explanation      blue bibcodes open ADS page with paths to full text
Author name code: panesar
ADS astronomy entries on 2022-09-14
author:"Panesar, Navdeep Kaur" 

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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: The Magnetic Origin of Solar Campfires: Observations by Solar
    Orbiter and SDO
Authors: Panesar, Navdeep Kaur; Zhukov, Andrei; Berghmans, David;
   Auchere, Frederic; Müller, Daniel; Tiwari, Sanjiv Kumar; Cheung, Mark
2022cosp...44.2564P    Altcode:
  Solar campfires are small-scale, short-lived coronal brightenings,
  recently observed in 174 Å images by Extreme Ultraviolet Imager (EUI)
  on board Solar Orbiter (SolO). Here we investigate the magnetic origin
  of 52 campfires, in quiet-Sun, using line-of-sight magnetograms from
  Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager
  (HMI) together with extreme ultraviolet images from SolO /EUI and
  SDO/Atmospheric Imaging Assembly (AIA). We find that the campfires
  are rooted at the edges of photospheric magnetic network lanes; (ii)
  most of the campfires reside above neutral lines and 77% of them appear
  at sites of magnetic flux cancelation between the majority-polarity
  magnetic flux patch and a merging minority-polarity flux patch, with
  a flux cancelation rate of ∼1018 Mx hr‑1; some of the smallest
  campfires come from the sites where magnetic flux elements were barely
  discernible in HMI; (iii) some of the campfires occur repeatedly
  from the same neutral line; (iv) in the large majority of instances
  (79%), campfires are preceded by a cool-plasma structure, analogous to
  minifilaments in coronal jets; and (v) although many campfires have
  "complex" structure, most campfires resemble small-scale jets, dots,
  or loops. Thus, "campfire" is a general term that includes different
  types of small-scale solar dynamic features. They contain sufficient
  magnetic energy (∼1026-1027 erg) to heat the solar atmosphere
  locally to 0.5-2.5 MK. Their lifetimes range from about 1 minute to
  over 1 hour, with most of the campfires having a lifetime of <10
  minutes. The average lengths and widths of the campfires are 5400 ±
  2500 km and 1600 ± 640 km, respectively. Our observations suggest that
  (a) the presence of magnetic flux ropes may be ubiquitous in the solar
  atmosphere and not limited to coronal jets and larger-scale eruptions
  that make CMEs, and (b) magnetic flux cancelation, most likely driven
  by magnetic reconnection in the lower atmosphere, is the fundamental
  process for the formation and triggering of most campfires.

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Title: Fine-scale, Dot-like, Brightenings in an Emerging Flux Region:
    SolO/EUI Observations, and Bifrost MHD Simulations
Authors: Tiwari, Sanjiv Kumar; Berghmans, David; De Pontieu, Bart;
   Hansteen, Viggo; Panesar, Navdeep Kaur
2022cosp...44.2529T    Altcode:
  Numerous tiny bright dots are observed in SolO's EUI/\hri\ data
  of an emerging flux region (a coronal bright point) in 174 \AA,
  emitted by the coronal plasma at $\sim$1 MK. These dots are roundish,
  with a diameter of 675$\pm$300 km, a lifetime of 50$\pm$35 seconds,
  and an intensity enhancement of 30% $\pm$10% from their immediate
  surroundings. About half of the dots remain isolated during their
  evolution and move randomly and slowly ($<$10 \kms). The other half
  show extensions, appearing as a small loop or surge/jet, with intensity
  propagations below 30\,\kms. Some dots form at the end of a fine-scale
  explosion. Many of the bigger and brighter EUI/HRI dots are discernible
  in SDO/AIA 171 \AA\ channel, have significant EM in the temperature
  range of 1--2 MK, and are often located at polarity inversion lines
  observed in HMI LOS magnetograms. Bifrost MHD simulations of an emerging
  flux region do show dots in synthetic Fe IX/X images, although dots
  in simulations are not as pervasive as in observations. The dots
  in simulations show distinct Doppler signatures -- blueshifts and
  redshifts coexist, or a redshift of the order of 10 \kms\ is followed
  by a blueshift of similar or higher magnitude. The synthetic images of
  O V/VI and Si IV lines, which form in the transition region, also show
  the dots that are observed in Fe IX/X images, often expanded in size,
  or extended as a loop, and always with stronger Doppler velocities (up
  to 100 \kms) than that in Fe IX/X lines. Our results, together with the
  field geometry of dots in the simulations, suggest that most dots in
  emerging flux regions form in the lower solar atmosphere (at $\approx$1
  Mm) by magnetic reconnection between emerging and pre-existing/emerged
  magnetic field. The dots are smaller in Fe IX/X images (than in O V/VI
  & Si IV lines) most likely because only the hottest counterpart of
  the magnetic reconnection events is visible in the hotter emission. Some
  dots might be manifestations of magneto-acoustic shocks (from the
  lower atmosphere) through the line formation region of Fe IX/X. A
  small number of dots could also be a response of supersonic downflows
  impacting transition-region/chromospheric density.

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Title: Observations of magnetic reconnection and particle acceleration
    locations in solar coronal jets
Authors: Zhang, Yixian; Musset, Sophie; Glesener, Lindsay; Panesar,
   Navdeep; Fleishman, Gregory
2022arXiv220705668Z    Altcode:
  We present a multi-wavelength analysis of two flare-related jets
  on November 13, 2014, using data from SDO/AIA, RHESSI, Hinode/XRT,
  and IRIS. Unlike most coronal jets where hard X-ray (HXR) emissions
  are usually observed near the jet base, in these events HXR emissions
  are found at several locations, including in the corona. We carry out
  the first differential emission measure (DEM) analysis that combines
  both AIA (and XRT when available) bandpass filter data and RHESSI HXR
  measurements for coronal jets, and obtain self-consistent results
  across a wide temperature range and into non-thermal energies. In
  both events, hot plasma first appeared at the jet base, but as the
  base plasma gradually cooled, hot plasma also appeared near the jet
  top. Moreover, non-thermal electrons, while only mildly energetic,
  are found in multiple HXR locations and contain a large amount of
  total energy. Particularly, the energetic electrons that produced the
  HXR sources at the jet top were accelerated near the top location,
  rather than traveling from a reconnection site at the jet base. This
  means that there was more than one particle acceleration site in
  each event. Jet velocities are consistent with previous studies,
  including upward and downward velocities around ~200 km/s and ~100
  km/s respectively, and fast outflows of 400-700 km/s. We also examine
  the energy partition in the later event, and find that the non-thermal
  energy in accelerated electrons is most significant compared to other
  energy forms considered. We discuss the interpretations and provide
  constraints on mechanisms for coronal jet formation.

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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: SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots
in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation
Authors: Tiwari, Sanjiv K.; Hansteen, Viggo H.; De Pontieu, Bart;
   Panesar, Navdeep K.; Berghmans, David
2022ApJ...929..103T    Altcode: 2022arXiv220306161T
  We report on the presence of numerous tiny bright dots in and around
  an emerging flux region (an X-ray/coronal bright point) observed with
  SolO's EUI/HRI<SUB>EUV</SUB> in 174 Å. These dots are roundish and have
  a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity
  enhancement of 30% ± 10% above their immediate surroundings. About
  half of the dots remain isolated during their evolution and move
  randomly and slowly (&lt;10 km s<SUP>-1</SUP>). The other half show
  extensions, appearing as a small loop or surge/jet, with intensity
  propagations below 30 km s<SUP>-1</SUP>. Many of the bigger and brighter
  HRI<SUB>EUV</SUB> dots are discernible in the SDO/AIA 171 Å channel,
  have significant emissivity in the temperature range of 1-2 MK, and
  are often located at polarity inversion lines observed in SDO/HMI LOS
  magnetograms. Although not as pervasive as in observations, a Bifrost
  MHD simulation of an emerging flux region does show dots in synthetic
  Fe IX/X images. These dots in the simulation show distinct Doppler
  signatures-blueshifts and redshifts coexist, or a redshift of the
  order of 10 km s<SUP>-1</SUP> is followed by a blueshift of similar
  or higher magnitude. The synthetic images of O V/VI and Si IV lines,
  which represent transition region radiation, also show the dots that
  are observed in Fe IX/X images, often expanded in size, or extended
  as a loop, and always with stronger Doppler velocities (up to 100
  km s<SUP>-1</SUP>) than that in Fe IX/X lines. Our observation and
  simulation results, together with the field geometry of dots in the
  simulation, suggest that most dots in emerging flux regions form in the
  lower solar atmosphere (at ≍ 1 Mm) by magnetic reconnection between
  emerging and preexisting/emerged magnetic field. Some dots might be
  manifestations of magnetoacoustic shocks through the line formation
  region of Fe IX/X emission.

