, we find that the majority of the
remaining prominences can be grouped into only two categories that
are distinctly different from each other. The main two types are (1)
channel prominences or channel filaments when seen against the solar
disk and (2) coronal cloud prominences, including narrow, down-flows
named coronal rain. We illustrate the many significant differences
between channel prominences and coronal cloud prominences. One of the
fundamental differences is that channel prominences often have patterns
of mass motions useful in anticipating many flares while coronal cloud
prominences tend to occur hours after major solar flares. We also raise
the question of whether the much taller coronal cloud prominences could
have a counterpart in prominences on solar-like stars with magnetic
fields of greater magnitude than the Sun.
---------------------------------------------------------
Title: Re-interpreting Prominences Classified as Tornadoes
Authors: Martin, Sara F.; Venkataramanasastry, Aparna
2015TESS....131206M Altcode:
Some papers in the recent literature identify tornado prominences
with barbs of quiescent prominences while papers in the much older
historic literature include a second category of tornado prominence that
does not correspond to a barb of a quiescent prominence. The latter
are described as prominence mass rotating around a nearly vertical
axis prior to its eruption and the rotation was verified by spectral
measurements. From H alpha Doppler-shifted mass motions recorded at
Helio Research or the Dutch Open Telescope, we illustrate how the
apparent tornado-like motions, identified with barbs, are illusions
in our mind’s eye resulting from poorly resolved counterstreaming
threads of mass in the barbs of quiescent prominences. In contrast,
we confirm the second category of rotational motion in prominences
shortly before and during eruption. In addition, we identify this
second category as part of the late phase of a phenomenon called the
roll effect in erupting prominences. In these cases, the eruption
begins with the sideways rolling of the top of a prominence. As the
eruption proceeds the rolling motion propagates down one leg or both
legs of the prominence depending on whether the eruption is asymmetric
or symmetric respectively. As an asymmetric eruption continues, the
longer lasting leg becomes nearly vertical and its rotational motion
also continues. If only this phase of the eruption was observed, as
in some historic cases, it was called a tornado prominence. However,
when we now observe entire eruptions in time-lapse sequences, the
similarity to terrestrial tornadoes is lost. We conclude that neither
prominence barbs, that give the illusion of rotation, nor the cases
of true rotational motion, in the legs of erupting prominences, are
usefully described as tornado prominences when the complete prominence
structure or complete erupting event is observed.
---------------------------------------------------------
Title: Questioning Many Mysteries
Authors: Martin, Sara F.
2015SoPh..290.1011M Altcode: 2015SoPh..tmp...35M
The first section of this memoir queries my formative years. Indirectly
I address the question, did my childhood and early years make a
difference in my choice of career? Why and how did I begin my journey
to becoming a scientist? Did I choose the field of solar astronomy or
did circumstances dictate it for me? In the second section, I travel
through my work environments and experiences, talking about interactions
and aspects of being a scientist that do not appear in our research
papers. What parts of my research were happenstances and what parts
did I plan? What does it feel like to be on scientific quests? Using
examples in my journey, I also turn to questions that have intrigued
me throughout my sojourn as a solar astronomer. How do scientific
discoveries come about? What factors lead to little discoveries? And
what factors lead to major exciting discoveries? Are there timely
questions we do not think to ask? How can small, seemingly scattered
pieces of knowledge suddenly coalesce into a deeper understanding -
what is called the "Aha!" experience - the times when our mental light
switches on, and with child-like wonder we behold a "big picture"?
---------------------------------------------------------
Title: The Magnetic Field Structure of Prominences from Direct and
Indirect Observations
Authors: Martin, Sara F.
2015ASSL..415..205M Altcode:
Solar prominences are fascinating and unique magnetic structures
in our solar system. From all observational evidence to date, their
intricate structure, dynamics and plasma parameters are apparently
all derived from observable source magnetic fields on the Sun. While
the processes that convert these source fields to prominence magnetic
fields are not fully understood, there is a trail of observational
information that gives many clues about how prominence magnetic fields
are derived from or related to these source fields and maintained for
various lengths of time through multiple processes, over a wide range
of spatial scales. This chapter highlights that trail of observational
information for two primary magnetic types with very different origins:
channel prominences and coronal cloud prominences.
---------------------------------------------------------
Title: Two Categories of Apparent Tornado-like Prominences
Authors: Martin, Sara F.; Venkataramanasastry, Aparna
2014AAS...22441403M Altcode:
Two categories of solar prominences have been described in the
literature as having a pattern of mass motions and/or a shape
similar to terrestrial tornados. We first identify the two categories
associated with prominences in the historic literature and then show
that counterparts do exist for both in recent literature but one
has not been called a tornado prominence. One category described as
being similar to tornados is associated with the barbs of quiescent
filaments but barbs appear to have rotational motion only under special
conditions. H alpha Doppler observations from Helio Research confirm
that this category is an illusion in our mind’s eye resulting from
counterstreaming in the large barbs of quiescent filaments. The second
category is a special case of rotational motion occurring during the
early stages of some erupting prominences, in recent years called the
roll effect in erupting prominences. In these cases, the eruption begins
with the sideways rolling of the top of a prominence. As the eruption
proceeds the rolling motion propagates down one leg or both legs of an
erupting prominence depending on whether the eruption is asymmetric or
symmetric respectively. As an asymmetric eruption proceeds, the longer
lasting leg becomes nearly vertical and has true rotational motion. If
only this phase of the eruption was observed, as in the historic cases,
it was called a tornado prominence and spectra recorded in these cases
provide proof of the rotational motion. When one observes an entire
eruption which exhibits the rolling motion, as accomplished at Helio
Research, the similarity to a tornado is lost because the event as a
whole has quite a different nature and the analogy to a terrestrial
tornado not longer appears suitable or helpful in understanding the
observed and deduced physical processes. Our conclusion is that there
are no solar prominences with motions that are usefully described as
tornado or tornado-like events aside from the fun of observing some
prominence barbs whose mass motions yield a fascinating illusion of
rotational motion under special conditions.
---------------------------------------------------------
Title: Apparent Solar Tornado-Like Prominences
Authors: Panasenco, Olga; Martin, Sara F.; Velli, Marco
2014SoPh..289..603P Altcode: 2013arXiv1307.2303P
Recent high-resolution observations from the Solar Dynamics Observatory
(SDO) have reawakened interest in the old and fascinating phenomenon
of solar tornado-like prominences. This class of prominences was
first introduced by Pettit (Astrophys. J.76, 9, 1932), who studied
them over many years. Observations of tornado prominences similar to
the ones seen by SDO had already been documented by Secchi (Le Soleil,
1877). High-resolution and high-cadence multiwavelength data obtained
by SDO reveal that the tornado-like appearance of these prominences is
mainly an illusion due to projection effects. We discuss two different
cases where prominences on the limb might appear to have a tornado-like
behavior. One case of apparent vortical motions in prominence spines
and barbs arises from the (mostly) 2D counterstreaming plasma motion
along the prominence spine and barbs together with oscillations along
individual threads. The other case of apparent rotational motion is
observed in a prominence cavity and results from the 3D plasma motion
along the writhed magnetic fields inside and along the prominence cavity
as seen projected on the limb. Thus, the "tornado" impression results
either from counterstreaming and oscillations or from the projection
on the plane of the sky of plasma motion along magnetic-field lines,
rather than from a true vortical motion around an (apparent) vertical or
horizontal axis. We discuss the link between tornado-like prominences,
filament barbs, and photospheric vortices at their base.
---------------------------------------------------------
Title: Rapid Formation and Disappearance of a Filament Barb
Authors: Joshi, Anand D.; Srivastava, Nandita; Mathew, Shibu K.;
Martin, Sara F.
2013SoPh..288..191J Altcode:
We present observations of an activated quiescent filament obtained in
Hα from the high-resolution Dutch Open Telescope (DOT) on 20 August
2010. The filament developed a barb in 10 min, which disappeared
within the next 35 min. A data set from the DOT spanning 2 h was used
to analyse this event. Line-of-sight velocity maps were constructed
from the Doppler images, which reveal flows in filament spine during
this period. Photospheric magnetograms were used from the Helioseismic
and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO)
to determine the changes in magnetic flux in the region surrounding the
barb location. The analysis shows flows in the filament spine towards
the barb location preceding its formation, and flows in the barb towards
the spine during its disappearance. Magnetograms reveal patches of
minority polarity flux close to the end of the barb at its greatest
elongation. The flows in the spine and barbs are along numerous threads
that compose these typical filament structures. The flows are consistent
with field-aligned threads and demonstrate that the replacement time
of the mass in barbs, and by inference, in the spine is very rapid.
---------------------------------------------------------
Title: Origins of Rolling, Twisting, and Non-radial Propagation of
Eruptive Solar Events
Authors: Panasenco, Olga; Martin, Sara F.; Velli, Marco; Vourlidas,
Angelos
2013SoPh..287..391P Altcode: 2012arXiv1211.1376P; 2012SoPh..tmp..321P
We demonstrate that major asymmetries in erupting filaments and CMEs,
namely major twists and non-radial motions are typically related to
the larger-scale ambient environment around eruptive events. Our
analysis of prominence eruptions observed by the STEREO, SDO, and
SOHO spacecraft shows that prominence spines retain, during the
initial phases, the thin ribbon-like topology they had prior to
the eruption. This topology allows bending, rolling, and twisting
during the early phase of the eruption, but not before. The combined
ascent and initial bending of the filament ribbon is non-radial
in the same general direction as for the enveloping CME. However,
the non-radial motion of the filament is greater than that of the
CME. In considering the global magnetic environment around CMEs,
as approximated by the Potential Field Source Surface (PFSS) model,
we find that the non-radial propagation of both erupting filaments and
associated CMEs is correlated with the presence of nearby coronal holes,
which deflect the erupting plasma and embedded fields. In addition,
CME and filament motions, respectively, are guided towards weaker
field regions, namely null points existing at different heights in
the overlying configuration. Due to the presence of the coronal hole,
the large-scale forces acting on the CME may be asymmetric. We find
that the CME propagates usually non-radially in the direction of least
resistance, which is always away from the coronal hole. We demonstrate
these results using both low- and high-latitude examples.
---------------------------------------------------------
Title: Using Coronal Cells to Infer the Magnetic Field Structure
and Chirality of Filament Channels
Authors: Sheeley, N. R., Jr.; Martin, S. F.; Panasenco, O.; Warren,
H. P.
2013ApJ...772...88S Altcode: 2013arXiv1306.2273S
Coronal cells are visible at temperatures of ~1.2 MK in Fe XII
coronal images obtained from the Solar Dynamics Observatory and Solar
Terrestrial Relations Observatory spacecraft. We show that near a
filament channel, the plumelike tails of these cells bend horizontally
in opposite directions on the two sides of the channel like fibrils
in the chromosphere. Because the cells are rooted in magnetic flux
concentrations of majority polarity, these observations can be used
with photospheric magnetograms to infer the direction of the horizontal
field in filament channels and the chirality of the associated magnetic
field. This method is similar to the procedure for inferring the
direction of the magnetic field and the chirality of the fibril pattern
in filament channels from Hα observations. However, the coronal cell
observations are easier to use and provide clear inferences of the
horizontal field direction for heights up to ~50 Mm into the corona.
---------------------------------------------------------
Title: Elementary Bipoles, the Building Blocks of Active Regions
Authors: Martin, Sara F.; Mkhitaryan, M.
2013SPD....44..109M Altcode:
New magnetic flux even in very small active regions appears as a
succession of tiny bipolar magnetic fields that successively and
concurrently appear in tight clusters. These smallest observable
bipoles were initially called “elementary bipoles” when first
seen in videomagnetograms from the Big Bear Solar Observatory (Martin,
S. F. 1990, “Elementary Bipoles of Active Regions and Ephemeral Active
Regions” Societa Astronomica Italiana, Memorie 61, 293). The magnetic
flux of each pole of elementary bipole is approximately the same and
measures 1018 Mx or less depending on both the spatial resolution
and sensitivity of the magnetograph with which the measurements are
made. The two poles initially occur very close together and rapidly
move in opposite directions with a typical speed of 3 km/sec. The
elementary bipoles within a cluster tend to emerge with similar
orientations. The most common orientation of the elementary bipoles
at any given time determines the “orientation” of a whole simple
bipolar region. In this paper we illustrate and compare 6 clusters
of elementary bipoles during the development of a large active region
less than 2 days old when observed in Hα at the Dutch Open Telescope
along with HMI/SDO. Each cluster of elementary bipoles behaves like
a single simple bipolar active region. However the clusters are so
close together that the magnetic flux of each bipolar cluster merges
or cancels with adjacent clusters. The study of elementary bipoles
provides a means of simplifying our understanding of the development
of complex active regions depending on both the spatial resolution and
sensitivity of the magnetograph with which the measurements are made.
---------------------------------------------------------
Title: Footpoint detection and mass-motion in chromospheric filaments
Authors: V, Aparna; Hardersen, P. S.; Martin, S. F.
2013SPD....44...06V Altcode:
A quiescent region on the Sun containing three filaments is used to
study the properties of mass motion. This study determines if the
footpoints or end-points of the filaments are the locations from where
mass gets injected into the filaments. Several hypotheses have been put
forth in the past to determine how a filament acquires mass. Trapping of
coronal mass in the filament channel due to condensation (Martin, 1996)
and injection of mass into the filaments during magnetic reconnection
(Priest, et al., 1995) are some of the speculations. This study looks
for indications for injection of mass via chromospheric footpoints. The
data consists of blue (Hα-0.5 Å) and red (Hα+0.5 Å) wing high
resolution Hα images of the W29N37 region of the Sun taken on Oct
30, 2010, from 1200 - 1600 UT. The Dutch Open Telescope was used to
obtain the data. The images are aligned and animated to see Doppler
motion in the fibrils. Smaller fibrils merge to form longer ones;
barbs appear and disappear in one of the long filaments and is seen
moving along the length of the filament. A region with no typical
filament-like absorption feature is observed to be continuously
receiving mass. Fibrils appear to be converging from opposite sides
along what appears to be a neutral line; mass motion is seen in these
fibrils as well. An eruption occurs in a region of fibrils lumped
together at the end of the first hour (1300 UT) followed by plage
brightening at 1430 UT near one of the filament regions. Helioviewer
(Panasenco, et al., 2011) is used for aligning the images; GIMP is
used for precision alignment and animation. Each frame in the sequence
is studied carefully to note changes in the filament regions. The
footpoints of the filaments are determined by the changes observed
in the position of the filament ‘legs’ in each frame. Variations
in the magnetic polarity corresponding to changes observed in the
chromosphere are analyzed using HMI magnetograms. Bright and dark points
on the magnetogram surrounding the filaments are examined for possible
locations of footpoints. The HMI images are overlaid with Stonyhurst
grids and full disk Hα images to improve the accuracy in determining
the location of the footpoints.Abstract (2,250 Maximum Characters): A
quiescent region on the Sun containing three filaments is used to study
the properties of mass motion. This study determines if the footpoints
or end-points of the filaments are the locations from where mass gets
injected into the filaments. Several hypotheses have been put forth
in the past to determine how a filament acquires mass. Trapping of
coronal mass in the filament channel due to condensation (Martin, 1996)
and injection of mass into the filaments during magnetic reconnection
(Priest, et al., 1995) are some of the speculations. This study looks
for indications for injection of mass via chromospheric footpoints. The
data consists of blue (Hα-0.5 Å) and red (Hα+0.5 Å) wing high
resolution Hα images of the W29N37 region of the Sun taken on Oct
30, 2010, from 1200 - 1600 UT. The Dutch Open Telescope was used to
obtain the data. The images are aligned and animated to see Doppler
motion in the fibrils. Smaller fibrils merge to form longer ones;
barbs appear and disappear in one of the long filaments and is seen
moving along the length of the filament. A region with no typical
filament-like absorption feature is observed to be continuously
receiving mass. Fibrils appear to be converging from opposite sides
along what appears to be a neutral line; mass motion is seen in these
fibrils as well. An eruption occurs in a region of fibrils lumped
together at the end of the first hour (1300 UT) followed by plage
brightening at 1430 UT near one of the filament regions. Helioviewer
(Panasenco, et al., 2011) is used for aligning the images; GIMP is
used for precision alignment and animation. Each frame in the sequence
is studied carefully to note changes in the filament regions. The
footpoints of the filaments are determined by the changes observed
in the position of the filament ‘legs’ in each frame. Variations
in the magnetic polarity corresponding to changes observed in the
chromosphere are analyzed using HMI magnetograms. Bright and dark
points on the magnetogram surrounding the filaments are examined for
possible locations of footpoints. The HMI images are overlaid with
Stonyhurst grids and full disk Hα images to improve the accuracy in
determining the location of the footpoints.
---------------------------------------------------------
Title: Formation of the Coronal Cloud Prominences Inside Magnetic
Funnels
Authors: Panasenco, Olga; Velli, Marco; Martin, Sara F.
2013enss.confE..94P Altcode:
We describe observations of coronal cloud prominences with the Solar
Dynamics Observatory and STEREO. Observations of this phenomenon
during the month of September 2012, in similar locations but over
widely separated periods, are used to investigate the reasons for
the appearance of coronal cloud prominces at different times in the
same location. In particular, we focus on the large scale structure of
the background magnetic field. Using a potential field source-surface
extrapolation to compute the coronal field from photospheric maps, we
find that coronal cloud prominences always form after filament eruptions
and CMEs have occurred nearby. The location of the cloud prominence
coincides with a magnetic field region which appears to be open but
rapidly expanding, an open field with a funnel structure. Part of the
plasma from the neighboring eruption falling back towards the sun is
captured and accumulates in these field regions of strong expansion
of the field. The plasma suspension at heights of 0.3 Rs, coinciding
with the largest gradients in the field naturally lead to a diamagnetic
hypothesis for the force counteracting gravity. We study the evolution
of the funnel-like open fields during several solar rotations and find
a direct relation between funnels and the presence of coronal clouds
at great heights in the solar corona.
---------------------------------------------------------
Title: Solar Tornado Prominences: Plasma Motions Along Filament Barbs
Authors: Panasenco, Olga; Velli, Marco; Martin, Sara F.; Rappazzo,
Franco
2013enss.confE..93P Altcode:
Recent high-resolution observations from the Solar Dynamic Observatory
(SDO) have reawakened interest in the old and fascinating phenomenon
of solar tornado prominences. This class of prominences was first
introduced by E. Pettit in 1932, who studied them over many years
up to 1950. High resolution and high cadence multi-wavelength data
obtained by SDO reveal that the tornado-like properties of these
prominences are mainly an illusion due to projection effects. We
show that counterstreaming plasma motions with projected velocities
up to +/- 45 km/sec along the prominence spine and barbs create a
tornado-like impression when viewed at the limb. We demonstrate that
barbs are often rooted at the intersection between 4-5 supergranular
cells. We discuss the observed oscillations along the vertical parts
of barbs and whether they may be related to vortex flows coming
from the convection downdrafts at the intersection of supergranules
(and possibly smaller convective cells) in the photosphere and their
entrained magnetic field. The unwinding of magnetic threads near the
photosphere via reconnection might be a source of the waves which are
observed as oscillations in prominence barbs.
---------------------------------------------------------
Title: The Build-Up to Eruptive Solar Events Viewed as the Development
of Chiral Systems
Authors: Martin, S. F.; Panasenco, O.; Berger, M. A.; Engvold, O.;
Lin, Y.; Pevtsov, A. A.; Srivastava, N.
2012ASPC..463..157M Altcode: 2012arXiv1212.3646M
When we examine the chirality or observed handedness of the
chromospheric and coronal structures involved in the long-term build-up
to eruptive events, we find that they evolve in very specific ways to
form two and only two sets of large-scale chiral systems. Each system
contains spatially separated components with both signs of chirality,
the upper portion having negative (positive) chirality and the lower
part possessing positive (negative) chirality. The components within
a system are a filament channel (represented partially by sets of
chromospheric fibrils), a filament (if present), a filament cavity,
sometimes a sigmoid, and always an overlying arcade of coronal
loops. When we view these components as parts of large-scale chiral
systems, we more clearly see that it is not the individual components
of chiral systems that erupt but rather it is the approximate upper
parts of an entire evolving chiral system that erupts. We illustrate the
typical pattern of build-up to eruptive solar events first without and
then including the chirality in each stage of the build-up. We argue
that a complete chiral system has one sign of handedness above the
filament spine and the opposite handedness in the barbs and filament
channel below the filament spine. If the spine has handedness, the
observations favor its having the handedness of the filament cavity and
coronal loops above. As the separate components of a chiral system form,
we show that the system appears to maintain a balance of right-handed
and left-handed features, thus preserving an initial near-zero net
helicity. We further argue that the chiral systems allow us to identify
key sites of energy transformation and stored energy later dissipated in
the form of concurrent CMEs, erupting filaments and solar flares. Each
individual chiral system may produce many successive eruptive events
above a single filament channel. Because major eruptive events
apparently do not occur independent of, or outside of, these unique
chiral systems, we hypothesize that the development of chiral systems:
(1) are fundamental to the occurrence of eruptive solar events and (2)
preserve an approximate balance between positive and negative helicity
(right and left-handed chirality) while preparing to release energy
in the form of CMEs, erupting filaments, and flares.
