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Author name code: sterling
ADS astronomy entries on 2022-09-14
author:"Sterling, Alphonse" 

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Title: Genesis and Coronal-jet-generating Eruption of a Solar
    Minifilament Captured by IRIS Slit-raster Spectra
Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Moore, Ronald L.;
   Sterling, Alphonse C.; De Pontieu, Bart
2022arXiv220900059P    Altcode:
  We present the first IRIS Mg II slit-raster spectra that fully capture
  the genesis and coronal-jet-generating eruption of a central-disk solar
  minifilament. The minifilament arose in a negative-magnetic-polarity
  coronal hole. The Mg II spectroheliograms verify that the minifilament
  plasma temperature is chromospheric. The Mg II spectra show that
  the erupting minifilament's plasma has blueshifted upflow in the
  jet spire's onset and simultaneous redshifted downflow at the
  location of the compact jet bright point (JBP). From the Mg II
  spectra together with AIA EUV images and HMI magnetograms, we find:
  (i) the minifilament forms above a flux cancelation neutral line
  at an edge of a negative-polarity network flux clump; (ii) during
  the minifilament's fast-eruption onset and jet-spire onset, the
  JBP begins brightening over the flux-cancelation neutral line. From
  IRIS2 inversion of the Mg II spectra, the JBP's Mg II bright plasma
  has electron density, temperature, and downward (red-shift) Doppler
  speed of 1012 cm^-3, 6000 K, and 10 kms, respectively, and the growing
  spire shows clockwise spin. We speculate: (i) during the slow rise
  of the erupting minifilament-carrying twisted flux rope, the top of
  the erupting flux-rope loop, by writhing, makes its field direction
  opposite that of encountered ambient far-reaching field; (ii) the
  erupting kink then can reconnect with the far-reaching field to make
  the spire and reconnect internally to make the JBP. We conclude that
  this coronal jet is normal in that magnetic flux cancelation builds a
  minifilament-carrying twisted flux rope and triggers the JBP-generating
  and jet-spire-generating eruption of the flux rope.

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Title: NuSTAR observations of a quiet Sun minifilament eruption
Authors: Hannah, Iain; Sterling, Alphonse; Grefenstette, Brian;
   Glesener, Lindsay; White, Stephen; Smith, David; Cooper, Kristopher;
   Krucker, Sam; Paterson, Sarah; Hudson, Hugh
2022cosp...44.2538H    Altcode:
  We present a unique set of observations of a confined minifilament
  eruption from the quiet-Sun during solar minimum. The Nuclear
  Spectroscopic Telescope Array (NuSTAR) spotted a tiny, compact hard
  X-ray (HXR) flare on 2019 April 26, peaking about 02:06UT for a few
  minutes, finding brief emission >5MK. Observations with SDO/AIA
  and Hinode/XRT show this HXR emission was due to a tiny flare arcade
  underneath a confined minifilament eruption - behaviour similar to those
  seen in both major active-region filament eruptions and minifilament
  eruptions that lead to coronal jets. Line-of-sight magnetograms from
  SDO/HMI show that this eruption is due to opposite polarity flux
  moving together and cancelling and not due to flux emergence. This
  eruption occurred near disk-centre, so the Earth orbiting observatories
  provide a top-down view of the event, but fortuitously a side-on view
  is obtained from STEREO-A/SECCHI, giving a clearer sense of eruption
  geometry. We also explore the possibility of non-thermal emission
  due to accelerated electrons in the NuSTAR HXR observations of this
  small-scale phenomena in the quiet Sun.

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Title: Bipolar Ephemeral Active Regions, Magnetic Flux Cancellation,
    and Solar Magnetic Explosions
Authors: Moore, Ronald L.; Panesar, Navdeep K.; Sterling, Alphonse C.;
   Tiwari, Sanjiv K.
2022ApJ...933...12M    Altcode: 2022arXiv220313287M
  We examine the cradle-to-grave magnetic evolution of 10 bipolar
  ephemeral active regions (BEARs) in solar coronal holes, especially
  aspects of the magnetic evolution leading to each of 43 obvious
  microflare events. The data are from the Solar Dynamics Observatory: 211
  Å coronal EUV images and line-of-sight photospheric magnetograms. We
  find evidence that (1) each microflare event is a magnetic explosion
  that results in a miniature flare arcade astride the polarity
  inversion line (PIL) of the explosive lobe of the BEAR's anemone
  magnetic field; (2) relative to the BEAR's emerged flux-rope Ω loop,
  the anemone's explosive lobe can be an inside lobe, an outside lobe,
  or an inside-and-outside lobe; (3) 5 events are confined explosions,
  20 events are mostly confined explosions, and 18 events are blowout
  explosions, which are miniatures of the magnetic explosions that
  make coronal mass ejections (CMEs); (4) contrary to the expectation
  of Moore et al., none of the 18 blowout events explode from inside
  the BEAR's Ω loop during the Ω loop's emergence; and (5) before
  and during each of the 43 microflare events, there is magnetic flux
  cancellation at the PIL of the anemone's explosive lobe. From finding
  evident flux cancellation at the underlying PIL before and during all
  43 microflare events-together with BEARs evidently being miniatures of
  all larger solar bipolar active regions-we expect that in essentially
  the same way, flux cancellation in sunspot active regions prepares
  and triggers the magnetic explosions for many major flares and CMEs.

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Title: Homologous Compact Major Blowout-eruption Solar Flares and
    their Production of Broad CMEs
Authors: Sahu, Suraj; Joshi, Bhuwan; Sterling, Alphonse C.; Mitra,
   Prabir K.; Moore, Ronald L.
2022ApJ...930...41S    Altcode: 2022arXiv220303954S
  We analyze the formation mechanism of three homologous broad coronal
  mass ejections (CMEs) resulting from a series of solar blowout-eruption
  flares with successively increasing intensities (M2.0, M2.6, and
  X1.0). The flares originated from NOAA Active Region 12017 during
  2014 March 28-29 within an interval of ≍24 hr. Coronal magnetic
  field modeling based on nonlinear force-free field extrapolation
  helps to identify low-lying closed bipolar loops within the flaring
  region enclosing magnetic flux ropes. We obtain a double flux rope
  system under closed bipolar fields for all the events. The sequential
  eruption of the flux ropes led to homologous flares, each followed by a
  CME. Each of the three CMEs formed from the eruptions gradually attained
  a large angular width, after expanding from the compact eruption-source
  site. We find these eruptions and CMEs to be consistent with the
  "magnetic-arch-blowout" scenario: each compact-flare blowout eruption
  was seated in one foot of a far-reaching magnetic arch, exploded up
  the encasing leg of the arch, and blew out the arch to make a broad CME.

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Title: Another Look at Erupting Minifilaments at the Base of Solar
    X-Ray Polar Coronal "Standard" and "Blowout" Jets
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Panesar, Navdeep K.
2022ApJ...927..127S    Altcode: 2022arXiv220112314S
  We examine 21 solar polar coronal jets that we identify in soft X-ray
  images obtained from the Hinode/X-ray telescope (XRT). We identify 11 of
  these as blowout jets and four as standard jets (with six uncertain),
  based on their X-ray-spire widths being respectively wide or narrow
  (compared to the jet's base) in the XRT images. From corresponding
  extreme ultraviolet (EUV) images from the Solar Dynamics Observatory's
  (SDO) Atmospheric Imaging Assembly (AIA), essentially all (at least
  20 of 21) of the jets are made by minifilament eruptions, consistent
  with other recent studies. Here, we examine the detailed nature of the
  erupting minifilaments (EMFs) in the jet bases. Wide-spire ("blowout")
  jets often have ejective EMFs, but sometimes they instead have an
  EMF that is mostly confined to the jet's base rather than ejected. We
  also demonstrate that narrow-spire ("standard") jets can have either
  a confined EMF, or a partially confined EMF where some of the cool
  minifilament leaks into the jet's spire. Regarding EMF visibility:
  we find that in some cases the minifilament is apparent in as few as
  one of the four EUV channels we examined, being essentially invisible
  in the other channels; thus, it is necessary to examine images from
  multiple EUV channels before concluding that a jet does not have an
  EMF at its base. The sizes of the EMFs, measured projected against the
  sky and early in their eruption, is 14″ ± 7″, which is within a
  factor of 2 of other measured sizes of coronal-jet EMFs.

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Title: Further Evidence for the Minifilament-eruption Scenario for
    Solar Polar Coronal Jets
Authors: Baikie, Tomi K.; Sterling, Alphonse C.; Moore, Ronald L.;
   Alexander, Amanda M.; Falconer, David A.; Savcheva, Antonia; Savage,
   Sabrina L.
2022ApJ...927...79B    Altcode: 2022arXiv220108882B
  We examine a sampling of 23 polar-coronal-hole jets. We first identified
  the jets in soft X-ray (SXR) images from the X-ray telescope (XRT) on
  the Hinode spacecraft, over 2014-2016. During this period, frequently
  the polar holes were small or largely obscured by foreground coronal
  haze, often making jets difficult to see. We selected 23 jets among
  those adequately visible during this period, and examined them further
  using Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly
  (AIA) 171, 193, 211, and 304 Å images. In SXRs, we track the lateral
  drift of the jet spire relative to the jet base's jet bright point
  (JBP). In 22 of 23 jets, the spire either moves away from (18 cases)
  or is stationary relative to (4 cases) the JBP. The one exception
  where the spire moved toward the JBP may be a consequence of
  line-of-sight projection effects at the limb. From the AIA images,
  we clearly identify an erupting minifilament in 20 of the 23 jets,
  while the remainder are consistent with such an eruption having taken
  place. We also confirm that some jets can trigger the onset of nearby
  "sympathetic" jets, likely because eruption of the minifilament field of
  the first jet removes magnetic constraints on the base-field region of
  the second jet. The propensity for spire drift away from the JBP, the
  identification of the erupting minifilament in the majority of jets,
  and the magnetic-field topological changes that lead to sympathetic
  jets, all support or are consistent with the minifilament-eruption
  model for jets.

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Title: Birth and Evolution of a Jet-Base-Topology Solar Magnetic
    Field with Four Consecutive Major Flare Explosions
Authors: Doran, Ilana; Panesar, Navdeep K.; Tiwari, Sanjiv; Moore,
   Ron; Bobra, Monica; Sterling, Alphonse
2021AGUFMSH35B2039D    Altcode:
  During 2011 September 6-8, NOAA solar active region (AR) 11283
  produced four consecutive major coronal mass ejections (CMEs) each
  with a co-produced major flare (GOES class M5.3, X2.1, X1.8, and
  M6.7). We examined the ARs magnetic field evolution leading to and
  following each of these major solar magnetic explosions. We follow
  flux emergence, flux cancellation and magnetic shear buildup leading
  to each explosion, and look for sudden flux changes and shear changes
  wrought by each explosion. We use AIA 193 A images and line-of-sight
  HMI vector magnetograms from Solar Dynamics Observatory (SDO), and
  SunPy, SHARPkeys, and IDL Solarsoft to prepare and analyze these
  data. The observed evolution of the vector field informs how magnetic
  field emergence and cancellation lead to and trigger the magnetic
  explosions, and thus informs how major CMEs and their flares are
  produced. We find that (1) all four flares are triggered by flux
  cancellation, (2) the third and fourth explosions (X1.8 and M6.7)
  begin with a filament eruption from the cancellation neutral line,
  (3) in the first and second explosions a filament erupts in the core
  of a secondary explosion that lags the main explosion and is probably
  triggered by Hudson-effect field implosion under the adjacent main
  exploding field, and (4) the transverse field suddenly strengthens along
  each main explosions underlying neutral line during the explosion,
  also likely due to Hudson-effect field implosion. Our observations
  are consistent with flux cancellation at the explosions underlying
  neutral line being essential in the buildup and triggering of each
  of the four explosions in the same way as in smaller-scale magnetic
  explosions that drive coronal jets.

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Title: Studying Solar Active-Region Magnetic Evolution Leading to
    a Confined Eruption
Authors: Zigament, Benjamin; Sterling, Alphonse; Moore, Ronald;
   Falconer, David
2021AGUFMSH35B2037Z    Altcode:
  Current research suggests that there exists a continuum of solar
  eruptions ranging from the comparatively small, such as coronal jets,
  to extremely large eruptions that produce coronal mass ejections (CMEs)
  and solar flares, with all sharing a common triggering mechanism: a
  filament/flux rope eruption triggered by magnetic flux cancellation. For
  coronal jets the erupting "minifilaments" are of length ~10,000 km
  (Sterling et al. 2015, Panesar et al. 2016), while the larger eruptions
  are accompanied by eruptions of typical filaments of size ~several x
  10^4 --- ~3x10^5 km. Sterling et al. (2018) examined this idea for
  two small ARs (flux ~ 2x10^21 Mx) that erupted to make CMEs. They
  tracked the evolution of the ARs from emergence to eruption and found
  eruption to occur when some of the emerged flux drifted together and
  underwent cancellation along the main magnetic neutral line on the
  interior of the AR, with eruption occurring after about 30---50% of
  the total flux of the respective regions canceled. Here we perform a
  similar study, using Solar Dynamics Observatory (SDO) AIA EUV images and
  SDO/HMI magnetograms, of a smaller AR (total flux <~10^21 Mx) that
  emerged in isolation near the neutral line in a large overarching old
  weak-field magnetic arcade on 2014 September 8. It produced a confined
  eruption (i.e., one that did not make a CME) about three days later,
  on September 10 near 18:45 UT. The ARs flux reached maximum about 12
  hr after emergence start, and then decreased continuously, with the
  decrease being partly from cancellation of small flux clumps in the
  interior of the AR. The eruption occurred when the flux had decreased
  by about 20%, and was centered on the neutral line of the emerged AR,
  but also involved filament-holding field along some of the old arcades
  neutral line. That filament underwent a confined eruption as part of
  the overall confined eruption. The emerged ARs being inside the larger
  arcade, its smaller size, and its smaller amount of cancellation may
  be reasons why the eruption was confined, instead of being ejective
  and producing a CME as in the two cases of Sterling et al (2018). This
  work was supported by funding from NASA's HGI Program.

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Title: Probing Upflowing Regions in the Quiet Sun and Coronal Holes
Authors: Schwanitz, Conrad; Harra, Louise; Raouafi, Nour E.; Sterling,
   Alphonse C.; Moreno Vacas, Alejandro; del Toro Iniesta, Jose Carlos;
   Orozco Suárez, David; Hara, Hirohisa
2021SoPh..296..175S    Altcode: 2021arXiv211012753S
  Recent observations from Parker Solar Probe have revealed that the
  solar wind has a highly variable structure. How this complex behaviour
  is formed in the solar corona is not yet known, since it requires
  omnipresent fluctuations, which constantly emit material to feed
  the wind. In this article we analyse 14 upflow regions in the solar
  corona to find potential sources for plasma flow. The upflow regions
  are derived from spectroscopic data from the EUV Imaging Spectrometer
  (EIS) on board Hinode determining their Doppler velocity and defining
  regions which have blueshifts stronger than −6 kms−<SUP>1</SUP>. To
  identify the sources of these blueshift data from the Atmospheric
  Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI),
  on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope
  (XRT), on board Hinode, are used. The analysis reveals that only 5 out
  of 14 upflows are associated with frequent transients, like obvious
  jets or bright points. In contrast to that, seven events are associated
  with small-scale features, which show a large variety of dynamics. Some
  resemble small bright points, while others show an eruptive nature, all
  of which are faint and only live for a few minutes; we cannot rule out
  that several of these sources may be fainter and, hence, less obvious
  jets. Since the complex structure of the solar wind is known, this
  suggests that new sources have to be considered or better methods used
  to analyse the known sources. This work shows that small and frequent
  features, which were previously neglected, can cause strong upflows in
  the solar corona. These results emphasise the importance of the first
  observations from the Extreme-Ultraviolet Imager (EUI) on board Solar
  Orbiter, which revealed complex small-scale coronal structures.

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Title: Relation of Microstreams in the Polar Solar Wind to Switchbacks
    and Coronal X-Ray Jets
Authors: Neugebauer, Marcia; Sterling, Alphonse C.
2021ApJ...920L..31N    Altcode: 2021arXiv211000079N
  Ulysses data obtained at high solar latitudes during periods of
  minimum solar activity in 1994 and 2007 are examined to determine the
  relation between velocity structures called microstreams and folds in
  the magnetic field called switchbacks. A high correlation is found. The
  possibility of velocity peaks in microstreams originating from coronal
  X-ray jets is reexamined; we now suggest that microstreams are the
  consequence of the alternation of patches of switchbacks and quiet
  periods, where the switchbacks could be generated by minifilament/flux
  rope eruptions that cause coronal jets.

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Title: What Causes Faint Solar Coronal Jets From Emerging Flux
    Regions In Coronal Holes?
Authors: Harden, A.; Panesar, N.; Moore, R.; Sterling, A.; Adams, M.
2021AAS...23821314H    Altcode:
  Using EUV images and line-of-sight magnetograms from Solar Dynamics
  Observatory, we examine eight emerging bipolar magnetic regions (BMRs)
  in central-disk coronal holes for whether the emerging magnetic arch
  made any noticeable coronal jets directly, via reconnection with
  ambient open field as modeled by Yokoyama &amp; Shibata (1995). During
  emergence, each BMR produced no obvious EUV coronal jet of normal
  brightness, but each produced one or more faint EUV coronal jets that
  are discernible in AIA 193 Å images. The spires of these jets are much
  fainter and usually narrower than for typical EUV jets that have been
  observed to be produced by minifilament eruptions in quiet regions and
  coronal holes. For each of 26 faint jets from the eight emerging BMRs,
  we examine whether the faint spire was evidently made a la Yokoyama
  &amp; Shibata (1995). We find: (1) 16 of these faint spires evidently
  originate from sites of converging opposite-polarity magnetic flux
  and show base brightenings like those in minifilament-eruption-driven
  coronal jets, (2) the 10 other faint spires maybe were made by a burst
  of the external-magnetic-arcade-building reconnection of the emerging
  magnetic arch with the ambient open field, reconnection directly driven
  by the arch's emergence, but (3) none were unambiguously made by such
  emergence-driven reconnection. Thus, for these eight emerging BMRs,
  the observations indicate that emergence-driven external reconnection
  of the emerging magnetic arch with ambient open field at most produces
  a jet spire that is much fainter than in previously-reported, much
  more obvious coronal jets driven by minifilament eruptions.

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Title: Network Jets As The Driver Of Counter-streaming Flows In A
    Solar Filament
Authors: Panesar, N. K.; Tiwari, S.; Moore, R.; Sterling, A.
2021AAS...23820506P    Altcode:
  We investigate the driving mechanism of counter-streaming flows
  in a solar filament, using EUV images from SDO/AIA, line of sight
  magnetograms from SDO/HMI, IRIS SJ images, and H-alpha data from
  GONG. We find that: (i) persistent counter-streaming flows along
  adjacent threads of a small (100" long) solar filament is present;
  (ii) both ends of the solar filament are rooted at the edges of
  magnetic network flux lanes; (iii) recurrent small-scale jets (also
  known as network jets) occur at both ends of the filament; (iv) some
  of the network jets occur at the sites of flux cancelation between the
  majority-polarity flux and merging minority-polarity flux patches;
  (v) these multiple network jets clearly drive the counter-streaming
  flows along the adjacent threads of the solar filament for ~2 hours
  with an average speed of 70 km s<SUP>-1</SUP>; (vi) some the network
  jets show base brightenings, analogous to the base brightenings of
  coronal jets; and (vii) the filament appears wider (4") in EUV images
  than in H-alpha images (2.5"), consistent with previous studies. Thus,
  our observations show that counter-streaming flows in the filament
  are driven by network jets and possibly these driving network jet
  eruptions are prepared and triggered by flux cancelation.

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Title: The Missing Cool Corona In The Flat Magnetic Field Around
    Solar Active Regions
Authors: Singh, T.; Sterling, A.; Moore, R.
2021AAS...23831321S    Altcode:
  SDO/AIA images the full solar disk in several EUV bands that are
  each sensitive to coronal plasma emissions of one or more specific
  temperatures. We observe that when isolated active regions (ARs) are on
  the disk, full-disk images in some of the coronal EUV channels show the
  outskirts of the AR as a dark moat surrounding the AR. Here we present
  several specific examples, selected from time periods when there was
  only a single AR present on the disk. Visually, moats are observed to
  be most prominent in the AIA 171 Angstrom band, which has the most
  sensitivity to emission from plasma at log10 T = 5.8. By using the
  emission measure distribution with temperature, we find the intensity
  of the moat to be most depressed over the temperature range log10 T ~
  5.7-6.2 for all the cases. We argue that the dark moat exists because
  the pressure from the strong magnetic field that splays out from the
  AR presses down on underlying magnetic loops, flattening those loops
  — along with the lowest of the AR's own loops over the moat — to a
  low altitude. Those loops, which would normally emit the bulk of the
  171 Angstrom emission, are restricted to heights above the surface
  that are too low to have 171 Angstrom emitting plasmas sustained in
  them, while hotter EUV-emitting plasmas are sustained in the overlying
  higher-altitude long AR-rooted coronal loops. This potentially explains
  the low-coronal-temperature dark moats surrounding the ARs.

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Title: On Making Magnetic-flux-rope Omega Loops For Solar Bipolar
    Magnetic Regions Of All Sizes By Convection Cells
Authors: Moore, R.; Tiwari, S.; Panesar, N.; Sterling, A.
2021AAS...23831318M    Altcode:
  This poster gives an overview of Moore, R. L., Tiwari, S. K., Panesar,
  N. K., &amp; Sterling, A. C. 2020, ApJ Letters, 902:L35. We propose that
  the magnetic-flux-rope omega loop that emerges to become any bipolar
  magnetic region (BMR) is made by a convection cell of the omega-loop's
  size from initially horizontal magnetic field ingested through the
  cell's bottom. This idea is based on (1) observed characteristics of
  BMRs of all spans (~1000 to ~200,000 km), (2) a well-known simulation
  of the production of a BMR by a supergranule-sized convection cell
  from horizontal field placed at cell bottom, and (3) a well-known
  convection-zone simulation. From the observations and simulations,
  we (1) infer that the strength of the field ingested by the biggest
  convection cells (giant cells) to make the biggest BMR omega loops
  is ~10<SUP>3</SUP> G, (2) plausibly explain why the span and flux of
  the biggest observed BMRs are ~200,000 km and ~10<SUP>22</SUP> Mx,
  (3) suggest how giant cells might also make "failed BMR" omega loops
  that populate the upper convection zone with horizontal field, from
  which smaller convection cells make BMR omega loops of their size,
  (4) suggest why sunspots observed in a sunspot cycle's declining
  phase tend to violate the hemispheric helicity rule, and (5) support a
  previously proposed amended Babcock scenario (Moore, R. L., Cirtain,
  J. W., &amp; Sterling, A. C. 2016, arXiv:1606.05371) for the sunspot
  cycle's dynamo process. Because the proposed convection-based heuristic
  model for making a sunspot-BMR omega loop avoids having ~10<SUP>5</SUP>
  G field in the initial flux rope at the bottom of the convection zone,
  it is an appealing alternative to the present magnetic-buoyancy-based
  standard scenario and warrants testing by high-enough-resolution
  giant-cell magnetoconvection simulations.

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Title: Coronal-jet-producing Minifilament Eruptions As A Possible
    Source Of Parker Solar Probe (PSP) Switchbacks
Authors: Sterling, A.; Moore, R.
2021AAS...23812306S    Altcode:
  The Parker Solar Probe (PSP) has observed copious rapid magnetic field
  direction changes in the near-Sun solar wind. These features have
  been called "switchbacks," and their origin is a mystery. But their
  widespread nature suggests that they may be generated by a frequently
  occurring process in the Sun's atmosphere. We examine the possibility
  that the switchbacks originate from coronal jets. Recent work suggests
  that many coronal jets result when photospheric magnetic flux cancels,
  and forms a small-scale "minifilament" flux rope that erupts and
  reconnects with coronal field. We argue that the reconnected erupting
  minifilament flux rope can manifest as an outward propagating Alfvenic
  fluctuation that steepens into an increasingly compact disturbance as
  it moves through the solar wind. Using previous observed properties
  of coronal jets that connect to coronagraph-observed white-light
  jets (a.k.a. "narrow CMEs"), along with typical solar wind speed
  values, we expect the coronal-jet-produced disturbances to traverse
  near-perihelion PSP in less than or about 25 min, with a velocity of
  about 400 km/s. To consider further the plausibility of this idea, we
  show that a previously studied series of equatorial latitude coronal
  jets, originating from the periphery of an active region, generate
  white-light jets in the outer corona (seen in STEREO/COR2 coronagraph
  images; 2.5 — 15 solar radii), and into the inner heliosphere (seen
  in STEREO/Hi1 heliospheric imager images; 15 — 84 solar radii). Thus
  it is tenable that disturbances put onto open coronal magnetic field
  lines by coronal-jet-producing erupting minifilament flux ropes can
  propagate out to PSP space and appear as switchbacks. This work was
  supported by the NASA Heliophysics Division, and by the NASA/MSFC
  Hinode Project. For further details see Sterling &amp; Moore (2020,
  ApJ, 896, L18).

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Title: What Causes Faint Solar Coronal Jets from Emerging Flux
    Regions in Coronal Holes?
Authors: Harden, Abigail R.; Panesar, Navdeep K.; Moore, Ronald L.;
   Sterling, Alphonse C.; Adams, Mitzi L.
2021ApJ...912...97H    Altcode: 2021arXiv210307813H
  Using EUV images and line-of-sight magnetograms from Solar Dynamics
  Observatory, we examine eight emerging bipolar magnetic regions (BMRs)
  in central-disk coronal holes for whether the emerging magnetic arch
  made any noticeable coronal jets directly, via reconnection with ambient
  open field as modeled by Yokoyama &amp; Shibata. During emergence,
  each BMR produced no obvious EUV coronal jet of normal brightness, but
  each produced one or more faint EUV coronal jets that are discernible
  in AIA 193 &amp;angst; images. The spires of these jets are much
  fainter and usually narrower than for typical EUV jets that have been
  observed to be produced by minifilament eruptions in quiet regions and
  coronal holes. For each of 26 faint jets from the eight emerging BMRs,
  we examine whether the faint spire was evidently made a la Yokoyama
  &amp; Shibata. We find that (1) 16 of these faint spires evidently
  originate from sites of converging opposite-polarity magnetic flux
  and show base brightenings like those in minifilament-eruption-driven
  coronal jets, (2) the 10 other faint spires maybe were made by a burst
  of the external-magnetic-arcade-building reconnection of the emerging
  magnetic arch with the ambient open field, with reconnection directly
  driven by the arch's emergence, but (3) none were unambiguously made by
  such emergence-driven reconnection. Thus, for these eight emerging BMRs,
  the observations indicate that emergence-driven external reconnection
  of the emerging magnetic arch with ambient open field at most produces
  a jet spire that is much fainter than in previously reported, much
  more obvious coronal jets driven by minifilament eruptions.

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Title: Fine-Scale Features of the Sun's Atmosphere: Spicules and Jets
Authors: Sterling, Alphonse C.
2021GMS...258..221S    Altcode:
  No abstract at ADS

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Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
    (DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
   Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
   Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
   Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
   Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
   Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
   Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
   Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
   Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
   Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
   Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
   Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
   Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
   Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
   Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
   Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
   Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
   E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
   Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
   Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
   Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
   Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
   A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
   Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
   Instrument Scientists; DKIST Science Working Group; DKIST Critical
   Science Plan Community
2021SoPh..296...70R    Altcode: 2020arXiv200808203R
  The National Science Foundation's Daniel K. Inouye Solar Telescope
  (DKIST) will revolutionize our ability to measure, understand,
  and model the basic physical processes that control the structure
  and dynamics of the Sun and its atmosphere. The first-light DKIST
  images, released publicly on 29 January 2020, only hint at the
  extraordinary capabilities that will accompany full commissioning of
  the five facility instruments. With this Critical Science Plan (CSP)
  we attempt to anticipate some of what those capabilities will enable,
  providing a snapshot of some of the scientific pursuits that the DKIST
  hopes to engage as start-of-operations nears. The work builds on the
  combined contributions of the DKIST Science Working Group (SWG) and
  CSP Community members, who generously shared their experiences, plans,
  knowledge, and dreams. Discussion is primarily focused on those issues
  to which DKIST will uniquely contribute.

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Title: The Missing Cool Corona in the Flat Magnetic Field around
    Solar Active Regions
Authors: Singh, Talwinder; Sterling, Alphonse C.; Moore, Ronald L.
2021ApJ...909...57S    Altcode: 2020arXiv201215406S
  Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly
  (AIA) images the full solar disk in several extreme-ultraviolet
  (EUV) bands that are each sensitive to coronal plasma emissions of
  one or more specific temperatures. We observe that when isolated
  active regions (ARs) are on the disk, full-disk images in some of
  the coronal EUV channels show the outskirts of the AR as a dark
  moat surrounding the AR. Here we present seven specific examples,
  selected from time periods when there was only a single AR present
  on the disk. Visually, we observe the moat to be most prominent in
  the AIA 171 Å band, which has the most sensitivity to emission from
  plasma at log<SUB>10</SUB> T = 5.8. By examining the 1D line-of-sight
  emission measure temperature distribution found from six AIA EUV
  channels, we find the intensity of the moat to be most depressed over
  the temperature range log<SUB>10</SUB> T ≍ 5.7-6.2 for most of the
  cases. We argue that the dark moat exists because the pressure from
  the strong magnetic field that splays out from the AR presses down
  on underlying magnetic loops, flattening those loops—along with the
  lowest of the AR's own loops over the moat—to a low altitude. Those
  loops, which would normally emit the bulk of the 171 Å emission, are
  restricted to heights above the surface that are too low to have 171
  Å emitting plasmas sustained in them, according to Antiochos &amp;
  Noci, while hotter EUV-emitting plasmas are sustained in the overlying
  higher-altitude long AR-rooted coronal loops. This potentially explains
  the low-coronal-temperature dark moats surrounding the ARs.

---------------------------------------------------------
Title: Coronal Jets Observed at Sites of Magnetic Flux Cancelation
Authors: Panesar, Navdeep Kaur; Sterling, Alphonse; Moore, Ronald;
   Tiwari, Sanjiv Kumar
2021cosp...43E1783P    Altcode:
  Solar jets of all sizes are magnetically channeled narrow eruptive
  events; the larger ones are often observed in the solar corona in EUV
  and coronal X-ray images. Recent observations show that the buildup and
  triggering of the minifilament eruptions that drive coronal jets result
  from magnetic flux cancelation under the minifilament, at the neutral
  line between merging majority-polarity and minority-polarity magnetic
  flux patches. Here we investigate the magnetic setting of on-disk
  small-scale jets (also known as jetlets) by using high resolution 172A
  images from the High-resolution Coronal Imager (Hi-C2.1) and EUV images
  from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly
  (AIA), and UV images from the Interface Region Imaging Spectrograph
  (IRIS), and line-of-sight magnetograms from the SDO/Helioseismic
  and Magnetic Imager (HMI). We observe jetlets at edges of magnetic
  network lanes. From magnetograms co-aligned with the Hi-C, IRIS,
  and AIA images, we find that the jetlets stem from sites of flux
  cancelation between merging majority-polarity and minority-polarity
  flux patches, and some of the jetlets show faint brightenings at their
  bases reminiscent of the base brightenings in coronal jets. Based on
  these observations of jetlets and our previous observations of ∼90
  coronal jets in quiet regions and coronal holes, we infer that flux
  cancelation is the essential process in the buildup and triggering of
  jetlets. Our observations suggest that network jetlet eruptions are
  small-scale analogs of both larger-scale coronal jet eruptions and
  the still-larger-scale eruptions that make major CMEs.

---------------------------------------------------------
Title: Network Jets as the Driver of Counter-streaming Flows in a
    Solar Filament
Authors: Panesar, N. K.; Tiwari, S. K.; Moore, R. L.; Sterling, A. C.
2020AGUFMSH0240004P    Altcode:
  We investigate the driving mechanism of counter-streaming flows
  in a solar filament, using EUV images from SDO/AIA, line of sight
  magnetograms from SDO/HMI, IRIS SJ images, and H-alpha data from
  GONG. We find that: (i) persistent counter-streaming flows along
  adjacent threads of a small (100" long) solar filament is present;
  (ii) both ends of the solar filament are rooted at the edges of
  magnetic network flux lanes; (iii) recurrent small-scale jets (also
  known as network jets) occur at both ends of the filament; (iv) some
  of the network jets occur at the sites of flux cancelation between the
  majority-polarity flux and merging minority-polarity flux patches;
  (v) these multiple network jets clearly drive the counter-streaming
  flows along the adjacent threads of the solar filament for ~2 hours
  with an average speed of 70 km s<SUP>-1</SUP>; (vi) some the network
  jets show base brightenings, analogous to the base brightenings of
  coronal jets; and (vii) the filament appears wider (4") in EUV images
  than in H-alpha images (2.5"), consistent with previous studies. Thus,
  our observations show that counter-streaming flows in the filament
  are driven by network jets and possibly these driving network jet
  eruptions are prepared and triggered by flux cancelation.

---------------------------------------------------------
Title: On Making Magnetic-flux-rope Ω Loops for Solar Bipolar
    Magnetic Regions of All Sizes by Convection Cells
Authors: Moore, Ronald L.; Tiwari, Sanjiv K.; Panesar, Navdeep K.;
   Sterling, Alphonse C.
2020ApJ...902L..35M    Altcode: 2020arXiv200913694M
  We propose that the flux-rope Ω loop that emerges to become any bipolar
  magnetic region (BMR) is made by a convection cell of the Ω-loop's size
  from initially horizontal magnetic field ingested through the cell's
  bottom. This idea is based on (1) observed characteristics of BMRs
  of all spans (∼1000 to ∼200,000 km), (2) a well-known simulation
  of the production of a BMR by a supergranule-sized convection cell
  from horizontal field placed at cell bottom, and (3) a well-known
  convection-zone simulation. From the observations and simulations,
  we (1) infer that the strength of the field ingested by the biggest
  convection cells (giant cells) to make the biggest BMR Ω loops is
  ∼10<SUP>3</SUP> G, (2) plausibly explain why the span and flux of
  the biggest observed BMRs are ∼200,000 km and ∼10<SUP>22</SUP>
  Mx, (3) suggest how giant cells might also make "failed-BMR" Ω loops
  that populate the upper convection zone with horizontal field, from
  which smaller convection cells make BMR Ω loops of their size, (4)
  suggest why sunspots observed in a sunspot cycle's declining phase
  tend to violate the hemispheric helicity rule, and (5) support a
  previously proposed amended Babcock scenario for the sunspot cycle's
  dynamo process. Because the proposed convection-based heuristic model
  for making a sunspot-BMR Ω loop avoids having ∼10<SUP>5</SUP> G
  field in the initial flux rope at the bottom of the convection zone,
  it is an appealing alternative to the present magnetic-buoyancy-based
  standard scenario and warrants testing by high-enough-resolution
  giant-cell magnetoconvection simulations.

---------------------------------------------------------
Title: Possible Evolution of Minifilament-Eruption-Produced Solar
    Coronal Jets, Jetlets, and Spicules, into Magnetic-Twist-Wave
    “Switchbacks” Observed by the Parker Solar Probe (PSP)
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Panesar, Navdeep K.;
   Samanta, Tanmoy
2020JPhCS1620a2020S    Altcode: 2020arXiv201012991S
  Many solar coronal jets result from erupting miniature-filament
  (“minifilament”) magnetic flux ropes that reconnect with encountered
  surrounding far-reaching field. Many of those minifilament flux
  ropes are apparently built and triggered to erupt by magnetic flux
  cancelation. If that cancelation (or some other process) results in
  the flux rope’s field having twist, then the reconnection with the
  far-reaching field transfers much of that twist to that reconnected
  far-reaching field. In cases where that surrounding field is open, the
  twist can propagate to far distances from the Sun as a magnetic-twist
  Alfvénic pulse. We argue that such pulses from jets could be the
  kinked-magnetic-field structures known as “switchbacks,” detected
  in the solar wind during perihelion passages of the Parker Solar Probe
  (PSP). For typical coronal-jet-generated Alfvénic pulses, we expect
  that the switchbacks would flow past PSP with a duration of several
  tens of minutes; larger coronal jets might produce switchbacks with
  passage durations ∼1hr. Smaller-scale jet-like features on the Sun
  known as “jetlets” may be small-scale versions of coronal jets,
  produced in a similar manner as the coronal jets. We estimate that
  switchbacks from jetlets would flow past PSP with a duration of a few
  minutes. Chromospheric spicules are jet-like features that are even
  smaller than jetlets. If some portion of their population are indeed
  very-small-scale versions of coronal jets, then we speculate that the
  same processes could result in switchbacks that pass PSP with durations
  ranging from about ∼2 min down to tens of seconds.

---------------------------------------------------------
Title: Sequential Lid Removal in a Triple-decker Chain of
    CME-producing Solar Eruptions
Authors: Joshi, Navin Chandra; Sterling, Alphonse C.; Moore, Ronald
   L.; Joshi, Bhuwan
2020ApJ...901...38J    Altcode: 2020arXiv200804525J
  We investigate the onsets of three consecutive coronal mass ejection
  (CME) eruptions in 12 hr from a large bipolar active region (AR)
  observed by the Solar Dynamics Observatory (SDO), the Solar Terrestrial
  Relations Observatory (STEREO), the Reuven Ramaty High Energy Solar
  Spectroscopic Imager (RHESSI), and the Geostationary Operational
  Environmental Satellite (GOES). Evidently, the AR initially had a
  "triple-decker" configuration: three flux ropes in a vertical stack
  above the polarity inversion line (PIL). Upon being bumped by a confined
  eruption of the middle flux rope, the top flux rope erupts to make the
  first CME and its accompanying AR-spanning flare arcade rooted in a far
  apart pair of flare ribbons. The second CME is made by eruption of the
  previously arrested middle flux rope, which blows open the flare arcade
  of the first CME and produces a flare arcade rooted in a pair of flare
  ribbons closer to the PIL than those of the first CME. The third CME
  is made by blowout eruption of the bottom flux rope, which blows open
  the second flare arcade and makes its own flare arcade and pair of
  flare ribbons. Flux cancellation observed at the PIL likely triggers
  the initial confined eruption of the middle flux rope. That confined
  eruption evidently triggers the first CME eruption. The lid-removal
  mechanism instigated by the first CME eruption plausibly triggers the
  second CME eruption. Further lid removal by the second CME eruption
  plausibly triggers the final CME eruption.

---------------------------------------------------------
Title: Network Jets as the Driver of Counter-streaming Flows in a
    Solar Filament/Filament Channel
Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Moore, Ronald L.;
   Sterling, Alphonse C.
2020ApJ...897L...2P    Altcode: 2020arXiv200604249P
  Counter-streaming flows in a small (100″ long) solar filament/filament
  channel are directly observed in high-resolution Solar Dynamics
  Observatory (SDO)/Atmospheric Imaging Assembly (AIA) extreme-ultraviolet
  (EUV) images of a region of enhanced magnetic network. We combine
  images from SDO/AIA, SDO/Helioseismic and Magnetic Imager (HMI), and the
  Interface Region Imaging Spectrograph (IRIS) to investigate the driving
  mechanism of these flows. We find that: (I) counter-streaming flows are
  present along adjacent filament/filament channel threads for ∼2 hr,
  (II) both ends of the filament/filament channel are rooted at the
  edges of magnetic network flux lanes along which there are impinging
  fine-scale opposite-polarity flux patches, (III) recurrent small-scale
  jets (known as network jets) occur at the edges of the magnetic network
  flux lanes at the ends of the filament/filament channel, (IV) the
  recurrent network jet eruptions clearly drive the counter-streaming
  flows along threads of the filament/filament channel, (V) some
  of the network jets appear to stem from sites of flux cancelation,
  between network flux and merging opposite-polarity flux, and (VI) some
  show brightening at their bases, analogous to the base brightening in
  coronal jets. The average speed of the counter-streaming flows along the
  filament/filament channel threads is 70 km s<SUP>-1</SUP>. The average
  widths of the AIA filament/filament channel and the Hα filament are
  4″ and 2"5, respectively, consistent with the earlier findings
  that filaments in EUV images are wider than in Hα images. Thus,
  our observations show that the continually repeated counter-streaming
  flows come from network jets, and these driving network jet eruptions
  are possibly prepared and triggered by magnetic flux cancelation.

---------------------------------------------------------
Title: Coronal-jet-producing Minifilament Eruptions as a Possible
    Source of Parker Solar Probe Switchbacks
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2020ApJ...896L..18S    Altcode: 2020arXiv200604990S
  The Parker Solar Probe (PSP) has observed copious rapid magnetic
  field direction changes in the near-Sun solar wind. These features
  have been called "switchbacks," and their origin is a mystery. But
  their widespread nature suggests that they may be generated by a
  frequently occurring process in the Sun's atmosphere. We examine the
  possibility that the switchbacks originate from coronal jets. Recent
  work suggests that many coronal jets result when photospheric
  magnetic flux cancels, and forms a small-scale "minifilament" flux
  rope that erupts and reconnects with coronal field. We argue that the
  reconnected erupting-minifilament flux rope can manifest as an outward
  propagating Alfvénic fluctuation that steepens into an increasingly
  compact disturbance as it moves through the solar wind. Using previous
  observed properties of coronal jets that connect to coronagraph-observed
  white-light jets (a.k.a. "narrow CMEs"), along with typical solar
  wind speed values, we expect the coronal-jet-produced disturbances to
  traverse near-perihelion PSP in ≲25 minutes, with a velocity of ∼400
  km s<SUP>-1</SUP>. To consider further the plausibility of this idea,
  we show that a previously studied series of equatorial latitude coronal
  jets, originating from the periphery of an active region, generate
  white-light jets in the outer corona (seen in STEREO/COR2 coronagraph
  images; 2.5-15 R<SUB>⊙</SUB>), and into the inner heliosphere (seen in
  Solar-Terrestrial Relations Observatory (STEREO)/Hi1 heliospheric imager
  images; 15-84 R<SUB>⊙</SUB>). Thus it is tenable that disturbances
  put onto open coronal magnetic field lines by coronal-jet-producing
  erupting-minifilament flux ropes can propagate out to PSP space and
  appear as switchbacks.

---------------------------------------------------------
Title: Onset of Magnetic Explosion in Solar Coronal Jets in Quiet
    Regions on the Central Disk
Authors: Panesar, Navdeep K.; Moore, Ronald L.; Sterling, Alphonse C.
2020ApJ...894..104P    Altcode: 2020arXiv200604253P
  We examine the initiation of 10 coronal jet eruptions in quiet
  regions on the central disk, thereby avoiding near-limb spicule-forest
  obscuration of the slow-rise onset of the minifilament eruption. From
  the Solar Dynamics Observatory/Atmospheric Imaging Assembly 171 Å 12
  s cadence movie of each eruption, we (1) find and compare the start
  times of the minifilament's slow rise, the jet-base bright point,
  the jet-base-interior brightening, and the jet spire, and (2) measure
  the minifilament's speed at the start and end of its slow rise. From
  (a) these data, (b) prior observations showing that each eruption was
  triggered by magnetic flux cancelation under the minifilament, and
  (c) the breakout-reconnection current sheet observed in one eruption,
  we confirm that quiet-region jet-making minifilament eruptions are
  miniature versions of CME-making filament eruptions, and surmise that
  in most quiet-region jets: (1) the eruption starts before runaway
  reconnection starts, (2) runaway reconnection does not start until
  the slow-rise speed is at least ∼1 km s<SUP>-1</SUP>, and (3) at
  and before eruption onset, there is no current sheet of appreciable
  extent. We therefore expect that (I) many CME-making filament eruptions
  are triggered by flux cancelation under the filament, (II) emerging
  bipoles seldom, if ever, directly drive jet production because the
  emergence is seldom, if ever, fast enough, and (III) at a separatrix
  or quasi-separatrix in any astrophysical setting of a magnetic field
  in low-beta plasma, a current sheet of appreciable extent can be built
  only dynamically by a magnetohydrodynamic convulsion of the field,
  not by quasi-static gradual converging of the field.

---------------------------------------------------------
Title: Possible Production of Solar Spicules by Microfilament
    Eruptions
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Samanta, Tanmoy;
   Yurchyshyn, Vasyl
2020ApJ...893L..45S    Altcode: 2020arXiv200404187S
  We examine Big Bear Solar Observatory (BBSO) Goode Solar Telescope
  (GST) high spatial resolution (0"06), high-cadence (3.45 s), Hα-0.8
  Å images of central-disk solar spicules, using data of Samanta et
  al. We compare with coronal-jet chromospheric-component observations
  of Sterling et al. Morphologically, bursts of spicules, referred to as
  "enhanced spicular activities" by Samanta et al., appear as scaled-down
  versions of the jet's chromospheric component. Both the jet and the
  enhanced spicular activities appear as chromospheric-material strands,
  undergoing twisting-type motions of ∼20-50 km s<SUP>-1</SUP>
  in the jet and ∼20-30 km s<SUP>-1</SUP> in the enhanced spicular
  activities. Presumably, the jet resulted from a minifilament-carrying
  magnetic eruption. For two enhanced spicular activities that we
  examine in detail, we find tentative candidates for corresponding
  erupting microfilaments, but not the expected corresponding base
  brightenings. Nonetheless, the enhanced-spicular-activities'
  interacting mixed-polarity base fields, frequent-apparent-twisting
  motions, and morphological similarities to the coronal jet's
  chromospheric-temperature component, suggest that erupting
  microfilaments might drive the enhanced spicular activities but be hard
  to detect, perhaps due to Hα opacity. Degrading the BBSO/GST-image
  resolution with a 1"0-FWHM smoothing function yields enhanced spicular
  activities resembling the "classical spicules" described by, e.g.,
  Beckers. Thus, a microfilament eruption might be the fundamental driver
  of many spicules, just as a minifilament eruption is the fundamental
  driver of many coronal jets. Similarly, a 0"5-FWHM smoothing renders
  some enhanced spicular activities to resemble previously reported
  "twinned" spicules, while the full-resolution features might account
  for spicules sometimes appearing as 2D-sheet-like structures.

---------------------------------------------------------
Title: Hi-C 2.1 Observations of Small-scale
    Miniature-filament-eruption-like Cool Ejections in an Active Region
    Plage
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Panesar, Navdeep
   K.; Reardon, Kevin P.; Molnar, Momchil; Rachmeler, Laurel A.; Savage,
   Sabrina L.; Winebarger, Amy R.
2020ApJ...889..187S    Altcode: 2019arXiv191202319S
  We examine 172 Å ultra-high-resolution images of a solar plage region
  from the High-Resolution Coronal Imager, version 2.1 (Hi-C 2.1, or Hi-C)
  rocket flight of 2018 May 29. Over its five minute flight, Hi-C resolved
  a plethora of small-scale dynamic features that appear near noise level
  in concurrent Solar Dynamics Observatory (SDO) Atmospheric Imaging
  Assembly (AIA) 171 Å images. For 10 selected events, comparisons with
  AIA images at other wavelengths and with Interface Region Imaging
  Spectrograph (IRIS) images indicate that these features are cool
  (compared to the corona) ejections. Combining Hi-C 172 Å, AIA 171 Å,
  IRIS 1400 Å, and Hα, we see that these 10 cool ejections are similar
  to the Hα "dynamic fibrils" and Ca II "anemone jets" found in earlier
  studies. The front of some of our cool ejections are likely heated,
  showing emission in IRIS 1400 Å. On average, these cool ejections
  have approximate widths 3"2 ± 2"1, (projected) maximum heights and
  velocities 4"3 ± 2"5 and 23 ± 6 km s<SUP>-1</SUP>, and lifetimes 6.5
  ± 2.4 min. We consider whether these Hi-C features might result from
  eruptions of sub-minifilaments (smaller than the minifilaments that
  erupt to produce coronal jets). Comparisons with SDO's Helioseismic and
  Magnetic Imager (HMI) magnetograms do not show magnetic mixed-polarity
  neutral lines at these events' bases, as would be expected for true
  scaled-down versions of solar filaments/minifilaments. But the features'
  bases are all close to single-polarity strong-flux-edge locations,
  suggesting possible local opposite-polarity flux unresolved by HMI. Or
  it may be that our Hi-C ejections instead operate via the shock-wave
  mechanism that is suggested to drive dynamic fibrils and the so-called
  type I spicules.