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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: Multi-wavelength Analysis of Two Flare-related RHESSI
    Coronal Jets
Authors: Zhang, Yixian; Musset, Sophie; Glesener, Lindsay; Panesar,
   Navdeep K.; Fleishman, Gregory
2021AGUFMSH25E2142Z    Altcode:
  Current models for solar coronal jets generally suggest that they are
  formed by magnetic reconnection between open and closed magnetic field
  lines, but details of triggering process for such magnetic reconnection
  are still not fully clear. Here we present multi-wavelength analysis
  of two flare-rated jets on November 13, 2014, using data from the
  Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory
  (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager
  (RHESSI). Usually, hot plasma in a coronal jet is located near
  the reconnection site or the base of the jet, as suggested by most
  models. However, for these two events, both the differential emission
  measure (DEM) analysis and RHESSI observations suggested that hot
  plasma appeared not only at the base of the jet at the beginning of
  each event, but also near the top of the jet a few minutes after the
  starting time. We performed the first comparison of the DEM in extreme
  ultraviolet (EUV) and the hard X-ray (HXR) spectrum for coronal jets,
  which qualitatively validated the hot component of the DEM. In one of
  the events, HXR emissions were observed at three different locations
  and different times: first at the base of the jet, then near the top
  of the jet, and finally at a location to the north of the jet. These
  HXR sources showed evidence of accelerated electrons which extended
  to fairly low energies. Jet velocities were consistent with previous
  studies, including major upward and downward velocities of 200km/s
  and 100km/s respectively, and fast outflows of 680km/s or 390km/s
  only visible in the 131A filter. Combining the temperature profile,
  the velocity profile, and the accelerated electron population for these
  two events, this work will provide new constraints on mechanisms for
  coronal jet formation.

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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: Characterizing Steady and Bursty Coronal Heating of a Solar
    Active Region
Authors: Wilkerson, Lucy; Tiwari, Sanjiv; Panesar, Navdeep K.;
   Moore, Ronald
2021AGUFMSH15E2060W    Altcode:
  One of the biggest problems in solar physics today is our inability
  to explain why the solar corona is so hot. In this project, we
  aimed to quantify transient and background coronal heating for a
  given active region in order to better understand coronal heating. We
  used SDO/AIA data of the active region NOAA 12712 observed on May 29,
  2018 over a period of 24 hours with a 3-minute cadence. We calculated
  FeXVIII emission (hot component of AIA 94 Å channel) by removing
  warm components using AIA 171 and 193 Å channels. From the maximum,
  minimum, and mean brightness values of each pixel over the full 24 hour
  period, we made maximum, minimum, and mean brightness maps. We repeated
  this process in moving time windows of 16 hours, 8 hours, 5 hours, 3
  hours, 1 hour, and 30 minutes. We used the total luminosity for each
  of these maps over time to make lightcurves that show the evolution
  of maximum, minimum, and mean brightness over time for each running
  window. Finally, we took the ratio of the total maximum and total
  minimum luminosity to total mean luminosity, and plotted these ratios
  over time. The average maximum to mean ratio was 8.40±0.00, 6.36±0.46,
  5.29±0.34, 4.73±0.24, 4.19±0.19, 3.21±0.17, and 2.64±0.15 and the
  average minimum to mean ratio was 0.053±0.00, 0.08±0.00, 0.12±0.01,
  0.14±0.02, 0.17±0.02, 0.26±0.02, and 0.33±0.03 for 24h, 16h, 8h,
  5h, 3h, 1h, and 30m windows, respectively. As expected, the ratio of
  background to mean luminosity increased as the time window decreased,
  and the ratio of transient to mean luminosity decreased as the time
  window decreased. As such, the ratio of background to mean luminosity
  is a new and effective technique to quantify the background intensity
  of the active region. Our 24h window result suggests that at most 5%
  of the luminosity of the AR at a given time comes from the steady
  background heating. This upper limit increases to 33% of the luminosity
  of the AR for the 30 min running window.

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Title: Solar Jet Hunter: a citizen science investigation of coronal
    solar jets
Authors: Musset, Sophie; Glesener, Lindsay; Fortson, Lucy; Kapsiak,
   Charles; Ostlund, Erik; Alnahari, Suhail; Jeunon, Mariana; Zhang,
   Yixian; Panesar, Navdeep; Fleishman, Gregory; Hurlburt, Neal
2021AGUFMSA32A..07M    Altcode:
  The Sun is the source of energetic particles that fill the heliosphere,
  interact with planets magnetospheres, and impact human activities. The
  origins of those energetic particles are still under investigation,
  as well as the mechanisms responsible for their escape from the solar
  atmosphere where they are energized. Solar jets, collimated ejections of
  solar plasma along magnetic field lines extending to the interplanetary
  medium, offer a possible route for particle escape. Coronal solar
  jets are commonly observed in soft X-rays and extreme ultraviolet
  (EUV) and are ubiquitous in the solar atmosphere, assuming various
  shapes, sizes and velocities. To date, autonomous algorithms are not
  detecting solar jets reliably, and they are usually reported manually
  by human observers, resulting in an incomplete and inhomogeneous
  database of jets. In order to produce a reliable, extensive, and
  consistent database of jets, that will be used to statistically study
  the jet phenomenon and its relationship to solar energetic particles,
  we initiated a citizen science project called Solar Jet Hunter whose
  goal is to explore the huge amount of EUV observations of the Sun in
  order to identify and characterize the solar jets in the dataset. The
  resulting database will also be used to train algorithms to identify
  solar jets in the EUV data. We will present here the preliminary
  results of this Zooniverse project.

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Title: Campfires observed by EUI: What have we learned so far?
Authors: Berghmans, David; Auchere, F.; Zhukov, Andrei; Mierla,
   Marilena; Chen, Yajie; Peter, Hardi; Panesar, Navdeep; Chitta, Lakshmi
   Pradeep; Antolin, Patrick; Aznar Cuadrado, Regina; Tian, Hui; Hou,
   Zhenyong; Podladchikova, Olena
2021AGUFMSH21A..02B    Altcode:
  Since its very first light images of the corona, the EUI/HRIEUV
  telescope onboard Solar Orbiter has observed small localised
  brightenings in the Quiet Sun. These small localised brightenings,
  have become known as campfires, and are observed with length scales
  between 400 km and 4000 km and durations between 10 sec and 200
  sec. The smallest and weakest of these HRIEUV brightenings have
  not been previously observed. Simultaneous observations from the
  EUI High-resolution Lyman- telescope (HRILYA) do not show localised
  brightening events, but the locations of the HRIEUV events clearly
  correspond to the chromospheric network. Comparisons with simultaneous
  AIA images shows that most events can also be identified in the
  17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although
  they appear weaker and blurred. Some of the larger campfires have
  the appearance of small interacting loops with the brightening
  expanding from the contact point of the loops. Our differential
  emission measure (DEM) analysis indicated coronal temperatures. We
  determined the height for a few of these campfires to be between 1
  and 5 Mm above the photosphere. We interpret these events as a new
  extension to the flare-microflare-nanoflare family. Given their low
  height, the EUI campfires could stand as a new element of the fine
  structure of the transition region-low corona, that is, as apexes
  of small-scale loops that undergo internal heating all the way up to
  coronal temperatures. 3D MHD simulations with the MURaM code revealed
  brightenings that are in many ways similar to the campfires by EUI. The
  brightenings in the simulations suggest that campfires are triggered by
  component reconnection inside flux bundles rather than flux emergence
  or cancellation. Nevertheless, some of the observed campfires can
  be clearly linked to flux cancellation events and, intriguingly,
  are preceded by an erupting cool plasma structure. Analysis of the
  dynamics of campfires revealed that some have the appearance of coronal
  microjets, the smallest coronal jets observed in the quiet Sun. The
  HRIEUV images also reveal transient jets on a somewhat bigger scale
  with repeated outflows on the order of 100 km s1. In this paper we
  will provide an overview of the campfire related phenomena that EUI
  has observed and discuss the possible relevance for coronal heating.