---------------------------------------------------------
Title: Large-field high-resolution mosaic movies
Authors: Hammerschlag, Robert H.; Sliepen, Guus; Bettonvil, Felix
C. M.; Jägers, Aswin P. L.; Sütterlin, Peter; Martin, Sara F.
2012SPIE.8444E..06H Altcode:
Movies with fields-of-view larger than normal for high-resolution
telescopes will give a better understanding of processes on the
Sun, such as filament and active region developments and their
possible interactions. New active regions can influence, by their
emergence, their environment to the extent of possibly serving
as an igniter of the eruption of a nearby filament. A method to
create a large field-of-view is to join several fields-of-view into
a mosaic. Fields are imaged quickly one after another using fast
telescope-pointing. Such a pointing cycle has been automated at the
Dutch Open Telescope (DOT), a high-resolution solar telescope located
on the Canary Island La Palma. The observer can draw with the computer
mouse the desired total field in the guider-telescope image of the
whole Sun. The guider telescope is equipped with an H-alpha filter and
electronic enhancement of contrast in the image for good visibility of
filaments and prominences. The number and positions of the subfields
are calculated automatically and represented by an array of bright
points indicating the subfield centers inside the drawn rectangle of
the total field on the computer screen with the whole-sun image. When
the exposures start the telescope repeats automatically the sequence of
subfields. Automatic production of flats is also programmed including
defocusing and fast motion over the solar disk of the image field. For
the first time mosaic movies were programmed from stored information
on automated telescope motions from one field to the next. The mosaic
movies fill the gap between whole-sun images with limited resolution
of synoptic telescopes including space instruments and small-field
high-cadence movies of high-resolution solar telescopes.
---------------------------------------------------------
Title: High-Resolution Observations of a Filament showing Activated
Barb
Authors: Joshi, Anand; Martin, Sara F.; Mathew, Shibu; Srivastava,
Nandita
2012cosp...39..841J Altcode: 2012cosp.meet..841J
Analysis of a filament showing an activated barb using observations from
the Dutch Open Telescope (DOT) on 2010 August 20 are presented. The DOT
takes Doppler images in Hα, among other wavelengths, in a region about
110 × 110 arcsec^{2} in area, at a cadence of 30~seconds. The offline
image restoration technique of speckle reconstruction is applied to
obtain diffraction limited images. The filament developed a new barb
in 10~minutes, which disappeared within the next 35~minutes. Such
a rapid formation and disappearance of a filament barb is unusual,
and has not been reported earlier. Line-of-sight velocity maps
were constructed from the Doppler images of the target filament. We
observe flows in the filament spine towards the barb location prior
to its formation, and flows in the barb towards the spine during its
disappearance. Photospheric magnetograms from Heliospheric Magnetic
Imager on board the Solar Dynamics Observatory, at a cadence of
45~seconds, were used to determine the changes in magnetic flux in
the region surrounding the barb location. The variation of magnetic
flux in this duration supports the view that barbs are rooted in minor
magnetic polarity. Our analysis shows that barbs can be short-lived and
formation and disappearance of the barb was associated with cancellation
of magnetic flux.
---------------------------------------------------------
Title: Coronal Holes, Filament Channels And Filaments: Observations
Of The Self-organization Of The Coronal Magnetic Field Over Solar
Cycles 23 And 24
Authors: Panasenco, Olga; Martin, S. F.; Velli, M.; Berger, M. A.
2012AAS...22020202P Altcode:
The aim of this work is to understand the relationship between coronal
holes, coronal hole boundaries and one of the other main features
of the coronal magnetic field, namely filament channels, regions
of highly sheared magnetic fields overlying photospheric polarity
reversal boundaries. The well-developed filament channel is a necessary
ingredient for filament formation. Polar coronal holes and polar crown
filament channels always seem to exist together, and even during periods
of weakest activity, when nothing indicates the presence of polar crown
channels on the solar disk, polar crown prominences appear at the limb
proving their existence. Does a similar symbiotic relationship exist
also for other coronal holes? There is some indication that for middle
and low latitude coronal holes different configurations occur depending
on the polarity of the hole relative to the pole. If the polarity is
the same, then a coronal pseudostreamer configuration can form with
twin filament channels at its base, while if the polarity is opposite,
the right conditions for the development of the filament channels
and filaments following the hemispheric helicity rule arise. Using
SOHO/EIT and MDI, STEREO/EUVI, SDO/AIA and HMI instruments we trace the
formation and mutual evolution of coronal holes and their symbiotic
filament channels up to and including filament formations, eruptions
and subsequent reformations during period 1998-2012 (solar cycles 23
and 24).
---------------------------------------------------------
Title: Coronal Mass Ejections from Magnetic Systems Encompassing
Filament Channels Without Filaments
Authors: Pevtsov, Alexei A.; Panasenco, Olga; Martin, Sara F.
2012SoPh..277..185P Altcode:
Well-developed filament channels may be present in the solar atmosphere
even when there is no trace of filament material inside them. Such
magnetic systems with filament channels without filaments can result
in coronal mass ejections that might appear to have no corresponding
solar surface source regions. In this case study, we analyze CMEs on
9 August 2001 and 3 March 2011 and trace their origins to magnetic
systems with filament channels containing no obvious filament material
on the days around the eruptions.
---------------------------------------------------------
Title: Coronal Holes and Filaments: Life in Symbiosis
Authors: Panasenco, O.; Velli, M.; Martin, S. F.; Berger, M. A.
2011AGUFMSH12A..05P Altcode:
The aim of this work is to understand the relationship between
coronal holes, coronal hole boundaries and one of the other main
features of the coronal magnetic field, namely filament channels,
regions of highly sheared magnetic fields overlying photospheric
polarity reversal boundaries. The well developed filament channel
is a necessary ingredient for the filament formation. Polar coronal
holes and polar crown filament channels always seem to exist together,
and even during periods of weakest activity, when nothing indicates
the presence of polar crown channels on the solar disk, polar crown
prominences appear at the limb proving their existence. Does a similar
symbiotic relationship exist also for other coronal holes? There is
some indication that for middle and low latitude coronal holes different
configurations occur depending on the polarity of the hole relative to
the pole. If the polarity is the same, then a coronal pseudostreamer
configuration can form with twin filament channels at its base, while if
the polarity is opposite, the right conditions for the development of
the filament channels and filaments following the hemispheric helicity
rule arise. Using STEREO/EUVI, SDO/AIA and HMI instruments we trace the
formation and mutual evolution of coronal holes and their symbiotic
filament channels up to and including filament formations, eruptions
and subsequent reformations during many solar rotations in 2010-2011.
---------------------------------------------------------
Title: The Disappearing Solar Filament of 2003 June 11: A Three-body
Problem
Authors: Balasubramaniam, K. S.; Pevtsov, A. A.; Cliver, E. W.;
Martin, S. F.; Panasenco, O.
2011ApJ...743..202B Altcode:
The eruption of a large quiescent filament on 2003 June 11 was preceded
by the birth of a nearby active region—a common scenario. In this
case, however, the filament lay near a pre-existing active region
and the new active region did not destabilize the filament by direct
magnetic connection. Instead it appears to have done so indirectly
via magnetic coupling with the established region. Restructuring
between the perturbed fields of the old region and the filament
then weakened the arcade overlying the midpoint of filament, where
the eruption originated. The inferred rate (~11° day<SUP>-1</SUP>)
at which the magnetic disturbance propagates from the mature region
to destabilize the filament is larger than the mean speed (~5º-6°
day<SUP>-1</SUP>) but still within the scatter obtained for Bruzek's
empirical relationship between the distance from a newly formed
active region to a quiescent filament and the time from active region
appearance to filament disappearance. The higher propagation speed in
the 2003 June 11 case may be due to the "broadside" (versus ”end-on")
angle of attack of the (effective) new flux to the coronal magnetic
fields overlying a central section of the axis of the filament.
---------------------------------------------------------
Title: Origins of Rolling, Twisting and Non-radial Propagation of
Eruptive Solar Events
Authors: Martin, Sara F.; Panasenco, Olga
2011sdmi.confE.105M Altcode:
We demonstrate that major asymmetries in erupting filaments and CMEs
are not only related to each other but that major twists and non-radial
motions typically are related to the larger, more global environment
around eruptive events. This overarching result grew out of a number of
earlier studies that we now encapsulate within the bigger picture. If
a filament erupts non-radially, as frequently happens, the top of
its spine first bends to one side and evolves into a sideways rolling
motion. As shown by 304 Angstrom observations from SOHO and STEREO and
earlier H alpha Doppler observations, the rolling motion propagates
down the legs of erupting filaments resulting in the large scale
twists commonly observed in them. The initial rolling initiates twist
of opposite chirality in the two legs. In addition to the observed
absence of twist in the pre-eruptive state, further evidence that
the energy creating the twist comes from above was found in Doppler
shifts; the rotational motions in the legs of erupting filaments are
not only opposite in sign to each other but the twists in both legs
are opposite in sign to that required if the observed sense of twist
were generated at the feet or in the legs of the erupting filament. We
next demonstrate that the combined ascent and initial bending is
non-radial in the same general direction as for the surrounding
CME. However, the non-radial motion of the filament is greater than
that of the CME. In considering the global environment around CMEs,
as can be approximated by the Potential Field Source Surface (PFSS)
Model, we found that both erupting filaments and their surrounding
CMEs are non-radial only in the direction away from a nearby coronal
hole and toward local and global null points. Due to the presence of
the coronal hole, the global forces on the CME are asymmetric. The CME
propagates non-radially in the direction of least resistance and that
is always away from the coronal hole as we demonstrate by comparing low
latitude and high latitude examples. Through modeling and comparison
with observed events, we anticipate that major twists and non-radial
motions in erupting prominences and CMEs will become predictable to
the extent that their environments are well-defined and measurable.
---------------------------------------------------------
Title: Stereoscopic Analysis of 31 August 2007 Erupting Prominence
Authors: Liewer, P. C.; Hall, J. R.; de Jong, E. M.; Martin, S. F.;
Panasenco, O.
2010AGUFMSH51A1658L Altcode:
The dramatic prominence eruption of 31 August 2007 and the associated
CME were well observed by both STEREO spacecraft, separated by 28° at
that time. The eruption occurred as the filament reach the West limb
as seen by STEREO B; the filament, the coronal cavity and the CME
were all clearly observed. We use tie-pointing and triangulation to
determine the 3D trajectories of the erupting filament (seen in EUVI
and COR1) and the associated CME and cavity (seen in COR1 and COR2)
and we compare these trajectories. From the EUVI 304 data, it can
be seen that the prominence footpoints change loctions during the
early stages of the eruption and, using stereoscopy, we find that
the new footpoints correspond to locations of EUVI 171 “endpoint
brightenings” discussed by Wang, Muglach and Kleim (ApJ, 2009) as
marking the outer edge of the transient coronal holes. Our observations
are consistent with their interpretation of the brightenings resulting
from magnetic reconnection between the erupting prominence magnetic
field and the overlying coronal arcade.
---------------------------------------------------------
Title: On dynamical properties of filament channels
Authors: Martin, S. F.; Panasenco, O.
2010MmSAI..81..662M Altcode:
We discuss some of the least understood properties of filament
channels. This includes the three-dimensional rotational configuration
at their centers and the importance of cancelling magnetic fields
to their configuration. Intranetwork magnetic fields play a role
by interacting with network magnetic fields and these interactions
probably provide the ubiquitous fibrils of the chromosphere which
continuously adjust to the configurations of the dominant network
magnetic fields. Supergranules play a role by severely restricting the
intermingling of opposite polarity magnetic fields and controlling the
diffusion rates whereby opposite polarities network magnetic fields
slowly converge and form long and long-lived, polarity reversal
boundaries where filaments can form.
---------------------------------------------------------
Title: Filaments, filament channels and their visibility during the
present solar minimum
Authors: Panasenco, O.; Martin, S. F.; Panasenco, A.
2009AGUFMSH11A1494P Altcode:
An unexpected aspect of the current long solar minimum between solar
cycles 23 and 24 is that polar crown prominences have been observed
nearly continuously above the solar limb. However, many of the same
polar crown prominences have had only small sections visible against the
chromosphere in H-alpha and these sections change from day to day. The
presence of much more extensive mass than seen in H-alpha is certain
because filaments are seen against the disk much more completely in 304A
than in H-alpha. These differences in filament visibility offer a good
opportunity to test our concepts of the relationship between filament
mass seen in H-alpha and the rate of cancelling magnetic fields in
the photosphere. We know from previous observations and theory over
more than 20 years that the existence of filaments is closely related
to canceling magnetic fields observed at the photosphere. We have made
the hypothesis that there is a threshold in the rate of canceling fields
below which filaments are not visible against the solar disk in H-alpha
but this concept has not been tested. We are testing this hypothesis
by calculating the rates of canceling magnetic flux for the different
filaments during their passing across the disk for the current minimum
and previous maximum of 23rd solar cycle. In our analyses we use data
sets from SOHO/MDI, SOHO/EIT, STEREO and ground based observatories.
---------------------------------------------------------
Title: Relating a Prominence Observed from the Solar Optical Telescope
on the Hinode Satellite to Known 3-D Structures of Filaments
Authors: Martin, S. F.; Panasenco, O.; Agah, Y.; Engvold, O.; Lin, Y.
2009ASPC..415..183M Altcode:
We address only a first step in relating limb and disk observations
by illustrating and comparing the spines and barbs of three different
quiescent prominences and filaments observed in Hα by three different
telescopes. Although the appearance of the three quiescent prominences
is quite different, we show that each consists of a spine, barbs
extending from the spine, and arcs at the base of some of the curtains
of barb threads.
---------------------------------------------------------
Title: Interwoven Patterns of Chirality Among Solar Structures:
a Review
Authors: Martin, Sara F.
2009SPD....40.2501M Altcode:
Chirality is the handedness of solar magnetic structures as recognized
in two dimensional solar images or in other solar data revealing
distinct magnetic patterns. This review covers the historical succession
of discoveries of the chirality of solar magnetic structures, beginning
with left and right-handed helical magnetic clouds detected in many
interplanetary coronal mass ejections. This led to the recognition
of corresponding chiralities in coronal loop systems. Separately,
chiral patterns in filaments, filament channels, sunspots, sigmoidal
structures, and flare loop systems were established, interrelated,
and linked to the chirality of coronal loop systems. The result was
the finding that all solar chiral patterns fall into two and only two
larger chiral systems with one system more prevalent in the northern
hemisphere and the other in the southern hemisphere. From chiral
characteristics, along with knowledge or assumptions about the magnetic
field topology, we have the ability to better deduce the helicities
characteristic of many solar structures. Traditionally, helicity is
a property of magnetic fields with strict mathematical definitions in
two well-known forms: twist and writhe. Application of the principle of
the conservation of helicity to chiral systems now leads to more mature
interpretations of the helicity of whole solar magnetic field systems
as well as their components, which together must contain equivalent
amounts of both left and right-handed helicity. From this broadened
perspective, comes a better understanding of why right-handed coronal
loops necessarily exist above filaments with left-handed barbs that
always overly left-handed filament channels and vice versa. Along
with this greater understanding, we are collectively at the point of
learning to better recognize and predict the senses of roll, twist,
and writhe in the axial fields of erupting prominences. These, in turn,
confirm the signs of helicity in associated CMEs and magnetic clouds -
where we began this brief historical journey.
---------------------------------------------------------
Title: A Dual Beam H-alpha Doppler System to Acquire, Analyse and
Anticipate Solar Eruptive Events Directed towards Earth
Authors: Joshi, Anand D.; Mathew, Shibu K.; Srivastava, Nandita;
Martin, Sara F.; Gupta, Sudhir K.
2009arXiv0905.3037J Altcode:
A new instrument with a dual-beam H-alpha Doppler system is being
developed at the Udaipur Solar Observatory (USO) in order to improve
the quality and quantity of data on quiet, activated and erupting
filaments and prominences on the Sun, especially those associated with
geo-effective coronal mass ejections. These data can be potentially used
to construct three-dimensional topology of erupting filaments as they
leave the surface of the Sun and can be compared with multi-wavelength
data obtained from space missions such as STEREO, SOHO, and Hinode. The
characterization of various optical components for the instrument
is being carried out, and some preliminary results are described in
the paper.
---------------------------------------------------------
Title: On small active region filaments, fibrils and surges
Authors: Lin, Y.; Martin, S. F.; Engvold, O.; Rouppe van der Voort,
L. H. M.; van Noort, M.
2008AdSpR..42..803L Altcode:
High resolution Hα images and magnetograms (0.2 arc s) of an active
region were obtained in alternating time series at 42 s cadences
using the Swedish 1-m Solar Telescope on 2004 August 21. The Hα
filtergrams reveal an active region filament and surges consisting
of thread-like structures which have widths similar to the widths of
chromospheric fibrils, both recorded down to the resolution limit in
the best images. All observed structures in the active region appear
highly dynamic. Fibrils show counterstreaming strongly resembling the
counterstreaming threads in filaments. Streaming, along the threads
of surges extending more than 10 arc s, is higher in speed (∼20
km s<SUP>-1</SUP>) than in the filament and fibrils and appears to
flow independently over and above the chromospheric fibrils. Blue
shifts seen in the Hα Dopplergrams confirm the outward mass motion
of the surges. However, in at least one case, we also see simultaneous
downflows from the same site but in the opposite direction and downward
toward the chromosphere. We suggest that the site between these
two outward and downward flows identifies the place where magnetic
reconnection could occur and thereby cause of the surge. This appears
to imply that the reconnection site is in the high chromosphere or
low corona.
---------------------------------------------------------
Title: A Method of Resolving the 180-Degree Ambiguity by Employing
the Chirality of Solar Features
Authors: Martin, S. F.; Lin, Y.; Engvold, O.
2008SoPh..250...31M Altcode: 2008SoPh..tmp..105M
The 180-degree ambiguity in magnetic field direction along polarity
reversal boundaries can be resolved often and reliably by the
chiral method. The chiral method requires (1) identification of
the chirality of at least one solar feature related to a polarity
reversal boundary along which the field direction is sought and (2)
knowledge of the polarity of the network magnetic field on at least
one side of the polarity reversal boundary. In the context of the
Sun, chirality is an observable signature of the handedness of the
magnetic field of a solar feature. We concentrate on how to determine
magnetic field direction from chirality definitions and illustrate
the technique in eight examples. The examples cover the spectrum of
polarity boundaries associated with filament channels and filaments
ranging from those connected with active regions to those on the
quiet Sun. The applicability of the chiral method to all categories of
filaments supports the view that active region filaments and quiescent
filaments are the extreme ends in a continuous spectrum of filaments.
---------------------------------------------------------
Title: Topological Analyses of Symmetric Eruptive Prominences
Authors: Panasenco, O.; Martin, S. F.
2008ASPC..383..243P Altcode:
Erupting prominences (filaments) that we have analyzed from Hα
Doppler data at Helio Research and from SOHO/EIT 304 Å, show strong
coherency between their chirality, the direction of the vertical and
lateral motions of the top of the prominences, and the directions
of twisting of their legs. These coherent properties in erupting
prominences occur in two patterns of opposite helicity; they constitute
a form of dynamic chirality called the “roll effect." Viewed from
the positive network side as they erupt, many symmetrically-erupting
dextral prominences develop rolling motion toward the observer along
with right-hand helicity in the left leg and left-hand helicity in
the right leg. Many symmetricaly-erupting sinistral prominences, also
viewed from the positive network field side, have the opposite pattern:
rolling motion at the top away from the observer, left-hand helical
twist in the left leg, and right-hand twist in the right leg. We have
analysed the motions seen in the famous movie of the “Grand Daddy"
erupting prominence and found that it has all the motions that define
the roll effect. From our analyses of this and other symmetric erupting
prominences, we show that the roll effect is an alternative to the
popular hypothetical configuration of an eruptive prominence as a
twisted flux rope or flux tube. Instead we find that a simple flat
ribbon can be bent such that it reproduces nearly all of the observed
forms. The flat ribbon is the most logical beginning topology because
observed prominence spines already have this topology prior to eruption
and an initial long magnetic ribbon with parallel, non-twisted threads,
as a basic form, can be bent into many more and different geometrical
forms than a flux rope.
---------------------------------------------------------
Title: Filament Substructures and their Interrelation
Authors: Lin, Y.; Martin, S. F.; Engvold, O.
2008ASPC..383..235L Altcode:
The main structural components of solar filaments, their spines, barbs,
and legs at the extreme ends of the spine, are illustrated from recent
high-resolution observations. The thread-like structures appear to
be present in filaments everywhere and at all times. They are the
fundamental elements of solar filaments. The interrelation of the
spines, barbs and legs are discussed. From observations, we present
a conceptual model of the magnetic field of a filament. We suggest
that only a single physical model is needed to explain filaments in
a continuous spectrum represented by active region filaments at one
end and quiescent filaments at the other end.
---------------------------------------------------------
Title: Chromospheric and coronal manifestations of photospheric
cancelling magnetic fields
Authors: Panasenco, Olga; Martin, Sara F.; Engvold, Oddbjorn
2008cosp...37.2336P Altcode: 2008cosp.meet.2336P
We discuss observable changes in solar features interpreted as
evidences of the transfer of magnetic fields from the photosphere
to the chromosphere and corona. In the photospheric level, new
or decayed active region magnetic fields of opposite polarity
encounter each other and cancel along a pre-existing polarity
reversal boundary. Concurrently, in the chromospheric level of
the solar atmosphere, the cancelling fields appear to lead to the
creation and maintenance of a filament channel. The channel is
identified by systematic changes in the orientation of fibrils
in the chromosphere. We deduce that invisible extensions of the
magnetic fields of the chromospheric fibrils into the corona could
represent the beginning of the formation of a filament cavity in the
low corona, before and/or during the initial appearance of a filament
threads. When the filament channel is fully developed, such that there
is a local magnetic field aligned with the polarity reversal boundary,
the cancelling fields are then associated with the transfer of plasma,
as well as magnetic field, into the low corona. We suggest this plasma
is observed as new filament threads.
