explanation      blue bibcodes open ADS page with paths to full text
Author name code: reames
ADS astronomy entries on 2022-09-14
author:Reames, Donald V.

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Title: Solar Energetic Particles: Spatial Extent and Implications
    of the H and He Abundances
Authors: Reames, Donald V.
2022SSRv..218...48R    Altcode: 2022arXiv220506883R
  One of the earliest indicators of the importance of shock acceleration
  of solar energetic particles (SEPs) was the broad spatial extent
  of the "gradual" SEP events produced as the shock waves, driven by
  wide, fast coronal mass ejections (CMEs), expand across the Sun with
  cross-field transport mediated by the shocks. Contrasting "impulsive"
  SEP events, with characteristic enhancements of <SUP>3</SUP>He and
  of heavy elements, are now associated with magnetic reconnection
  on open field lines in solar jets. However, large shock waves can
  also traverse pools of residual impulsive suprathermal ions and jets
  can produce fast CMEs that drive shock waves; in both cases shocks
  reaccelerate ions with the "impulsive" abundance signatures as well as
  coronal plasma. These more-complex events produce "excess protons" that
  identify this process, and recently, differences in the distribution
  of <SUP>4</SUP>He abundances have also been found to depend upon
  the combination of seed population and acceleration mode. Extreme
  differences in the <SUP>4</SUP>He abundances may reflect underlying
  differences in the abundances of the coronal regions being sampled by
  solar jets and, surprisingly, SEP events where shock waves sample two
  seed-particle populations seem to have about twice the <SUP>4</SUP>He/O
  ratio of those with a single source.

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Title: A Perspective on Solar Energetic Particles
Authors: Reames, Donald V.
2022FrASS...9.0864R    Altcode: 2022arXiv220315886R
  The author has been fortunate to observe and participate in the rise of
  the field of solar energetic particles (SEPs), from the early abundance
  studies, to the contemporary paradigm of shock acceleration in large
  SEP events, and element abundance enhancements that are power laws
  in mass-to-charge ratios from H to Pb. Through painful evolution the
  "birdcage" model and the "solar-flare myth" came and went, leaving us
  with shock waves and solar jets that can interact as sources of SEPs.

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Title: Energy Spectra vs. Element Abundances in Solar Energetic
    Particles and the Roles of Magnetic Reconnection and Shock
    Acceleration
Authors: Reames, Donald V.
2022SoPh..297...32R    Altcode: 2021arXiv211201568R
  We reexamine the relationship between energy spectral indices and
  element abundance enhancements in solar energetic particle (SEP) events
  at energies of a few MeV amu<SUP>−1</SUP>. We find a correlated
  behavior only in the largest gradual SEP4 events when all ions are
  accelerated from the ambient coronal plasma by shock waves driven by
  fast, wide coronal mass ejections (CMEs). This correlated abundance
  behavior can track complex time variations in the spectral indices
  during an event. In other (SEP3) events, CME-driven shock waves,
  days apart, sample seed particles from a single pool of suprathermal
  impulsive ions contributed earlier. Of the smaller, Fe-rich,
  impulsive SEP events, previously related to magnetic reconnection in
  solar jets, over half are subsequently reaccelerated by CME-driven
  shock waves (SEP2), causing typical ion intensities to have a 64%
  correlation with shock speeds. In these SEP2 events, the onset of
  shock acceleration is signaled by a new component in the abundances,
  large proton excesses. The remaining SEP1 events lack evidence of
  shock acceleration. However, for all these events (SEP1-SEP3) with
  abundances determined by magnetic reconnection, energy spectra and
  abundances are decoupled.

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Title: Fifty Years of 3 He-rich Events
Authors: Reames, Donald V.
2021FrASS...8..164R    Altcode: 2021arXiv211006251R
  The early 1970s saw a new and surprising feature in the composition
  of solar energetic particles (SEPs), resonant enhancements up to
  10,000-fold in the ratio 3He/4He that could even make 3He dominant
  over H in rare events. It was soon learned that these events also
  had enhancements in the abundances of heavier elements, such as a
  factor of ~10 enhancements in Fe/O, which was later seen to be part
  of a smooth increase in enhancements vs. mass-to-charge ratio A/Q
  from H to Pb rising by a factor of ~1000. These events were also
  associated with streaming 10 - 100 keV electrons that produce type
  III radio bursts. In recent years we have found these "impulsive"
  SEP events to be accelerated in islands of magnetic reconnection
  from plasma temperatures of 2 - 3 MK on open field lines in solar
  jets. Similar reconnection on closed loops traps the energy of the
  particles to produce hot (&gt;10 MK), bright flares. Sometimes impulsive
  SEP intensities are boosted by shock waves when the jets launch fast
  coronal mass ejections. No single theory yet explains both the sharp
  resonance in 3He and the smooth increase up to heavier elements; two
  processes seem to occur. Sometimes the efficient acceleration even
  exhausts the rare 3He in the source region, limiting its fluence.

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Title: Sixty Years of Element Abundance Measurements in Solar
    Energetic Particles
Authors: Reames, Donald V.
2021SSRv..217...72R    Altcode: 2021arXiv210714313R
  Sixty years ago the first observation was published showing solar
  energetic particles (SEPs) with a sampling of chemical elements with
  atomic numbers 6 ≤Z ≤18 above 40 MeV amu<SUP>−1</SUP>. Thus
  began study of the direct products of dynamic physics in the solar
  corona. As we have progressed from 4-min sounding-rocket samples
  to continuous satellite coverage of SEP events, we have extended
  the observations to the unusual distribution of element abundances
  throughout the periodic table. Small "impulsive" SEP events from
  islands of magnetic reconnection on open magnetic-field lines in solar
  jets generate huge enhancements in abundances of <SUP>3</SUP>He and
  of the heaviest elements, enhancements increasing as a power of the
  ion mass-to-charge ratio as (A /Q )<SUP>3.6</SUP>, on average. Solar
  flares involve the same physics but there the SEPs are trapped on
  closed loops, expending their energy as heat and light. The larger,
  energetic "gradual" SEP events are accelerated at shock waves driven
  by fast, wide coronal mass ejections (CMEs). However, these shocks can
  also reaccelerate ions from pools of residual suprathermal impulsive
  ions, and CMEs from jets can also drive fast shocks, complicating the
  picture. The underlying element abundances in SEP events represent
  the solar corona, which differs from corresponding abundances in the
  photosphere as a function of the first ionization potential (FIP) of
  the elements, distinguishing low-FIP (&lt;10 eV) ions from high-FIP
  neutral atoms as they expand through the chromosphere. Differences in
  FIP patterns of SEPs and the solar wind may distinguish closed- and
  open-field regions of formation at the base of the corona. Dependence
  of SEP acceleration upon A /Q allows best-fit estimation of ion Q
  -values and hence of the source plasma temperature of ∼1 - 3 MK,
  derived from abundances, which correlates with recent measures of
  temperatures using extreme ultraviolet emission from jets. Thus, element
  abundances in SEPs have become a powerful tool to study the underlying
  solar corona and to probe physical processes of broad astrophysical
  significance, from the "FIP effect" to magnetic reconnection and shock
  acceleration. New questions arise, however, about the theoretical
  basis of correlations of energy-spectral indices with power-laws of
  abundances, about the coexistence of separate resonant and non-resonant
  mechanisms for enhancements of <SUP>3</SUP>He and of heavy elements,
  about occasional events with unusual suppression of He and about the
  overall paucity of C in FIP comparisons.

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Title: The Evolution of Research on Abundances of Solar Energetic
    Particles
Authors: Reames, Donald
2021Univ....7..292R    Altcode:
  No abstract at ADS

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Title: Sulfur data from the Wind spacecraft for January 2014
Authors: Brooks, David; Yardley, Stephanie; Reames, Donald
2021zndo...4596004B    Altcode:
  No abstract at ADS

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Title: Solar Energetic Particles. A Modern Primer on Understanding
    Sources, Acceleration and Propagation
Authors: Reames, Donald V.
2021LNP...978.....R    Altcode: 2020arXiv201008517R
  In a field overflowing with beautiful images of the Sun, solar energetic
  particle (SEP) events are a hidden asset, perhaps a secret weapon,
  that can sample the solar corona and carry away unique imprints of its
  most bizarre and violent physics. Only recently have we found that the
  abundances of the elements in SEPs carry a wealth of data, not only on
  their own acceleration and history, but on plasma temperatures at their
  source, and on aspects of the genesis of the corona itself. SEPs are the
  tangible product of differing energetic outbursts at the Sun. They come
  in extremes. Little "impulsive" SEP events from magnetic reconnection
  in solar jets (also in flares), have most unusual 1000-fold resonant
  enhancements of 3He and of heavy elements like Au or Pb, while large
  "gradual" SEP events accelerated at shock waves driven by coronal mass
  ejections (CMEs), sample the composition of the corona itself, but
  also accelerate GeV protons that threaten Mars-bound astronauts with
  hazardous radiation. Direct SEP measurements plus solar images provide
  complimentary, "multi-messenger" data on high-energy physics at the Sun.

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Title: On the Correlation between Energy Spectra and Element
    Abundances in Solar Energetic Particles
Authors: Reames, Donald V.
2021SoPh..296...24R    Altcode: 2020arXiv200806985R
  In solar energetic particle (SEP) events, the physical processes
  of both shock acceleration and scattering during transport can
  cause energy-spectral indices to be correlated with enhancement or
  suppression of element abundances versus mass-to-charge ratios A /Q
  . We observe correlations for those "gradual" SEP events where shock
  waves accelerate ions from the ambient coronal plasma, but there are
  no such correlations for "impulsive" SEP events produced by magnetic
  reconnection in solar jets, where abundance enhancement in different
  events vary from (A<SUP>/Q ) +2</SUP> to (A<SUP>/Q ) +8</SUP>, nor
  are there correlations when shock waves reaccelerate these residual
  impulsive ions. In the latter events the abundances are determined
  separately, prior to the accelerated spectra. Events with correlated
  spectra and abundances show a wide variety of interesting behavior
  that has not been described previously. Small and moderate gradual SEP
  events, with relative abundances typically depending approximately upon
  (A<SUP>/Q ) −1</SUP> and the spectra upon energy E<SUP>−2.5</SUP>,
  vary little with time. Large SEP events show huge temporal variations
  skirting the correlation line; in one case O spectra vary with time
  from E<SUP>−1</SUP> to E<SUP>−5</SUP> while abundances vary from
  (A<SUP>/Q ) +1</SUP> to (A<SUP>/Q ) −2</SUP> during the event. In very
  large events, streaming-limited transport through proton-generated
  resonant Alfvén waves flattens the spectra and enhances heavy
  ion abundances prior to local shock passage, then steepens the
  spectra and reduces enhancements afterward, recapturing the typical
  correlation. Systematic correlation of spectra and element abundances
  provide a new perspective on the "injection problem" of ion selection
  by shocks and on the physics of SEP acceleration and transport.

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Title: Distinguishing the Rigidity Dependences of Acceleration and
    Transport in Solar Energetic Particles
Authors: Reames, Donald V.
2020SoPh..295..113R    Altcode: 2020arXiv200611338R
  In solar energetic particle (SEP) events, the power-law dependence
  of element abundance enhancements on their mass-to-charge ratios
  [A /Q ] provides a new tool that measures the combined rigidity
  dependences from both acceleration and transport. Distinguishing
  between these two processes can be challenging. However, the effects
  of acceleration dominate when SEP events are small or when the ions
  propagate scatter-free, and transport can dominate the temporal time
  evolution of large events with streaming-limited intensities. Magnetic
  reconnection in solar jets produces positive powers of A /Q from +2 to
  +7 and shock acceleration produces mostly negative powers from −2
  to +1 in small and moderate SEP events where transport effects are
  minimal. This variation in the rigidity dependence of shock acceleration
  may reflect the non-planar structure, complexity, and temporal time
  variation of coronal shocks themselves. Wave amplification by streaming
  protons in the largest SEP events suppresses the escape of ions with low
  A /Q , creating observed powers of A /Q from +1 to +3 upstream of the
  accelerating shock, decreasing to small negative powers downstream. For
  shock acceleration, the powers of A /Q are correlated with the energy
  spectral indices of He, O, and Fe, yet unexplained departures exist.

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Title: Virtues of Including Hydrogen in the Patterns of Element
    Abundances in Solar Energetic Particles
Authors: Reames, Donald V.
2020arXiv200412229R    Altcode:
  We revisit a multi-spacecraft study of the element abundances of
  solar energetic particles (SEPs) in the 23 January 2012 event, where
  the power-law pattern of enhancements versus the mass-to-charge ratio
  A/Q for the elements C through Fe was partly disrupted by a break near
  Mg, which turned out to be an unfortunate distraction. In the current
  article we find that extending that least-squares fits for C - Fe down
  to H at A/Q = 1 lends much more credence to the power laws, even though
  H itself was not included in the fits. We also investigate the extent
  of an adiabatically invariant "reservoir" of magnetically-trapped
  particles behind the shock wave in this event.

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Title: Four Distinct Pathways to the Element Abundances in Solar
    Energetic Particles
Authors: Reames, Donald V.
2020SSRv..216...20R    Altcode: 2019arXiv191206691R
  Based upon recent evidence from abundance patterns of chemical elements
  in solar energetic particles (SEPs), and, ironically, the belated
  inclusion of H and He, we can distinguish four basic SEP populations:
  (1) SEP1—pure "impulsive" SEPs are produced by magnetic reconnection
  in solar jets showing steep power-law enhancements of 1 ≤Z ≤56
  ions versus charge-to-mass ratio A /Q from a ≈3 MK plasma. (2)
  SEP2—ambient ions, mostly protons, plus SEP1 ions reaccelerated
  by the shock wave driven by the narrow coronal mass ejection (CME)
  from the same jet. (3) SEP3—a "gradual" SEP event is produced when
  a moderately fast, wide CME-driven shock wave barely accelerates
  ambient protons while preferentially accelerating accumulated remnant
  SEP1 ions from an active region fed by multiple jets. (4) SEP4—a
  gradual SEP event is produced when a very fast, wide CME-driven shock
  wave is completely dominated by ambient coronal seed population of
  0.8-1.8 MK plasma usually producing a full power law vs. A /Q for 1
  ≤Z ≤56 ions. We begin with element abundances in the photosphere
  that are fractionated during transport up to the corona based upon
  their first ionization potential (FIP); this important "FIP effect"
  for SEPs provides our reference abundances and is different for SEPs
  from that for the solar wind. We then show evidence for each of the
  processes of acceleration, reacceleration, and transport that conspire
  to produce the four abundances patterns we distinguish.

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Title: Element Abundances of Solar Energetic Particles and the
    Photosphere, the Corona, and the Solar Wind
Authors: Reames
2019Atoms...7..104R    Altcode: 2019arXiv191001209R
  From a turbulent history, the study of abundances of elements in solar
  energetic particles (SEPs) has grown into an extensive field that
  probes the solar corona and the physical processes of SEP acceleration
  and transport. Underlying SEPs are the abundances of the solar corona,
  which differ from photospheric abundances as a function of the first
  ionization potentials (FIPs) of the elements. The FIP-dependence of
  SEPs also differs from that of the solar wind; each has a different
  magnetic environment where low-FIP ions and high-FIP neutral atoms
  rise toward the corona. Two major sources generate SEPs: The small
  "impulsive" SEP events are associated with magnetic reconnection
  in solar jets that produce 1000-fold enhancements from H to Pb as a
  function of mass-to-charge ratio A/Q, and also 1000-fold enhancements
  in 3He/4He produced by resonant wave-particle interactions. In
  large "gradual" events, SEPs are accelerated at shock waves driven
  out from the Sun by wide, fast coronal mass ejections (CMEs). A/Q
  dependence of ion transport allows us to estimate Q and hence the
  source plasma temperature T. Weaker shock waves favor reacceleration
  of suprathermal ions accumulated from earlier impulsive SEP events,
  along with protons from the ambient plasma. In strong shocks the ambient
  plasma dominates. Ions from impulsive sources have T ~ 3 MK; those from
  ambient coronal plasma have T = 1 - 2 MK. These FIP- and A/Q-dependences
  explore complex new interactions in the corona and in SEP sources.