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Title: The Magnetic Origin of Solar Campfires
Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Berghmans, David;
   Cheung, Mark C. M.; Müller, Daniel; Auchere, Frederic; Zhukov, Andrei
2021ApJ...921L..20P    Altcode: 2021arXiv211006846P
  Solar campfires are fine-scale heating events, recently observed by
  Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Here we use EUI
  174 Å images, together with EUV images from Solar Dynamics Observatory
  (SDO)/Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms
  from SDO/Helioseismic and Magnetic Imager (HMI) to investigate the
  magnetic origin of 52 randomly selected campfires in the quiet solar
  corona. We find that (i) the campfires are rooted at the edges of
  photospheric magnetic network lanes; (ii) most of the campfires reside
  above the neutral line between majority-polarity magnetic flux patch and
  a merging minority-polarity flux patch, with a flux cancelation rate of
  ~10<SUP>18</SUP> Mx hr<SUP>-1</SUP>; (iii) some of the campfires occur
  repeatedly from the same neutral line; (iv) in the large majority of
  instances, campfires are preceded by a cool-plasma structure, analogous
  to minifilaments in coronal jets; and (v) although many campfires have
  "complex" structure, most campfires resemble small-scale jets, dots,
  or loops. Thus, "campfire" is a general term that includes different
  types of small-scale solar dynamic features. They contain sufficient
  magnetic energy (~10<SUP>26</SUP>-10<SUP>27</SUP> erg) to heat the solar
  atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1
  minute to over 1 hr, with most of the campfires having a lifetime of
  &lt;10 minutes. The average lengths and widths of the campfires are 5400
  ± 2500 km and 1600 ± 640 km, respectively. Our observations suggest
  that (a) the presence of magnetic flux ropes may be ubiquitous in the
  solar atmosphere and not limited to coronal jets and larger-scale
  eruptions that make CMEs, and (b) magnetic flux cancelation is the
  fundamental process for the formation and triggering of most campfires.

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Title: Multi-wavelength analysis of flare-related RHESSI coronal jets
Authors: Zhang, Y.; Musset, S.; Glesener, L.; Panesar, N.; Fleishman,
   G.
2021AAS...23821315Z    Altcode:
  Current models for solar coronal jets generally suggest that they
  are formed by magnetic reconnection between open and closed magnetic
  field lines, but details of the triggering process for such magnetic
  reconnection are still not fully clear. Here we report observations
  of a set of coronal jets on November 13 2014 using data from the
  Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the
  Atmospheric Imaging Assembly (AIA). Usually, hot plasma in a coronal
  jet is located near the reconnection site or the base of the jet, as
  suggested by most models. However, for the first and one of the later
  jets in this series, RHESSI found strong hard x-ray (HXR) emissions at
  the top of the jet, well-modeled by an isothermal distribution, which
  indicates the existence of hot material at the top. The differential
  emission measure (DEM) analysis with AIA data shows qualitatively
  consistent results with RHESSI observations, and we present a comparison
  between HXR flux deduced from AIA DEMs and HXR flux directly measured by
  RHESSI. To identify possible drivers for those jets, we calculate the
  jet speeds in multiple AIA filters and compare them with, for example,
  the upper limit of chromospheric evaporation. This work will provide
  new constraints on mechanisms for coronal jet formation.

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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.

---------------------------------------------------------
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.

---------------------------------------------------------
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.

---------------------------------------------------------
Title: What Percentage Of The Brightest Coronal Loops Are Rooted In
    Mixed-polarity Magnetic Flux?
Authors: Tiwari, S. K.; Evans, C. L.; Panesar, N.; Prasad, A.;
   Moore, R.
2021AAS...23820502T    Altcode:
  We have previously shown (Tiwari et al. 2017, ApJ Letters, 843,
  L20) that the heating in active region (AR) coronal loops depends
  systematically on their photospheric magnetic setting. There, we found
  that the brightest and hottest loops of ARs are the ones connecting
  sunspot umbra/penumbra at one end to (a) penumbra, (b) unipolar plage,
  or (c) mixed-polarity plage on the other end. The coolest loops are
  the ones that connect sunspot umbra at both ends. In this work we
  study the brightest loops during 24 hours in the core of the active
  region that was observed by Hi-C 2.1. These loops have neither foot in
  sunspot umbra or penumbra, but in plage. We investigate what percentage
  of the brightest coronal loops (in SDO/AIA Fe XVIII emission) have
  mixed-polarity magnetic flux at least at one of their feet, and so the
  heating could be driven by magnetic flux cancellation. We confirm the
  footpoint locations of loops via non-force-free field extrapolations
  (using SDO/HMI magnetograms) and find that ∼40% of the loops have
  both feet in unipolar flux, and ∼60% of the loops have at least one
  foot in mixed-polarity flux. The loops having mixed-polarity foot-point
  flux are ∼15% longer lived on average than the ones with both feet
  unipolar, but their peak-intensity averages do not show any significant
  difference. While the presence of mixed-polarity magnetic flux at least
  at one foot in majority of loops strongly supports the cancellation
  idea, the absence of mixed-polarity magnetic flux (to the detection
  limit of HMI) in about 40% of the loops suggests cancellation may not be
  necessary for heating coronal loops, but rather might enhance heating by
  some factor. We will further discuss some points that support, and some
  points that challenge, the flux cancellation idea of coronal heating.

---------------------------------------------------------
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.

---------------------------------------------------------
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.

---------------------------------------------------------
Title: Are the Brightest Coronal Loops Always Rooted in Mixed-polarity
    Magnetic Flux?
Authors: Tiwari, Sanjiv K.; Evans, Caroline L.; Panesar, Navdeep K.;
   Prasad, Avijeet; Moore, Ronald L.
2021ApJ...908..151T    Altcode: 2021arXiv210210146T
  A recent study demonstrated that freedom of convection and strength of
  magnetic field in the photospheric feet of active-region (AR) coronal
  loops, together, can engender or quench heating in them. Other studies
  stress that magnetic flux cancellation at the loop-feet potentially
  drives heating in loops. We follow 24 hr movies of a bipolar AR, using
  extreme ultraviolet images from the Atmospheric Imaging Assembly/Solar
  Dynamics Observatory (SDO) and line-of-sight (LOS) magnetograms from
  the Helioseismic and Magnetic Imager (HMI)/SDO, to examine magnetic
  polarities at the feet of 23 of the brightest coronal loops. We derived
  Fe XVIII emission (hot-94) images (using the Warren et al. method)
  to select the hottest/brightest loops, and confirm their footpoint
  locations via non-force-free field extrapolations. From 6″ × 6″
  boxes centered at each loop foot in LOS magnetograms we find that ∼40%
  of the loops have both feet in unipolar flux, and ∼60% of the loops
  have at least one foot in mixed-polarity flux. The loops with both feet
  unipolar are ∼15% shorter lived on average than the loops having
  mixed-polarity foot-point flux, but their peak-intensity averages
  are equal. The presence of mixed-polarity magnetic flux in at least
  one foot in the majority of the loops suggests that flux cancellation
  at the footpoints may drive most of the heating. But the absence of
  mixed-polarity magnetic flux (to the detection limit of HMI) in ∼40%
  of the loops suggests that flux cancellation may not be necessary to
  drive heating in coronal loops—magnetoconvection and field strength
  at both loop feet possibly drive much of the heating, even in the
  cases where a loop foot presents mixed-polarity magnetic flux.