---------------------------------------------------------
Title: Early Results from the Solar-Minimum 2019 Total Solar Eclipse
Authors: Pasachoff, J. M.; Lockwood, C. A.; Inoue, J. L.; Meadors,
   E. N.; Voulgaris, A.; Sliski, D.; Sliski, A.; Reardon, K. P.; Seaton,
   D. B.; Caplan, R. M.; Downs, C.; Linker, J. A.; Sterling, A. C.
2020AAS...23535903P    Altcode:
  We report on first results from our observations in Chile on July
  2, 2019, that revealed the extreme-solar-minimum corona, with only
  equatorial streamers and with visible polar plumes. We have observations
  in clear skies from our three observing sites: (1) The Cerro Tololo
  Inter-American Observatory, 7,240-foot altitude, 2 min 6 sec; (2)
  La Higuera, centerline, 2,500-foot altitude, 2 min 35 sec totality;
  (3) La Serena, sea level, 2 min 15 sec totality. Prominences on the
  limb provided orientation and coordination with spacecraft observations
  from NOAA's GOES-R Solar Ultraviolet Imager (SUVI) and the Atmospheric
  Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory (SDO). The
  double-diamond ring at second contact will extend our determination of
  a new IAU-recommended value of the solar diameter through comparison
  with models taking into account the precise lunar profile. Our coronal
  spectra from slitless spectrographs, from CTIO, showed the Fe XIV 530.3
  nm green line substantially weaker than the Fe X 637.4 nm red line,
  corresponding to the relatively low coronal temperature at this phase
  of the solar-activity cycle. On the spectra we also detected the weak
  coronal emission line of Ar X at 553.3 nm, as we also detected at
  the previous total solar eclipse of August 21, 2017, in the USA. We
  show a comparison of the eclipse observation with a prediction of the
  structure of the corona from an MHD model, carried out by Predictive
  Science Inc. (PSI). We consider the lines of sight to NASA's Parker
  Solar Probe at the times of total eclipses, when we can examine the
  coronal imaging in terms of electron density to compare with the in
  situ measurements. <P />We received major support from grant AGS-903500
  from the Solar Terrestrial Program, Atmospheric and Geospace Sciences
  Division, U.S. National Science Foundation. The CTIO site was courtesy
  of Associated Universities for Research in Astronomy (AURA). We had
  additional student support from the Massachusetts NASA Space Grant
  Consortium; Sigma Xi; the Global Initiatives Fund at Williams College;
  and the University of Pennsylvania. PSI was supported by AFOSR, NASA,
  and NSF. ACS received support from the NASA/HGI program, and from
  the MSFC Hinode project. AV thanks the mathematician Christophoros
  Mouratidis for his help with the data reduction of the spectra.

---------------------------------------------------------
Title: Early results from the solar-minimum 2019 total solar eclipse
Authors: Pasachoff, Jay M.; Lockwood, Christian A.; Inoue, John L.;
   Meadors, Erin N.; Voulgaris, Aristeidis; Sliski, David; Sliski, Alan;
   Reardon, Kevin P.; Seaton, Daniel B.; Caplan, Ronald M.; Downs, Cooper;
   Linker, Jon A.; Schneider, Glenn; Rojo, Patricio; Sterling, Alphonse C.
2020IAUS..354....3P    Altcode:
  We observed the 2 July 2019 total solar eclipse with a variety of
  imaging and spectroscopic instruments recording from three sites
  in mainland Chile: on the centerline at La Higuera, from the Cerro
  Tololo Inter-American Observatory, and from La Serena, as well
  as from a chartered flight at peak totality in mid-Pacific. Our
  spectroscopy monitored Fe X, Fe XIV, and Ar X lines, and we imaged Ar
  X with a Lyot filter adjusted from its original H-alpha bandpass. Our
  composite imaging has been compared with predictions based on modeling
  using magnetic-field measurements from the pre-eclipse month. Our
  time-differenced sites will be used to measure motions in coronal
  streamers.

---------------------------------------------------------
Title: A Two-Sided-Loop X-Ray Solar Coronal Jet and a Sudden
    Photospheric Magnetic-field Change, Both Driven by a Minifilament
    Eruption
Authors: Sterling, A. C.; Harra, L. K.; Moore, R. L.; Falconer, D. A.
2019AGUFMSH11D3382S    Altcode:
  Most of the commonly discussed solar coronal jets are of the
  type consisting of a <P />single spire extending approximately
  vertically from near the solar surface into the <P />corona. Recent
  research shows that eruption of a miniature filament (minifilament)
  <P />drives at least many such single-spire jets, and concurrently
  generates a miniflare at the <P />eruption site. A different type of
  coronal jet, identified in X-ray images during the <P />Yohkoh era, are
  two-sided-loop jets, which extend from a central excitation location <P
  />in opposite directions, along two opposite low-lying coronal loops
  that are more-or-less <P />horizontal to the surface. We observe such
  a two-sided-loop jet from the edge of active <P />region (AR) 12473,
  using data from Hinode XRT and EIS, and SDO AIA and HMI. Similar <P />to
  single-spire jets, this two-sided-loop jet results from eruption of a
  minifilament, which <P />accelerates to over 140 km/s before abruptly
  stopping upon striking overlying <P />nearly-horizontal magnetic field
  at ∼ 30,000 km altitude and producing the two-sided-loop <P />jet
  via interchange reconnection. Analysis of EIS raster scans show that
  a hot <P />brightening, consistent with a small flare, develops in the
  aftermath of the eruption, <P />and that Doppler motions (∼ 40 km/s)
  occur near the jet-formation region. As with <P />many single-spire
  jets, the trigger of the eruption here is apparently magnetic <P />flux
  cancelation, which occurs at a rate of ∼ 4×10^18 Mx/hr, comparable
  to the rate <P />observed in some single-spire AR jets. An apparent
  increase in the (line-of-sight) <P />flux occurs within minutes of
  onset of the minifilament eruption, consistent with the <P />apparent
  increase being due to a rapid reconfiguration of low-lying magnetic
  field <P />during the minifilament eruption. Details appear in Sterling
  et al. (2019, ApJ, 871, 220).

---------------------------------------------------------
Title: Hi-C 2.1 Observations of Jetlet-like Events at Edges of Solar
    Magnetic Network Lanes
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
   Winebarger, Amy R.; Tiwari, Sanjiv K.; Savage, Sabrina L.; Golub, Leon
   E.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
   Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
   Peter, Hardi; Testa, Paola; Walsh, Robert W.; Warren, Harry P.
2019ApJ...887L...8P    Altcode: 2019arXiv191102331P
  We present high-resolution, high-cadence observations of six,
  fine-scale, on-disk jet-like events observed by the High-resolution
  Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We
  combine the Hi-C 2.1 images with images from the Solar Dynamics
  Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and the Interface
  Region Imaging Spectrograph (IRIS), and investigate each event’s
  magnetic setting with co-aligned line-of-sight magnetograms from the
  SDO/Helioseismic and Magnetic Imager (HMI). We find that (i) all six
  events are jetlet-like (having apparent properties of jetlets), (ii)
  all six are rooted at edges of magnetic network lanes, (iii) four of
  the jetlet-like events stem from sites of flux cancelation between
  majority-polarity network flux and merging minority-polarity flux, and
  (iv) four of the jetlet-like events show brightenings at their bases
  reminiscent of the base brightenings in coronal jets. The average
  spire length of the six jetlet-like events (9000 ± 3000 km) is three
  times shorter than that for IRIS jetlets (27,000 ± 8000 km). While
  not ruling out other generation mechanisms, the observations suggest
  that at least four of these events may be miniature versions of both
  larger-scale coronal jets that are driven by minifilament eruptions
  and still-larger-scale solar eruptions that are driven by filament
  eruptions. Therefore, we propose that our Hi-C events are driven by
  the eruption of a tiny sheared-field flux rope, and that the flux rope
  field is built and triggered to erupt by flux cancelation.

---------------------------------------------------------
Title: Cradle-to-Grave Evolution and Explosiveness of the Magnetic
    Field from Bipolar Ephemeral Active Regions (BEARs) in Solar
    Coronal Holes
Authors: Panesar, N. K.; Nagib, C.; Moore, R. L.; Sterling, A. C.
2019AGUFMSH11D3386P    Altcode:
  We report on the entire magnetic evolution and history of
  magnetic-explosion eruption production of each of 7 bipolar
  ephemeral active regions (BEARs) observed in on-disk coronal holes
  in line-of-sight magnetograms and in coronal EUV images. One of
  these BEARs made no eruptions. The other 6 BEARs together display
  three kinds of magnetic-explosion eruptions: (1) blowout eruptions
  (eruptions that make a wide-spire blowout jet), (2) partially-confined
  eruptions (eruptions that make a narrow-spire standard jet), (3)
  confined eruptions (eruptions that make no jet, i.e., make only a
  spireless EUV microflare). The 7 BEARs are a subset of a set of 60
  random coronal-hole BEARs that were observed from the advent to the
  final dissolution of the BEAR's minority-polarity magnetic flux. The
  emergence phase (time interval from advent to maximum minority flux)
  for the 60 BEARs had been previously visually estimated using the
  magnetograms, to find if magnetic-explosion eruption events commonly
  occur inside a BEAR's emerging magnetic field (as had been assumed by
  Moore et al 2010, ApJ 720:757). That inspection found no inside eruption
  during the estimated emergence phase of any of the 60 BEARs. In this new
  work, for each of the 7 BEARs, we obtain a more reliable determination
  of when the emergence phase ended by finding the time of the BEAR's
  maximum minority flux from a time plot of the BEAR's minority flux
  measured from the magnetograms. These plots show: (1) none of the 7
  BEARs had an inside eruption while the BEAR was emerging, and (2)
  for these 7 BEARs, the visually-estimated emergence end time was
  never more than 6 hours before the measured time of maximum minority
  flux. Of the 60 BEARs, in only 6 was there an inside eruption within
  6 hours after the visually-estimated end of emergence. The above two
  results for the 7 BEARs, together with the previous visual inspection
  of the 60 BEARs, support that a great majority (at least 90%) of the
  explosive magnetic fields from BEARs in coronal holes are prepared
  and triggered to explode by magnetic flux cancellation, and that
  such flux cancellation seldom occurs inside an emerging BEAR. The
  visual inspection of the magnetograms of the 60 BEARs showed that the
  pre-eruption flux cancellation was either on the outside of the BEAR
  during or after the BEAR's emergence or on the inside of the BEAR
  after the BEAR's emergence.

---------------------------------------------------------
Title: Onset of the Magnetic Explosion in On-disk Solar Coronal Jets
Authors: Panesar, N. K.; Moore, R. L.; Sterling, A. C.
2019AGUFMSH11D3384P    Altcode:
  In our recent studies of ~10 quiet region and ~13 coronal hole coronal,
  we found that flux cancelation is the fundamental process in the
  buildup and triggering of the minifilament eruption that drives the
  production of the jet. Here, we investigate the onset and growth of
  the ten on-disk quiet region jets, using EUV images from SDO/AIA and
  magnetograms from SDO/HMI. We find that: (i) in all ten events the
  minifilament starts to rise at or before the onset of the signature
  of internal or external reconnection; (ii) in two out of ten jets
  brightening from the external reconnection starts at the same time as
  the slow rise of the minifilament and (iii) in six out of ten jets
  brightening from the internal reconnection starts before the start
  of the brightening from external reconnection. These observations
  show that the magnetic explosion in coronal jets begins in the same
  way as the magnetic explosion in filament eruptions that make solar
  flares and coronal mass ejections (CMEs). Our results indicate (1) that
  coronal jets are miniature versions of CME-producing eruptions and flux
  cancelation is the fundamental process that builds and triggers both
  the small-scale and the large-scale eruptions, and (2) that, contrary to
  the view of Moore et al (2018), the current sheet at which the external
  reconnection occurs in coronal jets usually starts to form at or after
  the onset of (and as a result of) the slow rise of the minifilament
  flux-rope eruption, and so is seldom of appreciable size before the
  onset of the slow rise of the minifilament flux-rope eruption.

---------------------------------------------------------
Title: Further Evidence for Magnetic Flux Cancelation as the Build-up
    and Trigger Mechanism for Eruptions in Isolated Solar Active Regions
Authors: Sterling, A. C.; Buell, A.; Moore, R. L.; Falconer, D. A.
2019AGUFMSH11D3388S    Altcode:
  We examine the magnetic evolution of three eruption-producing solar
  active regions (ARs), one each from 2013, 2014, and 2017, using data
  from SDO HMI and AIA. Each of the ARs is relatively small, so that
  we can follow its entire development during a single disk passage,
  from birth by emergence through the time of the respective eruptions;
  the first-, second-, and third-born respectively lived 3, 6.5, and 3
  days before eruption. Each AR was relatively isolated, with minimal
  interaction with surrounding ARs, allowing us to study each AR as an
  approximately isolated system. CMEs resulted from eruptions in the
  first two ARs, while the third AR's eruption was smaller and appeared
  confined. In each AR, the eruption was seated on an interval of the AR's
  magnetic polarity inversion line (neutral line) where opposite-polarity
  flux was merging together and undergoing apparent cancelation. Our
  results, together with an earlier pilot study of two ARs by Sterling
  et al. (2018), and along with recent studies of solar coronal jets,
  support the view that the magnetic field that explodes to produce
  solar eruptions of size scales ranging from jets to CMEs are usually
  built and triggered by flux cancelation along a sharp neutral line.

---------------------------------------------------------
Title: Generation of solar spicules and subsequent atmospheric heating
Authors: Samanta, Tanmoy; Tian, Hui; Yurchyshyn, Vasyl; Peter, Hardi;
   Cao, Wenda; Sterling, Alphonse; Erdélyi, Robertus; Ahn, Kwangsu;
   Feng, Song; Utz, Dominik; Banerjee, Dipankar; Chen, Yajie
2019Sci...366..890S    Altcode: 2020arXiv200602571S
  Spicules are rapidly evolving fine-scale jets of magnetized plasma in
  the solar chromosphere. It remains unclear how these prevalent jets
  originate from the solar surface and what role they play in heating
  the solar atmosphere. Using the Goode Solar Telescope at the Big Bear
  Solar Observatory, we observed spicules emerging within minutes of the
  appearance of opposite-polarity magnetic flux around dominant-polarity
  magnetic field concentrations. Data from the Solar Dynamics Observatory
  showed subsequent heating of the adjacent corona. The dynamic
  interaction of magnetic fields (likely due to magnetic reconnection)
  in the partially ionized lower solar atmosphere appears to generate
  these spicules and heat the upper solar atmosphere.

---------------------------------------------------------
Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
   Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
   David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
   Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
   Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
   Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
   Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
   Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
   Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
   Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
   Peter R.
2019PASJ...71R...1H    Altcode:
  Hinode is Japan's third solar mission following Hinotori (1981-1982)
  and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
  operation currently. Hinode carries three instruments: the Solar Optical
  Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
  instruments were built under international collaboration with the
  National Aeronautics and Space Administration and the UK Science and
  Technology Facilities Council, and its operation has been contributed
  to by the European Space Agency and the Norwegian Space Center. After
  describing the satellite operations and giving a performance evaluation
  of the three instruments, reviews are presented on major scientific
  discoveries by Hinode in the first eleven years (one solar cycle long)
  of its operation. This review article concludes with future prospects
  for solar physics research based on the achievements of Hinode.

---------------------------------------------------------
Title: Magnetic Flux Cancellation as the Trigger Mechanism of Solar
    Coronal Jets
Authors: McGlasson, Riley A.; Panesar, Navdeep K.; Sterling, Alphonse
   C.; Moore, Ronald L.
2019ApJ...882...16M    Altcode: 2019arXiv190606452M
  Coronal jets are transient narrow features in the solar corona that
  originate from all regions of the solar disk: active regions, quiet Sun,
  and coronal holes. Recent studies indicate that at least some coronal
  jets in quiet regions and coronal holes are driven by the eruption of a
  minifilament following flux cancellation at a magnetic neutral line. We
  have tested the veracity of that view by examining 60 random jets in
  quiet regions and coronal holes using multithermal (304, 171, 193, and
  211 Å) extreme ultraviolet images from the Solar Dynamics Observatory
  (SDO)/Atmospheric Imaging Assembly and line-of-sight magnetograms from
  the SDO/Helioseismic and Magnetic Imager. By examining the structure
  and changes in the magnetic field before, during, and after jet onset,
  we found that 85% of these jets resulted from a minifilament eruption
  triggered by flux cancellation at the neutral line. The 60 jets have
  a mean base diameter of 8800 ± 3100 km and a mean duration of 9 ±
  3.6 minutes. These observations confirm that minifilament eruption
  is the driver and magnetic flux cancellation is the primary trigger
  mechanism for most coronal hole and quiet region coronal jets.

---------------------------------------------------------
Title: Hi-C2.1 Observations of Solar Jetlets at Sites of Flux
    Cancelation
Authors: Panesar, Navdeep; Sterling, Alphonse C.; Moore, Ronald L.
2019AAS...23411701P    Altcode:
  Solar jets of all sizes are magnetically channeled narrow eruptive
  events; the larger ones are often observed in the solar corona in EUV
  and coronal X-ray images. Recent observations show that the buildup
  and triggering of the minifilament eruptions that drive coronal jets
  result from magnetic flux cancelation under the minifilament, at the
  neutral line between merging majority-polarity and minority-polarity
  magnetic flux patches. Here we investigate the magnetic setting
  of six on-disk small-scale jet-like/spicule-like eruptions (also
  known as jetlets) by using high resolution 172A images from the
  High-resolution Coronal Imager (Hi-C2.1) and EUV images from Solar
  Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and
  line-of-sight magnetograms from SDO/Helioseismic and Magnetic Imager
  (HMI). From magnetograms co-aligned with the Hi-C and AIA images, we
  find that (i) these jetlets are rooted at edges of magnetic network
  lanes (ii) some jetlets stem from sites of flux cancelation between
  merging majority-polarity and minority-polarity flux patches (iii)
  some jetlets show faint brightenings at their bases reminiscent of
  the base brightenings in coronal jets. Based on the 6 Hi-C jetlets
  that we have examined in detail and our previous observations of 30
  coronal jets in quiet regions and coronal holes, we infer that flux
  cancelation is the essential process in the buildup and triggering of
  jetlets. Our observations suggest that network jetlets result from
  small-scale eruptions that are analogs of both larger-scale coronal
  jet minifilament eruptions and the still-larger-scale eruptions that
  make major CMEs. This work was supported by the NASA/MSFC NPP program
  and the NASA HGI Program.

---------------------------------------------------------
Title: A Two-Sided-Loop X-Ray Solar Coronal Jet and a Sudden
    Photospheric Magnetic-field Change, Both Driven by a Minifilament
    Eruption
Authors: Sterling, Alphonse C.; Harra, Louise; Moore, Ronald L.;
   Falconer, David
2019AAS...23431701S    Altcode:
  Most of the commonly discussed solar coronal jets are of the type
  consisting of a single spire extending approximately vertically from
  near the solar surface into the corona. Recent research shows that
  eruption of a miniature filament (minifilament) drives at least many
  such single-spire jets, and concurrently generates a miniflare at the
  eruption site. A different type of coronal jet, identified in X-ray
  images during the Yohkoh era, are two-sided-loop jets, which extend
  from a central excitation location in opposite directions, along two
  opposite low-lying coronal loops that are more-or-less horizontal
  to the surface. We observe such a two-sided-loop jet from the edge
  of active region (AR) 12473, using data from Hinode XRT and EIS, and
  SDO AIA and HMI. Similar to single-spire jets, this two-sided-loop jet
  results from eruption of a minifilament, which accelerates to over 140
  km/s before abruptly stopping upon striking overlying nearly-horizontal
  magnetic field at ∼30,000 km altitude and producing the two-sided-loop
  jet via interchange reconnection. Analysis of EIS raster scans show
  that a hot brightening, consistent with a small flare, develops in
  the aftermath of the eruption, and that Doppler motions (∼40 km/s)
  occur near the jet-formation region. As with many single-spire jets, the
  trigger of the eruption here is apparently magnetic flux cancelation,
  which occurs at a rate of ∼4×10<SUP>18</SUP> Mx/hr, comparable to the
  rate observed in some single-spire AR jets. An apparent increase in the
  (line-of-sight) flux occurs within minutes of onset of the minifilament
  eruption, consistent with the apparent increase being due to a rapid
  reconfiguration of low-lying magnetic field during the minifilament
  eruption. Details appear in Sterling et al. (2019, ApJ, 871, 220).

---------------------------------------------------------
Title: A Two-sided Loop X-Ray Solar Coronal Jet Driven by a
    Minifilament Eruption
Authors: Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.;
   Falconer, David A.
2019ApJ...871..220S    Altcode: 2018arXiv181105557S
  Most of the commonly discussed solar coronal jets are the type that
  consist of a single spire extending approximately vertically from
  near the solar surface into the corona. Recent research supports
  that eruption of a miniature filament (minifilament) drives many such
  single-spire jets and concurrently generates a miniflare at the eruption
  site. A different type of coronal jet, identified in X-ray images during
  the Yohkoh era, are two-sided loop jets, which extend from a central
  excitation location in opposite directions, along low-lying coronal
  loops that are more-or-less horizontal to the surface. We observe
  such a two-sided loop jet from the edge of active region (AR) 12473,
  using data from Hinode X-Ray Telescope (XRT) and Extreme Ultraviolet
  Imaging Spectrometer (EIS), and from Solar Dynamics Observatory’s
  (SDO) Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic
  Imager (HMI). Similar to single-spire jets, this two-sided loop jet
  results from eruption of a minifilament, which accelerates to over 140
  km s<SUP>-1</SUP> before abruptly stopping after striking an overlying
  nearly horizontal-loop field at ∼30,000 km in altitude and producing
  the two-sided loop jet. An analysis of EIS raster scans shows that a hot
  brightening, consistent with a small flare, develops in the aftermath
  of the eruption, and that Doppler motions (∼40 km s<SUP>-1</SUP>)
  occur near the jet formation region. As with many single-spire jets, the
  magnetic trigger here is apparently flux cancelation, which occurs at
  a rate of ∼4 × 10<SUP>18</SUP> Mx hr<SUP>-1</SUP>, broadly similar
  to the rates observed in some single-spire quiet-Sun and AR jets. An
  apparent increase in the (line-of-sight) flux occurs within minutes of
  the onset of the minifilament eruption, consistent with the apparent
  increase being due to a rapid reconfiguration of low-lying fields
  during and soon after the minifilament-eruption onset.

---------------------------------------------------------
Title: Evidence of Twisting and Mixed-polarity Solar Photospheric
Magnetic Field in Large Penumbral Jets: IRIS and Hinode Observations
Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; De Pontieu, Bart;
   Tarbell, Theodore D.; Panesar, Navdeep K.; Winebarger, Amy R.;
   Sterling, Alphonse C.
2018ApJ...869..147T    Altcode: 2018arXiv181109554T
  A recent study using Hinode (Solar Optical Telescope/Filtergraph
  [SOT/FG]) data of a sunspot revealed some unusually large penumbral
  jets that often repeatedly occurred at the same locations in the
  penumbra, namely, at the tail of a penumbral filament or where the
  tails of multiple penumbral filaments converged. These locations had
  obvious photospheric mixed-polarity magnetic flux in Na I 5896 Stokes-V
  images obtained with SOT/FG. Several other recent investigations have
  found that extreme-ultraviolet (EUV)/X-ray coronal jets in quiet-Sun
  regions (QRs), in coronal holes (CHs), and near active regions (ARs)
  have obvious mixed-polarity fluxes at their base, and that magnetic
  flux cancellation prepares and triggers a minifilament flux-rope
  eruption that drives the jet. Typical QR, CH, and AR coronal jets are
  up to 100 times bigger than large penumbral jets, and in EUV/X-ray
  images they show a clear twisting motion in their spires. Here,
  using Interface Region Imaging Spectrograph (IRIS) Mg II k λ2796 SJ
  images and spectra in the penumbrae of two sunspots, we characterize
  large penumbral jets. We find redshift and blueshift next to each
  other across several large penumbral jets, and we interpret these as
  untwisting of the magnetic field in the jet spire. Using Hinode/SOT
  (FG and SP) data, we also find mixed-polarity magnetic flux at the
  base of these jets. Because large penumbral jets have a mixed-polarity
  field at their base and have a twisting motion in their spires, they
  might be driven the same way as QR, CH, and AR coronal jets.

---------------------------------------------------------
Title: IRIS and SDO Observations of Solar Jetlets Resulting from
    Network-edge Flux Cancelation
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
   Tiwari, Sanjiv K.; De Pontieu, Bart; Norton, Aimee A.
2018ApJ...868L..27P    Altcode: 2018arXiv181104314P
  Recent observations show that the buildup and triggering of minifilament
  eruptions that drive coronal jets result from magnetic flux cancelation
  at the neutral line between merging majority- and minority-polarity
  magnetic flux patches. We investigate the magnetic setting of 10
  on-disk small-scale UV/EUV jets (jetlets, smaller than coronal X-ray
  jets but larger than chromospheric spicules) in a coronal hole by using
  IRIS UV images and SDO/AIA EUV images and line-of-sight magnetograms
  from SDO/HMI. We observe recurring jetlets at the edges of magnetic
  network flux lanes in the coronal hole. From magnetograms coaligned
  with the IRIS and AIA images, we find, clearly visible in nine cases,
  that the jetlets stem from sites of flux cancelation proceeding at
  an average rate of ∼1.5 × 10<SUP>18</SUP> Mx hr<SUP>-1</SUP>, and
  show brightenings at their bases reminiscent of the base brightenings
  in larger-scale coronal jets. We find that jetlets happen at many
  locations along the edges of network lanes (not limited to the base
  of plumes) with average lifetimes of 3 minutes and speeds of 70 km
  s<SUP>-1</SUP>. The average jetlet-base width (4000 km) is three
  to four times smaller than for coronal jets (∼18,000 km). Based on
  these observations of 10 obvious jetlets, and our previous observations
  of larger-scale coronal jets in quiet regions and coronal holes, we
  infer that flux cancelation is an essential process in the buildup and
  triggering of jetlets. Our observations suggest that network jetlet
  eruptions might be small-scale analogs of both larger-scale coronal
  jets and the still-larger-scale eruptions producing CMEs.

---------------------------------------------------------
Title: Coronal Jets, and the Jet-CME Connection
Authors: Sterling, Alphonse C.
2018JPhCS1100a2024S    Altcode: 2019arXiv191202808S
  Solar coronal jets have been observed in detail since the early
  1990s. While it is clear that these jets are magnetically driven, the
  details of the driving process has recently been updated. Previously
  it was suspected that the jets were a consequence of magnetic flux
  emergence interacting with ambient coronal field. New evidence however
  indicates that often the direct driver of the jets is erupting field,
  often carrying cool material (a “minifilament”), that undergoes
  interchange magnetic reconnection with preexisting field ([1]). More
  recent work indicates that the trigger for eruption of the minifilament
  is frequently cancelation of photospheric magnetic fields at the base
  of the minifilament. These erupting minifilaments are analogous to the
  better-known larger-scale filament eruptions that produce solar flares
  and, frequently, coronal mass ejections (CMEs). A subset of coronal
  jets drive narrow “white-light jets,” which are very narrow CME-like
  features, and apparently a few jets can drive wider, although relatively
  weak, “streamer-puff” CMEs. Here we summarize these recent findings.

---------------------------------------------------------
Title: Magnetic Flux Cancelation as the Buildup and Trigger Mechanism
    for CME-producing Eruptions in Two Small Active Regions
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Panesar, Navdeep K.
2018ApJ...864...68S    Altcode: 2018arXiv180703237S
  We follow two small, magnetically isolated coronal mass ejection
  (CME)-producing solar active regions (ARs) from the time of their
  emergence until several days later, when their core regions erupt to
  produce the CMEs. In both cases, magnetograms show: (a) following
  an initial period where the poles of the emerging regions separate
  from each other, the poles then reverse direction and start to retract
  inward; (b) during the retraction period, flux cancelation occurs along
  the main neutral line of the regions; (c) this cancelation builds
  the sheared core field/flux rope that eventually erupts to make the
  CME. In the two cases, respectively 30% and 50% of the maximum flux
  of the region cancels prior to the eruption. Recent studies indicate
  that solar coronal jets frequently result from small-scale filament
  eruptions, with those “minifilament” eruptions also being built up
  and triggered by cancelation of magnetic flux. Together, the small-AR
  eruptions here and the coronal jet results suggest that isolated bipolar
  regions tend to erupt when some threshold fraction, perhaps in the
  range of 50%, of the region's maximum flux has canceled. Our observed
  erupting filaments/flux ropes form at sites of flux cancelation, in
  agreement with previous observations. Thus, the recent finding that
  minifilaments that erupt to form jets also form via flux cancelation
  is further evidence that minifilaments are small-scale versions of
  the long-studied full-sized filaments.

---------------------------------------------------------
Title: Flux Cancelation as the Trigger of Coronal Hole Jet Eruptions
Authors: Panesar, Navdeep Kaur; Sterling, Alphonse C.; Moore,
   Ronald Lee
2018tess.conf40806P    Altcode:
  Coronal jets are magnetically channeled narrow eruptions often observed
  in the solar corona. Recent observations show that coronal jets are
  driven by the eruption of a small-scale filament (minifilament). Here
  we investigate the triggering mechanism of jet-driving minifilament
  eruptions in coronal holes, by using X-ray images from Hinode, EUV
  images from SDO/AIA, and line of sight magnetograms from SDO/HMI. We
  study 13 on-disk randomly selected coronal hole jets, and track
  the evolution of the jet-base. In each case we find that there is a
  minifilament present in the jet-base region prior to jet eruption. The
  minifilaments reside above a neutral line between majority-polarity
  and minority-polarity magnetic flux patches. HMI magnetograms
  show continuous flux cancelation at the neutral line between the
  opposite polarity flux patches. Persistent flux cancelation eventually
  destabilizes the field that holds the minifilament plasma. The erupting
  field reconnects with the neighboring far-reaching field and produces
  the jet spire. From our study, we conclude that flux cancelation is
  the fundamental process for triggering coronal hole jets. Other recent
  studies show that jets in quiet regions and active regions also are
  accompanied by flux cancelation at minifilament neutral lines (Panesar
  et al. 2016b, Sterling et al. 2017); therefore the same fundamental
  process - namely, magnetic flux cancelation - triggers at least many
  coronal jets in all regions of the Sun.

---------------------------------------------------------
Title: Solar Explosions Imager (SEIM): A Next-Generation
    High-Resolution and High-Cadence EUV Telescope for Unraveling Eruptive
    Solar Features
Authors: Sterling, Alphonse C.; Moore, Ronald Lee; Winebarger, Amy R.
2018tess.conf11002S    Altcode:
  We present a skeletal proposal for a space-based EUV telescope to
  fly on the Next Generation Solar Physics Mission (NGSPM). A primary
  motivation is to unravel physical processes leading to small-scale
  solar features, such as solar coronal jets, and the processes leading
  to larger eruptions as well. Recent evidence suggests that jets
  result from eruptions of small-scale filaments (size scale: ~1—a
  few arcsec), analogous to larger filament eruptions that drive CMEs,
  and it is plausible that the even-smaller-scale spicules (∼0′′.1)
  operate in a similar fashion. Therefore an instrument planned around
  the concept of observing jet features, but with the highest practical
  resolution and cadence, would be valuable for observing various erupting
  solar features on many size and time scales. Resolution and cadence
  should be comparable to or better than that of Hi-C, i.e. ≤0”.1
  pixels and ≤10 s cadence. While no single instrument could span the
  entire needed data-set space needed to address fully these questions,
  the proposed instrument would complement first-rate instrumentation
  (namely, DKIST) expected to be in operation around the time of expected
  deployment. If resources permit, the proposed EUV instrument could
  be supplemented with additional instrumentation, or such additional
  instrumentation could be proposed as (a) separate effort(s). Especially
  complementary would be a photospheric magnetograph having ≤0”.1
  pixels, ≤1-minute cadence, line-of-sight-field sensitivity of ≤10
  G, and few-arc-minute FOV. (The SEIM concept has been presented as a
  WhitePaper with the same title to the NGSPM planning committee.)

---------------------------------------------------------
Title: Onset of the Magnetic Explosion in Solar Polar X-Ray Jets
Authors: Moore, Ronald Lee; Sterling, Alphonse C.; Panesar, Navdeep
   Kaur
2018tess.conf30598M    Altcode:
  We follow up on the Sterling et al (2015, Nature, 523, 437) discovery
  that nearly all solar polar X-ray jets are made by an explosive
  eruption of closed magnetic field carrying a miniature cool-plasma
  filament in its core. In the same X-ray and EUV movies used by Sterling
  et al (2015), we examine the onset and growth of the driving magnetic
  explosion in 15 of the 20 jets that they studied. We find evidence that:
  (1) in a large majority of polar X-ray jets, the runaway internal
  tether-cutting reconnection under the erupting minifilament flux rope
  starts after both the minifilament's rise and the spire-producing
  breakout reconnection have started; and (2) in a large minority,
  (a) before the eruption starts there is a current sheet between the
  explosive closed field and the ambient open field, and (b) the eruption
  starts with breakout reconnection at that current sheet. The observed
  sequence of events as the eruptions start and grow support the idea
  that the magnetic explosions that make polar X-ray jets work the same
  way as the much larger magnetic explosions that make a flare and coronal
  mass ejection (CME). That idea, and recent observations indicating that
  magnetic flux cancelation is the fundamental process that builds the
  field in and around the pre-jet minifilament and triggers that field's
  jet-driving explosion, together suggest that flux cancelation inside
  the magnetic arcade that explodes in a flare/CME eruption is usually
  the fundamental process that builds the explosive field in the core
  of the arcade and triggers that field's explosion. <P />This work
  was funded by the Heliophysics Division of NASA's Science Mission
  Directorate through the Living With a Star Science Program and the
  Heliophysics Guest Investigators Program.

---------------------------------------------------------
Title: Observations of Large Penumbral Jets from IRIS and Hinode
Authors: Tiwari, Sanjiv K.; Moore, Ronald Lee; De Pontieu, Bart;
   Tarbell, Theodore D.; Panesar, Navdeep Kaur; Winebarger, Amy R.;
   Sterling, Alphonse C.
2018tess.conf40807T    Altcode:
  Recent observations from Hinode (SOT/FG) revealed the presence of
  large penumbral jets (widths ≥ 500 km, larger than normal penumbral
  microjets, which have widths &lt; 400 km) repeatedly occurring at
  the same locations in a sunspot penumbra, at the tail of a penumbral
  filament or where the tails of several penumbral filaments apparently
  converge (Tiwari et al. 2016, ApJ). These locations were observed
  to have mixed-polarity flux in Stokes-V images from SOT/FG. Large
  penumbral jets displayed direct signatures in AIA 1600, 304, 171,
  and 193 channels; thus they were heated to at least transition region
  temperatures. Because large jets could not be detected in AIA 94 Å,
  whether they had any coronal-temperature plasma remains unclear. In
  the present work, for another sunspot, we use IRIS Mg II k 2796
  slit jaw images and spectra and magnetograms from Hinode SOT/FG and
  SOT/SP to examine: whether penumbral jets spin, similar to spicules
  and coronal jets in the quiet Sun and coronal holes; whether they stem
  from mixed-polarity flux; and whether they produce discernible coronal
  emission, especially in AIA 94 Å images.

---------------------------------------------------------
Title: Onset of the Magnetic Explosion in Solar Polar Coronal
    X-Ray Jets
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Panesar, Navdeep K.
2018ApJ...859....3M    Altcode: 2018arXiv180512182M
  We follow up on the Sterling et al. discovery that nearly all polar
  coronal X-ray jets are made by an explosive eruption of a closed
  magnetic field carrying a miniature filament in its core. In the same
  X-ray and EUV movies used by Sterling et al., we examine the onset
  and growth of the driving magnetic explosion in 15 of the 20 jets
  that they studied. We find evidence that (1) in a large majority of
  polar X-ray jets, the runaway internal/tether-cutting reconnection
  under the erupting minifilament flux rope starts after both the
  minifilament’s rise and the spire-producing external/breakout
  reconnection have started; and (2) in a large minority, (a) before
  the eruption starts, there is a current sheet between the explosive
  closed field and the ambient open field, and (b) the eruption starts
  with breakout reconnection at that current sheet. The variety of
  event sequences in the eruptions supports the idea that the magnetic
  explosions that make polar X-ray jets work the same way as the much
  larger magnetic explosions that make a flare and coronal mass ejection
  (CME). That idea and recent observations indicating that magnetic
  flux cancellation is the fundamental process that builds the field
  in and around the pre-jet minifilament and triggers that field’s
  jet-driving explosion together suggest that flux cancellation inside
  the magnetic arcade that explodes in a flare/CME eruption is usually
  the fundamental process that builds the explosive field in the core
  of the arcade and triggers that field’s explosion.

---------------------------------------------------------
Title: Magnetic Flux Cancelation as the Trigger of Solar Coronal
    Jets in Coronal Holes
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.
2018ApJ...853..189P    Altcode: 2018arXiv180105344P
  We investigate in detail the magnetic cause of minifilament eruptions
  that drive coronal-hole jets. We study 13 random on-disk coronal-hole
  jet eruptions, using high-resolution X-ray images from the Hinode/X-ray
  telescope(XRT), EUV images from the Solar Dynamics Observatory
  (SDO)/Atmospheric Imaging Assembly (AIA), and magnetograms from the
  SDO/Helioseismic and Magnetic Imager (HMI). For all 13 events, we track
  the evolution of the jet-base region and find that a minifilament of
  cool (transition-region-temperature) plasma is present prior to each jet
  eruption. HMI magnetograms show that the minifilaments reside along a
  magnetic neutral line between majority-polarity and minority-polarity
  magnetic flux patches. These patches converge and cancel with each
  other, with an average cancelation rate of ∼0.6 × 10<SUP>18</SUP>
  Mx hr<SUP>-1</SUP> for all 13 jets. Persistent flux cancelation at
  the neutral line eventually destabilizes the minifilament field, which
  erupts outward and produces the jet spire. Thus, we find that all 13
  coronal-hole-jet-driving minifilament eruptions are triggered by flux
  cancelation at the neutral line. These results are in agreement with
  our recent findings for quiet-region jets, where flux cancelation at
  the underlying neutral line triggers the minifilament eruption that
  drives each jet. Thus, from that study of quiet-Sun jets and this
  study of coronal-hole jets, we conclude that flux cancelation is the
  main candidate for triggering quiet-region and coronal-hole jets.

---------------------------------------------------------
Title: A Microfilament-Eruption Mechanism for Solar Spicules
Authors: Sterling, A. C.; Moore, R. L.
2017AGUFMSH43A2791S    Altcode:
  Recent studies indicate that solar coronal jets result from eruption
  of small-scale filaments, or "minifilaments" (Sterling et al. 2015,
  Nature, 523, 437; Panesar et al. ApJL, 832L, 7). In many aspects,
  these coronal jets appear to be small-scale versions of long-recognized
  large-scale solar eruptions that are often accompanied by eruption of
  a large-scale filament and that produce solar flares and coronal mass
  ejections (CMEs). In coronal jets, a jet-base bright point (JBP) that
  is often observed to accompany the jet and that sits on the magnetic
  neutral line from which the minifilament erupts, corresponds to the
  solar flare of larger-scale eruptions that occurs at the neutral line
  from which the large-scale filament erupts. Large-scale eruptions are
  relatively uncommon ( 1/day) and occur with relatively large-scale
  erupting filaments ( 10^5 km long). Coronal jets are more common (&gt;
  100s/day), but occur from erupting minifilaments of smaller size ( 10^4
  km long). It is known that solar spicules are much more frequent (many
  millions/day) than coronal jets. Just as coronal jets are small-scale
  versions of large-scale eruptions, here we suggest that solar spicules
  might in turn be small-scale versions of coronal jets; we postulate that
  the spicules are produced by eruptions of “microfilaments” of length
  comparable to the width of observed spicules ( 300 km). A plot of the
  estimated number of the three respective phenomena (flares/CMEs, coronal
  jets, and spicules) occurring on the Sun at a given time, against the
  average sizes of erupting filaments, minifilaments, and the putative
  microfilaments, results in a size distribution that can be fit with a
  power-law within the estimated uncertainties. The counterparts of the
  flares of large-scale eruptions and the JBPs of jets might be weak,
  pervasive, transient brightenings observed in Hinode/CaII images, and
  the production of spicules by microfilament eruptions might explain why
  spicules spin, as do coronal jets. The expected small-scale neutral
  lines from which the microfilaments would be expected to erupt would
  be difficult to detect reliably with current instrumentation, but
  might be apparent with instrumentation of the near future. A summary
  of this work appears in Sterling and Moore 2016, ApJL, 829, L9.

---------------------------------------------------------
Title: Dynamic Solar Coronal Jets occurring in a Near-Limb Active
    Region
Authors: Velasquez, J.; Sterling, A. C.; Falconer, D. A.; Moore,
   R. L.; Panesar, N. K.
2017AGUFMSH43A2792V    Altcode:
  Coronal Jets are long, narrow columns of plasma ejected from the lower
  solar atmosphere into the corona and observed at coronal wavelengths. In
  this study, we observe a series of coronal jets occurring in NOAA
  active region (AR) 12473 on 2015 December 30. At that time the AR was
  approaching the Sun's west limb, allowing for observation of the jets in
  profile, contrasting with our recent studies of on-disk active region
  jets (Sterling et al. 2016, ApJ, 821, 100; and 2017, ApJ, 844, 28). We
  observe the jets using X-ray images from Hinode's X-Ray Telescope
  (XRT) and EUV images from the Solar Dynamic Observatory's (SDO)
  Atmospheric Imaging Assembly (AIA). Here, we investigate the dynamic
  trajectories of about 9 jets, by measuring the distance between the jet
  base and the leading edge of the erupting jet (i.e., the jet length)
  as a function of time, when observed in 304 Angstrom AIA images. All
  of the selected jets are concurrently visible in X-rays, and thus we
  are measuring properties of the chromospheric-transition region "cool
  component" of X-ray jets; in most cases, the appearance of the jets,
  such as the length of their spire, differs substantially between the
  X-ray and EUV 304 Angstrom images. For our selection of jets, we find
  that in the 304 Angstrom images many of them spin as they extend. Most
  of those in our selection do not make coronal mass ejections (CMEs);
  on average our jets have outward velocities of about 126 km/s, average
  maximum lengths of 84,000 km, and average lifetimes of 38 min. These
  values fall in the range of outward velocities and lifetimes found by
  Panesar et al. (2016, ApJ, 822, L23) for active-region 304 Angstrom jets
  that did not make CMEs. These values are also comparable to those found
  by Moschou et al. (2013, Solar Phys, 284, 427) for a selection of quiet
  Sun and coronal hole 304 Angstrom jets. One of our selected jets did
  make a CME, and it has outward velocity of about 240 km/s, consistent
  with the Panesar et al. (2016) results for CME-producing jets.

---------------------------------------------------------
Title: Magnetic Flux Cancellation as the Trigger of Solar Coronal Jets
Authors: McGlasson, R.; Panesar, N. K.; Sterling, A. C.; Moore, R. L.
2017AGUFMSH43A2796M    Altcode:
  Coronal jets are narrow eruptions in the solar corona, and are often
  observed in extreme ultraviolet (EUV) and X-ray images. They occur
  everywhere on the solar disk: in active regions, quiet regions,
  and coronal holes (Raouafi et al. 2016). Recent studies indicate
  that most coronal jets in quiet regions and coronal holes are driven
  by the eruption of a minifilament (Sterling et al. 2015), and that
  this eruption follows flux cancellation at the magnetic neutral line
  under the pre-eruption minifilament (Panesar et al. 2016). We confirm
  this picture for a large sample of jets in quiet regions and coronal
  holes using multithermal (304 Å 171 Å, 193 Å, and 211 Å) extreme
  ultraviolet (EUV) images from the Solar Dynamics Observatory (SDO)
  /Atmospheric Imaging Assembly (AIA) and line-of-sight magnetograms from
  the SDO /Helioseismic and Magnetic Imager (HMI). We report observations
  of 60 randomly selected jet eruptions. We have analyzed the magnetic
  cause of these eruptions and measured the base size and the duration of
  each jet using routines in SolarSoft IDL. By examining the evolutionary
  changes in the magnetic field before, during, and after jet eruption,
  we found that each of these jets resulted from minifilament eruption
  triggered by flux cancellation at the neutral line. In agreement
  with the above studies, we found our jets to have an average base
  diameter of 7600 ± 2700 km and an average duration of 9.0 ± 3.6
  minutes. These observations confirm that minifilament eruption is the
  driver and magnetic flux cancellation is the primary trigger mechanism
  for nearly all coronal hole and quiet region coronal jet eruptions.

---------------------------------------------------------
Title: Origin of Pre-Coronal-Jet Minifilaments: Flux Cancellation
Authors: Panesar, N. K.; Sterling, A. C.; Moore, R. L.
2017AGUFMSH41C..03P    Altcode:
  We recently investigated the triggering mechanism of ten quiet-region
  coronal jet eruptions and found that magnetic flux cancellation at the
  neutral line of minifilaments is the main cause of quiet-region jet
  eruptions (Panesar et al 2016). However, what leads to the formation
  of the pre-jet minifilaments remained unknown. In the present work,
  we study the longer-term evolution of the magnetic field that leads
  to the formation of pre-jet minifilaments by using SDO/AIA intensity
  images and concurrent line of sight SDO/HMI magnetograms. We find
  that each of the ten pre-jet minifilaments formed due to progressive
  flux cancellation between the minority-polarity and majority-polarity
  flux patches (with a minority-polarity flux loss of 10% - 40% prior
  to minifilament birth). Apparently, the flux cancellation between the
  opposite polarity flux patches builds a highly-sheared field at the
  magnetic neutral line, and that field holds the cool transition region
  minifilament plasma. Even after the formation of minifilaments, the
  flux continues to cancel, making the minifilament body more thick and
  prominent. Further flux cancellation between the opposite-flux patches
  leads to the minifilament eruption and a resulting jet. From these
  observations, we infer that flux cancellation is usually the process
  that builds up the sheared and twisted field in pre-jet minifilaments,
  and that triggers it to erupt and drive a jet.

---------------------------------------------------------
Title: Onset of a Large Ejective Solar Eruption from a Typical
    Coronal-jet-base Field Configuration
Authors: Joshi, Navin Chandra; Sterling, Alphonse C.; Moore, Ronald
   L.; Magara, Tetsuya; Moon, Yong-Jae
2017ApJ...845...26J    Altcode: 2017arXiv170609176J
  Utilizing multiwavelength observations and magnetic field data from
  the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly
  (AIA), SDO/Helioseismic and Magnetic Imager (HMI), the Geostationary
  Operational Environmental Satellite (GOES), and RHESSI, we investigate
  a large-scale ejective solar eruption of 2014 December 18 from active
  region NOAA 12241. This event produced a distinctive “three-ribbon”
  flare, having two parallel ribbons corresponding to the ribbons of a
  standard two-ribbon flare, and a larger-scale third quasi-circular
  ribbon offset from the other two. There are two components to this
  eruptive event. First, a flux rope forms above a strong-field polarity
  inversion line and erupts and grows as the parallel ribbons turn on,
  grow, and spread apart from that polarity inversion line; this evolution
  is consistent with the mechanism of tether-cutting reconnection for
  eruptions. Second, the eruption of the arcade that has the erupting
  flux rope in its core undergoes magnetic reconnection at the null
  point of a fan dome that envelops the erupting arcade, resulting
  in formation of the quasi-circular ribbon; this is consistent with
  the breakout reconnection mechanism for eruptions. We find that
  the parallel ribbons begin well before (∼12 minutes) the onset
  of the circular ribbon, indicating that tether-cutting reconnection
  (or a non-ideal MHD instability) initiated this event, rather than
  breakout reconnection. The overall setup for this large-scale eruption
  (diameter of the circular ribbon ∼10<SUP>5</SUP> km) is analogous to
  that of coronal jets (base size ∼10<SUP>4</SUP> km), many of which,
  according to recent findings, result from eruptions of small-scale
  “minifilaments.” Thus these findings confirm that eruptions of
  sheared-core magnetic arcades seated in fan-spine null-point magnetic
  topology happen on a wide range of size scales on the Sun.