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Title: Excess H, Suppressed He, and the Abundances of Elements in
    Solar Energetic Particles
Authors: Reames, Donald V.
2019SoPh..294..141R    Altcode: 2019arXiv190802321R
  Recent studies of the abundances of H and He relative to those
  of heavier ions in solar energetic particle (SEP) events suggest
  new features in the underlying physics. Impulsive SEP events,
  defined by uniquely large enhancements of Fe/O, emerge from magnetic
  reconnection in solar jets. In small, "pure," shock-free, impulsive SEP
  events, protons with mass-to-charge ratio A /Q =1 fit the power-law
  dependence of element abundance enhancements versusA /Q extrapolated
  from the heavier elements 6 ≤Z ≤56 . Sometimes these events have
  order-of-magnitude suppressions of He, even though H fits with heavier
  elements, perhaps because of the slower ionization of He during a
  rapid rise of plasma from the chromosphere. In larger impulsive SEP
  events, He fits, but there are large proton excesses relative to the
  power-law fit of Z &gt;2 ions, probably because associated coronal
  mass ejections (CMEs) drive shock waves fast enough to reaccelerate
  the impulsive SEPs but also to sample protons from the ambient solar
  plasma. In contrast, gradual SEP events are accelerated by wide, fast
  CME-driven shock waves, but those with smaller, weaker shocks, perhaps
  quasi-perpendicular, favor impulsive suprathermal residue left by many
  previous jets, again supplemented with excess protons from ambient
  coronal plasma. In the larger, more common gradual SEP events, faster,
  stronger shock waves sample the ambient coronal plasma more deeply,
  overwhelming any impulsive-ion component, so that proton abundances
  again fit the same power-law distribution as all other elements. Thus,
  studies of the power-law behavior in A /Q of SEP element abundances give
  compelling new information on the varying physics of SEP acceleration
  and properties of the underlying corona.

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Title: Hydrogen and the Abundances of Elements in Gradual Solar
    Energetic-Particle Events
Authors: Reames, Donald V.
2019SoPh..294...69R    Altcode: 2019arXiv190203208R
  Despite its dominance, hydrogen has been largely ignored in studies
  of the abundance patterns of the chemical elements in gradual solar
  energetic particle (SEP) events; those neglected abundances show
  a surprising new pattern of behavior. Abundance enhancements of
  elements with 2 ≤Z ≤56 , relative to coronal abundances, show a
  power-law dependence versus their average mass-to-charge ratio A /Q
  , which varies from event to event and with time during events. The
  ion charge states Q depend upon the source plasma temperature T . For
  most gradual SEP events, shock waves have accelerated ambient coronal
  material with T &lt;2 MK with decreasing power laws in A /Q . In this
  case, the proton abundances agree rather well with the power-law fits
  extrapolated from elements with Z ≥6 at A /Q &gt;2 down to hydrogen
  at A /Q =1 . Thus the abundances of the elements with Z ≥6 fairly
  accurately predict the observed abundance of H, at a similar velocity,
  in most SEP events. However, for those gradual SEP events where ion
  enhancements follow positive powers of A /Q , especially those with T
  &gt;2 MK where shock waves have reaccelerated residual suprathermal
  ions from previous impulsive SEP events, proton abundances commonly
  exceed the extrapolated expectation, usually by a factor of order
  ten. This is a new and unexpected pattern of behavior that is unique
  to the abundances of protons and may be related to the need for more
  streaming protons to produce sufficient waves for scattering and
  acceleration of more heavy ions at the shock.

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Title: Hydrogen and the Abundances of Elements in Impulsive Solar
    Energetic-Particle Events
Authors: Reames, Donald V.
2019SoPh..294...37R    Altcode: 2019arXiv190104369R
  Hydrogen has been almost completely ignored in studies of the abundance
  patterns of the chemical elements in solar energetic particles
  (SEPs). We seek to find impulsive events where H fits these abundance
  patterns and document the events that do not, suggesting possible
  reasons for the disparity. For 24% of the smaller impulsive SEP events,
  the relative abundance of H fits within one standard deviation of the
  power-law fit of the abundances of elements 6 ≤Z ≤56 , relative
  to coronal abundances. In impulsive events with high intensities, H
  can be 10 to 100 times its expected value. In a few of these larger
  events, increased scattering at high wavenumber may preferentially
  detain H, perhaps with self-amplified waves; in some events pre-event
  proton background may contribute. In most large impulsive SEP events,
  however, associated shock waves must play a much greater role than
  previously thought; fast (&gt;500 kms−<SUP>1</SUP>) coronal mass
  ejections contribute to 62% of impulsive events. Shocks may sample
  protons from the ambient coronal plasma or residual background as well
  as reaccelerating heavier impulsive SEP ions injected from the region
  of magnetic reconnection in solar jets. Excess H may be a signature
  of shock acceleration.

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Title: Helium Suppression in Impulsive Solar Energetic-Particle Events
Authors: Reames, Donald V.
2019SoPh..294...32R    Altcode: 2018arXiv181201635R
  We have studied the element abundances and energy spectra of the small
  "He-poor" impulsive solar energetic-particle (SEP) events, comparing
  them with other impulsive SEP events with more-normal abundances of
  He. He-poor events can have abundances as low as He/O ≈ 2, while
  both impulsive and gradual SEP events usually have source abundances of
  30 ≤He/O≤100 with mean values of ≈ 50 - 60. He/C ratios are not
  only low, but often decrease with energy in He-poor events. Abundance
  enhancement patterns of other elements with atomic numbers 6 ≤Z
  ≤56 , and likely values of their mass-to-charge ratios A /Q , are
  generally unaltered in He-poor events, as are the probable source-plasma
  temperatures of 2.5 - 3.2 MK for all impulsive SEP events. One He-poor
  event is also an example of a rarer C-poor event with C/O=0.08 ±0.04 ,
  suppressed by a factor over five from the mean. We discuss suggestions
  of a possible A /Q threshold during acceleration and of the sluggish
  ionization of He entering the corona, because of its uniquely high
  first ionization potential (FIP), but the suppression of He and the
  decline of He/C with energy is difficult to explain if both He and C
  are fully ionized with A /Q =2 as expected at 2.5 - 3.2 MK. Although
  less dramatic, a possible excess enhancement of Ne in some impulsive
  SEP events is also considered. Possible causes of the large ≈
  30% spectral and abundance variations in impulsive events are also
  discussed. However, the physics of the He-poor events remains a mystery.

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Title: Corotating Shock Waves and the Solar-wind Source of Energetic
Ion Abundances: Power Laws in A /Q
Authors: Reames, Donald V.
2018SoPh..293..144R    Altcode: 2018arXiv180806132R
  We find that element abundances in energetic ions accelerated by
  shock waves formed at corotating interaction regions (CIRs) mirror
  the abundances of the solar wind modified by a decreasing power-law
  dependence on the mass-to-charge ratio A /Q of the ions. This behavior
  is similar in character to the well-known power-law dependence on A /Q
  of abundances in large gradual solar energetic particles (SEP). The
  CIR ions reflect the pattern of A /Q , with Q values of the source
  plasma temperature or freezing-in temperature of 1.0 - 1.2 MK typical
  of the fast solar wind in this case. Thus the relative ion abundances
  in CIRs are of the form (A<SUP>/Q ) a</SUP>, where a is nearly always
  negative and evidently decreases with distance from the shocks, which
  usually begin beyond 1 AU. For one unusual historic CIR event where
  a ≈0 , the reverse shock wave of the CIR seems to occur at 1 AU,
  and these abundances of the energetic ions become a direct proxy for
  the abundances of the fast solar wind.

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Title: Solar particle event storm shelter requirements for missions
    beyond low Earth orbit
Authors: Townsend, L. W.; Adams, J. H.; Blattnig, S. R.; Clowdsley,
   M. S.; Fry, D. J.; Jun, I.; McLeod, C. D.; Minow, J. I.; Moore,
   D. F.; Norbury, J. W.; Norman, R. B.; Reames, D. V.; Schwadron,
   N. A.; Semones, E. J.; Singleterry, R. C.; Slaba, T. C.; Werneth,
   C. M.; Xapsos, M. A.
2018LSSR...17...32T    Altcode:
  No abstract at ADS

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Title: Abundances, Ionization States, Temperatures, and FIP in Solar
    Energetic Particles
Authors: Reames, Donald V.
2018SSRv..214...61R    Altcode: 2017arXiv170900741R
  The relative abundances of chemical elements and isotopes have been
  our most effective tool in identifying and understanding the physical
  processes that control populations of energetic particles. The
  early surprise in solar energetic particles (SEPs) was 1000-fold
  enhancements in {}<SUP>3</SUP>He/{}<SUP>4</SUP>He from resonant
  wave-particle interactions in the small "impulsive" SEP events that
  emit electron beams that produce type III radio bursts. Further
  studies found enhancements in Fe/O, then extreme enhancements in
  element abundances that increase with mass-to-charge ratio A/Q,
  rising by a factor of 1000 from He to Au or Pb arising in magnetic
  reconnection regions on open field lines in solar jets. In contrast,
  in the largest SEP events, the "gradual" events, acceleration occurs
  at shock waves driven out from the Sun by fast, wide coronal mass
  ejections (CMEs). Averaging many events provides a measure of solar
  coronal abundances, but A/Q-dependent scattering during transport
  causes variations with time; thus if Fe scatters less than O, Fe/O is
  enhanced early and depleted later. To complicate matters, shock waves
  often reaccelerate impulsive suprathermal ions left over or trapped
  above active regions that have spawned many impulsive events. Direct
  measurements of ionization states Q show coronal temperatures of 1-2
  MK for most gradual events, but impulsive events often show stripping
  by matter traversal after acceleration. Direct measurements of Q are
  difficult and often unavailable. Since both impulsive and gradual SEP
  events have abundance enhancements that vary as powers of A/Q, we can
  use abundances to deduce the probable Q-values and the source plasma
  temperatures during acceleration, ≈3 MK for impulsive SEPs. This
  new technique also allows multiple spacecraft to measure temperature
  variations across the face of a shock wave, measurements otherwise
  unavailable and provides a new understanding of abundance variations
  in the element He. Comparing coronal abundances from SEPs and from
  the slow solar wind as a function of the first ionization potential
  (FIP) of the elements, remaining differences are for the elements C,
  P, and S. The theory of the fractionation of ions by Alfvén waves
  shows that C, P, and S are suppressed because of wave resonances
  during chromospheric transport on closed magnetic loops but not on open
  magnetic fields that supply the solar wind. Shock waves can accelerate
  ions from closed coronal loops that easily escape as SEPs, while the
  solar wind must emerge on open fields.

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Title: The "FIP Effect" and the Origins of Solar Energetic Particles
    and of the Solar Wind
Authors: Reames, Donald V.
2018SoPh..293...47R    Altcode: 2018arXiv180105840R
  We find that the element abundances in solar energetic particles (SEPs)
  and in the slow solar wind (SSW), relative to those in the photosphere,
  show different patterns as a function of the first ionization potential
  (FIP) of the elements. Generally, the SEP and SSW abundances reflect
  abundance samples of the solar corona, where low-FIP elements, ionized
  in the chromosphere, are more efficiently conveyed upward to the corona
  than high-FIP elements that are initially neutral atoms. Abundances of
  the elements, especially C, P, and S, show a crossover from low to high
  FIP at ≈10 eV in the SEPs but ≈14 eV for the solar wind. Naively,
  this seems to suggest cooler plasma from sunspots beneath active
  regions. More likely, if the ponderomotive force of Alfvén waves
  preferentially conveys low-FIP ions into the corona, the source plasma
  that eventually will be shock-accelerated as SEPs originates in magnetic
  structures where Alfvén waves resonate with the loop length on closed
  magnetic field lines. This concentrates FIP fractionation near the top
  of the chromosphere. Meanwhile, the source of the SSW may lie near the
  base of diverging open-field lines surrounding, but outside of, active
  regions, where such resonance does not exist, allowing fractionation
  throughout the chromosphere. We also find that energetic particles
  accelerated from the solar wind itself by shock waves at corotating
  interaction regions, generally beyond 1 AU, confirm the FIP pattern
  of the solar wind.

---------------------------------------------------------
Title: The Abundance of Helium in the Source Plasma of Solar
    Energetic Particles
Authors: Reames, Donald V.
2017SoPh..292..156R    Altcode: 2017arXiv170805034R
  Studies of patterns of abundance enhancements of elements, relative
  to solar coronal abundances, in large solar energetic-particle (SEP)
  events, and of their power-law dependence on the mass-to-charge
  ratio, A /Q , of the ions, have been used to determine the effective
  source-plasma temperature, T , that defines the Q -values of the
  ions. We find that a single assumed value for the coronal reference He/O
  ratio in all SEP events is often inconsistent with the transport-induced
  power-law trend of the other elements. In fact, the coronal He/O varies
  rather widely from one SEP event to another. In the large Fe-rich SEP
  events with T ≈3 MK, where shock waves, driven out by coronal mass
  ejections (CMEs), have reaccelerated residual ions from impulsive
  suprathermal events that occur earlier in solar active regions,
  He/O≈90 , a ratio similar to that in the slow solar wind, which may
  also originate from active regions. Ions in the large SEP events with
  T &lt;2 MK may be accelerated outside active regions, and have values
  of 40 ≤He/O≤60 . Mechanisms that determine coronal abundances,
  including variations of He/O, are likely to occur near the base of the
  corona (at ≈1.1 R<SUB>S</SUB>) and thus to affect both SEPs (at 2 -
  3 R<SUB>S</SUB>) and the solar wind. Other than He, reference coronal
  abundances for heavier elements show little temperature dependence or
  systematic difference between SEP events; He, the element with the
  highest first-ionization potential, is unique. The CME-driven shock
  waves probe the same regions of space, at ≈2 R<SUB>S</SUB> near
  active regions, which are also likely sources of the slow solar wind,
  providing complementary information on conditions in those regions.

---------------------------------------------------------
Title: Spatial Distribution of Element Abundances and Ionization
    States in Solar Energetic-Particle Events
Authors: Reames, Donald V.
2017SoPh..292..113R    Altcode: 2017arXiv170507471R
  We have studied the spatial and temporal distribution of abundances of
  chemical elements in large "gradual" solar energetic-particle (SEP)
  events, and especially the source plasma temperatures, derived from
  those abundances, using measurements from the Wind and Solar TErrestrial
  RElations Observatory (STEREO) spacecraft, widely separated in solar
  longitude. A power-law relationship between abundance enhancements and
  mass-to-charge ratios [A /Q ] of the ions can be used to determine
  Q -values and source plasma temperatures at remote spacecraft with
  instruments that were not designed for charge-state measurements. We
  search for possible source variations along the accelerating shock wave,
  finding one clear case where the accelerating shock wave appears to
  dispatch ions from 3.2 ±0.8 MK plasma toward one spacecraft and those
  from 1.6 ±0.2 MK plasma toward another, 116<SUP>∘</SUP> away. The
  difference persists for three days and then fades away. Three other
  SEP events show less-extreme variation in source temperatures at
  different spacecraft, in one case observed over 222<SUP>∘</SUP> in
  longitude. This initial study shows how the power-law relation between
  abundance enhancements and ion A /Q -values provides a new technique to
  determine Q and plasma temperatures in the seed population of SEP ions
  over a broad region of space using remote spacecraft with instruments
  that were not originally designed for measurements of ionization states.

---------------------------------------------------------
Title: Solar Energetic Particles
Authors: Reames, Donald V.
2017LNP...932.....R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Element Abundances and Source Plasma Temperatures of Solar
    Energetic Particles
Authors: Reames, Donald V.
2016JPhCS.767a2023R    Altcode: 2016arXiv161200030R
  Thirty years ago Breneman and Stone [1] observed that the enhancement
  or suppression of element abundances in large solar energetic-particle
  (SEP) events varies as a power of the mass-to-charge ratio, A/Q, of
  the elements. Since Q during acceleration or transport may depend upon
  the source plasma temperature T, the pattern of element enhancements
  can provide a best-fit measure of T. The small SEP events we call
  <SUP>3</SUP>He-rich or “impulsive” show average enhancements,
  relative to coronal abundances, rising as the 3.6 power of A/Q to a
  factor of ∼1000 for (76&lt;Z&lt;82)/O and temperature in the range
  2-4 MK. This acceleration is believed to occur in islands of magnetic
  reconnection on open field lines in solar flares and jets. It has
  been recently found that the large shock-accelerated “gradual”
  SEP events have a broad range of source plasma temperatures; 69%
  have coronal temperatures of T &lt;1.6 MK, while 24% have T ∼ 3 MK,
  the latter suggesting a seed population containing residual impulsive
  suprathermal ions. Most of the large event-to-event abundance variations
  and their time variation are largely explained by variations in T
  magnified by A/Q-dependent fractionation during transport. However,
  the non-thermal variance of impulsive SEP events (∼30%) exceeds that
  of the ∼3 MK gradual events (∼10%) so that several small impulsive
  events must be averaged together with the ambient plasma to form the
  seed population for shock acceleration in these events.