---------------------------------------------------------
Title: Fine-scale explosive energy release at sites of magnetic
flux cancellation in the core of a solar active region: Hi-C 2.1,
    IRIS and SDO observations
Authors: Tiwari, Sanjiv Kumar; Moore, Ronald; De Pontieu, Bart;
   Winebarger, Amy; Panesar, Navdeep Kaur
2021cosp...43E1779T    Altcode:
  The second sounding-rocket flight of the High-Resolution Coronal Imager
  (Hi-C 2.1) provided unprecedentedly-high spatial and temporal resolution
  (~250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 A, of
  a solar active region (AR NOAA 12712) near solar disk center. Three
  morphologically-different types (I: dot-like, II: loop-like, &amp;
  III: surge/jet-like) of fine-scale sudden brightening events (tiny
  microflares) are seen within and at the ends of an arch filament system
  in the core of the AR. Although type Is resemble IRIS bombs (in size,
  and brightness with respect to surroundings), our dot-like events are
  apparently much hotter, and shorter in span (70 s). Because Dot-like
  brightenings are not as clearly discernible in AIA 171 A as in Hi-C 172
  A, they were not reported before. We complement the 5-minute-duration
  Hi-C 2.1 data with SDO/HMI magnetograms, SDO/AIA EUV and UV images,
  and IRIS UV spectra and slit-jaw images to examine, at the sites of
  these events, brightenings and flows in the transition region and corona
  and evolution of magnetic flux in the photosphere. Most, if not all,
  of the events are seated at sites of opposite-polarity magnetic flux
  convergence (sometimes driven by adjacent flux emergence), implying
  flux cancellation at the microflare's polarity inversion line. In the
  IRIS spectra and images, we find confirming evidence of field-aligned
  outflow from brightenings at the ends of loops of the arch filament
  system. In types I and II the explosion is confined, while in type
  III the explosion is ejective and drives jet-like outflow. The light
  curves from Hi-C, AIA and IRIS peak nearly simultaneously for many
  of these events and none of the events display a systematic cooling
  sequence as seen in typical coronal flares, suggesting that these tiny
  brightening events have chromospheric/transition-region origin.

---------------------------------------------------------
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: Citizen science to identify and analyze coronal jets in
    SDO/AIA data
Authors: Musset, S.; Glesener, L.; Fortson, L.; Wright, D.; Kapsiak,
   C.; Hurlburt, N. E.; Panesar, N. K.; Fleishman, G. D.
2020AGUFMSH0240006M    Altcode:
  Coronal jets are collimated ejections of plasma that are found to
  be ubiquitous in the solar atmosphere, at different scales and in
  different regions of the Sun. They are interpreted as the result of
  energy release in the solar atmosphere when magnetic reconnection
  involves both closed and open magnetic field lines. Jets are therefore
  suspected to be associated with the escape of energetic particles
  from the solar atmosphere and possibly with perturbations of the solar
  wind. The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic
  Observatory (SDO) provides high-cadence and high-resolution images
  of the solar atmosphere in which coronal jets can be identified and
  studied. However, the detection of such events via automatic algorithms
  has been limited and is better achieved by human annotation of the
  data. In order to detect and catalog coronal jets in the AIA data set,
  we designed a citizen science project on the Zooniverse platform, where
  participants can report the precise position and timing of solar jets,
  along with an indication of their extent. The use of citizen science
  provides the opportunity to perform this kind of analysis on a large
  amount of data, and to derive the average values of the jet properties
  reported by multiple volunteers, removing some of the bias inherent in
  a single expert observer reporting such properties. This catalog of jet
  events will provide a useful database for future jet studies, including
  statistical studies, and a training set for a machine learning approach
  to the problem of the detection of coronal jets in EUV data sets.

---------------------------------------------------------
Title: Fine-scale explosive energy release at sites of magnetic
flux cancellation in the core of a solar active region: Hi-C 2.1,
    IRIS and SDO observations
Authors: Tiwari, S. K.; Panesar, N. K.; Moore, R. L.; De Pontieu,
   B.; Winebarger, A. R.
2020AGUFMSH0010007T    Altcode:
  The second sounding-rocket flight of the High-Resolution Coronal Imager
  (Hi-C 2.1) provided unprecedentedly-high spatial and temporal resolution
  (~250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 Å, of
  a solar active region (AR NOAA 12712) near solar disk center. Three
  morphologically-different types (I: dot-like, II: loop-like, &amp;
  III: surge/jet-like) of fine-scale sudden brightening events (tiny
  microflares) are seen within and at the ends of an arch filament system
  in the core of the AR. Although type Is resemble IRIS bombs (in size,
  and brightness with respect to surroundings), our dot-like events are
  apparently much hotter, and shorter in span (70 s). Because Dot-like
  brightenings are not as clearly discernible in AIA 171 Å as in Hi-C 172
  Å, they were not reported before. We complement the 5-minute-duration
  Hi-C 2.1 data with SDO/HMI magnetograms, SDO/AIA EUV and UV images,
  and IRIS UV spectra and slit-jaw images to examine, at the sites of
  these events, brightenings and flows in the transition region and corona
  and evolution of magnetic flux in the photosphere. Most, if not all,
  of the events are seated at sites of opposite-polarity magnetic flux
  convergence (sometimes driven by adjacent flux emergence), implying
  flux cancellation at the microflare's polarity inversion line. In the
  IRIS spectra and images, we find confirming evidence of field-aligned
  outflow from brightenings at the ends of loops of the arch filament
  system. In types I and II the explosion is confined, while in type
  III the explosion is ejective and drives jet-like outflow. The light
  curves from Hi-C, AIA and IRIS peak nearly simultaneously for many
  of these events and none of the events display a systematic cooling
  sequence as seen in typical coronal flares, suggesting that these tiny
  brightening events have chromospheric/transition-region origin.

---------------------------------------------------------
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: 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: 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: A Solar Magnetic-fan Flaring Arch Heated by Nonthermal
    Particles and Hot Plasma from an X-Ray Jet Eruption
Authors: Lee, Kyoung-Sun; Hara, Hirohisa; Watanabe, Kyoko; Joshi,
   Anand D.; Brooks, David H.; Imada, Shinsuke; Prasad, Avijeet; Dang,
   Phillip; Shimizu, Toshifumi; Savage, Sabrina L.; Moore, Ronald;
   Panesar, Navdeep K.; Reep, Jeffrey W.
2020ApJ...895...42L    Altcode: 2020arXiv200509875L
  We have investigated an M1.3 limb flare, which develops as a magnetic
  loop/arch that fans out from an X-ray jet. Using Hinode/EIS, we
  found that the temperature increases with height to a value of over
  10<SUP>7</SUP> K at the loop top during the flare. The measured Doppler
  velocity (redshifts of 100-500 km s<SUP>-1</SUP>) and the nonthermal
  velocity (≥100 km s<SUP>-1</SUP>) from Fe XXIV also increase with
  loop height. The electron density increases from 0.3 × 10<SUP>9</SUP>
  cm<SUP>-3</SUP> early in the flare rise to 1.3 × 10<SUP>9</SUP>
  cm<SUP>-3</SUP> after the flare peak. The 3D structure of the loop
  derived with Solar TErrestrial RElations Observatory/EUV Imager
  indicates that the strong redshift in the loop-top region is due to
  upflowing plasma originating from the jet. Both hard X-ray and soft
  X-ray emission from the Reuven Ramaty High Energy Solar Spectroscopic
  Imager were only seen as footpoint brightenings during the impulsive
  phase of the flare, then, soft X-ray emission moved to the loop top in
  the decay phase. Based on the temperature and density measurements and
  theoretical cooling models, the temperature evolution of the flare arch
  is consistent with impulsive heating during the jet eruption followed
  by conductive cooling via evaporation and minor prolonged heating in
  the top of the fan loop. Investigating the magnetic field topology and
  squashing factor map from Solar Dynamics Observatory/HMI, we conclude
  that the observed magnetic-fan flaring arch is mostly heated from low
  atmospheric reconnection accompanying the jet ejection, instead of from
  reconnection above the arch as expected in the standard flare model.