---------------------------------------------------------
Title: Onset of the Magnetic Explosion in Solar Polar Coronal
    X-Ray Jets
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Panesar, Navdeep
2017SPD....4820006M    Altcode:
  We examine the onset of the driving magnetic explosion in 15 random
  polar coronal X-ray jets. Each eruption is observed in a coronal
  X-ray movie from Hinode and in a coronal EUV movie from Solar Dynamics
  Observatory. Contrary to the Sterling et al (2015, Nature, 523, 437)
  scenario for minifilament eruptions that drive polar coronal jets,
  these observations indicate: (1) in most polar coronal jets (a)
  the runaway internal tether-cutting reconnection under the erupting
  minifilament flux rope starts after the spire-producing breakout
  reconnection starts, not before it, and (b) aleady at eruption onset,
  there is a current sheet between the explosive closed magnetic field
  and ambient open field; and (2) the minifilament-eruption magnetic
  explosion often starts with the breakout reconnection of the outside
  of the magnetic arcade that carries the minifilament in its core. On
  the other hand, the diversity of the observed sequences of occurrence
  of events in the jet eruptions gives further credence to the Sterlling
  et al (2015, Nature, 523, 437) idea that the magnetic explosions that
  make a polar X-ray jet work the same way as the much larger magnetic
  explosions that make and flare and CME. We point out that this idea,
  and recent observations indicating that magnetic flux cancelation is
  the fundamental process that builds the field in and around pre-jet
  minifilaments and triggers the jet-driving magnetic explosion, together
  imply that usually flux cancelation inside the arcade that explodes
  in a flare/CME eruption is the fundamental process that builds the
  explosive field and triggers the explosion.This work was funded by the
  Heliophysics Division of NASA's Science Mission Directorate through
  its Living With a Star Targeted Research and Technology Program,
  its Heliophsyics Guest Investigators Program, and the Hinode Project.

---------------------------------------------------------
Title: Active Region Jets II: Triggering and Evolution of Violent Jets
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David;
   Panesar, Navdeep K.; Martinez, Francisco
2017SPD....4830403S    Altcode:
  We study a series of X-ray-bright, rapidly evolving active-region
  coronal jets outside the leading sunspot of AR 12259, using Hinode/XRT,
  SDO/AIA and HMI, and IRIS/SJ data. The detailed evolution of such
  rapidly evolving “violent” jets remained a mystery after our
  previous investigation of active region jets (Sterling et al. 2016,
  ApJ, 821, 100). The jets we investigate here erupt from three
  localized subregions, each containing a rapidly evolving (positive)
  minority-polarity magnetic-flux patch bathed in a (majority)
  negative-polarity magnetic-flux background. At least several of
  the jets begin with eruptions of what appear to be thin (thickness
  ∼&lt;2‧‧) miniature-filament (minifilament) “strands” from
  a magnetic neutral line where magnetic flux cancelation is ongoing,
  consistent with the magnetic configuration presented for coronal-hole
  jets in Sterling et al. (2015, Nature, 523, 437). For some jets strands
  are difficult/ impossible to detect, perhaps due to their thinness,
  obscuration by surrounding bright or dark features, or the absence
  of erupting cool-material minifilaments in those jets. Tracing
  in detail the flux evolution in one of the subregions, we find
  bursts of strong jetting occurring only during times of strong flux
  cancelation. Averaged over seven jetting episodes, the cancelation
  rate was ~1.5×10^19 Mx/hr. An average flux of ~5×10^18 Mx canceled
  prior to each episode, arguably building up ~10^28—10^29 ergs of
  free magnetic energy per jet. From these and previous observations,
  we infer that flux cancelation is the fundamental process responsible
  for the pre-eruption buildup and triggering of at least many jets in
  active regions, quiet regions, and coronal holes.

---------------------------------------------------------
Title: Flux Cancelation as the trigger of quiet-region coronal
    jet eruptions
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.
2017SPD....4830402P    Altcode:
  Coronal jets are frequent transient features on the Sun, observed
  in EUV and X-ray emissions. They occur in active regions, quiet
  Sun and coronal holes, and appear as a bright spire with base
  brightenings. Recent studies show that many coronal jets are driven by
  the eruption of a minifilament. Here we investigate the magnetic cause
  of jet-driving minifilament eruptions. We study ten randomly-found
  on-disk quiet-region coronal jets using SDO/AIA intensity images
  and SDO/HMI magnetograms. For all ten events, we track the evolution
  of the jet-base region and find that (a) a cool (transition-region
  temperature) minifilament is present prior to each jet eruption; (b)
  the pre-eruption minifilament resides above the polarity-inversion line
  between majority-polarity and minority-polarity magnetic flux patches;
  (c) the opposite-polarity flux patches converge and cancel with each
  other; (d) the ongoing cancelation between the majority-polarity and
  minority-polarity flux patches eventually destabilizes the field holding
  the minifilament to erupt outwards; (e) the envelope of the erupting
  field barges into ambient oppositely-directed far-reaching field and
  undergoes external reconnection (interchange reconnection); (f) the
  external reconnection opens the envelope field and the minifilament
  field inside, allowing reconnection-heated hot material and cool
  minifilament material to escape along the reconnected far-reaching
  field, producing the jet spire. In summary, we found that each of our
  ten jets resulted from a minifilament eruption during flux cancelation
  at the magnetic neutral line under the pre-eruption minifilament. These
  observations show that flux cancelation is usually the trigger of
  quiet-region coronal jet eruptions.

---------------------------------------------------------
Title: Magnetic Flux Cancellation as the Origin of Solar Quiet-region
    Pre-jet Minifilaments
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.
2017ApJ...844..131P    Altcode: 2017arXiv170609079P
  We investigate the origin of 10 solar quiet-region pre-jet
  minifilaments, using EUV images from the Solar Dynamics Observatory
  (SDO)/Atmospheric Imaging Assembly (AIA) and magnetograms from the
  SDO Helioseismic and Magnetic Imager (HMI). We recently found that
  quiet-region coronal jets are driven by minifilament eruptions, where
  those eruptions result from flux cancellation at the magnetic neutral
  line under the minifilament. Here, we study the longer-term origin of
  the pre-jet minifilaments themselves. We find that they result from
  flux cancellation between minority-polarity and majority-polarity flux
  patches. In each of 10 pre-jet regions, we find that opposite-polarity
  patches of magnetic flux converge and cancel, with a flux reduction
  of 10%-40% from before to after the minifilament appears. For our 10
  events, the minifilaments exist for periods ranging from 1.5 hr to 2
  days before erupting to make a jet. Apparently, the flux cancellation
  builds a highly sheared field that runs above and traces the neutral
  line, and the cool transition region plasma minifilament forms in this
  field and is suspended in it. We infer that the convergence of the
  opposite-polarity patches results in reconnection in the low corona
  that builds a magnetic arcade enveloping the minifilament in its core,
  and that the continuing flux cancellation at the neutral line finally
  destabilizes the minifilament field so that it erupts and drives the
  production of a coronal jet. Thus, our observations strongly support
  that quiet-region magnetic flux cancellation results in both the
  formation of the pre-jet minifilament and its jet-driving eruption.

---------------------------------------------------------
Title: Evidence from IRIS that Sunspot Large Penumbral Jets Spin
Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; De Pontieu, Bart;
   Tarbell, Theodore D.; Panesar, Navdeep K.; Winebarger, Amy; Sterling,
   Alphonse C.
2017SPD....4810506T    Altcode:
  Recent observations from {\it Hinode} (SOT/FG) revealed the presence of
  large penumbral jets (widths $\ge$500 km, larger than normal penumbral
  microjets, which have widths $&lt;$ 400 km) repeatedly occurring at the
  same locations in a sunspot penumbra, at the tail of a filament or where
  the tails of several penumbral filaments apparently converge (Tiwari et
  al. 2016, ApJ). These locations were observed to have mixed-polarity
  flux in Stokes-V images from SOT/FG. Large penumbral jets displayed
  direct signatures in AIA 1600, 304, 171, and 193 channels; thus they
  were heated to at least transition region temperatures. Because
  large jets could not be detected in AIA 94 \AA, whether they had
  any coronal-temperature plasma remains unclear. In the present work,
  for another sunspot, we use IRIS Mg II k 2796 Å slit jaw images and
  spectra and magnetograms from Hinode SOT/FG and SOT/SP to examine:
  whether penumbral jets spin, similar to spicules and coronal jets in the
  quiet Sun and coronal holes; whether they stem from mixed-polarity flux;
  and whether they produce discernible coronal emission, especially in
  AIA 94 Å images. The few large penumbral jets for which we have IRIS
  spectra show evidence of spin. If these have mixed-polarity at their
  base, then they might be driven the same way as coronal jets and CMEs.

---------------------------------------------------------
Title: Babcock Redux: An Amendment of Babcock's Schematic of the
    Sun's Magnetic Cycle
Authors: Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.
2017SPD....4811103M    Altcode:
  We amend Babcock's original scenario for the global dynamo process
  that sustains the Sun's 22-year magnetic cycle. The amended scenario
  fits post-Babcock observed features of the magnetic activity cycle and
  convection zone, and is based on ideas of Spruit &amp; Roberts (1983,
  Nature, 304, 401) about magnetic flux tubes in the convection zone. A
  sequence of four schematic cartoons lays out the proposed evolution
  of the global configuration of the magnetic field above, in, and at
  the bottom of the convection zone through sunspot Cycle 23 and into
  Cycle 24. Three key elements of the amended scenario are: (1) as the
  net following-polarity magnetic field from the sunspot-region Ω-loop
  fields of an ongoing sunspot cycle is swept poleward to cancel and
  replace the opposite-polarity polar-cap field from the previous sunspot
  cycle, it remains connected to the ongoing sunspot cycle's toroidal
  source-field band at the bottom of the convection zone; (2) topological
  pumping by the convection zone's free convection keeps the horizontal
  extent of the poleward-migrating following-polarity field pushed to
  the bottom, forcing it to gradually cancel and replace old horizontal
  field below it that connects the ongoing-cycle source-field band to
  the previous-cycle polar-cap field; (3) in each polar hemisphere,
  by continually shearing the poloidal component of the settling new
  horizontal field, the latitudinal differential rotation low in the
  convection zone generates the next-cycle source-field band poleward
  of the ongoing-cycle band. The amended scenario is a more-plausible
  version of Babcock's scenario, and its viability can be explored
  by appropriate kinematic flux-transport solar-dynamo simulations. A
  paper giving a full description of our dynamo scenario is posted on
  arXiv (http://arxiv.org/abs/1606.05371).This work was funded by the
  Heliophysics Division of NASA's Science Mission Directorate through
  the Living With a Star Targeted Research and Technology Program and
  the Hinode Project.

---------------------------------------------------------
Title: Solar Active Region Coronal Jets. II. Triggering and Evolution
    of Violent Jets
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.;
   Panesar, Navdeep K.; Martinez, Francisco
2017ApJ...844...28S    Altcode: 2017arXiv170503040S
  We study a series of X-ray-bright, rapidly evolving active region
  coronal jets outside the leading sunspot of AR 12259, using Hinode/X-ray
  telescope, Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly
  (AIA) and Helioseismic and Magnetic Imager (HMI), and Interface
  Region Imaging Spectrograph (IRIS) data. The detailed evolution of
  such rapidly evolving “violent” jets remained a mystery after our
  previous investigation of active region jets. The jets we investigate
  here erupt from three localized subregions, each containing a rapidly
  evolving (positive) minority-polarity magnetic-flux patch bathed in a
  (majority) negative-polarity magnetic-flux background. At least several
  of the jets begin with eruptions of what appear to be thin (thickness
  ≲ 2<SUP>\prime\prime</SUP> ) miniature-filament (minifilament)
  “strands” from a magnetic neutral line where magnetic flux
  cancelation is ongoing, consistent with the magnetic configuration
  presented for coronal-hole jets in Sterling et al. (2016). Some jets
  strands are difficult/impossible to detect, perhaps due to, e.g.,
  their thinness, obscuration by surrounding bright or dark features,
  or the absence of erupting cool-material minifilaments in those
  jets. Tracing in detail the flux evolution in one of the subregions,
  we find bursts of strong jetting occurring only during times of strong
  flux cancelation. Averaged over seven jetting episodes, the cancelation
  rate was ∼ 1.5× {10}<SUP>19</SUP> Mx hr<SUP>-1</SUP>. An average
  flux of ∼ 5× {10}<SUP>18</SUP> Mx canceled prior to each episode,
  arguably building up ∼10<SUP>28</SUP>-10<SUP>29</SUP> erg of free
  magnetic energy per jet. From these and previous observations, we infer
  that flux cancelation is the fundamental process responsible for the
  pre-eruption build up and triggering of at least many jets in active
  regions, quiet regions, and coronal holes.

---------------------------------------------------------
Title: The Triggering Mechanism of Coronal Jets and CMEs: Flux
    Cancelation
Authors: Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald
2017shin.confE..27P    Altcode:
  Recent investigations (e.g. Sterling et al 2015, Panesar et al 2016)
  show that coronal jets are driven by the eruption of a small-scale
  filament (10,000 - 20,000 km long, called a minifilament) following
  magnetic flux cancelation at the neutral line underneath the
  minifilament. Minifilament eruptions appear to be analogous to
  larger-scale solar filament eruptions: they both reside, before
  the eruption, in the highly sheared field between the adjacent
  opposite-polarity magnetic flux patches (neutral line); jet-producing
  minifilament and larger-scale solar filament first show a slow-rise,
  followed by a fast-rise as they erupt; during the jet-producing
  minifilament eruption a jet bright point (JBP) appears at the
  location where the minifilament was rooted before the eruption,
  analogous to the situation with CME-producing larger-scale filament
  eruptions where a solar flare arcade forms during the filament eruption
  along the neutral line along which the filament resided prior to its
  eruption. In the present study we investigate the triggering mechanism
  of CME-producing large solar filament eruptions, and find that enduring
  flux cancelation at the neutral line of the filaments often triggers
  their eruptions. This corresponds to the finding that persistent flux
  cancelation at the neutral is the cause of jet-producing minifilament
  eruptions. Thus our observations support coronal jets being miniature
  version of CMEs.

---------------------------------------------------------
Title: Evaluation of the Minifilament-Eruption Scenario for Solar
    Coronal Jets in Polar Coronal Holes
Authors: Sterling, A. C.; Baikie, T. K.; Falconer, D. A.; Moore,
   R. L.; Savage, S. L.
2016AGUFMSH31B2574S    Altcode:
  Solar coronal jets are suspected to result from magnetic reconnection
  low in the Sun's atmosphere. Sterling et al. (2015) looked at 20 jets
  in polar coronal holes, using X-ray images from the Hinode/X-Ray
  Telescope (XRT) and EUV images from the Solar Dynamics Observatory
  (SDO) Atmospheric Imaging Assembly (AIA). They suggested that each jet
  was driven by the eruption of twisted closed magnetic field carrying
  a small-scale filament, which they call a "minifilament", and that
  the jet was produced by reconnection of the erupting field with
  surrounding open field. In this study, we carry out a more extensive
  examination of polar coronal jets. From 280 hours of XRT polar coronal
  hole observations spread over two years (2014-2016), we identified 117
  clearly-identifiable X-ray jet events. From the broader set, we selected
  25 of the largest and brightest events for further study in AIA 171,
  193, 211, and 304 Angstrom images. We find that at least the majority
  of the jets follow the minifilament-eruption scenario, although for some
  cases the evolution of the minifilament in the onset of its eruption is
  more complex then presented in the simplified schematic of Sterling et
  al. (2015). For all cases in which we could make a clear determination,
  the spire of the X-ray jet drifted laterally away from the jet-base-edge
  bright point; this spire drift away from the bright point is consistent
  with expectations of the minifilament-eruption scenario for coronal-jet
  production. This work was supported with funding from the NASA/MSFC
  Hinode Project Office, and from the NASA HGI program.

---------------------------------------------------------
Title: Solar Coronal Jets in Active Regions
Authors: Sterling, A. C.; Moore, R. L.; Martinez, F.; Falconer, D. A.
2016AGUFMSH43E..06S    Altcode:
  Solar coronal jets are common in both coronal holes and in active
  regions. Recently, Sterling et al. (2015, Nature 523, 437), using data
  from Hinode/XRT and SDO/AIA, found that coronal jets originating in
  polar coronal holes result from the eruption of small-scale filaments
  (minifilaments). The jet bright point (JBP) seen in X-rays and hotter
  EUV channels off to one side of the base of the jet's spire develops
  at the location where the minifilament erupts, consistent with the JBPs
  being miniature versions of typical solar flares that occur in the wake
  of large-scale filament eruptions. Here we consider whether active
  region coronal jets also result from the same minifilament-eruption
  mechanism, or whether they instead result from a different process, such
  as emerging flux. Here we present observations of NOAA active region
  12259, over 13-20 Jan 2015, using observations from Hinode/XRT, and
  from SDO/AIA and HMI. We focused on 13 standout jets that we identified
  from an initial survey of the XRT X-ray images, and we found many more
  jets in the AIA data set, which have higher cadence and more continuous
  coverage than our XRT data. All 13 jets originated from identifiable
  magnetic neutral lines; we further found magnetic flux cancelation to
  be occurring at essentially all of these neutral lines. At least 6 of
  those 13 jets were homologous, developing with similar morphology from
  nearly the same location, and in fact there were many more jets in the
  homologous sequence apparent in the higher-fidelity AIA data. Each of
  these homologous jets was consistent with minifilament-like ejections at
  the start of the jets. Other jets displayed a variety of morphologies,
  at least some of which were consistent with minifilament eruptions. For
  other jets however we have not yet clearly deciphered the driving
  mechanism. Our overall conclusions are similar to those of our earlier
  study of active region jets (Sterling et al. 2016, ApJ, 821, 100), where
  we found: some jets clearly to result from mini-filament eruptions;
  it was difficult to disentangle the mechanism of some other jets;
  and all of the jets originated from magnetic neutral lines, most of
  which were undergoing flux cancelation. This work was supported by
  funding from NASA/HGI, from the Hinode project, and (for FM) from the
  NASA/MSFC Research Experience for Undergraduates (REU) program.

---------------------------------------------------------
Title: Flux Cancellation Leading to Solar Filament Eruptions
Authors: Popescu, R. M.; Panesar, N. K.; Sterling, A. C.; Moore, R. L.
2016AGUFMSH31B2572P    Altcode:
  Solar filaments are strands of relatively cool, dense plasma
  magnetically suspended in the lower density hotter solar corona. They
  trace magnetic polarity inversion lines (PILs) in the photosphere
  below, and are supported against gravity at heights of up to 100 Mm
  above the chromosphere by the magnetic field in and around them. This
  field erupts when it is rendered unstable by either magnetic flux
  cancellation or emergence at or near the PIL. We have studied the
  evolution of photospheric magnetic flux leading to ten observed filament
  eruptions. Specifically, we look for gradual magnetic changes in the
  neighborhood of the PIL prior to and during eruption. We use Extreme
  Ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA),
  and magnetograms from the Helioseismic and Magnetic Imager (HMI),
  both onboard the Solar Dynamics Observatory (SDO), to study filament
  eruptions and their photospheric magnetic fields. We examine whether
  flux cancellation or/and emergence leads to filament eruptions and
  find that continuous flux cancellation was present at the PIL for many
  hours prior to each eruption. We present two events in detail and find
  the following: (a) the pre-eruption filament-holding core field is
  highly sheared and appears in the shape of a sigmoid above the PIL;
  (b) at the start of the eruption the opposite arms of the sigmoid
  reconnect in the middle above the site of (tether-cutting) flux
  cancellation at the PIL; (c) the filaments first show a slow-rise,
  followed by a fast-rise as they erupt. We conclude that these two
  filament eruptions result from flux cancellation in the middle of
  the sheared field and are in agreement with the standard model for
  a CME/flare filament eruption from a closed bipolar magnetic field
  [flux cancellation (van Ballegooijen and Martens 1989 and Moore and
  Roumelrotis 1992) and runaway tether-cutting (Moore et. al 2001)].

---------------------------------------------------------
Title: Coronal Jets from Minifilament Eruptions in Active Regions
Authors: Sterling, A. C.; Martinez, F.; Falconer, D. A.; Moore, R. L.
2016AGUFMSH31B2567S    Altcode:
  Solar coronal jets are transient (frequently of lifetime 10 min)
  features that shoot out from near the solar surface, become much
  longer than their width, and occur in all solar regions, including
  coronal holes, quiet Sun, and active regions (e.g., Shimojo et
  al. 1996, Certain et al. 2007). Sterling et al. (2015) and other
  studies found that in coronal holes and in quiet Sun the jets
  result when small-scale filaments, called “minifilaments,” erupt
  onto nearby open or high-reaching field lines. Additional studies
  found that coronal-jet-onset locations (and hence presumably the
  minifilament-eruption-onset locations) coincided with locations of
  magnetic-flux cancellation. For active region (AR) jets however the
  situation is less clear. Sterling et al. (2016) studied jets in one
  active region over a 24-hour period; they found that some AR jets
  indeed resulted from minifilament eruptions, usually originating
  from locations of episodes of magnetic-flux cancelation. In some
  cases however they could not determine whether flux was emerging or
  canceling at the polarity inversion line from which the minifilament
  erupted; and for other jets of that region minifilaments were not
  conclusively apparent prior to jet occurrence. Here we further study
  AR jets, by observing them in a single AR over a one-week period,
  using X-ray images from Hinode/XRT and EUV/UV images from SDO/AIA,
  and line-of-sight magnetograms and white-light intensity-grams from
  SDO/HMI. We initially identified 13 prominent jets in the XRT data,
  and examined corresponding AIA and HMI data. For at least several of
  the jets, our findings are consistent with the jets resulting from
  minifilament eruptions, and originating from sights of magnetic-field
  cancelation. Thus our findings support that, at least in many cases,
  AR coronal jets result from the same physical processes that produce
  coronal jets in quiet-Sun and coronal-hole regions. FM was supportedby
  the Research Experience for Undergraduates (REU) program at NASA/MSFC
  and the University of Alabama, Huntsville. Additional support was from
  the NASA HGI program and the Hinode project.

---------------------------------------------------------
Title: Solar Coronal Jets: Observations, Theory, and Modeling
Authors: Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.;
   Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.;
   DeVore, C. R.; Archontis, V.; Török, T.; Mason, H.; Curdt, W.;
   Meyer, K.; Dalmasse, K.; Matsui, Y.
2016SSRv..201....1R    Altcode: 2016arXiv160702108R; 2016SSRv..tmp...31R
  Coronal jets represent important manifestations of ubiquitous solar
  transients, which may be the source of significant mass and energy
  input to the upper solar atmosphere and the solar wind. While
  the energy involved in a jet-like event is smaller than that of
  "nominal" solar flares and coronal mass ejections (CMEs), jets
  share many common properties with these phenomena, in particular,
  the explosive magnetically driven dynamics. Studies of jets could,
  therefore, provide critical insight for understanding the larger,
  more complex drivers of the solar activity. On the other side of the
  size-spectrum, the study of jets could also supply important clues on
  the physics of transients close or at the limit of the current spatial
  resolution such as spicules. Furthermore, jet phenomena may hint to
  basic process for heating the corona and accelerating the solar wind;
  consequently their study gives us the opportunity to attack a broad
  range of solar-heliospheric problems.

---------------------------------------------------------
Title: Magnetic Flux Cancelation as the Trigger of Solar Quiet-region
    Coronal Jets
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
   Chakrapani, Prithi
2016ApJ...832L...7P    Altcode: 2016arXiv161008540P
  We report observations of 10 random on-disk solar quiet-region coronal
  jets found in high-resolution extreme ultraviolet (EUV) images from the
  Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly and having
  good coverage in magnetograms from the SDO/Helioseismic and Magnetic
  Imager (HMI). Recent studies show that coronal jets are driven by the
  eruption of a small-scale filament (called a minifilament). However,
  the trigger of these eruptions is still unknown. In the present
  study, we address the question: what leads to the jet-driving
  minifilament eruptions? The EUV observations show that there is a
  cool-transition-region-plasma minifilament present prior to each jet
  event and the minifilament eruption drives the jet. By examining pre-jet
  evolutionary changes in the line of sight photospheric magnetic field,
  we observe that each pre-jet minifilament resides over the neutral line
  between majority-polarity and minority-polarity patches of magnetic
  flux. In each of the 10 cases, the opposite-polarity patches approach
  and merge with each other (flux reduction between 21% and 57%). After
  several hours, continuous flux cancelation at the neutral line
  apparently destabilizes the field holding the cool-plasma minifilament
  to erupt and undergo internal reconnection, and external reconnection
  with the surrounding coronal field. The external reconnection opens the
  minifilament field allowing the minifilament material to escape outward,
  forming part of the jet spire. Thus, we found that each of the 10 jets
  resulted from eruption of a minifilament following flux cancelation at
  the neutral line under the minifilament. These observations establish
  that magnetic flux cancelation is usually the trigger of quiet-region
  coronal jet eruptions.

---------------------------------------------------------
Title: The 2016 Transit of Mercury Observed from Major Solar
    Telescopes and Satellites
Authors: Pasachoff, Jay M.; Schneider, Glenn; Gary, Dale; Chen, Bin;
   Sterling, Alphonse C.; Reardon, Kevin P.; Dantowitz, Ronald; Kopp,
   Greg A.
2016DPS....4811705P    Altcode:
  We report observations from the ground and space of the 9 May 2016
  transit of Mercury. We build on our explanation of the black-drop
  effect in transits of Venus based on spacecraft observations of the 1999
  transit of Mercury (Schneider, Pasachoff, and Golub, Icarus 168, 249,
  2004). In 2016, we used the 1.6-m New Solar Telescope at the Big Bear
  Solar Observatory with active optics to observe Mercury's transit at
  high spatial resolution. We again saw a small black-drop effect as 3rd
  contact neared, confirming the data that led to our earlier explanation
  as a confluence of the point-spread function and the extreme solar
  limb darkening (Pasachoff, Schneider, and Golub, in IAU Colloq. 196,
  2004). We again used IBIS on the Dunn Solar Telescope of the Sacramento
  Peak Observatory, as A. Potter continued his observations, previously
  made at the 2006 transit of Mercury, at both telescopes of the sodium
  exosphere of Mercury (Potter, Killen, Reardon, and Bida, Icarus 226,
  172, 2013). We imaged the transit with IBIS as well as with two RED
  Epic IMAX-quality cameras alongside it, one with a narrow passband. We
  show animations of our high-resolution ground-based observations along
  with observations from XRT on JAXA's Hinode and from NASA's Solar
  Dynamics Observatory. Further, we report on the limit of the transit
  change in the Total Solar Irradiance, continuing our interest from
  the transit of Venus TSI (Schneider, Pasachoff, and Willson, ApJ 641,
  565, 2006; Pasachoff, Schneider, and Willson, AAS 2005), using NASA's
  SORCE/TIM and the Air Force's TCTE/TIM. See http://transitofvenus.info
  and http://nicmosis.as.arizona.edu.Acknowledgments: We were glad for
  the collaboration at Big Bear of Claude Plymate and his colleagues of
  the staff of the Big Bear Solar Observatory. We also appreciate the
  collaboration on the transit studies of Robert Lucas (Sydney, Australia)
  and Evan Zucker (San Diego, California). JMP appreciates the sabbatical
  hospitality of the Division of Geosciences and Planetary Sciences of
  the California Institute of Technology, and of Prof. Andrew Ingersoll
  there. The solar observations lead into the 2017 eclipse studies,
  for which JMP is supported by grants from the NSF AGS and National
  Geographic CRE.

---------------------------------------------------------
Title: Babcock Redux: An Amendment of Babcock's Schematic of the
    Sun's Magnetic Cycle
Authors: Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.
2016usc..confE...5M    Altcode: 2016arXiv160605371M
  We amend Babcock's original scenario for the global dynamo process
  that sustains the Sun's 22-year magnetic cycle. The amended scenario
  fits post-Babcock observed features of the magnetic activity cycle
  and convection zone, and is based on ideas of Spruit &amp; Roberts
  (1983) about magnetic flux tubes in the convection zone. A sequence of
  four schematic cartoons lays out the proposed evolution of the global
  configuration of the magnetic field above, in, and at the bottom of the
  convection zone through sunspot Cycle 23 and into Cycle 24. Three key
  elements of the amended scenario are: (1) as the net following-polarity
  magnetic field from the sunspot-region -loop fields of an
  ongoing sunspot cycle is swept poleward to cancel and replace the
  opposite-polarity polar-cap field from the previous sunspot cycle, it
  remains connected to the ongoing sunspot cycle's toroidal source-field
  band at the bottom of the convection zone; (2) topological pumping by
  the convection zone's free convection keeps the horizontal extent of
  the poleward-migrating following-polarity field pushed to the bottom,
  forcing it to gradually cancel and replace old horizontal field below it
  that connects the ongoing-cycle source-field band to the previous-cycle
  polar-cap field; (3) in each polar hemisphere, by continually shearing
  the poloidal component of the settling new horizontal field, the
  latitudinal differential rotation low in the convection zone generates
  the next-cycle source-field band poleward of the ongoing-cycle band. The
  amended scenario is a more-plausible version of Babcock's scenario, and
  its viability can be explored by appropriate kinematic flux-transport
  solar-dynamo simulations. A paper of the above title and authors, giving
  a full description of the solar dynamo scenario of this abstract, is
  available at http://arxiv.org/abs/1606.05371. This work was funded by
  the Heliophysics Division of NASA's Science Mission Directorate through
  the Living With a Star Targeted Research and Technology Program and
  the Hinode Project.

---------------------------------------------------------
Title: A Microfilament-eruption Mechanism for Solar Spicules
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2016ApJ...828L...9S    Altcode: 2016arXiv161200430S
  Recent investigations indicate that solar coronal jets result from
  eruptions of small-scale chromospheric filaments, called minifilaments;
  that is, the jets are produced by scaled-down versions of typical-sized
  filament eruptions. We consider whether solar spicules might in turn
  be scaled-down versions of coronal jets, being driven by eruptions
  of microfilaments. Assuming a microfilament's size is about a
  spicule's width (∼300 km), the estimated occurrence number plotted
  against the estimated size of erupting filaments, minifilaments, and
  microfilaments approximately follows a power-law distribution (based
  on counts of coronal mass ejections, coronal jets, and spicules),
  suggesting that many or most spicules could result from microfilament
  eruptions. Observed spicule-base Ca II brightenings plausibly result
  from such microfilament eruptions. By analogy with coronal jets,
  microfilament eruptions might produce spicules with many of their
  observed characteristics, including smooth rise profiles, twisting
  motions, and EUV counterparts. The postulated microfilament eruptions
  are presumably eruptions of twisted-core micro-magnetic bipoles
  that are ∼1.″0 wide. These explosive bipoles might be built and
  destabilized by merging and cancelation of approximately a few to 100
  G magnetic-flux elements of size ≲ 0\buildrel{\prime\prime}\over{.}
  5{--}1\buildrel{\prime\prime}\over{.} 0. If, however, spicules
  are relatively more numerous than indicated by our extrapolated
  distribution, then only a fraction of spicules might result from this
  proposed mechanism.

---------------------------------------------------------
Title: Homologous Jet-driven Coronal Mass Ejections from Solar Active
    Region 12192
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.
2016ApJ...822L..23P    Altcode: 2016arXiv160405770P
  We report observations of homologous coronal jets and their coronal mass
  ejections (CMEs) observed by instruments onboard the Solar Dynamics
  Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO)
  spacecraft. The homologous jets originated from a location with emerging
  and canceling magnetic field at the southeastern edge of the giant
  active region (AR) of 2014 October, NOAA 12192. This AR produced in
  its interior many non-jet major flare eruptions (X- and M- class) that
  made no CME. During October 20 to 27, in contrast to the major flare
  eruptions in the interior, six of the homologous jets from the edge
  resulted in CMEs. Each jet-driven CME (∼200-300 km s<SUP>-1</SUP>)
  was slower-moving than most CMEs, with angular widths (20°-50°)
  comparable to that of the base of a coronal streamer straddling the AR
  and were of the “streamer-puff” variety, whereby the preexisting
  streamer was transiently inflated but not destroyed by the passage
  of the CME. Much of the transition-region-temperature plasma in the
  CME-producing jets escaped from the Sun, whereas relatively more of
  the transition-region plasma in non-CME-producing jets fell back to
  the solar surface. Also, the CME-producing jets tended to be faster and
  longer-lasting than the non-CME-producing jets. Our observations imply
  that each jet and CME resulted from reconnection opening of twisted
  field that erupted from the jet base and that the erupting field did
  not become a plasmoid as previously envisioned for streamer-puff CMEs,
  but instead the jet-guiding streamer-base loop was blown out by the
  loop’s twist from the reconnection.

---------------------------------------------------------
Title: A Series of Streamer-Puff CMEs Driven by Solar Homologous
    Jets from Active Region 12192
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.
2016SPD....47.0622P    Altcode:
  We investigate characteristics of solar coronal jets that originated
  from active region NOAA 12192 and produced coronal mass ejections
  (CMEs). This active region produced many non-jet major flare eruptions
  (X and M class) that made no CME. A multitude of jets occurred from the
  southeast edge of the active region, and in contrast to the major-flare
  eruptions in the core, six of these jets resulted in CMEs. Our jet
  observations are from multiple SDO/AIA EUV channels, including 304,
  171 and 193Å, and CME observations are taken from SOHO/LASCO C2
  coronograph. Each jet-driven CME was relatively slow-moving (~200
  - 300 km s<SUP>-1</SUP>) compared to most CMEs; had angular width
  (20° - 50°) comparable to that of the streamer base; and was of
  the “streamer-puff” variety, whereby a preexisting streamer was
  transiently inflated but not removed (blown out) by the passage of
  the CME. Much of the chromospheric-temperature plasma of the jets
  producing the CMEs escaped from the Sun, whereas relatively more of
  the chromospheric plasma in the non-CME-producing jets fell back to
  the solar surface. We also found that the CME-producing jets tended to
  be faster in speed and longer in duration than the non-CME-producing
  jets. We expect that the jets result from eruptions of minifilaments
  (Sterling et al. 2015). We further propose that the CMEs are driven
  by magnetic twist injected into streamer-base coronal loops when
  erupting-twisted-minifilament field reconnects with the ambient field
  at the foot of those loops. This research was supported by funding
  from NASA's LWS program.

---------------------------------------------------------
Title: Analysis of an Anemone-Type Eruption in an On-Disk Coronal Hole
Authors: Adams, Mitzi; Tennant, Allyn F.; Alexander, Caroline E.;
   Sterling, Alphonse C.; Moore, Ronald L.; Woolley, Robert
2016SPD....4740701A    Altcode:
  We report on an eruption seen in a very small coronal hole (about
  120” across), beginning at approximately 19:00 UT on March 3,
  2016. The event was initially observed by an amateur astronomer (RW)
  in an H-alpha movie from the Global Oscillation Network Group (GONG);
  the eruption attracted the attention of the observer because there was
  no nearby active region. To examine the region in detail, we use data
  from the Solar Dynamics Observatory (SDO), provided by the Atmospheric
  Imaging Assembly (AIA) in wavelengths 193 Å, 304 Å, and 94 Å, and the
  Helioseismic and Magnetic Imager (HMI). Data analysis and calibration
  activities such as scaling, rotation so that north is up, and removal of
  solar rotation are accomplished with SunPy. The eruption in low-cadence
  HMI data begins with the appearance of a bipole in the location of
  the coronal hole, followed by (apparent) expansion outwards when the
  intensity of the AIA wavelengths brighten; as the event proceeds,
  the coronal hole disappears. From high-cadence data, we will present
  results on the magnetic evolution of this structure, how it is related
  to intensity brightenings seen in the various SDO/AIA wavelengths,
  and how this event compares with the standard-anemone picture.

---------------------------------------------------------
Title: Minifilament Eruptions that Drive Coronal Jets in a Solar
    Active Region
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David;
   Panesar, Navdeep; Akiyama, Sachiko; Yashiro, Seiji; Gopalswamy, Nat
2016SPD....47.0334S    Altcode:
  Solar coronal jets are common in both coronal holes and in active
  regions. Recently, Sterling et al. (2015), using data from Hinode/XRT
  and SDO/AIA, found that coronal jets originating in polar coronal holes
  result from the eruption of small-scale filaments (minifilaments). The
  jet bright point (JBP) seen in X-rays and hotter EUV channels off to one
  side of the base of the jet's spire develops at the location where the
  minifilament erupts, consistent with the JBPs being miniature versions
  of typical solar flares that occur in the wake of large-scale filament
  eruptions. Here we consider whether active region coronal jets also
  result from the same minifilament-eruption mechanism, or whether they
  instead result from a different mechanism, such as the hitherto popular
  “emerging flux” model for jets. We present observations of an on-disk
  active region that produced numerous jets on 2012 June 30, using data
  from SDO/AIA and HMI, and from GOES/SXI. We find that several of these
  active region jets also originate with eruptions of miniature filaments
  (size scale ~20”) emanating from small-scale magnetic neutral lines
  of the region. This demonstrates that active region coronal jets are
  indeed frequently driven by minifilament eruptions. Other jets from the
  active region were also consistent with their drivers being minifilament
  eruptions, but we could not confirm this because the onsets of those
  jets were hidden from our view. This work was supported by funding
  from NASA/LWS, NASA/HGI, and Hinode.

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Title: Early Evaluation of the Corona at the 2016 March 9 Total
    Solar Eclipse
Authors: Pasachoff, Jay M.; Seaton, Daniel B.; Sterling, Alphonse C.
2016SPD....47.0326P    Altcode:
  We observed the corona on 2016 March 9 with a variety of assets on
  the ground and in space. The umbra of the total eclipse swept across
  Indonesia and into the Pacific, with totality at our Indonesian
  observation sites lasting 2 min 45 s at Ternate in the Spice Islands
  (Malukus) and 2 min 10 at Belitung. We compare our ground-based
  results with the coronal configurations observed with PROBA2/SWAP
  and Hinode XRT. One of our scientific goals is to follow the coronal
  configuration over the solar-activity cycle, with the sunspot number
  now half its maximum of either its 2012 or 2014 peak. We are evaluating
  temporal changes by comparing eclipse observations made at several
  ground-based sites along the path, with the longest span being 75 min
  from Belitung to the Woleia atoll in mid-Pacific, 1:25 UTC to 2:40 UTC;
  we are evaluating whether the airborne observations made at 3:35 UTC
  on March 8 (across the International Dateline) are of suitable quality
  to provide further comparison at high spatial resolution. We also
  compare our images with the near-simultaneous coronal observations
  made with SOHO/LASCO, SDO/AIA, STEREO-A/SECCHI, and the Mauna Loa
  Solar Observatory's K-cor coronagraph. ACS received support for image
  analysis from the Hinode project.

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Title: Minifilament Eruptions that Drive Coronal Jets in a Solar
    Active Region
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.;
   Panesar, Navdeep K.; Akiyama, Sachiko; Yashiro, Seiji; Gopalswamy, Nat
2016ApJ...821..100S    Altcode:
  We present observations of eruptive events in an active region adjacent
  to an on-disk coronal hole on 2012 June 30, primarily using data from
  the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA),
  SDO/Helioseismic and Magnetic Imager (HMI), and STEREO-B. One eruption
  is of a large-scale (∼100″) filament that is typical of other
  eruptions, showing slow-rise onset followed by a faster-rise motion
  starting as flare emissions begin. It also shows an “EUV crinkle”
  emission pattern, resulting from magnetic reconnections between
  the exploding filament-carrying field and surrounding field. Many
  EUV jets, some of which are surges, sprays and/or X-ray jets, also
  occur in localized areas of the active region. We examine in detail
  two relatively energetic ones, accompanied by GOES M1 and C1 flares,
  and a weaker one without a GOES signature. All three jets resulted
  from small-scale (∼20″) filament eruptions consistent with a slow
  rise followed by a fast rise occurring with flare-like jet-bright-point
  brightenings. The two more-energetic jets showed crinkle patters, but
  the third jet did not, perhaps due to its weakness. Thus all three jets
  were consistent with formation via erupting minifilaments, analogous
  to large-scale filament eruptions and to X-ray jets in polar coronal
  holes. Several other energetic jets occurred in a nearby portion of
  the active region; while their behavior was also consistent with their
  source being minifilament eruptions, we could not confirm this because
  their onsets were hidden from our view. Magnetic flux cancelation
  and emergence are candidates for having triggered the minifilament
  eruptions.

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Title: Probing Solar Eruption by Tracking Magnetic Cavities and
    Filaments
Authors: Sterling, A. C.; Johnson, J. R.; Moore, R. L.; Gibson, S. E.
2015AGUFMSH53B2489S    Altcode:
  A solar eruption is a tremendous explosion on the Sun that happens when
  energy stored in twisted (or distorted) magnetic fields is suddenly
  released. When this field is viewed along the axis of the twist in
  projection at the limb, e.g. in EUV or white-light coronal images,
  the outer portions of the pre-eruption magnetic structure sometimes
  appears as a region of weaker emission, called a "coronal cavity,"
  surrounded by a brighter envelope. Often a chromospheric filament
  resides near the base of the cavity and parallel to the cavity's central
  axis. Typically, both the cavity and filament move outward from the Sun
  at the start of an eruption of the magnetic field in which the cavity
  and filament reside. Studying properties the cavities and filaments
  just prior to and during eruption can help constrain models that
  attempt to explain why and how the eruptions occur. In this study,
  we examined six different at-limb solar eruptions using images from
  the Extreme Ultraviolet Imaging Telescope (EIT) aboard the Solar and
  Heliospheric Observatory (SOHO). For four of these eruptions we observed
  both cavities and filaments, while for the remaining two eruptions,
  one had only a cavity and the other only a filament visible in EIT
  images. All six eruptions were in comparatively-quiet solar regions,
  with one in the neighborhood of the polar crown. We measured the height
  and velocities of the cavities and filaments just prior to and during
  the start of their fast-eruption onsets. Our results support that the
  filament and cavity are integral parts of a single large-scale erupting
  magnetic-field system. We examined whether the eruption-onset heights
  were correlated with the expected magnetic field strengths of the
  eruption-source regions, but no clear correlation was found. We discuss
  possible reasons for this lack of correlation, and we also discuss
  future research directions. The research performed was supported
  by the National Science Foundation under Grant No. AGS-1460767;
  J.J. participated in the Research Experience for Undergraduates (REU)
  program, at NASA/MSFC. Additional support was from a grant from the
  NASA LWS program.

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Title: Revised View of Solar X-Ray Jets
Authors: Sterling, A. C.; Moore, R. L.; Falconer, D. A.; Adams, M.
2015AGUFMSH23D..04S    Altcode:
  We investigate the onset of ~20 random X-ray jets observed by
  Hinode/XRT. Each jetwas near the limb in a polar coronal hole,
  and showed a ”bright point” in anedge of the base of the jet, as
  is typical for previously-observed X-ray jets. Weexamined SDO/AIA
  EUV images of each of the jets over multiple AIA channels,including
  304 Ang, which detects chromospheric emissions, and 171, 193, and
  211 Ang,which detect cooler-coronal emissions. We find the jets to
  result from eruptionsof miniature (size &lt;~10 arcsec) filaments from
  the bases of the jets. In manycases, much of the erupting-filament
  material forms a chromospheric-temperaturejet. In the cool-coronal
  channels, often the filament appears in absorption andthe hotter
  EUV component of the jet appears in emission. The jet bright point
  formsat the location from which the miniature filament erupts,
  analogous to theformation of a standard solar flare arcade via flare
  (“internal”) reconnection in the wake of the eruption of a typical
  larger-scale chromospheric filament. Thespire of the jet forms on open
  field lines that presumably have undergoneinterchange (”external”)
  reconnection with the erupting field that envelops andcarries the
  miniature filament. This is consistent with what we found for theonset
  of an on-disk coronal jet we examined in Adams et al. (2014), and
  theobservations of other workers. It is however not consistent with
  the basicversion of the ”emerging-flux model” for X-ray jets. This
  work was supported byfunding from NASA/LWS, Hinode, and ISSI.

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Title: Exploring the properties of Solar Prominence Tornados
Authors: Ahmad, E.; Panesar, N. K.; Sterling, A. C.; Moore, R. L.
2015AGUFMSH53B2485A    Altcode:
  Solar prominences consist of relatively cool and dense plasma
  embedded in the hotter solar corona above the solar limb. They
  form along magnetic polarity inversion lines, and are magnetically
  supported against gravity at heights of up to ~100 Mm above the
  chromosphere. Often, parts of prominences visually resemble Earth-based
  tornados, with inverted-cone-shaped structures and internal motions
  suggestive of rotation. These "prominence tornados" clearly possess
  complex magnetic structure, but it is still not certain whether
  they actually rotate around a ”rotation” axis, or instead just
  appear to do so because of composite internal material motions such
  as counter-streaming flows or lateral (i.e. transverse to the field)
  oscillations. Here we study the structure and dynamics of five randomly
  selected prominences, using extreme ultraviolet (EUV) 171 Å images
  obtained with high spatial and temporal resolution by the Atmospheric
  Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO)
  spacecraft. All of the prominences resided in non-active-region
  locations, and displayed what appeared to be tornado-like rotational
  motions. Our set includes examples oriented both broadside and end-on to
  our line-of-sight. We created time-distance plots of horizontal slices
  at several different heights of each prominence, to study the horizontal
  plasma motions. We observed patterns of oscillations at various heights
  in each prominence, and we measured parameters of these oscillations. We
  find the oscillation time periods to range over ~50 - 90 min, with
  average amplitudes of ~6,000 km, and with average velocities of ~7
  kms-1. We found similar values for prominences viewed either broadside
  or end-on; this observed isotropy of the lateral oscillatory motion
  suggests that the apparent oscillations result from actual rotational
  plasma motions and/or lateral oscillations of the magnetic field,
  rather than to counter-streaming flows. This research was supported
  by the National Science Foundation under Grant No. AGS-1460767;
  EA participated in the Research Experience for Undergraduates (REU)
  program, at NASA/MSFC. Additional support was from a grant from the
  NASA LWS program.

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Title: A Series of Streamer-Puff CMEs Driven by Solar Homologous Jets
Authors: Panesar, N. K.; Sterling, A. C.; Moore, R. L.
2015AGUFMSH54B..07P    Altcode:
  Solar coronal jets are magnetically channeled narrow eruptions
  often observed in the solar atmosphere, typically in EUV and X-ray
  emission, and occurring in various solar environments including
  active regions and coronal holes. Their driving mechanism is still
  under discussion, but facts that we know about jets include: (a)
  they are ejected from or near sites of compact magnetic explosions
  (compact ejective solar flares), (b) they sometimes carry chromospheric
  material high into the corona along with coronal-temperature plasma,
  (c) the cool-material jet velocities can reach 100 km s-1 or more, and
  (d) some active-region jets produce coronal mass ejections (CMEs). Here
  we investigate characteristics of EUV jets that originated from active
  region NOAA 12192 and produced CMEs. This active region produced many
  non-jet major flare eruptions (X and M class) that made no CME. A
  multitude of jets also occurred in the region, and in contrast to the
  major-flare eruptions, seven of these jets resulted in CMEs. Our jet
  observations are from multiple SDO/AIA EUV channels, including 304,
  171, 193 and 94 Å, and our CME observations are from SOHO/LASCO C2
  images. Each jet-driven CME was relatively slow-moving; had angular
  width (30° - 70°) comparable to that of the streamer base; and was
  of the "streamer-puff" variety, whereby a preexisting streamer was
  transiently inflated but not removed (blown out) by the passage of
  the CME. Much of the chromospheric-temperature plasma of the jets
  producing the CMEs escaped from the Sun, whereas relatively more of
  the chromospheric plasma in the non-CME-producing jets fell back to
  the solar surface. We also found that the CME-producing jets tended to
  be faster in speed and longer in duration than the non-CME-producing
  jets. This research was supported by funding from NASA's LWS program.

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Title: Visibility of Hinode/XRT X-Ray Jets at AIA/EUV Wavelengths,
    a Temperature Indicator
Authors: Sterling, A. C.; Bakucz Canario, D.; Moore, R. L.; Falconer,
   D. A.
2015AGUFMSH31B2415S    Altcode:
  X-ray jets have been observed for years using data from the X-Ray
  Telescope (XRT) on the Hinode Satellite. Recently with the launch of the
  Solar Dynamics Observatory (SDO) it has been possible to observe solar
  jets over a range of EUV of wavelengths using the Atmospheric Imaging
  Assembly (AIA). In this study, we investigated the appearance of X-ray
  jets in AIA images at wavelengths of 304, 171, 193, 211, 131, 94, and
  335 Å. We selected 20 random X-ray jets from XRT movies of the polar
  coronal holes and then examined AIA EUV images from the same locations
  and times to determine the visibility of the jets at the different EUV
  wavelengths. We found that the jets were almost always visible in the
  193 and 211 Å channel images. In the "hottest" EUV channels (94 Å, 335
  Å), usually the spire of the jet was not visible, although sometimes
  a base brightening could be discerned. At other wavelengths (171, 131,
  and 335), the results were mixed. Based on the response characteristics
  of AIA (Lemen et al, 2011) to the temperature of the observed radiating
  solar plasma, our finding that most jets are visible in the 193 and 211
  Å channels is consistent with other recent studies that measured jet
  temperatures of 1.5~2.0 MK (Pucci et al, 2012 &amp; Paraschiv et al,
  2015). This work was supported by the NASA LWS and HGI programs.