---------------------------------------------------------
Title: The Origin of Element Abundance Variations in Solar Energetic
    Particles
Authors: Reames, Donald V.
2016SoPh..291.2099R    Altcode: 2016SoPh..tmp..110R; 2016arXiv160306233R
  Abundance enhancements, during acceleration and transport in both
  gradual and impulsive solar energetic particle (SEP) events, vary
  approximately as power laws in the mass-to-charge ratio [A /Q ] of the
  ions. Since the Q -values depend upon the electron temperature of the
  source plasma, this has allowed a determination of this temperature
  from the pattern of element-abundance enhancements and a verification
  of the expected inverse-time dependence of the power of A /Q for
  diffusive transport of ions from the SEP events, with scattering mean
  free paths found to be between 0.2 and 1 AU. SEP events derived from
  plasma of different temperatures map into different regions in typical
  cross-plots of abundances, spreading the distributions. In comparisons
  of SEP events with temperatures above 2 MK, impulsive events show
  much broader non-thermal variation of abundances than do gradual
  events. The extensive shock waves accelerating ions in gradual events
  may average over much of an active region where numerous but smaller
  magnetic reconnections, "nanojets", produce suprathermal seed ions,
  thus averaging over varying abundances, while an impulsive SEP event
  only samples one local region of abundance variations. Evidence for a
  reference He/O-abundance ratio of 91, rather than 57, is also found for
  the hotter plasma. However, while this is similar to the solar-wind
  abundance of He/O, the solar-wind abundances otherwise provide an
  unacceptably poor reference for the SEP-abundance enhancements,
  generating extremely large errors.

---------------------------------------------------------
Title: Temperature of the Source Plasma in Gradual Solar Energetic
    Particle Events
Authors: Reames, Donald V.
2016SoPh..291..911R    Altcode: 2015arXiv150908948R; 2016SoPh..tmp...25R
  Scattering during interplanetary transport of particles during
  large, "gradual" solar energetic-particle (SEP) events can cause
  element abundance enhancements or suppressions that depend upon the
  mass-to-charge ratio [A /Q ] of the ions as an increasing function
  early in events and a decreasing function of the residual scattered ions
  later. Since the Q -values for the ions depend upon the source plasma
  temperature [T ], best fits of the power-law dependence of enhancements
  vs.A /Q can determine T . These fits provide a fundamentally new
  method to determine the most probable value of T for these events in
  the energy region 3 -10 MeVamu−<SUP>1</SUP>. Complicated variations
  in the grouping of element enhancements or suppressions match similar
  variations in A /Q at the best-fit temperature. We find that fits to
  the times of increasing and decreasing powers give similar values of
  T , in the range of 0.8 - 1.6 MK for 69 % of events, consistent with
  the acceleration of ambient coronal plasma by shock waves driven out
  from the Sun by coronal mass ejections (CMEs). However, 24 % of the SEP
  events studied showed plasma of 2.5 - 3.2 MK, typical of that previously
  determined for the smaller impulsive SEP events; these particles may
  be reaccelerated preferentially by quasi-perpendicular shock waves
  that require a high injection threshold that the impulsive-event ions
  exceed or simply by high intensities of impulsive suprathermal ions at
  the shock. The source-temperature distribution of ten higher-energy
  ground-level events (GLEs) in the sample is similar to that of the
  other gradual events, at least for SEPs in the energy-range of 3 -10
  MeVamu−<SUP>1</SUP>. Some events show evidence that a portion of
  the ions may have been further stripped of electrons before the shock
  acceleration; such events are smaller and tend to cluster late in the
  solar cycle.

---------------------------------------------------------
Title: Dropout of Directional Electron Intensities in Large Solar
    Energetic Particle Events
Authors: Tan, Lun C.; Reames, Donald V.
2016ApJ...816...93T    Altcode:
  In the “gradual” solar energetic particle (SEP) event during solar
  cycle 23 we have observed the dispersionless modulation (“dropout”)
  in directional intensities of nonrelativistic electrons. The average
  duration of dropout periods is ∼0.8 hr, which is consistent with the
  correlation scale of solar wind turbulence. During the dropout period
  electrons could display scatter-free transport in an intermittent
  way. Also, we have observed a decrease in the anisotropic index of
  incident electrons with increasing electron energy (E<SUB>e</SUB>),
  while the index of scattered/reflected electrons is nearly independent
  of E<SUB>e</SUB>. We hence perform an observational examination
  of the correlation between the anisotropic index of low-energy
  scattered/reflected electrons and the signature of the locally measured
  solar wind turbulence in the dissipation range, which is responsible
  for resonant scattering of nonrelativistic electrons. Since during
  the dropout period the slab turbulence fraction is dominant (0.8 ±
  0.1), we pay close attention to the effect of slab fraction on the
  correlation examined. Our observation is consistent with the simulation
  result that in the dominance of the slab turbulence component there
  should exist a dispatched structure of magnetic flux tubes, along
  which electrons could be transported in a scatter-free manner. Since
  a similar phenomenon is exhibited in the “impulsive” SEP event,
  electron dropout should be a transport effect. Therefore, being
  different from most ion dropout events, which are due to a compact
  flare source, the dropout of directional electron intensities should
  be caused by the change of turbulence status in the solar wind.

---------------------------------------------------------
Title: What Are the Sources of Solar Energetic Particles? Element
    Abundances and Source Plasma Temperatures
Authors: Reames, Donald V.
2015SSRv..194..303R    Altcode: 2015SSRv..tmp..103R; 2015arXiv151003449R
  We have spent 50 years in heated discussion over which populations
  of solar energetic particles (SEPs) are accelerated at flares and
  which by shock waves driven out from the Sun by coronal mass ejections
  (CMEs). The association of the large "gradual" SEP events with shock
  acceleration is supported by the extensive spatial distribution of
  SEPs and by the delayed acceleration of the particles. Recent STEREO
  observations have begun to show that the particle onset times correspond
  to the observed time of arrival of the shock on the observer's magnetic
  flux tube and that the SEP intensities are related to the local
  shock speed. The relative abundances of the elements in these gradual
  events are a measure of those in the ambient solar corona, differing
  from those in the photosphere by a widely-observed function of the
  first ionization potential (FIP) of the elements. SEP events we call
  "impulsive", the traditional "<SUP>3</SUP>He-rich" events with enhanced
  heavy-element abundances, are associated with type III radio bursts,
  flares, and narrow CMEs; they selectively populate flux tubes that
  thread a localized source, and they are fit to new particle-in-cell
  models of magnetic reconnection on open field lines as found in solar
  jets. These models help explain the strong enhancements seen in heavy
  elements as a power (of 2-8) in the mass-to-charge ratio A/Q throughout
  the periodic table from He to Pb. A study of the temperature dependence
  of A/Q shows that the source plasma in impulsive SEP events must lie in
  the range of 2-4 MK to explain the pattern of abundances. This is much
  lower than the temperatures of &gt;10 MK seen on closed loops in solar
  flares. Recent studies of A/Q-dependent enhancements or suppressions
  from scattering during transport show source plasma temperatures in
  gradual SEP events to be 0.8-1.6 MK in 69 % of the events, i.e. coronal
  plasma; 24 % of the events show reaccelerated impulsive-event material.

---------------------------------------------------------
Title: Coronal Sources of Impulsive Fe-Rich Solar Energetic Particle
    Events
Authors: Kahler, S.; Reames, D.; Cliver, E.
2015ICRC...34...49K    Altcode: 2015arXiv150909260K; 2015PoS...236...49K
  We review recent work on 111 Fe-rich impulsive solar energetic
  ($\sim$ 3 MeV/nuc) particle (SEP) events observed from 1994 to
  2013. Strong elemental abundance enhancements scale with A/Q, the
  ion mass-to-charge ratio, as (A/Q)$^{\alpha}$, where 2 $&lt; \alpha
  &lt;$ 8 for different events. Most Fe-rich events are associated with
  both flares and coronal mass ejections (CMEs), and those with larger
  $\alpha$ are associated with smaller flares, slower and narrower CMEs,
  and lower SEP event fluences. The narrow equilibrium temperature
  range required to fit the observed A/Q enhancements is 2.5--3.2 MK,
  far below the characteristic flare temperatures of $&gt;$ 10 MK. Only
  a small number of SEP events slightly outside this temperature range
  were found in an expanded search of impulsive Fe-rich events. Event
  characteristics are similar for events isolated in time and those
  occurring in clusters. The current challenge is to determine the
  solar sources of the Fe-rich events. Ambient coronal regions in the
  2.5--3.2 MK range are broadly distributed both in and outside active
  regions. We explore the possibility of acceleration from thermal plasmas
  at reconnecting current sheets in the context of observed standard and
  blowout jets. Recent current sheet reconnection modelling provides a
  basis for the A/Q enhancements.

---------------------------------------------------------
Title: Where are the Sources of Solar Energetic Particles?
Authors: Reames, Donald V.
2015shin.confE..64R    Altcode:
  We have spent 50 years arguing over which populations of solar
  energetic particles (SEPs) are accelerated at flares and which
  by shock waves driven out from the Sun by coronal mass ejections
  (CMEs). The association of the large 'gradual' SEP events with shock
  acceleration is supported by the extensive spatial distribution of
  the particles. Recent STEREO observations have begun to show that the
  particle onset times corresponds to the observed time of arrival of
  the shock at the observer's magnetic flux tube and the SEP intensities
  are related to the local shock speed. The relative abundances of the
  elements in these gradual events are a measure of those in the ambient
  solar corona, differing from those in the photosphere by a well-studied
  function of the first ionization potential (FIP). SEP events we call
  'impulsive', the traditional '3He-rich events,' are associated type III
  radio bursts, flares, and narrow CMEs, they selectively populate flux
  tubes that thread the localized source, and they are better fit to new
  particle-in-cell models of magnetic reconnection on open field lines
  as seen in jets. These models help explain the strong enhancements
  seen in heavy elements as a power (of 2 - 8) in the mass-to-charge
  ratio A/Q throughout the periodic table from He to Pb. A study of the
  temperature dependence of A/Q shows that the source plasma in impulsive
  SEP events must lie in the range of 2-4 MK to explain the pattern of
  abundances. This is much lower than the temperatures of &gt;10 MK seen
  on closed loops in flares.

---------------------------------------------------------
Title: Temperature of the Source Plasma for Impulsive Solar Energetic
    Particles
Authors: Reames, Donald V.; Cliver, Edward W.; Kahler, Stephen W.
2015SoPh..290.1761R    Altcode: 2015SoPh..tmp...81R; 2015arXiv150502741R
  The steep power-law dependence of element abundance enhancements
  on the mass-to-charge ratios [A /Q ] of the ions in impulsive solar
  energetic-particle (SEP) events causes these enhancements to reflect
  the temperature-dependent pattern of Q of the ions in the source
  plasma. We searched for SEP events from coronal plasma that is hotter
  or cooler than the limited region of 2.5 - 3.2 MK previously found to
  dominate 111 impulsive SEP events. Fifteen new events were found, four
  (three) originating in 2-MK (4-MK) plasma, but none from outside this
  temperature range. Although the impulsive SEP events are strongly
  associated with flares, this result indicates that these ions are
  not accelerated from flare-heated plasma, which can often exceed
  10 MK. Evidently the ions of 2 -20 MeVamu−<SUP>1</SUP> that we
  observe in space are accelerated from active-region plasma on open
  magnetic-field lines near the flare, but not from the closed loops of
  the flare. The power-law dependence of the abundance enhancements on
  A /Q of the ions is expected from theoretical models of acceleration
  from regions of magnetic reconnection.

---------------------------------------------------------
Title: Element abundances in solar energetic particles: two physical
    processes, two abundance patterns
Authors: Reames, Donald V.
2015arXiv150100610R    Altcode:
  Abundances of elements comprising solar energetic particles (SEPs) come
  with two very different patterns. Historically called "impulsive" and
  "gradual" events, they have been studied for 40 years, 20 years by the
  Wind spacecraft. Gradual SEP events measure coronal abundances. They
  are produced when shock waves, driven by coronal mass ejections (CMEs),
  accelerate the ambient coronal plasma; we discuss the average abundances
  of 21 elements that differ from corresponding solar photospheric
  abundances by a well-known dependence on the first ionization
  potential (FIP) of the element. The smaller impulsive ("3He-rich")
  SEP events are associated with magnetic reconnection involving open
  field lines from solar flares or jets that also eject plasma to produce
  accompanying CMEs. These events produce striking heavy-element abundance
  enhancements, relative to coronal abundances, by an average factor of
  3 at Ne, 9 at Fe, and 900 for elements with 76&lt;Z&lt;82. This is a
  strong, power-law dependence on A/Q with a ~3.6 power when Q values
  are determined at coronal temperatures near 3 MK. Small individual SEP
  events with the steepest enhancements (~6th power of A/Q), from ~2.5 MK
  plasma, are associated with B- and C-class X-ray flares, and with narrow
  (&lt;100 deg) CMEs. Enhancements in 3He/4He can be as large as those
  in heavy elements but are uncorrelated with them. However, events with
  3He/4He &gt; 0.1 are even more strongly associated with narrow, slow
  CMEs, cooler coronal plasma, and smaller X-ray flares. The impulsive
  SEP events do not come from hot flare plasma; they are accelerated
  early and/or on adjacent open field lines.

---------------------------------------------------------
Title: Variations in Abundance Enhancements in Impulsive Solar
    Energetic-Particle Events and Related CMEs and Flares
Authors: Reames, Donald V.; Cliver, Edward W.; Kahler, Stephen W.
2014SoPh..289.4675R    Altcode: 2014arXiv1407.7838R; 2014SoPh..tmp..121R
  We study event-to-event variations in the abundance enhancements of the
  elements He through Pb for Fe-rich impulsive solar energetic-particle
  (SEP) events, and their relationship with properties of associated
  coronal mass ejections (CMEs) and solar flares. Using a least-squares
  procedure we fit the power-law enhancement of element abundances as
  a function of their mass-to-charge ratio A/Q to determine both the
  power and the coronal temperature (which determines Q) in each of
  111 impulsive SEP events identified previously. Individual SEP events
  with the steepest element enhancements, e.g. ∼ (A/Q)<SUP>6</SUP>,
  tend to be smaller, lower-fluence events with steeper energy spectra
  that are associated with B- and C-class X-ray flares, with cooler (∼
  2.5 MK) coronal plasma, and with narrow (&lt; 100<SUP>∘</SUP>),
  slower (&lt; 700 km s<SUP>−1</SUP>) CMEs. On the other hand,
  higher-fluence SEP events have flatter energy spectra, less-dramatic
  heavy-element enhancements, e.g. ∼ (A/Q)<SUP>3</SUP>, and come from
  somewhat hotter coronal plasma (∼ 3.2 MK) associated with C-, M-,
  and even X-class X-ray flares and with wider CMEs. Enhancements in
  <SUP>3</SUP>He/<SUP>4</SUP>He are uncorrelated with those in heavy
  elements. However, events with <SUP>3</SUP>He/<SUP>4</SUP>He≥0.1
  are even more strongly associated with narrow, slow CMEs, with
  cooler coronal plasma, and with B- and C-class X-ray flares than
  are other Fe-rich impulsive SEP events with smaller enhancements of
  <SUP>3</SUP>He.

---------------------------------------------------------
Title: Abundance Enhancements in Impulsive Solar Energetic-Particle
    Events with Associated Coronal Mass Ejections
Authors: Reames, Donald V.; Cliver, Edward W.; Kahler, Stephen W.
2014SoPh..289.3817R    Altcode: 2014SoPh..tmp...86R; 2014arXiv1404.3322R
  We study the abundances of the elements He through Pb in Fe-rich
  impulsive solar energetic-particle (SEP) events with measurable
  abundances of ions with atomic number Z&gt;2 observed on the Wind
  spacecraft, and their relationship with coronal mass ejections
  (CMEs) observed by the Large Angle and Spectrometric Coronagraph
  (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). On an
  average the element abundances in these events are similar to coronal
  abundances at low Z but, for heavier elements, enhancements rise as
  a power law in the mass-to-charge ratio A/Q of the ions (at coronal
  temperatures of 2.5 - 3 MK) to a factor of 3 at Ne, 9 at Fe, and 900
  for 76≤Z≤82. Energy dependences of abundances are minimal in the 2
  - 15 MeV amu<SUP>−1</SUP> range. The 111 of these Fe-rich impulsive
  SEP events we found, between November 1994 and August 2013 using the
  Wind spacecraft, have a 69 % association rate with CMEs. The CMEs are
  narrow with a median width of 75<SUP>∘</SUP>, are characteristically
  from western longitudes on the Sun, and have a median speed of ≈
  600 km s<SUP>−1</SUP>. Nearly all SEP onsets occur within 1.5 -
  5 h of the CME onset. The faster (&gt; 700 km s<SUP>−1</SUP>),
  wider CMEs in our sample are related to SEPs with coronal abundances
  indicating hot coronal plasma with fully ionized He, C, N and O and
  moderate enhancements of heavier elements, relative to He, but slower
  (&lt; 700 km s<SUP>−1</SUP>), narrower CMEs emerge from cooler
  plasma where higher SEP mass-to-charge ratios, A/Q, yield much greater
  abundance enhancements, even for C/He and O/He. Apparently, the open
  magnetic-reconnection region where the impulsive SEPs are accelerated
  also provides the energy to drive out CME plasma, accounting for a
  strong, probably universal, impulsive SEP-CME association.