---------------------------------------------------------
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: A CME-Producing Solar Eruption from the Interior of a Twisted
    Emerging Bipole
Authors: Moore, R. L.; Adams, M.; Panesar, N. K.; Falconer, D. A.;
   Tiwari, S. K.
2019AGUFMSH43D3355M    Altcode:
  In a negative-polarity coronal hole, magnetic flux emergence, seen by
  the Solar Dynamics Observatory's (SDO) Helioseismic Magnetic Imager
  (HMI), begins at approximately 19:00 UT on March 3, 2016. The emerged
  magnetic field produced sunspots with penumbrae by 3:00 UT on March
  4, which NOAA numbered 12514. The emerging magnetic field is largely
  bipolar with the opposite-polarity fluxes spreading apart overall,
  but there is simultaneously some convergence and cancellation of
  opposite-polarity flux at the polarity inversion line (PIL) inside the
  emerging bipole. The emerging bipole shows obvious overall left-handed
  shear and/or twist in its magnetic field and corresponding clockwise
  rotation of the two poles of the bipole about each other as the bipole
  emerges. The eruption comes from inside the emerging bipole and blows
  it open to produce a CME observed by SOHO/LASCO. That eruption is
  preceded by flux cancellation at the emerging bipole's interior PIL,
  cancellation that plausibly builds a sheared and twisted flux rope
  above the interior PIL and finally triggers the blow-out eruption of
  the flux rope via photospheric-convection-driven slow tether-cutting
  reconnection of the legs of the sheared core field, low above the
  interior PIL, as proposed by van Ballegooijen and Martens (1989, ApJ,
  343, 971) and Moore and Roumeliotis (1992, in Eruptive Solar Flares,
  ed. Z. Svestka, B.V. Jackson, and M.E. Machado [Berlin:Springer],
  69). The production of this eruption is a (perhaps rare) counterexample
  to solar eruptions that result from external collisional shearing
  between opposite polarities from two distinct emerging and/or emerged
  bipoles (Chintzoglou et al., 2019, ApJ, 871:67).

---------------------------------------------------------
Title: Are the brightest coronal loops always rooted in mixed-polarity
    magnetic flux?
Authors: Evans, C.; Tiwari, S. K.; Panesar, N. K.; Prasad, A.; Moore,
   R. L.
2019AGUFMSH41F3324E    Altcode:
  Magnetic energy dissipated in coronal loops heats the Sun's corona
  to millions of Kelvin. Some recent investigations indicate that in
  addition to the required magnetoconvection and field strength, heating
  in the brightest coronal loops are driven by flux cancellation at
  the loop-feet. To find coronal loop footpoints , we selected extreme
  ultraviolet (EUV) data from the Atmospheric Imaging Assembly (AIA)
  and line- of-sight (LOS) magnetograms from the Helioseismic and
  Magnetic Imager (HMI), both on-board the Solar Dynamics Observatory
  (SDO). We located the footpoints of 28 brightest coronal loops of
  the bipolar active region NOAA 12712 on 28 May 2018 in hot 94 images
  (calculated using the Warren et al. method) and confirm the location
  of these footpoints via non-force free field extrapolations. We examine
  the photospheric magnetic field in 6" boxes centered at each footpoint
  and find that ~20% of loops have both feet in unipolar magnetic flux,
  ~10% loops have both feet in mixed-polarity flux, and ~70% of loops
  have one foot in unipolar and one in mixed-polarity flux. The presence
  of mixed-polarity magnetic flux in at least one foot of majority
  of the brightest coronal loops suggests that flux cancellation at
  the footpoints may drive heating in them. However, the absence of
  mixed-polarity magnetic flux (to the detection limit of HMI) in a
  significant number of the brightest coronal loops suggests that flux
  cancellation may not be necessary to drive heating in the loops - the
  combination of magnetoconvection and the magnetic field strength at the
  footpoints could be responsible for much of the coronal loop heating
  even in cases where a footpoint presents mixed-polarity magnetic flux.

---------------------------------------------------------
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: Fine-scale explosive energy release at sites of magnetic flux
    cancellation in the core of the solar active region observed by Hi-C
    2.1, IRIS and SDO
Authors: Tiwari, S. K.; Panesar, N. K.; Moore, R. L.; De Pontieu,
   B.; Winebarger, A. R.
2019AGUFMSH31C3323T    Altcode:
  The second sounding-rocket flight of the High-Resolution Coronal Imager
  (Hi-C 2.1) provided unprecedentedly-high spatial and temporal resolution

---------------------------------------------------------
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: Fine-scale Explosive Energy Release at Sites of Prospective
    Magnetic Flux Cancellation in the Core of the Solar Active Region
    Observed by Hi-C 2.1, IRIS, and SDO
Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.;
   De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
   Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.;
   Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton,
   Richard J.; Peter, Hardi; Walsh, Robert W.
2019ApJ...887...56T    Altcode: 2019arXiv191101424T
  The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial
  and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X
  emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56
  UT. Three morphologically different types (I: dot-like; II: loop-like;
  III: surge/jet-like) of fine-scale sudden-brightening events (tiny
  microflares) are seen within and at the ends of an arch filament system
  in the core of the AR. Although type Is (not reported before) resemble
  IRIS bombs (in size, and brightness with respect to surroundings),
  our dot-like events are apparently much hotter and shorter in span
  (70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI
  magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw
  images to examine, at the sites of these events, brightenings and
  flows in the transition region and corona and evolution of magnetic
  flux in the photosphere. Most, if not all, of the events are seated
  at sites of opposite-polarity magnetic flux convergence (sometimes
  driven by adjacent flux emergence), implying likely flux cancellation
  at the microflare’s polarity inversion line. In the IRIS spectra
  and images, we find confirming evidence of field-aligned outflow from
  brightenings at the ends of loops of the arch filament system. In types
  I and II the explosion is confined, while in type III the explosion
  is ejective and drives jet-like outflow. The light curves from Hi-C,
  AIA, and IRIS peak nearly simultaneously for many of these events,
  and none of the events display a systematic cooling sequence as seen in
  typical coronal flares, suggesting that these tiny brightening events
  have chromospheric/transition region origin.

---------------------------------------------------------
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: Fine-scale explosive energy release at sites of magnetic
    flux cancellation in the core of the solar active region observed
    by HiC2.1, IRIS and SDO
Authors: Tiwari, Sanjiv K.; Panesar, Navdeep; Moore, Ronald L.;
   De Pontieu, Bart; Testa, Paola; Winebarger, Amy R.
2019AAS...23411702T    Altcode:
  The second sounding-rocket flight of the High-Resolution Coronal Imager
  (HiC2.1) provided unprecedentedly-high spatial and temporal resolution
  (150 km, 4.5 s) coronal EUV images of Fe IX/X emission at 172 Å, of
  a solar active region (AR NOAA 12712) near solar disk center. Three
  morphologically-different types (I: dot-like, II: loop-like, &amp;
  III: surge/jet-like) of fine-scale sudden brightening events (tiny
  microflares) are seen within and at the ends of an arch filament
  system in the core of the AR. We complement the 5-minute-duration
  HiC2.1 data with SDO/HMI magnetograms, SDO/AIA EUV and UV images, and
  IRIS UV spectra and slit-jaw images to examine, at the sites of these
  events, brightenings and flows in the transition region and corona
  and evolution of magnetic flux in the photosphere. Most, if not all,
  of the events are seated at sites of opposite-polarity magnetic flux
  convergence (sometimes driven by adjacent flux emergence), implying
  flux cancellation at the polarity inversion line. In the IRIS spectra
  and images, we find confirming evidence of field-aligned outflow from
  brightenings at the ends of loops of the arch filament system. These
  outflows from both ends of the arch filament system are seen as
  bi-directional flows in the arch filament system, suggesting that the
  well-known counter-streaming flows in large classical filaments could be
  driven in the same way as in this arch filament system: by fine-scale
  jet-like explosions from fine-scale sites of mixed-polarity field in
  the feet of the sheared field that threads the filament. Plausibly,
  the flux cancellation at these sites prepares and triggers a fine scale
  core-magnetic-field structure (a small sheared/twisted core field or
  flux rope along and above the cancellation line) to explode. In types
  I &amp; II the explosion is confined, while in type III the explosion
  is ejective and drives jet-like outflow in the manner of larger jets
  in coronal holes, quiet regions, and active regions.