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Title: Destabilization of a Solar Prominence/Filament Field System
    by a Series of Eight Homologous Eruptive Flares Leading to a CME
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Innes, Davina E.;
   Moore, Ronald L.
2015ApJ...811....5P    Altcode: 2015arXiv150801952P
  Homologous flares are flares that occur repetitively in the same
  active region, with similar structure and morphology. A series of at
  least eight homologous flares occurred in active region NOAA 11237 over
  2011 June 16-17. A nearby prominence/filament was rooted in the active
  region, and situated near the bottom of a coronal cavity. The active
  region was on the southeast solar limb as seen from the Solar Dynamics
  Observatory/Atmospheric Imaging Assembly, and on the disk as viewed from
  the Solar TErrestrial RElations Observatory/EUVI-B. The dual perspective
  allows us to study in detail behavior of the prominence/filament
  material entrained in the magnetic field of the repeatedly erupting
  system. Each of the eruptions were mainly confined, but expelled hot
  material into the prominence/filament cavity system (PFCS). The field
  carrying and containing the ejected hot material interacted with the
  PFCS and caused it to inflate, resulting in a step-wise rise of the
  PFCS approximately in step with the homologous eruptions. The eighth
  eruption triggered the PFCS to move outward slowly, accompanied by
  a weak coronal dimming. As this slow PFCS eruption was underway, a
  final “ejective” flare occurred in the core of the active region,
  resulting in strong dimming in the EUVI-B images and expulsion of a
  coronal mass ejection (CME). A plausible scenario is that the repeated
  homologous flares could have gradually destabilized the PFCS, and its
  subsequent eruption removed field above the acitive region and in turn
  led to the ejective flare, strong dimming, and CME.

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Title: Small-scale filament eruptions as the driver of X-ray jets
    in solar coronal holes
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.;
   Adams, Mitzi
2015Natur.523..437S    Altcode: 2017arXiv170503373S
  Solar X-ray jets are thought to be made by a burst of reconnection
  of closed magnetic field at the base of a jet with ambient open
  field. In the accepted version of the `emerging-flux' model, such
  a reconnection occurs at a plasma current sheet between the open
  field and the emerging closed field, and also forms a localized X-ray
  brightening that is usually observed at the edge of the jet's base. Here
  we report high-resolution X-ray and extreme-ultraviolet observations
  of 20 randomly selected X-ray jets that form in coronal holes at
  the Sun's poles. In each jet, contrary to the emerging-flux model,
  a miniature version of the filament eruptions that initiate coronal
  mass ejections drives the jet-producing reconnection. The X-ray bright
  point occurs by reconnection of the `legs' of the minifilament-carrying
  erupting closed field, analogous to the formation of solar flares in
  larger-scale eruptions. Previous observations have found that some
  jets are driven by base-field eruptions, but only one such study, of
  only one jet, provisionally questioned the emerging-flux model. Our
  observations support the view that solar filament eruptions are formed
  by a fundamental explosive magnetic process that occurs on a vast range
  of scales, from the biggest mass ejections and flare eruptions down
  to X-ray jets, and perhaps even down to smaller jets that may power
  coronal heating. A similar scenario has previously been suggested,
  but was inferred from different observations and based on a different
  origin of the erupting minifilament.

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Title: Physical properties of solar polar jets. A statistical study
    with Hinode XRT data
Authors: Paraschiv, A. R.; Bemporad, A.; Sterling, A. C.
2015A&A...579A..96P    Altcode: 2015arXiv150507191P
  <BR /> Aims: The target of this work is to investigate the physical
  nature of polar jets in the solar corona and their possible contribution
  to coronal heating and solar wind flow based on the analysis of
  X-ray images acquired by the Hinode XRT telescope. We estimate the
  different forms of energy associated with many of these small-scale
  eruptions, in particular the kinetic energy and enthalpy. <BR />
  Methods: Two Hinode XRT campaign datasets focusing on the two polar
  coronal holes were selected to analyze the physical properties of
  coronal jets; the analyzed data were acquired using a series of
  three XRT filters. Typical kinematical properties (e.g., length,
  thickness, lifetime, ejection rate, and velocity) of 18 jets are
  evaluated from the observed sequences, thus providing information
  on their possible contribution to the fast solar wind flux escaping
  from coronal holes. Electron temperatures and densities of polar-jet
  plasmas are also estimated using ratios of the intensities observed
  in different filters. <BR /> Results: We find that the largest amount
  of energy eventually provided to the corona is thermal. The energy
  due to waves may also be significant, but its value is comparatively
  uncertain. The kinetic energy is lower than thermal energy, while other
  forms of energy are comparatively low. Lesser and fainter events seem
  to be hotter, thus the total contribution by polar jets to the coronal
  heating could have been underestimated so far. The kinetic energy flux
  is usually around three times smaller than the enthalpy counterpart,
  implying that this energy is converted into plasma heating more than in
  plasma acceleration. This result suggests that the majority of polar
  jets are most likely not escaping from the Sun and that only cooler
  ejections could possibly have enough kinetic energy to contribute to
  the total solar wind flow.

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Title: Magnetic Untwisting in Solar Jets that Go into the Outer
    Corona in Polar Coronal Holes
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David A.
2015ApJ...806...11M    Altcode: 2015arXiv150403700M
  We study 14 large solar jets observed in polar coronal holes. In
  EUV movies from the Solar Dynamics Observatory/Atmospheric Imaging
  Assembly (AIA), each jet appears similar to most X-ray jets and
  EUV jets that erupt in coronal holes; but each is exceptional in
  that it goes higher than most, so high that it is observed in the
  outer corona beyond 2.2 R <SUB>Sun</SUB> in images from the Solar
  and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph
  (LASCO)/C2 coronagraph. From AIA He ii 304 Å movies and LASCO/C2
  running-difference images of these high-reaching jets, we find: (1)
  the front of the jet transits the corona below 2.2 R <SUB>Sun</SUB> at
  a speed typically several times the sound speed; (2) each jet displays
  an exceptionally large amount of spin as it erupts; (3) in the outer
  corona, most of the jets display measureable swaying and bending of
  a few degrees in amplitude; in three jets the swaying is discernibly
  oscillatory with a period of order 1 hr. These characteristics suggest
  that the driver in these jets is a magnetic-untwisting wave that is
  basically a large-amplitude (i.e., nonlinear) torsional Alfvén wave
  that is put into the reconnected open field in the jet by interchange
  reconnection as the jet erupts. From the measured spinning and swaying,
  we estimate that the magnetic-untwisting wave loses most of its energy
  in the inner corona below 2.2 R <SUB>Sun</SUB>. We point out that the
  torsional waves observed in Type-II spicules might dissipate in the
  corona in the same way as the magnetic-untwisting waves in our big jets,
  and thereby power much of the coronal heating in coronal holes.

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Title: Small-Scale Filament Eruptions Leading to Solar X-Ray Jets
Authors: Sterling, Alphonse; Moore, Ronald; Falconer, David
2015TESS....140701S    Altcode:
  We investigate the onset of ~10 random X-ray jets observed by
  Hinode/XRT. Each jet was near the limb in a polar coronal hole, and
  showed a “bright point” in an edge of the base of the jet, as is
  typical for previously-observed X-ray jets. We examined SDO/AIA EUV
  images of each of the jets over multiple AIA channels, including
  304 Å, which detects chromospheric emissions, and 171, 193, and
  211 Å, which detect cooler-coronal emissions. We find the jets to
  result from eruptions of miniature (size &lt;~10 arcsec) filaments
  from the bases of the jets. Much of the erupting-filament material
  forms a chromospheric-temperature jet. In the cool-coronal channels,
  often the filament appears in absorption and the hotter EUV component
  of the jet appears in emission. The jet bright point forms at the
  location from which the miniature filament erupts, analogous to the
  formation of a standard solar flare arcade in the wake of the eruption
  of a typical larger-scalechromospheric filament. The spire of the jet
  forms on open field lines that presumably have undergone interchange
  reconnection with the erupting field that envelops and carries the
  miniature filament. Thus these X-ray jets and their bright points are
  made by miniature filament eruptions via “internal” and “external”
  reconnection of the erupting field. This is consistent with what we
  found for the onset of an on-disk coronal jet we examined in Adams et
  al. (2014). This work was supported by funding from NASA/LWS, Hinode,
  and ISSI.

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Title: A Prominence/filament eruption triggered by eight homologous
    flares
Authors: Panesar, Navdeep K.; Sterling, Alphonse; Innes, Davina;
   Moore, Ronald
2015TESS....140805P    Altcode:
  Eight homologous flares occurred in active region NOAA 11237 over 16 -
  17 June 2011. A prominence system with a surrounding coronal cavity
  was adjacent to, but still magnetically connected to the active
  region. The eight eruptions expelled hot material from the active
  region into the prominence/filament cavity system (PFCS) where the
  ejecta became confined. We mainly aim to diagnose the 3D dynamics of
  the PFCS during the series of eight homologous eruptions by using data
  from two instruments: SDO/AIA and STEREO/EUVI-B, covering the Sun from
  two directions. The field containing the ejected hot material interacts
  with the PFCS and causes it to inflate, resulting in a discontinuous
  rise of the prominence/filament approximately in steps with the
  homologous eruptions. The eighth eruption triggers the PFCS to move
  outward slowly, accompanied by a weak coronal dimming. Subsequently the
  prominence/filament material drains to the solar surface. This PFCS
  eruption evidently slowly opens field overlying the active region,
  which results in a final ‘ejective’ eruption from the core of
  the active region. A strong dimming appears adjacent to the final
  eruption’s flare loops in the EUVI-B images, followed by a CME. We
  propose that the eight homologous flares gradually disrupted the PFCS
  and removed the overlying field above the active region, leading to
  the CME via the ‘lid removal’ mechanism.

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Title: More Macrospicule Jets in On-Disk Coronal Holes
Authors: Adams, Mitzi; Sterling, Alphonse; Moore, Ronald
2015TESS....120301A    Altcode:
  We examine the magnetic structure and dynamics of multiple jets found
  in coronal holes close to or at disk center. All data are from the
  Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic
  Imager (HMI) of the Solar Dynamics Observatory (SDO). We report on
  observations of about ten jets in an equatorial coronal hole spanning
  2011 February 27 and 28. We show the evolution of these jets in AIA 193
  Å, examine the magnetic field configuration and flux changes in the
  jet area, and discuss the probable trigger mechanism of these events. We
  reported on another jet in this same coronal hole on 2011 February 27,
  ~13:04 UT (Adams et al 2014, ApJ, 783: 11). That jet is a previously
  unrecognized variety of blowout jet, in which the base-edge bright
  point is a miniature filament-eruption flare arcade made by internal
  reconnection of the legs of the erupting field. In contrast, in the
  presently-accepted "standard" picture for blowout jets, the base-edge
  bright point is made by interchange reconnection of initially-closed
  erupting jet-base field with ambient open field. This poster presents
  further evidence of the production of the base-edge bright point in
  blowout jets by internal reconnection. Our observations suggest that
  most of the bigger and brighter EUV jets in coronal holes are blowout
  jets of the new-found variety.

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Title: Reconnection and Spire Drift in Coronal Jets
Authors: Moore, Ronald; Sterling, Alphonse; Falconer, David
2015TESS....140702M    Altcode:
  It is observed that there are two morphologically-different kinds of
  X-ray/EUV jets in coronal holes: standard jets and blowout jets. In
  both kinds: (1) in the base of the jet there is closed magnetic
  field that has one foot in flux of polarity opposite that of the
  ambient open field of the coronal hole, and (2) in coronal X-ray/EUV
  images of the jet there is typically a bright nodule at the edge
  of the base. In the conventional scenario for jets of either kind,
  the bright nodule is a compact flare arcade, the downward product of
  interchange reconnection of closed field in the base with impacted
  ambient open field, and the upper product of this reconnection is the
  jet-outflow spire. It is also observed that in most jets of either
  kind the spire drifts sideways away from the bright nodule. We present
  the observed bright nodule and spire drift in an example standard
  jet and in two example blowout jets. With cartoons of the magnetic
  field and its reconnection in jets, we point out: (1) if the bright
  nodule is a compact flare arcade made by interchange reconnection,
  then the spire should drift toward the bright nodule, and (2) if
  the bright nodule is instead a compact flare arcade made, as in a
  filament-eruption flare, by internal reconnection of the legs of the
  erupting sheared-field core of a lobe of the closed field in the base,
  then the spire, made by the interchange reconnection that is driven on
  the outside of that lobe by the lobe’s internal convulsion, should
  drift away from the bright nodule. Therefore, from the observation
  that the spire usually drifts away from the bright nodule, we infer:
  (1) in X-ray/EUV jets of either kind in coronal holes the interchange
  reconnection that generates the jet-outflow spire usually does not make
  the bright nodule; instead, the bright nodule is made by reconnection
  inside erupting closed field in the base, as in a filament eruption,
  the eruption being either a confined eruption for a standard jet or
  a blowout eruption (as in a CME) for a blowout jet, and (2) in this
  respect, the conventional reconnection picture for the bright nodule in
  coronal jets is usually wrong for observed coronal jets of either kind.

---------------------------------------------------------
Title: Exploring Euv Spicules Using 304 Ang He II Data from SDO/AIA
Authors: Snyder, I. R.; Sterling, A. C.; Falconer, D. A.; Moore, R. L.
2014AGUFMSH51C4179S    Altcode:
  We present results from an exploratory study of He II 304 ŠEUV
  spicules at the limb of the Sun. We also measured properties of
  one macrospicule; macrospicules are longer than most spicules, and
  much broader in width than spicules. We use high-cadence (12 sec)
  and high-resolution (0.6 arcsec pixels) data from the Atmospheric
  Imaging Array (AIA) instrument on the Solar Dynamic Observatory
  (SDO). All of the observed events occurred near the solar north pole,
  in quiet-Sun or coronal-hole environments. We examined the maximum
  lengths, maximum rise velocities, and lifetimes of about 30 EUV spicules
  and the macrospicule. For the bulk of the EUV spicules the ranges of
  these quantities are respectively ~10,000----40,000 km, 20---100 km/s,
  and ~100--- ~600 sec. For the macrospicule the corresponding quantities
  are respectively ~60,000 km, ~130 km/s, and ~1800 sec, which is typical
  of macrospicules measured by other workers. Therefore macrospicules
  are taller, longer-lived, and faster than most EUV spicules. The
  rise profiles of both the spicules and the macrospicules fit well to
  a second-order ("parabolic”) trajectory, although the acceleration
  was often weaker than that of solar gravity in the profiles fitted to
  the trajectories. Our macrospicule also had an obvious brightening at
  its base at birth, whereas such brightenings were not apparent for
  the EUV spicules. Most of the EUV spicules remained visible during
  their decent back to the solar surface, although a small percentage
  of the spicules and the macrospicule faded out before falling back
  to the surface. Our sample of macrospicules is not yet large enough
  to address whether they are scaled-up versions of EUV spicules, or
  independent phenomena. A.C.S. and R.L.M. were supported by funding from
  the Heliophysics Division of NASA's Science Mission Directorate through
  the Living With a Star Targeted Research and Technology Program, and
  the Hinode Project. I.R.S. was supported by NSF's Research Experience
  for Undergraduates Program.

---------------------------------------------------------
Title: Macrospicule Jets in On-Disk Coronal Holes
Authors: Adams, M.; Sterling, A. C.; Moore, R. L.
2014AGUFMSH51C4178A    Altcode:
  We examine the magnetic structure and dynamics of multiple jets found
  in coronal holes close to or on disk center. All data are from the
  Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic
  Imager (HMI) of the Solar Dynamics Observatory (SDO). We report on
  observations of ten jets in an equatorial coronal hole from 2011
  February 27 and multiple jets found in equatorial coronal holes
  on these dates: 2010-June-4, 2012-March-13, 2013-May 29-2013, and
  2014-February-24. We will show in detail the evolution of the jets
  and will compare the magnetic field arrangement and probable trigger
  mechanism of these events to those of a specific macrospicule jet
  observed on 2011 February 27. We recently discovered that this jet is
  a previously-unrecognized variety of blowout jet (Adams et al 2014,
  ApJ, 783: 11). In this variety, the reconnection bright point is not
  made by interchange reconnection of initially-closed erupting field
  in the base of the jet with ambient open field but is a miniature
  filament-eruption flare arcade made by internal reconnection of the
  legs of the erupting field.

---------------------------------------------------------
Title: Exploring He II 304 Å Spicules and Macrospicules at the
    Solar Limb
Authors: Sterling, A. C.; Snyder, I. R.; Falconer, D. A.; Moore, R. L.
2014AGUFMSH53D..04S    Altcode:
  We present results from a study of He II 304 Ang spicules and
  macrospiculesobserved at the limb of the Sun in 304 Ang channel image
  sequences from theAtmospheric Imaging Assembly (AIA) on the Solar
  Dynamics Observatory (SDO). Thesedata have both high spatial (0.6 arcsec
  pixels) and temporal (12 s) resolution. All of the observed events
  occurred in quiet or coronal hole regions near the solarpole. He II 304
  Ang spicules and macrospicules are both transient jet-likefeatures,
  with the macrospicules being wider and having taller maximum heights
  thanthe spicules. We looked for characteristics of the populations
  of these twophenomena that might indicate whether they have the same
  initiation mechanisms. Weexamine the maximum heights, time-averaged
  rise velocities, and lifetimes of about30 spicules and about five
  macrospicules. For the spicules, these quantities are,respectively,
  ~10,000----40,000 km, 20---100 km/s, and a few 100--- ~600 sec. Forthe
  macrospicules the corresponding properties are &gt;~60,000 km, &gt;~55
  km/s, andlifetimes of &gt;~1800 sec. Therefore the macrospicules have
  velocities comparable tothose of the fastest spicules and live longer
  than the spicules. The leading-edgetrajectories of both the spicules
  and the macrospicules match well a second-order(“parabolic”)
  profile, although the acceleration in the fitted profiles is
  generally weaker than that of solar gravity. The macrospicules also
  have obviousbrightenings at their bases at their birth, while such
  brightenings are notapparent for most of the spicules. Our findings are
  suggestive of the twophenomena possibly having different initiation
  mechanisms, but this is not yetconclusive. A.C.S. and R.L.M. were
  supported by funding from the HeliophysicsDivision of NASA's Science
  Mission Directorate through the Living With a StarTargeted Research
  and Technology Program, and the Hinode Project. I.R.S. wassupported
  by NSF's Research Experience for Undergraduates Program.

---------------------------------------------------------
Title: Birth, Life, and Death of a Solar Coronal Plume
Authors: Pucci, Stefano; Poletto, Giannina; Sterling, Alphonse C.;
   Romoli, Marco
2014ApJ...793...86P    Altcode:
  We analyze a solar polar-coronal-hole (CH) plume over its entire
  ≈40 hr lifetime, using high-resolution Solar Dynamic Observatory
  Atmospheric Imaging Assembly (AIA) data. We examine (1) the plume's
  relationship to a bright point (BP) that persists at its base, (2)
  plume outflows and their possible contribution to the solar wind
  mass supply, and (3) the physical properties of the plume. We find
  that the plume started ≈2 hr after the BP first appeared and became
  undetectable ≈1 hr after the BP disappeared. We detected radially
  moving radiance variations from both the plume and from interplume
  regions, corresponding to apparent outflow speeds ranging over
  ≈(30-300) km s<SUP>-1</SUP> with outflow velocities being higher
  in the "cooler" AIA 171 Å channel than in the "hotter" 193 Å and
  211 Å channels, which is inconsistent with wave motions; therefore,
  we conclude that the observed radiance variations represent material
  outflows. If they persist into the heliosphere and plumes cover ≈10%
  of a typical CH area, these flows could account for ≈50% of the
  solar wind mass. From a differential emission measure analysis of the
  AIA images, we find that the average electron temperature of the plume
  remained approximately constant over its lifetime, at T <SUB>e</SUB>
  ≈ 8.5 × 10<SUP>5</SUP> K. Its density, however, decreased with the
  age of the plume, being about a factor of three lower when the plume
  faded compared to when it was born. We conclude that the plume died
  due to a density reduction rather than to a temperature decrease.

---------------------------------------------------------
Title: New Aspects of a Lid-removal Mechanism in the Onset of an
    Eruption Sequence that Produced a Large Solar Energetic Particle
    (SEP) Event
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.;
   Knox, Javon M.
2014ApJ...788L..20S    Altcode:
  We examine a sequence of two ejective eruptions from a single active
  region on 2012 January 23, using magnetograms and EUV images from the
  Solar Dynamics Observatory's (SDO) Helioseismic and Magnetic Imager
  (HMI) and Atmospheric and Imaging Assembly (AIA), and EUV images from
  STEREO/EUVI. This sequence produced two coronal mass ejections (CMEs)
  and a strong solar energetic particle event (SEP); here we focus on
  the magnetic onset of this important space weather episode. Cheng
  et al. showed that the first eruption's ("Eruption 1") flux rope was
  apparent only in "hotter" AIA channels, and that it removed overlying
  field that allowed the second eruption ("Eruption 2") to begin via
  ideal MHD instability; here we say that Eruption 2 began via a "lid
  removal" mechanism. We show that during Eruption 1's onset, its flux
  rope underwent a "tether weakening" (TW) reconnection with field that
  arched from the eruption-source active region to an adjacent active
  region. Standard flare loops from Eruption 1 developed over Eruption
  2's flux rope and enclosed filament, but these overarching new loops
  were unable to confine that flux rope/filament. Eruption 1's flare
  loops, from both TW reconnection and standard-flare-model internal
  reconnection, were much cooler than Eruption 2's flare loops (GOES
  thermal temperatures of ~7.5 MK and 9 MK, compared to ~14 MK). The
  corresponding three sequential GOES flares were, respectively, due to TW
  reconnection plus earlier phase Eruption 1 tether-cutting reconnection,
  Eruption 1 later-phase tether-cutting reconnection, and Eruption 2
  tether-cutting reconnection.

---------------------------------------------------------
Title: New Aspects of a Lid-Removal Mechanism in the Onset of a
    SEP-Producing Eruption Sequence
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David;
   Knox, Javon M
2014AAS...22421202S    Altcode:
  We examine a sequence of two ejective eruptions from a single active
  region on 2012 January 23, using magnetograms and EUV images from
  SDO/HMI and SDO/AIA, and EUV images from STEREO. Cheng et al. (2013)
  showed that the first eruption's (“Eruption 1”) flux rope was apparent
  only in “hotter” AIA channels, and that it removed overlying field
  that allowed the second eruption (“Eruption 2”) to begin via ideal
  MHD instability; here we say Eruption 2 began via a “lid removal”
  mechanism. We show that during Eruption-1's onset, its flux rope
  underwent “tether weakening” (TW) reconnection with the field of an
  adjacent active region. Standard flare loops from Eruption 1 developed
  over Eruption-2's flux rope and enclosed filament, but these overarching
  new loops were unable to confine that flux rope/filament. Eruption-1's
  flare loops, from both TW reconnection and standard-flare-model internal
  reconnection, were much cooler than Eruption-2's flare loops (GOES
  thermal temperatures of ~9 MK compared to ~14 MK). This eruption
  sequence produced a strong solar energetic particle (SEP) event
  (10 MeV protons, &gt;10^3 pfu for 43 hrs), apparently starting when
  Eruption-2's CME blasted through Eruption-1's CME at 5---10 R_s. This
  occurred because the two CMEs originated in close proximity and in
  close time sequence: Eruption-1's fast rise started soon after the TW
  reconnection; the lid removal by Eruption-1's ejection triggered the
  slow onset of Eruption 2; and Eruption-2's CME, which started ~1 hr
  later, was three times faster than Eruption-1's CME.

---------------------------------------------------------
Title: Magnetic Untwisting in Jets that Go into the Outer Solar
    Corona in Polar Coronal Holes
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David
2014AAS...22440803M    Altcode:
  We present results from a study of 14 jets that were observed in SDO/AIA
  EUV movies to erupt in the Sun’s polar coronal holes. These jets
  were similar to the many other jets that erupt in coronal holes, but
  reached higher than the vast majority, high enough to be observed in the
  outer corona beyond 2 solar radii from Sun center by the SOHO/LASCO/C2
  coronagraph. We illustrate the characteristic structure and motion of
  these high-reaching jets by showing observations of two representative
  jets. We find that (1) the speed of the jet front from the base of the
  corona out to 2-3 solar radii is typically several times the sound speed
  in jets in coronal holes, (2) each high-reaching jet displays unusually
  large rotation about its axis (spin) as it erupts, and (3) in the outer
  corona, many jets display lateral swaying and bending of the jet axis
  with an amplitude of a few degrees and a period of order 1 hour. From
  these observations we infer that these jets are magnetically driven,
  propose that the driver is a magnetic-untwisting wave that is basically
  a large-amplitude (non-linear) torsional Alfven wave that is put into
  the open magnetic field in the jet by interchange reconnection as the
  jet erupts, and estimate that the magnetic-untwisting wave loses most
  of its energy before reaching the outer corona. These observations of
  high-reaching coronal jets suggest that the torsional magnetic waves
  observed in Type-II spicules can similarly dissipate in the corona and
  thereby power much of the coronal heating in coronal holes and quiet
  regions. This work is funded by the NASA/SMD Heliophysics Division’s
  Living With a Star Targeted Research &amp; Technology Program.

---------------------------------------------------------
Title: A Small-scale Eruption Leading to a Blowout Macrospicule Jet
    in an On-disk Coronal Hole
Authors: Adams, Mitzi; Sterling, Alphonse C.; Moore, Ronald L.; Gary,
   G. Allen
2014ApJ...783...11A    Altcode:
  We examine the three-dimensional magnetic structure and dynamics
  of a solar EUV-macrospicule jet that occurred on 2011 February 27
  in an on-disk coronal hole. The observations are from the Solar
  Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and
  the SDO Helioseismic and Magnetic Imager (HMI). The observations
  reveal that in this event, closed-field-carrying cool absorbing
  plasma, as in an erupting mini-filament, erupted and opened,
  forming a blowout jet. Contrary to some jet models, there was no
  substantial recently emerged, closed, bipolar-magnetic field in the
  base of the jet. Instead, over several hours, flux convergence and
  cancellation at the polarity inversion line inside an evolved arcade
  in the base apparently destabilized the entire arcade, including its
  cool-plasma-carrying core field, to undergo a blowout eruption in the
  manner of many standard-sized, arcade-blowout eruptions that produce
  a flare and coronal mass ejection. Internal reconnection made bright
  "flare" loops over the polarity inversion line inside the blowing-out
  arcade field, and external reconnection of the blowing-out arcade field
  with an ambient open field made longer and dimmer EUV loops on the
  outside of the blowing-out arcade. That the loops made by the external
  reconnection were much larger than the loops made by the internal
  reconnection makes this event a new variety of blowout jet, a variety
  not recognized in previous observations and models of blowout jets.

---------------------------------------------------------
Title: The contribution of X-ray polar blowout jets to the solar
    wind mass and energy
Authors: Poletto, Giannina; Sterling, Alphonse C.; Pucci, Stefano;
   Romoli, Marco
2014IAUS..300..239P    Altcode:
  Blowout jets constitute about 50% of the total number of X-ray jets
  observed in polar coronal holes. In these events, the base magnetic
  loop is supposed to blow open in what is a scaled-down representation
  of two-ribbon flares that accompany major coronal mass ejections
  (CMEs): indeed, miniature CMEs resulting from blowout jets have been
  observed. This raises the question of the possible contribution of
  this class of events to the solar wind mass and energy flux. Here we
  make a first crude evaluation of the mass contributed to the wind and
  of the energy budget of the jets and related miniature CMEs, under
  the assumption that small-scale events behave as their large-scale
  analogs. This hypothesis allows us to adopt the same relationship
  between jets and miniature-CME parameters that have been shown to hold
  in the larger-scale events, thus inferring the values of the mass and
  kinetic energy of the miniature CMEs, currently not available from
  observations. We conclude our work estimating the mass flux and the
  energy budget of a blowout jet, and giving a crude evaluation of the
  role possibly played by these events in supplying the mass and energy
  that feeds the solar wind.

---------------------------------------------------------
Title: Physical Parameters of Standard and Blowout Jets
Authors: Pucci, Stefano; Poletto, Giannina; Sterling, Alphonse C.;
   Romoli, Marco
2013ApJ...776...16P    Altcode:
  The X-ray Telescope on board the Hinode mission revealed the
  occurrence, in polar coronal holes, of much more numerous jets than
  previously indicated by the Yohkoh/Soft X-ray Telescope. These plasma
  ejections can be of two types, depending on whether they fit the
  standard reconnection scenario for coronal jets or if they include a
  blowout-like eruption. In this work, we analyze two jets, one standard
  and one blowout, that have been observed by the Hinode and STEREO
  experiments. We aim to infer differences in the physical parameters
  that correspond to the different morphologies of the events. To this
  end, we adopt spectroscopic techniques and determine the profiles of
  the plasma temperature, density, and outflow speed versus time and
  position along the jets. The blowout jet has a higher outflow speed,
  a marginally higher temperature, and is rooted in a stronger magnetic
  field region than the standard event. Our data provide evidence for
  recursively occurring reconnection episodes within both the standard
  and the blowout jet, pointing either to bursty reconnection or to
  reconnection occurring at different locations over the jet lifetimes. We
  make a crude estimate of the energy budget of the two jets and show
  how energy is partitioned among different forms. Also, we show that
  the magnetic energy that feeds the blowout jet is a factor of 10 higher
  than the magnetic energy that fuels the standard event.

---------------------------------------------------------
Title: Magnetic Untwisting in Most Solar X-Ray Jets
Authors: Moore, Ronald L.; Sterling, A. C.; Falconer, D.; Robe, D. M.
2013SPD....4410304M    Altcode:
  From 54 X-ray jets observed in the polar coronal holes by Hinode’s
  X-Ray Telescope (XRT) during coverage in movies from Solar Dynamic
  Observatory’s Atmospheric Imaging Assembly (AIA) taken in its
  He II 304 Å band at a cadence of 12 s, we have established a basic
  characteristic of solar X-ray jets: untwisting motion in the spire. In
  this presentation, we show the progression of few of these X-ray jets
  in XRT images and track their untwisting in AIA He II images. From
  their structure displayed in their XRT movies, 19 jets were evidently
  standard jets made by interchange reconnection of the magnetic-arcade
  base with ambient open field, 32 were evidently blowout jets made by
  blowout eruption of the base arcade, and 3 were of ambiguous form. As
  was anticipated from the &gt;10,000 km span of the base arcade in
  most polar X-ray jets and from the disparity of standard jets and
  blowout jets in their magnetic production, few of the standard X-ray
  jets (3 of 19) but nearly all of the blowout X-ray jets (29 of 32)
  carried enough cool (T ~ 10^5 K) plasma to be seen in their He II
  movies. In the 32 X-ray jets that showed a cool component, the He II
  movies show 10-100 km/s untwisting motions about the axis of the spire
  in all 3 standard jets and in 26 of the 29 blowout jets. Evidently,
  the open magnetic field in nearly all blowout X-ray jets and probably
  in most standard X-ray jets carries transient twist. This twist
  apparently relaxes by propagating out along the open field as a
  torsional wave. High-resolution spectrograms and Dopplergrams have
  shown that most Type-II spicules have torsional motions of 10-30
  km/s. Our observation of similar torsional motion in X-ray jets (1)
  strengthens the case for Type-II spicules being made in the same way
  as X-ray jets, by blowout eruption of a twisted magnetic arcade in the
  spicule base and/or by interchange reconnection of the twisted base
  arcade with the ambient open field, and hence (2) strengthens the case
  made by Moore et al (2011, ApJ, 731: L18) that the Sun's granule-size
  emerging magnetic bipoles, by making Type-II spicules, power the global
  corona and solar wind. This work was funded by NASA’s LWS TRT Program,
  NASA's Hinode Project, and NSF's REU Program.

---------------------------------------------------------
Title: An Automatic Detection Technique for Prominence Eruptions
    and Surges using SDO/AIA Images
Authors: Yashiro, Seiji; Gopalswamy, N.; Makela, P.; Akiyama, S.;
   Sterling, A. C.
2013SPD....44...99Y    Altcode:
  We present an automatic technique to detect and characterize eruptive
  events (EEs), e.g. prominence eruptions and surges, using SDO/AIA
  304 Å images. The technique works as follows. 1) The SDO 304 Å
  images are polar-transformed for easy handling of the outward motion
  of EEs and for saving computer resources. 2) The transformed images
  are divided by a background map, which is determined as the minimum
  intensity of each pixel during 24 hours. 3) The EEs are defined as a
  region in the ratio maps with pixels having a ratio &gt;2. Because a
  stationary prominence has relatively high background, the prominence
  is detected only when it moves. 4) Pattern recognition is performed to
  separate different EEs at different locations. 5) In successive images,
  two EEs with more than 50% of pixels overlapping are considered to
  be the same EE. 6) If the height of an EE increases monotonically
  in 5 successive images, we consider it as a reliable eruption. The
  technique detects 1428 prominence eruptions and 1921 surges from 2010
  May to 2012 December. The locations of PEs identified by this technique
  clearly indicated decayed onset of the maximum phase in the south with
  respect to the north. This work was supported by NASA Living with a
  Star TR&amp;T programAbstract (2,250 Maximum Characters): We present
  an automatic technique to detect and characterize eruptive events
  (EEs), e.g. prominence eruptions and surges, using SDO/AIA 304 Å
  images. The technique works as follows. 1) The SDO 304 Å images are
  polar-transformed for easy handling of the outward motion of EEs and
  for saving computer resources. 2) The transformed images are divided by
  a background map, which is determined as the minimum intensity of each
  pixel during 24 hours. 3) The EEs are defined as a region in the ratio
  maps with pixels having a ratio &gt;2. Because a stationary prominence
  has relatively high background, the prominence is detected only when it
  moves. 4) Pattern recognition is performed to separate different EEs at
  different locations. 5) In successive images, two EEs with more than 50%
  of pixels overlapping are considered to be the same EE. 6) If the height
  of an EE increases monotonically in 5 successive images, we consider it
  as a reliable eruption. The technique detects 1428 prominence eruptions
  and 1921 surges from 2010 May to 2012 December. The locations of PEs
  identified by this technique clearly indicated decayed onset of the
  maximum phase in the south with respect to the north. This work was
  supported by NASA Living with a Star TR&amp;T program

---------------------------------------------------------
Title: A Small-Scale Filament Eruption Leading to a Blowout
    Macrospicule Jet in an On-Disk Coronal Hole
Authors: Sterling, Alphonse C.; Adams, M.; Moore, R. L.; Tennant,
   A. F.; Gary, G. A.
2013SPD....44...17S    Altcode:
  We observe an eruptive jet that occurred in an on-disk solar coronal
  hole, using EUV images from the Solar Dynamics Observatory (SDO)
  Atmospheric Imaging Assembly (AIA), supplemented by magnetic data from
  the SDO Helioseismic and Magnetic Imager (HMI). This jet is similar to
  features variously called macrospicules or erupting minifilaments. After
  an initial pre-eruptive phase, a concentration of absorbing, cool
  material in the AIA images moves with a substantially-horizontal motion
  toward a region of open magnetic field, and subsequently jets out along
  that vertical field. Prior to and during the jet's ~20 min lifetime,
  the magnetic flux integrated over the local region shows flux changes
  of &amp;lt 20% of the background flux levels, with a time-averaged
  emergence rate of no more than &lt;3 × 10^15 Mx/s in the neighborhood
  of the jet. Contrary to some jet models, there was no substantial
  recently-emerged bipolar field in the base of the jet. Instead, there
  was an established evolving magnetic arcade that held mini-filament-like
  cool plasma in its core field. We propose that subtle evolution of the
  magnetic flux in and around this arcade destabilized its core field,
  as in some standard-sized arcade blowout eruptions that produce a flare
  and CME following the slow rise of a standard-sized filament in the
  core of the arcade. Closed field carrying the cool plasma erupted into
  the open field and formed the blowout jet, evidently at least partly
  by interchange reconnection with the open field. Internal reconnection
  made compact bright "flare" loops inside the blowing-out arcade, while,
  on the outside, interchange reconnection made longer and dimmer EUV
  "crinkle" loops. That the loops made by the external reconnection were
  considerably larger than the loops made by the internal reconnection
  makes this event a new variety of blowout jet, a variety not recognized
  in previous observations and models of blowout jets.

---------------------------------------------------------
Title: The 2012 Total Eclipse Expeditions in Queensland
Authors: Pasachoff, Jay M.; Babcock, B. A.; Lu, M.; Dantowitz, R.;
   Lucas, R.; Seiradakis, J. H.; Voulgaris, A.; Gaintatzis, P.; Steele,
   A.; Sterling, A. C.; Rusin, V.; Saniga, M.
2013SPD....44...51P    Altcode:
  A total eclipse swept across Queensland and other sites in northeastern
  Australia on the early morning of 14 November 2012, local time. We
  mounted equipment to observe coronal images and spectra during the
  approximately 2 minutes of totality, the former for comparison with
  spacecraft images and to fill in the doughnut of imaging not well
  covered with space coronagraphs. Matching weather statistics, viewing
  was spotty, and our best observations were from a last-minute inland
  site on the Tablelands, with some observations from a helicopter at 9000
  feet altitude over our original viewing site at Miallo. Only glimpses of
  the corona were visible at our Port Douglas and Trinity Beach, Cairns,
  locations, with totality obscured from our sites at Newell and Miallo,
  though some holes in the clouds provided coronal views from Palm Cove
  and elsewhere along the coast. Preliminary analysis of the spectra
  again shows Fe XIV stronger than Fe X, as in 2010 but not earlier,
  a sign of solar maximum, as was the coronal shape. An intriguing CME
  is discernible in the SE. Acknowledgments: We thank Terry Cuttle, Aram
  Friedman, Michael Kentrianakis, and Nicholas Weber for assistance and
  collaboration in Australia and Wendy Carlos for image processing. Our
  expedition was supported in part by NSF grant AGS-1047726 from Solar
  Terrestrial Research of the Atmospheric and Geospace Sciences Division,
  and by the Rob Spring Fund and Science Center funds at Williams
  College. ML was also supported in part by a Grant-In-Aid of Research
  from the National Academy of Sciences, administered by Sigma Xi, The
  Scientific Research Society (Grant ID: G20120315159311). VR and MS
  acknowledge support from projects VEGA 2/0003/13 and NGS-3139-12 of
  the National Geographic Society. We are grateful to K. Shiota (Japan)
  for kindly providing us with some of his 2012 eclipse coronal images.

---------------------------------------------------------
Title: The Cool Component and the Dichotomy, Lateral Expansion,
    and Axial Rotation of Solar X-Ray Jets
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David A.;
   Robe, Dominic
2013ApJ...769..134M    Altcode:
  We present results from a study of 54 polar X-ray jets that were
  observed in coronal X-ray movies from the X-ray Telescope on Hinode and
  had simultaneous coverage in movies of the cooler transition region (T
  ~ 10<SUP>5</SUP> K) taken in the He II 304 Å band of the Atmospheric
  Imaging Assembly (AIA) on Solar Dynamics Observatory. These dual
  observations verify the standard-jet/blowout-jet dichotomy of polar
  X-ray jets previously found primarily from XRT movies alone. In accord
  with models of blowout jets and standard jets, the AIA 304 Å movies
  show a cool (T ~ 10<SUP>5</SUP> K) component in nearly all blowout X-ray
  jets and in a small minority of standard X-ray jets, obvious lateral
  expansion in blowout X-ray jets but none in standard X-ray jets, and
  obvious axial rotation in both blowout X-ray jets and standard X-ray
  jets. In our sample, the number of turns of axial rotation in the
  cool-component standard X-ray jets is typical of that in the blowout
  X-ray jets, suggesting that the closed bipolar magnetic field in the
  jet base has substantial twist not only in all blowout X-ray jets but
  also in many standard X-ray jets. We point out that our results for
  the dichotomy, lateral expansion, and axial rotation of X-ray jets add
  credence to published speculation that type-II spicules are miniature
  analogs of X-ray jets, are generated by granule-size emerging bipoles,
  and thereby carry enough energy to power the corona and solar wind.

---------------------------------------------------------
Title: An upper limit to the solar wind mass loading by X-ray
    polar jets
Authors: Pucci, Stefano; Poletto, Giannina; Sterling, Alphonse C.;
   Romoli, Marco
2013AIPC.1539...62P    Altcode:
  Hinode observations of polar coronal holes revealed a larger population
  of X-ray jets than previously reported. Some of these comply with
  the standard reconnection model suggested by Shibata et al. (1992),
  others, likely analogous to CME eruptions and referred to as blow-out
  jets (e.g. Moore et al., 2010), show a more structured morphology. We
  present here two events, representative of the two jet categories, that
  have been observed by HINODE and STEREO in polar coronal holes. Their
  outward speed has been evaluated from high resolution images; also,
  because the jets have been observed in multiple filters, we have been
  able to derive, via spectroscopic techniques, their temperature and
  density evolution, both along the jets and in time. Knowledge of these
  parameters allows us to estimate the mass flux that jets of the two
  types transport to the solar wind and, assuming a given frequency of
  events, to infer a value for the wind mass loading contributed by polar
  jets. Because there are insufficient data to establish the percentage
  of ejections which eventually fall back to the Sun and because the
  jets we analyzed are probably among the more energetic within their
  respective class of events, the estimate we give is an upper limit to
  the jet wind mass loading.

---------------------------------------------------------
Title: Three 2012 Transits of Venus: From Earth, Jupiter, and Saturn
Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.;
   Edelman, E.; Reardon, K.; Widemann, T.; Tanga, P.; Dantowitz, R.;
   Silverstone, M. D.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson,
   P. D.; Willson, R. C.; Kopp, G. A.; Yurchyshyn, V. B.; Sterling,
   A. C.; Scherrer, P. H.; Schou, J.; Golub, L.; McCauley, P.; Reeves, K.
2013AAS...22131506P    Altcode:
  We observed the 2012 June 6/5 transit seen from Earth (E/ToV),
  simultaneously with Venus Express and several other spacecraft
  not only to study the Cytherean atmosphere but also to provide an
  exoplanet-transit analog. From Haleakala, the whole transit was visible
  in coronal skies; among our instruments was one of the world-wide Venus
  Twilight Experiment's nine coronagraphs. Venus's atmosphere became
  visible before first contact. SacPeak/IBIS provided high-resolution
  images at Hα/carbon-dioxide. Big Bear's NST also provided
  high-resolution observations of the Cytherean atmosphere and black-drop
  evolution. Our liaison with UH's Mees Solar Observatory scientists
  provided magneto-optical imaging at calcium and potassium. Solar
  Dynamics Observatory's AIA and HMI, and the Solar Optical Telescope
  (SOT) and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance
  measurements with ACRIMSAT and SORCE/TIM, were used to observe the
  event as an exoplanet-transit analog. On September 20, we imaged
  Jupiter for 14 Hubble Space Telescope orbits, centered on a 10-hour
  ToV visible from Jupiter (J/ToV), as an exoplanet-transit analog in
  our own solar system, using Jupiter as an integrating sphere. Imaging
  was good, although much work remains to determine if we can detect
  the expected 0.01% solar irradiance decrease at Jupiter and the even
  slighter differential effect between our violet and near-infrared
  filters caused by Venus's atmosphere. We also give a first report on our
  currently planned December 21 Cassini UVIS observations of a transit of
  Venus from Saturn (S/ToV). Our E/ToV expedition was sponsored by the
  Committee for Research and Exploration/National Geographic Society;
  supplemented: NASA/AAS's Small Research Grant Program. We thank Rob
  Ratkowski, Stan Truitt, Rob Lucas, Aram Friedman, and Eric Pilger
  '82 at Haleakala, and Joseph Gangestad '06 at Big Bear for assistance,
  and Lockheed Martin Solar and Astrophysics Lab and Hinode science and
  operations teams for support for coordinated observations with NASA
  satellites. Our J/ToV observations were based on observations made
  with HST, operated by AURA, Inc., under NASA contract NAS 5-26555;
  these observations are associated with program #13067.

---------------------------------------------------------
Title: Observations from SDO, Hinode, and STEREO of a Twisting and
    Writhing Start to a Solar-filament-eruption Cascade
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Hara, Hirohisa
2012ApJ...761...69S    Altcode:
  We analyze data from SDO (AIA, HMI), Hinode (SOT, XRT, EIS), and STEREO
  (EUVI) of a solar eruption sequence of 2011 June 1 near 16:00 UT,
  with an emphasis on the early evolution toward eruption. Ultimately,
  the sequence consisted of three emission bursts and two filament
  ejections. SDO/AIA 304 Å images show absorbing-material strands
  initially in close proximity which over ~20 minutes form a
  twisted structure, presumably a flux rope with ~10<SUP>29</SUP>
  erg of free energy that triggers the resulting evolution. A jump
  in the filament/flux rope's displacement (average velocity ~20 km
  s<SUP>-1</SUP>) and the first burst of emission accompanies the
  flux-rope formation. After ~20 more minutes, the flux rope/filament
  kinks and writhes, followed by a semi-steady state where the flux
  rope/filament rises at (~5 km s<SUP>-1</SUP>) for ~10 minutes. Then
  the writhed flux rope/filament again becomes MHD unstable and violently
  erupts, along with rapid (50 km s<SUP>-1</SUP>) ejection of the filament
  and the second burst of emission. That ejection removed a field that
  had been restraining a second filament, which subsequently erupts as
  the second filament ejection accompanied by the third (final) burst of
  emission. Magnetograms from SDO/HMI and Hinode/SOT, and other data,
  reveal several possible causes for initiating the flux-rope-building
  reconnection, but we are not able to say which is dominant. Our
  observations are consistent with magnetic reconnection initiating the
  first burst and the flux-rope formation, with MHD processes initiating
  the further dynamics. Both filament ejections are consistent with the
  standard model for solar eruptions.

---------------------------------------------------------
Title: Production of High-Temperature Plasmas During the Early Phases
    of a C9.7 Flare. II. Bi-directional Flows Suggestive of Reconnection
    in a Pre-flare Brightening Region
Authors: Watanabe, T.; Hara, H.; Sterling, A. C.; Harra, L. K.
2012SoPh..281...87W    Altcode: 2012SoPh..tmp..185W
  The 6 June 2007 16:55 UT flare was well observed with high time-cadence
  sparse raster scans by the EUV Imaging Spectrometer (EIS) on board
  the Hinode spacecraft. The observation covers an active region area
  of 240 arcsec × 240 arcsec with the 1 arcsec slit in about 160 seconds.

---------------------------------------------------------
Title: The 2012 Transit of Venus for Cytherean Atmospheric Studies
    and as an Exoplanet Analog
Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.;
   Reardon, K. P.; Widemann, T.; Tanga, P.; Dantowitz, R.; Willson,
   R.; Kopp, G.; Yurchyshyn, V.; Sterling, A.; Scherrer, P.; Schou, J.;
   Golub, L.; Reeves, K.
2012DPS....4450806P    Altcode:
  We worked to assemble as complete a dataset as possible for the
  Cytherean atmosphere in collaboration with Venus Express in situ
  and to provide an analog of spectral and total irradiance exoplanet
  measurements. From Haleakala, the whole transit was visible in
  coronal skies; our B images showed the evolution of the visibility
  of Venus's atmosphere and of the black-drop effect, as part of the
  Venus Twilight Experiment's 9 coronagraphs distributed worldwide
  with BVRI. We imaged the Cytherean atmosphere over two minutes before
  first contact, with subarcsecond resolution, with the coronagraph and
  a separate refractor. The IBIS imaging spectrometer at Sacramento
  Peak Observatory at H-alpha and carbon-dioxide also provided us
  high-resolution imaging. The NST of Big Bear Solar Observatory
  also provided high-resolution vacuum observations of the Cytherean
  atmosphere and black drop evolution. Our liaison with UH's Mees Solar
  Observatory scientists provided magneto-optical imaging at calcium
  and potassium. Spaceborne observations included the Solar Dynamics
  Observatory's AIA and HMI, and the Solar Optical Telescope (SOT)
  and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance
  measurements with ACRIMSAT and SORCE/TIM, to characterize the
  event as an exoplanet-transit analog. Our expedition was sponsored
  by the Committee for Research and Exploration/National Geographic
  Society. Some of the funds for the carbon-dioxide filter for IBIS were
  provided by NASA through AAS's Small Research Grant Program. We thank
  Rob Lucas, Aram Friedman, and Eric Pilger '82 for assistance with
  Haleakala observing, Rob Ratkowski of Haleakala Amateur Astronomers
  for assistance with equipment and with the site, Stan Truitt for the
  loan of his Paramount ME, and Steve Bisque/Software Bisque for TheSky
  X controller. We thank Joseph Gangestad '06 of Aerospace Corp., a
  veteran of our 2004 expedition, for assistance at Big Bear. We thank
  the Lockheed Martin Solar and Astrophysics Laboratory and Hinode
  science and operations teams for planning and support.