---------------------------------------------------------
Title: Correlation of Electron Path Lengths Observed in the Highly
    Wound Outer Region of Magnetic Clouds with the Slab Fraction of
    Magnetic Turbulence in the Dissipation Range
Authors: Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Shao, Xi;
   Wang, Linghua
2014ApJ...786..122T    Altcode:
  Three magnetic cloud events, in which solar impulsive electron
  events occurred in their outer region, are employed to investigate
  the difference of path lengths L <SUB>0eIII</SUB> traveled by
  non-relativistic electrons from their release site near the Sun to
  the observer at 1 AU, where L <SUB>0eIII</SUB> = v <SUB>l</SUB> ×
  (t <SUB>l</SUB> - t <SUB>III</SUB>), v <SUB>l</SUB> and t <SUB>l</SUB>
  being the velocity and arrival time of electrons in the lowest energy
  channel (~27 keV) of the Wind/3DP/SST sensor, respectively, and t
  <SUB>III</SUB> being the onset time of type III radio bursts. The
  deduced L <SUB>0eIII</SUB> value ranges from 1.3 to 3.3 AU. Since
  a negligible interplanetary scattering level can be seen in both L
  <SUB>0eIII</SUB> &gt; 3 AU and ~1.2 AU events, the difference in L
  <SUB>0eIII</SUB> could be linked to the turbulence geometry (slab or
  two-dimensional) in the solar wind. By using the Wind/MFI magnetic field
  data with a time resolution of 92 ms, we examine the turbulence geometry
  in the dissipation range. In our examination, ~6 minutes of sampled
  subintervals are used in order to improve time resolution. We have
  found that, in the transverse turbulence, the observed slab fraction is
  increased with an increasing L <SUB>0eIII</SUB> value, reaching ~100%
  in the L <SUB>0eIII</SUB> &gt; 3 AU event. Our observation implies
  that when only the slab spectral component exists, magnetic flux tubes
  (magnetic surfaces) are closed and regular for a very long distance
  along the transport route of particles.

---------------------------------------------------------
Title: Element Abundances in Solar Energetic Particles and the
    Solar Corona
Authors: Reames, Donald V.
2014SoPh..289..977R    Altcode: 2013arXiv1306.2246R
  This is a study of abundances of the elements He, C, N, O, Ne, Mg,
  Si, S, Ar, Ca, and Fe in solar energetic particles (SEPs) in the 2
  - 15 MeV amu<SUP>−1</SUP> region measured on the Wind spacecraft
  during 54 large SEP events occurring between November 1994 and June
  2012. The origin of most of the temporal and spatial variations
  in abundances of the heavier elements lies in rigidity-dependent
  scattering during transport of the particles away from the site of
  acceleration at shock waves driven out from the Sun by coronal mass
  ejections (CMEs). Variation in the abundance of Fe is correlated with
  the Fe spectral index, as expected from scattering theory but not
  previously noted. Clustering of Fe abundances during the "reservoir"
  period, late in SEP events, is also newly reported. Transport-induced
  enhancements in one region are balanced by depletions in another, thus,
  averaging over these variations produces SEP abundances that are energy
  independent, confirms previous SEP abundances in this energy region,
  and provides a credible measure of element abundances in the solar
  corona. These SEP-determined coronal abundances differ from those in
  the solar photosphere by a well-known function that depends upon the
  first ionization potential (FIP) or ionization time of the element.

---------------------------------------------------------
Title: Spatial Distribution of Solar Energetic Particles in the
    Inner Heliosphere
Authors: Reames, Donald V.; Ng, Chee K.; Tylka, Allan J.
2013SoPh..285..233R    Altcode: 2012SoPh..tmp..126R
  We study the spatial distribution of solar energetic particles (SEPs)
  throughout the inner heliosphere during six large SEP events from the
  period 1977 through 1979, as deduced from observations on the Helios 1
  and 2, IMP 7 and 8, ISEE 3, and Voyager 1 and 2 spacecraft. Evidence of
  intensity maxima associated with the expanding shock wave is commonly
  seen along its central and western flanks, although the region of peak
  acceleration or "nose" of the shock is sometimes highly localized
  in longitude. In one event (1 January 1978) a sharp peak in 20 -
  30 MeV proton intensities is seen more strongly by Voyager at ∼ 2
  AU than it is by spacecraft at nearby longitudes at ∼ 1 AU. Large
  spatial regions, or "reservoirs," often exist behind the shocks with
  spatially uniform SEP intensities and invariant spectra that decrease
  adiabatically with time as their containment volume expands. Reservoirs
  are seen to sweep past 0.3 AU and can extend out many AU. Boundaries
  of the reservoirs can vary with time and with particle velocity,
  rather than rigidity. In one case, a second shock wave from the Sun
  reaccelerates protons that retain the same hard spectrum as protons
  in the reservoir from the preceding SEP event. Thus reservoirs can
  provide not only seed particles but also a "seed spectrum" with a
  spectral shape that is unchanged by a weaker second shock.

---------------------------------------------------------
Title: The Two Sources of Solar Energetic Particles
Authors: Reames, Donald V.
2013SSRv..175...53R    Altcode: 2013arXiv1306.3608R; 2013SSRv..tmp....6R
  Evidence for two different physical mechanisms for acceleration of solar
  energetic particles (SEPs) arose 50 years ago with radio observations
  of type III bursts, produced by outward streaming electrons, and
  type II bursts from coronal and interplanetary shock waves. Since
  that time we have found that the former are related to "impulsive"
  SEP events from impulsive flares or jets. Here, resonant stochastic
  acceleration, related to magnetic reconnection involving open field
  lines, produces not only electrons but 1000-fold enhancements of
  <SUP>3</SUP>He/<SUP>4</SUP>He and of ( Z&gt;50)/O. Alternatively, in
  "gradual" SEP events, shock waves, driven out from the Sun by coronal
  mass ejections (CMEs), more democratically sample ion abundances that
  are even used to measure the coronal abundances of the elements. Gradual
  events produce by far the highest SEP intensities near Earth. Sometimes
  residual impulsive suprathermal ions contribute to the seed population
  for shock acceleration, complicating the abundance picture, but this
  process has now been modeled theoretically. Initially, impulsive events
  define a point source on the Sun, selectively filling few magnetic
  flux tubes, while gradual events show extensive acceleration that can
  fill half of the inner heliosphere, beginning when the shock reaches
  ∼2 solar radii. Shock acceleration occurs as ions are scattered
  back and forth across the shock by resonant Alfvén waves amplified
  by the accelerated protons themselves as they stream away. These
  waves also can produce a streaming-limited maximum SEP intensity and
  plateau region upstream of the shock. Behind the shock lies the large
  expanse of the "reservoir", a spatially extensive trapped volume of
  uniform SEP intensities with invariant energy-spectral shapes where
  overall intensities decrease with time as the enclosing "magnetic
  bottle" expands adiabatically. These reservoirs now explain the slow
  intensity decrease that defines gradual events and was once erroneously
  attributed solely to slow outward diffusion of the particles. At
  times the reservoir from one event can contribute its abundances and
  even its spectra as a seed population for acceleration by a second
  CME-driven shock wave. Confinement of particles to magnetic flux tubes
  that thread their source early in events is balanced at late times by
  slow velocity-dependent migration through a tangled network produced
  by field-line random walk that is probed by SEPs from both impulsive
  and gradual events and even by anomalous cosmic rays from the outer
  heliosphere. As a practical consequence, high-energy protons from
  gradual SEP events can be a significant radiation hazard to astronauts
  and equipment in space and to the passengers of high-altitude aircraft
  flying polar routes.

---------------------------------------------------------
Title: Comparison between Path Lengths Traveled by Solar Electrons
    and Ions in Ground-Level Enhancement Events
Authors: Tan, Lun C.; Malandraki, Olga E.; Reames, Donald V.; Ng,
   Chee K.; Wang, Linghua; Patsou, Ioanna; Papaioannou, Athanasios
2013ApJ...768...68T    Altcode:
  We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT
  ion data to investigate the path length difference between solar
  electrons and ions in the ground-level enhancement (GLE) events in
  solar cycle 23. Assuming that the onset time of metric type II or
  decameter-hectometric (DH) type III radio bursts is the solar release
  time of non-relativistic electrons, we have found that within an
  error range of ±10% the deduced path length of low-energy (~27 keV)
  electrons from their release site near the Sun to the 1 AU observer is
  consistent with the ion path length deduced by Reames from the onset
  time analysis. In addition, the solar longitude distribution and IMF
  topology of the GLE events examined are in favor of the coronal mass
  ejection-driven shock acceleration origin of observed non-relativistic
  electrons. We have also found an increase of electron path lengths with
  increasing electron energies. The increasing rate of path lengths is
  correlated with the pitch angle distribution (PAD) of peak electron
  intensities locally measured, with a higher rate corresponding to a
  broader PAD. The correlation indicates that the path length enhancement
  is due to the interplanetary scattering experienced by first arriving
  electrons. The observed path length consistency implies that the maximum
  stable time of magnetic flux tubes, along which particles transport,
  could reach 4.8 hr.

---------------------------------------------------------
Title: Modeling Multi-Spacecraft Observation to Understand SEP Origin,
    Acceleration, and Transport and to Infer their Radial, Latitudinal
    and Longitudinal Variations
Authors: Ng, C. K.; Reames, D. V.; Rouillard, A. P.; Tan, L. C.;
   Tylka, A. J.; von Rosenvinge, T. T.
2012AGUFMSH23B..01N    Altcode:
  We present interesting examples of our study of the spatial
  distribution of SEPs inferred from observations on the Helios 1 and
  2, IMP7 and 8, ISEE3, and Voyager 1 and 2 spacecraft in the time
  interval 1977-1979. The study is on the concurrent observation of
  protons in three energy bins from a few MeV to &gt;100 MeV and ~
  6 MeV electrons, spanning heliocentric distances from 0.3 AU to
  several AU and a wide longitude range. We take advantage of the unique
  spacecraft configuration in each case to infer the implications of the
  multi-point observations on the origin, acceleration, and transport of
  SEPs, in particular as regards "reservoir" formation, perpendicular
  transport, and relation to CME-driven shocks. For the recent 2011
  March 21 event, we present model fits to the SEP intensity time
  profiles and energy spectra observed by STEREO-A and many spacecraft
  at Earth's L1 Lagrangian point. We also present the evolution of
  the SEP intensity radial profiles on field lines leading to STEREO
  and L1 as predicted by the focused transport model, which includes
  self-consistent SEP-amplified Alfvén waves. The radial dependence
  of the maximum intensity and fluence at various SEP energies from the
  same fitted model at STEREO A and L1 will be presented. This work is
  supported in part by NASA grants NNX09AU98G, NNG11PV53P, NNX08AQ02G,
  and NNH09AK79I. Work at GSFC is funded by NASA.

---------------------------------------------------------
Title: Particle Energy Spectra at Traveling Interplanetary Shock Waves
Authors: Reames, Donald V.
2012ApJ...757...93R    Altcode:
  We have searched for evidence of significant shock acceleration of
  He ions of ~1-10 MeV amu<SUP>-1</SUP> in situ at 258 interplanetary
  traveling shock waves observed by the Wind spacecraft. We find that the
  probability of observing significant acceleration, and the particle
  intensity observed, depends strongly upon the shock speed and less
  strongly upon the shock compression ratio. For most of the 39 fast
  shocks with significant acceleration, the observed spectral index
  agrees with either that calculated from the shock compression ratio or
  with the spectral index of the upstream background, when the latter
  spectrum is harder, as expected from diffusive shock theory. In many
  events the spectra are observed to roll downward at higher energies,
  as expected from Ellison-Ramaty and from Lee shock-acceleration
  theories. The dearth of acceleration at ~85% of the shocks is explained
  by (1) a low shock speed, (2) a low shock compression ratio, and (3)
  a low value of the shock-normal angle with the magnetic field, which
  may cause the energy spectra that roll downward at energies below our
  observational threshold. Quasi-parallel shock waves are rarely able to
  produce measurable acceleration at 1 AU. The dependence of intensity on
  shock speed, seen here at local shocks, mirrors the dependence found
  previously for the peak intensities in large solar energetic-particle
  events upon speeds of the associated coronal mass ejections which
  drive the shocks.

---------------------------------------------------------
Title: Composition of the Solar Corona, Solar Wind, and Solar
    Energetic Particles
Authors: Schmelz, J. T.; Reames, D. V.; von Steiger, R.; Basu, S.
2012ApJ...755...33S    Altcode:
  Along with temperature and density, the elemental abundance is a basic
  parameter required by astronomers to understand and model any physical
  system. The abundances of the solar corona are known to differ from
  those of the solar photosphere via a mechanism related to the first
  ionization potential of the element, but the normalization of these
  values with respect to hydrogen is challenging. Here, we show that the
  values used by solar physicists for over a decade and currently referred
  to as the "coronal abundances" do not agree with the data themselves. As
  a result, recent analysis and interpretation of solar data involving
  coronal abundances may need to be revised. We use observations from
  coronal spectroscopy, the solar wind, and solar energetic particles
  as well as the latest abundances of the solar photosphere to establish
  a new set of abundances that reflect our current understanding of the
  coronal plasma.

---------------------------------------------------------
Title: The Longitudinal Properties of a Solar Energetic Particle
    Event Investigated Using Modern Solar Imaging
Authors: Rouillard, A. P.; Sheeley, N. R.; Tylka, A.; Vourlidas,
   A.; Ng, C. K.; Rakowski, C.; Cohen, C. M. S.; Mewaldt, R. A.; Mason,
   G. M.; Reames, D.; Savani, N. P.; StCyr, O. C.; Szabo, A.
2012ApJ...752...44R    Altcode:
  We use combined high-cadence, high-resolution, and multi-point imaging
  by the Solar-Terrestrial Relations Observatory (STEREO) and the Solar
  and Heliospheric Observatory to investigate the hour-long eruption of a
  fast and wide coronal mass ejection (CME) on 2011 March 21 when the twin
  STEREO spacecraft were located beyond the solar limbs. We analyze the
  relation between the eruption of the CME, the evolution of an Extreme
  Ultraviolet (EUV) wave, and the onset of a solar energetic particle
  (SEP) event measured in situ by the STEREO and near-Earth orbiting
  spacecraft. Combined ultraviolet and white-light images of the lower
  corona reveal that in an initial CME lateral "expansion phase," the
  EUV disturbance tracks the laterally expanding flanks of the CME,
  both moving parallel to the solar surface with speeds of ~450 km
  s<SUP>-1</SUP>. When the lateral expansion of the ejecta ceases, the
  EUV disturbance carries on propagating parallel to the solar surface
  but devolves rapidly into a less coherent structure. Multi-point
  tracking of the CME leading edge and the effects of the launched
  compression waves (e.g., pushed streamers) give anti-sunward speeds
  that initially exceed 900 km s<SUP>-1</SUP> at all measured position
  angles. We combine our analysis of ultraviolet and white-light images
  with a comprehensive study of the velocity dispersion of energetic
  particles measured in situ by particle detectors located at STEREO-A
  (STA) and first Lagrange point (L1), to demonstrate that the delayed
  solar particle release times at STA and L1 are consistent with the
  time required (30-40 minutes) for the CME to perturb the corona over a
  wide range of longitudes. This study finds an association between the
  longitudinal extent of the perturbed corona (in EUV and white light)
  and the longitudinal extent of the SEP event in the heliosphere.

---------------------------------------------------------
Title: Use of Incident and Reflected Solar Particle Beams to Trace
    the Topology of Magnetic Clouds
Authors: Tan, Lun C.; Malandraki, Olga E.; Reames, Donald V.; Ng,
   Chee K.; Wang, Linghua; Dorrian, Gareth
2012ApJ...750..146T    Altcode:
  Occasionally, large solar energetic particle (SEP) events occur
  inside magnetic clouds (MCs). In this work, the onset time analysis,
  the peak intensity analysis, and the decay phase analysis of SEPs are
  used to investigate two large SEP events inside MCs: the 1998 May 2
  and 2002 April 21 events. The onset time analysis of non-relativistic
  electrons and ~MeV nucleon<SUP>-1</SUP> heavy ions shows the stability
  of the magnetic loop structure during a period of a few hours in the
  events examined. The joint analysis of pitch-angle distributions and
  peak intensities of electrons exhibits that, depending on the particle
  pitch angle observed at 1 AU, in the April event the reflection point of
  particles may be distributed along a wide spatial range, implying that
  the magnetic loop is a magnetic bottle connected to the Sun with both
  legs. In contrast, in the May event particle reflection occurs abruptly
  at the magnetic mirror formed by a compressed field enhancement behind
  the interplanetary shock, consistent with its open field line topology.