---------------------------------------------------------
Title: STEREO 3D Data of the Fast Formation of the Ribbon-Like
Prominences and Their Dynamics During Eruption
Authors: Panasenco, O.; Martin, S. F.
2007AGUFMSH41B..07P Altcode:
We have analyzed STEREO/SECCHI/EUVI Helium 304Å data and created
3-dimensional geometrical models for the two erupting prominences
observed by STEREO. 3D STEREO movies, made by combining views from
the two spacecraft, allow us to understand the true 3D structure of
the prominences before and during eruption. In a movie from 12 May
2007 we can see the fast filling of the existing filament channel
by plasma. This fast formation of the prominence allows us to trace
in time and space the appearance of the main structural parts of the
prominence: the barbs and the flat ribbon shape of the whole body of
the prominence. We have analyzed the formation and development these
structures before eruption and the motion of the erupting part of the
prominence during eruption. We found that the motion of the erupting
prominence shows the roll effect of the top of prominence. The STEREO
movie from 16 May 2007 shows us another clear example of the roll effect
during prominence eruption. The observed fast filling of the existing
filament channel by plasma and the quick formation of the prominence
with the ribbon-like geometrical structure, followed by the partial
eruption with the obvious roll effect are the clear evidence of non flux
rope magnetic nature of prominences. Our qualitative model of prominence
formation by cancelling of magnetic flux at the photosphere and magnetic
reconnection in the chromosphere and corona is in agreement with the
STEREO observational facts of formation and eruption of prominences.
---------------------------------------------------------
Title: Comparisons of the Spines of Prominences (Filaments) in Hα
and He II (304Å) Images
Authors: Martin, Sara F.; Engvold, O.; Lin, Y.
2007AAS...21012006M Altcode: 2007BAAS...39..245M
Prominence (filament) spines are being analyzed in Hα images from
ground-based observatories and in He II 304 Αngstrom (Å) images from
the EIT experiment on board the SoHO satellite. Our comparisons show the
spines of quiescent prominences are often longer and slightly taller in
He II 304Å images than seen in Hα images. Spines are also sharper and
more clearly defined in He II 304Å than in Hα images. The prominences
(filaments) in some cases appear earlier and can also last longer in
304Å than in Hα. Examples are shown on the disk and above the limb
where the spines of separate filaments (prominences) merge in 304Å
images before they appear to merge in Hα. In one case, the spine
of a quiescent filament disappears in Hα but remains visible in He
II images. These observations are consistent with our measurements
of a typical quiescent prominence that shows the Hα brightness
decreases with height in the prominence, whereas the brightness at
He II 304Å slightly increases with height. Thus we find that the
spines of quiescent prominences are always more readily visible in
304Å than in Hα. The relative variation of prominence brightness with
height reflects a difference in conditions for excitation of these two
lines. This is consistent with a presumed increase of temperature with
height, in combination with a slight decrease of electron density with
height and with the theory that the He II 304Å line is controlled by
EUV radiation from the surrounding corona, whereas Hα is influenced
by radiation from the chromosphere below. SFM acknowledges support
from NSF grant ATM-0519249 and Y.L. from Norwegian Research Council
grant FRINAT171012.
---------------------------------------------------------
Title: Observations of the Merging of Two Quiescent Filaments
Authors: Mikurda, Katarzyna; Martin, S. F.
2007AAS...210.5302M Altcode: 2007BAAS...39..164M
The two filaments were observed close to disk center in the same field
of view of approximately 9x9 arc. min. The observations were made using
a tunable lithium niobate, narrow band etalon on the 25 cm Martin Solar
Telescope at Helio Research in southern California. One filament was
close to the equator and was oriented nearly east-west and the other, to
the west, was oriented north-south with the north end approximately 120
Mm from the west end of the equatorial filament. Continued observations
were made of these filaments for 2 to 5.5 hours per day between October
10 and 15, 2004. The observations were made at multiple wavelengths
within + and - 1 Å around Hα. <P />We compared Hα centerline images
with data taken by SOHO/EIT at 304A and observed significant differences
in the evolution of the filaments at these wavelengths. For example,
in EIT 304 Å images the two filaments seem to join on October 12,
i.e. about two days earlier than in Hα. Moreover, the observed merging
took longer (over three days) in Hα than in EIT 304 Å images, where
it took place on a single day. The dynamics of the merger event is
demonstrated with Hα and EIT 304 Å movies. <P />The Doppler velocities
calculated from the line wings images before, during and after the
merging event were in the normal range for quiescent filaments. In
our investigation of subsequent SOHO/EIT images at 304 Å we found
no sign of an eruption due to the merging of the filaments. <P />The
contribution of KM was supported under NASA grant NAG5-10852 and SFM
acknowledges NSF grant ATM-0519249.
---------------------------------------------------------
Title: Merging of Filaments in a Dual-Filament System
Authors: Mikurda, K.; Martin, S. F.
2006IAUJD...3E..92M Altcode:
Introduction: The dual filament system merges to form one extended
filament. Methods: The filaments were observed at Helio Research at
multiple wavelengths around Hα using a tunable filter and a narrow
band Fabry-Perot etalon as part of the Joint Observing Campaign
(JOP 178). These observations are used to create two-dimensional
Dopplergrams. The Hα images are compared with data taken onboard the
SOHO (Solar and Heliospheric Observatory) spacecraft (EIT at 304 A and
LASCO C2). The GONG magnetograms provide the information on photospheric
magnetic fields. Results and Discussion: The filaments were observed
on the solar disk between October 10 and 16, 2004. We compare the
morphology of the filament system in Hα and He II line at 304 A
and discuss its evolution. We investigate the photospheric magnetic
flux cancellation rate during the merging process. There is no clear
evidence of an eruption associated with the merging of the filaments
from either EIT or LASCO in contrary to some previous findings.
---------------------------------------------------------
Title: A Simple Method of Resolving the 180 Degree Ambiguity Employing
the Chirality of Solar Features
Authors: Martin, Sara F.; Lin, Y.; Engvold, O.
2006SPD....37.0129M Altcode: 2006BAAS...38..220M
The 180 degree ambiguity in magnetic field direction along polarity
reversal boundaries can be resolved simply and reliably by a technique
that we name "chiral method". For a given polarity boundary, the
chiral method requires identifying the chirality of at least one
solar feature related to the polarity boundary, familiarity with the
one-to-one associations between the chirality of solar features, and
the polarity of the network magnetic field on at least one side of the
polarity boundary. We demonstrate the technique in 6 examples. The
examples cover the spectrum of polarity boundaries associated with
filament channels and filaments ranging from those associated with
active regions to those on the quiet Sun.The applicability of the
chiral method to all categories of filaments supports the view that
active region filaments and quiescent filaments are the extreme
ends in a continuous spectrum of filaments. An example is shown
of a filament where the chirality could not be determined in low
resolution images because of lack of consistency in barb orientation;
however, at high resolution, all threads of this barb were found to
be consistent with just one sense of chirality. The chiral method
is almost universally applicable because many types of data, that
reveal chirality in solar features, are now readily available over the
world-wide web. Solar features that most commonly reveal chirality
are filaments, filament channels, sigmoids, and both quiescent and
dynamic coronal loop systems. Assuming that the chirality of the solar
features is identified correctly, the method is fail-safe and physically
meaningful because chirality is an observational representation of
the helicity and there are clear differences between left-handed and
right-handed solar structures.Support from US NSF grant ATM-0209395
and NASA grant NAG5-10852 are acknowledged for S.F.M. and Y.L.
---------------------------------------------------------
Title: "Coronal Cloud" Prominences And Their Association With Coronal
Mass Ejections
Authors: Lin, Yong; Martin, S. F.; Engvold, O.
2006SPD....37.0121L Altcode: 2006BAAS...38Q.219L
"Coronal cloud" prominences appear to form as bright knots of mass
condensing out of the corona while some of their mass also continuously
drains down along curved streamers to the chromosphere. Movies of such
"suspended cloud" prominences were recorded in Hα by Dunn as early as
the 1950s (1976, Solar Physics 49, 283). They have been also observed
in HeI 10830 Å and EIT 304 Å .Four Hα "coronal clouds" were recorded
at Helio Research (2004/09/16-17, 2004/11/16-17 and 2005/12/12). Their
apparent heights are estimated in the range between 66,000-240,000 km,
much higher than the more common prominences and filaments with spines
and barbs. Near the surface, the downflows accelerate at a typical
speed of 40 km s<SUP>-1</SUP>. By comparing the positions of the
coronal clouds with magnetograms several days prior to or after the
coronal clouds were observed at the limb, we are able to show that the
condensations of mass are located above or adjacent to complex active
regions. The condensations of the fainter coronal clouds have a V-shaped
appearance which suggests to us that these concentrations of mass might
be trapped at junctions of separatrix magnetic surfaces.For each of our
4 cases, LASCO movies show a CME 1-2 days prior to the "coronal clouds"
and encompassing or overlapping the range of latitudes. In one case,
the LASCO movie also shows a downflow after the CME which is radially
above the coronal cloud. We suggest that downflows associated with
CMEs provide the mass for "coronal clouds" formation even though
the downflows are not clearly observed in three of the 4 cases; the
downflows could be blocked from our sight by the LASCO occulting disk
and/or obscured by the more prevalent outflows of mass.Support from
US NSF grant ATM-0209395 and NASA grant NAG5-10852 are acknowledged.
---------------------------------------------------------
Title: Dynamics of an active region filament, fibrils and surges in
high resolution
Authors: Lin, Y.; Martin, S. F.; Engvold, O.; Rouppe van der Voort,
L. H. M.; van Noort, M.
2006cosp...36.3193L Altcode: 2006cosp.meet.3193L
High resolution H alpha and magnetograms 0 2 arc sec of an active region
were obtained in alternating time series at 42 sec cadences using the
Swedish 1-m Solar Telescope on 2004 August 21 The 79 times 52 arcsec
field of view was centered at N11 W5 The H alpha filtergrams reveal an
active region filament and surges consisting of thread-like structures
which have widths similar to the widths of chromospheric fibrils both
recorded down to the resolution limit in the best images All observed
structures in the active region are highly dynamic The flow speeds in
some active filament threads 25 km s -1 are higher than typical speeds
in quiescent filament threads Fibrils show counterstreaming strongly
resembling the counterstreaming threads in filaments The transverse
speeds of mass within fibrils are comparable to the typical speeds
of mass flows in quiescent filament threads sim 10 km s -1 Streaming
along the threads of surges extending more than 10 arc sec is higher
in speed sim 20 km s -1 than in the filament and fibrils and appears
to flow over the chromospheric fibrils Small surges near one end of
the filament appear to flow into the filament thereby mass seems to
be added to the filament Blue shifts seen in the H alpha Dopplergrams
confirm the outward mass motion of the surges However in at least one
case we also see simultaneous red shifts from the same site in the
opposite direction toward the chromosphere We suggest that the site
between these two opposite motions identifies the place where magnetic
---------------------------------------------------------
Title: A theory of the roll effect in prominence eruption
Authors: Choe, G. S.; Cheng, C. Z.; Martin, S. F.
2006cosp...36.3469C Altcode: 2006cosp.meet.3469C
It is often observed in prominence eruptions that the top part of
the prominence ribbon bends in one direction to make the ribbon
horizontally flat Also the legs of the erupting prominence undergo
twisting motions of opposite senses This effect is discovered and named
as roll effect by S F Martin The sense of rolling is found to depend on
the chirality of the prominence The roll effect acts for breaking of the
geometrical symmetry of the system Unless the prominence environment
is systematically asymmetric the symmetry-breaking evolution of a
prominence can hardly be understood in the framework of the conventional
magnetohydrodynamics MHD with isotropic electrical conductivity When
the electrical conductivity is anisotropic the symmetry of the system
is not conserved We investigate the solar magnetic field evolution with
anisotropic electrical conductivity Now the motion of the magnetic field
is not tied to the plasma center of mass motion but has a component
against the current direction Thus the rising motion of the magnetic
field is skewed to a certain direction conditioned by the current
When magnetic reconnection takes place in a magnetic loop or arcade
the direction of the current in the current sheet region and in the
legs of the current sheet is almost opposite to the current direction
in the underlying reconnected loops This explains why the Doppler
shift at the top and outer parts of the erupting prominence is of the
opposite sense to that in the bottom part between the prominence legs
Furthermore this reasoning can account for how the
---------------------------------------------------------
Title: Evidence for the Formation of Faint, High Prominences in the
Aftermath of two Faint CMEs
Authors: Martin, S. F.; Engvold, O.
2005AAS...20720401M Altcode: 2005BAAS...37.1502M
On 16 and 17 September 2004, changes in two unusually high prominences
were recorded for intervals of several hours in the Hα line at Helio
Research using a 10-inch aperture telescope equipped with a narrow band
(1/10 fwhm) filter. The high prominences, each reaching an altitude
200,000 km, appeared above a long low-lying prominence that was
well-observed crossing the limb and had a maximum altitude of 60,000
km. The lower prominence had a horizontal axis and barbs while the
high prominence in Hα consisted of many strands of nearly vertical
structure but with only a few threads with mass streaming downward
close to the chromosphere. Because there were no apparent geometric
properties or mass flows in common between the high prominences and
the low one, it is deduced that the high prominences were associated
with photospheric polarity reversal boundaries and filament channels
that were at least 20-33 degrees beyond the west limb and associated
with a large decaying active region. Additionally, LASCO movies
revealed two faint CMEs on 14 Sep (19:12 UT) and 15 Sep (21:24 UT)
evidently from the backside of the Sun and near the same position
angles as the high prominences. These events were also most likely
related to the polarity reversal boundaries within or on the border
of the large active region beyond the west limb. We suggest that each
of the high prominences developed in the 1-2 day aftermath of each
of the successive CMEs. We further suggest that the prominences are
related to the formation of current sheets anticipated by (Lin and
Forbes 2000) or magnetic interfaces (Lin and van Ballegooijen 2001)
that, in either case, are continuing to evolve one to two days after
the eruptive events. Support from NSF grant ATM-0209395 is acknowledged.
---------------------------------------------------------
Title: Formation of an Extraordinarily Long Filament Channel
Authors: Anderson, M.; Martin, S. F.
2005ASPC..346..201A Altcode:
We analyze an example of how the Sun's surface processes appear to
cause filament channels to evolve from medium-scale into global-scale
phenomena. The channel was nearly linear when it reached a maximum
length of 160 heliographic degrees. Because filament channels need
to be of the same chirality (helicity) to merge and because most
quiescent filaments in the northern and southern hemispheres have
opposite chirality, this example is among the largest that the Sun
could be expected to produce. <P />We focus on filament channels
because they are more fundamental than the filaments that form and
erupt from them. The physical factors and processes that contributed
to the formation and development of the channels from medium-scale into
this global-scale filament were: (1) the presence and diffusion of the
magnetic flux of active regions, (2) canceling magnetic fields, (3)
differential rotation, (4) the pattern of orientation of the magnetic
field bipoles of active regions per hemisphere known as Joy's law, and
(5) the hemispheric chirality pattern for filament channels and their
filaments. We suggest two additional factors, not included in this
study, that might play significant roles in contributing to the overall
form of the giant channels. These are: (7) meridional circulation and
the (8) reconfiguring of solar magnetic fields during all scales of
eruptive events.
---------------------------------------------------------
Title: On the origin and configuration of the 20 March 2003
interplanetary shock and magnetic cloud at 1 AU
Authors: Berdichevsky, D. B.; Richardson, I. G.; Lepping, R. P.;
Martin, S. F.
2005JGRA..110.9105B Altcode: 2005JGRA..11009105B
On 20 March 2003, a forward shock was observed in the near-Earth
solar wind, followed 8 hours later by an interplanetary magnetic cloud
(IMC), in a configuration having several uncommon features: Both were
parts of a 38-hour interval containing transient solar outflows that
occurred in an extended high-speed stream from a Y-shaped extension
of the south polar coronal hole. (In contrast, IMCs, and ejecta
in general, were rarely observed within high-speed streams at low
heliolatitudes during cycle 23.) The most likely solar source for the
IMC is AR 10314, located at S15°, just above the "fork" of the Y-shaped
coronal hole. Several solar flares occurred in this active region on
17-18 March, as well as a succession of four coronal mass ejections
(CMEs). Velocity considerations narrow the most likely source of the
38-hour interval of activity to two CMEs on 17 March 2003 associated
with solar flares at W33° and W39°. The IMC axis had a north-south
orientation, which is unusual for IMCs during this solar cycle. Its
left-handedness implies an association with a left-skewed coronal
arcade, which is less common in the Southern Hemisphere. Considering
the shock observed ahead of the IMC, we conclude based on orientation
and ram pressure arguments that this shock was not driven by the
IMC, as might be presumed, but was the flank of an unrelated shock
that overtook the IMC approximately halfway between Sun and Earth,
heating the plasma and accelerating particles within the IMC. The CME
associated with the X-class flare, at 1208 UT on 18 March in AR 10314
appears to be the solar source for this shock.
---------------------------------------------------------
Title: Sequential Chromospheric Brightenings beneath a Transequatorial
Halo Coronal Mass Ejection
Authors: Balasubramaniam, K. S.; Pevtsov, A. A.; Neidig, D. F.; Cliver,
E. W.; Thompson, B. J.; Young, C. A.; Martin, S. F.; Kiplinger, A.
2005ApJ...630.1160B Altcode:
Analyses of multiwavelength data sets for a solar eruption at ~21:30
UT on 2002 December 19 show evidence for the disappearance of a
large-scale, transequatorial coronal loop (TL). In addition, coronal
manifestations of the eruption (based on SOHO EIT and LASCO images)
include large-scale coronal dimming, flares in each associated active
region in the northern and southern hemispheres, and a halo CME. We
present detailed observations of the chromospheric aspects of this
event based on Hα images obtained with the ISOON telescope. The
ISOON images reveal distant flare precursor brightenings, sympathetic
flares, and, of most interest herein, four nearly cospatial propagating
chromospheric brightenings. The speeds of the propagating disturbances
causing these brightenings are 600-800 km s<SUP>-1</SUP>. The inferred
propagating disturbances have some of the characteristics of Hα
and EIT flare waves (e.g., speed, apparent emanation from the flare
site, subsequent filament activation). However, they differ from
typical Hα chromospheric flare waves (also known as Moreton waves)
because of their absence in off-band Hα images, small angular
arc of propagation (<30°), and their multiplicity. Three of
the four propagating disturbances consist of a series of sequential
chromospheric brightenings of network points that suddenly brighten in
the area beneath the TL that disappeared earlier. SOHO MDI magnetograms
show that the successively brightened points that define the inferred
propagating disturbances were exclusively of one polarity, corresponding
to the dominant polarity of the affected region. We speculate that
the sequential chromospheric brightenings represent footpoints of
field lines that extend into the corona, where they are energized in
sequence by magnetic reconnection as coronal fields tear away from
the chromosphere during the eruption of the transequatorial CME. We
report briefly on three other events with similar narrow propagating
disturbances that were confined to a single hemisphere.
---------------------------------------------------------
Title: Roll Effect in Prominence Eruption Explained by Anisotropic
Electrical Conductivity
Authors: Choe, G. S.; Cheng, C. Z.; Martin, S. F.
2005AGUSMSP44A..01C Altcode:
When a prominence erupts, it generally rises non-radially and the top
part of the prominence ribbon bends in one direction to make the ribbon
horizontally flat. Also the legs of the prominence undergo twisting
motions of opposite senses. This phenomenon was discovered and named as
"role effect" by S. F. Martin. This effect can hardly be understood in
the framework of ideal MHD or MHD with isotropic conductivity. Such
breaking of a geometrical symmetry in the evolution of an initially
symmetric system can take place when the electrical conductivity
is anisotropic. We perform simulations of a solar plasma evolution
with anisotropic electrical conductivity. Now the magnetic field
does not only move together with plasma bulk flows, but also against
electric currents. Thus the rising motion of the field is skewed to one
direction. When magnetic reconnection takes place in a magnetic loop or
arcade, the direction of the current in the current sheet region and in
the region connected to this current sheet by field lines is opposite to
that in the underlying reconnected loops. This explains why the Doppler
shift at the top and outer parts of the erupting prominence is opposite
to that in the bottom part between the prominence legs. Furthermore,
this reasoning can account for how the sign of the roll effect depends
on the chirality of the prominence as observed.
---------------------------------------------------------
Title: Minor Planet Observations [671 Stony Ridge]
Authors: Rogers, J. E.; Brewster, S. C.; Hadlen, D. A.; Hoff, J. M.;
Martin, S. F.; Sable, P. K.; Hadlen, D.
2004MPC..52503...5R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Minor Planet Observations [671 Stony Ridge]
Authors: Rogers, J. E.; Brewster, S. C.; Hadlen, D. A.; Sable, P.;
Hoff, J. M.; Martin, S. L.; Martin, S. F.; Hoff, J.
2004MPC..51593...6R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: H alpha Doppler Observations and Movies of the X-class Flares
on 2003 Nov 2 and 2003 Nov 4
Authors: Martin, S. F.
2004AAS...204.4711M Altcode: 2004BAAS...36..738M
The most energetic X-class flares on 2003 Nov. 2 and Nov. 4 were
observed at Helio Research at multiple wavelengths around the Hydrogen
alpha line. The flares were recorded in 0.5 Angstrom steps in the
range of -2 to +2 Angstroms using a tunable filter of 1 Angstrom
half-width. The tunable filter was employed in the Helio Research 25 cm
aperture telescope with a field of view limited to 10 X 10 arc min. <P
/>The flare of Nov 2 was observed entirely against the solar disk. The
images reveal the brightest parts of the extended flare. The time-lapse
movies of these images show how the bright core of the chromospheric
part of the flare spreads across each of 3 large sunspot umbrae of the
associated active region. <P />The Nov 4 flare was observed primarily as
complex system loops above limb with an occulting disk blocking most of
the solar disk. These sets of images show the development and evolution
of the flare loop system. Doppler motions in the range of - 90 to +
90 km/sec within the loops are well revealed in these time-lapse series
at 9 wavelengths shown as time-lapse movies. <P />The observations and
analyses are supported under NASA grant NAG5-10852 and are available
for correlative studies with data sets from other observatories.