---------------------------------------------------------
Title: Solar Spicules near and at the Limb, Observed from Hinode
Authors: Sterling, A. C.; Moore, R. L.
2012ASPC..454...87S    Altcode:
  Solar spicules appear as narrow jets emanating from the chromosphere and
  extending into the corona. They have been observed for over a hundred
  years, mainly in chromospheric spectral lines such as H-alpha. Because
  they are at the limit of visibility of ground-based instruments,
  their nature has long been a puzzle. In recent years however, vast
  progress has been made in understanding them both theoretically
  and observationally, as spicule studies have undergone a revolution
  because of the superior resolution and time cadence of ground-based
  and space-based instruments. Even more rapid progress is currently
  underway, due to the Solar Optical Telescope (SOT) instrument on the
  Hinode spacecraft. Here we give a synopsis of our recent findings from
  a movie of sharpened images from the Hinode SOT Ca II filtergraph of
  spicules at and near the limb in a polar coronal hole.

---------------------------------------------------------
Title: Observational Evidence for Interaction Between X-ray Jets
    and Multiple Bright Points
Authors: Pucci, S.; Poletto, G.; Sterling, A.; Romoli, M.
2012ASPC..456..217P    Altcode:
  The Hinode X-ray telescope (XRT) observed in November 2007 the Northen
  polar Coronal Hole (CH) over extended time periods. Among these we
  selected two 20 hours long time intervals and carried out a photometric
  analysis of several X-ray Bright Points (BPs), within a selected area,
  aiming at ascertaining whether there is any correlation between the
  BPs intensity fluctuations and the occurrence of jets originating
  within this area. Our results indicate that jets result from magnetic
  connectivity changes that also produced BP variability: the interaction
  between BPs and jets may be interpreted as the small scale version of
  the Active Regions phenomena where flares and eruptions are initiated
  by interacting bipoles.

---------------------------------------------------------
Title: Physical Parameters of a Blowout Jet Observed by HINODE
    and STEREO/EUVI
Authors: Pucci, S.; Poletto, G.; Sterling, A.; Romoli, M.
2012ASPC..456..219P    Altcode:
  The present work aims at identifying a typical blowout jet and
  inferring its physical parameters. To this end, we present a preliminary
  multi-instrument analysis of the bright X-ray jet that occurred in the
  north polar coronal hole on Nov. 3, 2007, at 11:50 UT. The jet shows
  the typical characteristics of “blowout jets” (Moore et al. 2010),
  and was observed by Hinode/X-Ray Telescope (XRT) and by Stereo/Extreme
  UltraViolett Imager (EUVI) and COR1. Temperatures and Emission Measures
  (EMs) of the jet have been derived from the EUVI A data via the filter
  ratio technique in the pre-event, near maximum and in the post-maximum
  phases. Temperatures and EMs inferred from EUVI data are then used to
  calculate the predicted XRT Al-poly intensity: predicted values are
  compared with observed values and found to be consistent.

---------------------------------------------------------
Title: The Limit of Magnetic-Shear Energy in Solar Active Regions
Authors: Moore, Ronald L.; Falconer, D. A.; Sterling, A. C.
2012AAS...22020438M    Altcode:
  It has been found previously, by measuring from active-region
  magnetograms a proxy of the free energy in the active region’s
  magnetic field, (1) that there is a sharp upper limit to the free energy
  the field can hold that increases with the amount of magnetic field
  in the active region, the active region’s magnetic flux content,
  and (2) that most active regions are near this limit when their field
  explodes in a CME/flare eruption. That is, explosive active regions are
  concentrated in a main-sequence path bordering the free-energy-limit
  line in (flux content, free-energy proxy) phase space. Here we present
  evidence that specifies the underlying magnetic condition that gives
  rise to the free-energy limit and the accompanying main sequence of
  explosive active regions. Using a suitable free energy proxy measured
  from vector magnetograms of 44 active regions, we find evidence that
  (1) in active regions at and near their free-energy limit, the ratio of
  magnetic-shear free energy to the non-free magnetic energy the potential
  field would have is of order 1 in the core field, the field rooted along
  the neutral line, and (2) this ratio is progressively less in active
  regions progressively farther below their free-energy limit. Evidently,
  most active regions in which this core-field energy ratio is much less
  than 1 cannot be triggered to explode; as this ratio approaches 1,
  most active regions become capable of exploding; and when this ratio
  is 1, most active regions are compelled to explode. <P />This work was
  funded by NASA’s Science Mission Directorate through the Heliophysics
  Guest Investigators Program, the Hinode Project, and the Living With
  a Star Targeted Research &amp; Technology Program.

---------------------------------------------------------
Title: Observations from SDO and Hinode of a Twisting and Writhing
    Start to a Solar-filament-eruption Cascade
Authors: Sterling, Alphonse C.; Moore, R. L.
2012AAS...22050802S    Altcode:
  We analyze data from SDO and hinode of a solar eruption sequence of
  1 June 2011 near 16:00 UT, with emphasis on the early evolution
  toward eruption. Ultimately, the sequence consisted of three
  emission bursts and two filament ejections. SDO/AIA 304 Ang images
  show absorbing-material strands initially in close proximity that
  over 20 min form a twisted structure, presumably a flux rope with
  10<SUP>29 </SUP>ergs of free energy that triggers the resulting
  evolution. A jump in the filament/flux rope's height (average velocity
  20 km s<SUP>-1</SUP>) and the first burst of emission accompanies
  the flux-rope formation. After 20 min more, the flux rope/filament
  kinks and writhes, followed by a semi-steady state where the flux
  rope/filament rises at ( 5 km s<SUP>-1</SUP>) for 10 min. Then the
  writhed flux rope/filament again becomes MHD unstable and violently
  erupts, along with rapid (&gt; 50 km s<SUP>-1</SUP>) ejection of the
  filament and the second burst of emission. That ejection removed field
  that had been restraining a second filament, which subsequently erupts
  as the second filament ejection accompanied by the third (final) burst
  of emission. Magnetograms from SDO/HMI and hinode/SOT, and other data,
  reveal several possible causes for initiating the flux-rope-building
  reconnection, but we are not able to say which is dominant. Our
  observations are consistent with tether-cutting reconnection initiating
  the first burst and the flux-rope formation, with MHD processes
  initiating the further dynamics. Both filament ejections are consistent
  with the standard model for solar eruptions. NASA supported this work
  through its Heliophysics program.

---------------------------------------------------------
Title: The Limit of Magnetic-shear Energy in Solar Active Regions
Authors: Moore, Ronald L.; Falconer, David A.; Sterling, Alphonse C.
2012ApJ...750...24M    Altcode:
  It has been found previously, by measuring from active-region
  magnetograms a proxy of the free energy in the active region's magnetic
  field, (1) that there is a sharp upper limit to the free energy the
  field can hold that increases with the amount of magnetic field
  in the active region, the active region's magnetic flux content,
  and (2) that most active regions are near this limit when their
  field explodes in a coronal mass ejection/flare eruption. That is,
  explosive active regions are concentrated in a main-sequence path
  bordering the free-energy-limit line in (flux content, free-energy
  proxy) phase space. Here, we present evidence that specifies the
  underlying magnetic condition that gives rise to the free-energy limit
  and the accompanying main sequence of explosive active regions. Using
  a suitable free-energy proxy measured from vector magnetograms of 44
  active regions, we find evidence that (1) in active regions at and near
  their free-energy limit, the ratio of magnetic-shear free energy to the
  non-free magnetic energy the potential field would have is of the order
  of one in the core field, the field rooted along the neutral line, and
  (2) this ratio is progressively less in active regions progressively
  farther below their free-energy limit. Evidently, most active regions
  in which this core-field energy ratio is much less than one cannot
  be triggered to explode; as this ratio approaches one, most active
  regions become capable of exploding; and when this ratio is one,
  most active regions are compelled to explode.

---------------------------------------------------------
Title: Solar Polar X-Ray Jets and Multiple Bright Points: Evidence
    for Sympathetic Activity
Authors: Pucci, Stefano; Poletto, Giannina; Sterling, Alphonse C.;
   Romoli, Marco
2012ApJ...745L..31P    Altcode:
  We present an analysis of X-ray bright points (BPs) and X-ray jets
  observed by Hinode/X-Ray Telescope on 2007 November 2-4, within the
  solar northern polar coronal hole. After selecting small subregions
  that include several BPs, we followed their brightness evolution over
  a time interval of a few hours, when several jets were observed. We
  find that most of the jets occurred in close temporal association
  with brightness maxima in multiple BPs: more precisely, most jets
  are closely correlated with the brightening of at least two BPs. We
  suggest that the jets result from magnetic connectivity changes that
  also induce the BP variability. We surmise that the jets and implied
  magnetic connectivity we describe are small-scale versions of the
  active-region-scale phenomenon, whereby flares and eruptions are
  triggered by interacting bipoles.

---------------------------------------------------------
Title: The Global Context of Solar Activity During the Whole
    Heliosphere Interval Campaign
Authors: Webb, D. F.; Cremades, H.; Sterling, A. C.; Mandrini, C. H.;
   Dasso, S.; Gibson, S. E.; Haber, D. A.; Komm, R. W.; Petrie, G. J. D.;
   McIntosh, P. S.; Welsch, B. T.; Plunkett, S. P.
2011SoPh..274...57W    Altcode:
  The Whole Heliosphere Interval (WHI) was an international observing and
  modeling effort to characterize the 3-D interconnected "heliophysical"
  system during this solar minimum, centered on Carrington Rotation
  2068, March 20 - April 16, 2008. During the latter half of the WHI
  period, the Sun presented a sunspot-free, deep solar minimum type
  face. But during the first half of CR 2068 three solar active regions
  flanked by two opposite-polarity, low-latitude coronal holes were
  present. These departures from the quiet Sun led to both eruptive
  activity and solar wind structure. Most of the eruptive activity,
  i.e., flares, filament eruptions and coronal mass ejections (CMEs),
  occurred during this first, active half of the interval. We determined
  the source locations of the CMEs and the type of associated region,
  such as active region, or quiet sun or active region prominence. To
  analyze the evolution of the events in the context of the global solar
  magnetic field and its evolution during the three rotations centered
  on CR 2068, we plotted the CME source locations onto synoptic maps of
  the photospheric magnetic field, of the magnetic and chromospheric
  structure, of the white light corona, and of helioseismological
  subsurface flows. Most of the CME sources were associated with the
  three dominant active regions on CR 2068, particularly AR 10989. Most
  of the other sources on all three CRs appear to have been associated
  with either isolated filaments or filaments in the north polar crown
  filament channel. Although calculations of the flux balance and
  helicity of the surface magnetic features did not clearly identify a
  dominance of one region over the others, helioseismological subsurface
  flows beneath these active regions did reveal a pronounced difference
  among them. These preliminary results suggest that the "twistedness"
  (i.e., vorticity and helicity) of subsurface flows and its temporal
  variation might be related to the CME productivity of active regions,
  similar to the relationship between flares and subsurface flows.

---------------------------------------------------------
Title: Lateral Offset of the Coronal Mass Ejections from the X-flare
    of 2006 December 13 and Its Two Precursor Eruptions
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Harra, Louise K.
2011ApJ...743...63S    Altcode:
  Two GOES sub-C-class precursor eruptions occurred within ~10 hr prior
  to and from the same active region as the 2006 December 13 X4.3-class
  flare. Each eruption generated a coronal mass ejection (CME) with
  center laterally far offset (gsim 45°) from the co-produced bright
  flare. Explaining such CME-to-flare lateral offsets in terms of the
  standard model for solar eruptions has been controversial. Using
  Hinode/X-Ray Telescope (XRT) and EUV Imaging Spectrometer (EIS)
  data, and Solar and Heliospheric Observatory (SOHO)/Large Angle and
  Spectrometric Coronagraph (LASCO) and Michelson Doppler Imager (MDI)
  data, we find or infer the following. (1) The first precursor was a
  "magnetic-arch-blowout" event, where an initial standard-model eruption
  of the active region's core field blew out a lobe on one side of the
  active region's field. (2) The second precursor began similarly, but the
  core-field eruption stalled in the side-lobe field, with the side-lobe
  field erupting ~1 hr later to make the CME either by finally being blown
  out or by destabilizing and undergoing a standard-model eruption. (3)
  The third eruption, the X-flare event, blew out side lobes on both
  sides of the active region and clearly displayed characteristics of the
  standard model. (4) The two precursors were offset due in part to the
  CME originating from a side-lobe coronal arcade that was offset from
  the active region's core. The main eruption (and to some extent probably
  the precursor eruptions) was offset primarily because it pushed against
  the field of the large sunspot as it escaped outward. (5) All three CMEs
  were plausibly produced by a suitable version of the standard model.

---------------------------------------------------------
Title: Observed Aspects of Reconnection in Solar Eruptions
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Gary, G. Allen;
   Cirtain, Jonathan W.; Falconer, David A.
2011SSRv..160...73M    Altcode: 2011SSRv..tmp..113M; 2011SSRv..tmp..189M; 2011SSRv..tmp...30M
  The observed magnetic field configuration and signatures of reconnection
  in the large solar magnetic eruptions that make major flares and coronal
  mass ejections and in the much smaller magnetic eruptions that make
  X-ray jets are illustrated with cartoons and representative observed
  eruptions. The main reconnection signatures considered are the imaged
  bright emission from the heated plasma on reconnected field lines. In
  any of these eruptions, large or small, the magnetic field that drives
  the eruption and/or that drives the buildup to the eruption is initially
  a closed bipolar arcade. From the form and configuration of the magnetic
  field in and around the driving arcade and from the development of the
  reconnection signatures in coordination with the eruption, we infer
  that (1) at the onset of reconnection the reconnection current sheet
  is small compared to the driving arcade, and (2) the current sheet can
  grow to the size of the driving arcade only after reconnection starts
  and the unleashed erupting field dynamically forces the current sheet to
  grow much larger, building it up faster than the reconnection can tear
  it down. We conjecture that the fundamental reason the quasi-static
  pre-eruption field is prohibited from having a large current sheet is
  that the magnetic pressure is much greater than the plasma pressure
  in the chromosphere and low corona in eruptive solar magnetic fields.

---------------------------------------------------------
Title: Spectroscopic Observations of a Coronal Moreton Wave
Authors: Harra, Louise K.; Sterling, Alphonse C.; Gömöry, Peter;
   Veronig, Astrid
2011ApJ...737L...4H    Altcode:
  We observed a coronal wave (EIT wave) on 2011 February 16, using
  EUV imaging data from the Solar Dynamics Observatory/Atmospheric
  Imaging Assembly (AIA) and EUV spectral data from the Hinode/EUV
  Imaging Spectrometer (EIS). The wave accompanied an M1.6 flare that
  produced a surge and a coronal mass ejection (CME). EIS data of the
  wave show a prominent redshifted signature indicating line-of-sight
  velocities of ~20 km s<SUP>-1</SUP> or greater. Following the main
  redshifted wave front, there is a low-velocity period (and perhaps
  slightly blueshifted), followed by a second redshift somewhat weaker
  than the first; this progression may be due to oscillations of the EUV
  atmosphere set in motion by the initial wave front, although alternative
  explanations may be possible. Along the direction of the EIS slit the
  wave front's velocity was ~500 km s<SUP>-1</SUP>, consistent with
  its apparent propagation velocity projected against the solar disk
  as measured in the AIA images, and the second redshifted feature had
  propagation velocities between ~200 and 500 km s<SUP>-1</SUP>. These
  findings are consistent with the observed wave being generated by the
  outgoing CME, as in the scenario for the classic Moreton wave. This
  type of detailed spectral study of coronal waves has hitherto been a
  challenge, but is now possible due to the availability of concurrent
  AIA and EIS data.

---------------------------------------------------------
Title: Insights into Filament Eruption Onset from Solar Dynamics
    Observatory Observations
Authors: Sterling, Alphonse C.; Moore, R. L.; Freeland, S. L.
2011SPD....42.0904S    Altcode: 2011BAAS..43S.0904S
  We examine the buildup to and onset of an active region filament
  confined eruption of 2010 May 12, using EUV imaging data from the Solar
  Dynamics Observatory (SDO) Atmospheric Imaging Array and line-of-sight
  magnetic data from the SDO Helioseismic and Magnetic Imager. Over the
  hour preceding eruption the filament undergoes a slow rise averaging
  3 km/s, with a step-like trajectory. Accompanying a final rise step 20
  minutes prior to eruption is a transient preflare brightening, occurring
  on loops rooted near the site where magnetic field had canceled over
  the previous 20 hr. Flow-type motions of the filament are relatively
  smooth with speeds 50 km/s prior to the preflare brightening and appear
  more helical, with speeds 50-100 km/s, after that brightening. After
  a final plateau in the filament's rise, its rapid eruption begins,
  and concurrently an outer shell "cocoon" of the filament material
  increases in emission in hot EUV lines, consistent with heating in
  a newly formed magnetic flux rope. The main flare brightenings start
  5 minutes after eruption onset. The main flare arcade begins between
  the legs of an envelope-arcade loop that is nearly orthogonal to the
  filament, suggesting that the flare results from reconnection among
  the legs of that loop. This progress of events is broadly consistent
  with flux cancellation leading to formation of a helical flux rope
  that subsequently erupts due to onset of a magnetic instability and/or
  runaway tether cutting. A full description of this work appears in
  ApJ Letters 2011, 731, L3. NASA supported this work through its Solar
  Physics Supporting Research and Technology, Sun-Earth Connection
  Guest Investigator, and Living With a Star Targeted Research &amp;
  Technology programs.

---------------------------------------------------------
Title: Insights into Filament Eruption Onset from Solar Dynamics
    Observatory Observations
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Freeland, Samuel L.
2011ApJ...731L...3S    Altcode:
  We examine the buildup to and onset of an active region filament
  confined eruption of 2010 May 12, using EUV imaging data from the Solar
  Dynamics Observatory (SDO) Atmospheric Imaging Array and line-of-sight
  magnetic data from the SDO Helioseismic and Magnetic Imager. Over the
  hour preceding eruption the filament undergoes a slow rise averaging
  ~3 km s<SUP>-1</SUP>, with a step-like trajectory. Accompanying a
  final rise step ~20 minutes prior to eruption is a transient preflare
  brightening, occurring on loops rooted near the site where magnetic
  field had canceled over the previous 20 hr. Flow-type motions of the
  filament are relatively smooth with speeds ~50 km s<SUP>-1</SUP>
  prior to the preflare brightening and appear more helical, with
  speeds ~50-100 km s<SUP>-1</SUP>, after that brightening. After a
  final plateau in the filament's rise, its rapid eruption begins,
  and concurrently an outer shell "cocoon" of the filament material
  increases in emission in hot EUV lines, consistent with heating in
  a newly formed magnetic flux rope. The main flare brightenings start
  ~5 minutes after eruption onset. The main flare arcade begins between
  the legs of an envelope-arcade loop that is nearly orthogonal to the
  filament, suggesting that the flare results from reconnection among
  the legs of that loop. This progress of events is broadly consistent
  with flux cancellation leading to formation of a helical flux rope
  that subsequently erupts due to onset of a magnetic instability and/or
  runaway tether cutting.

---------------------------------------------------------
Title: Solar X-ray Jets, Type-II Spicules, Granule-size Emerging
    Bipoles, and the Genesis of the Heliosphere
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Cirtain, Jonathan
   W.; Falconer, David A.
2011ApJ...731L..18M    Altcode:
  From Hinode observations of solar X-ray jets, Type-II spicules, and
  granule-size emerging bipolar magnetic fields in quiet regions and
  coronal holes, we advocate a scenario for powering coronal heating
  and the solar wind. In this scenario, Type-II spicules and Alfvén
  waves are generated by the granule-size emerging bipoles (EBs) in the
  manner of the generation of X-ray jets by larger magnetic bipoles. From
  observations and this scenario, we estimate that Type-II spicules and
  their co-generated Alfvén waves carry into the corona an area-average
  flux of mechanical energy of ~7 × 10<SUP>5</SUP> erg cm<SUP>-2</SUP>
  s<SUP>-1</SUP>. This is enough to power the corona and solar wind
  in quiet regions and coronal holes, and therefore indicates that the
  granule-size EBs are the main engines that generate and sustain the
  entire heliosphere.

---------------------------------------------------------
Title: Simultaneous Observations of the Chromosphere with TRACE
    and SUMER
Authors: Pasachoff, Jay M.; Tingle, Evan D.; Dammasch, Ingolf E.;
   Sterling, Alphonse C.
2011SoPh..268..151P    Altcode: 2010SoPh..tmp..209P; 2010SoPh..tmp..233P; 2010arXiv1010.4814P
  Using mainly the 1600 Å continuum channel and also the 1216 Å Lyman-α
  channel (which includes some UV continuum and C IV emission) aboard
  the TRACE satellite, we observed the complete lifetime of a transient,
  bright chromospheric loop. Simultaneous observations with the SUMER
  instrument aboard the SOHO spacecraft revealed interesting material
  velocities through the Doppler effect existing above the chromospheric
  loop imaged with TRACE, possibly corresponding to extended nonvisible
  loops, or the base of an X-ray jet.

---------------------------------------------------------
Title: Hinode extreme-ultraviolet imaging spectrometer observations
    of a limb active region
Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E.; Sterling, A. C.;
   Tripathi, D.; Young, P. R.
2011A&A...525A.137O    Altcode:
  <BR /> Aims: We investigate the electron density and temperature
  structure of a limb active region. <BR /> Methods: We have carried out
  a study of an active region close to the solar limb using observations
  from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-ray
  telescope (XRT) on board Hinode. The electron density and temperature
  distributions of the coronal emission have been determined using
  emission line intensity ratios. Differential emission measure (DEM)
  analysis and the emission measure (EM) loci technique were used to
  examine the thermal structure of the emitting plasma as a function
  of distance from the limb. <BR /> Results: The highest temperature
  and electron density values are found to be located in the core of
  the active region, with a peak electron number density value of 1.9
  × 10<SUP>10</SUP> cm<SUP>-3</SUP> measured using the Fe XII 186.887
  Å to 192.394 Å line intensity ratio. The plasma along the line of
  sight in the active region was found to be multi-thermal at different
  distances from the limb. The EIS and XRT DEM analyses appear to be
  in agreement in the temperature interval from log T = 6.5-6.7. <BR />
  Conclusions: Our results provide new constraints for models of coronal
  heating in active regions.

---------------------------------------------------------
Title: Three-dimensional morphology of a coronal prominence cavity
Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de
   Toma, G.; Hao, J.; Hill, S. M.; Hudson, H. S.; Marque, C.; McIntosh,
   P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.;
   Sterling, A.; Tripathi, D.; Williams, D. R.; Zhang, M.
2010AGUFMSH51A1667G    Altcode:
  We present a three-dimensional density model of coronal prominence
  cavities, and a morphological fit that has been tightly constrained
  by a uniquely well-observed cavity. Observations were obtained as part
  of an International Heliophysical Year campaign by instruments from a
  variety of space- and ground-based observatories, spanning wavelengths
  from radio to soft-X-ray to integrated white light. From these data
  it is clear that the prominence cavity is the limb manifestation of
  a longitudinally-extended polar-crown filament channel, and that
  the cavity is a region of low density relative to the surrounding
  corona. As a first step towards quantifying density and temperature
  from campaign spectroscopic data, we establish the three-dimensional
  morphology of the cavity. This is critical for taking line-of-sight
  projection effects into account, since cavities are not localized in the
  plane of the sky and the corona is optically thin. We have augmented
  a global coronal streamer model to include a tunnel-like cavity with
  elliptical cross-section and a Gaussian variation of height along
  the tunnel length. We have developed a semi-automated routine that
  fits ellipses to cross-sections of the cavity as it rotates past the
  solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI)
  observations from the two Solar Terrestrial Relations Observatory
  (STEREO) spacecraft. This defines the morphological parameters of our
  model, from which we reproduce forward-modeled cavity observables. We
  find that cavity morphology and orientation, in combination with the
  viewpoints of the observing spacecraft, explains the observed variation
  in cavity visibility for the east vs. west limbs.

---------------------------------------------------------
Title: Three-dimensional Morphology of a Coronal Prominence Cavity
Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de
   Toma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marqué, C.; McIntosh,
   P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.;
   Seaton, D. B.; Sterling, A. C.; Tripathi, D.; Williams, D. R.;
   Zhang, M.
2010ApJ...724.1133G    Altcode:
  We present a three-dimensional density model of coronal prominence
  cavities, and a morphological fit that has been tightly constrained
  by a uniquely well-observed cavity. Observations were obtained as part
  of an International Heliophysical Year campaign by instruments from a
  variety of space- and ground-based observatories, spanning wavelengths
  from radio to soft X-ray to integrated white light. From these data
  it is clear that the prominence cavity is the limb manifestation of
  a longitudinally extended polar-crown filament channel, and that the
  cavity is a region of low density relative to the surrounding corona. As
  a first step toward quantifying density and temperature from campaign
  spectroscopic data, we establish the three-dimensional morphology
  of the cavity. This is critical for taking line-of-sight projection
  effects into account, since cavities are not localized in the plane of
  the sky and the corona is optically thin. We have augmented a global
  coronal streamer model to include a tunnel-like cavity with elliptical
  cross-section and a Gaussian variation of height along the tunnel
  length. We have developed a semi-automated routine that fits ellipses
  to cross-sections of the cavity as it rotates past the solar limb, and
  have applied it to Extreme Ultraviolet Imager observations from the
  two Solar Terrestrial Relations Observatory spacecraft. This defines
  the morphological parameters of our model, from which we reproduce
  forward-modeled cavity observables. We find that cavity morphology
  and orientation, in combination with the viewpoints of the observing
  spacecraft, explain the observed variation in cavity visibility for
  the east versus west limbs.

---------------------------------------------------------
Title: Eruptive Signatures in the Solar Atmosphere During the WHI
    Campaign (20 March-16 April 2008)
Authors: Sterling, Alphonse C.
2010HiA....15..498S    Altcode:
  We examined EUV movies of the Sun during the period of the Whole
  Heliospheric Interval (WHI) campaign of 20 March-16 April 2008,
  searching for indications of eruptive events. Our data set was
  obtained from EIT on SOHO, using its 195 Å filter, and from EUVI
  on the two STEREO satellites, using their 171 Å, 195 Å, 284 Å,
  and 304 Å filters. Here we present a table showing results from our
  preliminary search.

---------------------------------------------------------
Title: Fibrillar Chromospheric Spicule-like Counterparts to an
    Extreme-ultraviolet and Soft X-ray Blowout Coronal Jet
Authors: Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.
2010ApJ...722.1644S    Altcode:
  We observe an erupting jet feature in a solar polar coronal hole, using
  data from Hinode/Solar Optical Telescope (SOT), Extreme Ultraviolet
  Imaging Spectrometer (EIS), and X-Ray Telescope (XRT), with supplemental
  data from STEREO/EUVI. From extreme-ultraviolet (EUV) and soft X-ray
  (SXR) images we identify the erupting feature as a blowout coronal
  jet: in SXRs it is a jet with a bright base, and in EUV it appears
  as an eruption of relatively cool (~50,000 K) material of horizontal
  size scale ~30” originating from the base of the SXR jet. In SOT
  Ca II H images, the most pronounced analog is a pair of thin (~1”)
  ejections at the locations of either of the two legs of the erupting
  EUV jet. These Ca II features eventually rise beyond 45”, leaving the
  SOT field of view, and have an appearance similar to standard spicules
  except that they are much taller. They have velocities similar to that
  of "type II" spicules, ~100 km s<SUP>-1</SUP>, and they appear to have
  spicule-like substructures splitting off from them with horizontal
  velocity ~50 km s<SUP>-1</SUP>, similar to the velocities of splitting
  spicules measured by Sterling et al. Motions of splitting features and
  of other substructures suggest that the macroscopic EUV jet is spinning
  or unwinding as it is ejected. This and earlier work suggest that a
  subpopulation of Ca II type II spicules are the Ca II manifestation
  of portions of larger scale erupting magnetic jets. A different
  subpopulation of type II spicules could be blowout jets occurring on
  a much smaller horizontal size scale than the event we observe here.

---------------------------------------------------------
Title: Evidence for magnetic flux cancelation leading to an ejective
    solar eruption observed by Hinode, TRACE, STEREO, and SoHO/MDI
Authors: Sterling, A. C.; Chifor, C.; Mason, H. E.; Moore, R. L.;
   Young, P. R.
2010A&A...521A..49S    Altcode:
  <BR /> Aims: We study the onset of a solar eruption involving a
  filament ejection on 2007 May 20. <BR /> Methods: We observe the
  filament in Hα images from Hinode/SOT and in EUV with TRACE and
  STEREO/SECCHI/EUVI. Hinode/XRT images are used to study the eruption in
  soft X-rays. From spectroscopic data taken with Hinode/EIS we obtain
  bulk-flow velocities, line profiles, and plasma densities in the
  onset region. The magnetic field evolution was observed in SoHO/MDI
  magnetograms. <BR /> Results: We observed a converging motion between
  two opposite polarity sunspots that form the primary magnetic polarity
  inversion line (PIL), along which resides filament material before
  eruption. Positive-flux magnetic elements, perhaps moving magnetic
  features (MMFs) flowing from the spot region, appear north of the
  spots, and the eruption onset occurs where these features cancel
  repeatedly in a negative-polarity region north of the sunspots. An
  ejection of material observed in Hα and EUV marks the start of the
  filament eruption (its “fast-rise”). The start of the ejection is
  accompanied by a sudden brightening across the PIL at the jet's base,
  observed in both broad-band images and in EIS. Small-scale transient
  brightenings covering a wide temperature range (Log T<SUB>e</SUB> =
  4.8-6.3) are also observed in the onset region prior to eruption. The
  preflare transient brightenings are characterized by sudden, localized
  density enhancements (to above Log n<SUB>e</SUB> [ cm<SUP>-3</SUP>] =
  9.75, in Fe XIII) that appear along the PIL during a time when pre-flare
  brightenings were occurring. The measured densities in the eruption
  onset region outside the times of those enhancements decrease with
  temperature. Persistent downflows (red-shifts) and line-broadening
  (Fe XII) are present along the PIL. <BR /> Conclusions: The array of
  observations is consistent with the pre-eruption sheared-core magnetic
  field being gradually destabilized by evolutionary tether-cutting flux
  cancelation that was driven by converging photospheric flows, and the
  main filament ejection being triggered by flux cancelation between the
  positive flux elements and the surrounding negative field. A definitive
  statement however on the eruption's ultimate cause would require
  comparison with simulations, or additional detailed observations of
  other eruptions occurring in similar magnetic circumstances. <P />The
  video that accompanies Fig. 3 is only available in electronic form at
  <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Dichotomy of Solar Coronal Jets: Standard Jets and Blowout Jets
Authors: Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse
   C.; Falconer, David A.
2010ApJ...720..757M    Altcode:
  By examining many X-ray jets in Hinode/X-Ray Telescope coronal X-ray
  movies of the polar coronal holes, we found that there is a dichotomy
  of polar X-ray jets. About two thirds fit the standard reconnection
  picture for coronal jets, and about one third are another type. We
  present observations indicating that the non-standard jets are
  counterparts of erupting-loop Hα macrospicules, jets in which the
  jet-base magnetic arch undergoes a miniature version of the blowout
  eruptions that produce major coronal mass ejections. From the coronal
  X-ray movies we present in detail two typical standard X-ray jets
  and two typical blowout X-ray jets that were also caught in He II
  304 Å snapshots from STEREO/EUVI. The distinguishing features of
  blowout X-ray jets are (1) X-ray brightening inside the base arch
  in addition to the outside bright point that standard jets have,
  (2) blowout eruption of the base arch's core field, often carrying a
  filament of cool (T ~ 10<SUP>4</SUP> - 10<SUP>5</SUP> K) plasma, and
  (3) an extra jet-spire strand rooted close to the bright point. We
  present cartoons showing how reconnection during blowout eruption of
  the base arch could produce the observed features of blowout X-ray
  jets. We infer that (1) the standard-jet/blowout-jet dichotomy of
  coronal jets results from the dichotomy of base arches that do not
  have and base arches that do have enough shear and twist to erupt open,
  and (2) there is a large class of spicules that are standard jets and
  a comparably large class of spicules that are blowout jets.

---------------------------------------------------------
Title: Production of High-temperature Plasmas During the Early Phases
    of a C9.7 Flare
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Sterling, Alphonse C.;
   Harra, Louise K.
2010ApJ...719..213W    Altcode:
  Explosive chromospheric evaporation is predicted from some current
  solar flare models. In this paper, we analyze a flare with high time
  cadence raster scans with the EUV Imaging Spectrometer (EIS) on board
  the Hinode spacecraft. This observation covers an area of 240” ×
  240”, with the 1” slit in about 160 s. The early phases of a C9.7
  flare that occurred on 2007 June 6 were well observed. The purpose of
  our analysis is to study for the first time the spatially resolved
  spectra of high-temperature plasma, especially from Fe XXIII and Fe
  XXIV, allowing us to explore the explosive chromospheric evaporation
  scenario further. Sections of raster images obtained between 17:20:09
  and 17:20:29 (UT) show a few bright patches of emission from Fe
  XXIII/Fe XXIV lines at the footpoints of the flaring loops; these
  footpoints were not clearly seen in the images taken earlier, between
  17:17:30 and 17:17:49 (UT). Fe XXIII spectra at these footpoints show
  dominating blueshifted components of -(300 to 400) km s<SUP>-1</SUP>,
  while Fe XV/XIV lines are nearly stationary; Fe XII lines and/or
  lower temperature lines show slightly redshifted features, and Fe
  VIII and Si VII to He II lines show ~+50 km s<SUP>-1</SUP> redshifted
  components. The density of the 1.5-2 MK plasma at these footpoints is
  estimated to be 3 × 10<SUP>10</SUP> cm<SUP>-3</SUP> by the Fe XIII/XIV
  line pairs around the maximum of the flare. High-temperature loops
  connecting the footpoints appear in the Fe XXIII/XXIV images taken over
  17:22:49-17:23:08 (UT) which is near the flare peak. Line profiles of
  these high-temperature lines at this flare peak time show only slowly
  moving components. The concurrent cooler Fe XVII line at 254.8 Å is
  relatively weak, indicating the predominance of high-temperature plasma
  (&gt;10<SUP>7</SUP> K) in these loops. The characteristics observed
  during the early phases of this flare are consistent with the scenario
  of explosive chromospheric evaporation.

---------------------------------------------------------
Title: Hinode Solar Optical Telescope Observations of the Source
    Regions and Evolution of "Type II" Spicules at the Solar Polar Limb
Authors: Sterling, Alphonse C.; Moore, Ronald L.; DeForest, Craig E.
2010ApJ...714L...1S    Altcode:
  We examine solar spicules using high-cadence Ca II data of the north
  pole coronal hole region, using the Solar Optical Telescope (SOT)
  on the Hinode spacecraft. The features we observe are referred to as
  "Type II" spicules by De Pontieu et al. in 2007. By convolving the
  images with the inverse-point-spread function for the SOT Ca II filter,
  we are able to investigate the roots of some spicules on the solar
  disk, and the evolution of some spicules after they are ejected from
  the solar surface. We find that the source regions of at least some of
  the spicules correspond to locations of apparent-fast-moving (~few ×
  10 km s<SUP>-1</SUP>), transient (few 100 s), Ca II brightenings on the
  disk. Frequently the spicules occur when these brightenings appear to
  collide and disappear. After ejection, when seen above the limb, many
  of the spicules fade by expanding laterally (i.e., roughly transverse
  to their motion away from the solar surface), splitting into two or
  more spicule "strands," and the spicules then fade without showing
  any downward motion. Photospheric/chromospheric acoustic shocks alone
  likely cannot explain the high velocities (~100 km s<SUP>-1</SUP>) of
  the spicules. If the Ca II brightenings represent magnetic elements,
  then reconnection among those elements may be a candidate to explain
  the spicules. Alternatively, many of the spicules could be small-scale
  magnetic eruptions, analogous to coronal mass ejections, and the
  apparent fast motions of the Ca II brightenings could be analogs of
  flare loops heated by magnetic reconnection in these eruptions.

---------------------------------------------------------
Title: Blowout Jets: Hinode X-Ray Jets that Don't Fit the Standard
    Model
Authors: Moore, Ronald L.; Cirtain, J. W.; Sterling, A. C.
2010AAS...21640620M    Altcode: 2010BAAS...41..883M
  Nearly half of all H-alpha macrospicules in polar coronal holes appear
  to be miniature filament eruptions (Yamauchi et al 2004, ApJ, 605,
  511). This suggests that there is a large class of X-ray jets in which
  the jet-base magnetic arcade undergoes a blowout eruption as in a CME,
  instead of remaining static as in most solar X-ray jets, the standard
  jets that fit the model advocated by Shibata (e.g., Shibata et al 1992,
  PASJ, 44, L173). Along with a cartoon depicting the standard model,
  we present a cartoon depicting the signatures expected of blowout
  jets in coronal X-ray images. From Hinode/XRT movies and STEREO/EUVI
  snapshots in polar coronal holes, we present examples of (1) X-ray jets
  that fit the standard model, and (2) X-ray jets that do not fit the
  standard model but do have features appropriate for blowout jets. These
  features are (1) a flare arcade inside the jet-base arcade in addition
  to the small flare arcade (bright point) outside that standard jets
  have, (2) a filament of cool (T 80,000 K) plasma that erupts from
  the core of the jet-base arcade, and (3) an extra jet strand that
  should not be made by the reconnection for standard jets but could
  be made by reconnection between the ambient unipolar open field and
  the opposite-polarity leg of the filament-carrying flux-rope core
  field of the erupting jet-base arcade. We therefore infer that these
  non-standard jets are blowout jets, jets made by miniature versions of
  the sheared-core-arcade eruptions that make CMEs. <P />This work was
  funded by NASA's Science Mission Directorate through the Heliophysics
  Guest Investigators Program, the Hinode Project, and the Living With
  a Star Targeted Research and Technology Program.

---------------------------------------------------------
Title: Solar Polar Spicules Observed with Hinode
Authors: Sterling, Alphonse C.; Moore, R. L.; DeForest, C. E.
2010AAS...21640303S    Altcode: 2010BAAS...41Q.878S
  We examine solar polar region spicules using high-cadence Ca II data
  from the Solar Optical Telescope (SOT) on the Hinode spacecraft. We
  sharpened the images by convolving them with the inverse-point-spread
  function of the SOT Ca II filter, and we are able to see some of
  the spicules originating on the disk just inside the limb. Bright
  points are frequently at the root of the disk spicules. These “Ca
  II brightenings” scuttle around at few x 10 km/s, live for 100 sec,
  and may be what are variously known as “H<SUB>2V</SUB> grains,”
  “K<SUB>2V</SUB> grains,” or "K<SUB>2V</SUB> bright points.” When
  viewed extending over the limb, some of the spicules appear to expand
  horizontally or spit into two or more components, with the horizontal
  expansion or splitting velocities reaching 50 km/s. This work was
  funded by NASA's Science Mission Directorate through the Living
  With a Star Targeted Research and Technology Program, the Supporting
  Research and Program, the Heliospheric Guest Investigator Program,
  and the Hinode project.

---------------------------------------------------------
Title: Geometric Model of a Coronal Cavity
Authors: Kucera, Therese A.; Gibson, S. E.; Rastawicki, D.; Dove, J.;
   de Toma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.;
   Reeves, K. K.; Schmidt, D. J.; Sterling, A. C.; Tripathi, D. K.;
   Williams, D. R.; Zhang, M.
2010AAS...21640510K    Altcode: 2010BAAS...41..890K
  We observed a coronal cavity from August 8-18 2007 during a
  multi-instrument observing campaign organized under the auspices of
  the International Heliophysical Year (IHY). Here we present initial
  efforts to model the cavity with a geometrical streamer-cavity
  model. The model is based the white-light streamer model of Gibson et
  al. (2003), which has been enhanced by the addition of a cavity and
  the capability to model EUV and X-ray emission. The cavity is modeled
  with an elliptical cross-section and Gaussian fall-off in length and
  width inside the streamer. Density and temperature can be varied in the
  streamer and cavity and constrained via comparison with data. Although
  this model is purely morphological, it allows for three-dimensional,
  multi-temperature analysis and characterization of the data, which
  can then provide constraints for future physical modeling. Initial
  comparisons to STEREO/EUVI images of the cavity and streamer show that
  the model can provide a good fit to the data. This work is part of the
  effort of the International Space Science Institute International Team
  on Prominence Cavities.

---------------------------------------------------------
Title: Triggering of solar magnetic eruptions on various size scales
Authors: Sterling, Alphonse
2010cosp...38.2839S    Altcode: 2010cosp.meet.2839S
  A solar eruption that produces a coronal mass ejection (CME) together
  with a flare is driven by the eruption of a closed-loop magnetic
  arcade that has a sheared-field core. Before eruption, the sheared
  core envelops a polarity inversion line along which cool filament
  material may reside. The sheared-core arcade erupts when there is
  a breakdown in the balance between the confining downward-directed
  magnetic tension of the overall arcade field and the upward-directed
  force of the pent-up magnetic pressure of the sheared field in the
  core of the arcade. What triggers the breakdown in this balance in
  favor of the upward-directed force is still an unsettled question. We
  consider several eruption examples, using imaging data from the SoHO,
  TRACE and Hinode satellites, and other sources, along with information
  about the magnetic field of the erupting regions. In several cases,
  observations of large-scale eruptions, where the magnetic neutral line
  spans ∼ few ×10,000 km, are consistent with magnetic flux cancelation
  being the trigger to the eruption's onset, even though the amount of
  flux canceled is only ∼ few percent of the total magnetic flux of
  the erupting region. In several other cases, an initial compact (small
  size-scale) eruption occurs embedded inside of a larger closed magnetic
  loop system, so that the smaller eruption destabilizes and causes the
  eruption of the much larger system. In this way, small-scale eruptive
  events can result in eruption of much larger-scale systems. This work
  was funded by NASA's Science Mission Directorate thought the Living
  With a Star Targeted Research and Technology Program, the Supporting
  Research and Program, and the Hinode project.

---------------------------------------------------------
Title: Two types of magnetic flux cancelation in the solar eruption
    of 2007 May 20
Authors: Sterling, Alphonse; Moore, Ronald; Mason, Helen
2010cosp...38.1946S    Altcode: 2010cosp.meet.1946S
  We study a solar eruption on 2007 May 20, in an effort to understand the
  cWe study a solar eruption of 2007 May 20, in an effort to understand
  the cause of the eruption's onset. The event produced a GOES class
  B6.7 flare peaking at 05:56 UT, while ejecting a surge/filament and
  producing a coronal mass ejection (CME). We examine several data
  sets, including Hα images from the Solar Optical Telescope (SOT) on
  Hinode, EUV images from TRACE, and line-of-sight magnetograms from
  SoHO/MDI. Flux cancelation occurs among two different sets of flux
  elements inside of the erupting active region: First, for several days
  prior to eruption, opposite-polarity sunspot groups inside the region
  move toward each other, leading to the cancelation of ∼ 1021 Mx
  of flux over three days. Second, within hours prior to the eruption,
  positive-polarity moving magnetic features (MMFs) flowing out of the
  positive-flux spots at ∼ 1 km/s repeatedly cancel with field inside
  a patch of negative-polarity flux located north of the sunspots. The
  filament erupts as a surge whose base is rooted in the location where
  the MMF cancelation occurs, while during the eruption that filament
  flows out along the polarity inversion line between the converging spot
  groups. We conclude that a plausible scenario is that the converging
  spot fields brought the magnetic region to the brink of instability,
  and the MMF cancelation pushed the system "over the edge," triggering
  the eruption. This work was funded by NASA's Science Mission Directorate
  thought the Living With a Star Targeted Research and Technology Program,
  the Supporting Research and Program, and the Hinode project.

---------------------------------------------------------
Title: Limb Spicules from the Ground and from Space
Authors: Pasachoff, Jay M.; Jacobson, William A.; Sterling, Alphonse C.
2009SoPh..260...59P    Altcode: 2009arXiv0909.0027P
  We amassed statistics for quiet-sun chromosphere spicules at the limb
  using ground-based observations from the Swedish 1-m Solar Telescope on
  La Palma and simultaneously from NASA's Transition Region and Coronal
  Explorer (TRACE) spacecraft. The observations were obtained in July
  2006. With the 0.2 arcsecond resolution obtained after maximizing
  the ground-based resolution with the Multi-Object Multi-Frame Blind
  Deconvolution (MOMFBD) program, we obtained specific statistics for
  sizes and motions of over two dozen individual spicules, based on
  movies compiled at 50-second cadence for the series of five wavelengths
  observed in a very narrow band at Hα, on-band and at ± 0.035 nm
  and ± 0.070 nm (10 s at each wavelength) using the SOUP filter,
  and had simultaneous observations in the 160 nm EUV continuum from
  TRACE. The MOMFBD restoration also automatically aligned the images,
  facilitating the making of Dopplergrams at each off-band pair. We
  studied 40 Hα spicules, and 14 EUV spicules that overlapped Hα
  spicules; we found that their dynamical and morphological properties
  fit into the framework of several previous studies. From a preliminary
  comparison with spicule theories, our observations are consistent with
  a reconnection mechanism for spicule generation, and with UV spicules
  being a sheath region surrounding the Hα spicules.

---------------------------------------------------------
Title: Large-Scale Flows in Prominence Cavities
Authors: Schmit, D. J.; Gibson, S. E.; Tomczyk, S.; Reeves, K. K.;
   Sterling, Alphonse C.; Brooks, D. H.; Williams, D. R.; Tripathi, D.
2009ApJ...700L..96S    Altcode:
  Regions of rarefied density often form cavities above quiescent
  prominences. We observed two different cavities with the Coronal
  Multichannel Polarimeter on 2005 April 21 and with Hinode/EIS on 2008
  November 8. Inside both of these cavities, we find coherent velocity
  structures based on spectral Doppler shifts. These flows have speeds of
  5-10 km s<SUP>-1</SUP>, occur over length scales of tens of megameters,
  and persist for at least 1 hr. Flows in cavities are an example of
  the nonstatic nature of quiescent structures in the solar atmosphere.

---------------------------------------------------------
Title: Flows and Plasma Properties in Quiescent Cavities
Authors: Schmit, Donald; Gibson, S.; Reeves, K.; Sterling, A.;
   Tomczyk, S.
2009SPD....40.1015S    Altcode:
  Regions of rarefied density often form cavities above quiescent
  prominences. In an attempt to constrain the plasma properties of
  "equilibrium" cavities we conduct several diagnostics using Hinode/EIS,
  STEREO/EUVI, and CoMP. One novel observation is of large scale flows in
  cavities. Using different instruments to observe two distinct cavities
  off the solar limb in coronal emission lines, we find that spectral
  doppler shifts imply LOS velocities within cavities on the order of
  1-10 km/s. These flows occur over length scales of several hundred Mm
  and persist for hours.

---------------------------------------------------------
Title: Solar Spicules Near and at the Limb, Observed from Hinode
Authors: Sterling, Alphonse C.
2009SPD....40.1006S    Altcode:
  Solar spicules appear as narrow jets emanating from the chromosphere and
  extending into the corona. They have been observed for over a hundred
  years, mainly in chromospheric spectral lines such as Hα. Because they
  are at the limit of visibility of ground-based instruments, their nature
  has long been a puzzle. In recent years however, vast progress has been
  made in understanding them both theoretically and observationally. Most
  recently, spicule studies have undergone a revolution because of the
  superior resolution, time cadence, and atmosphere-free observations
  from the Solar Optical Telescope (SOT) instrument on the Hinode
  spacecraft. Here we present observations of spicules from Hinode SOT,
  and consider how the observations from Hinode compare with historical
  observations. We include data taken in the blue and red wings of Hα,
  where the spicules have widths of a few 100 kms, and the longest ones
  reach 10<SUP>4 </SUP>km in extent, similar to sizes long reported from
  ground-based instruments. Their dynamics are not easy to generalize,
  with many showing the upward movement followed by falling or fading,
  as traditionally reported, but with others showing more dynamic or
  even ejective aspects. There is a strong transverse component to their
  motion, as extensively reported previously from the Hinode data as
  evidence for Alfven waves. <P />NASA supported this work through its
  Living with a Star program.