---------------------------------------------------------
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: Invisibility of Solar Active Region Umbra-to-Umbra Coronal
Loops: New Evidence that Magnetoconvection Drives Solar-Stellar
    Coronal Heating
Authors: Moore, Ronald L.; Tiwari, Sanjiv; Thalmann, Julia; Panesar,
   Navdeep; Winebarger, Amy
2019AAS...23410603M    Altcode:
  How magnetic energy is injected and released in the solar corona,
  keeping it heated to several million degrees, remains elusive. The
  corona is shaped by the magnetic field that fills it and the heating
  of the corona generally increases with increasing strength of the
  field. For each of two bipolar solar active regions having one or
  more sunspots in each of the two main opposite-polarity domains of
  magnetic flux, from comparison of a nonlinear force-free model of the
  active region's three-dimensional coronal magnetic field to observed
  extreme-ultraviolet coronal loops, we find that (1) umbra-to-umbra
  loops, despite being rooted in the strongest magnetic flux at both ends,
  are invisible, and (2) the brightest loops have one foot in a sunspot
  umbra or penumbra and the other foot in another sunspot's penumbra or
  in unipolar or mixed-polarity plage. The invisibility of umbra-to-umbra
  loops is new evidence that magnetoconvetion drives solar-stellar coronal
  heating: evidently, the strong umbral field at both ends quenches the
  magnetoconvection and hence the heating. Broadly, our results indicate
  that depending on the field strength in both feet, the photospheric feet
  of a coronal loop on any convective star can either engender or quench
  coronal heating in the body of the loop. <P />This work was supported
  by funding from the Heliophysics Division of NASA's Science Mission
  Directorate, from NASA's Postdoctoral Program, and from the Austrian
  Science Fund. The results have been published in The Astrophysical
  Journal Letters (Tiwari, S. K., Thalmann, J. K., Panesar, N. K., Moore,
  R. L., &amp; Winebarger, A. R. 2017, ApJ Letters, 843:L20).

---------------------------------------------------------
Title: A CME-Producing Solar Eruption from the Interior of an Emerging
    Bipolar Active Region
Authors: Adams, Mitzi L.; Moore, Ronald L.; Panesar, Navdeep;
   Falconer, David
2019AAS...23430501A    Altcode:
  In a negative-polarity coronal hole, magnetic flux emergence, seen
  by the Solar Dynamics Observatory's (SDO) Helioseismic Magnetic
  Imager (HMI), begins at approximately 19:00 UT on March 3, 2016. The
  emerged magnetic field produced sunspots, which NOAA numbered 12514
  two days later. The emerging magnetic field is largely bipolar with
  the opposite-polarity fluxes spreading apart overall, but there is
  simultaneously some convergence and cancellation of opposite-polarity
  flux at the polarity inversion line (PIL) inside the emerging bipole. In
  the first fifteen hours after emergence onset, three obvious eruptions
  occur, observed in the coronal EUV images from SDO's Atmospheric
  Imaging Assembly (AIA). The first two erupt from separate segments
  of the external PIL between the emerging positve-polarity flux and
  the extant surrounding negative-polarity flux, with the exploding
  magnetic field being prepared and triggered by flux cancellation at the
  external PIL. The emerging bipole shows obvious overall left-handed
  shear and/or twist in its magnetic field. The third and largest
  eruption comes from inside the emerging bipole and blows it open to
  produce a CME observed by SOHO/LASCO. That eruption is preceded by flux
  cancellation at the emerging bipole's interior PIL, cancellation that
  plausibly builds a sheared and twisted flux rope above the interior
  PIL and finally triggers the blow-out eruption of the flux rope via
  photospheric-convection-driven slow tether-cutting reconnection of
  the legs of the sheared core field, low above the interior PIL, as
  proposed by van Ballegooijen and Martens (1989, ApJ, 343, 971) and
  Moore and Roumeliotis (1992, in Eruptive Solar Flares, ed. Z. Svestka,
  B.V. Jackson, and M.E. Machado [Berlin:Springer], 69). The production of
  this eruption is a (perhaps rare) counterexample to solar eruptions that
  result from external collisional shearing between opposite polarities
  from two distinct emerging and/or emerged bipoles (Chintzoglou et al.,
  2019, ApJ, 871:67). <P />This work was supported by NASA, the NASA
  Postdoctoral Program (NPP), and NSF.

---------------------------------------------------------
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: 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: Critical Magnetic Field Strengths for Solar Coronal Plumes
    in Quiet Regions and Coronal Holes?
Authors: Avallone, Ellis A.; Tiwari, Sanjiv K.; Panesar, Navdeep K.;
   Moore, Ronald L.; Winebarger, Amy
2018ApJ...861..111A    Altcode: 2018arXiv180511188A
  Coronal plumes are bright magnetic funnels found in quiet regions (QRs)
  and coronal holes (CHs). They extend high into the solar corona and last
  from hours to days. The heating processes of plumes involve dynamics
  of the magnetic field at their base, but the processes themselves
  remain mysterious. Recent observations suggest that plume heating is
  a consequence of magnetic flux cancellation and/or convergence at
  the plume base. These studies suggest that the base flux in plumes
  is of mixed polarity, either obvious or hidden in Solar Dynamics
  Observatory (SDO)/HMI data, but do not quantify it. To investigate the
  magnetic origins of plume heating, we select 10 unipolar network flux
  concentrations, four in CHs, four in QRs, and two that do not form a
  plume, and track plume luminosity in SDO/AIA 171 Å images along with
  the base flux in SDO/HMI magnetograms, over each flux concentration’s
  lifetime. We find that plume heating is triggered when convergence of
  the base flux surpasses a field strength of ∼200-600 G. The luminosity
  of both QR and CH plumes respond similarly to the field in the plume
  base, suggesting that the two have a common formation mechanism. Our
  examples of non-plume-forming flux concentrations, reaching field
  strengths of 200 G for a similar number of pixels as for a couple of our
  plumes, suggest that a critical field might be necessary to form a plume
  but is not sufficient for it, thus advocating for other mechanisms,
  e.g., flux cancellation due to hidden opposite-polarity field, at play.