---------------------------------------------------------
Title: Solar Coronal Magnetic Filaments: The Roll Effect in Erupting
Prominences
Authors: Bangert, P. D.; Martin, S. F.; Berger, M. A.
2003SPD....34.0508B Altcode: 2003BAAS...35..815B
Based on observations, we suggest that the magnetic field of a filament
(or prominence) should be treated as a ribbon. We then use the ribbon
hypothesis to explain an observable effect which we term the roll
effect. Briefly, the nature of the roll effect is manifested by a
filament ribbon in its slow pre-eruptive rise through the tendency to
be non-radial, with a small preferential roll in one direction. When it
erupts and further rises, the most elevated portion bends over in the
roll direction and is forced to become nearly horizontal. Propagation
of the roll down the legs of the filament twists them in opposite
directions as we verify in observed examples. The direction of this
rolling has a one-to-one correspondence with the combination of filament
chirality that is known to be in one-to-one correspondence with the
polarity of the photospheric magnetic field on either side of the
filament. Because the rolling can occur in only two possible forms of
handedness, they constitute an observable form of chirality specific
to erupting filaments. Establishing this bijection is the major concern
of this talk. <P />The contribution of PDB was partially supported by a
Valerie Mysercough Prize, SFM was supported by NASA grant NAG5-5917 and
MAB gratefully acknowledges funding by PPARC grant PPA/G/S/1999/00059.
---------------------------------------------------------
Title: Prominence and Filament Activity Recorded with a New, Tunable,
One-Angstrom Filter
Authors: Martin, S. F.; Martin, D. C.
2003SPD....34.2011M Altcode: 2003BAAS...35..846M
New observations using a one-Angstrom Hα tunable multi-layer
interference filter demonstrate the efficacy of this filter in detecting
key Doppler shifts in filaments and prominences both before and during
their eruption. The new filter is superior as a prefilter. However,
here we emphasize its merits as a stand-alone filter. The new filter was
constructed from 2 single-period interference filters. Used in tandem,
the two filters allow us to achieve an effective one Angstrom passband
that is tunable by mechanical tilting over a useful range of at least
6 Angstroms. Employed in a solar telescope and starting at Hα line
center, an observer can detect all filaments on the solar disk, a goal
not achievable with most other one-Angstrom filters. The observer can
then initiate manual or automated tuning of the filter to determine
whether a filament has normal, low Doppler shifts or increased Doppler
shifts signaling that it is either activated or in the early stage of
eruption. Our few initial observations reveal activations as readily
as through much more expensive, ultra-narrow passband filters of the
Fabry-Perot or birefringent type. Less visibility of chromospheric
fine structure might be considered either an asset or disadvantage
depending upon the observational goals. Minor changes in the filter
passband with wavelength are a possible downside to be weighed against
its relative low cost, minimal mass, and ruggedness which make it
practical for monitoring major solar activity in space experiments as
well as from the ground. The development and use of this filter was
possible through NASA grant NAG5-9517.
---------------------------------------------------------
Title: Signatures of Large Scale Coronal Eruptive Activity, Associated
Flares, and Propagating Chromospheric Disturbances
Authors: Balasubramaniam, K. S.; Pevtsov, A. A.; Neidig, D. F.;
Cliver, E. W.; Young, C. A.; Martin, S. F.; Kiplinger, A. L.
2003SPD....34.0505B Altcode: 2003BAAS...35..814B
Analyses of multi-wavelength data sets on 2002 December 19 at
approximately 2150 UT show evidence of a large-scale, transequatorial
coronal eruption associated with simultaneous flares in active
regions in both hemispheres. The coronal manifestations (based on
EIT, LASCO, and TRACE images) include a large coronal dimming,
an opening/restructuring of magnetic fields, the formation of a
transient coronal hole, and a halo CME. In the chromosphere, ISOON
H-alpha images show distant flare precursor brightenings and several
sympathetic flares. Originating near the main flare is a rapidly
propagating (800 km/s), narrowly channeled disturbance detectable as a
sequential brightening of numerous pre-existing points in the H-alpha
chromospheric network. This disturbance is not a chromospheric Moreton
wave, but it does produce a temporary activation of a transequatorial
filament. This filament does not erupt nor do any other filaments
in the vicinity. MDI magnetograms show that the brightened network
points are all of the same polarity (the dominant polarity among the
points in the disturbance's path), suggesting that the affected field
lines extend into the corona where they are energized in sequence
as the eruption tears away. <P />Three other similar eruptive events
(non-transequatorial) that we studied, while they are less impressive,
show most of the same phenomena including distant sympathetic flares and
a propagating disturbance showing close adherence to the monopolarity
rule. Two of these events do include filament eruptions near the main
flare. We conclude that the observations of these four events are
consistent with large scale coronal eruptive activity that triggers
nearly simultaneous surface activity of various forms separated by
distances on the same scale as the coronal structures themselves. A
filament eruption at the main flare site appears not to be a necessity
in this type of eruptive activity.
---------------------------------------------------------
Title: Signs of helicity in solar prominences and related features
Authors: Martin, Sara F.
2003AdSpR..32.1883M Altcode:
The chirality of filaments and features in their environment are
reviewed in preparation to discuss how some of the observational
signatures of chirality have been differently interpreted as
corresponding to either positive or negative helicity. Complete
agreement exists among authors that the positive and negative signs
of chirality of sigmoids and coronal arcades correspond respectively
to positive and negative signs of helicity. However, to date there has
not been a consensus on whether the observational definitions of right
and left handed signatures of the chirality of filaments and filament
channels correspond respectively to positive and negative signs of
twist helicity or to the inverse. Three proposed observational tests
are discussed on how to establish the correct associations but only
Doppler velocity measurements during erupting prominences have been
generally regarded as a definitive test. Doppler shifts in spectra and
multi-wave length sets of filtergrams of filament eruptions recorded
with at least three different instruments at different observatories
have provided data showing the largely unexpected result that
both signs of twist helicity exist in different parts of erupting
prominences. Supporting evidence of both signs of helicity in some
erupting prominences are additionally shown in 195A images from TRACE,
304A images from EIT/SOHO and vortical motions in the chromosphere
observed at NSO/Sacramento Peak Observatory. This accumulation of
evidence also reveals a general pattern of dual helicity associated
with a rolling motion in the top and twist of opposite helicity in
the legs of these erupting prominences. A force generating a rolling
motion implies no introduction of twist unless applied non-uniformly to
a non-rigid structure. If the non-rigid structure is part of a closed
magnetic field system, like a prominence, and a force is applied at its
top as inferred from the observations, both signs of twist helicity
are necessarily produced. It is suggested that such an unknown force
produces the observed "roll effect" in erupting prominences and that
the source of this initiating force needs to be identified.
---------------------------------------------------------
Title: The Skew of High-Latitude X-ray Arcades in the Declining
Phase of Cycle 22
Authors: Mc Allister, A. H.; Mackay, D. H.; Martin, S. F.
2002SoPh..211..155M Altcode:
The chirality of high-latitude coronal arcades in the declining phase
of cycle 22 has been studied. It is found that the observed skew of
the high-latitude arcades is opposite to the dominant arcade skew at
lower latitudes. This new result which applies only to the declining
phase of the solar cycle is consistent with differential rotation and
the simulations of Mackay and van Ballegooijen (2001). Limitations of
the present study are discussed along with its consequences for the
global pattern of filaments in each hemisphere. The results suggest
that, for the declining phase, the previously observed global pattern
may be more complex with latitudinal variations. Future observing
programs required to clarify the issue are discussed.
---------------------------------------------------------
Title: Solar Prominence Dynamics
Authors: Martin, S. F.
2002AAS...200.3102M Altcode: 2002BAAS...34..684M
In their most stable state, prominences are characterized by
continuous mass flows at speeds of 5-20 km/sec along every part
of their structure. In images having high spatial resolution,
prominences always consist of very fine threads. Recent Hα Doppler
observations show finely interleaved motions in opposite directions
and over long distances along these threads, a phenomenon known as
counterstreaming. This fine-scale bi-directional streaming is evidence
that the local magnetic field within prominences is everywhere parallel
with the prominence threads. At the sides of intermediate and quiescent
prominences, are groups of threads along which mass flows to and
from the chromosphere. These are known as barbs; prominence threads
and barbs reveal whether a prominence is right-handed (dextral) or
left-handed (sinistral). Counterstreaming along the barbs leads to
the conclusion that the mass of prominence is continuously supplied
from the low chromosphere or at the temperature minimum very near the
photosphere. To understand the dynamics of these continuous mass flows,
we must look to the sea of continuously interacting, small-scale bipolar
magnetic fields beneath prominences. In He II 304A images from the EIT
experiment on the SOHO satellite, the speeds along the high axis of
prominences are reported to be faster than in Hα with common speeds
in the range of 10-30 km/sec. Prominences are also a few thousand
kilometers taller and often tens of thousands of kilometers longer in
He II 304A. Prominences seen against the solar disk are often called
filaments. Many filaments exhibit activated intervals when their flows
are accelerated; at these times, they reveal additional varieties of
motion. Activations can be caused by small flares near one end of a
filament, by impact from flare waves, or by emerging magnetic regions
near the filament but they also occur for no obvious reason. Only
some activated intervals lead to eruption. NASA grants NAG5-9517 and
NAG5-10852 are gratefully acknowledged.
---------------------------------------------------------
Title: A test of real-time prediction of magnetic cloud topology
and geomagnetic storm occurrence from solar signatures
Authors: McAllister, A. H.; Martin, S. F.; Crooker, N. U.; Lepping,
R. P.; Fitzenreiter, R. J.
2001JGR...10629185M Altcode:
On the basis of the location, orientation, and surrounding magnetic
field configuration of an erupting filament observed on September
27, 1997, an Earth-encounter with a magnetic cloud having specific
topological properties and an ensuing geomagnetic storm were predicted
for September 30, assuming an average Sun-Earth transit time. A
subsequent comparison with solar wind and geomagnetic data surrounding
September 30 yielded a mixed level of success. Although a geomagnetic
storm occurred on October 1, ironically, the strong southward magnetic
field responsible for it was not encountered at the leading edge of the
cloud, as predicted, but rather in the preceding sheath. In retrospect,
the most likely sources of the southward field in the sheath were either
a preceding CME or magnetic flux from high in the corona, not draped or
turbulent flux from the ambient solar wind as is often supposed. With
the aid of a flux rope model, we show that the elevation and polarity of
the cloud axis and the chirality of the cloud were predicted correctly
but that the trajectory of the spacecraft (and Earth) through what was
deduced to be the leg of a flux rope loop precluded encounter with its
leading southward field. The storm began with a sudden commencement
near 0100 UT on October 1, corresponding to passage of a shock-like
discontinuity, and the Dst storm index reached a minimum of -108 nT
14 hours later at 1500 UT. The leading edge of the cloud, however,
coincident with the onset of counterstreaming electrons confirming its
identification, was not encountered until 1700 UT. The disagreement
between the predicted and actual arrival time reflects not only the
lack of speed prediction capabilities but also the inability to predict
whether encounter will be head-on with the apex of a flux rope loop or,
as deduced in this case, passage through one of its legs.
---------------------------------------------------------
Title: East and West Limb Erupting Events Associated with the Same
Filament Channel
Authors: Martin, S. F.
2001AGUSM..SH42A05M Altcode:
Separated by an interval of 10 days, two major filaments erupted from
the same filament channel. The first began on the disk near the east
limb; the second also began on the disk but near the west limb. Both
erupting filaments were exceptionally bright with complex helical
structure. The second filament formed at the location of the first
eruptive and within one day after the first eruptive. The orientation
of the filament channel was SW to NE extending out of NOAA active
region 9262 with an average angle of 35 degrees relative to the solar
equator. These circumstances offer the unusual opportunity to study
similar filament eruptions and their corresponding CMEs from different
viewing directions and to try to determine if the apparent structure
of the events is strongly dependent on viewing direction. The leading
front of the CME with the east limb eruptive was a faint arc in the
EIT FeXII 195A images. In the LASCO C2 field, a CME was found with the
first eruptive although it was not reported on the LASCO preliminary
CME listing; it consisted of a succession of ejecta along nearly radial
trajectories and hence did not look like most published examples of
CMEs. The CME with the west limb eruptive had the form of a classical
arch but lacked a clear cavity. Both events were also nearly concurrent
with but slightly lagging an adjacent CME. In these examples, the
large difference in the appearance of the CMEs could be due at least
in part to the difference in viewing direction. However, some of the
differences could also be due to interaction with the adjacent CMEs
at different locations. In the LASCO C3 fields of view, each of the
subject events appeared to merge with an adjacent CME into a single
larger or longer-enduring CME. The subject events are consistent with
the idea of triggering by interaction with the adjacent CMEs.
---------------------------------------------------------
Title: Small Magnetic Bipoles Emerging in a Filament Channel
Authors: Chae, Jongchul; Martin, Sara F.; Yun, H. S.; Kim, Junghoon;
Lee, Sangwoo; Goode, Philip R.; Spirock, Tom; Wang, Haimin
2001ApJ...548..497C Altcode:
Observations have shown that quiescent prominences or filaments have a
hemispheric magnetic pattern of chirality. Motivated by the question
of whether the filament chirality is of subsurface origin or not,
we have studied small magnetic bipoles that emerged in a quiescent
filament channel at latitude N45°. During our 5 day observing run,
performed in 1999 October, a huge filament erupted and reformed shortly
in the same filament channel. Using high-cadence, long-integration
line-of-sight magnetograms taken at Big Bear Solar Observatory, we
identified a total of 102 bipoles that showed an average total flux
of 2.8×10<SUP>19</SUP> Mx, an average separation of 7400 km at the
time of full development, and an emergence rate of 430 hr<SUP>-1</SUP>
per the entire solar surface area. These properties indicate that most
of the bipoles are ephemeral regions. The most important finding in
the present study is that the magnetic axes of the bipoles emerging in
the filament channel are systematically oriented; a negative (trailing)
pole is observed to be located preferentially to the south-east of its
companion positive (leading) pole. This preferred orientation does not
match either the Hale law of active region orientation or a theory that
attributes the axial field of a filament to emerging bipoles. We propose
two possible subsurface field configurations of bipoles consistent with
the observed preferential orientation and discuss physical implications
of our results for understanding filament magnetic fields.
---------------------------------------------------------
Title: The origin and development of the May 1997 magnetic cloud
Authors: Webb, D. F.; Lepping, R. P.; Burlaga, L. F.; DeForest, C. E.;
Larson, D. E.; Martin, S. F.; Plunkett, S. P.; Rust, D. M.
2000JGR...10527251W Altcode:
A complete halo coronal mass ejection (CME) was observed by the SOHO
Large-Angle and Spectrometric Coronagraph (LASCO) coronagraphs on May
12, 1997. It was associated with activity near Sun center, implying that
it was aimed earthward. Three days later on May 15 an interplanetary
shock and magnetic cloud/flux rope transient was detected at the Wind
spacecraft 190 R<SUB>E</SUB> upstream of Earth. The long enduring
southward magnetic fields associated with these structures triggered a
geomagnetic storm. The CME was associated with a small coronal arcade
that formed over a filament eruption with expanding double ribbons
in Hα emission. The flare was accompanied by a circular EUV wave,
and the arcade was flanked by adjacent dimming regions. We surmise
that these latter regions marked the feet of a flux rope that expanded
earthward into the solar wind and was observed as the magnetic cloud
at Wind. To test this hypothesis we determined key parameters of the
solar structures on May 12 and compared them with the modeled flux
rope parameters at Wind on May 15. The measurements are consistent
with the flux rope originating in a large coronal structure linked
to the erupting filament, with the opposite-polarity feet of the rope
terminating in the depleted regions. However, bidirectional electron
streaming was not observed within the cloud itself, suggesting that
there is not always a good correspondence between such flows and ejecta.
---------------------------------------------------------
Title: Model Prediction for an Observed Filament
Authors: Aulanier, G.; Srivastava, N.; Martin, S. F.
2000ApJ...543..447A Altcode:
This paper presents the results of a “blind test” for modeling
the structure of an observed filament using the three-dimensional
magnetohydrostatic model recently developed by Aulanier et al. in
1999. The model uses a constant shear α, and it takes into account the
effects of pressure and gravity. The test consisted of predicting the
structure of a filament (observed in the southern hemisphere) with
a minimum observational input: only a line-of-sight magnetogram,
with a straight line drawn on it to show the location of the
filament, was provided. The filament was chosen by the observers
(N. S. and S. F. M.) because it had a definite overall left-handed
structural pattern known as sinistral, but the direction of component
of the magnetic field along the filament axis was uncertain from the
combination of Hα data and magnetograms. The modeler (G. A.) evaluated
and fixed the values of some of the free parameters of the model
while some others were varied in reasonable ranges. The Hα image
of the filament was revealed only after the modeling. For α>0,
the three-dimensional distribution of magnetic dips computed by the
model fairly well reproduces the structure of the filament and its
barbs. Moreover, the models for which α<0 do not match well the
observations. This study then shows the first successful theoretical
prediction for the magnetic field of an observed filament. It shows
that the method based on the Aulanier et al. model is a powerful tool,
not only for purposes of modeling, but also for prediction of the
chirality, helicity, and morphology of observed filaments.
---------------------------------------------------------
Title: Orientation of Emerging Bipoles in a Filament Channel
Authors: Chae, J.; Goode, P. R.; Spirock, T. J.; Wang, H.; Martin,
S. F.; Yun, H. S.; Kim, Jung-Hoon; Lee, Sangwoo
2000SPD....31.0405C Altcode: 2000BAAS...32R.835C
Observations have shown that quiescent prominences or filaments have
a hemispheric magnetic pattern of chirality or handedness. Motivated
by the question of whether the filament chirality is of sub-surface
origin or not, we have studied magnetic bipoles emerging in a quiescent
filament channel at latitude N45° . During our 5 day observing run
performed in 1999 October, a huge filament erupted and another began to
form in the same filament channel. Using high cadence deep line-of-sight
magnetograms, we identified a total of 102 small emerging bipoles,
which display the following statistical properties: 1) an average flux
of 1.2x 10<SUP>19</SUP> Mx and an average separation of 7200 km; 2) an
inferred global emergence frequency of 600 hr<SUP>-1</SUP> all over the
solar surface; and 3) a preferred orientation that a negative (trailing)
pole is located at the south-east of the companion positive (leading)
pole. The majority of the bipoles appear to be ephemeral regions which
are systematically smaller than those previously studied with Kitt
Peak full disk daily magnetograms. The preferred orientation of these
bipoles differs greatly from both the filament axial field direction
and the active region polarity law. We conclude that factors other than
the Hale polarity law are the cause of asymmetry in the orientation of
small bipoles having total magnetic fluxes below 2 x 10<SUP>19</SUP> Mx.
---------------------------------------------------------
Title: Factors Related to the Origin of a Gradual Coronal Mass
Ejection Associated with an Eruptive Prominence on 1998 June 21-22
Authors: Srivastava, Nandita; Schwenn, Rainer; Inhester, Bernd;
Martin, Sara F.; Hanaoka, Yoichiro
2000ApJ...534..468S Altcode:
We present observations of a coronal mass ejection (CME) associated
with an eruptive prominence during 1998 June 21-22 by LASCO (Large
Angle Spectroscopic Coronagraph) aboard SOHO (Solar and Heliospheric
Observatory). Various features in the three-part structured, white-light
CME as observed by LASCO-C2 and C3 coronagraphs were compared with
features in the other wavelengths, for example, in Fe XIV and Fe X
emission lines obtained from LASCO C1, in Hα from Helio-Research and
at 17 GHz obtained from Nobeyama Radioheliograph. We have investigated
conditions in several data sets to understand the eruptive and the
pre-eruptive scenario of the CME. The CME and the eruptive prominence
accelerate up to ~20 R<SUB>solar</SUB> and then decelerate to the
velocity of the ambient slow solar wind. The analysis clearly shows
that this particular CME is a typical case of a very slow or gradual
CME for which it is difficult to define an exact onset time. The CME
could be tracked for about 30 hours until it crossed a distance of
30 R<SUB>solar</SUB> and disappeared from the field of view of the
LASCO-C3 coronagraph. The height-time profiles of various features of
this CME suggest that the leading edge of the CME and the top of the
prominence or the core follow similar pattern, implying a common driver
for both the CME and the eruptive prominence. The observations provide
strong evidence that the CME and the prominence eruption resulted from
a common cause which is the global restructuring of the magnetic field
in the corona in an extensive volume of space near and including the
CME. The restructuring in turn was a consequence of newly emerging
flux regions near and within the neighboring active regions close to
the base of the CME.
---------------------------------------------------------
Title: Observations of the 24 September 1997 Coronal Flare Waves
Authors: Thompson, B. J.; Reynolds, B.; Aurass, H.; Gopalswamy, N.;
Gurman, J. B.; Hudson, H. S.; Martin, S. F.; St. Cyr, O. C.