---------------------------------------------------------
Title: The Two Sources of Solar Energetic Particles
Authors: Reames, Donald V.
2012AAS...22011201R    Altcode:
  The identification of two different physical mechanisms for acceleration
  of solar energetic particles (SEPs) began nearly 50 years ago with the
  radio observations of type III bursts produced by outward streaming
  electrons and type II bursts from coronal (and interplanetary) shock
  waves. Since that time we have found that the former are related
  to “impulsive” SEP events from flares or jets where resonant
  stochastic acceleration, probably related to magnetic reconnection,
  can produce 1000-fold enhancements of <SUP>3</SUP>He/<SUP>4</SUP>He
  and of (Z&gt;50)/O, for example, while the latter “gradual” SEP
  events sample ion abundances democratically and are used to measure
  the coronal abundances of the elements. Sometimes, unfortunately,
  residual impulsive suprathermal ions can also contribute to the seed
  population for shock acceleration, complicating the picture, but
  this process can now be modeled theoretically. Initially, impulsive
  events behave like a point source on the Sun, while multi-spacecraft
  observations of gradual events show extensive acceleration that can span
  half of the inner heliosphere, beginning when the shock reaches 2 solar
  radii. Acceleration occurs as ions are scattered back and forth across
  the shock by proton-generated resonant Alfven waves. These waves also
  define a streaming-limited maximum intensity or plateau region prior to
  arrival of the shock. Behind the shock lies an extensive “reservoir”
  region of spatially uniform SEP intensity that decreases with time as
  the “magnetic bottle” enclosing it expands.

---------------------------------------------------------
Title: Solar energetic particles: Shock acceleration and transport
    through self-amplified waves
Authors: Ng, Chee K.; Reames, Donald V.; Tylka, Allan J.
2012AIPC.1436..212N    Altcode:
  This article reviews our work on the powerful influence of
  self-amplified Alfvén waves on the interplanetary (IP) transport
  and shock acceleration of solar energetic particles (SEPs). In large
  gradual events, a huge number of shock-accelerated protons stream
  through the IPmediumand amplify ambient Alfvén waves by orders of
  magnitude. Nonlinear models that take account of selfamplified waves
  semi-quantitatively explain many intriguing SEP observations at 1
  AU: (a) upper limits to early SEP intensities, (b) flat intensity
  energy spectra up to ~ 30 MeV/amu before shock arrival, and (c)
  complex temporal, energy, and event-to-event variations of elemental
  abundances. Streaming limit complicates estimation of the number and
  energy of SEPs accelerated in a solar event but provides a safety
  window for astronauts to seek shelter before a potential hazardous
  intensity rise at shock passage. Self-amplified waves help bootstrap
  shock acceleration and the high near-shock SEP intensity predicted at
  &lt;= 20rsolar. is relevant to inner heliospheric space missions.

---------------------------------------------------------
Title: Comparative Modeling of 2011 March 21 SEP Event at STEREO-A
    and Earth's L1
Authors: Ng, C. K.; Rouillard, A. P.; Reames, D. V.; Tylka, A. J.;
   von Rosenvinge, T. T.
2011AGUFMSH34A..03N    Altcode:
  The 2011 March 21 solar energetic particle (SEP) event is strong at
  STEREO-A and weak at Earth L1 Lagrangian point, with quite different
  intensity time histories and energy spectra. Details of the SEP,
  flare, CME and in situ plasma and field observations are presented by
  Rouillard et al. at this conference. Here we report on our modeling
  of the transport of multi-species SEPs coupled to Alfvén-wave
  amplification by streaming energetic protons. The pre-shock proton
  intensity observed by IMPACT at STEREO-A is averaged over 21 hours after
  the fast rise. This "plateau" intensity spectrum flattens below 2 MeV
  at a few 100 pfu, where 1 pfu = protons/(cm^2 s sr MeV). By contrast,
  at 90 deg to the east, spacecraft at L1 observe a slow and small
  intensity rise with power-law spectra while, 90 deg even further east,
  STEREO-B observes no significant increase. Modeling SEP transport in
  this event requires quite different energy- and time-dependent release
  of accelerated SEPs at the traveling shock on the different field lines
  leading to STEREO-A and L1. We infer that the shock accelerated a large
  number of &gt; 3 MeV protons on field lines leading to STEREO-A. The
  numerous protons generate strong wave growth, which limits the proton
  intensity and flattens the energy spectrum at &lt; 2 MeV. In contrast,
  on field lines leading to L1, the shock accelerated far fewer energetic
  protons, which amplified few waves. With few self-amplified waves to
  "trap" the SEPs near the shock, the proton intensity rises toward
  low energy as a power law. This finding from observations at two
  widely separated spacecraft in the same SEP event is consistent with
  the conclusion of our comparative modeling of the weak 1998 May 2
  and strong 2003 October 28 ground level events. Together, these four
  event observations show a progression from weak shock acceleration and
  power-law intensity spectrum at ~ 1 AU to strong shock acceleration
  and a flattened energy spectrum. As shock acceleration to proton
  intensity &gt; 100 pfu increases its range from &lt; 7 MeV to &lt;
  50 MeV going from the 2011 March 21 event at STEREO-A to the 2003 Oct
  28 event at L1, the energy of spectral flattening rises from 2 MeV
  to 20 MeV. We will also present fitting of the observed intensity and
  spectra of minor ions. We thank Glenn Mason for his advice on ACE/ULEIS
  observations. Work at GSFC is funded by NASA. Work of APR was partly
  funded by NASA contracts NNX11AD40G-45527 and NNXIOAT06G. Work of
  CKN, DVR, and AJT are supported in part by NASA grants NNX09AU98G,
  NNX08AQ02G, and NNH09AK79I, respectively.

---------------------------------------------------------
Title: What Causes Scatter-free Transport of Non-relativistic Solar
    Electrons?
Authors: Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Shao, Xi;
   Wang, Linghua
2011ApJ...728..133T    Altcode:
  We have examined the cause of the scatter-free transport of
  non-relativistic solar electrons. Electron scatter-free transport
  events are compared with the diffusive transport event. The emphasis
  of our examination is on the energy dependence of electron angular
  distributions and the steepening of interplanetary magnetic field
  (IMF) power spectral densities (PSDs). Near and above the proton
  gyrofrequency, the effects of both R-mode (whistler) and L-mode
  (electromagnetic ion cyclotron, EMIC) waves need to be taken into
  account separately. The PSD spectral steepening due to the EMIC
  wave damping by solar-wind thermal ions becomes essential. In a
  fast-rise-fast-decay impulsive electron event we have observed such
  steepening, which significantly reduces PSD levels at frequencies
  above the proton gyrofrequency. The spectral steepening thus produced
  favors the occurrence of scatter-free transport of low-energy
  electrons. Consequently, within the Wind/3D Plasma and Energetic
  Particle Instrument/Silicon Semiconductor Telescope measured energy
  range (~25-500 keV), there appears to be an electron energy window,
  across which the scatter-free transport of lower energy electrons would
  change to the diffusive transport of higher energy electrons. We have
  observed such a change and found it is correlated with the occurrence
  of broken power-law spectra of electrons. Thus the connection between
  the transition from diffusive to scatter-free electron transport
  and the concurrent transition from high to low IMF PSD levels with
  corresponding breaks in the electron power-law energy spectrum and
  PSD spectrum has been recognized.

---------------------------------------------------------
Title: Exploring with Multiple Spacecraft the Scene of the Traveling
    Strong Shock and its Driver
Authors: Berdichevsky, D. B.; Wu, C.; Reames, D. V.; MacDowall, R. J.;
   Farrugia, C. J.
2010AGUFMSH31D..07B    Altcode:
  We explore the global morphology of the transient shock generated by
  a fast solar ejection using multispacecraft observations, at wide
  heliographic longitudes. We consider the gradual solar energetic
  particle [SEP] events starting on 24 September 1977, 1 January and 23
  September 1978, 26 March and 24 April 1979. To do this we use the solar
  wind parameters at each spacecraft location at the time of passage of
  the shock. In most cases data coverage at each shock passage enable us
  to estimate the shock normal and its velocity relative to the upstream
  solar wind. We remote sense the source of type II radio bursts, when
  available. Here, for each case, at the nearest in-situ location to the
  shocks nose, we present the findings; (1) the presence of unusual fast
  and massive driver, within two hours or less of the shock passage and
  the preliminary analysis of their unique plasma properties available,
  (2) with regard to the driven shock, with the help of modeling the
  inference of its morphological nature; (3) Further, the finding that
  each one of these five shocks has a surface portion moving at least
  more than 300 km/s faster than the upstream solar wind, enabling strong
  shock conditions, as we know from the Earth's bow shock, which are
  identified over distances from the Sun of 0.4 to 1.0 AU. Finally we
  show that the shock with the most extended and fastest surface portion
  (&gt; 1600 km/s) is the one which produced the largest energetic proton
  flux in each energy channel (&lt; 60 MeV), at each location within an
  extension of close to 180° in longitude. The shock with the smallest
  increase in energetic particle intensities, which was limited to an
  extension in longitude of less than 120°, had its fastest surface
  portion moving at possibly less than 900 km/s.

---------------------------------------------------------
Title: Streaming Limit: New Observations and Model Results
Authors: Ng, C. K.; Reames, D. V.; Tylka, A. J.
2010AGUFMSH41C..06N    Altcode:
  Solar energetic particle intensities at 1 AU often show an early
  temporal plateau where the intensity is limited. This early intensity
  limit may provide a valuable time window for astronauts to seek
  shelter before large shock-associated intensity increase (if any). The
  Ng and Reames (1994) time-dependent model of SEP transport through
  self-amplified Alfvén waves predicts a maximum proton intensity of
  ~ 250 particles /(cm^2 s str MeV) at ~ 1 MeV, in agreement within a
  factor of 2 with the observational survey by Reames and Ng (1998). In
  fact, streaming-limited intensity is implicit in the steady-state
  shock-acceleration solution of Bell (1978) and Lee (1983). Further
  studies on the effect of self-amplified waves on SEP intensity spectra
  have been made by Ng, Reames and Tylka (2003), Vanio (2003), and Lee
  (2005). Intensities exceeding the Ng and Reames (1994) limit have been
  reported (e.g., Lario et al. 2009). We present new observations of
  multi-species SEP spectra at the temporal intensity plateau. We also
  present new theoretical results on how the streaming limit depends on
  ion species and energy, ambient wave intensity spectrum, Alfvén speed,
  solar-wind speed, shock speed, and the presence of interplanetary shocks
  and interaction regions. Among the new interesting observations is the
  strong suppression of ion intensities near 1 MeV/amu in events that
  have high 10-100 MeV proton intensity. New modeling results confirm
  that this is due to these low-energy ions being strongly scattered at
  small pitch angles by waves amplified by 10-100 MeV protons at large
  pitch angles. As the high-energy protons travel upstream and scatter
  from small to large pitch-angles, they simultaneously amplify waves en
  route over a range of wavenumbers, including those that are resonant
  with low-energy protons. Thus, wave amplification by streaming protons
  and the pitch-angle dependence of the wave-particle resonance condition
  are essential factors in understanding the limiting behavior. We thank
  Glenn Mason for his advice on ACE/ULEIS observations. Work by CKN, DVR,
  and AJT are supported in part by NASA grants NNX09AU98G, NNX08AQ02G,
  and NNH09AK79I, respectively.

---------------------------------------------------------
Title: Streaming-limited Intensities of Solar Energetic Particles
    on the Intensity Plateau
Authors: Reames, Donald V.; Ng, Chee K.
2010ApJ...723.1286R    Altcode:
  We examine the energy spectra of H, He, O, and Fe ions on the temporal
  intensity plateau region in large solar energetic-particle (SEP) events,
  where intensities may be ”streaming limited.” Upstream of shock waves
  near the Sun, equilibrium may occur when outwardly streaming protons
  amplify resonant Alfvén waves that then scatter subsequent protons
  sufficiently to reduce the streaming. In the largest SEP events, the
  so-called ground-level events (GLEs), we find proton energy spectra that
  are peaked near ~10 MeV with the energy of similar peaks decreasing for
  heavier ions and for smaller events. These spectra contrast sharply with
  spectra near the time of shock passage which rise monotonically above
  the plateau spectra with decreasing energy. We suggest that strong
  suppression of upstream ion intensities near ~1 MeV amu<SUP>-1</SUP>
  on the plateau occurs when those ions resonate with waves amplified
  earlier by streaming protons of ~10 MeV and above. GLEs with much
  lower intensities of 10-100 MeV protons on the plateau show spectra
  of ions that rise monotonically toward low energies with no peaking
  and no suppression of low-energy ions. Wave amplification by streaming
  protons and the pitch-angle dependence of the resonance condition are
  essential factors in our understanding of the limiting behavior.

---------------------------------------------------------
Title: A Multi-spacecraft View of Solar-energetic-particle Onsets
    in the 1977 November 22 Event
Authors: Reames, Donald V.; Lal, Nand
2010ApJ...723..550R    Altcode:
  We examine the onset timing of solar energetic particles in the large
  ground-level event (GLE) of 1977 November 22 as observed from six
  spacecraft at four distinct solar longitudes. In most cases, it was
  possible to use velocity dispersion of the energetic protons to fix
  the solar particle release (SPR) time and the path length traveled
  by the initial particle burst from each solar longitude. We find
  that the SPR times do depend upon solar longitude, being earliest for
  spacecraft that are magnetically well connected to the source region,
  and later for longitudes on the flanks of the outward-driven shock
  wave. The earliest SPR time occurs well after peak photon emission
  from the associated Hα flare. These observations are consistent with
  conclusions derived from single-longitude observations of different
  GLE events. They are consistent with shock acceleration over a broad
  spatial region with heights rising, and/or shock speeds falling,
  for longitudes on the flanks of the shock.

---------------------------------------------------------
Title: Unusual time histories of galactic and anomalous cosmic rays
    at 1 AU over the deep solar minimum of cycle 23/24
Authors: McDonald, Frank B.; Webber, William R.; Reames, Donald V.
2010GeoRL..3718101M    Altcode:
  The unusually quiet Sun of the cycle 23/24 solar minimum (that ended
  in December, 2009) has resulted in lower values of the interplanetary
  magnetic field and a slower approach of the tilt angle of the
  heliospheric current sheet toward the solar equator than has been
  observed for recent solar minima. As a result of these changes, the
  time-histories of galactic and anomalous cosmic rays over this period
  are very different from those of recent minima at the same phase of the
  heliomagnetic cycle. Since ∼2005.6 there has been an on-going increase
  in cosmic-ray intensity (except for one brief transient decrease)
  that lasted for 4.4 years. The relative rigidity dependences of these
  increases compared to previous cycles are complex and should provide
  insight into the role of various solar and interplanetary phenomena
  in the modulation process. The largest increase occurs in the nominal
  “cross-over energy” region (where the modulation is essentially
  the same for each minimum of the two past 22 year heliomagnetic cycles)
  which extends from ∼200 MeV/n to &gt;500 MeV/n.

---------------------------------------------------------
Title: Remote Sensing of Magnetic-Cloud Topology
Authors: Reames, Donald V.
2010SoPh..265..187R    Altcode: 2010SoPh..tmp...39R
  We investigate the topology of magnetic clouds using energetic particles
  from a variety of sources outside the clouds as probes to remotely
  sense the interconnections of the magnetic field. We find that only a
  small percentage of field lines in magnetic clouds are truly closed
  directly to the Sun, so as to exclude particles from an external
  source. Field lines that are open to the outer heliosphere must be
  mixed with closed field lines on a fine spatial scale in the clouds
  to explain the simultaneous observation of anomalous cosmic rays from
  the outer heliosphere and of counter-streaming suprathermal electrons
  from the corona. The results of this paper show that, given sufficient
  time, particles accelerated at shock waves outside magnetic clouds
  have access to the interior and to a wide region of solar longitude
  in interplanetary space surrounding the clouds.