---------------------------------------------------------
Title: Coronal Nonthermal Velocity Following Helicity Injection
    Before an X-Class Flare
Authors: Harra, L. K.; Williams, D. R.; Wallace, A. J.; Magara, T.;
   Hara, H.; Tsuneta, S.; Sterling, A. C.; Doschek, G. A.
2009ApJ...691L..99H    Altcode:
  We explore the "pre-flare" behavior of the corona in a three-day
  period building up to an X-class flare on 2006 December 13 by analyzing
  EUV spectral profiles from the Hinode EUV Imaging Spectrometer (EIS)
  instrument. We found an increase in the coronal spectral line widths,
  beginning after the time of saturation of the injected helicity as
  measured by Magara &amp; Tsuneta. In addition, this increase in line
  widths (indicating nonthermal motions) starts before any eruptive
  activity occurs. The Hinode EIS has the sensitivity to measure changes
  in the buildup to a flare many hours before the flare begins.

---------------------------------------------------------
Title: New Evidence that CMEs are Self-Propelled Magnetic Bubbles
Authors: Moore, R. L.; Sterling, A. C.; Suess, S. T.
2008ASPC..397...98M    Altcode:
  We briefly describe the “standard model” for the production of coronal
  mass ejections (CMEs), and our view of how it works. We then summarize
  pertinent recent results that we have found from SOHO observations of
  CMEs and the flares at the sources of these magnetic explosions. These
  results support our interpretation of the standard model: a CME is
  basically a self-propelled magnetic bubble, a low-beta plasmoid,
  that (1) is built and unleashed by the tether-cutting reconnection
  that builds and heats the coronal flare arcade, (2) can explode from
  a flare site that is far from centered under the full-blown CME in
  the outer corona, and (3) drives itself out into the solar wind by
  pushing on the surrounding coronal magnetic field.

---------------------------------------------------------
Title: Early Hinode Observations of a Solar Filament Eruption
Authors: Sterling, A. C.; Moore, R. L.
2008ASPC..397..115S    Altcode:
  We use Hinode X-Ray Telescope (XRT) and Solar Optical Telescope (SOT)
  filtergraph (FG) Stokes-V magnetogram observations to study the early
  onset of a solar eruption that includes an erupting filament that we
  observe in TRACE EUV images; this is one of the first filament eruptions
  seen with Hinode. The filament undergoes a slow rise for at least
  30 min prior to its fast eruption and strong soft X-ray flaring, and
  the new Hinode data elucidate the physical processes occurring during
  the slow-rise period. During the slow-rise phase, a soft X-ray (SXR)
  sigmoid forms from apparent reconnection low in the sheared core field
  traced by the filament, and there is a low-level intensity peak in both
  EUV and SXRs during the slow rise. The SOT data show that magnetic flux
  cancelation occurs along the neutral line of the filament in the hours
  before eruption, and this likely caused the low-lying reconnection that
  produced the microflaring and the slow rise leading up to the eruption.

---------------------------------------------------------
Title: Magnetic Flux Cancelation Leading to the Eruption of a Coronal
Mass Ejection: Observations from Hinode, SOHO, TRACE, and STEREO
Authors: Sterling, A. C.; Chifor, C.; Mason, H.; Moore, R. L.
2008AGUSMSP23B..05S    Altcode:
  We study a solar eruption involving ejection of a filament on 2007 May
  20, using instruments on Hinode, STEREO, TRACE, and SOHO. We observe
  the filament in EUV from TRACE and STEREO, and in H-alpha from SOT on
  Hinode. We also see the eruption in soft X-rays with XRT on Hinode,
  and in several EUV lines from EIS on Hinode. SOHO/MDI magnetograms
  show that converging motion between opposite-polarity sunspots in the
  region result in expansion of large-scale loops overlying the region's
  primary magnetic neutral line, along which sits filament material prior
  to its eruption. The source location of an EUV filament's surge-like
  ejection is a negative-polarity magnetic region that is north of the
  interacting spots, and patches of magnetic field flow at ~ 0.5 km/s
  from the positive converging spots into the negative region in the
  north. Apparently, repeated episodes of flux cancelation occur where
  the flowing positive flux collides with the northern negative flux,
  and the source of the EUV filament's ejection is near this cancelation
  site. Spectroscopic data from EIS are available for a portion of the
  active region that includes the northern cancelation site, and from
  these data we obtain bulk-flow velocities, line-broadening turbulent
  velocities, and densities of plasma in the region. The array of
  observations is consistent with the pre-eruption sheared-core magnetic
  arcade being gradually destabilized by evolutionary tether-cutting
  flux cancelation that was driven by converging photospheric flows.

---------------------------------------------------------
Title: Initiation of Solar Eruptions
Authors: Sterling, A. C.; Moore, R. L.
2008ASPC..383..163S    Altcode:
  We consider processes occurring just prior to and at the start of
  the onset of flare- and CME-producing solar eruptions. Our recent
  work uses observations of filament motions around the time of
  eruption onset as a proxy for the evolution of the fields involved
  in the eruption. Frequently the filaments show a slow rise prior to
  fast eruption, indicative of a slow expansion of the field that is
  about to explode. Work by us and others suggests that reconnection
  involving emerging or canceling flux results in a lengthening of
  fields restraining the filament-carrying field, and the consequent
  upward expansion of the field in and around the filament produces the
  filament's slow rise; that is, the reconnection weakens the magnetic
  “tethers” (“tether-weakening” reconnection), and results in the slow
  rise of the filament. It is still inconclusive, however, what mechanism
  is responsible for the switch from the slow rise to the fast eruption.

---------------------------------------------------------
Title: Hinode Observations of the Onset Stage of a Solar Filament
    Eruption
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Berger, Thomas
   E.; Bobra, Monica; Davis, John M.; Jibben, Patricia; Kano, Ryohei;
   Lundquist, Loraine L.; Myers, D.; Narukage, Noriyuki; Sakao, Taro;
   Shibasaki, Kiyoto; Shine, Richard A.; Tarbell, Theodore D.; Weber, Mark
2007PASJ...59S.823S    Altcode:
  We used Hinode X-Ray Telescope (XRT) and Solar Optical Telescope (SOT)
  filtergraph (FG) Stokes-V magnetogram observations, to study the
  early onset of a solar eruption that includes an erupting filament
  that we observe in TRACE EUV images. The filament undergoes a slow
  rise for at least 20min prior to its fast eruption and strong soft
  X-ray (SXR) flaring; such slow rises have been previously reported,
  and the new Hinode data elucidate the physical processes occurring
  during this period. XRT images show that during the slow-rise phase,
  an SXR sigmoid forms from apparent reconnection low in the sheared core
  field traced by the filament, and there is a low-level intensity peak
  in both EUV and SXRs during the slow rise. MDI and SOT FG Stokes-V
  magnetograms show that the pre-eruption filament is along a neutral
  line between opposing-polarity enhanced network cells, and the SOT
  magnetograms show that these opposing fields are flowing together
  and canceling for at least six hours prior to eruption. From the MDI
  data we measured the canceling network fields to be ∼ 40G, and we
  estimated that ∼ 10<SUP>19</SUP> Mx of flux canceled during the
  five hours prior to eruption; this is only ∼ 5% of the total flux
  spanned by the eruption and flare, but apparently its tether-cutting
  cancellation was enough to destabilize the sigmoid field holding the
  filament and resulted in that field's eruption.

---------------------------------------------------------
Title: Coronal Dimming Observed with Hinode: Outflows Related to a
    Coronal Mass Ejection
Authors: Harra, Louise K.; Hara, Hirohisa; Imada, Shinsuke; Young,
   Peter R.; Williams, David R.; Sterling, Alphonse C.; Korendyke,
   Clarence; Attrill, Gemma D. R.
2007PASJ...59S.801H    Altcode:
  Coronal dimming has been a signature used to determine the source
  of plasma that forms part of a coronal mass ejection (CME) for many
  years. Generally dimming is detected through imaging instruments such
  as SOHO EIT by taking difference images. Hinode tracked active region
  10930 from which there were a series of flares. We combined dimming
  observations from EIT with Hinode data to show the impact of flares
  and coronal mass ejections on the region surrounding the flaring
  active region, and we discuss evidence that the eruption resulted in
  a prolonged steady outflow of material from the corona. The dimming
  region shows clear structure with extended loops whose footpoints are
  the source of the strongest outflow (≈ 40 kms<SUP>-1</SUP>). This
  confirms that the loops that are disrupted during the event do lose
  plasma and hence are likely to form part of the CME. This is the
  first time the velocity of the coronal plasma has been measured in an
  extended dimming region away from the flare core. In addition there
  was a weaker steady outflow from extended, faint loops outside the
  active region before the eruption, which is also long lasting. These
  were disturbed and the velocity increased following the flare. Such
  outflows could be the source of the slow solar wind.

---------------------------------------------------------
Title: New Evidence for the Role of Emerging Flux in a Solar
    Filament's Slow Rise Preceding Its CME-producing Fast Eruption
Authors: Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.
2007ApJ...669.1359S    Altcode:
  We observe the eruption of a large-scale (~300,000 km) quiet-region
  solar filament leading to an Earth-directed “halo” coronal mass
  ejection (CME), using data from EIT, CDS, MDI, and LASCO on SOHO
  and from SXT on Yohkoh. Initially the filament shows a slow (~1 km
  s<SUP>-1</SUP> projected against the solar disk) and approximately
  constant velocity rise for about 6 hr, before erupting rapidly, reaching
  a velocity of ~8 km s<SUP>-1</SUP> over the next ~25 minutes. CDS
  Doppler data show Earth-directed filament velocities ranging from
  &lt;20 km s<SUP>-1</SUP> (the noise limit) during the slow-rise phase,
  to ~100 km s<SUP>-1</SUP> early in the eruption. Beginning within 10
  hr prior to the start of the slow rise, localized new magnetic flux
  emerged near one end of the filament. Near the start of and during the
  slow-rise phase, soft X-ray (SXR) microflaring occurred repeatedly at
  the flux-emergence site, and the magnetic arcade over the filament
  progressively brightened in a fan of illumination in SXRs. These
  observations are consistent with “tether-weakening” reconnection
  occurring between the newly emerging flux and the overlying arcade
  field containing the filament, and apparently this reconnection is the
  cause of the filament's slow rise. We cannot, however, discern whether
  the transition from slow rise to fast eruption was caused by a final
  episode of tether-weakening reconnection, or by one or some combination
  of other possible mechanisms allowed by the observations. Intensity
  “dimmings” and “brightenings” occurring both near to and relatively
  far from the location of the filament are possible signatures of the
  expansion (“opening”) of the erupting field and its reconnection
  with overarching field during the eruption.

---------------------------------------------------------
Title: Origin of the Sheared Magnetic Fields that Explode in Flares
    and Coronal Mass Ejections
Authors: Moore, R. L.; Sterling, A. C.
2007ASPC..369..539M    Altcode:
  From observations of 37 flare-arcade events, their magnetic settings,
  their sheared core fields, and the coronal mass ejections from these
  events, we find evidence that the sheared core fields in mature
  magnetic arcades are not formed by bodily emergence of a twisted flux
  rope along the neutral line. This implies that these sigmoidal sheared
  fields are instead formed by reconnection and flows above and in the
  photosphere. A high priority of Solar-B should be to discover the
  evolutionary processes that build the sigmoidal sheared fields along
  mature neutral lines.

---------------------------------------------------------
Title: The Width of a Solar Coronal Mass Ejection and the Source of
the Driving Magnetic Explosion: A Test of the Standard Scenario for
    CME Production
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Suess, Steven T.
2007ApJ...668.1221M    Altcode:
  We show that the strength (B<SUB>Flare</SUB>) of the magnetic
  field in the area covered by the flare arcade following
  a CME-producing ejective solar eruption can be estimated
  from the final angular width (Final θ<SUB>CME</SUB>)
  of the CME in the outer corona and the final angular width
  (θ<SUB>Flare</SUB>) of the flare arcade: B<SUB>Flare</SUB>~1.4[(Final
  θ<SUB>CME</SUB>)/θ<SUB>Flare</SUB><SUP>2</SUP> G. We assume (1) the
  flux-rope plasmoid ejected from the flare site becomes the interior of
  the CME plasmoid; (2) in the outer corona (R&gt;2 R<SUB>solar</SUB>)
  the CME is roughly a “spherical plasmoid with legs” shaped like a
  lightbulb; and (3) beyond some height in or below the outer corona
  the CME plasmoid is in lateral pressure balance with the surrounding
  magnetic field. The strength of the nearly radial magnetic field
  in the outer corona is estimated from the radial component of the
  interplanetary magnetic field measured by Ulysses. We apply this
  model to three well-observed CMEs that exploded from flare regions
  of extremely different size and magnetic setting. One of these CMEs
  was an over-and-out CME, that is, in the outer corona the CME was
  laterally far offset from the flare-marked source of the driving
  magnetic explosion. In each event, the estimated source-region field
  strength is appropriate for the magnetic setting of the flare. This
  agreement (1) indicates that CMEs are propelled by the magnetic field
  of the CME plasmoid pushing against the surrounding magnetic field;
  (2) supports the magnetic-arch-blowout scenario for over-and-out CMEs;
  and (3) shows that a CME's final angular width in the outer corona
  can be estimated from the amount of magnetic flux covered by the
  source-region flare arcade.

---------------------------------------------------------
Title: Analysis of Erupting Solar Prominences in Terms of an
    Underlying Flux-Rope Configuration
Authors: Krall, Jonathan; Sterling, Alphonse C.
2007ApJ...663.1354K    Altcode:
  Data from four solar prominence eruptions are analyzed so as to
  examine the flux-rope configuration at the onset of eruption and
  to test specific aspects of an analytic flux-rope model of solar
  eruptions. The model encompasses both prominence eruptions and coronal
  mass ejections (CMEs) as generic elements of a typical erupting
  flux-rope structure. The hypothesized relationship between prominence
  footpoint separation and prominence acceleration profile is examined, as
  is the hypothesized geometrical relationship between the prominence and
  the CME leading edge (LE). While the simple model does not account for
  some observed features, the prominence and “loop” (LE) data are shown
  to be consistent with both the geometrical model and the theoretical
  acceleration profile. This analysis further suggests that the onset
  of eruption is associated with a situation in which the underlying
  flux-rope geometry maximizes the outward magnetic “hoop” force.

---------------------------------------------------------
Title: Coronal dimming observed with Hinode
Authors: Harra, Louise; Hara, H.; Young, P.; Williams, D.; Sterling,
   A.; Attrill, G.
2007AAS...210.6305H    Altcode: 2007BAAS...39..172H
  Coronal dimming has been a technique used to determine the source
  of plasma that forms part of a coronal mass ejection. Generally
  dimming is detected through imaging instruments such as SOHO EIT by
  taking difference images. In a few cases the SOHO-CDS has been used
  to determine outflowing material, and a decrease in density. Hinode
  tracked active region 10930 from which there were a series of flares. We
  combine dimming observations from EIT with Hinode data to show the
  impact of flares and coronal mass ejections on the region surrounding
  the flaring active region, and we discuss evidence that the eruption
  resulted in a prolonged steady outflow of material from the corona.

---------------------------------------------------------
Title: The Coronal-dimming Footprint of a Streamer-Puff Coronal Mass
Ejection: Confirmation of the Magnetic-Arch-Blowout Scenario
Authors: Moore, Ronald L.; Sterling, Alphonse C.
2007ApJ...661..543M    Altcode:
  A streamer puff is a recently identified variety of coronal mass
  ejection (CME) of narrow to moderate width. It (1) travels out along
  a streamer, transiently inflating the streamer but leaving it largely
  intact, and (2) occurs in step with a compact ejective flare in an
  outer flank of the base of the streamer. These aspects suggest the
  following magnetic-arch-blowout scenario for the production of these
  CMEs: the magnetic explosion that produces the flare also produces a
  plasmoid that explodes up the leg of an outer loop of the arcade base
  of the streamer, blows out the top of this loop, and becomes the core
  of the CME. In this paper, we present a streamer-puff CME that produced
  a coronal dimming footprint. The coronal dimming, its magnetic setting,
  and the timing and magnetic setting of a strong compact ejective flare
  within the dimming footprint nicely confirm the magnetic-arch-blowout
  scenario. From these observations, together with several published
  cases of a transequatorial CME produced in tandem with an ejective
  flare or filament eruption that was far offset from directly under the
  CME, we propose the following. Streamer-puff CMEs are a subclass (one
  variety) of a broader class of “over-and-out” CMEs that are often
  much larger than streamer puffs but are similar to them in that they
  are produced by the blowout of a large quasi-potential magnetic arch
  by a magnetic explosion that erupts from one foot of the large arch,
  where it is marked by a filament eruption and/or an ejective flare.

---------------------------------------------------------
Title: Analysis of Polar Plumes Observed During March 29, 2006 Total
    Solar Eclipse
Authors: Farid, Samaiyah; Winebarger, A.; Oluseyi, H.; Sterling, A.;
   Tan, A.
2007AAS...210.9508F    Altcode: 2007BAAS...39..224F
  Polar plumes are long lived structures that occur in coronal holes
  and are thought to be the source region of the slow solar wind. In
  this poster, we present analysis of polar plumes observed during the
  March 29, 2006 solar eclipse from Cape Coast, Ghana. We have analyzed
  SOHO/EIT data of the same time and date of the eclipse to determine how
  the EUV intensity varies as a function of height. We have developed a
  steady-state one dimensional hydrodynamic model of plumes that includes
  a stratified heating rate, area expansion, and a non-zero velocity
  at the plume base. We have compared the intensity profiles from the
  model calculated for different heating rates and base velocities with
  the intensity profiles of the observed plumes. We present the results
  of our model and the analysis and make a conjecture about the mass
  contribution of plumes to the solar wind.

---------------------------------------------------------
Title: The Coronal-dimming Footprint Of A Streamer-puff Coronal Mass
Ejection: Confirmation Of The Magnetic-arch-blowout Scenario
Authors: Moore, Ronald L.; Sterling, A. C.
2007AAS...210.2907M    Altcode: 2007BAAS...39..138M
  A streamer puff is a recently identified variety of coronal mass
  ejection (CME) of narrow to moderate width. It (1) travels out along
  a streamer, transiently inflating the streamer but leaving it largely
  intact, and (2) occurs in step with a compact ejective flare in an
  outer flank of the base of the streamer. These aspects suggest the
  following magnetic-arch-blowout scenario for the production of these
  CMEs: the magnetic explosion that produces the flare also produces a
  plasmoid that explodes up the leg of an outer loop of the arcade base
  of the streamer, blows out the top of this loop, and becomes the core
  of the CME. In this paper, we present a steamer-puff CME that produced
  a coronal dimming footprint. The coronal dimming, its magnetic setting,
  and the timing and magnetic setting of a strong compact ejective flare
  within the dimming footprint nicely confirm the magnetic-arch-blowout
  scenario. From these observations, together with several published
  cases of a trans-equatorial CME produced in tandem with an ejective
  flare or filament eruption that was far offset from directly under the
  CME, we propose the following. Streamer-puff CMEs are a subclass (one
  variety) of a broader class of “over-and-out” CMEs that are often
  much larger than steamer puffs but are similar to them in that they
  are produced by the blowout of a large quasi-potential magnetic arch
  by a magnetic explosion that erupts from one foot of the large arch,
  where it is marked by a filament eruption and/or an ejective flare. <P
  />This work was funded by the Heliophysics Division of NASA's Science
  Mission Directorate.

---------------------------------------------------------
Title: Combined Hinode, STEREO, And TRACE Observations of a Solar
Filament Eruption: Evidence For Destabilization By Flux-Cancelation
    Tether Cutting
Authors: Sterling, Alphonse C.; Moore, R. L.; Hinode Team
2007AAS...210.7207S    Altcode: 2007BAAS...39R.179S
  We present observations from Hinode, STEREO, and TRACE of a solar
  filament eruption and flare that occurred on 2007 March 2. Data
  from the two new satellites, combined with the TRACE observations,
  give us fresh insights into the eruption onset process. HINODE/XRT
  shows soft X-ray (SXR) activity beginning approximately 30 minutes
  prior to ignition of bright flare loops. STEREO and TRACE images show
  that the filament underwent relatively slow motions coinciding with
  the pre-eruption SXR brightenings, and it underwent rapid eruptive
  motions beginning near the time of flare onset. Concurrent HINODE/SOT
  magnetograms showed substantial flux cancelation under the filament at
  the site of the pre-eruption SXR activity. From these observations
  we infer that progressive tether-cutting reconnection driven by
  photospheric convection caused the slow rise of the filament and
  led to its eruption. <P />NASA supported this work through a NASA
  Heliosphysics GI grant.

---------------------------------------------------------
Title: Cool-Plasma Jets that Escape into the Outer Corona
Authors: Corti, Gianni; Poletto, Giannina; Suess, Steve T.; Moore,
   Ronald L.; Sterling, Alphonse C.
2007ApJ...659.1702C    Altcode:
  We report on observations acquired in 2003 May during a SOHO-Ulysses
  quadrature campaign. The UVCS slit was set normal to the radial of
  the Sun along the direction to Ulysses at 1.7 R<SUB>solar</SUB>, at
  a northern latitude of 14.5°. From May 25 to May 28, UVCS acquired
  spectra of several short-lived ejections that represent the extension
  at higher altitudes of recursive EIT jets, imaged in He II λ304. The
  jets were visible also in LASCO images and seem to propagate along
  the radial to Ulysses. UVCS spectra showed an unusually high emission
  in cool lines, lasting for about 10-25 minutes, with no evidence of
  hot plasma. Analysis of the cool line emission allowed us to infer
  the physical parameters (temperature, density, and outward velocity)
  of jet plasma and the evolution of these quantities as the jet crossed
  the UVCS slit. From these quantities, we estimated the energy needed
  to produce the jet. We also looked for any evidence of the events in
  the in situ data. We conclude by comparing our results with those of
  previous works on similar events and propose a scenario that accounts
  for the observed magnetic setting of the source of the jets and allows
  the jets to be magnetically driven.

---------------------------------------------------------
Title: Initiation of Coronal Mass Ejections
Authors: Moore, Ronald L.; Sterling, Alphonse C.
2006GMS...165...43M    Altcode:
  This paper is a synopsis of the initiation of the strong-field magnetic
  explosions that produce large, fast coronal mass ejections. The
  presentation outlines our current view of the eruption onset, based on
  results from our own observational work and from the observational and
  modeling work of others. From these results and from physical reasoning,
  we and others have inferred the basic processes that trigger and
  drive the explosion. We describe and illustrate these processes using
  cartoons. The magnetic field that explodes is a sheared-core bipole
  that may or may not be embedded in surrounding strong magnetic field,
  and may or may not contain a flux rope before it starts to explode. We
  describe three different mechanisms that singly or in combination
  can trigger the explosion: (1) runaway internal tether-cutting
  reconnection, (2) runaway external tether-cutting reconnection, and
  (3) ideal MHD instability or loss or equilibrium. For most eruptions,
  high-resolution, high-cadence magnetograms and chromospheric and coronal
  movies (such as from TRACE or Solar-B) of the pre-eruption region and
  of the onset of the eruption and flare are needed to tell which one
  or which combination of these mechanisms is the trigger. Whatever the
  trigger, it leads to the production of an erupting flux rope. Using
  a simple model flux rope, we demonstrate that the explosion can be
  driven by the magnetic pressure of the expanding flux rope, provided
  the shape of the expansion is "fat" enough.

---------------------------------------------------------
Title: Wide and Narrow CMEs and their Source Explosions Observed at
    the Spring 2003 SOHO-Sun-Ulysses Quadrature
Authors: Suess, S. T.; Corti, G.; Poletto, G.; Sterling, A.; Moore, R.
2006ESASP.617E.147S    Altcode: 2006soho...17E.147S
  No abstract at ADS

---------------------------------------------------------
Title: Characteristics of EIT Dimmings in Solar Eruptions
Authors: Adams, Mitzi; Sterling, A. C.
2006SPD....37.0114A    Altcode: 2006BAAS...38..217A
  Intensity "dimmings" in coronal images are a key feature of solar
  eruptions. Such dimmings are likely the source locations for much of
  the material expelled in coronal mass ejections (CMEs). Characteristics
  such as the timing of the dimmings with respect to the onset of other
  eruption signatures, and the location of the dimmings in the context of
  the magnetic field environment of the erupting region, are indicative
  of the mechanism leading to the eruption. We examine dimmings of six
  eruptions in images from the EUV Imaging Telescope (EIT) on SOHO,
  along with supplementary soft X-ray (SXR) data from GOES and the SXR
  Telescope (SXT) on Yohkoh. We examine the timing of the dimming onset
  and compare with the time of EUV and SXR brightening and determine
  the timescale for the recovery from dimming for each event. With
  line-of-sight photospheric magnetograms from the MDI instrument on
  SOHO, we determine the magnetic structure of the erupting regions
  and the locations of the dimmings in those regions. &gt;From our
  analysis we consider which mechanism likely triggered each eruption:
  internal tether cutting, external tether cutting ("breakout"), loss
  of equilibrium, or some other mechanism.

---------------------------------------------------------
Title: Initiation of the Slow-Rise and Fast-Rise Phases of an Erupting
    Solar Filamentby Localized Emerging Magnetic Field via Microflaring
Authors: Sterling, Alphonse C.; Moore, R. L.; Harra, L. K.
2006SPD....37.0823S    Altcode: 2006BAAS...38..234S
  EUV data from EIT show that a filament of 2001 February 28 underwent
  aslow-rise phase lasting about 6 hrs, before rapidly erupting in a
  fast-risephase. Concurrent images in soft X-rays (SXRs) from Yohkoh/SXT
  show that aseries of three microflares, prominent in SXT images but weak
  in EIT 195 AngEUV images, occurred near one end of the filament. The
  first and lastmicroflares occurred respectively in conjunction with
  the start of theslow-rise phase and the start of the fast-rise phase,
  and the second microflarecorresponded to a kink in the filament
  trajectory. Beginning within 10 hoursof the start of the slow rise,
  new magnetic flux emerged at the location of themicroflaring. This
  localized new flux emergence and the resulting microflares,consistent
  with reconnection between the emerging field and the sheared sigmoidcore
  magnetic field holding the filament, apparently caused the slow
  rise ofthis field and the transition to explosive eruption. For the
  first time insuch detail, the observations show this direct action of
  localized emergingflux in the progressive destabilization of a sheared
  core field in the onset ofa coronal mass ejection (CME). Similar
  processes may have occurred in otherrecently-studied events.NASA
  supported this work through NASA SR&amp;T and SEC GI grants.

---------------------------------------------------------
Title: The Origin Of The Sheared Magnetic Fields That Erupt In Flares
    And Coronal Mass Ejections
Authors: Moore, Ronald L.; Sterling, A. C.
2006SPD....37.2001M    Altcode: 2006BAAS...38R.247M
  From a search of the Yohkoh/SXT whole-Sun movie in the years 2000 and
  2001, we found 37 flare-arcade events for which there were full-disk
  magnetograms from SOHO/MDI, coronagraph movies from SOHO/LASCO, and
  before and after full-disk chromospheric images from SOHO/EIT and/or
  from ground-based observatories. For each event, the observations show
  or strongly imply that the flare arcade was produced in the usual way
  by the eruption of sheared core field (as a flux rope) from along the
  neutral line inside a mature bipolar magnetic arcade. Two-thirds (25)
  of these arcades had the normal leading-trailing magnetic polarity
  arrangement of the active regions in the hemisphere of the arcade, but
  the other third (12) had reversed polarity, their leading flux being
  the trailing-polarity remnant of one or more old active regions and
  their trailing flux being the leading-polarity remnant of one or more
  other old active regions. &gt;From these observations, we conclude:
  (1) The sheared core field in a reversed-polarity arcade must be formed
  by processes in and above the photosphere, not by the emergence of a
  twisted flux rope bodily from below the photosphere. (2) The sheared
  core fields in the normal-polarity arcades were basically the same as
  those in the reversed-polarity arcades: both showed similar sigmoidal
  form and produced similar explosions (similar flares and CMEs). (3)
  Hence, the sheared core fields in normal-polarity mature arcades are
  likely formed mainly by the same processes as in reversed-polarity
  arcades. (4) These processes should be discernible in high-resolution
  magnetogram sequences and movies of the photosphere, chromosphere, and
  corona such those to come from Solar-B.This work was supported by NASA's
  Science Mission Directorate through its Solar and Heliospheric Physics
  Supporting Research &amp; Technology program and its Heliophysics
  Guest Investigators program.

---------------------------------------------------------
Title: Recursive Narrowcmes Within a Coronal Streamer
Authors: Bemporad, A.; Sterling, A. C.; Moore, R. L.; Poletto, G.
2005ESASP.600E.153B    Altcode: 2005ESPM...11..153B; 2005dysu.confE.153B
  No abstract at ADS

---------------------------------------------------------
Title: A New Variety of Coronal Mass Ejection: Streamer Puffs from
    Compact Ejective Flares
Authors: Bemporad, A.; Sterling, Alphonse C.; Moore, Ronald L.;
   Poletto, G.
2005ApJ...635L.189B    Altcode:
  We report on SOHO UVCS, LASCO, EIT, and MDI observations of a
  series of narrow ejections that occurred at the solar limb. These
  ejections originated from homologous compact flares whose source
  was an island of included polarity located just inside the base of
  a coronal streamer. Some of these ejections result in narrow CMEs
  (“streamer puffs”) that move out along the streamer. These streamer
  puffs differ from “streamer blowout” CMEs in that (1) while the
  streamer is transiently inflated by the puff, it is not disrupted, and
  (2) each puff comes from a compact explosion in the outskirts of the
  streamer arcade, not from an extensive eruption along the main neutral
  line of the streamer arcade. From the observations, we infer that
  each streamer puff is produced by means of the inflation or blowing
  open of an outer loop of the arcade by ejecta from the compact-flare
  explosion in the foot of the loop. So, in terms of their production,
  our streamer puffs are a new variety of CME.

---------------------------------------------------------
Title: Slow-Rise and Fast-Rise Phases of an Erupting Solar Filament,
    and Flare Emission Onset
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2005ApJ...630.1148S    Altcode:
  We observe the eruption of an active-region solar filament on
  1998 July 11 using high time cadence and high spatial resolution
  EUV observations from the TRACE satellite, along with soft X-ray
  images from the soft X-ray telescope (SXT) on the Yohkoh satellite,
  hard X-ray fluxes from the BATSE instrument on the CGRO satellite
  and from the hard X-ray telescope (HXT) on Yohkoh, and ground-based
  magnetograms. We concentrate on the initiation of the eruption in an
  effort to understand the eruption mechanism. Prior to eruption the
  filament undergoes a slow upward movement in a slow-rise phase with an
  approximately constant velocity of ~15 km s<SUP>-1</SUP> that lasts
  about 10 minutes. It then erupts in a fast-rise phase, accelerating
  to a velocity of ~200 km s<SUP>-1</SUP> in about 5 minutes and then
  decelerating to ~150 km s<SUP>-1</SUP> over the next 5 minutes. EUV
  brightenings begin about concurrently with the start of the filament's
  slow rise and remain immediately beneath the rising filament during
  the slow rise; initial soft X-ray brightenings occur at about the same
  time and location. Strong hard X-ray emission begins after the onset
  of the fast rise and does not peak until the filament has traveled
  to a substantial altitude (to a height about equal to the initial
  length of the erupting filament) beyond its initial location. Our
  observations are consistent with the slow-rise phase of the eruption
  resulting from the onset of “tether cutting” reconnection between
  magnetic fields beneath the filament, and the fast rise resulting from
  an explosive increase in the reconnection rate or by catastrophic
  destabilization of the overlying filament-carrying fields. About 2
  days prior to the event, new flux emerged near the location of the
  initial brightenings, and this recently emerged flux could have been
  a catalyst for initiating the tether-cutting reconnection. With the
  exception of the sudden transition from the slow-rise phase to the
  fast-rise phase in our event, our filament's height-time profile is
  qualitatively similar to the plot of the erupting flux rope height as
  a function of time recently computed by Chen and Shibata for a model
  in which the eruption is triggered by reconnection between an emerging
  field and another field under the flux rope.

---------------------------------------------------------
Title: Shape and Reconnection of the Exploding Magnetic Field in
    the Onset of CMEs
Authors: Moore, R. L.; Sterling, A. C.; Falconer, D. A.; Gary, G. A.
2005AGUSMSH54B..01M    Altcode:
  From chromospheric and coronal images and line-of-sight and vector
  magnetograms of magnetic regions that produce CMEs, and from
  chromospheric and coronal movies of the onsets of CME eruptions,
  it appears that the magnetic field that explodes to drive the CME
  is initially the strongly sheared core of a magnetic arcade encasing
  a polarity dividing line in the magnetic flux. Before or during the
  onset of the explosion, the sheared core field becomes a flux rope,
  often carrying chromospheric material within it. For the erupting flux
  rope to drive the explosion, that is, for its magnetic energy content
  to decrease in the explosion, the flux rope's cross-sectional area
  must increase faster than its length. For instance, for isotropic
  expansion, the area increases as the square of the length, and the
  magnetic energy content of the flux rope decreases as the inverse of
  the length. The instability that initiates the eruption of the flux
  rope might be an ideal MHD kink instability, or might involve runaway
  tether-cutting reconnection. The reconnection begins below the flux
  rope (internal to the arcade) when the overall field configuration
  of the region is effectively that of a single bipole. When the flux
  rope resides in a multi-bipolar configuration having a magnetic null
  above the flux rope, the runaway tether-cutting reconnection might
  begin either below the flux rope or at the null above (external to)
  the arcade. We present examples of observed CME onsets that illustrate
  the above alternatives. In each example, reconnection below the flux
  rope begins early in the eruption. This indicates that internal
  tether cutting reconnection (classic tether-cutting reconnection)
  is important in unleashing the CME explosion in all cases, including
  those in which the explosion may be triggered by MHD kinking or by
  external reconnection (classic breakout reconnection).

---------------------------------------------------------
Title: Flare Emission Onset in the Slow-Rise and Fast-Rise Phases
    of an Erupting Solar Filament Observed with TRACE
Authors: Sterling, A. C.; Moore, R. L.
2005AGUSMSP44A..02S    Altcode:
  We observe the eruption of an active-region solar filament of 1998
  July~11 using high time cadence and high spatial resolution EUV
  observations from the TRACE satellite, along with soft X-ray images
  from the soft X-ray telescope (SXT) on the Yohkoh satellite, hard X-ray
  fluxes from the BATSE instrument on the ( CGRO) satellite and from the
  hard X-ray telescope (HXT) on Yohkoh, and ground-based magnetograms. We
  concentrate on the initiation of the eruption in an effort to
  understand the eruption mechanism. First the filament undergoes slow
  upward movement in a "slow rise" phase with an approximately constant
  velocity of ≍ 15~km~s-1 that lasts about 10~min, and then it erupts
  in a "fast-rise" phase, reaching a velocity of ≍ 200~km~s-1 in about
  5~min, followed by a period of deceleration. EUV brightenings begin just
  before the start of the filament's slow rise, and remain immediately
  beneath the rising filament during the slow rise; initial soft X-ray
  brightenings occur at about the same time and location. Strong hard
  X-ray emission begins after the onset of the fast rise, and does not
  peak until the filament has traveled a substantial altitude (to a
  height about equal to the initial length of the erupting filament)
  beyond its initial location. Our observations are consistent with
  the slow-rise phase of the eruption resulting from the onset of
  "tether cutting" reconnection between magnetic fields beneath the
  filament, and the fast rise resulting from an explosive increase
  in the reconnection rate or by catastrophic destabilization of the
  overlying filament-carrying fields. About two days prior to the event
  new flux emerged near the location of the initial brightenings, and
  this recently-emerged flux could have been a catalyst for initiating
  the tether-cutting reconnection. With the exception of the initial
  slow rise, our findings qualitatively agree with the prediction for
  erupting-flux-rope height as a function of time in a model discussed
  by Chen &amp; Shibata~(2000) based on reconnection between emerging
  flux and a flux rope. NASA supported this work through NASA SR&amp;T
  and SEC GI grants.

---------------------------------------------------------
Title: X-Ray and EUV Observations of CME Eruption Onset
Authors: Sterling, Alphonse C.
2005IAUS..226...27S    Altcode:
  Why CMEs erupt is a major outstanding puzzle of solar
  physics. Signatures observable at the earliest stages of eruption
  onset may hold precious clues about the onset mechanism. We summarize
  and discuss observations from SOHO/EIT in EUV and from Yohkoh/SXT
  in soft X-rays of the pre-eruption and eruption phases of three CME
  expulsions, along with the eruptions' magnetic setting inferred from
  SOHO/MDI magnetograms. Our events involve clearly-observable filament
  eruptions and multiple neutral lines, and we use the magnetic settings
  and motions of the filaments to help infer the geometry and behavior of
  the associated erupting magnetic fields. Pre-eruption and early-eruption
  signatures include a relatively slow filament rise prior to eruption,
  and intensity dimmings and brightenings, both in the immediate
  neighborhood of the "core" (location of greatest magnetic shear)
  of the erupting fields and at locations remote from the core. These
  signatures and their relative timings place observational constraints
  on eruption mechanisms; our recent work has focused on implications
  for the so-called "tether cutting" and "breakout" models, but the same
  observational constraints are applicable to any model.

---------------------------------------------------------
Title: Tether-Cutting Energetics of a Solar Quiet Region Prominence
    Eruption
Authors: Sterling, A. C.
2004ASPC..325..395S    Altcode:
  We study the morphology and energetics of a slowly-evolving quiet
  region solar prominence eruption occurring on 1999 February 8-9 in the
  solar north polar crown region, using ion{Fe{xv}} EUV 284 AA data from
  the EUV Imaging Telescope (EIT) on SOHO and soft X-ray data from the
  soft X-ray telescope (SXT) on Yohkoh. After rising at approximately 1
  kmps for about six hours, the prominence accelerates to a velocity of
  approximately 10 kmps leaving behind EUV and soft X-ray loop arcades
  of a weak flare in its source region. These flare brightenings are
  consistent with “tether-cutting” reconnection occurring beneath the
  rising prominence, but they only become apparent about two hours after
  the prominence's acceleration. Nonetheless, via energetic arguments
  we show that tether cutting could have been occurring nearer the
  time of the start of the fast rise, but not yet discernible in SXT
  images. Therefore we are unable to assess whether tether cutting was
  responsible for the the prominence's acceleration from these data alone.

---------------------------------------------------------
Title: The Relationship between Prominence Eruptions and Global
    Coronal Waves
Authors: Attrill, G. D. R.; Harra, L. K.; Matthews, S. A.; Foley,
   C. R.; Sterling, A. C.
2004ASPC..325..409A    Altcode:
  There has been much debate over the physical mechanism for producing
  global coronal waves (`EIT waves'). In this work, we investigate
  whether filament eruptions are directly associated with coronal
  waves. We analyse 45 coronal waves and search for evidence of
  filament eruptions. We used SOHO-EIT data, and EIT data along with
  any available ground-based Hα data to search for filament eruptions,
  and found that more than 50 % of coronal waves are clearly associated
  with eruptions. The speeds of the coronal waves, and the filament
  eruptions are similar. We discuss the implications of these results.

---------------------------------------------------------
Title: External and Internal Reconnection in Two Filament-Carrying
    Magnetic Cavity Solar Eruptions
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2004ApJ...613.1221S    Altcode:
  We observe two near-limb solar filament eruptions, one of 2000 February
  26 and the other of 2002 January 4. For both we use 195 Å Fe XII images
  from the Extreme-Ultraviolet Imaging Telescope (EIT) and magnetograms
  from the Michelson Doppler Imager (MDI), both of which are on the
  Solar and Heliospheric Observatory (SOHO). For the earlier event
  we also use soft X-ray telescope (SXT), hard X-ray telescope (HXT),
  and Bragg Crystal Spectrometer (BCS) data from the Yohkoh satellite,
  and hard X-ray data from the BATSE experiment on the Compton Gamma
  Ray Observatory (CGRO). Both events occur in quadrupolar magnetic
  regions, and both have coronal features that we infer belong to the
  same magnetic cavity structures as the filaments. In both cases, the
  cavity and filament first rise slowly at ~10 km s<SUP>-1</SUP> prior
  to eruption and then accelerate to ~100 km s<SUP>-1</SUP> during the
  eruption, although the slow-rise movement for the higher altitude cavity
  elements is clearer in the later event. We estimate that both filaments
  and both cavities contain masses of ~10<SUP>14</SUP>-10<SUP>15</SUP> and
  ~10<SUP>15</SUP>-10<SUP>16</SUP> g, respectively. We consider whether
  two specific magnetic reconnection-based models for eruption onset,
  the “tether cutting” and the “breakout” models, are consistent
  with our observations. In the earlier event, soft X-rays from SXT
  show an intensity increase during the 12 minute interval over which
  fast eruption begins, which is consistent with tether-cutting-model
  predictions. Substantial hard X-rays, however, do not occur until
  after fast eruption is underway, and so this is a constraint the
  tether-cutting model must satisfy. During the same 12 minute interval
  over which fast eruption begins, there are brightenings and topological
  changes in the corona indicative of high-altitude reconnection early
  in the eruption, and this is consistent with breakout predictions. In
  both eruptions, the state of the overlying loops at the time of onset
  of the fast-rise phase of the corresponding filament can be compared
  with expectations from the breakout model, thereby setting constraints
  that the breakout model must meet. Our findings are consistent with
  both runaway tether-cutting-type reconnection and fast breakout-type
  reconnection, occurring early in the fast phase of the February eruption
  and with both types of reconnection being important in unleashing
  the explosion, but we are not able to say which, if either, type of
  reconnection actually triggered the fast phase. In any case, we have
  found specific constraints that either model, or any other model,
  must satisfy if correct.

---------------------------------------------------------
Title: External and Internal Reconnection in Two Filament-Carrying
    Magnetic-Cavity Solar Eruptions
Authors: Sterling, A. C.; Moore, R. L.
2004AAS...204.1804S    Altcode: 2004BAAS...36..683S
  We observe two near-limb solar filament eruptions, one of 2000 February
  26 and the other of 2002 January 4, using 195 Å Fe xii\ images from
  SOHO/EIT and magnetograms from SOHO/MDI\@. For the earlier event
  we also use soft X-ray data from Yohkoh/SXT, and hard X-ray data
  from Yohkoh/HXT and CGRO/BATSE\@. Both events occur in quadrupolar
  magnetic regions, and both have coronal features belonging to the same
  magnetic-cavity-structures as the filaments. In both cases the cavity
  and filament have a slow-rise phase of ∼ 10 km s<SUP>-1</SUP> prior to
  eruption, followed by a fast-rise phase of ∼ 100 km s<SUP>-1</SUP>
  during eruption. We estimate both filaments and both cavities to
  contain masses of ∼ 10<SUP>14-15</SUP> g and ∼ 10<SUP>15-16</SUP>
  g, respectively. We consider two specific magnetic-reconnection-based
  models for eruption onset, the “tether cutting” and the “breakout”
  models. In the earlier event SXT images show an intensity increase
  during the 12-minute interval over which the fast phase begins,
  consistent with tether-cutting. Substantial hard X-rays, however,
  do not occur until after fast eruption is underway, which provides
  a constraint on the tether-cutting model. Also around the time fast
  eruption begins there are brightenings and topological changes in
  the corona indicative of high-altitude reconnection, consistent with
  breakout. In both eruptions, however, fast rise onset occurs while
  cavity-related coronal loops are still evolving from “closed” to
  “open,” providing constraints on the breakout model. Therefore our
  findings are consistent with aspects of both models, but we cannot
  say which, if either, mechanism triggered the fast phase. We have
  also found specific constraints that either model, or any other
  eruption-onset model, must satisfy if correct. NASA supported this
  work through SR&amp;T and SEC GI grants.

---------------------------------------------------------
Title: Evidence for Gradual External Reconnection before Explosive
    Eruption of a Solar Filament
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2004ApJ...602.1024S    Altcode:
  We observe a slowly evolving quiet-region solar eruption of 1999
  April 18, using extreme-ultraviolet (EUV) images from the EUV
  Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
  (SOHO) and soft X-ray images from the Soft X-ray Telescope (SXT) on
  Yohkoh. Using difference images, in which an early image is subtracted
  from later images, we examine dimmings and brightenings in the region
  for evidence of the eruption mechanism. A filament rose slowly at
  about 1 km s<SUP>-1</SUP> for 6 hours before being rapidly ejected at
  about 16 km s<SUP>-1</SUP>, leaving flare brightenings and postflare
  loops in its wake. Magnetograms from the Michelson Doppler Imager
  (MDI) on SOHO show that the eruption occurred in a large quadrupolar
  magnetic region with the filament located on the neutral line of the
  quadrupole's central inner lobe between the inner two of the four
  polarity domains. In step with the slow rise, subtle EIT dimmings
  commence and gradually increase over the two polarity domains on one
  side of the filament, i.e., in some of the loops of one of the two
  sidelobes of the quadrupole. Concurrently, soft X-ray brightenings
  gradually increase in both sidelobes. Both of these effects suggest
  heating in the sidelobe magnetic arcades, which gradually increase
  over several hours before the fast eruption. Also, during the slow
  pre-eruption phase, SXT dimmings gradually increase in the feet and
  legs of the central lobe, indicating expansion of the central-lobe
  magnetic arcade enveloping the filament. During the rapid ejection,
  these dimmings rapidly grow in darkness and in area, especially in
  the ends of the sigmoid field that erupts with the filament, and flare
  brightenings begin underneath the fast-moving but still low-altitude
  filament. We consider two models for explaining the eruption:
  “breakout,” which says that reconnection occurs high above the
  filament prior to eruption, and “tether cutting,” which says that
  the eruption is unleashed by reconnection beneath the filament. The
  pre-eruption evolution is consistent with gradual breakout that led to
  (and perhaps caused) the fast eruption. Tether-cutting reconnection
  below the filament begins early in the rapid ejection, but our data are
  not complete enough to determine whether this reconnection began early
  enough to be the cause of the fast-phase onset. Thus, our observations
  are consistent with gradual breakout reconnection causing the long slow
  rise of the filament, but allow the cause of the sudden onset of the
  explosive fast phase to be either a jump in the breakout reconnection
  rate or the onset of runaway tether-cutting reconnection, or both.

---------------------------------------------------------
Title: Solar Spicules: Prospects for Breakthroughs in Understanding
    with Solar-B
Authors: Sterling, A.
2004cosp...35.2435S    Altcode: 2004cosp.meet.2435S
  Spicules densely populate the lower solar atmosphere; any image or
  movie of the chromosphere shows a plethora of them or their "cousins,"
  such as mottles or fibrils. Yet despite several decades of effort we
  still do not know the mechanism that generates them, or how important
  their contribution is to the material and energy balance of the overall
  solar atmosphere. Solar-B will provide exciting new chromospheric
  observations at high time- and spatial-resolution, along with associated
  quality magnetic field data, that promise to open doors to revolutionary
  breakthroughs in spicule research. In this presentation we will review
  the current observational and theoretical status of spicule studies,
  and discuss prospects for advances in spicule understanding during
  the Solar-B era.

---------------------------------------------------------
Title: Solar 'EIT Waves' - What are They?
Authors: Harra, L. K.; Sterling, A. C.
2004IAUS..219..498H    Altcode: 2003IAUS..219E..65H
  Using spectral data from the Coronal Diagnostic Spectrometer (CDS)
  instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft
  we observe a coronal wave feature which occurred in association with a
  solar eruption and flare on 1998 June~13. EUV images from the Transition
  Region and Coronal Explorer (TRACE) satellite show that the coronal
  wave consists of two aspects: (1) a “bright wave” which shows up
  prominently in the TRACE difference images moves with a velocity of
  approximately 200km/s and is followed by a strong dimming region behind
  it and (2) a “weak wave” which is faint in the TRACE images has a
  velocity of about 500km/s and appears to disperse out of the bright
  wave. A “high-velocity” CDS feature however occurs after the weak wave
  passes which appears to correspond to ejection of cool filament-like
  material in TRACE images. Our observations have similarities with a
  numerical simulation model of coronal waves presented by Chen etal
  (2002) who suggests that coronal waves consist of a faster-propagating
  piston-driven portion and a more slowly-propagating portion due to
  the opening of field lines associated with an erupting filament.