2000SoPh..193..161T Altcode:
We report coincident observations of coronal and chromospheric `flare
wave' transients in association with a flare, large-scale coronal
dimming, metric radio activity and a coronal mass ejection. The two
separate eruptions occurring on 24 September 1997 originate in the
same active region and display similar morphological features. The
first wave transient was observed in EUV and Hα data, corresponding
to a wave disturbance in both the chromosphere and the solar corona,
ranging from 250 to approaching 1000 km s<SUP>−1</SUP> at different
times and locations along the wavefront. The sharp wavefront had a
similar extent and location in both the EUV and Hα data. The data did
not show clear evidence of a driver, however. Both events display a
coronal EUV dimming which is typically used as an indicator of a coronal
mass ejection in the inner corona. White-light coronagraph observations
indicate that the first event was accompanied by an observable coronal
mass ejection while the second event did not have clear evidence of a
CME. Both eruptions were accompanied by metric type II radio bursts
propagating at speeds in the range of 500-750 km s<SUP>−1</SUP>,
and neither had accompanying interplanetary type II activity. The
timing and location of the flare waves appear to indicate an origin
with the flaring region, but several signatures associated with coronal
mass ejections indicate that the development of the CME may occur in
concert with the development of the flare wave.
---------------------------------------------------------
Title: Minifilament Eruption on the Quiet Sun. I. Observations at
Hα Central Line
Authors: Wang, Jingxiu; Li, Wei; Denker, Carsten; Lee, Chikyin; Wang,
Haimin; Goode, Philip R.; McAllister, Alan; Martin, Sara F.
2000ApJ...530.1071W Altcode:
The eruption of miniature filaments on the quiet Sun has been analyzed
from time sequences of digital Hα filtergrams obtained at Big Bear
Solar Observatory during 1997 September 18-24. The 2 days with the
best image quality were selected for this initial study. During
13 hr of time-lapse observations on these 2 days, in an effective
640<SUP>”</SUP>x480<SUP>”</SUP> area of quiet Sun close to the disk
center, 88 erupting miniature filaments were identified. On average,
these small-scale erupting filaments have a projected length of 19,000
km, an observed ejection speed of 13 km s<SUP>-1</SUP>, and a mean
lifetime of 50 minutes from first appearance through eruption. The
total mass and kinetic energy involved in a miniature filament
eruption is estimated to be 10<SUP>13</SUP> g and 10<SUP>25</SUP>
ergs, respectively. They are distinguished from macrospicules by the
same criteria that large-scale filaments, before and during eruption,
are distinguished from surges. Prior to eruption, one end, both ends,
or the midsection of a miniature filament is superposed over a polarity
reversal boundary on line-of-sight magnetograms. We conclude that
miniature filaments are the small-scale analog to large-scale filaments.
---------------------------------------------------------
Title: The Essential Role of Magnetic Reconnection in Erupting
Prominences and CMEs
Authors: McAllister, H.; Martin, S. F.
2000AdSpR..26..469M Altcode:
Reconnection has been invoked by various researchers in the different
steps of filament formation, evolution, and eruption, but it has been
hard to obtain conclusive observational evidence. The association of
magnetic clouds with the CMEs over erupting filaments has been suggested
as being the result of reconnection behind the CMEs as they leave
the Sun. In previous work we have shown that magnetic cloud topology
can be predicted from the pre-eruption filament and post-eruption
coronal arcade structure if reconnection is assumed to be involved
in the eruption process. In this paper we outline the stages in the
eruption process, indicating how reconnection can play a role. The
case of the eruption on September 27, 1997, in which the topological
properties of a magnetic cloud were successfully predicted from the
solar observations, illustrates the fact that reconnection plays an
important part in the life of prominences and CMEs, as well as in flares
---------------------------------------------------------
Title: Simultaneous Hα and X-ray Observations of Prominence Eruption
and Disappearance
Authors: Tonooka, H.; Matsumoto, R.; Miyaji, S.; Martin, S. F.;
Canfield, R. C.; Reardon, K.; McAllister, A.; Shibata, K.
2000AdSpR..26..473T Altcode:
Prominence eruptions or disappearances observed with an Hα limb
filtergraph can be classified into 3 categories, the eruptive
prominence, the quasi-eruptive prominence, and the disappearing
prominence. We investigated their mechanism by comparing the results
of simultaneous observations by Yohkoh SXT and Hα. We found that soft
X-ray features change in both eruptive prominences and quasieruptive
prominences, whereas no significant change takes place in disappearing
prominences.In one prominence eruption event soft X-ray cusp structure
suggests that the reconnection point is just below the Hα prominence
---------------------------------------------------------
Title: Magnetic reconnection as the cause of a photospheric canceling
feature and mass flows in a filament
Authors: Litvinenko, Yuri E.; Martin, Sara F.
1999SoPh..190...45L Altcode:
Magnetic reconnection in the temperature minimum region of the
solar photosphere can account for the canceling magnetic features
on the Sun. Litvinenko (1999a) showed that a reconnection model
explains the quiet-Sun features with the magnetic flux cancelation
rate of order 10<SUP>17</SUP> Mx hr<SUP>−1</SUP>. In this paper
the model is applied to cancelation in solar active regions,
which is characterized by a much larger rate of cancelation ∖
ge10<SUP>19</SUP> Mx hr<SUP>−1</SUP>. In particular, the evolution
of a photospheric canceling feature observed in an active region on
July 2, 1994 is studied. The theoretical predictions are demonstrated
to be in reasonable agreement with the measured speed of approaching
magnetic fragments, the magnetic field in the fragments, and the flux
cancelation rate, deduced from the combined Big Bear Hα time-lapse
images and videomagnetograms calibrated against the daily NSO/Kitt
Peak magnetogram. Of particular interest is the prediction that
photospheric reconnection should lead to a significant upward mass
flux and the formation of a solar filament. Hα observations indeed
showed a filament that had one of its ends spatially superposed with
the canceling feature.
---------------------------------------------------------
Title: Counter-streaming gas flows in solar prominences as evidence
for vertical magnetic fields
Authors: Zirker, J. B.; Engvold, O.; Martin, S. F.
1998Natur.396..440Z Altcode:
Solar prominences are sheets of relatively cool and dense gas embedded
in the surrounding hotter corona. An erupting prominence can inject a
mass of up to 10<SUP>15</SUP>g into the solar wind as part of a coronal
mass ejection. These eruptions must depend critically on the topology of
the prominence's magnetic field. In all present models,, the prominence
hangs on horizontal or helical field lines, while an overlying magnetic
arcade temporarily restrains the prominence from erupting. Such models
are inconsistent, however, with the slow upward vertical gas flows that
are seen in prominences. Here we report counter-streaming flows along
closely spaced vertical regions of a prominence, between its top and the
lower solar atmosphere. As the flows must be aligned with the magnetic
field, this observation implies that a field connects the prominence
directly to the photosphere, contrary to all existing models. These
magnetic `tethers' might help prevent a prominence from erupting.
---------------------------------------------------------
Title: Conditions for the Formation and Maintenance of Filaments
(Invited Review)
Authors: Martin, Sara F.
1998SoPh..182..107M Altcode:
Observational conditions for the formation and maintenance of filaments
are reviewed since 1989 in the light of recent findings on their
structure, chirality, inferred magnetic topology, and mass flows. Recent
observations confirm the necessary conditions previously cited: (1)
their location at a boundary between opposite-polarity magnetic fields
(2) a system of overlying coronal loops, (3) a magnetically-defined
channel beneath, (4) the convergence of the opposite-polarity network
magnetic fields towards their common boundary within the channel and (5)
cancellation of magnetic flux at the common polarity boundary. Evidence
is put forth for three additional conditions associated with fully
developed filaments: (A) field-aligned mass flows parallel with their
fine structure (B) a multi-polar background source of small-scale
magnetic fields necessary for the formation of the filament barbs and
(C) a handedness property known as chirality which requires them to be
either of two types, dextral or sinistral. One-to-one relationships have
been established between the chirality of filaments and the chirality of
their filament channels and overlying coronal arcades. These findings
reinforce earlier evidence that every filament magnetic field is
separate from the magnetic field of the overlying arcade but both
are parts of a larger magnetic field system. The larger system has
at least quadrupolar footprints in the photosphere and includes the
filament channel and subphotospheric magnetic fields, This `systems'
view of filaments and their environment enables new perspectives on
why arcades and channels are invariable conditions for their existence.
---------------------------------------------------------
Title: Soft X-Ray Features of Prominence Eruption and Disappearance
Authors: Tonooka, H.; Matsumoto, R.; Miyaji, S.; Martin, S. F.;
Canfield, R. C.; Reardon, K.; McAllister, A.; Shibata, K.
1998ASSL..229..371T Altcode: 1998opaf.conf..371T
No abstract at ADS
---------------------------------------------------------
Title: Filament Chirality: A Link Between Fine-Scale and Global
Patterns (Review)
Authors: Martin, S. F.
1998ASPC..150..419M Altcode: 1998IAUCo.167..419M; 1998npsp.conf..419M
No abstract at ADS
---------------------------------------------------------
Title: Plasma Streaming as Indicator of Field Topology in a Quiescent
Filament
Authors: Zirker, J. B.; Engvold, O.; Martin, S. F.
1997AAS...19112004Z Altcode: 1997BAAS...29.1402Z
Although it is generally accepted that quiescent filaments have strong
horizontal axial magnetic field (Leroy,1984) the field configuration in
the legs (“barbs” or “feet”) is controversial. Previous observations
indicate both rising and falling Doppler motions in such appendages,
at speeds less than “free-fall” (Dunn,1960; Yi et al,1991; Zirker
et al, 1994). Such observations could be consistent with the presence
of horizontal magnetic fields that are slowly drifting up and down
carrying plasma with them. However the H alpha fine-structure strongly
suggests the presence of vertical or highly inclined magnetic field
lines. Without vector field observations it is difficult to choose
between these alternatives. In an attempt to clarify the issue,
H alpha observations of a quiescent filament were made during its
passage across the disk, from 12 to 20 April, 1993 at the Big Bear
Observatory. Remarkable high-speed flows (of order 20 km/s ) were
seen along the axial "spine" of the filament. Substantially slower
motions were detected in the barbs. The paradox of non-free-fall
motions in the predominantly vertically directed threads of barbs,
will be discussed briefly. Bommier,V., Landi Degli'Innocenti,E.,
Leroy, J-L., and Sahal-Brechot, S.: 1994, Solar Phys. 154,231 Dunn,
R.B.,1960, Ph D Thesis, Harvard University Engvold,O.: 1976,Solar
Phys.49,283. Leroy,J-L. Bommier,V. nd Sahal Brechot,S.:1984, Astronomy
and Astrophysics, 131,33. Yi,Z.,Engvold,O. and Keil,S.L.: 1991, Solar
Phys. 132,63. Zirker,J.B.,Engvold,O.and Yi,Z. 1994, Solar Phys. 150,81.
---------------------------------------------------------
Title: Global Magnetic Patterns of Chirality
Authors: Zirker, J. B.; Martin, S. F.; Harvey, K.; Gaizauskas, V.
1997SoPh..175...27Z Altcode:
During the past five years at least six manifestations of a global
organization of solar magnetic fields have been recognized. The magnetic
chirality (handedness) of the following features shows a hemispheric
preference: filament channels, quiescent filaments, sunspot whorls,
superpenumbral fibrils, coronal arcades, and interplanetary clouds
associated with CMEs. Although the patterns are clear in the data,
their interpretation and their possible connection to the dynamo is
open to question. This paper reviews the observations of the patterns,
corrects some misinterpretations, and offers a scenario for the origin
of the most marked pattern, the chirality of filaments. We suggest
the pattern arises from the reconnection of coronal loops, under
the influence of supergranulation and differential rotation. Unlike
alternative scenarios, ours relies only on observable surface motions
and fields.
---------------------------------------------------------
Title: A Conceptual Model of the Formation of Filament Barbs
Authors: Martin, S. F.
1997SPD....28.1706M Altcode: 1997BAAS...29..921M
Barbs are the structures along the sides of a filament that connect
its horizontal axis to chromosphere. The barbs, previously called
'legs' can be considered as magnetic field conduits along which mass
is continuously guided and transported to and from the chromosphere. In
the model presented, the barbs represent a secondary stage in filament
formation which follows an intial stage in which a nearly horizontal
axial magnetic field is first formed along a filament channel. Barb
formation is most effectively and readily illustrated where the
filament channel is broad and well-developed such as exists among the
decaying network remnants of active regions. In these circumstances,
the filament channel is a region of relatively low magnetic flux density
compared to adjacent areas further from the polarity inversion. H-alpha
filtergrams show that the axial parts of the filament are low and
nearly contiguous with the chromosphere. The low height of the axial
field, and the relative absence of concentrations of network magnetic
field, are favorable conditions for magnetic reconnection between the
axial field of the filament and new ephemeral regions and intranetwork
magnetic fields beneath the filament. These reconnections lead to the
formation of the barbs joining parts of the newly emerged fields to the
axial field of the filament. Barb formation and motions seen in H-alpha
filtergrams provide the evidence for this initial part of the conceptual
model. The remaining part of the model is a demonstration of why only
right-bearing barbs are seen on dextral filaments and left-bearing
barbs on sinistral filaments; this is due to the sinistral or dextral
magnetic configuration of the filament channel which does not permit the
survival of barbs of the non-observed chirality as will be illustrated.
---------------------------------------------------------
Title: Filament disturbance and associated magnetic changes in the
filament environment.
Authors: Wang, J.; Shi, Z.; Martin, S. F.
1996A&A...316..201W Altcode:
The morphology and velocity patterns of a disturbing filament in an
active region, and the evolution of its surrounding magnetic fields are
described in this paper. The disturbance is characterized by vigorous
loosening rotation and upward motion. It starts at sites of new
emerging flux and cancelling magnetic features beneath the filament,
and where microflares take place. In the filament environment, two
small emerging flux regions and seven cancelling magnetic features are
identified. Major disturbance is associated with flux cancellation
at several sites, underlying the central part of the filament. We
suggest that the surrounding magnetic fields of the filament and the
magnetic fields in the filament have been partly reconnected at the
photospheric level. This results in a complicated magnetic topology,
and appears to be the cause of the filament activation.
---------------------------------------------------------
Title: YOHKOH SXT Observations of Prominence Eruption and
Disappearance
Authors: Tonooka, H.; Matsumoto, R.; Miyaji, S.; Martin, S. F.;
Canfield, R. C.; Reardon, K.; McAllister, A.; Shibata, K.
1996mpsa.conf..493T Altcode: 1996IAUCo.153..493T
No abstract at ADS
---------------------------------------------------------
Title: The Skew of X-ray Coronal Loops Overlying H alpha Filaments
Authors: Martin, S. F.; McAllister, A. H.
1996mpsa.conf..497M Altcode: 1996IAUCo.153..497M
No abstract at ADS
---------------------------------------------------------
Title: The initiation of coronal mass ejections by newly emerging
magnetic flux
Authors: Feynman, J.; Martin, S. F.
1995JGR...100.3355F Altcode:
We present observational evidence that eruptions of quiescent filaments
and associated coronal mass ejections (CMEs) occur as a consequence of
the destabilization of large-scale coronal arcades due to interactions
between these structures and new and growing active regions. Both
statistical and case studies have been carried out. In a case study
of a “bugle” observed by the High-Altitude Observatory Solar Maximum
Mission coronagraph, the high-resolution magnetograms from the Big Bear
Solar Observatory show newly emerging and rapidly changing flux in the
magnetic fields that apparently underlie the bulge. For other case
studies and in the statistical work the eruption of major quiescent
filaments was taken as a proxy for CME eruption. We have found that
two thirds of the quiescent-filament-associated CMEs occurred after
substantial amounts of new magnetic flux emerged in the vicinity of
the filament. In addition, in a study of all major quiescent filaments
and active regions appearing in a 2-month period we found that 17 of
the 22 filaments that were associated with new active regions erupted
and 26 of the 31 filaments that were not associated with new flux did
not erupt. In all cases in which the new flux was oriented favorably
for reconnection with the preexisting large-scale coronal arcades;
the filament was observed to erupt. The appearance of the new flux in
the form of new active regions begins a few days before the eruption
and typically is still occurring at the time of the eruption. A CME
initiation scenario taking account of these observational results
is proposed.
---------------------------------------------------------
Title: The Skew of X-Ray Coronal Loops Overlying Hα Filaments
Authors: Martin, S. F.; McAllister, A. H.
1995SPD....26..603M Altcode: 1995BAAS...27R.961M
No abstract at ADS
---------------------------------------------------------
Title: Footpoints of Solar Filaments
Authors: Martin, Sara F.
1994AAS...18512303M Altcode: 1994BAAS...26.1522M
Quiescent filaments are characterized in part by appendages
or `barbs' along each side of the long axis or `spine' of the
filament. Observations of the barbs at the limb and against the disk
show that the barbs are paths along which mass flows from the spine to
the chromosphere or vice-versa. The barbs and their chromospheric and
photospheric footpoints were studied using Hα filtergrams of a filament
and corresponding photospheric line-of-sight magnetograms revealing
enhanced network magnetic fields adjacent to the filament. These
data were acquired from 13 thru 17 May 1992 at the Big Bear Solar
Observatory. The footpoints of the major barbs were found to coincide
with patches of minority polarity among the photospheric magnetic
fields on each side of the filament. The minority polarity consists
of small patches of magnetic field opposite in polarity to the areas
of dominant unipolar network magnetic field on the same side of the
filament. This finding is consistent with the magnetic field in the
barbs being `inverse', that is, the reverse of the direction of the
component of the magnetic field of the coronal arcade high above and
perpendicular to the spine of the filament.
---------------------------------------------------------
Title: Preflare State
Authors: Rust, David M.; Sakurai, Takashi; Gaizauskas, Victor; Hofmann,
Axel; Martin, Sara F.; Priest, Eric R.; Wang, Jing-Xiu
1994SoPh..153....1R Altcode:
Discussion on the preflare state held at the Ottawa Flares 22
Workshop focused on the interpretation of solar magnetograms and
of Hα filament activity. Magnetograms from several observatories
provided evidence of significant build up of electric currents in
flaring regions. Images of X-ray emitting structures provided a clear
example of magnetic relaxation in the course of a flare. Emerging
and cancelling magnetic fields appear to be important for triggering
flares and for the formation of filaments, which are associated with
eruptive flares. Filaments may become unstable by the build up of
electric current helicity. Examples of heliform eruptive filaments
were presented at the Workshop. Theoretical models linking filaments
and flares are briefly reviewed.
---------------------------------------------------------
Title: Material Ejection
Authors: Webb, David F.; Forbes, Terry G.; Aurass, Henry; Chen, James;
Martens, Piet; Rompolt, Bogdan; Rusin, Vojtech; Martin, Sara F.
1994SoPh..153...73W Altcode:
This paper reviews the major discussions and conclusions of the Flares
22 Workshop concerning the physical processes involved in mass ejecta
events, with an emphasis on large-scale phenomena, especially Coronal
Mass Ejections (CMEs). New insights have been gained from recent
data obtained from the SMM andYohkoh spacecraft and from several new
ground-based radio and optical instruments, as well as from theoretical
advances concerning the origins, driving mechanisms and long-term
evolution of CMEs.
---------------------------------------------------------
Title: Solar Fine-Scale Structures in the Corona, Transition Region,
and Lower Atmosphere
Authors: Moses, Dan; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.;
Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Recely, F.;
Martin, S. F.; Zirin, H.
1994ApJ...430..913M Altcode:
The American Science and Engineering Soft X-ray Imaging Payload and the
Naval Research Laboratory High Resolution Telescope and Spectrograph
(HRTS) were launched from White Sands on 1987 December 11 in coordinated
sounding rocket flights. The goal was to investigate the correspondence
of fine-scale structures from different temperature regimes in the
solar atmosphere, and particularly the relationship between X-ray bright
points (XBPs) and transition region explosive events. We present results
of the analysis of co-aligned X-ray images, maps of sites of transition
region explosive events observed in C IV 10<SUP>5</SUP>, HRTS 1600
A spectroheliograms of the T<SUB>min</SUB> region, and ground-based
magnetogram and He I 10830 A images. We examined the relationship
of He I 10830 A dark features and evolving magnetic features which
correspond to XBPs. We note a frequent double ribbon pattern of the
He I dark feature counterparts to XBPs. We discuss an analysis of the
relationship of XBPs to evolving magnetic features by Webb et al.,
which shows that converging magnetic features of opposite polarity are
the most significant magnetic field counterparts to XBPs. The magnetic
bipolar features associated with XBPs appear as prominent network
elements in chromospheric and transition region images. The features
in C IV observations corresponding to XBP sites are in general bright,
larger scale (approximately 10 arcsec) regions of complex velocity
fields of order 40 km/s, which is typical of brighter C IV network
elements. These C IV features do not reach the approximately 100 km/s
velocities seen in the C IV explosive events. Also, there are many
similar C IV bright network features without a corresponding XBP in the
X-ray image. The transition region explosive events do not correspond
directly to XBPs. The explosive events appear to be concentrated in
the quiet Sun at the edges of strong network, or within weaker field
strength network regions. We find a greater number of C IV events than
expected from the results of a previous Spacelab 2 HRTS disk survey. We
attribute this at least partly to better spatial resolution with the
newer HRTS data. The full-disk X-ray image shows a pattern of dark
lanes in quiet Sun areas. The number density of C IV events is twice
as large inside as outside a dark lane (4.6 x 10<SUP>-3</SUP> vs. 2.3
x 10<SUP>-3</SUP> explosive events per arcsec <SUP>2</SUP>). The dark
lane corresponds to an old decaying magnetic neutral line. We suggest
that this provides an increased opportunity for small-scale convergence
and reconnection of opposite polarity magnetic field features, in
analogy with the results of Webb et al. for XBPs but at a reduced
scale of reconnection.
---------------------------------------------------------
Title: HRTS Observations of Explosive Events in a Flaring Active
Region
Authors: Dere, K. P.; Martin, S. F.