---------------------------------------------------------
Title: The Deep Solar Minimum of Cycle 23/24: A New Look at the
    Heliosphere and Solar Modulation
Authors: McDonald, F. B.; Webber, Bill; Reames, Donald; Stone, E. C.;
   Cummings, A. C.; Heikkila, B. C.; Lal, N.
2010cosp...38.1654M    Altcode: 2010cosp.meet.1654M
  The Deep Solar Minimum of Cycle 23/24 (that apparently ended in
  December, 2009) resulted in lower values of the interplanetary magnetic
  field and a slower approach of the tilt angle of the heliospheric
  current sheet to the lowest value observed in recent solar minima. As
  a result of these unusual interplanetary conditions the time-histories
  and intensities of galactic and anomalous cosmic rays over this period
  are very different from those of previous solar minima at the same
  phase of the heliomagnetic cycle -for example 200 MeV/n GCR He are 30

---------------------------------------------------------
Title: Time Dependent Composition in Large Solar Energetic Particle
    Events
Authors: Cohen, C. M.; Tylka, A. J.; Mason, G. M.; Mewaldt, R. A.;
   Reames, D. V.
2009AGUFMSH22A..01C    Altcode:
  Temporal evolution in elemental abundance ratios in large solar
  energetic particle (SEP) events has proven to be a powerful tool
  in investigating interplanetary particle transport processes. In
  particular, the Fe/O abundance measured at a common energy/nucleon (E/M)
  typically decreases as a function of time in large SEP events. However,
  it has been found that for some events originating in the western
  solar hemisphere this time dependence lessens when the abundance
  ratio is calculated using O measured at a higher E/M than Fe. Such
  behavior may be the result of rigidity-dependent scattering processes
  in the interplanetary medium. In this work, we examine the time
  dependence of the Fe/O abundance in several large SEP events using
  ratios calculated at many common and different E/M values between
  0.3 and 80 MeV/nucleon. We will discuss the implications regarding
  rigidity-dependent effects. In addition, we will present analysis of the
  behavior of the He/H abundance where the charge states (and therefore,
  the rigidities) of the elements are known.

---------------------------------------------------------
Title: The Unusual Time History of Galactic an Anomalous Cosmic Rays
    in the Heliosphere over the Deep Solar Minimum of Cycle 23/24
Authors: McDonald, F. B.; Webber, W. R.; Reames, D. V.; Stone, E. C.;
   Cummings, A. C.; Heikkila, B. C.; Lal, N.
2009AGUFM.U34A..07M    Altcode:
  The continuing Quiet Sun of the cycle 23/24 solar minimum has resulted
  in cosmic ray intensity time-histories at 1 AU that are very different
  from those of the 1965 and 1987 solar minima at the same phase of
  the 22 year heliomagnetic cycle. Instead of the sharp intensity peak
  of these earlier cycles, the cosmic ray intensity displays a broad
  plateau followed by an on-going increase that has now lasted for 1.4
  years. Over the cycle 19 and 21 solar minima there was a suppression
  of the cosmic ray intensity at rigidities below 0.5 GV while at neutron
  monitor energies (72 GeV) the intensity was 3-5% higher than in qA&gt;0
  cycle. For cycle 23/24 in 2009.5 the 200 MeV/n He intensity is 25%
  higher than its 1987 and the neutron monitor data from the North-West
  University 4 Station Network is within 1.5% of those of 1987. However,
  the intensity of 13.5 MeV/n ACR oxygen intensity is a factor of 2
  below its 1987 level. These complex spectral differences are clearly
  caused by the decrease in strength of the interplanetary field below
  the level of previous minima and the relatively high inclination of
  the heliospheric current sheet that persisted until ~ 2009.3 before
  decreasing to lower values. In the heliosheath cosmic ray data from
  Voyager 1 and 2 are showing significant increases that reflect the
  changes that are occurring in the solar wind and magnetic fields in
  the distant heliosphere. The relative behavior of 10 MeV GCR electrons
  and 150-380 MeV/n He suggest these particles follow a different route
  entering the heliosphere than the higher energy cosmic rays. At this
  time the deep solar minimum is continuing so further changes in the
  cosmic ray time histories can be expected.

---------------------------------------------------------
Title: Solar Energetic-Particle Release Times in Historic Ground-Level
    Events
Authors: Reames, Donald V.
2009ApJ...706..844R    Altcode:
  Ground-level events (GLEs) are large solar energetic-particle events
  with sufficiently hard spectra for GeV protons to be detected by neutron
  monitors at ground level. For each of 30 well-observed historic GLEs
  from four solar cycles, extending back to 1973, I have plotted onset
  times versus velocity<SUP>-1</SUP> for particles observed on the IMP-7
  and 8, ISEE-3, Wind, and GOES spacecraft and by neutron monitors. A
  linear fit on such a plot for each GLE determines the initial solar
  particle release (SPR) time, as the intercept, and the magnetic path
  length traversed, as the slope, of the fitted line. Magnetic path
  lengths and SPR times are well determined by the fits and cannot be
  used as adjustable parameters to make particle and photon emission
  times coincide. SPR times follow the onsets of shock-induced type
  II radio bursts and the coronal height of the coronal mass ejection
  (CME)-driven shock at SPR time can be determined for GLEs spanning an
  interval of solar longitude of ~140 deg. For a given GLE, all particle
  species and energies diverge from a single SPR point at a given coronal
  height and footpoint longitude of the field line to the Earth. These
  heights tend to increase with longitudinal distance away from the
  source, a pattern expected for shock acceleration. Acceleration for
  magnetically well-connected large GLEs begins at ~2 solar radii, in
  contrast to non-GLEs that have been found to be strongly associated with
  shocks above ~3 solar radii. The higher densities and magnetic field
  strengths at lower altitudes may be responsible for the acceleration
  of higher-energy particles in GLEs, while those GLEs that begin above
  3R <SUB>S</SUB> may compensate by having higher shock speeds. These
  results support the joint dependence of maximum particle energy on
  magnetic field strength, injected particle density, and shock speed,
  all predicted theoretically.

---------------------------------------------------------
Title: Anomalous Cosmic Rays as Probes of Magnetic Clouds
Authors: Reames, D. V.; Kahler, S. W.; Tylka, A. J.
2009ApJ...700L.196R    Altcode:
  We report, for the first time, the observation near the Earth of
  anomalous cosmic ray (ACR) particles throughout the interiors of
  interplanetary magnetic clouds (MCs) at the same intensity as outside
  the MCs. ACRs, accelerated in the outer heliosphere, have unique
  elemental abundances making their identity unambiguous as they probe
  these clouds from the outside. Thus, MCs, carried out from the Sun
  by coronal mass ejections (CMEs), are seen to contain no structures
  that are magnetically closed to the penetration of ions with energies
  above a few MeV amu<SUP>-1</SUP>. As the MCs expand outward, they
  must fill their increasing volume with ACRs dynamically, to the same
  degree as neighboring "open" field lines. These observations cast
  doubt on conventional ideas about the closed field topologies of
  MCs and the cross-field transport of energetic particles. The ACR
  observations conflict with some reports of significant exclusion
  from MCs of solar energetic particles (SEPs) of comparable energy
  and rigidity. A process that allows cross-field transport of ACRs may
  also allow similar transport of SEPs late in events, causing the large
  spatial extent and uniformity of SEPs in "invariant spectral regions"
  extending far behind CME-driven shock waves.

---------------------------------------------------------
Title: A Comparison of Elemental Abundance Ratios in Sep Events in
    Fast and Slow Solar Wind Regions
Authors: Kahler, S. W.; Tylka, A. J.; Reames, D. V.
2009ApJ...701..561K    Altcode:
  The solar energetic (E &gt; 1 MeV nucleon<SUP>-1</SUP>) particles
  (SEPs) observed in gradual events at 1 AU are assumed to be accelerated
  by coronal/interplanetary shocks from ambient thermal or suprathermal
  seed particles. If so, then the elemental abundances of SEPs produced
  in different solar wind (SW) stream types (transient, fast, and
  slow) might be systematically distinguished from each other. We
  look for these differences in SEP energy spectra and in elemental
  abundance ratios (including Mg/Ne and Fe/C, which compare low/high
  first ionization potential elements), in a large number of SEP time
  intervals over the past solar cycle. The SW regions are characterized
  by the three-component stream classification of Richardson et al. Our
  survey shows no significant compositional or energy spectral differences
  in the 5-10 MeV nucleon<SUP>-1</SUP> range for SEP events of different
  SW stream types. This result extends the earlier finding that SEP events
  are observed frequently in fast SW streams, although their higher Alfven
  and SW flow speeds should constrain SEP production by coronal mass
  ejection-driven shocks in those regions. We discuss the implications
  of our results for shock seed populations and cross-field propagation.

---------------------------------------------------------
Title: Observational Evidence on the Presence of an Outer Reflecting
    Boundary in Solar Energetic Particle Events
Authors: Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Saloniemi,
   Oskari; Wang, Linghua
2009ApJ...701.1753T    Altcode:
  We have focused primarily on the 2001 September 24 solar energetic
  particle (SEP) event to verify previous indications of the presence
  of an outer reflecting boundary of SEPs. By using energetic electron
  and ion data obtained from multi-spacecraft observations, we have
  identified a collimated particle beam consisting of reflected particles
  returning from an outer boundary. The peak of reflected particles
  appears before the arrival of particles at 90° pitch angle. In
  addition, an onset time analysis is carried out in order to determine
  parameters characterizing the boundary. Our analysis suggests that the
  presence of a counter-streaming particle beam with a deep depression
  at ~90° pitch angle during the onset phase is evidence for a nearby
  reflecting boundary. We have compared this property in the SEP events
  of 2002 April 21 and August 24. A reflecting boundary that blocks a
  flux tube is important in space weather forecasting since it can cause
  the "reservoir" effect that may enhance the intensity and duration of
  high-energy particles.

---------------------------------------------------------
Title: The Solar Energetic Particle Event of 14 December 2006
Authors: von Rosenvinge, T. T.; Richardson, I. G.; Reames, D. V.;
   Cohen, C. M. S.; Cummings, A. C.; Leske, R. A.; Mewaldt, R. A.; Stone,
   E. C.; Wiedenbeck, M. E.
2009SoPh..256..443V    Altcode:
  The solar energetic particle event on 14 December 2006 was observed
  by several near-Earth spacecraft including the Advanced Composition
  Explorer (ACE), STEREO A and B, SOHO and Wind. An interesting feature
  of this event is a series of unusual fluctuations in the particle
  intensity that occurred during the first few hours. These fluctuations
  were observed inside a magnetic cloud that originated in a solar
  event on 13 December and show both similarities and variations at the
  different spacecraft. Interestingly, the most striking difference is
  between observations at the two closely-separated STEREO spacecraft. In
  particular, large fluctuations in the proton intensity were seen by the
  High Energy Telescope (HET) on STEREO A, and to a lesser extent at Wind
  and ACE, but not by the STEREO B HET. We conclude that the differences
  in intensity-time profiles were caused by anisotropies in the particle
  distribution and the different viewing directions of the individual
  particle telescopes. The intensity/anisotropy variations suggest that
  flux tubes with different particle propagation conditions existed
  within this magnetic cloud despite the absence of local magnetic field
  signatures associated with these regions. The intensity fluctuations are
  similar to those occasionally seen in impulsive particle events. There
  were also spacecraft-to-spacecraft differences during the onset of
  the particle event. An initial rapid onset of energetic (&gt; 40
  MeV) protons was observed by the STEREO A and B spacecraft outside
  the magnetic cloud, but not by spacecraft such as SOHO that were
  already inside the magnetic cloud at this time. The latter spacecraft
  observed a slower, lower intensity increase. Evidently, energetic
  proton propagation from the solar event to the vicinity of Earth was
  inhibited within the magnetic cloud compared to outside.

---------------------------------------------------------
Title: Solar Release Times of Energetic Particles in Ground-Level
    Events
Authors: Reames, Donald V.
2009ApJ...693..812R    Altcode:
  We study the onset times of energetic particles of various species
  and velocities, v, in large solar energetic particle events with
  sufficiently hard spectra that are seen by neutron monitors at ground
  level. Observations of He, O, and Fe from the Wind spacecraft provide
  especially well-defined sequences of onset times, and data from
  IMP-8, GOES, and neutron monitors contribute importantly at higher
  energies. Plotting onset times versus v <SUP>-1</SUP> yields a line
  with the initial solar particle release (SPR) time as the intercept
  and the magnetic path length as the slope. We find consistent results
  for 13 of the 16 ground-level events that occurred from 1994 to 2007,
  in solar cycle 23. Path lengths vary from 1.1 to 2.2 AU in the 13
  events. In all of the events, SPR times occur after the onset of the
  shock wave-induced type II radio emission. Events with well-defined SPR
  times are found over a wide span of solar longitude, suggesting that
  all ion species and energies are released together, even far from the
  source longitude, with no evidence of energy- or rigidity-dependent
  coronal transport. If the SPR time is converted to a radial distance
  of the source shock wave from the Sun and plotted against longitude,
  acceleration for well-connected events is found to begin at 2-4 solar
  radii over a longitude span of ~ 100° and to rise to greater heights
  only at longitudes more distant from the source, as would be expected
  from shock-acceleration models.

---------------------------------------------------------
Title: Exploring the global shock scenario at multiple points
between sun and earth: The solar transients launched on January 1
    and September 23, 1978
Authors: Berdichevsky, D. B.; Reames, D. V.; Wu, C. -C.; Schwenn, R.;
   Lepping, R. P.; MacDowall, R. J.; Farrugia, C. J.; Bougeret, J. -L.;
   Ng, C.; Lazarus, A. J.
2009AdSpR..43..113B    Altcode:
  We revisit the transient interplanetary events of January 1 and
  September 23, 1978. Using in-situ and remote sensing observations at
  locations widely separated in longitudes and distances from the Sun,
  we infer that in both cases the overall shock surface had a very fast
  “nose” region with speeds &gt;900 and &gt;1500 km<SUP>-1</SUP>
  in the January and September events, respectively, and much slower
  flank speeds (∼600 km<SUP>-1</SUP> or less), suggesting a shock
  surface with a strong speed gradient with heliospheric longitude. The
  shock-nose regions are thus likely efficient acceleration sites of MeV
  ions, even at 1 AU from the Sun. Our 3D magnetohydrodynamics modeling
  suggests that a 24° × 24° localized disturbance at 18 solar radii
  injecting momentum 100 times the background solar wind input over 1
  h can produce a disturbance in semi-quantitative agreement with the
  observed shock arrival time, plasma density and velocity time series
  in the January 1978 event.

---------------------------------------------------------
Title: Role of Self-Amplified Waves in Coronal Shock Acceleration
Authors: Ng, C. K.; Reames, D. V.
2008AGUFMSH23C..06N    Altcode:
  Solar-energetic-proton (SEP) acceleration at a parallel shock is modeled
  with self-consistent Alfvén-wave excitation and shock transmission. 18
  - 50 keV seed protons at 0.001 plasma proton density are accelerated
  in 10 minutes to a power-law intensity spectrum rolling over at ~
  300 MeV by a 2500 km/s shock launched from 3.5 solar radii in typical
  coronal condition with low ambient wave intensity. Scattering of large
  pitch-angle high-energy SEPs by waves amplified by small pitch-angle
  low-energy SEPs bootstraps the acceleration. The rapid acceleration
  is inappreciably retarded by wavenumber shift of shock-transmitted
  Alfvén waves or by the interaction of sunward streaming SEPs
  with downstream waves. There is no significant second-order Fermi
  acceleration. SEP acceleration beyond the 'knee' energy proceeds
  from large to small pitch-angles, for gyroresonant wave-particle
  interaction at k ~ B/(μ P). B is magnetic field, k wavenumber, P
  rigidity and μ pitch-cosine. Classical mean-free-path is inapplicable
  in this time-dependent process. Using the above μ-dependent resonant
  condition to calculate wave-growth rates but the 'sharpened' condition
  k ~ B/P to calculate μ-scattering rates underestimates scattering
  by self-amplified waves, giving little acceleration (Berezhko et al
  1998). Using k ~ B/P to calculate wave-growth and scattering rates
  (Vainio &amp; Laitinen 2007) is consistent but incorrectly requires the
  SEPs to amplify unique waves from the weak ambient state. In contrast,
  true gyroresonant interaction must 'relay' the influence of amplified
  waves from low-P large-μ SEPs to high-P low-μ SEPs, leading to fast
  acceleration. Model results will be presented and dependence on model
  parameters will be discussed.

---------------------------------------------------------
Title: The Unusual Time History of Galactic and Anomalous Cosmic
    Rays at 1 AU over the Solar Minimum of Cycle 23
Authors: McDonald, F. B.; Webber, W. R.; Reames, D. V.
2008AGUFMSH21C..06M    Altcode:
  Studies of the galactic cosmic rays temporal variations (GCRs) over
  the "Modern Era" (from 1950s) establish the existence of a 22-year
  cosmic ray modulation cycle that is dominated by the 11-year solar
  activity cycle but is significantly influenced by gradient and curvature
  drifts in the interplanetary magnetic field (IPB) in association with
  changes in the tilt of the heliospheric neutral current sheet over
  the heliomagnetic cycle. In qA&lt;0 epochs (when positive ions flow in
  along the neutral sheet and out over the solar poles), the solar minimum
  cosmic rays intensity is peaked over a period of several months (1965,
  1987) in contrast to the 3 - 4 year plateau periods for qA&gt;0 minima
  when the flow pattern is reversed. However, for 200 MeV/n GCR HE at 1
  AU there is a quasi-plateau region for the cycle 23 solar minimum that
  now extends over some 12 months. The intensity level of this component
  is essentially the same as that of 1965 and 1987, as is the large
  depression of anomalous cosmic ray ACR He (10 - 40 MeV/n) relative to
  the qA&gt;0 minima. There appears to be two different solar effects,
  the current sheet tilt in 2007 is less than in 1987 while the magnitude
  of the 1P B field is at its lowest value since essentially continuous
  measurements began in 1963. These will have off-setting effects on the
  GCR intensity. 10 Be and 14 C studies have shown that previous epochs of
  low solar activity [Oort (1050 AD); Spoerer (1420-1540); and Maunder
  (1615-1715)] have been marked by high cosmic ray intensity. There
  were other periods of reduced solar activity [Wolf (1320) and Dalton
  (1810)] which were associated with more moderate enhancements of the
  GCR intensity. Studies using data from the Cosmic Ray Network [IMP,
  ACE, neutron monitors at 1 AU, and Pioneer, Voyager, and Ulysses at
  greater heliocentric distances] are providing a better understanding
  of the solar phenomena that produce the cosmic ray modulation and
  should lead to an understanding of the solar changes in the distant
  past associated with the epochs of enhanced GCR intensity.