---------------------------------------------------------
Title: Tether-cutting Energetics of a Solar Quiet-Region Prominence
    Eruption
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2003ApJ...599.1418S    Altcode:
  We study the morphology and energetics of a slowly evolving quiet-region
  solar prominence eruption occurring on 1999 February 8-9 in the solar
  north polar crown region, using soft X-ray data from the soft X-ray
  telescope (SXT) on Yohkoh and Fe XV EUV 284 Å data from the EUV
  Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
  (SOHO). After rising at ~1 km s<SUP>-1</SUP> for about six hours,
  the prominence accelerates to a velocity of ~10 km s<SUP>-1</SUP>,
  leaving behind EUV and soft X-ray loop arcades of a weak flare in
  its source region. Intensity dimmings occur in the eruption region
  cospatially in EUV and soft X-rays, indicating that the dimmings
  result from a depletion of material. Over the first two hours of
  the prominence's rapid rise, flarelike brightenings occur beneath
  the rising prominence that might correspond to “tether-cutting”
  magnetic reconnection. These brightenings have heating requirements of
  up to ~10<SUP>28</SUP>-10<SUP>29</SUP> ergs, and this is comparable
  to the mechanical energy required for the rising prominence over the
  same time period. If the ratio of mechanical energy to heating energy
  remains constant through the early phase of the eruption, then we infer
  that coronal signatures for the tether cutting may not be apparent
  at or shortly after the start of the fast phase in this or similar
  low-energy eruptions, since the plasma-heating energy levels would
  not exceed that of the background corona.

---------------------------------------------------------
Title: Tether-Cutting Energetics of a Solar Quiet Region Prominence
    Eruption
Authors: Sterling, A. C.; Moore, R. L.
2003AGUFMSH22A0182S    Altcode:
  We study the morphology and energetics of a slowly-evolving quiet region
  solar prominence eruption occurring on 1999 February 8---9 in the
  solar north polar crown region, using Fe~xv EUV 284~Å data from the
  EUV Imaging Telescope (EIT) on SOHO and soft X-ray data from the soft
  X-ray telescope (SXT) on Yohkoh. After rising at ≈ 1~km~s<SUP>-1</SUP>
  for about six hours, the prominence accelerates to a velocity of ≈
  10~km~s<SUP>-1</SUP>, leaving behind EUV and soft X-ray loop arcades
  of a weak flare in its source region. Intensity dimmings occur in the
  eruption region cospatially in EUV and soft X-rays, indicating that
  the dimmings result from a depletion of material. Over the first two
  hours of the prominence's rapid rise, flare-like brightenings occur
  beneath the rising prominence which may correspond to “tether cutting”
  magnetic reconnection. These brightenings have heating requirements of
  up to ∼ 10<SUP>28</SUP>---10<SUP>29</SUP>~ergs, and this is comparable
  to the mechanical energy required for the rising prominence over the
  same time period. If the ratio of mechanical energy to heating energy
  remains constant through the early phase of the eruption, then we infer
  that coronal signatures for the tether cutting may not be apparent at
  or shortly after the start of the faster-rise phase of the prominence
  in this or similar low-energy eruptions, since the plasma-heating
  energy levels would not exceed that of the background corona. Our
  findings have strong implications for the correct use of observations
  in testing theoretical ideas for the onset of solar eruptions.

---------------------------------------------------------
Title: A near-solar-cycle's worth of CME studied with Yohkoh
Authors: Sterling, Alphonse C.
2003ESASP.535..415S    Altcode: 2003iscs.symp..415S
  Yohkoh observed the Sun virtually continuously between August 1991
  and December 2001, covering nearly a complete solar cycle. Among the
  instruments on board was the Soft X-ray Telescope (SXT), which gave
  us fresh perspectives on the dynamic nature of the solar corona. Data
  from Yohkoh, and from SXT in particular, are helping us undertstand
  the nature of Coronal Mass Ejections (CMEs). Although CMEs were a
  topic of interest from the start of the mission, major progress in
  relating Yohkoh observations to CMEs began in late 1996, following the
  start of observations of CMEs with the instruments on board the SOHO
  satellite. Since then we have learned much by combining the direct and
  indirect observations of CMEs from SOHO, with the coronal observations
  from SXT. We now have both an improved understanding of, and new
  questions about: the coronal source regions of CMEs, the nature of
  the material ejected in CMEs, the relation between CMEs and soft X-ray
  flares, and the underlying mechanism driving general solar eruptions.

---------------------------------------------------------
Title: Evidence for Gradual External Reconnection Leading to Explosive
    Eruption of a Solar Filament
Authors: Sterling, A. C.; Moore, R. L.
2003SPD....34.2301S    Altcode: 2003BAAS...35..851S
  We observe a slowly-evolving quiet region solar eruption of 1999
  April 18, using images in 195 Å Fe xii from EIT on SOHO, and in soft
  X-rays from SXT on Yohkoh. We examine dimmings and brightenings in
  difference images, where an early image is subtracted from later
  images, for evidence of the eruption mechanism. A filament rose
  slowly at about 1 km s<SUP>-1</SUP> for six hours before being
  rapidly ejected at about 10 km s<SUP>-1</SUP>, leaving flare
  brightenings and post-flare loops in its wake. SOHO MDI data show
  that the eruption occurred in a quadrupolar region, with the filament
  location splitting the four magnetic sources. During the slow rise,
  subtle EIT dimmings occur between the filament and one of the remote
  magnetic regions. Concurrently, soft X-ray brightenings occur between
  the filament and either remote magnetic region. Both of these effects
  suggest temperature enhancements in magnetic loop systems on either
  side of the filament prior to eruption. Pre-eruption SXT dimmings
  occur on either side of and very close to the slowly rising filament,
  indicating expansion of enveloping magnetic loops. At the start of the
  rapid ejection, intense dimmings occur at the locations evacuated by
  the filament, and brightenings occur underneath the fast-moving but
  still low-altitude filament. We consider two models for explaining
  the eruption: “breakout,” which says that reconnection occurs high
  above the filament prior to eruption, and “tether cutting,” which
  says that the eruption is driven by reconnecting field lines beneath
  the filament. We find that pre-eruption evolution is consistent with
  breakout. Tether cutting-type reconnection occurs during the rapid
  ejection, but our data are not complete enough to determine whether
  that reconnection is the primary cause of the fast-phase onset.

---------------------------------------------------------
Title: Imaging and Spectroscopic Investigations of a Solar Coronal
Wave: Properties of the Wave Front and Associated Erupting Material
Authors: Harra, Louise K.; Sterling, Alphonse C.
2003ApJ...587..429H    Altcode:
  Using spectral data from the Coronal Diagnostic Spectrometer (CDS)
  instrument on the Solar and Heliospheric Observatory spacecraft, we
  observe a coronal wave feature (often referred to as an EIT wave) that
  occurred in association with a solar eruption and flare on 1998 June
  13. EUV images from the Transition Region and Coronal Explorer (TRACE)
  satellite show that the coronal wave consists of two aspects: (1) a
  “bright wave,” which shows up prominently in the TRACE difference
  images, moves with a velocity of approximately 200 km s<SUP>-1</SUP>,
  and is followed by a strong dimming region behind it and (2) a “weak
  wave,” which is faint in the TRACE images, has a velocity of about 500
  km s<SUP>-1</SUP>, and appears to disperse out of the bright wave. The
  weak wave passes through the CDS field of view but shows little or
  no line-of-sight motions in CDS spectra (velocities less than about
  10 km s<SUP>-1</SUP>). Only a small portion of the bright wave passes
  the CDS field of view, with the spectral lines showing insignificant
  shifts. A high-velocity CDS feature, however, occurs after the weak wave
  passes, which appears to correspond to ejection of cool, filament-like
  material in TRACE images. Our observations have similarities with
  a numerical simulation model of coronal waves presented by Chen et
  al., who suggest that coronal waves consist of a faster propagating,
  piston-driven portion and a more slowly propagating portion due to
  the opening of field lines associated with an erupting filament.

---------------------------------------------------------
Title: Doppler Detection of Material Outflows from Coronal Intensity
    “Dimming Regions” During Coronal Mass Ejection Onset
Authors: Sterling, A.; Harra, Louise
2002AAS...200.3709S    Altcode: 2002BAAS...34..696S
  “Coronal dimmings,” localized regions showing a precipitous drop in
  EUV or X-ray emission, are a key coronal signature of the sources of
  Coronal Mass Ejections (CMEs). Researchers often assume that dimmings
  result from a depletion of coronal material (i.e., a decrease in density
  along the line-of-sight), even when no obvious moving structure can be
  detected in images. Yet, this explanation has not been unambiguously
  established; in principle the dimmings could, for example, be due
  to a dramatic change in the temperature of the emitting material
  instead. Here we present the most direct evidence to-date that the
  dimmings result from mass loss, by observing Doppler motions of material
  leaving the regions as they dim. Using spectral data from the Coronal
  Diagnostic Spectrometer (CDS) on SOHO, we observe Doppler shifts in
  two different events. One of these, from 1998 March 31 near 9 UT,
  was near the solar limb and was associated with a CME traveling in the
  plane of the sky, while the other event, from 1999 July 19 near 1:50
  UT, was on the solar disk and was associated with an Earth-directed
  “halo” CME\@. The limb event shows Doppler signatures of ≈ 30 km
  s<SUP>-1</SUP> in coronal (Fe xvi and Mg ix) emission lines, where the
  enhanced velocities coincide with the locations of coronal dimming. An
  “EIT wave” accompanies the disk event, and a dimming region behind
  the wave shows strong blue-shifted Doppler signatures of ≈ 100 km
  s<SUP>-1</SUP> in the O v transition region line. These results provide
  strong evidence that material from the dimming regions feeds into
  the CMEs. This work was supported by NASA's SR&amp;T and GI Programs,
  and by PPARC.

---------------------------------------------------------
Title: SXT and EIT Observations of A Quiet Region Large-Scale
Eruption: Implications for Eruption Theories
Authors: Sterling, A. C.; Moore, R. L.; Thompson, B. J.
2002mwoc.conf..165S    Altcode:
  We present Yohkoh/SXT and SOHO/EIT observations of a set of slow, large
  scale, quiet-region solar eruptions. In SXT data, these events seem to
  appear “out of nothing,” indicating that they are associated initially
  with weak magnetic fields and corresponding low heating rates. These
  events evolve relatively slowly, affording us an opportunity to
  examine in detail their development. We look for signatures of the
  start of the eruptions through intensity variations, physical motions,
  and dimming signatures in the SXT and EIT data. In particular, we look
  to see whether the earliest signatures are brightenings occurring in
  the “core” region (i.e., the location where the magnetic shear is
  strongest and the post-flare loops develop); such early brightenings in
  the core could be indicative of a “tether-cutting” process, whereby
  the eruption is instigated by magnetic reconnection among highly-sheared
  core fields. In our best-observed case, we find motions of the core
  fields beginning well before brightenings in the core. This is new
  evidence that tether-cutting is not the primary mechanism operating
  in solar eruptions. Rather, our observations are more consistent with
  the eruption process known as the “breakout model” (Antiochos et
  al. 1999), which holds that the eruption results from initial slow
  magnetic reconnections occurring high above (far from) the core region.

---------------------------------------------------------
Title: Contagious Coronal Heating from Recurring Emergence of
    Magnetic Flux
Authors: Moore, R. L.; Falconer, D. A.; Sterling, A. C.
2002mwoc.conf...39M    Altcode:
  For each of six old bipolar active regions, we present and interpret
  Yohkoh/SXT and SOHO/MDI observations of the development, over several
  days, of enhanced coronal heating in and around the old bipole in
  response to new magnetic flux emergence within the old bipole. The
  observations show: 1. In each active region, new flux emerges in the
  equatorward side of the old bipole, around a lone remaining leading
  sunspot and/or on the equatorward end of the neutral line of the old
  bipole. 2. The emerging field is marked by intense internal coronal
  heating, and enhanced coronal heating occurs in extended loops stemming
  from the emergence site. 3. In five of the six cases, a "rooster tail"
  of coronal loops in the poleward extent of the old bipole also brightens
  in response to the flux emergence. 4. There are episodes of enhanced
  coronal heating in surrounding magnetic fields that are contiguous
  with the old bipole but are not directly connected to the emerging
  field. From these observations, we suggest that the accommodation
  of localized newly emerged flux within an old active region entails
  far reaching adjustments in the 3D magnetic field throughout the
  active region and in surrounding fields in which the active region is
  embedded, and that these adjustments produce the extensive enhanced
  coronal heating. We Also Note That The Reason For The recurrence
  of flux emergence in old active regions may be that active-region
  flux tends to emerge in giant-cell convection downflows. If so, the
  poleward "rooster tail" is a coronal flag of a long-lasting downflow
  in the convection zone. This work was funded by NASA's Office of Space
  Science through the Solar Physics Supporting Research and Technology
  Program and the Sun-Earth Connection Guest Investigator Program.

---------------------------------------------------------
Title: Hα Proxies for EIT Crinkles: Further Evidence for Preflare
    “Breakout”-Type Activity in an Ejective Solar Eruption
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Qiu, Jiong; Wang,
   Haimin
2001ApJ...561.1116S    Altcode:
  We present Hα observations from Big Bear Solar Observatory of an
  eruptive flare in NOAA Active Region 8210, occurring near 22:30 UT
  on 1998 May 1. Previously, using the EUV Imaging Telescope (EIT)
  on the SOHO spacecraft, we found that a pattern of transient,
  localized brightenings, which we call “EIT crinkles,” appears in
  the neighborhood of the eruption near the time of flare onset. These
  EIT crinkles occur at a location in the active region well separated
  from the sheared core magnetic fields, which is where the most intense
  features of the eruption are concentrated. We also previously found
  that high-cadence images from the Soft X-ray Telescope (SXT) on
  Yohkoh indicate that soft X-ray intensity enhancements in the core
  begin after the start of the EIT crinkles. With the Hα data, we find
  remote flare brightening counterparts to the EIT crinkles. Light curves
  as functions of time of various areas of the active region show that
  several of the remote flare brightenings undergo intensity increases
  prior to the onset of principal brightenings in the core region,
  consistent with our earlier findings from EIT and SXT data. These timing
  relationships are consistent with the eruption onset mechanism known
  as the breakout model, introduced by Antiochos and colleagues, which
  proposes that eruptions begin with reconnection at a magnetic null high
  above the core region. Our observations are also consistent with other
  proposed mechanisms that do not involve early reconnection in the core
  region. As a corollary, our observations are not consistent with the
  so-called tether-cutting models, which say that the eruption begins with
  reconnection in the core. The Hα data further show that a filament in
  the core region becomes activated near the time of EIT crinkle onset,
  but little if any of the filament actually erupts, despite the presence
  of a halo coronal mass ejection (CME) associated with this event.

---------------------------------------------------------
Title: Material Outflows from Coronal Intensity “Dimming Regions”
    during Coronal Mass Ejection Onset
Authors: Harra, Louise K.; Sterling, Alphonse C.
2001ApJ...561L.215H    Altcode:
  One signature of expulsion of coronal mass ejections (CMEs) from the
  solar corona is the appearance of transient intensity dimmings in
  coronal images. These dimmings have generally been assumed to be due
  to discharge of CME material from the corona, and thus the “dimming
  regions” are thought of as an important signature of the sources of
  CMEs. We present spectral observations of two dimming regions at the
  time of expulsion of CMEs, using the Coronal Diagnostic Spectrometer
  (CDS) on the SOHO satellite. One of the dimming regions is at the
  solar limb and associated with a CME traveling in the plane of the
  sky, while the other region is on the solar disk and associated with
  an Earth-directed “halo” CME. From the limb event, we see Doppler
  signatures of ~30 km s<SUP>-1</SUP> in coronal (Fe XVI and Mg IX)
  emission lines, where the enhanced velocities coincide with the
  locations of coronal dimming. This provides direct evidence that the
  dimmings are associated with outflowing material. We also see larger
  (~100 km s<SUP>-1</SUP>) Doppler velocities in transition region (O V
  and He I) emission lines, which are likely to be associated with motions
  of a prominence and loops at transition region temperatures. An “EIT
  wave” accompanies the disk event, and a dimming region behind the wave
  shows strong blueshifted Doppler signatures of ~100 km s<SUP>-1</SUP>
  in O V, suggesting that material from the dimming regions behind the
  wave may be feeding the CME.

---------------------------------------------------------
Title: EIT and SXT Observations of a Quiet-Region Filament Ejection:
    First Eruption, Then Reconnection
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Thompson, Barbara J.
2001ApJ...561L.219S    Altcode:
  We observe a slow-onset quiet-region filament eruption with the EUV
  Imaging Telescope (EIT) on the Solar Heliospheric Observatory (SOHO)
  and the soft X-ray telescope (SXT) on Yohkoh. This event occurred on
  1999 April 18 and was likely the origin of a coronal mass ejection
  detected by SOHO at 08:30 UT on that day. In the EIT observation,
  one-half of the filament shows two stages of evolution: stage 1 is a
  slow, roughly constant upward movement at ~1 km s<SUP>-1</SUP> lasting
  ~6.5 hr, and stage 2 is a rapid upward eruption at ~16 km s<SUP>-1</SUP>
  occurring just before the filament disappears into interplanetary
  space. The other half of the filament shows little motion along the
  line of sight during the time of stage 1 but erupts along with the rest
  of the filament during stage 2. There is no obvious emission from the
  filament in the SXT observation until stage 2; at that time, an arcade
  of EUV and soft X-ray loops forms first at the central location of the
  filament and then expands outward along the length of the filament
  channel. A plot of EUV intensity versus time of the central portion
  of the filament (where the postflare loops initially form) shows a
  flat profile during stage 1 and a rapid upturn after the start of
  stage 2. This light curve is delayed from what would be expected if
  “tether-cutting” reconnection in the core of the erupting region
  were responsible for the initiation of the eruption. Rather, these
  observations suggest that a loss of stability of the magnetic field
  holding the filament initiates the eruption, with reconnection in the
  core region occurring only as a by-product.

---------------------------------------------------------
Title: Internal and external reconnection in a series of homologous
    solar flares
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2001JGR...10625227S    Altcode:
  Using data from the extreme ultraviolet imaging telescope (EIT) on SOHO
  and the soft X-ray telescope (SXT) on Yohkoh, we examine a series of
  morphologically homologous solar flares occurring in National Oceanic
  and Atmospheric Administration (NOAA) active region 8210 over May 1-2,
  1998. An emerging flux region (EFR) impacted against a sunspot to
  the west and next to a coronal hole to the east is the source of the
  repeated flaring. An SXT sigmoid parallels the EFR's neutral line at
  the site of the initial flaring in soft X rays. In EIT each flaring
  episode begins with the formation of a crinkle pattern external to
  the EFR. These EIT crinkles move out from, and then in toward, the
  EFR with velocities ~20 km s<SUP>-1</SUP>. A shrinking and expansion
  of the width of the coronal hole coincides with the crinkle activity,
  and generation and evolution of a postflare loop system begins near the
  time of crinkle formation. Using a schematic based on magnetograms of
  the region, we suggest that these observations are consistent with the
  standard reconnection-based model for solar eruptions but are modified
  by the presence of the additional magnetic fields of the sunspot
  and coronal hole. In the schematic, internal reconnection begins
  inside of the EFR-associated fields, unleashing a flare postflare
  loops, and a coronal mass ejection (CME). External reconnection,
  first occurring between the escaping CME and the coronal hole field
  and second occurring between fields formed as a result of the first
  external reconnection, results in the EIT crinkles and changes in the
  coronal hole boundary. By the end of the second external reconnection,
  the initial setup is reinstated; thus the sequence can repeat, resulting
  in morphologically homologous eruptions. Our inferred magnetic topology
  is similar to that suggested in the “breakout model” of eruptions
  [Antiochos, 1998], although we cannot determine if our eruptions are
  released primarily by the breakout mechanism (external reconnection)
  or, alternatively, primarily by the internal reconnection.

---------------------------------------------------------
Title: EIT Crinkles as Evidence for the Breakout Model of Solar
    Eruptions
Authors: Sterling, Alphonse C.; Moore, Ronald L.
2001ApJ...560.1045S    Altcode:
  We present observations of two homologous flares in NOAA Active Region
  8210 occurring on 1998 May 1 and 2, using EUV data from the EUV Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory,
  high-resolution and high-time cadence images from the soft X-ray
  telescope on Yohkoh, images or fluxes from the hard X-ray telescope
  on Yohkoh and the BATSE experiment on board the Compton Gamma Ray
  Observatory, and Ca XIX soft X-ray spectra from the Bragg crystal
  spectrometer (BCS) on Yohkoh. Magnetograms indicate that the flares
  occurred in a complex magnetic topology, consisting of an emerging flux
  region (EFR) sandwiched between a sunspot to the west and a coronal
  hole to the east. In an earlier study we found that in EIT images,
  both flaring episodes showed the formation of a crinkle-like pattern
  of emission (“EIT crinkles”) occurring in the coronal hole vicinity,
  well away from a central “core field” area near the EFR-sunspot
  boundary. With our expanded data set, here we find that most of the
  energetic activity occurs in the core region in both events, with some
  portions of the core brightening shortly after the onset of the EIT
  crinkles, and other regions of the core brightening several minutes
  later, coincident with a burst of hard X-rays there are no obvious core
  brightenings prior to the onset of the EIT crinkles. These timings are
  consistent with the “breakout model” of solar eruptions, whereby the
  emerging flux is initially constrained by a system of overlying magnetic
  field lines, and is able to erupt only after an opening develops in
  the overlying fields as a consequence of magnetic reconnection at a
  magnetic null point. In our case, the EIT crinkles would be a signature
  of this pre-impulsive phase magnetic reconnection, and brightening of
  the core only occurs after the core fields begin to escape through the
  newly created opening in the overlying fields. Morphology in soft X-ray
  images and properties in hard X-rays differ between the two events,
  with complexities that preclude a simple determination of the dynamics
  in the core at the times of eruption. From the BCS spectra, we find
  that the core region expends energy at a rate of ~10<SUP>26</SUP> ergs
  s<SUP>-1</SUP> during the time of the growth of the EIT crinkles; this
  rate is an upper limit to energy expended in the reconnections opening
  the overlying fields. Energy losses occur at an order of magnitude
  higher rate near the time of the peak of the events. There is little
  evidence of asymmetry in the spectra, consistent with the majority of
  the mass flows occurring normal to the line of sight. Both events have
  similar electron temperature dependencies on time.

---------------------------------------------------------
Title: Velocity observations of an active region during the onset
    phase of a coronal mass ejection
Authors: Harra, Louise K.; Sterling, Alphonse C.
2001ESASP.493..237H    Altcode: 2001sefs.work..237H
  No abstract at ADS

---------------------------------------------------------
Title: Energetics of an Active Region Observed from Helium-Like
    Sulphur Lines
Authors: Watanabe, Tetsuya; Sterling, Alphonse C.; Hudson, Hugh S.;
   Harra, Louise K.
2001SoPh..201...71W    Altcode:
  We report temperature diagnostics derived from helium-like ions of
  sulphur for an active region NOAA 7978 obtained with Bragg Crystal
  Spectrometer (BCS) on board the Yohkoh satellite. For the same
  region we estimate conductive flux downward to the chromosphere by
  the Coronal Diagnostic Spectrometer (CDS) on board the Solar and
  Heliospheric Observatory (SOHO) satellite. This region appeared as a
  region of soft X-ray enhancement in May 1996, underwent a period of
  enhanced activity coinciding with flux emergence between 6 July and
  12 July, and then continued to exist in a nearly flareless state for
  several solar rotations until November 1996. Energy balance of the
  non-flaring active region is basically consistent with a model of
  an arcade of coronal loops having an average loop-top temperature of
  4×10<SUP>6</SUP> K. Energy from flare activity during a period of flux
  emergence is comparable to the energy requirements of the non-flaring
  active region. However, the non-flaring energy is roughly constant
  for the subsequent solar rotations following the birth of the active
  region even after the flare activity essentially subsided. Energy
  partition between flare activity and steady active-region heating
  thus varies significantly over the lifetime of the active region,
  and active-region emission cannot always be identified with flaring.

---------------------------------------------------------
Title: Onset of the Magnetic Explosion in Solar Flares and Coronal
    Mass Ejections
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Hudson, Hugh S.;
   Lemen, James R.
2001ApJ...552..833M    Altcode:
  We present observations of the magnetic field configuration and its
  transformation in six solar eruptive events that show good agreement
  with the standard bipolar model for eruptive flares. The observations
  are X-ray images from the Yohkoh soft X-ray telescope (SXT) and
  magnetograms from Kitt Peak National Solar Observatory, interpreted
  together with the 1-8 Å X-ray flux observed by GOES. The observations
  yield the following interpretation. (1) Each event is a magnetic
  explosion that occurs in an initially closed single bipole in which the
  core field is sheared and twisted in the shape of a sigmoid, having an
  oppositely curved elbow on each end. The arms of the opposite elbows are
  sheared past each other so that they overlap and are crossed low above
  the neutral line in the middle of the bipole. The elbows and arms seen
  in the SXT images are illuminated strands of the sigmoidal core field,
  which is a continuum of sheared/twisted field that fills these strands
  as well as the space between and around them. (2) Although four of
  the explosions are ejective (appearing to blow open the bipole) and
  two are confined (appearing to be arrested within the closed bipole),
  all six begin the same way. In the SXT images, the explosion begins
  with brightening and expansion of the two elbows together with the
  appearance of short bright sheared loops low over the neutral line
  under the crossed arms and, rising up from the crossed arms, long
  strands connecting the far ends of the elbows. (3) All six events are
  single-bipole events in that during the onset and early development
  of the explosion they show no evidence for reconnection between the
  exploding bipole and any surrounding magnetic fields. We conclude that
  in each of our events the magnetic explosion was unleashed by runaway
  tether-cutting via implosive/explosive reconnection in the middle of the
  sigmoid, as in the standard model. The similarity of the onsets of the
  two confined explosions to the onsets of the four ejective explosions
  and their agreement with the model indicate that runaway reconnection
  inside a sheared core field can begin whether or not a separate system
  of overlying fields, or the structure of the bipole itself, allows the
  explosion to be ejective. Because this internal reconnection apparently
  begins at the very start of the sigmoid eruption and grows in step
  with the explosion, we infer that this reconnection is essential for
  the onset and growth of the magnetic explosion in eruptive flares and
  coronal mass ejections.

---------------------------------------------------------
Title: EIT Crinkles as Evidence for the Breakout Model of Solar
    Eruptions
Authors: Sterling, A. C.; Moore, R. L.
2001AGUSM..SH51B02S    Altcode:
  Ejective solar eruptions generally involve: (i) a strong magnetic
  field “core” region, which envelops a magnetic inversion line and
  is the site of the earliest post-flare loop footpoints, and (ii)
  weaker magnetic fields surrounding the core. Determining whether the
  eruption begins in the core or in the surrounding fields is vital
  to understanding the eruption process. Here we discuss observational
  tests of two different models with opposing views on where the eruption
  begins. The “tether-cutting model” suggests that magnetic reconnection
  among fields in the core is the primary cause of the eruption; in this
  case, we expect the earliest signature of the start of the eruption to
  be brightenings inside the core. In contrast, the “breakout model”
  (Antiochos et al.~1999, ApJ, 510, 485) suggests that the eruption
  begins when overlying coronal fields are eroded away by low-energy
  reconnection far from the core; in this case, we would expect initial
  brightenings at sites remote from the core. To test these ideas, we
  examine relative timings of brightenings inside and outside the core
  region of a series of homologous flares in NOAA AR~8210 over 1998
  May 1-2. As we previously reported (Sterling and Moore 2001, JGR, in
  press), these events displayed a crinkle-like pattern of emission in
  EIT 195 images (“EIT crinkles”) near the time of the eruptions, at
  locations remote from the core. We examine the onset of these remote
  brightenings relative to the core brightenings, observing the core
  using EIT data and high-cadence ( ~ 10~s), high resolution (2.5”
  pixels) data from the Soft X-ray Telescope (SXT) on Yohkoh. We find
  that the EIT crinkles precede the core brightenings by several minutes,
  which is consistent with the breakout model, but inconsistent with
  the tether-cutting model. ACS is an NRC---MSFC Research Associate.

---------------------------------------------------------
Title: Sigmoid CME source regions at the Sun: some recent results
Authors: Sterling, A. C.
2000JASTP..62.1427S    Altcode: 2000JATP...62.1427S
  Identifying coronal mass ejection (CME) precursors in the solar corona
  would be an important step in space weather forecasting, as well as
  a vital key to understanding the physics of CMEs. Twisted magnetic
  field structures are suspected of being the source of at least some
  CMEs. These features can appear sigmoid (S or inverse-S) shaped
  in soft X-ray (SXR) images. We review recent observations of these
  structures and their relation to CMEs, using SXR data from the Soft
  X-ray Telescope (SXT) on the Yohkoh satellite, and EUV data from the
  EUV Imaging Telescope (EIT) on the SOHOsatellite. These observations
  indicate that the pre-eruption sigmoid patterns are more prominent
  in SXRs than in EUV, and that sigmoid precursors are present in over
  50% of CMEs. These findings are important for CME research, and may
  potentially be a major component to space weather forecasting. So far,
  however, the studies have been subject to restrictions that will have
  to be relaxed before sigmoid morphology can be used as a reliable
  predictive tool. Moreover, some CMEs do not display a SXR sigmoid
  structure prior to eruption, and some others show no prominent SXR
  signature of any kind before or during eruption.

---------------------------------------------------------
Title: Solar Spicules: A Review of Recent Models and Targets for
    Future Observations - (Invited Review)
Authors: Sterling, Alphonse C.
2000SoPh..196...79S    Altcode:
  Since their discovery over 100 years ago, there have been many
  suggestions for the origin and development of solar spicules. Because
  the velocities of spicules are comparable to the sound and Alfvén
  speeds of the low chromosphere, linear theory cannot fully describe
  them. Consequently, detailed tests of theoretical ideas had to await
  the development of computing power that only became available during
  the 1970s. This work reviews theories for spicules and spicule-like
  features over approximately the past 25 years, with an emphasis on
  the models based on nonlinear numerical simulations. These models have
  given us physical insight into wave propagation in the solar atmosphere,
  and have helped elucidate how such waves, and associated shock waves,
  may be capable of creating motions and structures on magnetic flux tubes
  in the lower solar atmosphere. So far, however, it has been difficult to
  reproduce the most-commonly-quoted parameters for spicules with these
  models, using what appears to be the most suitable input parameters. A
  key impediment to developing satisfactory models has been the lack of
  reliable observational information, which is a consequence of the small
  angular size and transient lifetime of spicules. I close with a list of
  key observational questions to be addressed with space-based satellites,
  such as the currently operating TRACE satellite, and especially the
  upcoming Solar-B mission. Answers to these questions will help determine
  which, if any, of the current models correctly explains spicules.

---------------------------------------------------------
Title: Internal and External Reconnection in a Series of Homologous
    Solar Flares
Authors: Sterling, A. C.; Moore, R. L.
2000SPD....31.1405S    Altcode: 2000BAAS...32..847S
  Using data from the Extreme Ultraviolet Telescope (EIT) on SOHO and
  the Soft X-ray Telescope (SXT) on Yohkoh, we examine a series of
  morphologically homologous solar flares occurring in NOAA AR 8210
  over May 1---2, 1998. An emerging flux region (EFR) impacted against
  a sunspot to the west and next to a coronal hole to the east is the
  source of the repeated flaring. An SXT sigmoid traces the EFR's neutral
  line at the site of the initial flaring in soft X-rays. In EIT, each
  flaring episode begins with the formation of a crinkle pattern external
  to the EFR\@. These EIT crinkles move out from, and then in toward, the
  EFR with velocities ~ 20 km s<SUP>-1</SUP>. A shrinking and expansion
  of the width of the coronal hole coincides with the crinkle activity,
  and generation and evolution of a postflare loop system begins near the
  time of crinkle formation. Using a schematic based on magnetograms of
  the region, we suggest that these observations are consistent with the
  standard reconnection-based model for solar eruptions, but modified
  by the presence of the additional magnetic fields of the sunspot and
  coronal hole. In the schematic, internal reconnection begins inside of
  the EFR-associated fields, unleashing a flare, postflare loops, and a
  CME\@. External reconnection, occurring between the escaping CME and
  the surrounding fields, results in the EIT crinkles and changes in the
  coronal hole boundary. Our inferred magnetic topology is similar to that
  suggested in the ` ` breakout model" of eruptions [Antiochos, 1998],
  although we cannot determine if the ultimate source of the eruptions
  in this case is due to the breakout mechanism or, alternatively, is
  primarily released by the internal reconnection. ACS is an NRC---MSFC
  Research Associate

---------------------------------------------------------
Title: Yohkoh SXT and SOHO EIT Observations of Sigmoid-to-Arcade
    Evolution of Structures Associated with Halo Coronal Mass Ejections
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Thompson, Barbara J.;
   Zarro, Dominic M.
2000ApJ...532..628S    Altcode:
  A subset of the solar-disk counterparts to halo coronal mass ejections
  (CMEs) displays an evolution in soft X-rays (SXR) that is characterized
  by a preflare S-shaped structure, dubbed a “sigmoid,” which evolves
  into a postflare cusp or arcade. We examine the morphological properties
  of the evolution of sigmoids into cusps and arcades for four such
  regions associated with SXR flares, using the Soft X-Ray Telescope
  (SXT) on the Yohkoh satellite and the EUV Imaging Telescope (EIT) on
  the Solar and Heliospheric Observatory (SOHO) satellite. Most of our
  EIT observations are with the 1.5 MK 195 Å Fe XII channel. At most,
  there is only a weak counterpart to the SXR sigmoid in the preflare 195
  Å EUV images, indicating that the preflare sigmoid has a temperature
  greater than 1.5 MK. While more identifiable than in the 195 Å channel,
  a clear preflare sigmoid is also not observed in the 2.0 MK EIT 284 Å
  Fe XV channel. During the time of the flare, however, an EUV sigmoid
  brightens near the location of the SXR preflare sigmoid. Initially
  the SXR sigmoid lies along a magnetic neutral line. As the SXR flare
  progresses, new field lines appear with orientation normal to the
  neutral line and with footpoints rooted in regions of opposite polarity;
  these footpoints are different from those of the preflare sigmoid. The
  cusp structures in SXRs develop from these newly ignited field lines. In
  EIT images, the EUV sigmoid broadens as the flare progresses, forming
  an arcade beneath the SXR cusp. Our findings are consistent with a
  standard picture in which the origin of the flare and CME is caused by
  the eruption of a filament-like feature, with the stretching of field
  lines producing a cusp. We infer that the cusp-producing fields may
  be overlying the sigmoid fields in the preflare phase, but we do not
  directly observe such preflare overlying fields.

---------------------------------------------------------
Title: Variation of Thermal Structure with Height of a Solar Active
    Region Derived from SOHO CDS and YOHKOH BCS Observations
Authors: Sterling, Alphonse C.; Pike, C. D.; Mason, Helen E.; Watanabe,
   Tetsuya; Antiochos, Spiro K.
1999ApJ...524.1096S    Altcode:
  We present observations of NOAA solar Active Region 7999 when it was
  near the west solar limb on 1996 December 2 and 3, using data from
  the Coronal Diagnostic Spectrometer (CDS) experiment on the SOHO
  satellite. Ratios of intensities of 2 MK material (as observed in
  CDS Fe XVI images) to 1 MK material (from CDS Mg IX images) indicate
  that there is a drop in the ratio of the hotter to the cooler material
  with height in the region, up to an altitude of about 10<SUP>5</SUP>
  km. At low altitudes the relative amount of 2 MK emission measure to
  1 MK emission measure ranges from 8 to 10, while the ratio is minimum
  near 10<SUP>5</SUP> km, ranging from 1.3 to 3.5. The decrease with
  height of the CDS ratio qualitatively resembles the decrease in S
  XV election temperature with height (measurable up to ~85,000 km) in
  the same active region obtained from the Bragg crystal spectrometer
  instrument on Yohkoh. The CDS images indicate that the highest S
  XV temperatures and largest CDS ratios correspond to regions of
  microflares, and somewhat lower S XV temperatures and CDS ratios
  correspond to diffuse regions. Above 10<SUP>5</SUP> km, the trend of
  the CDS ratios changes, either increasing or remaining approximately
  constant with height. At these altitudes the CDS images show faint,
  large-scale diffuse structures.

---------------------------------------------------------
Title: SOHO EIT Observations of Extreme-Ultraviolet “Dimming”
    Associated with a Halo Coronal Mass Ejection
Authors: Zarro, Dominic M.; Sterling, Alphonse C.; Thompson, Barbara
   J.; Hudson, Hugh S.; Nitta, Nariaki
1999ApJ...520L.139Z    Altcode:
  A solar flare was observed on 1997 April 7 with the Soft X-ray Telescope
  (SXT) on Yohkoh. The flare was associated with a “halo” coronal
  mass ejection (CME). The flaring region showed areas of reduced soft
  X-ray (SXR) brightness--“dimmings”--that developed prior to the CME
  observed in white light and persisted for several hours following the
  CME. The most prominent dimming regions were located near the ends of
  a preflare SXR S-shaped (sigmoid) feature that disappeared during the
  event, leaving behind a postflare SXR arcade and cusp structure. Based
  upon these and similar soft X-ray observations, it has been postulated
  that SXR dimming regions are the coronal signatures (i.e., remnants)
  of magnetic flux ropes ejected during CMEs. This Letter reports
  new observations of coronal dimming at extreme-ultraviolet (EUV)
  wavelengths obtained with the Extreme-ultraviolet Imaging Telescope
  (EIT) on the Solar and Heliospheric Observatory (SOHO). A series of
  EIT observations in the 195 Å Fe XII wavelength band were obtained
  simultaneously with SXT during the 1997 April 7 flare/CME. The EIT
  observations show that regions of reduced EUV intensity developed at
  the same locations and at the same time as SXR dimming features. The
  decrease in EUV intensity (averaged over each dimming region) occurred
  simultaneously with an increase in EUV emission from flaring loops in
  the active region. We interpret these joint observations within the
  framework of flux-rope eruption as the cause of EUV and SXR coronal
  dimmings, and as the source of at least part of the CME.

---------------------------------------------------------
Title: Electron temperatures of a late-phase solar active region
    from it YOHKOH BCS and SXT observations
Authors: Sterling, Alphonse C.
1999A&A...346..995S    Altcode:
  We deduce electron temperatures in a 2-3 month old active region from
  1996 September and October, using soft X-ray S Xv spectra from the Bragg
  Crystal Spectrometer (BCS) and images from the Soft X-ray Telescope
  (SXT), both on board the Yohkoh satellite. Our observations cover a
  full transit of the region, from before its appearance around the east
  limb until after it disappeared around the west limb. Over most of this
  transit the region is diffuse and extremely quiescent, with few strong
  X-ray intensity enhancements (microflares) seen in plots of the GOES
  flux. During the passage the region's temperature is roughly constant
  at 2.5+/-0.2 MK in S Xv and at 1.9+/-0.1 MK from SXT, with emission
  measures of about 10(48) cm(-3) for both instruments. Temperatures
  obtained from SXT are consistently lower then the S Xv values,
  indicating a multithermal plasma. A high-temperature (&gt;~ 5 MK)
  component, seen in younger active regions, is virtually absent in this
  mature active region. Our findings, combined with earlier work, provide
  a method for estimating S Xv temperatures of structures based on their
  intensity in SXT, even when these structures are not isolated on the Sun
  and hence not directly resolvable with the full-Sun BCS instrument. Our
  work also suggests that old active regions form a fundamental component
  of the quiet-Sun corona during periods of high solar activity.

---------------------------------------------------------
Title: YOHKOH SXT and SOHO EIT Observations of “Sigmoid-to-Arcade”
    Evolution of Structures Associated with Halo CMEs
Authors: Sterling, A. C.; Hudson, H. S.; Thompson, B. J.; Zarro, D. M.
1999AAS...19410107S    Altcode: 1999BAAS...31..999S
  A subset of the solar-disk counterparts to halo coronal mass ejections
  (CMEs) display an evolution in soft X-rays (SXR) characterized by a
  preflare “S”-shaped structure, dubbed a “sigmoid,” evolving into
  a postflare cusp or arcade. We examine the morphological properties
  of the evolution of sigmoids into cusps and arcades for four such
  regions associated with SXR flares, using the Soft X-ray Telescope
  (SXT) on Yohkoh and the 195 Angstroms Fe xii\ channel of the EUV Imaging
  Telescope (EIT) on SOHO. There is, at most, only a weak counterpart to
  the SXR sigmoid in the preflare EUV images, indicating that the preflare
  sigmoid has a temperature &gt;1.5 MK\@. During the time of the flare
  itself, however, an EUV sigmoid brightens near the location of the
  SXR preflare sigmoid. Initially the SXR sigmoid lies along a magnetic
  neutral line. As the SXR flare progresses new field lines appear with
  orientation normal to the neutral line and with footpoints rooted in
  opposite polarity regions; these footpoints are different from those of
  the preflare sigmoid. The cusp structures in SXRs develop from these
  newly-ignited field lines. In EIT images the EUV sigmoid broadens out
  as the flare progresses, forming an arcade which resides beneath the
  SXR cusp. In many respects, our findings are consistent with a standard
  picture where the origin of the flare and CME is due to the eruption
  of a filament-like feature, and the stretching of overlying preflare
  fields produces the cusp. We do not, however, observe these preflare
  overlying fields prior to flare onset. This work was supported by the
  NRL Naval basic research program and NASA.

---------------------------------------------------------
Title: Alfvénic Resonances on Ultraviolet Spicules
Authors: Sterling, Alphonse C.
1998ApJ...508..916S    Altcode:
  We consider the propagation of small-amplitude torsional Alfvén waves
  on spicule-like structures seen at UV and EUV wavelengths. We assume
  that such UV spicules have densities an order of magnitude lower than
  chromospheric spicules. Extending the earlier analysis of Sterling &amp;
  Hollweg, we find that UV spicules can act as resonance cavities, whereby
  Alfvén waves of preferred frequencies have strong transmission into the
  structures. The resonance cavity forms because of the sharp changes in
  Alfvén velocity between the photosphere/chromosphere and the UV spicule
  at the UV spicule's base and between the UV spicule and the corona at
  the top of the UV spicule. For a canonical UV spicule residing on a
  magnetic flux tube of strength B<SUB>0</SUB> = 40 G with length L =
  10,000 km and density ρ = 1.0 × 10<SUP>-14</SUP> g cm<SUP>-3</SUP>,
  we predict a fundamental resonance period of about 35 s, some 3 times
  shorter than for a corresponding chromospheric spicule. Velocities
  along the length of the UV spicule vary from about 30 to 150 km
  s<SUP>-1</SUP>, increasing with height along the structure. Longer UV
  spicules have longer resonance periods and lower rotational velocities,
  and stronger magnetic fields result in shorter resonance periods and
  higher velocities. The same qualitative parameter dependencies also
  hold for chromospheric spicules. Damping flattens out the velocity
  amplitude's profile along the structure and reduces the maximum velocity
  but does not appreciably change the periods of the resonances.

---------------------------------------------------------
Title: X-ray coronal changes during Halo CMEs
Authors: Hudson, H. S.; Lemen, J. R.; St. Cyr, O. C.; Sterling, A. C.;
   Webb, D. F.
1998GeoRL..25.2481H    Altcode:
  Using the Yohkoh soft X-ray images, we examine the coronal structures
  associated with “halo” coronal mass ejections (CMEs). These may
  correspond to events near solar disk center. Starting with a list
  of eleven confirmed halo CMEs over the time range from December 1996
  through May 1997, we find seven with surface features identifiable in
  soft X-rays, with GOES classifications ranging from A1 to M1.3. These
  have a characteristic pattern of sigmoid → arcade development. In each
  of these events, the pre-flare structure disrupted during the flare,
  leaving the appearance of compact transient coronal holes. The four
  remaining events had weak or indistinguishable signatures in the X-ray
  images. For the events for which we could see well-defined coronal
  changes, we confirm our previous result that the estimated mass loss
  inferred from the soft X-ray dimming is a small fraction of typical
  CME masses [Sterling &amp; Hudson 1997].

---------------------------------------------------------
Title: S XV Spectral Properties of an Active Region from the YOHKOH
    Bragg Crystal Spectrometer
Authors: Sterling, A. C.
1998ASSL..229..245S    Altcode: 1998opaf.conf..245S
  No abstract at ADS

---------------------------------------------------------
Title: Numerical simulations of solar spicules
Authors: Sterling, A.
1998ESASP.421...35S    Altcode: 1998sjcp.conf...35S
  No abstract at ADS

---------------------------------------------------------
Title: NOAA 7978: the Last best Old-Cycle Region
Authors: Hudson, H. S.; Labonte, B. J.; Sterling, A. C.; Watanabe, Te.
1998ASSL..229..237H    Altcode: 1998opaf.conf..237H
  No abstract at ADS

---------------------------------------------------------
Title: Yohkoh SXT Observations of X-Ray “Dimming” Associated with
    a Halo Coronal Mass Ejection
Authors: Sterling, Alphonse C.; Hudson, Hugh S.
1997ApJ...491L..55S    Altcode:
  A sudden depletion or intensity “dimming” of the X-ray corona
  sometimes accompanies a solar eruptive flare or coronal mass ejection
  (CME). We have identified a dimming that occurred just prior to a
  “halo” CME, observed on 1997 April 7 using the Soft X-ray Telescope
  (SXT) on Yohkoh. Halo CMEs are prime candidates for “space weather”
  effects. The dimming occurred in compact regions near a flare of
  14 UT on April 7, over a projected area of about 10<SUP>20</SUP>
  cm<SUP>-2</SUP>, and indicate that a mass of a few times 10<SUP>14</SUP>
  g was ejected. This is a lower limit imposed by the obscuration
  of the dimming volume by the brightness of the accompanying flare
  and other factors. Most of the mass deficit comes from two regions
  close to the ends of a preflare S-shaped active-region structure,
  and the resulting dimmings in these regions persisted for more than
  three days following the flare. A cusp-shaped loop--not apparent
  prior to the flare--dominates the emission in the flare decay phase,
  and has a mass comparable to that lost in the dimming regions. Our
  findings are consistent with the source of the CME being a flux rope
  that erupted, leaving behind the dimming regions. The cusp-shaped loop
  probably represents magnetic fields reconfigured or reconnected by the
  eruption. We do not see an X-ray analog of the wavelike disturbance
  evident in SOHO EUV images.

---------------------------------------------------------
Title: X-ray spectral observations of a solar active region corona
Authors: Sterling, Alphonse C.
1997GeoRL..24.2263S    Altcode:
  We study the X-ray flux and electron temperature variation of the corona
  above a solar active region. Electron temperatures are determined using
  data from the S xv channel of the Bragg crystal spectrometer (BCS)
  instrument on board the Yohkoh satellite. The active region, designated
  NOAA AR 7999, rotated from just inside the west solar limb to beyond
  the limb over the period December 2-4, 1996, allowing us to map the
  electron temperature as a function of height in the active region's
  corona. Consistent with previous findings, we find two components to
  the active region coronal temperature, with a hotter (T<SUB>e</SUB>
  ≳5.0 MK) component due to transient flares and microflares, and a
  cooler component present in between the times of the microflares. There
  is a steady decrease in the frequency of occurrence of flares and
  microflares as the occultation progresses, implying that the flaring
  structures are low lying. For the cool component, the average electron
  temperature is about 4.5 MK when the region is just inside the limb,
  and gradually decreases to under 3.0 MK as the region rotates around
  the limb, indicating that temperature decreases with height.

---------------------------------------------------------
Title: Electron Temperatures of the Corona Above a Solar Active
    Region Determined from S XV Spectra
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Watanabe, Tetsuya
1997SPD....28.0136S    Altcode: 1997BAAS...29..885S
  We present high resolution soft X-ray spectral observations of the
  corona above an active region, using data from the Bragg crystal
  spectrometer (BCS) on board the Yohkoh satellite. We observed NOAA AR
  7978 as it rotated beyond the solar limb so that the lower portions of
  the region were occulted. Long integrations from times after the region
  had totally disappeared some days later show a substantial background
  in S xv. Since the background spectrum is featureless, spectral lines
  obtained from the time of occultation must originate from the upper
  corona of the active region. Our results support previous findings that
  the corona consists of two components: a cooler, steady component with
  T_e ~ 3 MK, and a hotter, transient component in excess of 5 MK. This
  hotter component is due to microflares; outside the time of microflares
  there is relatively little or no active region upper coronal plasma
  with T_e gtrsim 3.5 MK. There is evidence for a decrease in T_e with
  height for the cool component.