---------------------------------------------------------
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: 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: Birth of a Bipolar Active Region in a Small Solar Coronal Hole
Authors: Adams, Mitzi; Panesar, Navdeep Kaur; Moore, Ronald L.
2018tess.conf20235A    Altcode:
  We report on an the emergence of an anemone active region in a very
  small

---------------------------------------------------------
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: Critical Magnetic Field Strengths for Unipolar Solar Coronal
    Plumes in Quiet Regions and Coronal Holes?
Authors: Avallone, E. A.; Tiwari, S. K.; Panesar, N. K.; Moore, R. L.
2017AGUFMSH43A2797A    Altcode:
  Coronal plumes are sporadic fountain-like structures that are bright
  in coronal emission. Each is a magnetic funnel rooted in a strong
  patch of dominant-polarity photospheric magnetic flux surrounded by
  a predominantly-unipolar magnetic network, either in a quiet region
  or a coronal hole. The heating processes that make plumes bright
  evidently involve the magnetic field in the base of the plume, but
  remain mysterious. Raouafi et al. (2014) inferred from observations
  that plume heating is a consequence of magnetic reconnection in the
  base, whereas Wang et al. (2016) showed that plume heating turns
  on/off from convection-driven convergence/divergence of the base
  flux. While both papers suggest that the base magnetic flux in their
  plumes is of mixed polarity, these papers provide no measurements
  of the abundance and strength of the evolving base flux or consider
  whether a critical magnetic field strength is required for a plume to
  become noticeably bright. To address plume production and evolution,
  we track the plume luminosity and the abundance and strength of the
  base magnetic flux over the lifetimes of six coronal plumes, using
  Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 171
  Å images and SDO/Helioseismic and Magnetic Imager (HMI) line-of-sight
  magnetograms. Three of these plumes are in coronal holes, three are in
  quiet regions, and each plume exhibits a unipolar base flux. We track
  the base magnetic flux over each plume's lifetime to affirm that its
  convergence and divergence respectively coincide with the appearance
  and disappearance of the plume in 171 Å images. We tentatively find
  that plume formation requires enough convergence of the base flux to
  surpass a field strength of ∼300-500 Gauss, and that quiet Sun and
  coronal-hole plumes both exhibit the same behavior in the response of
  their luminosity in 171 Å to the strength of the magnetic field in
  the base.

---------------------------------------------------------
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: Invisibility of Solar Active Region Umbra-to-Umbra Coronal
Loops: New Evidence that Magnetoconvection Drives Solar-Stellar
    Coronal Heating
Authors: Tiwari, S. K.; Thalmann, J. K.; Panesar, N. K.; Moore, R. L.;
   Winebarger, A. R.
2017AGUFMSH43A2789T    Altcode:
  Coronal heating generally increases with increasing magnetic field
  strength: the EUV/X-ray corona in active regions is 10-100 times more
  luminous and 2-4 times hotter than that in quiet regions and coronal
  holes, which are heated to only about 1.5 MK, and have fields that are
  10-100 times weaker than that in active regions. From a comparison of
  a nonlinear force-free model of the three-dimensional active region
  coronal field to observed extreme-ultraviolet loops, we find that (1)
  umbra-to-umbra coronal loops, despite being rooted in the strongest
  magnetic flux, are invisible, and (2) the brightest loops have one
  foot in an umbra or penumbra and the other foot in another sunspot's
  penumbra or in unipolar or mixed-polarity plage. The invisibility of
  umbra-to-umbra loops is new evidence that magnetoconvection drives
  solar-stellar coronal heating: evidently, the strong umbral field at
  both ends quenches the magnetoconvection and hence the heating. Our
  results from EUV observations and nonlinear force-free modeling of
  coronal magnetic field imply that, for any coronal loop on the Sun or
  on any other convective star, as long as the field can be braided by
  convection in at least one loop foot, the stronger the field in the
  loop, the stronger the coronal heating.

---------------------------------------------------------
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 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: 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: New Evidence that Magnetoconvection Drives Solar-Stellar
    Coronal Heating
Authors: Tiwari, Sanjiv K.; Thalmann, Julia K.; Panesar, Navdeep K.;
   Moore, Ronald L.; Winebarger, Amy R.
2017ApJ...843L..20T    Altcode: 2017arXiv170608035T
  How magnetic energy is injected and released in the solar
  corona, keeping it heated to several million degrees, remains
  elusive. Coronal heating generally increases with increasing magnetic
  field strength. From a comparison of a nonlinear force-free model
  of the three-dimensional active region coronal field to observed
  extreme-ultraviolet loops, we find that (1) umbra-to-umbra coronal
  loops, despite being rooted in the strongest magnetic flux, are
  invisible, and (2) the brightest loops have one foot in an umbra or
  penumbra and the other foot in another sunspot’s penumbra or in
  unipolar or mixed-polarity plage. The invisibility of umbra-to-umbra
  loops is new evidence that magnetoconvection drives solar-stellar
  coronal heating: evidently, the strong umbral field at both ends
  quenches the magnetoconvection and hence the heating. Broadly, our
  results indicate that depending on the field strength in both feet,
  the photospheric feet of a coronal loop on any convective star can
  either engender or quench coronal heating in the loop’s body.

---------------------------------------------------------
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: 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: 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: Suppression of heating of coronal loops rooted in opposite
    polarity sunspot umbrae
Authors: Tiwari, Sanjiv K.; Thalmann, Julia; Moore, Ronald; Panesar,
   Navdeep; Winebarger, Amy
2016shin.confE..61T    Altcode:
  EUV observations of active region (AR) coronae reveal the presence
  of loops at different temperatures. To understand the mechanisms that
  result in hotter or cooler loops, we study a typical bipolar AR, near
  solar disk center, which has moderate overall magnetic twist and at
  least one fully developed sunspot of each polarity. From AIA 193 and
  94 Å images we identify many clearly discernible coronal loops that
  connect plage or a sunspot of one polarity to an opposite-polarity
  plage region. The AIA 94 Å images show dim regions in the umbrae of
  the sunspots. To see which coronal loops are rooted in a dim umbral
  area, we performed a non-linear force-free field (NLFFF) modeling
  using photospheric vector magnetic field measurements obtained with
  the Heliosesmic Magnetic Imager (HMI) onboard SDO. The NLFFF model,
  validated by comparison of calculated model field lines with observed
  loops in AIA 193 and 94 Å, specifies the photospheric roots of the
  model field lines. Some model coronal magnetic field lines arch from
  the dim umbral area of the positive-polarity sunspot to the dim umbral
  area of a negative-polarity sunspot. Because these coronal loops are
  not visible in any of the coronal EUV and X-ray images of the AR, we
  conclude they are the coolest loops in the AR. This result suggests
  that the loops connecting opposite polarity umbrae are the least heated
  because the field in umbrae is so strong that the convective braiding
  of the field is strongly suppressed.

---------------------------------------------------------
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: 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.

---------------------------------------------------------
Title: Suppression of heating of coronal loops rooted in opposite
    polarity sunspot umbrae
Authors: Tiwari, Sanjiv K.; Thalmann, Julia K.; Moore, Ronald L.;
   Panesar, Navdeep; Winebarger, Amy R.
2016SPD....47.0336T    Altcode:
  EUV observations of active region (AR) coronae reveal the presence
  of loops at different temperatures. To understand the mechanisms that
  result in hotter or cooler loops, we study a typical bipolar AR, near
  solar disk center, which has moderate overall magnetic twist and at
  least one fully developed sunspot of each polarity. From AIA 193 and
  94 A images we identify many clearly discernible coronal loops that
  connect plage or a sunspot of one polarity to an opposite-polarity
  plage region. The AIA 94 A images show dim regions in the umbrae of
  the spots. To see which coronal loops are rooted in a dim umbral area,
  we performed a non-linear force-free field (NLFFF) modeling using
  photospheric vector magnetic field measurements obtained with the
  HMI onboard SDO. After validation of the NLFFF model by comparison of
  calculated model field lines and observed loops in AIA 193 and 94, we
  specify the photospheric roots of the model field lines. The model field
  then shows the coronal magnetic loops that arch from the dim umbral
  areas of the opposite polarity sunspots. Because these coronal loops
  are not visible in any of the coronal EUV and X-ray images of the AR,
  we conclude they are the coolest loops in the AR. This result suggests
  that the loops connecting opposite polarity umbrae are the least
  heated because the field in umbrae is so strong that the convective
  braiding of the field is strongly suppressed.We hypothesize that the
  convective freedom at the feet of a coronal loop, together with the
  strength of the field in the body of the loop, determines the strength
  of the heating. In particular, we expect the hottest coronal loops
  to have one foot in an umbra and the other foot in opposite-polarity
  penumbra or plage (coronal moss), the areas of strong field in which
  convection is not as strongly suppressed as in umbra. Many transient,
  outstandingly bright, loops in the AIA 94 movie of the AR do have this
  expected rooting pattern. We will also present another example of AR
  in which we find a similar rooting pattern of coronal loops.