---------------------------------------------------------
Title: Shock Acceleration of Solar Energetic Protons: The First
    10 Minutes
Authors: Ng, C. K.; Reames, D. V.
2008ApJ...686L.123N    Altcode:
  Proton acceleration at a parallel coronal shock is modeled with
  self-consistent Alfvén wave excitation and shock transmission. 18-50
  keV seed protons at 0.1% of plasma proton density are accelerated
  in 10 minutes to a power-law intensity spectrum rolling over at 300
  MeV by a 2500 km s<SUP>-1</SUP> shock traveling outward from 3.5
  r<SUB>⊙</SUB>, for typical coronal conditions and low ambient wave
  intensities. Interaction of high-energy protons of large pitch angles
  with Alfvén waves amplified by low-energy protons of small pitch angles
  is key to rapid acceleration. Shock acceleration is not significantly
  retarded by sunward streaming protons interacting with downstream
  waves. There is no significant second-order Fermi acceleration.

---------------------------------------------------------
Title: SEP Acceleration by Traveling Coronal Shock
Authors: Ng, C. K.; Reames, D. V.; Tylka, A. J.
2008AGUSMSH41A..09N    Altcode:
  We present simulations from a numerical model of
  solar-energetic-particle (SEP) acceleration at a coronal-
  mass-ejection-driven shock traveling through the solar corona. The
  model includes full pitch-angle dependence, self-consistent resonant
  wave-particle interaction, focusing, convection, adiabatic deceleration,
  wave propagation and wave transmission at shock. The model is solved
  with a new accurate finite-difference method. Outward streaming
  SEPs amplify upstream outward Alfvén waves, which are further
  enhanced by the wave transmission process as they travel downstream
  of the advancing shock. The explosively growing waves bootstrap SEP
  acceleration. However, shock accelerated SEPs also stream downstream,
  damping outward waves and enhancing inward waves there. Particles
  scattered between upstream outward waves and downstream inward waves
  experience less compression than SEPs scattered between upstream
  outward waves and downstream outward waves. Thus SEPs streaming
  inward downstream tend to slow shock acceleration and to produce
  a softer SEP energy spectrum. We will illustrate these opposing
  processes with computed results and discuss how SEP acceleration
  depends on model assumptions and physical parameters, e.g., shock
  speed, Alfvén speed, ambient wave intensity, seed particle energy and
  density. Acknowledgment: this work was supported by NASA LWS04-0000-0076
  and SHP04-0016-0024.

---------------------------------------------------------
Title: A Comparison of Elemental Abundance Ratios in SEP Events in
    Fast and Slow Solar Wind Regions
Authors: Kahler, S.; Tylka, A.; Reames, D.
2008AGUSMSH43C..01K    Altcode:
  The solar energetic (E &gt; 1 MeV) particles (SEP) observed in gradual
  events at 1 AU are generally assumed to be accelerated from ambient
  suprathermal particles. If so, then the elemental abundances of SEPs
  produced in fast wind regions might be systematically distinguished
  from the abundances of those from slow wind regions. We look for these
  differences using the Mg/Ne ratios in a large number of SEP events
  from the past solar cycle. The solar wind regions are characterized
  by O7/O6 ratios and by the three-component wind stream classification
  of Richardson et al. (JGR, 2002). The Mg/Ne ratio provides a low/high
  first ionization potential (FIP) element ratio with comparable particle
  rigidities to minimize propagation effects. Our initial survey shows no
  significant differences in the 5-10 MeV/nucleon range for fast and slow
  wind SEP events. This result supplements the earlier finding that SEP
  events are observed frequently in fast wind and are not associated with
  unusually higher CME speeds, although the higher Alfven and solar wind
  flow speeds in fast wind regions should mitigate against the production
  of CME-driven shocks in those regions. We discuss the implications of
  our results for shock seed populations and cross-field propagation. AJT
  was supported by the Office of Naval Research and NASA DPR NNG06EC55I.

---------------------------------------------------------
Title: Ion Anisotropy and High-Energy Variability of Large Solar
Particle Events: A Comparative Study
Authors: Tan, Lun C.; Reames, Donald V.; Ng, Chee K.
2008ApJ...678.1471T    Altcode:
  We have made comparative studies of ion anisotropy and high-energy
  variability of solar energetic particle (SEP) events previously examined
  by the Solar, Heliospheric, and Interplanetary Environment (SHINE)
  Workshop campaign. We have found distinctly different characteristics of
  SEPs in two large "gradual" events having very similar solar progenitors
  (the 2002 April 21 and August 24 events). Since the scattering centers
  of SEPs are approximately frozen in the solar wind, we emphasize
  work in the solar-wind frame, where SEPs tend to be isotropized and
  small anisotropies are easier to detect. While in the August event
  no streaming reversal occurred, in the April event the field-aligned
  anisotropy of all heavy ions showed signs of streaming reversal. The
  difference in streaming reversal was consistent with the difference in
  the presence of the outer reflecting boundary. In the April event the
  magnetic mirror, which was located behind the interplanetary shock
  driven by the preceding coronal mass ejection (CME), could block
  the stream of SEPs, while in the August event SEPs escaped freely in
  the absence of any nearby boundary. The magnetic mirror was formed
  at the bottleneck of magnetic field lines draped around a flank of
  the preceding CME. In previous SHINE event analysis, the contrasting
  event durations and Fe/O ratios of the both events were explained as
  the interplay between shock geometry and seed population. Our new
  findings, however, indicate that event duration and time, as well
  as spectral variation, are also affected by the presence of a nearby
  reflecting boundary.

---------------------------------------------------------
Title: The High Energy Telescope for STEREO
Authors: von Rosenvinge, T. T.; Reames, D. V.; Baker, R.; Hawk,
   J.; Nolan, J. T.; Ryan, L.; Shuman, S.; Wortman, K. A.; Mewaldt,
   R. A.; Cummings, A. C.; Cook, W. R.; Labrador, A. W.; Leske, R. A.;
   Wiedenbeck, M. E.
2008SSRv..136..391V    Altcode: 2008SSRv..tmp...20V
  The IMPACT investigation for the STEREO Mission includes a complement
  of Solar Energetic Particle instruments on each of the two STEREO
  spacecraft. Of these instruments, the High Energy Telescopes (HETs)
  provide the highest energy measurements. This paper describes the
  HETs in detail, including the scientific objectives, the sensors,
  the overall mechanical and electrical design, and the on-board
  software. The HETs are designed to measure the abundances and energy
  spectra of electrons, protons, He, and heavier nuclei up to Fe in
  interplanetary space. For protons and He that stop in the HET, the
  kinetic energy range corresponds to ∼13 to 40 MeV/n. Protons that
  do not stop in the telescope (referred to as penetrating protons)
  are measured up to ∼100 MeV/n, as are penetrating He. For stopping
  He, the individual isotopes <SUP>3</SUP>He and <SUP>4</SUP>He can be
  distinguished. Stopping electrons are measured in the energy range
  ∼0.7 6 MeV.

---------------------------------------------------------
Title: Theoretical modeling for the stereo mission
Authors: Aschwanden, Markus J.; Burlaga, L. F.; Kaiser, M. L.; Ng,
   C. K.; Reames, D. V.; Reiner, M. J.; Gombosi, T. I.; Lugaz, N.;
   Manchester, W.; Roussev, I. I.; Zurbuchen, T. H.; Farrugia, C. J.;
   Galvin, A. B.; Lee, M. A.; Linker, J. A.; Mikić, Z.; Riley, P.;
   Alexander, D.; Sandman, A. W.; Cook, J. W.; Howard, R. A.; Odstrčil,
   D.; Pizzo, V. J.; Kóta, J.; Liewer, P. C.; Luhmann, J. G.; Inhester,
   B.; Schwenn, R. W.; Solanki, S. K.; Vasyliunas, V. M.; Wiegelmann, T.;
   Blush, L.; Bochsler, P.; Cairns, I. H.; Robinson, P. A.; Bothmer,
   V.; Kecskemety, K.; Llebaria, A.; Maksimovic, M.; Scholer, M.;
   Wimmer-Schweingruber, R. F.
2008SSRv..136..565A    Altcode: 2006SSRv..tmp...75A
  We summarize the theory and modeling efforts for the STEREO mission,
  which will be used to interpret the data of both the remote-sensing
  (SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The
  modeling includes the coronal plasma, in both open and closed magnetic
  structures, and the solar wind and its expansion outwards from the Sun,
  which defines the heliosphere. Particular emphasis is given to modeling
  of dynamic phenomena associated with the initiation and propagation
  of coronal mass ejections (CMEs). The modeling of the CME initiation
  includes magnetic shearing, kink instability, filament eruption, and
  magnetic reconnection in the flaring lower corona. The modeling of CME
  propagation entails interplanetary shocks, interplanetary particle
  beams, solar energetic particles (SEPs), geoeffective connections,
  and space weather. This review describes mostly existing models of
  groups that have committed their work to the STEREO mission, but is by
  no means exhaustive or comprehensive regarding alternative theoretical
  approaches.

---------------------------------------------------------
Title: STEREO IMPACT Investigation Goals, Measurements, and Data
    Products Overview
Authors: Luhmann, J. G.; Curtis, D. W.; Schroeder, P.; McCauley, J.;
   Lin, R. P.; Larson, D. E.; Bale, S. D.; Sauvaud, J. -A.; Aoustin, C.;
   Mewaldt, R. A.; Cummings, A. C.; Stone, E. C.; Davis, A. J.; Cook,
   W. R.; Kecman, B.; Wiedenbeck, M. E.; von Rosenvinge, T.; Acuna,
   M. H.; Reichenthal, L. S.; Shuman, S.; Wortman, K. A.; Reames, D. V.;
   Mueller-Mellin, R.; Kunow, H.; Mason, G. M.; Walpole, P.; Korth, A.;
   Sanderson, T. R.; Russell, C. T.; Gosling, J. T.
2008SSRv..136..117L    Altcode:
  The IMPACT (In situ Measurements of Particles And CME Transients)
  investigation on the STEREO mission was designed and developed to
  provide multipoint solar wind and suprathermal electron, interplanetary
  magnetic field, and solar energetic particle information required to
  unravel the nature of coronal mass ejections and their heliospheric
  consequences. IMPACT consists of seven individual sensors which are
  packaged into a boom suite, and a SEP suite. This review summarizes
  the science objectives of IMPACT, the instruments that comprise
  the IMPACT investigation, the accommodation of IMPACT on the STEREO
  twin spacecraft, and the overall data products that will flow from
  the IMPACT measurements. Accompanying papers in this volume of Space
  Science Reviews highlight the individual sensor technical details and
  capabilities, STEREO project plans for the use of IMPACT data, and
  modeling activities for IMPACT (and other STEREO) data interpretation.

---------------------------------------------------------
Title: The High Energy Telescopes for the STEREO Mission
Authors: von Rosenvinge, T. T.; Cummings, A. C.; Leske, R. A.; Mewaldt,
   R. A.; Reames, D. V.; Stone, E. C.; Wiedenbeck, M. E.
2008ICRC....1..103V    Altcode: 2008ICRC...30a.103V
  We describe the High Energy Telescopes (HETs), which are part of the
  IMPACT investigation for the STEREO mission (Principal Investigator:
  Janet Luhmann, University of California at Berkeley). The two STEREO
  spacecraft were launched from Cape Canaveral, FL on October 25,
  2006. High energy electrons (~ 0.7 -6 MeV) and nuclei from hydrogen
  to iron (~ 13 - 200 MeV/nucleon) are detected by the HETs, one on
  each spacecraft. Observations from one pass through the Earth’s
  magnetosphere and from four X-class solar events in December,
  2006 are presented to illustrate the capabilities of the HETs. The
  HET observations are also compared with observations from other
  spacecraft. The event of December 13th was the first Ground Level
  Event in almost two years. We will compare the elemental composition
  of this event with that of the previous Ground Level Event on January
  20, 2005. This work was supported by NASA (at Caltech and JPL under
  contract NAS5-00133 and grant NAG5-12929).

---------------------------------------------------------
Title: Bulk Flow Velocity and First-Order Anisotropy of Solar
Energetic Particles Observed on the Wind Spacecraft: Overview of Three
    “Gradual” Particle Events
Authors: Tan, Lun C.; Reames, Donald V.; Ng, Chee K.
2007ApJ...661.1297T    Altcode:
  We have developed techniques to calculate bulk flow velocity and
  first-order anisotropy of solar energetic particles (SEPs) with MeV
  nucleon<SUP>-1</SUP> energies as recorded on the Wind spacecraft. Using
  the techniques we selected and analyzed three gradual SEP events having
  different solar longitudes. Since upstream of interplanetary (IP)
  shocks during our selected events the interplanetary magnetic field is
  nearly perpendicular to the solar wind, the diffusive transport of SEPs
  along the magnetic field line is conveniently decoupled from solar-wind
  streaming. We present the bulk flow velocity measurements of H, He, O,
  and Fe ions at different energies. In two of the three events studied,
  it is seen that the flow directions of heavy ions reverse in sequence,
  i.e., faster ions reverse their direction earlier. Several hours
  before the IP shock passage, the bulk flows of all heavy ions become
  opposite to the proton flow. Thus, in the upstream region we mainly
  observe shock-accelerated protons that continue to flow away from
  the shock, while higher rigidity heavy ions predominantly come from
  strong acceleration near the Sun. The reversed ion direction appears
  also to involve a reflecting boundary beyond 1 AU, from which higher
  velocity ions return earlier. The preferred geometry of the selected
  2001 September 24 event also allows us to determine the propagating
  direction of proton-generated Alfvén waves based on flow velocity
  measurements of heavy ions.

---------------------------------------------------------
Title: Recent Results of the 2005 LWS TR&amp;T Focus Team for Solar
    Energetic Particles
Authors: Desai, M. I.; Cohen, C. M.; Smith, C. W.; Lee, M. A.;
   Litvinenko, Y.; Reames, D. V.; Ng, C. K.; Tylka, A. J.; Kota, J.;
   Giacalone, J.; Jokipii, J. R.; Sokolov, I.; Gombosi, T.; Roussev,
   I. I.; Li, G.; Zank, G. P.; Tessein, J.
2006AGUFMSH23C..03D    Altcode:
  Shock waves driven by coronal mass ejections are presently believed
  to be responsible for producing large gradual solar energetic
  particle (SEP) events that can pose significant radiation hazard
  for humans and technological systems near Earth. However, our
  present ability to accurately predict various properties of SEP
  events (e.g., peak intensities, energy spectra, and composition)
  is somewhat limited. Reliable prediction of these properties depends
  on a multitude of observational and theoretical cross-disciplinary
  studies that include: (1) Understanding and modeling the initiation and
  propagation of fast CMEs and the evolution of shock characteristics
  as they travel through the corona and interplanetary medium, (2)
  Characterizing the ambient coronal and solar wind plasma, the solar
  and interplanetary magnetic field, and the suprathermal ion population
  through which the CMEs and their shocks propagate en route to Earth,
  and (3) Developing a detailed understanding of particle injection and
  acceleration at CME-driven shocks and their subsequent transport out
  to 1 AU. Such studies are being routinely conducted both, individually
  and collectively by members of the 2005 LWS TR&amp;T Focus Team for
  SEPs. In this talk we will summarize the SEP Team's ongoing efforts,
  highlight the key new results, and discuss some of the main scientific
  challenges that we need to overcome in order to improve current
  understanding of the physical processes occurring in large SEP events.