---------------------------------------------------------
Title: Temporal Variations of Solar Flare Spectral Properties: Hard
    X-Ray Fluxes and Fe XXV, Ca XIX, and Wide-Band Soft X-Ray Fluxes,
    Temperatures, and Emission Measures
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Lemen, James R.;
   Zarro, Dominic A.
1997ApJS..110..115S    Altcode:
  We present fluxes, temperatures, and emission measures for nine
  solar flares, using data from both the Fe XXV and Ca XIX channels
  of the Bragg Crystal Spectrometer (BCS) experiment on the Yohkoh
  satellite and from the wide-band soft X-ray spectrometers on the GOES
  spacecraft. We also present hard X-ray fluxes from the Hard X-ray
  Telescope (HXT) on Yohkoh and the BATSE spectrometer on the Compton
  Gamma-Ray Observatory (CGRO). All events occurred during 1992 and
  ranged in size from GOES class C5 to M2. Three of the events occurred
  near the solar limb. For each flare we give two sets of plots. The
  first set shows flux, electron temperature, and emission measures
  for Fe XXV, Ca XIX, and GOES as functions of time. The second set of
  plots gives log electron temperature as functions of log (emission
  measure)<SUP>1/2</SUP> for these three wavelength ranges; we refer to
  these plots as E<SUP>1/2</SUP>-T diagrams. Hard X-ray flux information
  is included in both sets of plots. Our observations indicate that (1)
  cooler plasmas are located along the legs of, or are evenly distributed
  along, the flaring loops, while hotter plasmas are concentrated near
  the loop tops, (2) peaks in temperature in each of the wavelength
  bands are closely associated with hard X-ray enhancements, and (3)
  the emission from both relatively hot and relatively cool flaring
  plasmas emanates from the same loop or from closely related loops.

---------------------------------------------------------
Title: Electron Temperatures of the Corona Above a Solar Active
    Region Determined from S XV Spectra
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Watanabe, Tetsuya
1997ApJ...479L.149S    Altcode:
  We present the first high-resolution soft X-ray spectral observations of
  the corona above an active region, using the Bragg crystal spectrometer
  (BCS) on board the Yohkoh satellite. We observed NOAA AR 7978 as it
  rotated beyond the solar limb so that the lower portions of the region
  were occulted. Long integrations from times after the region had totally
  disappeared some days later show a substantial, variable background
  in S XV. Since the background spectrum is featureless, spectral lines
  obtained from the time of occultation must originate from the upper
  corona of the active region. Our results support previous findings that
  the active region corona consists of two components: a cooler, steady
  component with T<SUB>e</SUB> ~ 3 MK and a hotter, transient component
  in excess of 5 MK. This hotter component is due to microflares; outside
  the time of microflares there is relatively little or no active region
  upper coronal plasma with T<SUB>e</SUB> &gt;~ 3.5 MK. There is evidence
  for a decrease in T<SUB>e</SUB> with height for the cool component.

---------------------------------------------------------
Title: S XV Spectral Properties of an Active Region from the Yohkoh
    Bragg Crystal Spectrometer
Authors: Sterling, Alphonse C.
1997ApJ...478..807S    Altcode:
  Using the Bragg crystal spectrometer (BCS) on board the Yohkoh
  satellite, we examine the spectral properties of a solar active region
  from 1996 March 22-24. Because the region, NOAA AR 7953, was the
  only one on the Sun over the 3-day period, it was possible to obtain
  quality spectra for that region alone despite the BCS being a full-Sun
  instrument. We analyzed about 150 S XV spectra with integration times
  ranging from about 15 to 3000 s. At least one sub-C-class flare and one
  C-class flare were observed during the period. Lower level transient
  brightenings occur nearly continuously in the region. We find average
  electron temperatures for the nonflaring active region ranging from
  5.5 to 6.2 MK, and an average nonthermal velocity of 43.5 +/- 11.8 km
  s<SUP>-1</SUP> over the 3 days. Temporal variations of S XV values for
  flux and electron temperature, for electron temperature and emission
  measure, and for flux and emission measure are all strongly correlated
  both when the region is nonflaring and when it is flaring. Correlations
  between nonthermal velocity and flux and between nonthermal velocity
  and electron temperature are strong when flares are included in the
  analysis, but the correlation is weak when spectra from times of flares
  are excluded. It is, however, difficult to deconvolve the contribution
  of the source distribution to the nonthermal velocity estimate when
  flux from the region is low.

---------------------------------------------------------
Title: Isolating the Footpoint Characteristics of a Solar Flare Loop
Authors: Harra-Murnion, L. K.; Culhane, J. L.; Hudson, H. S.; Fujiwara,
   T.; Kato, T.; Sterling*, A. C.
1997SoPh..171..103H    Altcode:
  We analyse the physical characteristics of a C5.7 class flare which
  was observed on 27 September, 1993 using data from the soft X-ray
  telescope (SXT), the Bragg crystal spectrometer (BCS), and the hard
  X-ray telescope (HXT) on Yohkoh. The flare takes the form of a simple
  loop which is much brighter at one of its footpoints than anywhere
  else for a period of 2 min. During this time there is an increase in
  the soft X-ray fluxes, and a corresponding peak in hard X-rays. The
  parameters derived from the hard X-ray and soft X-ray spectra and images
  are assumed to be from the footpoint. This flare showed two peaks in
  the non-thermal velocity, the first one simultaneous with the footpoint
  brightening. The non-thermal velocity corresponding to these first few
  minutes is unusually large - by a factor of 80%, 68%, and 26% relative
  to the second peak in the Fexxv, Caxix, and Sxv channels respectively.

---------------------------------------------------------
Title: Active Region Coronal Temperatures from YOHKOH BCS Sxv Spectra
Authors: Sterling, A. C.; Hudson, H. S.; Watanabe, T.
1997IAUJD..19E...9S    Altcode:
  Using the Bragg crystal spectrometer (BCS) on board the Yohkoh
  satellite, we present high resolution soft X-ray spectral observations
  of the corona above an active region. We observed NOAA AR 7978 as
  it rotated beyond the solar limb so that the lower portions of the
  region were occulted. Long integrations from times after the region
  had totally disappeared some days later show a substantial background
  in Sxv. Since the background spectrum is featureless, spectral lines
  obtained from the time of occultation must originate from the upper
  corona of the active region. Our results support previous findings
  that the active region corona consists of two components: a cooler,
  steady component with electron temperature T_e ~3 MK, and a hotter,
  transient component in excess of 5 MK @. This hotter component is due
  to micro-flares; outside the time of micro-flares there is relatively
  little or no active region upper coronal plasma with T_e higher than
  about 3.5 MK @. There is evidence for a decrease in T_e with height
  for the cool component.

---------------------------------------------------------
Title: Active Region Energetics via Yohkoh/BCS and SOHO/CDS
Authors: Watanabe, T.; Sterling, Alphonse C.; Hudson, Hugh S.;
   Harra-Murnion, Louise K.
1997ESASP.404..723W    Altcode: 1997cswn.conf..723W
  No abstract at ADS

---------------------------------------------------------
Title: YOHKOH Observations of Fe XXVI X-Ray Line Emission from
    Solar Flares
Authors: Pike, C. D.; Phillips, K. J. H.; Lang, J.; Sterling, A.;
   Watanabe, T.; Hiei, E.; Culhane, J. L.; Cornille, M.; Dubau, J.
1996ApJ...464..487P    Altcode:
  We report on observations from the Bragg Crystal Spectrometer (B CS)
  on board the Japanese solar flare spacecraft Yohkoh showing Fe XXVI
  Lyα X-ray line emission at 1.78 Å. Some 75 events over a 2 yr period
  between 1991 December 6 and 1993 December 31 have been analyzed. The
  greater sensitivity of the BCS compared with previous instruments has
  enabled such emission to be detected from a wider group of flares than
  has previously been possible. The likelihood of detecting Fe XXVI lines
  in a flare is found to increase sharply with the electron temperature
  obtained from the Fe XXV line spectrum, also observed by the BCS,
  and with GOES X-ray class. The width of the Lyα<SUB>1</SUB>, line,
  measured after the impulsive stage, is greater than that determined by
  thermal Doppler broadening, but this is explained by the nonzero spatial
  extent of flares. Electron temperatures from the intensity ratio of a
  nearby feature due to Fe XXV dielectronic satellites and the Fe XXVI
  Lyα<SUB>1</SUB> line are obtained from new atomic parameters from
  the superstructure code, details of which are described. This revises
  earlier calculations that have been extensively used. Comparison
  of these temperatures with those from the Fe XXV spectra provides
  evidence for a single loose grouping of flares, with the difference
  between the two temperatures ranging from nearly zero to about 20 MK. A
  "superhot" component would seem to be more or less developed according
  to whether the temperature difference is large or nearly zero. Flares
  at both extremes are examined in detail. The gradually varying part
  of the 14-33 keV X-ray emission for these events, as observed by the
  Hard X-ray Telescope on Yohkoh, has a hardness ratio corresponding
  to temperatures and emission measures similar to those from Fe XXVI
  line ratios, pointing to a common origin for their emission. Many of
  the flares studied occurred in particular active regions with great
  magnetic complexity, although Fe XXVI flares do not seem to be a
  distinct class within large X-ray flares.

---------------------------------------------------------
Title: Solar coronal abundances: Some recent X-ray flare observations
Authors: Sterling, Alphonse C.
1996AIPC..374..343S    Altcode: 1996hesp.conf..343S
  I review recent elemental abundance studies from X-ray flare spectra
  obtained with Bragg crystal spectrometer experiments on board the SMM,
  P78-1, and Yohkoh spacecraft. Using the line-to-continuum method, data
  from all three satellites indicate an enhancement of the abundance of
  low-FIP Ca relative to H. But the average magnitude of the enhancement
  is somewhat uncertain. Flare-to-flare variations in the enhancement are
  also seen. Fe flare abundances seem to be close to photospheric values,
  with differing methods giving somewhat differing values. These findings,
  in conjunction with results for S, leave open the possibility that
  H may behave as an intermediate-FIP element or that a more complex
  characterization may apply. Further studies of the Yohkoh data, and
  studies comparing different analysis methods are needed to clarify
  these issues.

---------------------------------------------------------
Title: YOHKOH Observations of an Over-the-Limb Solar Flare with
    Large Spectral Line Shifts
Authors: Sterling, Alphonse C.; Harra-Murnion, Louise K.; Hudson,
   Hugh S.; Lemen, James R.
1996ApJ...464..498S    Altcode:
  We present observations of a solar flare of 1993 April 15 near 9 UT,
  using data from the Yohkoh Bragg crystal spectrometer (BC S) and soft
  X-ray telescope (SXT). Observations from SXT indicate that the flare
  occurred well beyond the solar limb, meaning that our observations
  are restricted to the uppermost portions of the flaring structure. BCS
  spectra show strong bulk blueshifts of the spectral line profiles for a
  short period near the start of the event, followed by an extended period
  of strong bulk redshifts of the line profiles. Concurrent with these
  bulk line shifts, the spectra show "blue wing" asymmetries. Both bulk
  line shifts and blue wings are infrequent characteristics of flares
  observed near the solar limb. Our observations are consistent with
  strong upward mass motions occurring on a high-altitude flaring loop
  oriented edge-on with the Earth. We find nonthermal line broadenings
  in the spectra which are qualitatively and quantitatively similar to
  line broadenings in spectra of disk flares. Near peak intensity of the
  flare, ≤10% of the residual nonthermal broadening can be explained
  by the spatial distribution of the soft X-ray flaring structure.

---------------------------------------------------------
Title: Temporal Variations of Solar Flare Spectral Properties in CA
    XIX and GOES
Authors: Sterling, A. C.; Hudson, H. S.; Lemen, J. R.; Zarro, D. A.
1996AAS...188.1905S    Altcode: 1996BAAS...28..850S
  Since the advent of space borne X-ray observations, there has been
  a strong interest in the nature of the X-ray solar flare. Examining
  the relationships between radiations produced in different portions
  of the X-ray spectrum gives us information on the properties of the
  constituent flaring plasmas. We have studied the joint variation of
  electron temperatures and emission measures for a number of flares in
  two different wavelength ranges, using data from the narrow band Ca xix
  channel (near 3.18 Angstroms) of the Bragg crystal spectrometer (BCS)
  experiment on board the Yohkoh spacecraft, and data from the wide band
  X-ray monitors on the Geostationary Operational Environmental Satellites
  (GOES, covering 0.5---8 Angstroms). A power law relationship often
  describes the relationship between temperature and emission measure
  during the decay phase in both wavelength ranges. According to work of
  Sylwester et al. (1993, A&amp;A 267, 586), energy input parameters and
  physical properties of the flaring loop(s) determine the slope of this
  power law. We find that ratios of Ca xix to GOES slopes generally fall
  between .6 and 1.0, when slopes in both channels are measured during the
  flare decay in each respective wavelength range. This relatively good
  agreement between slopes in the two channels suggests that emissions
  in both wavelength ranges originate from either the same flaring loop,
  or differing loops with similar global properties.

---------------------------------------------------------
Title: Fe XXVI line emission observed by YOHKOH
Authors: Pike, C. D.; Pillips, K. J. H.; Lang, J.; Sterling, A.;
   Watanabe, T.; Hiei, E.; Culhane, J. L.
1996AdSpR..17d..51P    Altcode: 1996AdSpR..17...51P
  Observations from the Bragg Crystal Spectrometer (BCS) on board
  the Japanese solar flare space-craftYohkoh showing Fe xxvi Ly-alpha
  X-ray line emission at about 1.78 Angstroms are reported. Some 75
  events over a two-year-long period between December 1991 and December
  1993 have been analyzed. The greater sensitivity of the BCS compared
  with previous instruments has enabled such emission to be detected
  from a wider group of flares than has previously been possible. The
  likelihood of detecting Fe xxvi lines in a flare is found to increase
  sharply with the electron temperature obtained from the Fe xxv line
  spectrum, also observed by the BCS, and with GOES X-ray class. The
  width of the Lyalpha_1 line, measured after the impulsive stage, is
  rather greater than that determined by thermal Doppler broadening,
  and if the excess broadening is attributed to turbulence, velocities
  of up to 70 km s^-1 are indicated. Comparison of electron temperatures
  obtained from the Fe xxvi spectrum with Fe xxv temperatures provides
  evidence for a single loose grouping of flares, with the difference
  between the two temperatures ranging from nearly zero to about 20 x
  10^6K. A “superhot” component would seem to be more or less developed
  according as the temperature difference is large or nearly zero.

---------------------------------------------------------
Title: YOHKOH SXT and BCS Observations of the "Reconnection Region"
    of a Solar Flare
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Lemen, James R.
1996ASPC..111..177S    Altcode: 1997ASPC..111..177S
  The authors find strong line shifts in Bragg crystal spectrometer
  (BCS) spectra of a flare which occurred well beyond the solar limb on
  1993 April 15. Since the flare is beyond the limb, only the uppermost
  regions of the flare are visible. If reconnection is acting in flares,
  than one may expect that the line shifts from this event are due to
  reconnection jets emanating from above the region of the main flaring
  loops. The authors show, however, that details of the line shifts
  are not consistent with this picture. Rather than being a result of
  reconnection jets, it is more likely that the line shifts are due
  to plasma motions on a flaring loop oriented edge on with respect to
  the Earth.

---------------------------------------------------------
Title: Isolating the Footpoint Characteristics of a Solar Flare Loop
Authors: Harra-Murnion, L. K.; Culhane, J. L.; Fujiwara, T.; Hudson,
   H. S.; Kato, T.; Sterling, A. C.
1996mpsa.conf..527H    Altcode: 1996IAUCo.153..527H
  No abstract at ADS

---------------------------------------------------------
Title: X-ray Observations of an Over-the-Limb Solar Flare with Large
    Spectral Line Shifts
Authors: Sterling, A. C.; Harra-Murnion, L. K.; Hudson, H. S.; Lemen,
   J. R.; Strong, K. T.
1996mpsa.conf..557S    Altcode: 1996IAUCo.153..557S
  No abstract at ADS

---------------------------------------------------------
Title: A Loop Flare Observed by YOHKOH on 1992 July 11
Authors: Khan, Josef I.; Hudson, Hugh S.; Sterling, Alphonse C.;
   Lemen, James R.
1996ASPC..111..162K    Altcode: 1997ASPC..111..162K
  The authors present Yohkoh soft and hard X-ray observations of a
  flare. Soft X-ray morphology shows the structure of this flare to
  be a relatively simple loop. Nonetheless several interesting points
  were found including: (i) bright soft X-ray footpoints persist long
  after completion of the impulsive hard X-ray bursts; (ii) both legs
  and footpoints of the flare loop appear to move together rather than
  apart during the course of the flare; (iii) initially the flare loop
  appears to have a fairly uniform thickness but as the flare progresses
  the loop-top region becomes broader; (iv) 'low energy' hard X-rays
  appear to originate from high in the loop near the loop apex; and (v)
  soft X-ray spectra show strong line asymmetries suggesting the presence
  of upflowing plasma oriented nearly directly towards the Earth.

---------------------------------------------------------
Title: Yohkho Soft X-Ray Spectroscopic Observations of the Bright
    Loop-Top Kernels of Solar Flares
Authors: Khan, Josef I.; Harra-Murnion, Louise K.; Hudson, Hugh S.;
   Lemen, James R.; Sterling, Alphonse C.
1995ApJ...452L.153K    Altcode:
  Observations of solar flares by the Soft X-ray Telescope (SXT) on
  board Yohkoh frequently show strongly enhanced brightenings near the
  tops of the magnetic loops containing hot plasma. The Yohkoh Bragg
  Crystal Spectrometer (BCS) cannot normally make observations of these
  loop-top sources in the absence of contamination by the legs and the
  feet of the loops since it has no spatial resolution. We have overcome
  this limitation by using the solar limb as an occulting edge in a
  sequence of similar flares that occurred over an interval of ~10 hr
  near the west limb on 1992 November 24. The progressive occultation by
  the limb restricts the line of sight to higher and higher altitudes
  during this sequence, with the final event showing only a compact
  source of the type often found at loop tops. BCS observations in Fe
  XXV, Ca XIX, and S XV show that electron temperatures and nonthermal
  velocities in these compact sources are similar to those quantities
  determined for disk flares in previous studies. As with disk flares,
  the nonthermal line broadening persists late into the decay phase
  of the flaring isolated loop tops. Our results favor mechanisms for
  nonthermal-velocity generation that are either independent of height
  or place the source near the apex of the flaring loop. In addition,
  there may be a temporal relationship between the hard X-ray emission
  and the nonthermal velocity, which suggests a possible association
  between the primary energy release of the flare, the nonthermal-velocity
  generation mechanism, and the loop top.

---------------------------------------------------------
Title: Yohkoh Multi-Wavelength Observations of the Bright Loop-Top
    Kernels in Solar Flares
Authors: Sterling, A.; Khan, J.; Harra-Murnion, L.; Hudson, H.;
   Lemen, J.
1995SPD....26.1211S    Altcode: 1995BAAS...27..985S
  No abstract at ADS

---------------------------------------------------------
Title: Fe XXV Temperatures in Flares from the YOHKOH Bragg Crystal
    Spectrometer
Authors: Sterling, Alphonse C.; Doschek, George A.; Pike, C. David
1994ApJ...435..898S    Altcode:
  Studies by Doschek et al. using P78-1 and Solar Maximum Misson
  (SMM) data have shown that the ratio of intensities of the Fe XXV
  and Ca XIX resonance lines can be expressed as a function of Fe XXV
  temperature. Using a more recent data set consisting of 13 flares
  observed by the Bragg crystal spectrometer (BCS) experiment on board
  Yohkoh, we find a nearly identical functional relationship between
  the same resonance line ratios and Fe XXV temperatures. We use this
  functional relationship to obtain resonance line ratio temperatures
  (T<SUB>RLR</SUB>) for each flare in our data set, and compare them
  with temperatures resulting from application of a simple spectral
  fitting method. (T<SUB>SSF</SUB>) to individal Fe XXV spectra. We also
  use a more involved free-parameter spectral fitting method to deduce
  temperatures (T<SUB>FSF</SUB>) from some of these spectra. On average,
  agreement between T<SUB>RLR</SUB> and T<SUB>SSF</SUB> improves as a
  flare progresses in time, with average agreements of 10.0% +/- 5.2%,
  6.4% +/- 5.4%, and 5.0% +/- 3.9% over the rise, peak, and decay phases,
  respectively. Deviations between T<SUB>RLR</SUB> and T<SUB>FSF</SUB>
  are about the same or smaller. Thus, for most analysis purposes, all
  three methods yield virtually identical temperatures in flares. The
  somewhat poorer agreement between T<SUB>SSF</SUB> and T<SUB>RLR</SUB>
  during the earlier phases may be partially a result of difficulties
  in obtaining precise values for temperatures from spectral fits
  when blueshifts and large nonthermal broadenings are present in the
  spectra. Because of the high sensitivity of the Yohkoh BCS compared
  to that of BCS experiments on earlier spacecraft, we can for the first
  time consistently observe the heating phase of flares in Fe XXV.

---------------------------------------------------------
Title: Jets and brightenings generated by energy deposition in the
    middle and upper solar chromosphere
Authors: Sterling, Alphonse C.; Shibata, Kazunari; Mariska, John T.
1994SSRv...70...77S    Altcode:
  Numerical simulations of energy depositions in the middle and upper
  solar chromosphere result in ejection of chromospheric material into
  the corona and heating of the chromospheric gas. These simulations may
  be capable of describing some of the features seen by the soft X-ray
  telescope on board theYohkoh satellite.

---------------------------------------------------------
Title: The 1991 November 9 Flare at 03.2 UT: Observations from YOHKOH
Authors: Doschek, G. A.; Mariska, J. T.; Strong, K. T.; Bentley, R. D.;
   Brown, C. M.; Culhane, J. L.; Lang, J.; Sterling, A. C.; Watanabe, T.
1994ApJ...431..888D    Altcode:
  We discuss X-ray spectra and soft X-ray images of an M1.9 flare that
  occurred on 1991 November 9 near 03.2 UT. These data were obtained with
  instrumentation on the Japanese Yohkoh spacecraft. They cover the entire
  rise phase and peak flare emission, and the beginning of the decay
  phase. We determine the dynamics, temperature, and emission measure
  of the flare as inferred from the X-ray line profiles of resonance
  lines of Fe XXV, Ca XIX, and S XV. We discuss the morphology of the
  flare as inferred from the soft X-ray images. The November 9 flare is
  atypical in that a stronger than usual blueshifted emission component
  (relative to the stationary component) is observed for the resonance
  lines at flare onset. We discuss several methods for deconvolving the
  blueshifted component from the stationary component. The X-ray line
  profiles are consistent with predictions of numerical simulations
  of chromospheric evaporation. The X-ray images reveal a flare with a
  complicated loop geometry that is not fully understood. Many of the
  features in the images are moving upwards at speeds ranging from a
  few km/s to about 800 km/s. The blueshifted emission begins near the
  onset of hard X-ray emission, implying that particle acceleration and
  upflowing plasma have a common energy source.

---------------------------------------------------------
Title: YOHKOH Bragg Crystal Spectrometer(BCS) Observations of the
    6-Feb-1992 Limb Flare
Authors: Sterling, A. C.
1994kofu.symp..131S    Altcode:
  We present Yohkoh BCS observations of a near-limb solar flare of 6
  Feb 1992. SXT images show that the event was composed of at least
  two flaring loops. The first of these to flare had a maximum Fe XXV
  temperature of about 19 MK and no substantial Fe XXVI component, while
  the second flaring loop achieved a Fe XXV temperature in excess of 21
  MK and had a superhot (30--40 MK) Fe XXVI component.

---------------------------------------------------------
Title: YOHKOH Observations of Weak Events Within AR7218
Authors: Linford, G. A.; Hudson, H.; Sterling, A.
1994xspy.conf...49L    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A Resonance Line Rations Method for Determining Flare
    Temperatures Using YOHKOH BCS Spectra
Authors: Sterling, A. C.; Doschek, G.; Mariska, J. T.; Hiei, E.;
   Watanabe, T.
1994xspy.conf..127S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Non-Thermal Effects in Slow Solar Flares
Authors: Hudson, H. S.; Acton, L. W.; Sterling, A. C.; Tsuneta, S.;
   Fishman, J.; Meegan, C.; Paciesas, W.; Wilson, R.
1994xspy.conf..143H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The 1992 January 5 Flare at 13.3 UT: Observations from YOHKOH
Authors: Doschek, G. A.; Strong, K. T.; Bentley, R. D.; Brown, C. M.;
   Culhane, J. L.; Fludra, A.; Hiei, E.; Lang, J.; Mariska, J. T.;
   Phillips, K. J. H.; Pike, C. D.; Sterling, A. C.; Watanabe, T.; Acton,
   L. W.; Bruner, M. E.; Hirayama, T.; Tsuneta, S.; Rolli, E.; Kosugi,
   T.; Yoshimori, M.; Hudson, H. S.; Metcalf, T. R.; Wuelser, J. -P.;
   Uchida, Y.; Ogawara, Y.
1993ApJ...416..845D    Altcode:
  We discuss X-ray spectra and soft X-ray images of an M1.9 flare that
  occurred on 1992 January 5 near 13.3 UT. These data were obtained
  with instrumentation on the Japanese Yohkoh spacecraft. They cover
  the entire rise phase of the flare. To supplement these data we have
  ground-based magnetograms and Hα spectroheliograms. We calculate
  the electron temperature and emission measure of the flare as a
  function of time during the early rise phase using X-ray spectral
  line intensities and line ratios. Using spectral line widths, line
  profile asymmetries, and wavelength shifts due to the Doppler effect,
  we calculate the dynamical properties of the flare. The time development
  of the morphology of the flare, as revealed by the soft X-ray images
  and the Hα spectroheliograms, and the physical quantities inferred
  from the X-ray spectra, are compared with chromospheric evaporation
  models. There is an enhancement of blueshifted emission that is closely
  correlated with the hard X-ray bursts. Heating of one loop in the flare
  is consistent with a conduction-evaporation model, but heating is found
  in several structures that do not appear to be physically associated
  with each other. No standard evaporation model can adequately explain
  all of the observations.

---------------------------------------------------------
Title: Yohkoh observations of plasma upflows during solar flares
Authors: Culhane, J. L.; Phillips, A. T.; Pike, C. D.; Fludra, A.;
   Bentley, R. D.; Bromage, B.; Doschek, G. A.; Hiei, E.; Inda, M.;
   Mariska, J. T.; Phillips, K. J. H.; Sterling, A. C.; Watanabe, T.
1993AdSpR..13i.303C    Altcode: 1993AdSpR..13..303C
  Observations of two flares, an M 2.2 event on 16 December, 1991 and the
  precursor to an X1 flare on 15 November, 1991 are presented. Spectra
  obtained with the Bragg Crystal Spectrometer (BCS) are compared with
  data from the Hard and Soft X-ray Telescopes (HXT, SXT) and the Wide
  Band Spectrometer (WBS) on the satellite. For both events the creation
  of upflowing plasma is detected. While the first event seems to conform
  well to the chromospheric evaporation model for high temperature plasma
  production, the behaviour for the second event is more complex.

---------------------------------------------------------
Title: Determination of coronal abundances of sulphur, calcium and
    iron using the yohkoh bragg crystal spectrometer
Authors: Fludra, A.; Culhane, J. L.; Bentley, R. D.; Doschek, G. A.;
   Hiei, E.; Phillips, K. J. H.; Sterling, A.; Watanabe, T.
1993AdSpR..13i.395F    Altcode: 1993AdSpR..13..395F
  Using spectra from the Bragg Crystal Spectrometer on Yohkoh we have
  derived coronal abundances of sulphur, calcium and iron during several
  flares from the ratio of the flux in the resonance line to the nearby
  continuum. Multi-thermal effects have been taken into account using
  differential emission measure analysis. We have also determined the
  abundance of S in cool active regions during a period of very low solar
  activity. We compare the coronal abundances of S, Ca and Fe with their
  photospheric values.

---------------------------------------------------------
Title: Temperatures in Flares Determined from Fe XXV Spectra,
    Resonance Line Ratios, and GOES X-ray Flux
Authors: Sterling, A. C.; Doschek, G. A.; Pike, C. D.; Hudson, H. S.;
   Lemen, J. R.; Zarro, D. M.
1993BAAS...25.1178S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar Chromospheric and Transition Region Response to Energy
    Deposition in the Middle and Upper Chromosphere
Authors: Sterling, Alphonse C.; Shibata, Kazunari; Mariska, John T.
1993ApJ...407..778S    Altcode:
  A series of numerical simulations modeling the chromosphere and
  transition region response to deposition of thermal energy ranging
  from about 5 x 10 exp 24 to 5 x 10 exp 28 ergs in the middle or upper
  chromosphere is reported. The dissipative effects of heat conduction,
  optically thin radiation losses in the corona, and an approximate
  expression for the radiation losses of lower temperature plasma are
  calculated. In response to the energy deposition, chromospheric material
  is ejected into the corona in the form of pressure gradient generated
  jets, jets with pressure-gradient, and shock-generated components,
  or high-speed gas plugs. Category of ejection depends on the spatial
  and temporal distribution and the magnitude of the input energy source.

---------------------------------------------------------
Title: On the Absolute Abundance of Calcium in Solar Flares
Authors: Sterling, Alphonse C.; Doschek, George A.; Feldman, Uri
1993ApJ...404..394S    Altcode:
  The abundance of calcium relative to hydrogen in soft X-ray-emitting
  solar flare plasmas is determined. Results were obtained for 25
  flares. An average calcium-to-hydrogen abundance of about 5 x 10
  exp -6, which is about a factor of 2 greater than measured for the
  photosphere, is found. This result is consistent with an enhancement
  of low first ionization elements in soft X-ray flare plasmas. For
  one flare, the calcium abundance was higher, at about 1.6 times the
  average results. It is inferred that the calcium abundance can vary
  among flares. Significant variations of the calcium abundance during
  the course of a flare were not detected.

---------------------------------------------------------
Title: Determination of element abundances using the Yohkoh Bragg
    Crystal Spectrometer.
Authors: Fludra, A.; Culhane, J. L.; Bentley, R. D.; Doschek, G. A.;
   Hiei, E.; Phillips, K. J. H.; Sterling, A.; Watanabe, T.
1993uxrs.conf..542F    Altcode: 1993uxsa.conf..542F
  No abstract at ADS

---------------------------------------------------------
Title: Observations of Several Small Flares with the Bragg Crystal
    Spectrometer on YOHKOH
Authors: Culhane, J. Leonard; Fludra, Andrzej; Bentley, Robert D.;
   Doschek, George A.; Watanabe, Tetsuya; Hiei, Eijiro; Lang, James;
   Carter, Martin K.; Mariska, John T.; Phillips, Andrew T.; Phillips,
   Kenneth J. H.; Pike, C. David; Sterling, Alphonse C.
1992PASJ...44L.101C    Altcode:
  We have analysed data from two flares of GOES class C7.1 and C8.5
  observed by the Yohkoh Bragg Crystal Spectrometer. The high sensitivity
  of the Yohkoh instrument allows us to observe the very early stages of
  flare development and to study small events with a high signal-to-noise
  ratio. Spectral fitting programs have been used to derive plasma
  temperatures, emission measures and velocities from spectra of S XV,
  Ca XIX and Fe XXV. Large plasma motions indicative of chromospheric
  evaporation have been found. A more detailed analysis of a flare which
  occurred on 1991 October 30 is presented.

---------------------------------------------------------
Title: YOHKOH Bragg Crystal Spectrometer Observations of the Dynamics
    and Temperature Behavior of a Soft X-Ray Flare
Authors: Doschek, George A.; Mariska, John T.; Watanabe, Tetsuya;
   Hiei, Eijiro; Lang, James; Culhane, J. Leonard; Bentley, Robert D.;
   Brown, Charles M.; Feldman, Uri; Phillips, Andrew T.; Phillips,
   Kenneth J. H.; Sterling, Alphonse C.
1992PASJ...44L..95D    Altcode:
  We describe X-ray spectra of an M1.5 flare that occurred on 1991
  November 9, starting at about 0313 UT. This flare is unusual in that
  very intense blueshifted components are observed in the resonance
  lines of Fe XXV, Ca XIX, and S XV. During the onset of the flare,
  the resonance lines of Ca XIX and Fe XXV are primarily due to
  this blueshifted component, which from the Doppler effect indicates
  line-of-sight speeds and turbulent motions that in combination extend
  up to 800 km s(-1) .

---------------------------------------------------------
Title: Yohkoh BCS Observations of Doppler Shifts Early in Solar Flares
Authors: Mariska, J. T.; Doschek, G. A.; Sterling, A. C.; Culhane,
   J. L.; Hiei, E.; Watanabe, T.; Lang, J.
1992AAS...180.2308M    Altcode: 1992BAAS...24..761M
  No abstract at ADS

---------------------------------------------------------
Title: Time Variation of Solar Flare Temperatures Determined from
    YOHKOH BCS Spectra
Authors: Sterling, A. C.; Doschek, G. A.; Mariska, J. T.; Pike, C. D.;
   Culhane, J. L.; Hiei, E.; Watanabe, T.; YOHKOH BCS Team
1992AAS...180.3001S    Altcode: 1992BAAS...24..775S
  Bragg Crystal Spectrometer (BCS) X-ray spectra analysis from past
  satellite missions indicate that it is possible to estimate temperatures
  in highly ionized flare plasmas to within about 12\ resonance lines
  in different He-like ions. This procedure is particularly valuable
  in cases where other temperature measuring methods are insufficient,
  such as during the rise phase of flares with strong X-ray spectra
  blue shifts. Here we examine this ratio variation in several flares
  using data from the Fe XXV, Ca XIX, and S XV channels of the BCS
  experiment onboard the Yohkoh satellite. We select flares for
  which we have good rise phase data, and calibrate the ratios using
  dielectronic-to-resonance line ratios in selected Fe XXV spectra
  assuming constant elemental abundances in each event. The Yohkoh BCS is
  about an order of magnitude more sensitive than previous X-ray flare
  spectrometers, and is therefore able to examine the early stages of
  flare development in greater detail than previously possible. For this
  study we select events for which we have good rise phase data, but data
  well into the decay phase is available for a number of the selected
  events. This allows us, for the first time, to follow the evolution
  of flare spectra from relatively cool temperatures (~ 12 MK in Fe XXV)
  to previously quoted “typical" flare temperatures (~ 17 MK in Fe XXV).

---------------------------------------------------------
Title: Emergence of Magnetic Flux from the Convection Zone into the
    Solar Atmosphere. I. Linear and Nonlinear Adiabatic Evolution of
    the Convective-Parker Instability
Authors: Nozawa, S.; Shibata, K.; Matsumoto, R.; Sterling, A. C.;
   Tajima, T.; Uchida, Y.; Ferrari, A.; Rosner, R.
1992ApJS...78..267N    Altcode:
  The linear and nonlinear properties of the evolution of emerging
  magnetic flux from the solar convection zone into the photosphere,
  chromosphere, and corona are studied. A linear stability analysis
  of the partially magnetized convection zone is presented. The growth
  rate of this combined convective-Parker instability is found to differ
  significantly from that of the Parker instability in the absence of
  convection. When beta(=pg/pm) is greater than 10 in the initial flux
  sheet, the growth rate increases with horizontal wavenumber, and there
  is no maximum growth rate. A local maximum can occur when the flux
  is initially located near the top of the convection zone. When beta
  is less than 10, the convective-Parker instability behaves like the
  Parker instability for long-wavelength modes, and like the convective
  instability for short-wavelength modes. A 2D MHD code is used to study
  the nonlinear evolution of the system. When the initial flux sheet has
  beta less than 10, the long-wavelength mode dominates the nonlinear
  evolution of the system, independently of the initial perturbation
  wavelength.

---------------------------------------------------------
Title: Numerical Simulations of Microflare Evolution in the Solar
    Transition Region and Corona
Authors: Sterling, Alphonse C.; Mariska, John T.; Shibata, Kazunari;
   Suematsu, Yoshinori
1991ApJ...381..313S    Altcode:
  Several observers report transient ultraviolet brightenings, often
  referred to as microflares, in the solar atmosphere. In this paper,
  the results are presented of a series of one-dimensional numerical
  simulations examining possible relationships between microflares
  and the generation of dynamical chromospheric and transition region
  features. Low-energy and medium-energy microflares eject long-lived
  cool, dense gas plugs into the corona, with the gas plug traversing
  the loop apex in the medium energy case. In the case of high-energy
  microflares, the gas plug is rapidly heated to the temperature of the
  surrounding corona, and the results resemble the dynamics occurring
  in standard solar flare thick-target electron beam models.

---------------------------------------------------------
Title: On the Absolute Abundance of Ca in Solar Flares
Authors: Sterling, A. C.; Doschek, G. A.
1991BAAS...23.1467S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Numerical Studies of Atmospheric Dynamics Driven by Energy
    Deposition in the Chromosphere
Authors: Sterling, A. C.; Mariska, J. T.; Shibata, K.
1991BAAS...23.1029S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Numerical Simulations of Ultraviolet and X-ray Microflares
Authors: Sterling, A. C.; Shibata, K.; Mariska, J. T.
1991LNP...387...71S    Altcode: 1991fpsa.conf...71S
  A series of numerical simulations indicates that thermal energy
  releases of 1025 - 1027 ergs in the middle chromosphere can produce
  ejections into the corona in the form of pressure gradient generated
  jets, jets with pressure gradient and shock generated components, or
  high speed gas plugs. Heating of the chromosphere to X-ray emitting
  temperatures occurs in association with gas plugs, perhaps generating
  X-ray microflares observable by Solar-A. Chromospheric UV-microflares
  can occur in association with some jets, but do not generally occur
  with spicules.

---------------------------------------------------------
Title: Atmospheric Heating in Emerging Flux Regions (With 2 Figures)
Authors: Shibata, K.; Nozawa, S.; Matsumoto, R.; Tajima, T.; Sterling,
   A. C.
1991mcch.conf..609S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Numerical Simulation of Microflare Evolution in the Solar
    Transition Region and Corona (With 4 Figures)
Authors: Sterling, A. C.; Mariska, J. T.
1991mcch.conf..630S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Emergence of Solar Magnetic Flux from the Convection Zone
    into the Photosphere and Chromosphere
Authors: Shibata, K.; Nozawa, S.; Matsumoto, R.; Sterling, A. C.;
   Tajima, T.
1990ApJ...351L..25S    Altcode:
  A two-dimensional MHD code is used to study the nonlinear dynamics
  of solar magnetic flux emerging from the convection zone into the
  photosphere and chromosphere. An isolated horizontal magnetic flux with
  beta of about 4 is initially located in a convectively unstable layer
  (solar convection zone) beneath a two-temperature layered atmosphere
  (solar corona-chromosphere/photosphere). The combined effects of
  convection and magnetic buoyancy carry the magnetic flux from the
  convection zone into the photosphere, where it then expands through
  the photosphere and chromosphere. Gas slides down the expanding loop,
  resulting in its evacuation and subsequent rise due to enhanced
  magnetic buoyancy. Initially, weak convection zone magnetic flux (B
  of about 600 G) is amplified up to 1000 G or more after emerging into
  the photosphere. The resulting velocity fields are similar to those
  observed in arch filament systems.

---------------------------------------------------------
Title: Numerical Simulations of the Rebound Shock Model for Solar
    Spicules
Authors: Sterling, Alphonse C.; Mariska, John T.
1990ApJ...349..647S    Altcode:
  Using time-dependent numerical simulations, the proposed rebound shock
  mechanism for spicules has been examined. At temperatures above a
  critical value, T(c), the radiation is characteristic of the conditions
  in the optically thin corona and near optically thin transition
  region. When T less than T(c), the atmosphere has a radiative cooling
  time, tau(rad) characteristic of chromosphere. The spicule is initiated
  with a quasi-impulsive force in the low chromosphere, which drives a
  train of upward propagating rebound shocks along the rigid magnetic flux
  tube. These shocks then move the transition region upward. The material
  below the displaced transition region has temperatures and densities
  similar to those of spicules when T(c) = 20,000 K or more and tau(rad)
  = 500 s or more, but not when T(c) = 10,000 K, and probably not when
  tau(rad) = 100 s. For all the cases where the cross sectional area
  diverges rapidly with height, the upward velocity of the transition
  region is less than that of spicules. Moreover, the maximum height is
  less than that of average spicules. Taller, higher velocity spicules
  result when the magnetic field cross sectional area is constant. In
  all cases, the rebound shock mechanism produces substantial motions
  and temperature and density variations in chromospheric and transition
  region material. It is suggested that this may be a partial explanation
  for the continuous dynamic state of the lower solar atmosphere.

---------------------------------------------------------
Title: Emergence of Solar Magnetic Flux from the Convection Zone
    into the Photosphere aand Chromosphere
Authors: Sterling, A. C.; Shibata, K.; Nozawa, S.; Matsumoto, R.;
   Tajima, T.
1989BAAS...21.1179S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A Rebound Shock Mechanism for Solar Fibrils
Authors: Sterling, Alphonse C.; Hollweg, Joseph V.
1989ApJ...343..985S    Altcode:
  Flows along a rigid solar magnetic flux tube which is horizontal over
  a substantial portion of its length are numerically investigated. A
  single, quasi-impulsive force near the base of the first vertical
  segment drives a series of upward propagating rebound shocks on the
  flux tube. When the horizontal segment is in the corona, the shocks
  raise the transition region onto the horizontal segment and eventually
  onto the coronal vertical segment. The material behind the displaced
  transition region resembles a fibril on the horizontal segment, and a
  short spicule on the second vertical segment. A full-sized spicule does
  not develop. The resulting density of the material on the horizontal
  segment is 10 to the -14th g/cu cm, which is consistent with the
  observed densities in fibrils. When the horizontal segment is in the
  chromosphere, the motions and densities induced on the horizontal
  segment do not resemble those of observed fibrils, and a full-sized
  spicule again does not develop.

---------------------------------------------------------
Title: Numerical Simulations of the Rebound Shock Model for Spicules
Authors: Sterling, A. C.; Mariska, J. T.
1988BAAS...20Q.989S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Rebound Shock Model for Solar Spicules: Dynamics at
    Long Times
Authors: Sterling, Alphonse C.; Hollweg, Joseph V.
1988ApJ...327..950S    Altcode:
  The spicule model due to Hollweg is extended and developed. The
  dynamics is emphasized here; radiative and ionization losses, heat
  conduction, and nonshock heat input, are not included. In the model,
  a series of rebound shocks results in chromospheric material with
  spicule-like properties below a raised transition region. The shocks
  result from a single quasi-impulsive source in the photosphere. It
  is found that at long times, the model approaches a new hydrostatic
  equilibrium with the transition region remaining raised, and with a
  region of shock-heated chromosphere below it. Attention is given to
  the variation of the properties of the model in response to different
  values for the magnitude and location of the source, and to different
  initial transition region heights. It is concluded that the model
  is capable of generating structures with properties consistent with
  observations of spicules (with the exception of temperature) when only
  the dynamics is considered.

---------------------------------------------------------
Title: A Rebound Shock Model for Solar Fibrils
Authors: Sterling, A. C.; Hollweg, J. V.
1988BAAS...20..690S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Dynamics of the Solar Atmosphere: Spicules and Fibrils.
Authors: Sterling, Alphonse Christopher
1988PhDT.........2S    Altcode:
  Numerical and analytical studies of MHD waves on magnetic flux tubes are
  applied to problems of the solar atmosphere. In particular, theoretical
  analysis of the chromospheric features known as spicules and fibrils
  are undertaken. The thesis consists of three principal segments:. i. A
  preexisting spicule model is extended and developed. In the model, a
  series of rebound shocks propagating on a vertical magnetic flux tube
  results in chromospheric material with spicule-like properties below a
  raised transition region. The model emphasizes dynamic motions and shock
  heating, but excludes radiative and ionization losses. At long times,
  the model approaches a new hydrostatic equilibrium with the transition
  region remaining raised, and with a region of shock-heated chromosphere
  below it. The variation of the model properties in response to different
  initial parameters is investigated. One conclusion is that the model
  is capable of generating structures with properties consistent with
  observations of spicules (with the exception of temperature) when
  only the dynamics is considered. ii. An analytical study is performed
  using linearized MHD equations to demonstrate that spicules may act as
  resonance cavities for MHD Alfven waves propagating along a vertical
  magnetic flux tube. When the resonances are excited, large amounts of
  wave energy from the photosphere and lower chromosphere can propagate
  into the spicule. This may result in the observed heating, fading,
  and twisting motions of spicules. It is assumed that the wave energy
  can be dissipated as heat via a turbulent cascade which follows
  a Kolmogorov. iii. The spicule model used in the first segment of
  the thesis is applied to a magnetic field geometry which is vertical
  through the photosphere and chromosphere, turns horizontal in the low
  corona, and eventually turns vertical again and extends into the outer
  corona. Radiative and ionization losses are again omitted. A structure
  develops on the horizontal segment which may be identifiable with a
  fibril, but a full spicule does not develop. At long times, the fibril
  and short spicule remain extended, and a standing wave develops on
  the flux tube.

---------------------------------------------------------
Title: Spicule Dynamics: Long Time Behavior
Authors: Sterling, A. C.; Hollweg, J. V.
1985BAAS...17Q.631S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Alfvenic resonances on solar spicules
Authors: Sterling, A. C.; Hollweg, J. V.
1984ApJ...285..843S    Altcode:
  It is suggested that twisting and heating of solar spicules can
  be produced by Alfven waves which enter the spicule from below. The
  spicule is treated as a region of constant Alfven speed which is bounded
  above by a region of much higher Alfven speed (the corona) and below
  by a region of exponentially increasing Alfven speed (the photosphere
  and chromosphere). It is shown how the spicule can act as a resonant
  cavity. The transmission of the waves into the cavity is analytically
  determined to be enhanced at certain resonant frequencies. With
  reasonable spicule parameters, and assuming the spicule damping to be
  moderately large, it is found that twisting velocities of approximately
  20-30 km/s can be induced on the spicule. It is suggested that the
  Alfven waves are dissipated via a turbulent cascade of their energy to
  higher wavenumbers. It is shown that the waves can thereby heat the
  spicules to the observed temperatures. It is further suggested that
  the continued input of energy can explain why H-alpha spicules fade,
  since the predicted heating rate is sufficient to heat the spicules
  to temperatures at which the hydrogen is fully ionized; thus H-alpha
  spicules may evolve into EUV spicules.

---------------------------------------------------------
Title: Resonant heating - an interpretation of coronal loop data
Authors: Hollweg, J. V.; Sterling, A. C.
1984ApJ...282L..31H    Altcode:
  The authors show that the resonant heating theory of Hollweg can be
  used to organize the coronal loop data of Golub et al. When combined
  with a reasonable form for the input power spectrum, the resonant
  heating theory is fully compatible with the loop data.

---------------------------------------------------------
Title: Coronal Loop Heating: Theory and Data
Authors: Hollweg, J. V.; Sterling, A. C.
1984BAAS...16..527H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Alfvenic Heating: An Interpretation of Coronal Loop Data
Authors: Sterling, A. C.; Hollweg, J. V.
1984BAAS...16Q.527S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Resonances of Solar Spicules
Authors: Hollweg, J. V.; Sterling, A. C.
1983BAAS...15R.994H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Study of Earth Tides, Earthquakes and Terrestrial Spectroscopy
    by Analysis of the Level Fluctuations in a Borehole at Heibaart
    (Belgium)
Authors: Sterling, A.; Smets, E.
1971GeoJ...23..225S    Altcode: 1971GeoJI..23..225S
  No abstract at ADS

---------------------------------------------------------
Title: Etude des marées terrestres et des séismes par l'analyse
    des variations du niveau d'eau dans un puits à Heibaart
Authors: Sterling, A.; Smets, E.
1970C&T....86...23S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Effets de dilatations cubiques dues aux marées terrestres
    observés sous forme de variations de niveau dans un puits à
    Basècles (Hainaut)
Authors: Melchior, P.; Sterling, A.; Wery, A.
1963C&T....79..353M    Altcode:
  No abstract at ADS