---------------------------------------------------------
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.

---------------------------------------------------------
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: 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: 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: Evidence of suppressed heating of coronal loops rooted in
    opposite polarity sunspot umbrae
Authors: Tiwari, Sanjiv K.; Thalmann, Julia K.; Winebarger, Amy R.;
   Panesar, Navdeep K.; Moore, Ronald
2015TESS....120404T    Altcode:
  Observations of active region (AR) coronae in different EUV wavelengths
  reveal the presence of various loops at different temperatures. To
  understand the mechanisms that result in hotter or cooler loops, we
  study a typical bipolar AR, near solar disk center, which has moderate
  overall magnetic twist and at least one fully developed sunspot of
  each polarity. From AIA 193 and 94 A images we identify many clearly
  discernible coronal loops that connect opposite-polarity plage or
  a sunspot to a opposite-polarity plage region. The AIA 94 A images
  show dim regions in the umbrae of the spots. To see which coronal
  loops are rooted in a dim umbral area, we performed a non-linear
  force-free field (NLFFF) modeling using photospheric vector magnetic
  field measurements obtained with the Heliosesmic Magnetic Imager (HMI)
  onboard SDO. After validation of the NLFFF model by comparison of
  calculated model field lines and observed loops in AIA 193 and 94 A,
  we specify the photospheric roots of the model field lines. The model
  field then shows the coronal magnetic loops that arch from the dim
  umbral area of the positive-polarity sunspot to the dim umbral area of a
  negative-polarity sunspot. Because these coronal loops are not visible
  in any of the coronal EUV and X-ray images of the AR, we conclude they
  are the coolest loops in the AR. This result suggests that the loops
  connecting opposite polarity umbrae are the least heated because the
  field in umbrae is so strong that the convective braiding of the field
  is strongly suppressed.From this result, we further hypothesize that
  the convective freedom at the feet of a coronal loop, together with the
  strength of the field in the body of the loop, determines the strength
  of the heating. In particular, we expect the hottest coronal loops
  to have one foot in an umbra and the other foot in opposite-polarity
  penumbra or plage (coronal moss), the areas of strong field in which
  convection is not as strongly suppressed as in umbrae. Many transient,
  outstandingly bright, loops in the AIA 94 A movie of the AR do have
  this expected rooting pattern.

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Title: On the Structure and Evolution of a Polar Crown
    Prominence/Filament System
Authors: Panesar, N. K.; Innes, D. E.; Schmit, D. J.; Tiwari, S. K.
2014SoPh..289.2971P    Altcode: 2014arXiv1402.4989P; 2014SoPh..tmp...50P
  Polar crown prominences, that partially circle the Sun's poles between
  60° and 70° latitude, are made of chromospheric plasma. We aim to
  diagnose the 3D dynamics of a polar crown prominence using high-cadence
  EUV images from the Solar Dynamics Observatory (SDO)/AIA at 304,
  171, and 193 Å and the Ahead spacecraft of the Solar Terrestrial
  Relations Observatory (STEREO-A)/EUVI at 195 Å. Using time series
  across specific structures, we compare flows across the disk in
  195 Å with the prominence dynamics seen on the limb. The densest
  prominence material forms vertical columns that are separated by many
  tens of Mm and connected by dynamic bridges of plasma that are clearly
  visible in 304/171 Å two-colour images. We also observe intermittent
  but repetitious flows with velocity 15 km s<SUP>−1</SUP> in the
  prominence that appear to be associated with EUV bright points on
  the solar disk. The boundary between the prominence and the overlying
  cavity appears as a sharp edge. We discuss the structure of the coronal
  cavity seen both above and around the prominence. SDO/HMI and GONG
  magnetograms are used to infer the underlying magnetic topology. The
  evolution and structure of the prominence with respect to the magnetic
  field seems to agree with the filament-linkage model.

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Title: A Study of quiescent prominences using SDO and STEREO data
Authors: Panesar, Navdeep Kaur
2014PhDT........78P    Altcode:
  In this dissertation, we have studied the structure, dynamics and
  evolution of two quiescent prominences. Quiescent prominences are large
  structures and mainly associated with the quiet Sun region. For the
  analysis, we have used the high spatial and temporal cadence data from
  the Solar Dynamic Observatory (SDO), and the Solar Terrestrial Relations
  Observatory (STEREO). We combined the observations from two different
  directions and studied the prominence in 3D. In the study of polar crown
  prominence, we mainly investigated the prominence flows on limb and
  found its association with on-disk brightenings. The merging of diffused
  active region flux in the already formed chain of prominence caused
  the several brightenings in the filament channel and also injected the
  plasma upward with an average velocity of 15 km/s. In another study,
  we investigated the triggering mechanism of a quiescent tornado-like
  prominence. Flares from the neighboring active region triggered the
  tornado-like motions of the top of the prominence. Active region field
  contracts after the flare which results in the expansion of prominence
  cavity. The prominence helical magnetic field expands and plasma moves
  along the field lines which appear as a tornado-like activity. In
  addition, the thermal structure of the tornado-like prominence and
  neighbouring active region was investigated by analysing emission
  in six of the seven EUV channels from the SDO. These observational
  investigations led to our understanding of structure and dynamics
  of quiescent prominences, which could be useful for theoretical
  prominence models.

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Title: A solar tornado caused by flares
Authors: Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C.
2014IAUS..300..235P    Altcode:
  An enormous solar tornado was observed by SDO/AIA on 25 September
  2011. It was mainly associated with a quiescent prominence with an
  overlying coronal cavity. We investigate the triggering mechanism
  of the solar tornado by using the data from two instruments: SDO/AIA
  and STEREO-A/EUVI, covering the Sun from two directions. The tornado
  appeared near to the active region NOAA 11303 that produced three
  flares. The flares directly influenced the prominence-cavity system. The
  release of free magnetic energy from the active region by flares
  resulted in the contraction of the active region field. The cavity,
  owing to its superior magnetic pressure, expanded to fill this vacated
  space in the corona. We propose that the tornado developed on the top
  of the prominence due to the expansion of the prominence-cavity system.

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Title: A solar tornado triggered by flares?
Authors: Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C.
2013A&A...549A.105P    Altcode: 2012arXiv1211.6569P
  Context. Solar tornados are dynamical, conspicuously helical magnetic
  structures that are mainly observed as a prominence activity. <BR />
  Aims: We investigate and propose a triggering mechanism for the solar
  tornado observed in a prominence cavity by SDO/AIA on September 25,
  2011. <BR /> Methods: High-cadence EUV images from the SDO/AIA and
  the Ahead spacecraft of STEREO/EUVI are used to correlate three
  flares in the neighbouring active-region (NOAA 11303) and their EUV
  waves with the dynamical developments of the tornado. The timings
  of the flares and EUV waves observed on-disk in 195 Å are analysed
  in relation to the tornado activities observed at the limb in 171
  Å. <BR /> Results: Each of the three flares and its related EUV wave
  occurred within ten hours of the onset of the tornado. They have an
  observed causal relationship with the commencement of activity in
  the prominence where the tornado develops. Tornado-like rotations
  along the side of the prominence start after the second flare. The
  prominence cavity expands with the accelerating tornado motion after
  the third flare. <BR /> Conclusions: Flares in the neighbouring active
  region may have affected the cavity prominence system and triggered
  the solar tornado. A plausible mechanism is that the active-region
  coronal field contracted by the "Hudson effect" through the loss of
  magnetic energy as flares. Subsequently, the cavity expanded by its
  magnetic pressure to fill the surrounding low corona. We suggest that
  the tornado is the dynamical response of the helical prominence field
  to the cavity expansion. <P />Movies are available in electronic form
  at <A href="http://www.aanda.org">http://www.aanda.org</A>

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Title: A study of quiescent prominences using SDO and STEREO data
Authors: Panesar, Navdeep Kaur
2013PhDT.......414P    Altcode:
  No abstract at ADS