1994kofu.symp..289D Altcode:
Explosive events are a highly dynamic, small-scale phenomena that are
commonly observed on the Sun with the NRL High Resolution Telescope and
Spectrograph (HRTS). There is now considerable evidence which suggests
that they are signatures of magnetic reconnection during flux emergence
and cancellation. Data from the Big Bear Solar Observatory and the
HRTS instrument are used to demonstrate the direct correspondence
between explosive events and evolving magnetic structures.
---------------------------------------------------------
Title: A Converging Flux Model of an X-Ray Bright Point and an
Associated Canceling Magnetic Feature
Authors: Priest, E. R.; Parnell, C. E.; Martin, S. F.
1994ApJ...427..459P Altcode:
X-ray bright points are an important part of the solar corona and
therefore of the coronal heating problem. When it was first realized
that bright points are always situated above opposite polarity
magnetic fragments in the photosphere, it was natural to suggest
that such fragments represent emerging flux and that an X-ray
bright point is caused by reconnection of the emerging flux with
an overlying coronal magnetic field. However, a recent important
discovery at the Big Bear Solar Observatory is that the magnetic
fragments of opposite polarity are usually not emerging but are
instead coming together and disappearing and so are referred to as
canceling magnetic features. Sometimes a tiny filament is observed
to form and erupt at the same time. A unified model is here proposed
which explains these observational features and has several phases:
(1) a preinteraction phase, in which two photospheric fragments are
unconnected magnetically and begin to approach one another, until
eventually oppositely directed fields from the fragments come into
contact at a second-order null point; (2) an interaction phase, in which
the null point becomes an X-point and rises into the corona; an X-ray
bright point is created for typically 8 hr by coronal reconnection,
driven by the continued approach of the photospheric sources; long
hot loops and Yohkoh X-ray jets may be created by the reconnection,
and rapid variability in bright point emission may be produced by
an impulsive burst regime of reconnection; the explosive events
seen with High Resolution Telescope and Spectrograph (HRTS) may be
produced as the X-point passes through the upper chromosphere; (3) a
cancellation phase, in which a canceling magnetic feature is produced
by photospheric reconnection as the fragments come into contact and
decrease in strength; above the canceling fragments a small filament
may form and erupt over typically an hour. An important role is played
by the interaction distance (d), which is proportional to the magnetic
flux of the fragments and inversely proportional to the overlying
magnetic field strength. It determines the fragment separation at
which the interaction phase begins and the resulting maximum height
of the reconnection point. It is suggested that coronal reconnection
driven by footpoint motion represents an elementary heating event
that may be heating normal coronal loops and may be at the root of
the nanoflare/microflare process. Bright points may well be at the
large-scale end of a broad spectrum of events of the type modeled in
this paper, which are heating the solar corona. At very small scales,
such events in 'furnaces' in the coronal hole network may even produce
high-frequency waves that propagate out and drive the solar wind
(Axford 1993).
---------------------------------------------------------
Title: Large-scale velocity fields and small-scale magnetic fields
during the maximum of solar cycle 22
Authors: Martin, Sara F.; Harvey, K. L.
1994cait.reptQ....M Altcode:
Studies of the solar cycle have revealed that the size distribution
of active regions does not vary with the solar cycle. Size, rate of
rise, and lifetime of active regions are roughly proportional although
a wide range of variation exists among these parameters. The polar
field typically reverses about 2 years after solar maximum. The new
solar cycle does not seem to start until after the reversal of the
sign of the magnetic poles. However, the new solar cycle does overlap
appreciably with the previous cycle and begins 3 or more years prior
to the minimum in sunspot producing active regions. The solar cycle
begins with ephemeral regions at high latitudes. From the analysis of
active region and ephemeral region data over more than a whole solar
cycle it is concluded that ephemeral regions are in all respects the
small-scale end of the distribution of active regions. No rationale
was found for excluding ephemeral regions as one of the effects of the
solar dynamo. The search for the early ephemeral regions associated
with solar cycle 23 at high latitudes yielded the tentative conclusion
that it was detected during our observing runs during the spring of
1993 although confirming data is needed.
---------------------------------------------------------
Title: An observational and conceptual model of the magnetic field
of a filament
Authors: Martin, S. F.; Echols, Ch. R.
1994ASIC..433..339M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Correlation Between Sunspot Whirls and Filament Type
Authors: Rust, D. M.; Martin, S. F.
1994ASPC...68..337R Altcode: 1994sare.conf..337R
No abstract at ADS
---------------------------------------------------------
Title: Magnetic field configurations basic to filament channels
and filaments
Authors: Martin, S. F.; Bilimoria, R.; Tracadas, P. W.
1994ASIC..433..303M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observational Criteria for Filament Models
Authors: Martin, Sara F.
1994ASPC...68..264M Altcode: 1994sare.conf..264M
No abstract at ADS
---------------------------------------------------------
Title: Transition Region Explosive Events in an X-Ray Dark Lane
Region of the Quiet Sun
Authors: Cook, J. W.; Moses, D.; Brueckner, G. E.; Dere, K. P.;
Bartoe, J. -D. F.; Webb, D.; Davis, J. M.; Harvey, J. W.; Recely,
F.; Martin, S. F.; Zirin, H.
1993BAAS...25.1181C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Field Configurations Basic to Filament Channels
and Filaments
Authors: Martin, S. F.; Bilimoria, R.; Tracadas, P. W.
1993BAAS...25.1217M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Initiation of Coronal Mass Ejections
Authors: Feynman, J.; Martin, S. F.
1993BAAS...25.1203F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Correspondence Between X-Ray Bright Points and Evolving
Magnetic Features in the Quiet Sun
Authors: Webb, D. F.; Martin, S. F.; Moses, D.; Harvey, J. W.
1993SoPh..144...15W Altcode:
Coronal bright points, first identified as X-ray Bright Points (XBPs),
are compact, short-lived and associated with small-scale, opposite
polarity magnetic flux features. Previous studies have yielded
contradictory results suggesting that XBPs are either primarily a
signature of emerging flux in the quiet Sun, or of the disappearance
of pre-existing flux. With the goal of improving our understanding of
the evolution of the quiet Sun magnetic field, we present results of
a study of more recent data on XBPs and small-scale evolving magnetic
structures. The coordinated data set consists of X-ray images obtained
during rocket flights on 15 August and 11 December, 1987, full-disk
magnetograms obtained at the National Solar Observatory - Kitt Peak,
and time-lapse magnetograms of multiple fields obtained at Big Bear
Solar Observatory. We find that XBPs were more frequently associated
with pre-existing magnetic features of opposite polarity which appeared
to be cancelling than with emerging or new flux regions. Most young,
emerging regions were not associated with XBPs. However, some XBPs
were associated with older ephemeral regions, some of which were
cancelling with existing network or intranetwork poles. Nearly all of
the XBPs corresponded to opposite polarity magnetic features which
wereconverging towards each other; some of these had not yet begun
cancelling. We suggest that most XBPs form when converging flow brings
oppositely directed field lines together, leading to reconnection and
heating of the newly-formed loops in the low corona.
---------------------------------------------------------
Title: Large-scale velocity fields and small-scale magnetic fields
during the maximum of solar cycle 22
Authors: Martin, Sara F.; Harvey, K. L.
1992cait.rept.....M Altcode:
One key accomplishment from the research during FY 1991 was the finding
by K. Harvey and P. Foukal that the photospheric network is the third
significant component that accounts for observed variations in the
total solar irradiance (the first previously recognized component is
the temporary decreases due to sunspots and the second is variation
due to plage brightness). Other key accomplishments were the K. Harvey
results from studying magnetic flux over the solar cycle: (1) increases
in the total magnetic flux by a factor of 4 to 5 from solar minimum to
solar maximum with the variation from active regions flux (greater than
25 Gauss) by more than a factor of 20 from cycle minimum to maximum
while the variation from quiet sun fields (less than 25 Gauss) was
no more than a factor of 2; (2) interpretation of (1) as meaning that
more than 70 percent of the magnetic flux in active regions disappears
without dispersing; (3) slower decreases of weak fields in phase with
the decrease in strong fields; and (4) irregular pulses of new flux
which appear to be primarily associated with active region complexes.
---------------------------------------------------------
Title: Ultraviolet Explosive Events and Evolving Magnetic Fields
Authors: Dere, K. P.; Martin, S. F.
1992AAS...180.5604D Altcode: 1992BAAS...24..821D
No abstract at ADS
---------------------------------------------------------
Title: An Observational Conceptual Model of the Formation of Filaments
Authors: Martin, S. F.
1992LNP...399..331M Altcode: 1992esf..coll..331M; 1992IAUCo.133..331M
No abstract at ADS
---------------------------------------------------------
Title: The Solar Cycle Pattern in the Direction of the Magnetic
Field along the Long Axes of Polar Filaments
Authors: Martin, Sara F.; Marquette, William H.; Bilimoria, Rajash
1992ASPC...27...53M Altcode: 1992socy.work...53M
No abstract at ADS
---------------------------------------------------------
Title: The Role of Cancelling Magnetic Fields in the Buildup to
Erupting Filaments and Flares
Authors: Martin, S. F.; Livi, S. H. B.
1992LNP...399...33M Altcode: 1992IAUCo.133...33M; 1992esf..coll...33M
We present a scenario for understanding the role of cancelling
magnetic fields in the build-up to eruptive solar flares. The key
intermediate step in this scenario involves the formation of a filament
magnetic field in the corona above a photospheric polarity inversion
where cancelling magnetic fields are observed. The formation of a
filament magnetic field is accomplished in several recent models
by first interpreting the cancelling fields as a visible effect of
a slow, steady magnetic reconnection. This reconnection results
in a reconfiguring of the magnetic field; line-of-sight pairs of
closely-spaced opposite-polarity fields disappear from the photosphere
thereby accounting for the cancellation; simultaneously the horizontal
component is increased in the corona above the polarity inversion. The
new and increasing horizontal component is synonymous with the building
of a magnetic field where mass can accumulate to forma filament. If
the magnetic reconnection continues for a sufficient length of time,
the changing equilibrium between the growing filament magnetic field
and the overlying, coronal magnetic field will result in a very slow,
simultaneous ascent of both the filament magnetic field and the
overlying coronal magnetic field with greater motion in the outer,
weaker coronal field. This upward stretching of the magnetic fields
eventually results in a closer spacing of oppositely-directed corona)
magnetic fields (resembling a tangential discontinuity) beneath the
filament. As depicted in some flare models, magnetic reconnection then
suddenly occurs in the corona beneath the filament; flare loops form in
the lower part of the reconnected field and a corona) mass ejection and
erupting filament comprise the upper part of the reconnected field. To
illustrate the observable phases of this scenario, we describe the
build-up to two simple eruptive flares in a small active region.
---------------------------------------------------------
Title: The chromospheric and transition region manifestations of an
Ellerman bomb.
Authors: Cook, J. W.; Brueckner, G. E.; Dere, K. P.; Martin, S. F.;
Gayley, K. G.
1992BAAS...24.1074C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Elementary Bipoles of Active Regions and Ephemeral Active
Regions
Authors: Martin, S. F.
1991BAAS...23.1053M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Studies of solar magnetic fields during the rise of solar
cycle 22
Authors: Martin, Sara F.
1991cait.reptQ....M Altcode:
New information about the solar cycle and the changing magnetic fields
includes: (1) Every solar cycle has a duration of 18 to 22 years
even though the peak between successive cycles is approximately 11
years. This means that there are two solar cycles on the sun nearly
all of the time; the exception is the few years preceeding solar
maximum. (2) A large-scale velocity field was discovered around the
perimeter of one of the major active regions that developed during
the rise of the current solar cycle. If averaged over a several month
interval, the velocity would be of the same order of magnitude as
the velocity pattern of the torsional oscillation signal that varies
systematically over the solar cycle. The newly discovered velocity
pattern can be interpreted as either a severe contamination to the
torsional oscillation signal or another way of observing the torsional
oscillation velocity field. (3) The analyses of small-scale magnetic
fields on the quiet sun has shown that network magnetic fields are
continuously being replaced by intranetwork magnetic fields. The
replacement occurs when intranetwork magnetic fields collide with
network magnetic fields; both polarities are observed to cancel
each other at a mean rates of 10<SUP>18</SUP> Maxwells/hour. The
non-cancelling components of the intranetwork magnetic field replace
the cancelled components of the network. No net long-term increases
or decreases in magnetic flux occur as a consequence of these processes.
---------------------------------------------------------
Title: Properties of the Largescale and Smallscale Flow Patterns in
and around AR:19824
Authors: Schrijver, C. J.; Martin, S. F.
1990SoPh..129...95S Altcode:
We trace the photospheric motions of 170 concentrations of magnetic
flux tubes in and around the decaying active region No. 19824 (CMP 23
October 1986), using a series of magnetograms obtained at the Big Bear
Solar Observatory. The magnetograms span an interval of just over five
days and cover an area of about 4 × 5 arc min centered on the active
region. We find a persistent large-scale flow pattern that is superposed
on the small-scale random motions of both polarities. Correction
for differential rotation unveils the systematic, large-scale flow
surrounding the core region of the magnetic plage. The flow (with a
mean velocity of 30 m s<SUP>−1</SUP>) is faster and more pronounced
around the southern side of the core region than around the northern
side, and it accelerates towards the western side of the active
region. The northern and southern branches of the large-scale flow
converge westward of the core region, dragging along the westernmost
sunspot and some of the magnetic flux near it. The overall pattern
of the large-scale flow resembles the flow of a river around a sand
bar. The long-term evolution of the active region suggests that the
flow persists for several months. We discuss the possible association
of the large-scale flow with the torsional oscillation.
---------------------------------------------------------
Title: Elementary bipoles of active regions and ephemeral active
regions
Authors: Martin, Sara F.
1990MmSAI..61..293M Altcode:
The general properties of elementary bipoles (EBs), the class of
moving magnetic features identified by Frazier (1972) as building
blocks of new solar active regions, are described, and variations in
their characteristics are illustrated with extensive videomagnetograms
obtained at Big Bear Solar Observatory during 1984-1989. Consideration
is given to ephemeral active regions consisting of EBs with only
one positive and one negative pole, multiple-pole ephemeral regions,
reversed-polarity EBs, interactions among EBs and adjacent magnetic
features, and the EBs of small and medium active regions. The
detection of EBs prior to the appearance of arch filaments confirms
the relationship found by Frazier.
---------------------------------------------------------
Title: Small-Scale Magnetic Features Observed in the Photosphere
Authors: Martin, S. F.
1990IAUS..138..129M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Conditions for the Formation of Prominences as Inferred from
Optical Observations
Authors: Martin, Sara F.
1990LNP...363....1M Altcode: 1990IAUCo.117....1M; 1990doqp.coll....1M
In the optical region of the electromagnetic spectrum, the conditions
most frequently associated with the formation of prominences are:
(1) the existence of opposite polarity photospheric magnetic fields on
opposing sides of a prominence, (2) a coronal arcade that connects the
magnetic fields on opposing sides of a prominence, (3) a transverse
magnetic field configuration in the chromospheric and photospheric
polarity inversion zones that is approximately perpendicular to the
direction of maximum magnetic field gradient between adjacent patches
of opposite polarity line-of-sight magnetic flux, (4) in active
regions or decaying active regions, the alignment of chromospheric
fibrils in a polarity inversion zone approximately parallel to
the transverse magnetic field component and parallel to the long
axis of the future prominence, (5) the long-term (hours to days)
converging flow of small patches of opposite polarity magnetic flux
towards a common polarity inversion zone, and (6) the cancellation
of encountering patches of magnetic flux of opposite polarity at a
photospheric polarity inversion boundary (interpreted as the transport
of magnetic flux upwards or downwards through the photosphere). Because
these are observed conditions found from magnetograms and filtergrams
at various wavelengths, they do not necessarily represent independent
physical conditions. Although none of these conditions have proven to be
individually sufficient for prominence formation, a combination of 3 of
these conditions might prove to be both necessary and sufficient. The
following hypothesis is offered for study and evaluation: condition
(2) and the combination of conditions (5) and (6), if dynamically
maintained for a sufficient length of time, will invariably result in
the formation of a prominence.
---------------------------------------------------------
Title: Flaring Arches - Part Two
Authors: Svestka, Zdenek; Farnik, Frantisek; Fontenla, Juan M.;
Martin, Sara F.
1989SoPh..123..317S Altcode:
We discuss first the development of the coronal arch-shaped structure of
∼ 57000 km length which was born at or before 08:00 UT on 6 November,
1980 and became the site of 13 quasi-periodic brightenings in hard
X-rays from 10:00 to 14:30 UT. The same structure became the site
of a series of 17 flaring arches between 15:30 and 24:00 UT on that
day. The periodicity of ∼ 19 min, defined well for the quasi-periodic
variations, seems to be partly retained during the occurrence of the
flaring arches.
---------------------------------------------------------
Title: The Footpoints of Giant Arches
Authors: Martin, Sara F.; Svestka, Zdenek F.; Bhatnagar, Arvind
1989SoPh..124..339M Altcode:
We have detected chromospheric footpoints of the giant post-flare
coronal arches discovered by HXIS a few years ago. Hα photographs
obtained at Big Bear and Udaipur Solar Observatories show chromospheric
signatures associated with 5 sequential giant arch events observed
in the interval from 6 to 10 November, 1980. The set of footpoints at
one end of the arches consists of enhancements within a plage at the
northeast periphery of the active region and the set of footpoints at
the other end of the arch consists of brightenings of the chromosphere
south of the active region. Both sets of footpoints show very slow
brightness variations correlated in time with the brightness variations
of the X-ray arches. Current-free modelling of the coronal magnetic
field by Kopp and Poletto (1989), based on a Kitt Peak magnetogram,
confirms the identification of the two sets of footpoints by showing
magnetic field lines connecting them.
---------------------------------------------------------
Title: Correspondence between solar fine-scale structures in the
corona, transition region, and lower atmosphere from collaborative
observations
Authors: Moses, J. Daniel; Cook, J. W.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.; Webb, D. F.; Davis, John M.; Recely, F.; Martin,
S. F.; Zirin, H.
1989sxsr.reptR....M Altcode:
The Soft X-Ray Imaging Payload and the High Resolution Telescope and
Spectrograph (HRTS) instrument were launched from White Sands on 11
December 1987 in coordinated sounding rocket flights to investigate the
correspondence of coronal and transition region structures, especially
the relationship between X-ray bright points (XBPs) and transition
region small spatial scale energetic events. The coaligned data from
X-ray images are presented along with maps of sites of transition
region energetic events observed in C IV (100,000 K), HRTS 1600 A
spectroheliograms of the T<SUB>min</SUB> region and ground based
magnetogram and He I 10830 A images.
---------------------------------------------------------
Title: Mass Motions Associated with Solar Flares
Authors: Martin, Sara F.
1989SoPh..121..215M Altcode: 1989IAUCo.104..215M
Mass motions are a principal means by which components of solar flares
can be distinguished. Typical patterns of mass motions in Hα are
described for chromospheric flare ribbons, remote chromospheric flare
patches, flare loops, flaring arches, surges, erupting filaments and
some expanding coronal features. Interrelationships between these
phenomena are discussed and illustrations of each are presented.
---------------------------------------------------------
Title: Flare energetics.
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veck, N. J.
1989epos.conf..377W Altcode:
The authors have sought to establish a comprehensive and self-consistent
picture of the sources and transport of energy within a flare. To
achieve this goal, they chose five flares in 1980 that were well
observed with instruments on the Solar Maximum Mission, and with other
space-borne and ground-based instruments. The events were chosen to
represent various types of flares. Details of the observations available
for them and the corresponding physical parameters derived from these
data are presented. The flares were studied from two perspectives,
the impulsive and gradual phases, and then the results were compared
to obtain the overall picture of the energetics of these flares. The
authors also discuss the role that modeling can play in estimating the
total energy of a flare when the observationally determined parameters
are used as the input to a numerical model. Finally, a critique of
our current understanding of flare energetics and the methods used to
determine various energetics terms is outlined, and possible future
directions of research in this area are suggested.
---------------------------------------------------------
Title: The identification and interaction of network, intranetwork,
and ephemeral-region magnetic fields
Authors: Martin, Sara F.
1988SoPh..117..243M Altcode:
Network magnetic fields, ephemeral active regions, and intranetwork
magnetic fields are illustrated and discussed in several
contexts. First, they are presented in relation to the appearance
and disappearance of magnetic flux. Second, their properties in
common with all solar magnetic features are discussed. Third,
their distinguishing characteristics are emphasized. Lastly, their
interactions are illustrated.
---------------------------------------------------------
Title: Development of Noble Liquid Detectors for Gamma Ray
Spectroscopy.
Authors: Marquette, William H.; Martin, Sara F.
1988SoPh..117..227M Altcode:
We describe the decay phase of one of the largest active regions of
solar cycle 22 that developed by the end of June 1987. The center of
both polarities of the magnetic fields of the region systematically
shifted north and poleward throughout the decay phase. In addition,
a substantial fraction of the trailing magnetic fields migrated
equatorward and south of the leading, negative fields. The result of
this migration was the apparent rotation of the magnetic axis of the
region such that a majority of the leading polarity advanced poleward at
a faster rate than the trailing polarity. As a consequence, this region
could not contribute to the anticipated reversal of the polar field.
---------------------------------------------------------
Title: The extended solar activity cycle
Authors: Wilson, P. R.; Altrocki, R. C.; Harvey, K. L.; Martin, S. F.;
Snodgrass, H. B.
1988Natur.333..748W Altcode:
The solar cycle has been defined in terms of a sequential periodic
variation in sunspot numbers, the period being the interval between
successive minima, currently averaging 11.2 years. But a number of
observations have indicated that the activity cycle may begin at
higher latitudes before the emergence of the first sunspots of the
new cycle. Here we report results from sunspot cycle 21 concerning
the ephemeral active regions, the coronal green-line emission and the
torsional oscillation signal, which confirm the earlier suggestions. In
particular, we report the appearance of a high-latitude population of
ephemeral active regions in the declin-ing phase of sunspot cycle 21,
with orientations that tend to favour those for cycle 22 rather than
21. Taken together, these data indicate that sunspot activity is simply
the main phase of a more extended cycle that begins at high latitudes
before the maximum of a given sunspot cycle and progresses towards
the equator during the next 18-22 yr, merging with the conventional
'butterfly diagram' (the plot of the latitudes of emerging sunspots
against time) as it enters sunspot latitudes. We suggest that this
extended cycle may be understood in the perspective of a model of
giant convective rolls that generate dynamo waves propagating from
pole to equator.
---------------------------------------------------------
Title: An Eruptive Prominence and Associated Cm-Mm Emission Outside
the Solar Limb
Authors: Zodi, A. M.; Correia, E.; Costa, J. E. R.; Kaufmann, P.;
Martin, S. F.; Kundu, M. R.
1988SoPh..116...83Z Altcode:
We present radio maps at 22 and 44 GHz which show the emission before
and after the eruption of a quiescent prominence located at the west
limb. The observed radiation following the eruption is not consistent
with thermal bremsstrahlung mechanism. It can be interpreted as due
to gyrosynchrotron emission of nonthermal electrons. Our observations
appear to be similar to the microwave radiation observed in post-flare
loops; this radiation is due to nonthermal electrons trapped in the
closed magnetic structures formed after the prominence eruption.
---------------------------------------------------------
Title: The Correspondence Between Small-Scale Coronal Structures
and the Evolving Solar Magnetic Field
Authors: Webb, D. F.; Moses, J. D.; Davis, J. M.; Harvey, J. W.;
Martin, S. F.; Zirin, H.
1988BAAS...20..722W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flaring Arches - Part One
Authors: Martin, Sara F.; Svestka, Zdenek F.
1988SoPh..116...91M Altcode:
`Flaring arches" is a name assigned to a particular component of
some flares. This component consists of X-ray and Hα emission which
traverses a coronal arch from one to the other of its chromospheric
footpoints. The primary footpoint is at the site of a flare. The
secondary footpoint, tens of thousands of kilometers distant from the
source flare, but in the same active region, brightens in Hα concurrent
with the beginning of the hard X-ray burst at the primary site. From the
inferred travel time of the initial exciting agent we deduce that high
speed electron streams travelling through the arch must be the source
of the initial excitation at the secondary footpoint. Subsequently,
a more slowly moving agent gradually enhances the arch first in
X-rays and subsequently in Hα, starting at the primary footpoint and
propagating along the arch trajectory. The plasma flow in Hα shows
clearly that material is injected into the arch from the site of the
primary footpoint and later on, at least in some events, a part of it
is also falling back.
---------------------------------------------------------
Title: Studies of flares and disappearing magnetic flux
Authors: Martin, Sara F.
1988cait.rept.....M Altcode:
Research accomplishments include: (1) research on flaring arches; (2)
a collaborative paper on Anomalously Dense Flare Loops was published;
(3) the footprints of the giant arches previously discovered by
Z. Svestka were found in hydrogen alpha observations from the Big Bear
Solar Observatory and the Udaipur Solar Observatory; (4) several sets
of new observations showing a relationship between cancelling magnetic
fields and flares were acquired and analyzed; and (5) a new hypothesis
is advanced that cancelling magnetic fields are necessary conditions
for the energy build-up to solar flares.
---------------------------------------------------------
Title: The cancellation of magnetic flux on the quiet sun
Authors: Wang, Jingxiu; Shi, Zhongxian; Martin, Sara F.; Livi, Silvia
H. B.
1988VA.....31...79W Altcode:
The mutual loss of magnetic flux in closely spaced, opposite polarity
magnetic fields is herein defined as ;cancellation;. The combination
of two cancelling components is referred to as a cancelling magnetic
feature. In this paper, a classification scheme for cancelling magnetic
features according to the origins of their two halves is proposed;
the observed properties of flux cancellation are summarized. The
cancellation appears to be the observational evidence of magnetic
reconnection taking place in or above the photospheric layer.
---------------------------------------------------------
Title: Multi-thermal observations of newly formed loops in a
dynamic flare
Authors: Švestka, Zdeněk F.; Fontenla, Juan M.; Machado, Marcos E.;
Martin, Sara F.; Neidig, Donald F.; Poletto, Giannina
1987SoPh..108..237S Altcode:
The dynamic flare of 6 November, 1980 (max ≈ 15:26 UT) developed a
rich system of growing loops which could be followed in Hα for 1.5
hr. Throughout the flare, these loops, near the limb, were seen in
emission against the disk. Theoretical computations of deviations from
LTE populations for a hydrogen atom reveal that this requires electron
densities in the loops close to, or in excess of 10<SUP>12</SUP>
cm <SUP>-3</SUP>. From measured widths of higher Balmer lines the
density at the tops of the loops was found to be 4 x 10<SUP>12</SUP>
cm <SUP>-3</SUP> if no non-thermal motions were present, or 5 ×
10<SUP>11</SUP> cm <SUP>-3</SUP> for a turbulent velocity of ~ 12 km
s <SUP>-1</SUP>.
---------------------------------------------------------
Title: The appearance and disappearance of magnetic flux on the
quiet sun
Authors: Zirin, Harold; Martin, Sara F.
1987cait.reptQ....Z Altcode:
Significant new discoveries and findings were made concerning solar
magnetic fields. The majority of magnetic flux on the sun is observed to
disappear when magnetic fields of one polarity migrate into or develop
in juxtaposition with fields of opposite polarity. The cancellation of
magnetic fields can be interpreted as: (a) submergence (b) reconnection
or (c) dissipation (annihilation). Large-scale filaments are observed
to form in the chromosphere immediately above the boundaries between
areas of network magnetic field of opposite polarity where network
cancellation occurs. Small-scale filaments develop in association with
small-scale cancelling magnetic fields at the rate of hundreds per
day. Magnetic fields associated with large-scale solar convection cells,
known as intranetwork magnetic fields, can be detected everywhere on
the visible disk of the sun by using the videomagnetograph to integrate
successive, 1/15 sec. magnetic field images for intervals of 1 to 10
minutes. The intranetwork field appears to be a few seconds of arc in
diameter, and have field strengths of the order of a few to tens of
Gauss. The intranetwork fields appear to originate at the centers of
supergranules and flow to the boundaries of the cells in approximately
radial patterns.
---------------------------------------------------------
Title: Flaring arches
Authors: Martin, Sara F.; Švestka, Zdenek F.
1987SoPh..113..303M Altcode: 1982SoPh..113..303M
No abstract at ADS
---------------------------------------------------------
Title: Do moving magnetic features represent sunspot decay?
Authors: Wang, J. -X.; Martin, S. F.; Livi, S. H. B.
1987PBeiO..10...58W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Characterization of the Total Flare Energy
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.41W Altcode: 1986epos.confE..41W
No abstract at ADS
---------------------------------------------------------
Title: Energetics of the Impulsive Phase
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf..5.5W Altcode: 1986epos.confE...5W
No abstract at ADS
---------------------------------------------------------
Title: Energetics of the Gradual Phase
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.20W Altcode: 1986epos.confE..20W
No abstract at ADS
---------------------------------------------------------
Title: Review of Impulsive Phase Phenomena
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.60W Altcode: 1986epos.confE..60W
No abstract at ADS
---------------------------------------------------------
Title: Small-scale eruptive filaments on the quiet sun.
Authors: Hermans, Linda M.; Martin, Sara F.
1986NASCP2442..369H Altcode: 1986copp.nasa..369H
A study of a little known class of eruptive events on the quiet sun was
conducted. All of 61 small-scale eruptive filamentary structures were
identified in a systematic survey of 32 days of H alpha time-lapse
films of the quiet sun acquired at Big Bear Solar Observatory. When
fully developed, these structures have an average length of 15 arc
seconds before eruption. They appear to be the small-scale analog
of large-scale eruptive filaments observed against the disk. At the
observed rate of 1.9 small-scale eruptive features per field of view
per average 7.0 hour day, the rate of occurence of these events on the
sun were estimated to be greater than 600 per 24 hour day.. The average
duration of the eruptive phase was 26 minutes while the average lifetime
from formation through eruption was 70 minutes. A majority of the
small-scale filamentary sturctures were spatially related to cancelling
magnetic features in line-of-sight photospheric magnetograms. Similar
to large-scale filaments, the small-scale filamentary structures
sometimes divided opposite polarity cancelling fragments but often had
one or both ends terminating at a cancellation site. Their high numbers
appear to reflect the much greater flux on the quiet sun. From their
characteristics, evolution, and relationship to photospheric magnetic
flux, it was concluded that the structures described are small-scale
eruptive filaments and are a subset of all filaments.
---------------------------------------------------------
Title: Recent observations of the formation of filaments.
Authors: Martin, Sara F.
1986NASCP2442...73M Altcode: 1986copp.nasa...73M
Two examples of the formation of small filaments in H alpha are
described and illustrated. In both cases, the formation is seen to be
the spontaneous appearance of strands of absorbing mass that evolve
from no previous structure. The initial development of the filaments
appears to consist of the accumulation of these absorptive strands
along approximately parallel paths in a channel between large-scale,
opposite polarity magnetic fields on either side of the filaments. The
strands exhibit continuous changes in shape and degree of absorption
which can be due to successive condensations resulting in new strands,
mass motions within the strands, and outflow of the mass from the
strands. For at least several hours before the formation of both
filaments, small-scale fragments of opposite polarity, line-of-sight
magnetic flux adjacent to or immediately below the filaments,
and at the ends of the filaments, were cancelling. This type of
magnetic flux disappearance continued during the development of the
filaments and is commonly observed in association with established
filaments. Cancellation is interpreted as an important evolutionary
change in the magnetic field that can lead to configurations suitable
for the formation of filaments.
---------------------------------------------------------
Title: Flares Chosen for Energetics Study
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.47W Altcode: 1986epos.confE..47W
No abstract at ADS
---------------------------------------------------------
Title: Relationships among the Phases
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.39W Altcode: 1986epos.confE..39W
No abstract at ADS
---------------------------------------------------------
Title: The Formation and Decay of Sunspots in Enhanced Solar Network
Authors: Livi, S. H. B.; Martin, S. F.
1986BAAS...18..991L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Small-Scale Eruptive Filaments on the Quiet Sun
Authors: Hermans, L. M.; Martin, S. F.
1986BAAS...18..991H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flaring Arches in Hα and X-Rays
Authors: Martin, S. F.; Svestka, Z.
1986BAAS...18Q.898M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of chromospheric flare dynamics at the next
solar maximum specific recommendations of the Chromospheric Flare
Dynamics Group.
Authors: Canfield, R. C.; Gaizauskas, V.; Kurokawa, H.; Martin, S. F.;
Svestka, Z.
1986lasf.conf..489C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Survey of an active region in H<SUB>&</SUB>alpha;
and X-rays.
Authors: Schadee, Aert; Martin, Sara F.
1986lasf.conf..360S Altcode: 1986lasf.symp..360S
The authors studied Hale Active Region No. 16918 during almost
15 hours of simultaneous observation by Big Bear Solar Observatory
(H<SUB>&</SUB>alpha;) and HXIS (3.5 - 5.5 keV) aboard SMM on 18 -
22 June 1980.
---------------------------------------------------------
Title: Flare energetics.
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
G.; Serio, S.; Sylwester, J.; Veck, N. J.
1986NASCP2439....5W Altcode:
In this investigation of flare energetics, the authors establish a
comprehensive and self-consistent picture of the sources and transport
of energy within a flare. They chose five flares in 1980 that were
well observed with instruments on the SMM, and with other space-borne
and ground-based instruments. Details of the observations available
for them and the corresponding physical parameters derived from these
data are presented. The flares were studied from two perspectives,
the impulsive and gradual phases, and then the results were compared
to obtain the overall picture of the energetics of these flares. The
authors also discuss the role that modeling can play in estimating the
total energy of a flare when the observationally determined parameters
are used as the input to a numerical model.
---------------------------------------------------------
Title: A dynamic flare with anomalously dense flare loops
Authors: Svestka, Z.; Fontenla, J. M.; Machado, M. E.; Martin, S. F.;
Neidig, D. F.; Poletto, G.
1986AdSpR...6f.253S Altcode: 1986AdSpR...6..253S
The dynamic flare of 6 November 1980 (max. ~ 15:26 UT) developed a
rich system of growing loops which could be followed in Hα for 1.5
hours. Throughout the flare, these loops, near the limb, were seen in
emission against the disk. Theoretical computations of b-values for
a hydrogen atom reveal that this requires electron densities in the
loops to be close to 10<SUP>12</SUP> cm<SUP>-3</SUP>. From measured
widths of higher Balmer lines the density at the loops of the loops
was found to be 4 × 10<SUP>12</SUP> cm<SUP>-3</SUP> if no non-thermal
motions were present. It is now general knowledge that flare loops
are initially observed in X-rays and become visible in Hα only after
cooling. For such a high density a loop would cool through radiation
from 10<SUP>7</SUP> K to 10<SUP>4</SUP> K within a few minutes so that
the dense Hα loops should have heights very close to the heights of
the X-ray loops. This, however, contradicts the observations obtained by
the HXIS and FCS instruments on board SMM which show the X-ray loops at
much higher altitudes than the loops in Hα. Therefore, the density must
have been significantly smaller when the loops were formed and the flare
loops were apparently both shrinking and becoming denser while cooling.
---------------------------------------------------------
Title: Ephemeral regions versus pseudo ephemeral regions
Authors: Martin, S. F.; Livi, S. H. B.; Wang, J.; Shi, Z.
1985svmf.nasa..403M Altcode:
New studies of the quiet Sun reveal that ephemeral active regions
constitute minority rather than a majority of all the short lived,
small scale bipolar features on the Sun. In contrast to the recognized
patterns of growth and decay of ephemeral regions, various examples of
the creation of other temporary bipoles nicknamed pseudo ephemeral
regions are illustrated. The pseudo ephemeral regions are the
consequence of combinations of small scale dynamic processes of the
quiet Sun including: (1) fragmentation of network magnetic fields,
(2) the separation of opposite polarity halves of ephemeral regions
as they grow and evolve, and (3) the coalescence of weak network or
intranetwork magnetic fields. New observations offer the possibility
of resolving the discrepancies that have arisen in the association of
ephemeral regions with X-ray bright points. Many X-ray bright points
may be related to those pseudo ephemeral regions which have begun to
exhibit magnetic flux loss.
---------------------------------------------------------
Title: Images of a Major Compact Flare in Hard X-rays and H-alpha
Authors: Svestka, Z.; Martin, S. F.
1985BAAS...17..628S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The cancellation of magnetic flux. I - On the quiet sun
Authors: Livi, S. H. B.; Wang, J.; Martin, S. F.
1985AuJPh..38..855L Altcode:
Digital and photographic magnetograms recorded at 2.5 min intervals
on July 9, 1984 are used to study the disappearance of magnetic flux
in an area of the quiet sun; attention is given to 16 examples of
flux disappearance and three ephemeral regions meeting minimum flux
and change percentage criteria. Flux disappearance is noted to have
occurred only in closely spaced features of opposite polarity, and
is accordingly designated 'cancellation'. The cancellation phenomenon
occurred in combinations of network features, intranetwork features,
and ephemeral regions. It is concluded that cancellation is the dominant
mechanism through which magnetic flux is observed to disappear on the
quiet sun.
---------------------------------------------------------
Title: Ephemeral regions vs. pseudo ephemeral regions.
Authors: Martin, S. F.; Livi, S. H. B.; Wang, J.; Shi, Z.
1985NASCP2374..403M Altcode:
The authors retain the definition of an ephemeral region as a feature
which appears to originate as a compact bipole and grows as a unit
in total flux for at least a short time after its birth. In contrast
to the recognized patterns of growth and decay of ephemeral regions,
various examples of the creation of other temporary bipoles nicknamed
"pseudo ephemeral regions" are illustrated. The pseudo ephemeral regions
are the consequence of combinations of small scale dynamic processes of
the quiet sun including: (1) fragmentation of network magnetic fields,
(2) the separation of opposite polarity halves of ephemeral regions
as they grow and evolve, and (3) the coalescence of weak network or
intra-network magnetic fields. The authors suggest that many X-ray
bright points may be related to the pseudo ephemeral regions. They
also suggest that vector magnetograms should also reveal distinct
differences between real and pseudo ephemeral regions.
---------------------------------------------------------
Title: The cancellation of magnetic flux. II - In a decaying active
region
Authors: Martin, S. F.; Livi, S. H. B.; Wang, J.
1985AuJPh..38..929M Altcode:
An active region was studied in detail during its period of decay from
3 to 8 August 1984 using Hα filtergrams and videomagnetograms acquired
at the Big Bear Solar Observatory. The decay was initiated by a process
of fragmentation in which very small knots of magnetic flux separated
from larger concentrations of flux. The disappearance of magnetic flux
was always observed when the small fragments of flux encountered other
small fragments or concentrations of flux of opposite polarity. This
type of disappearance of magnetic flux, called 'cancellation', is shared
by both polarities of magnetic field. Cancellation was the only observed
means of major loss of flux in the photospheric magnetic fields of the
active region. Approaching fragments of opposite polarity flux always
collided and, after apparent collision, permanent loss of magnetic
flux was subsequently and invariably observed. Thus, cancellation is
a highly predictable phenomenon.
---------------------------------------------------------
Title: The cancellation of magnetic flux II - in a decaying active
region.
Authors: Martin, S. F.; Livi, S. H. B.; Wang, J.
1985MPARp.212..179M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The cancellation of magnetic flux I - on the quiet sun.
Authors: Livi, S. H. B.; Wang, J.; Martin, S. F.
1985MPARp.212..178L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relationships of a growing magnetic flux region to flares
Authors: Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.;
Kucera, A.; Dezső, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.;
Livi, S. H. B.; Wang, J.
1984AdSpR...4g..61M Altcode: 1984AdSpR...4...61M
Some sites for solar flares are known to develop where new magnetic
flux emerges and becomes abutted against opposite polarity pre-existing
magnetic flux (review by Galzauskas/1/). We have identified and analyzed
the evolution of such flare sites at the boundaries of a major new and
growing magnetic flux region within a complex of active regions, Hale
No. 16918. This analysis was done as a part of a continuing study of the
circumstances associated with flares in Hale Region 16918, which was
designated as an FBS target during the interval 18 - 23 June 1980. We
studied the initiation and development of both major and minor flares in
Hα images in relation to the identified potential flare sites at the
boundaries of the growing flux region and to the general development
of the new flux. This study lead to our recognition of a spectrum of
possible relationships of growing flux regions to flares as follows:
(1) intimate interaction with adjacent old flux - flare sites centered
at new/old flux boundary, (2) forced or “intimidated” interaction
in which new flux pushes old field having lower flux density towards a
neighboring old polarity inversion line where a flare then takes place,
(3) “influential” interaction - magnetic lines of force over an old
polarity inversion line, typically containing a filament, reconnect to
the new emerging flux; a flare occurs with erupting filament when the
magnetic field overlying the filament becomes too weak to prevent its
eruption, (4) inconsequential interaction - new flux region is too small
or has wrong orientation for creating flare conditions, (5) incidental -
flare occurs without any significant relationship to new flux regions.
---------------------------------------------------------
Title: Dynamic Signatures of Quiet Sun Magnetic Fields
Authors: Martin, S. F.
1984ssdp.conf...30M Altcode:
Three categories of quiet sun magnetic fields are currently recognized:
network magnetic fields, ephemeral active regions, and intra-network
magnetic fields. A few basic characteristics of each of these types
of magnetic fields are briefly reviewed. The second objective of the
paper is to present new observational data showing interactions between
these types of magnetic fields.
---------------------------------------------------------
Title: Solar-active-region growth rates.
Authors: Hermans, L. M.; Martin, S. F.
1983PASP...95Q.597H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Early Signs of New Active Regions
Authors: Martin, S. F.
1983BAAS...15..971M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Rates of Growth of Active Regions
Authors: Hermans, L. M.; Martin, S. F.
1983BAAS...15..701H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamic signatures of quiet sun magnetic fields
Authors: Martin, S. F.
1983STIN...8420464M Altcode:
The collision and disappearance of opposite polarity fields is observed
most frequently at the borders of network cells. Due to observational
limitations, the frequency, magnitude, and spatial distribution of
magnetic flux loss have not yet been quantitatively determined at the
borders or within the interiors of the cells. However, in agreement with
published hypotheses of other authors, the disapperance of magnetic flux
is speculated to be a consequence of either gradual or rapid magnetic
reconnection which could be the means of converting magnetic energy into
the kinetic, thermal, and nonthermal sources of energy for microflares,
spicules, the solar wind, and the heating of the solar corona.
---------------------------------------------------------
Title: Analysis of flares observed during the solar maximum year
Authors: Zirin, H.; Martin, S. F.; Walton, S. R.
1982cait.rept.....Z Altcode:
This report encompasses three major projects: (1) Qualitative
characterization of the H-alpha profiles of the flare of 5 November
1980 at 2233 UT; (2) Construction of a film projector/digitizer for
the purpose of projecting half-frame 35mm images onto a television
camera detector; (3) Images of solar plages near the limb in broadband
continuum, and analysis thereof. These projects are described in the
respective three sections of this report.
---------------------------------------------------------
Title: Study of the Post-Flare Loops on 1973JUL29 - Part Four -
Revision of T and NE Values and Comparison with the Flare of 1980MAY21
Authors: Švestka, Z.; Dodson-Prince, H. W.; Martin, S. F.; Mohler,
O. C.; Moore, R. L.; Nolte, J. T.; Petrasso, R. D.
1982SoPh...78..271S Altcode:
We present revised values of temperature and density for the flare
loops of 29 July 1973 and compare the revised parameters with those
obtained aboard the SMM for the two-ribbon flare of 21 May 1980. The 21
May flare occurred in a developed sunspot group; the 29 July event was a
spotless two-ribbon flare. We find that the loops in the spotless flare
extended higher (by a factor of 1.4-2.2), were less dense (by a factor
of 5 or more in the first hour of development), were generally hotter,
and the whole loop system decayed much slower than in the spotted flare
(i.e. staying at higher temperature for a longer time). We also align
the hot X-ray loops of the 29 July flare with the bright Hα ribbons
and show that the Hα emission is brightest at the places where the
spatial density of the hot elementary loops is enhanced.
---------------------------------------------------------
Title: Emerging magnetic flux, flares and filaments - FBS interval
16-23 June 1980
Authors: Martin, S. F.; Dezso, L.; Antalova, A.; Kucera, A.; Harvey,
K. L.
1982AdSpR...2k..39M Altcode: 1982AdSpR...2...39M
17 emerging magnetic flux regions with arch filaments related to
new sunspots were identified in Hale Active Region No. 16918 during
the 7 day interval from 16-22 June. Most of the new flux regions
were clustered around the filament channel between the old opposite
polarity fields as were most of the flares. The two largest regions of
new magnetic flux and a few of the smaller flux regions developed very
near the end points of filaments. This suggests that the emergence of
flux in existing active regions might be non-random in position along
a filament channel as well as in distance from a filament channel. <P
/>We have analyzed the positions of 88 flares to date during about
half of each day. We find that slightly more than half (50%) of the
flares, irrespective of their size, are centered within the new flux
regions. About 1/5 (20%) were centered on the border between the new
flux and the adjacent older magnetic field. Less than 1/3 occurred
outside of the newly emerging flux regions but in many cases were very
close to the newly emerging flux. We conclude that at least 2/3 of
the flares are intimately related to the emerging flux regions while
the remaining 1/3 might be either indirectly related or unrelated to
the emerging flux.
---------------------------------------------------------
Title: A Formula for Forecasting the Probability of Eruption of
Quiescent Filaments
Authors: Martin, S. F.; Lawrence, V. W.
1981BAAS...13..847M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A formula for forecasting the probability of eruption of
quiescent filaments.
Authors: Martin, S. F.; Lawrence, V. W.
1981BAAS...13Q.847M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: X-Ray Observations of Two Different Systems of "Post Flare"
Loops
Authors: Svestka, Z.; Dodson-Prince, H. W.; Mohler, O. C.; Martin,
S. F.; Moore, R. L.; Nolte, J. T.; Petrasso, R. D.
1981BAAS...13R.542S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New Information on the Spatial Distribution of Active Regions
Authors: Martin, S. F.; Hermans, L. M.; Marquette, W. H.
1981BAAS...13..551M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preflare conditions, changes and events
Authors: Martin, S. F.
1980SoPh...68..217M Altcode:
Prefiare conditions, changes and events are loosely categorized as
distinct, evolutionary or statistical. Distinct preflare phenomena
are those for which direct physical associations with flares are
implied. Also, they are not known to occur in a like manner during
the absence of flares. These include the early stage of filament
eruptions within active centers, preflare vortical structures, some
transient X-ray emitting features, 5303 Å accelerating coronal arches,
and increases in circular polarization at cm wavelengths. Evolutionary
preflare changes are considered to be any long-term effect that may be
related to the flare build-up even though the same changes may occur in
the absence of flares. This category covers the development of current
sheets or strongly sheared magnetic fields, evolving magnetic features,
emerging flux regions, the development of satellite fields around
sunspots, the evolution of reverse polarity field configurations,
the merging of adjacent active centers, sunspot motions and the
development of velocity patterns. Statistical preflare changes logically
include both distinct and evolutionary preflare changes. However,
in addition, there are preflare conditions and events that are
not necessarily linked to the flare in either a direct physical or
indirect evolutionary way. Such parameters or events that may only
be statistically significant are certain magnetic field properties,
the brightness of active centers at various wavelengths, the previous
occurrence of flares and subflares, increased turbulence in filaments
and certain radio events.
---------------------------------------------------------
Title: Factors Related to the Eruption of Quiescent Filaments
Authors: Hermans, L. M.; Martin, S. F.; Marquette, W. H.
1980BAAS...12..914H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Attempt to Identify Flare Precursor Mass Motions in
Real Time
Authors: Dunn, J. M.; Martin, S. F.
1980BAAS...12..904D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Relationship Between the Eruption of Quiescent Filaments
and the Development of New Active Centers
Authors: Hermans, L. M.; Martin, S. F.
1980BAAS...12..477H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Application of Digital Image Processing Techniques to Faint
Solar Flare Phenomena
Authors: Glackin, D. L.; Martin, S. F.
1980BAAS...12..525G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Comparison of Solar Cycle 21 with Previous Solar Cycles
Authors: Marquette, W. H.; Martin, S. F.
1980BAAS...12..508M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamics of Flare Sprays
Authors: Tandberg-Hanssen, E.; Martin, S. F.; Hansen, R. T.
1980SoPh...65..357T Altcode:
During solar cycle No. 20 new insight into the flare-spray phenomenon
has been attained due to several innovations in solar optical-observing
techniques (higher spatial resolution cinema-photography, tunable
pass-band filters, multi-slit spectroscopy and extended angular
field coronagraphs). From combined analysis of 13 well-observed
sprays which occurred between 1969-1974 we conclude that (i) the
spray material originates from a preexisting active region filament
which undergoes increased absorption some tens of minutes prior to
the abrupt chromospheric brightening at the `flare-start', and (ii)
the spray material is confined within a steadily expanding, loop-shaped
(presumably magnetically controlled) envelope with part of the material
draining back down along one or both legs of the loop.
---------------------------------------------------------
Title: The preflare state
Authors: van Hoven, G.; Barbosa, D. D.; Birn, J.; Cheng, C. -C.;
Hansen, R. T.; Jackson, B. V.; Martin, S. F.; McIntosh, P. S.;
Nakagawa, Y.; Anzer, U.
1980sfsl.work...17V Altcode: 1980sofl.symp...17V
The accumulation, storage and irreversible release of the free
energy necessary for a solar flare are discussed on the basis of data
obtained from the Apollo Telescope Mount on Skylab and other pertinent
sources. Skylab and OSO 7 observations of possible flare precursors
and flare evolution are presented, and the evolution of the flare of
Sept. 5, 1973, the most completely observed flare of the Skylab program,
is described in detail, with account given to magnetic structures and
H alpha radiation. Theories of the preflare state are then reviewed,
with attention given to the force-free fields and coronal arcades,
thermal and magnetic structures and the MHD stability of coronal loops.
---------------------------------------------------------
Title: Mechanical energy output of the 5 September 1973 flare
Authors: Webb, D. F.; Cheng, C. -C.; Dulk, G. A.; Martin, S. F.;
McKenna-Lawlor, S.; McLean, D. J.; Edberg, S. J.
1980sfsl.work..471W Altcode: 1980sofl.symp..471W
The mechanical energy flux of observed macroscopic mass plasma motions
in the solar flare of Sept. 5, 1973, is estimated. Consideration is
given to the cool eruptive material in the eruptive filament and large
surge as revealed by H alpha observations, the moving emission front
seen in Ca II as well as H alpha, the piston-driven shock and mass
ejection coronal transient observed in radio spectra and flare core
motions, and mechanical energy estimates of 5.6 x 10 to the 29th to 8.9
x 10 to the 30th, 9.0 x 10 to the 29th, 2 x 10 to the 30th (thermal)
and 10 to the 31st (magnetic), and 9 x 10 to the 24th erg are obtained,
respectively, in agreement with previous estimates. It is concluded
that the mechanical energy of large-scale mass motions dominates the
radiative output of the flare by more than two orders of magnitude,
and that a significant portion of the mechanical energy is in the form
of magnetic flux delivered to interplanetary space.
---------------------------------------------------------
Title: Forecasting of Solar Flares based on Magnetic Field
Configurations
Authors: Harvey, K. L.; Martin, S. F.
1980STP.....3...30H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Particle acceleration in the process of eruptive opening and
reconnection of magnetic fields
Authors: Svestka, Z.; Martin, S. F.; Kopp, R. A.
1980IAUS...91..217S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Application of digital image processing techniques to faint
solar flare phenomena
Authors: Glackin, D. L.; Martin, S. F.
1980SPIE..264..236G Altcode: 1981SPIE..264..236G
Digital image processing of eight solar flare events was performed using
the Video Information Communication and Retrieval language in order
to study moving emission fronts, flare halos, and Moreton waves. The
techniques used include contrast enhancement, isointensity contouring,
the differencing of images, spatial filtering, and geometrical
registration. The spatial extent and temporal behavior of the faint
phenomena is examined along with the relation of the three types of
phenomena to one another. The image processing techniques make possible
the detailed study of the history of the phenomena and provide clues
to their physical nature.
---------------------------------------------------------
Title: An Experiment in Predicting The Eruption Of Filaments
Authors: Martin, S. F.; Edberg, S. J.; Hermans, L. M.; Dunn, J. M.
1979BAAS...11..659M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ephemeral Active Regions during Solar Minimum
Authors: Martin, S. F.; Harvey, K. H.
1979SoPh...64...93M Altcode:
Ephemeral active regions (ER) identified on Kitt Peak daily full-disk
magnetograms from April through November 1975 were analyzed and
compared with larger active regions during the same interval. The 1975
ER were also compared with ER data from 1970, 1973, 1976, and 1977. ER
were found to vary approximately with the sunspot cycle. However, a
minimum in the number of ER occurred at least one year prior to sunspot
minimum. All evidence to date indicates that the early ER minimum was
due to the rise of solar cycle 21 primarily in the form of ER. ER were
statistically identified as belonging to both outgoing solar cycle 20
and incoming cycle 21 by maxima in their distribution in latitude and by
their statistically dominant orientation as a function of latitude. From
the identification of ER with specific solar cycles and the persistent
presence of high latitude ER maxima since 1970, it is suggested that
the outgoing and incoming solar cycles may co-exist on the sun longer
than the 0-3 year period of overlap between successive cycles already
known from the properties of large sunspot-producing active regions.
---------------------------------------------------------
Title: Study of the Post-Flare Loops on 1973JULY29 - Part Three -
Dynamics of the Hα Loops
Authors: Martin, S. F.
1979SoPh...64..165M Altcode:
Bright and dark curvilinear structures observed between the two major
chromospheric ribbons during the flare of 29 July 1973 on films from
the Big Bear Solar Observatory are interpreted as a typical system of
coronal loops joining the inner boundaries of the separating flare
ribbons. These observations, made through a 0.25 Å Hα filter,
only show small segments of the loops having Doppler shifts within
approximately ± 22 km s<SUP>−1</SUP> relative to the filter
passband centered at Hα, Hα -0.5 Å or Hα +0.5 Å. However, from
our knowledge of the typical behavior of such loop systems observed at
the limb in Hα and at 5303 Å, it has been possible to reconstruct
an appoximate model of the probable development of the loops of the
29 July flare as they would have been viewed at the limb relative to
the position of a prominence which began to erupt a few minutes before
the start of the flare. It is seen that the loops ascended through the
space previously occupied by the filament. On the assumption that Hα
fine structures parallel the magnetic field, we can conclude that a
dramatic reorientation of the direction of the magnetic field in the
corona occurred early in the flare, subsequent to the start of the
eruption of the filament and prior to the time that the Hα loops
ascended through the space previously occupied by the filament.
---------------------------------------------------------
Title: A query into the source of proton emission from solar flares,
report 2
Authors: Martin, S. F.
1979sosylrept.....M Altcode:
Seven solar flares that were followed by major proton events were
examined to determine the diverse and common properties of major
flares. The most probable site of primary proton acceleration
is cospatial with the site and instant of formation of coronal
loops. Because loop formation occurs through the entire duration of
major solar flares over significantly large areas of active centers,
it is proposed that proton injection occurs from a relatively large
volume of space in the corona of active centers and is continuous
throughout, and possibly even after, the visible duration of the
related chromospheric flare. The flare veil is hypothesized to occur
as a result of proton charge exchange taking place in the white-light
transient. The Kopp and Pneuman model of loop formation by magnetic
reconnection is suggested as an adequate and satisfactory model for all
major flares with the provision that the beginning of rapid magnetic
field reconnection is coincident with flare start.
---------------------------------------------------------
Title: Discussion
Authors: Hirayama, T.; Maltby, P.; Malville, J.; Martin, S. F.; Rust,
D. M.; Spicer, D. S.
1979phsp.coll..267H Altcode: 1979IAUCo..44..267H
No abstract at ADS
---------------------------------------------------------
Title: Discussion
Authors: Acton, L. W.; Anzer, U.; Engvold, O.; Martin, S. F.; Pneuman,
G. W.; Rust, D. M.; Tandberg-Hanssen, E.; Zirin, H.
1979phsp.coll..164A Altcode: 1979IAUCo..44..164A
No abstract at ADS
---------------------------------------------------------
Title: Application of Digital Image Processing to Solar Data
Authors: Glackin, D. L.; Martin, S. F.
1978BAAS...10..641G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ephemeral Active Regions during Solar Minimum.
Authors: Harvey, K. L.; Martin, S. F.
1978BAAS...10..417H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interpretations of the Moving Emission Front Observed with
the Flare of 5 September 1973.
Authors: Martin, S. F.
1978BAAS...10Q.462M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Inferences about the Rotation and Eruption of Prominences.
Authors: Martin, S. F.; Hansen, R. T.
1977BAAS....9..314M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ephemeral active regions during the solar minimum. 1: General
properties and trends over the solar cycle. 2: Characteristics of
individual ephemeral regions
Authors: Martin, S. F.; Harvey, K. L.
1976sosylrept.....M Altcode:
General properties of ephemeral active regions were studied using Kitt
Peak daily magnetograms from Apr. - Nov. 1975. Although this interval
was prior to sunspot minimum, ephemeral regions related to incoming
cycle 21 were already more numerous than ephemeral regions related to
outgoing cycle 20. The transition between the old and new solar cycle
was identified by a reversal of the statistically dominant orientation
of regions and sometimes by a minimum in the latitude distribution
where adjacent cycles overlapped. During this interval the transition
between cycle 20 and 21 was at N18 deg and S24 deg. Comparing this 1975
data with previously studied data from 1970 and 1973, we find evidence
that incoming cycle 21 was already present on the sun at middle and high
latitudes in 1973 and 1970. Extrapolating backward and forward in time
from these three periods, we find that it is conceivable that two solar
cycles may be present on the sun at all times. It appears that further
statistical studies of ephemeral active regions may yield long-term
prognostic information on the future course of solar activity. The
birth of 90 ephemeral regions was recorded. Prior to the birth of
regions, existing network was found to disappear or show lateral
displacement. The growth and decay rates of regions were comparable. In
the decaying phase, some flux elements simply disappeared; some merged
with network or other elements of regions of similar polarity; some
collided and simultaneously disappeared with network or elements of
other regions of opposite polarity. All clearly identifiable ephemeral
regions dissipated by these processes while continuing to expand.
---------------------------------------------------------
Title: Early recognition of major solar flares in Halpha .
Authors: Martin, S. F.; Ramsey, H. E.
1976npsa.conf..301M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Comparison of Flares in Hα and D<SUB>3</SUB> (He I).
Authors: Ramsey, H. E.; Martin, S. F.; Harvey, K. L.
1975BAAS....7..424R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Helical Motion in an Eruptive Prominence.
Authors: Martin, S. F.; Hansen, R. T.
1975BAAS....7..472M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A comparison of flares and prominences in D3 and H(alpha)
Authors: Ramsey, H. E.; Martin, S. F.; Harvey, K. L.
1975lock.rept.....R Altcode:
During 1973, flares were photographed using a 0.4A filter on the D3
line of HeI and, in 1974, with an additional passband at 0.8A into
the red wing. During most of this period, time-lapse photographs also
were taken on either or both the H(alpha) multi-slit spectrograph
and the H(alpha) Doppler filter. On a separate telescope, limb events
were photographed in D3 and H(alpha) through similar 8A filters. Very
few flares displayed D3 in emission in part of the flare. For large
flares, some absorption parts of the D3 flare correspond closely to the
H(alpha) flare both spatially and temporally. However, the D3 flare
boundaries are more sharply defined. It seemed D3 absorption events
were correlated more frequently with surges and active filaments than
with flare elements. The relative brightness of D3 and H(alpha) were
examined for a number of solar phenomena observed at the limb. High
velocity portions of surges, erupting filaments and loops brightened
more in H(alpha) were examined for a number of solar phenomena observed
at the limb. High velocity portions of surges, erupting filaments
and loops brightened more in H(alpha) than in D3. In limb flares,
D3 brightened more than H(alpha).
---------------------------------------------------------
Title: Ephemeral Active Regions in 1970 and 1973
Authors: Harvey, K. L.; Harvey, J. W.; Martin, S. F.
1975SoPh...40...87H Altcode:
A study of ephemeral active regions (ER) identified on good quality
full-disk magnetograms reveals: On the average 373 and 179 ER were
present on the Sun in 1970 and 1973 respectively. The number varies
with the solar cycle.
---------------------------------------------------------
Title: A multi-slit spectrograph and Hα Doppler system
Authors: Martin, S. F.; Ramsey, H. E.; Carroll, G. A.; Martin, D. C.
1974SoPh...37..343M Altcode:
A multiple entrance slit spectrograph was built for time-lapse
photography of the spectra of flares and other transient solar
phenomena. This spectrograph employs narrow-band filters to limit the
wavelength range of the spectrograph to several angstroms centered
at Hα or other spectral lines. The passband of the filter, and
the dispersion of the spectrograph determine the number of parallel
slits through which light may be passed to achieve multiple adjacent
spectral displays. By using a 7 Å filter, a dispersion of 10.8 Å
mm<SUP>−1</SUP>, and 35 mm film, adjacent Hα spectra are imaged
from 30 parallel slits. A system of mirrors and relay lenses transfers
the slitjaw image to the same film plane as the spectral image. A 2
frame camera is used to simultaneously record both images on adjacent
frames. Filtering of the reference spatial image to 1.0 Å allows
the observer to see the position of the slits relative to the Hα
centerline structure and to match the brightness of the spatial image
to the spectral display. A polarizing beamsplitter, prior to the slits,
provides a prefiltered second solar image to a narrow band Hα Doppler
filter for simultaneous photography in the wings of the Hα line. The
multislit monochromatic spectrograph and Hα Doppler system constitute
a flexible instrument in which components may be substituted to achieve
different passbands width, image scales, dispersions and corresponding
numbers and spacings of adjacent spectra at a selected wavelength.
---------------------------------------------------------
Title: Ephemeral active regions in 1970 and 1973
Authors: Harvey, K. L.; Martin, S. F.; Harvey, J. W.
1974lock.reptR....H Altcode:
The work reported here was undertaken to learn more about the spatial
distribution of Ephemeral active regions (ER), lifetime, solar
cycle variation, and association with major active centers. Primary
consideration was given to the question of whether or not ER represent,
in part, a new class of solar activity or are simply small active
regions.
---------------------------------------------------------
Title: Correlation of a Flare-Wave and Type II Burst
Authors: Harvey, Karen L.; Martin, Sara F.; Riddle, Anthony C.
1974SoPh...36..151H Altcode:
We have studied the relation of a flare-induced wave and the type II and
III radio bursts associated with the 26 April 1969, 2258 UT flare. Our
observations suggest the flare-wave and type II bursts were produced
by a common source.
---------------------------------------------------------
Title: Rare Observations of the Flare-Related Wave Effects
Authors: Martin, S. F.; Harvey, K. L.
1974fpsw.conf...39M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ephemeral Active Regions
Authors: Harvey, Karen L.; Martin, Sara F.
1973SoPh...32..389H Altcode:
Ephemeral active regions attain maximum development within 1 day or
less of their initial appearance and are typically observed for 1-2
days. They appear mostly as small bipolar regions having a typical
dimension of about 30000 km and a maximum total flux of the order of
10<SUP>20</SUP> Mx. The ephemeral regions generally do not produce
sunspots and flares, though they are identified in Hα as small
active centers.
---------------------------------------------------------
Title: The Evolution of Prominences and Their Relationship to Active
Centers (A Review)
Authors: Martin, Sara F.
1973SoPh...31....3M Altcode:
A necessary condition for the formation of prominences is established
where components of the magnetic field of opposite sign lie
juxtaposed. This condition is sometimes recognizable prior to the
formation of prominences in active centers and between adjacent
active centers in Hα by paths of fibrils aligned nearly end to
end. Prominences are usually not found in active regions until they are
about 4 days old. After this time, the number of prominences appears
to be a function of the large-scale complexities in the magnetic field
pattern whether these are a result of emerging flux, the merging of
adjacent active centers, or the coalescing of remnant fields of active
centers. Prominences may disappear by the slow or rapid flow of mass
into the chromosphere or by the more violent eruptives. The formation
of new active centers has been associated with the eruption of some
filaments related to weak chromospheric fields.
---------------------------------------------------------
Title: A Multi-Slit Spectrograph
Authors: Martin, Sara F.
1973BAAS....5S.276M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Early Recognition of Major Solar Flares in Hα
Authors: Martin, S. F.; Ramsey, H. E.
1972PrAA...30..371M Altcode:
No abstract at ADS