---------------------------------------------------------
Title: Bulk Flow Velocity and First-Order Anisotropy of Solar
    Energetic Particles Observed on Wind Spacecraft
Authors: Tan, L. C.; Reames, D. V.; Ng, C. K.
2006AGUFMSH43B1515T    Altcode:
  We have developed a technique to calculate the bulk flow velocity
  and first-order anisotropy of solar energetic particles (SEPs) with
  MeV per nucleon energies. Using the technique we have selected and
  analyzed three "gradual" SEP events recorded by the Low-Energy Matrix
  Telescope (LEMT) of the Energetic Particles: Acceleration, Composition,
  and Transport experiment (EPACT) on the Wind spacecraft. Since in
  our selected events, the interplanetary magnetic field upstream of
  interplanetary (IP) shock is nearly perpendicular to the solar-wind
  velocity, the effect of SEP scattering centers can be clearly
  discerned. From the observations of H, He, O, and Fe ions at different
  energies, we find that upstream of IP shock the bulk flow direction
  of heavy ions is opposite to that of protons. In addition, the ion
  velocity/rigidity dependence of the first-order anisotropy of SEPs is
  different between the onset and the upstream region. The implication
  of our observations will be discussed.

---------------------------------------------------------
Title: The Disappearance of Large, Fe-Rich Solar Energetic Particle
Events in the Declining Phase of Cycle 23: Implications for the Role
    of Flares
Authors: Dietrich, W. F.; Tylka, A. J.; Cliver, E. W.; Cohen, C. M.;
   Mewaldt, R. A.; Reames, D. V.
2006AGUFMSH41B..03D    Altcode:
  Solar energetic particle (SEP) events are generally divided into two
  categories, "gradual" and "impulsive". corresponding, respectively, to
  acceleration by shocks driven by fast coronal mass ejections (CMEs) or
  acceleration at sites associated with flares, probably through resonant
  wave-particle interactions following magnetic reconnection. One of the
  defining distinctions between the two types is the event-integrated
  Fe/O ratio, with gradual events at a few MeV/nucleon exhibiting
  typical coronal values while impulsive events generally show strong
  enhancements. But the precise, comprehensive observations from a fleet
  of new spacecraft at the start of Cycle 23 immediately challenged this
  neat picture: Fe/O ratios generally varied with energy, and a large
  fraction of the nominally "gradual" events, when observed at energies
  above the few MeV/nucleon where the two categories were originally
  developed, showed enhanced Fe/O ratios approaching those typically
  associated with impulsive events. In 1997-2002, 13 out of the 38 very
  large SEP events (identified by &gt;30 MeV proton fluence above 2 x
  105/cm2-sr) had an Fe/O ratio above 30 MeV/nucleon that was at least
  four times the nominal coronal value. But in 2003-2005, zero out of the
  20 events satisfying the same selection criterion displayed comparably
  large Fe/O enhancements. This dramatic shift clearly indicates that
  the condition(s) that allow flares to contribute to large SEP events
  have changed in some fundamental way in the declining phase of Cycle
  23. In particular, three hypotheses (direct-flare; shock- acceleration
  of escaping suprathermals from the accompanying flare; or shock
  acceleration of remnant suprathermals from previous flare activity)
  have been proposed in order to explain the flare-like composition seen
  at high energies in some large gradual events. Based on comparisons
  of the reported flare, CME, and suprathermal characteristics in the
  two time periods, we show that the third hypothesis appears to be most
  likely to be able to accommodate the late-Cycle disappearance of the
  large Fe-rich events. We also examine open issues surrounding this
  explanation that Sentinels will be able to address.

---------------------------------------------------------
Title: Solar Sources of Impulsive Solar Energetic Particle Events
    and Their Magnetic Field Connection to the Earth
Authors: Nitta, Nariaki V.; Reames, Donald V.; De Rosa, Marc L.; Liu,
   Yang; Yashiro, Seiji; Gopalswamy, Natchimuthuk
2006ApJ...650..438N    Altcode:
  This paper investigates the solar origin of impulsive solar energetic
  particle (SEP) events, often referred to as <SUP>3</SUP>He-rich flares,
  by attempting to locate the source regions of 117 events as observed
  at ~2-3 MeV amu<SUP>-1</SUP>. Given large uncertainties as to when
  ions at these energies were injected, we use type III radio bursts
  that occur within a 5 hr time window preceding the observed ion onset,
  and search in EUV and X-ray full-disk images for brightenings around
  the times of the type III bursts. In this way we find the solar sources
  in 69 events. High cadence EUV images often reveal a jet in the source
  region shortly after the type III burst. We also study magnetic field
  connections between the Earth and the solar sources of impulsive SEP
  events as identified above, combining the potential field source
  surface (PFSS) model for the coronal field and the Parker spiral
  for the interplanetary magnetic field. We find open field lines in
  and around ~80% of the source regions. But only in ~40% of the cases,
  can we find field lines that are both close to the source region at the
  photosphere and to the Parker spiral coordinates at the source surface,
  suggesting challenges in understanding the Sun-Earth magnetic field
  with observations available at present and in near future.

---------------------------------------------------------
Title: A Comparative Study of Ion Characteristics in the Large Gradual
    Solar Energetic Particle Events of 2002 April 21 and 2002 August 24
Authors: Tylka, A. J.; Cohen, C. M. S.; Dietrich, W. F.; Lee, M. A.;
   Maclennan, C. G.; Mewaldt, R. A.; Ng, C. K.; Reames, D. V.
2006ApJS..164..536T    Altcode:
  Solar energetic particles (SEPs) provide an opportunity to study in
  detail the processes of particle acceleration and transport that are
  ubiquitous in astrophysical plasmas. Tylka et al. focused on the problem
  of SEP spectral and compositional variability at energies above a few
  tens of MeV per nucleon. They motivated their study with two large,
  gradual SEP events, 2002 April 21 and 2002 August 24, which have
  similar fast coronal mass ejections (CMEs) and flares but nevertheless
  illustrate the extremes of high-energy behavior. In this paper, we
  present additional detailed comparisons between the ion characteristics
  of these events. These results should be helpful in developing and
  testing new SEP models, which are currently under development.

---------------------------------------------------------
Title: Shock Geometry, Seed Populations, and the Origin of Variable
    Elemental Composition at High Energies in Large Gradual Solar
    Particle Events
Authors: Tylka, A. J.; Cohen, C. M. S.; Dietrich, W. F.; Lee, M. A.;
   Maclennan, C. G.; Mewaldt, R. A.; Ng, C. K.; Reames, D. V.
2005ApJ...625..474T    Altcode:
  Above a few tens of MeV per nucleon, large, gradual solar
  energetic particle (SEP) events are highly variable in their
  spectral characteristics and elemental composition. The origin
  of this variability has been a matter of intense and ongoing
  debate. In this paper, we propose that this variability arises
  from the interplay of two factors-shock geometry and a compound
  seed population, typically comprising both solar-wind and flare
  suprathermals. Whereas quasi-parallel shocks generally draw their
  seeds from solar-wind suprathermals, quasi-perpendicular shocks-by
  requiring a higher initial speed for effective injection-preferentially
  accelerate seed particles from flares. Solar-wind and flare seed
  particles have distinctive compositional characteristics, which are
  then reflected in the accelerated particles. We first examine our
  hypothesis in the context of particles locally accelerated near 1 AU
  by traveling interplanetary shocks. We illustrate the implications
  of our hypothesis for SEPs with two very large events, 2002 April 21
  and 2002 August 24. These two events arise from very similar solar
  progenitors but nevertheless epitomize extremes in high-energy SEP
  variability. We then test our hypothesis with correlation studies
  based on observations of 43 large SEP events in 1997-2003 by the
  Advanced Composition Explorer, Wind, the Interplanetary Monitoring
  Platform 8, and GOES. We consider correlations among high-energy Fe/O,
  event size, spectral characteristics, the presence of GeV protons,
  and event duration at high energies. The observed correlations are
  all qualitatively consistent with our hypothesis. Although these
  correlation studies cannot be construed as proof of our hypothesis,
  they certainly confirm its viability. We also examine the alternative
  hypothesis in which a direct flare component-rather than flare particles
  subsequently processed through a shock-dominates at high energies. This
  alternative would produce compositional characteristics similar to
  those of our hypothesis. However, the observed longitude distribution
  of the enhanced Fe/O events, their spectral characteristics, and
  recent timing studies all pose serious challenges for a direct flare
  component. We also comment on measurements of the mean ionic charge
  state of Fe at high energies. We conclude that shock geometry and
  seed population potentially provide a framework for understanding
  the overall high-energy variability in large SEP events. We suggest
  additional studies for testing this hypothesis.

---------------------------------------------------------
Title: IMPACT: Science goals and firsts with STEREO
Authors: Luhmann, J. G.; Curtis, D. W.; Lin, R. P.; Larson, D.;
   Schroeder, P.; Cummings, A.; Mewaldt, R. A.; Stone, E. C.; Davis, A.;
   von Rosenvinge, T.; Acuna, M. H.; Reames, D.; Ng, C.; Ogilvie, K.;
   Mueller-Mellin, R.; Kunow, H.; Mason, G. M.; Wiedenbeck, M.; Sauvaud,
   A.; Aoustin, C.; Louarn, P.; Dandouras, J.; Korth, A.; Bothmer, V.;
   Vasyliunas, V.; Sanderson, T.; Marsden, R. G.; Russell, C. T.; Gosling,
   J. T.; Bougeret, J. L.; McComas, D. J.; Linker, J. A.; Riley, P.;
   Odstrcil, D.; Pizzo, V. J.; Gombosi, T.; DeZeeuw, D.; Kecskemety, K.
2005AdSpR..36.1534L    Altcode:
  The in situ measurements of particles and CME transients (IMPACT)
  investigation on the twin STEREO spacecraft focuses on the solar
  energetic particle, solar wind and suprathermal electron, and magnetic
  field measurements needed to address STEREO's goals. IMPACT will provide
  regular, identical, in situ multipoint measurements bracketing Earth
  as each spacecraft separates from it at a rate of ∼22°/yr along
  Earth's orbit. Combined with the PLASTIC and SWAVES investigations,
  IMPACT fills a critical role in the STEREO quest to connect SECCHI's
  3D coronal images to their interplanetary consequences.

---------------------------------------------------------
Title: Solar Flare Nuclear Gamma Rays and Energetic Particles in
    Space, 1980-198
Authors: Cliver, E. W.; Vestrand, W. T.; Reames, D. V.
2005ICRC....1...53C    Altcode: 2005ICRC...29a..53C
  No abstract at ADS

---------------------------------------------------------
Title: The Solar Energetic Particle Event of 16 August 2001: ~
    400 MeV Protons Following an Eruption at ~ W180
Authors: Cliver, E. W.; Thompson, B. J.; Lawrence, G. R.; Zhukov,
   A. N.; Tylka, A. J.; Dietrich, W. F.; Reames, D. V.; Reiner, M. J.;
   MacDowall, R . J.; Kosovichev, A. G.; Ling, A. G.
2005ICRC....1..121C    Altcode: 2005ICRC...29a.121C
  No abstract at ADS

---------------------------------------------------------
Title: Association of Coronal Mass Ejections and Type II Radio Bursts
    with Impulsive Solar Energetic Particle Events
Authors: Yashiro, S.; Gopalswamy, N.; Cliver, E. W.; Reames, D. V.;
   Kaiser, M. L.; Howard, R. A.
2004ASPC..325..401Y    Altcode:
  We report the association of impulsive solar energetic particle (SEP)
  events with coronal mass ejections (CMEs) and metric type II radio
  bursts. We identified 38 impulsive SEP events using the WIND/EPACT
  instrument and their CME association was investigated using white
  light data from SOHO/LASCO. We found that (1) at least ∼ 28--39 % of
  impulsive SEP events were associated with CMEs, (2) only 8--13 % were
  associated with metric type II radio bursts. The statistical properties
  of the associated CMEs were investigated and compared with those of
  general CMEs and CMEs associated with large gradual SEP events. The
  CMEs associated with impulsive SEP events were significantly slower
  (median speed of 613 kmps) and narrower (49 deg) than those of CMEs
  associated with large gradual SEP events (1336 kmps, 360 deg), but
  faster than the general CMEs (408 kmps).

---------------------------------------------------------
Title: The unusual signatures at and near 2018 UT (Wind in situ
    observations) of the travelling, fast forward interplanetary shock
    on September 25, 2001
Authors: Berdichevsky, D. B.; Desch, M. D.; Lepping, R. P.; Larson,
   D. E.; Lin, R.; Kasper, J.; Nagai, T.; Reames, D. V.
2004AGUFMSH33A1197B    Altcode:
  We show that at 2018 UT on September 25, 2001, a velocity discontinuity
  of [-300, -200, -200] kms-1 (in GSE coordinates) passes Wind. However,
  the downstream shock candidate region appears to be far from thermal
  equilibrium. Henceforth it is our purpose to show that it is not a
  shock discontinuity amenable to the Rankine-Hugoniot based techniques. A
  possible shock related thermalization (at Wind) appears approximately
  90 seconds later, at 2019:31UT, behind a magnetic hole showing a large
  rotational discontinuity. Timing using Wind and other spacecraft located
  tens to hundreds of earth radii apart allows the preliminary assessment
  of an overall shock normal. In the context of Sun-Earth connections, the
  disturbance appears related to the Sept 24,1030UT halo-CME [EIT observed
  a CME starting in AR9632 located at [S18; E27] at 09:12 UT], which
  was moving at 2240 kms-1 in the plane of the sky. In most events we
  put special value on the identification of the plasma density by using
  the electron plasma thermal line. However, there is a loss of detection
  of the plasma line between 2010 and 2016 UT. This shock is important,
  because strong particle and wave intensities appear to be associated
  with it. Candidate compressional waves are identified upstream of the
  shock. Their presence suggests that they are an additional source of
  turbulence. This is so, because the compressional waves are likely
  being created by the shock accelerated particles and subsequently
  overtaken by the shock, probably, in an almost continuous process.

---------------------------------------------------------
Title: Heavy-Element Abundances in Solar Energetic Particle Events
Authors: Reames, D. V.; Ng, C. K.
2004ApJ...610..510R    Altcode:
  We survey the relative abundances of elements with 1&lt;=Z&lt;=82
  in solar energetic particle (SEP) events observed at 2-10 MeV
  amu<SUP>-1</SUP> during nearly 9 years aboard the Wind spacecraft,
  with special emphasis on enhanced abundances of elements with
  Z&gt;=34. Abundances of Fe/O again show a bimodal distribution with
  distinct contributions from impulsive and gradual SEP events, as seen
  in earlier solar cycles. Periods with greatly enhanced abundances of
  (50&lt;=Z&lt;=56)/O, just as those with enhanced <SUP>3</SUP>He/<SUP>
  4</SUP>He, fall prominently in the Fe-rich population of the impulsive
  SEP events. In a sample of the 39 largest impulsive events, 25 have
  measurable enhancements in (50&lt;=Z&lt;=56)/O and (76&lt;=Z&lt;=82)/O,
  relative to coronal values, ranging from ~100 to 10,000. By contrast,
  in a sample of 45 large gradual events the corresponding enhancements
  vary from ~0.2 to 20. However, the magnitude of the heavy-element
  enhancements in impulsive events is less striking than their strong
  correlation with the Fe spectral index and flare size, with the
  largest enhancements occurring in flares with the steepest Fe spectra,
  the smallest Fe fluence, and the lowest X-ray intensity, as reported
  here for the first time. Thus, it seems that small events with low
  energy input can produce only steep spectra of the dominant species
  but accelerate rare heavy elements with great efficiency, probably
  by selective absorption of resonant waves in the flare plasma. With
  increased energy input, enhancements diminish as heavy ions are
  depleted, and spectra of the dominant species harden.

---------------------------------------------------------
Title: Coronal Shocks and Solar Energetic Proton Events
Authors: Cliver, E. W.; Kahler, S. W.; Reames, D. V.
2004ApJ...605..902C    Altcode:
  From 1996 July through 2001 June, less than half (43/98) of all
  favorably located (from solar western hemisphere sources) metric type
  II radio bursts were associated with solar energetic proton (SEP)
  events observed at Earth. When western hemisphere metric type IIs were
  accompanied by decametric-hectometric (DH; 1-14 MHz) type II emission
  (observed by Wind/WAVES) during this period, their association with
  ~20 MeV SEP events (with peak fluxes &gt;=10<SUP>-3</SUP> protons
  cm<SUP>-2</SUP> s<SUP>-1</SUP> sr<SUP>-1</SUP> MeV<SUP>-1</SUP>)
  was 90% (26/29), versus only 25% (17/69) for metric IIs without a DH
  counterpart. Overall, 82% (63%) of all SEP events with visible disk
  origins were associated with metric (DH) type II bursts, with the
  percentage associations increasing with SEP event size to 88% (96%) for
  ~20 MeV SEP events with peak intensities of &gt;=10<SUP>-1</SUP> protons
  cm<SUP>-2</SUP> s<SUP>-1</SUP> sr<SUP>-1</SUP> MeV<SUP>-1</SUP>. Our
  results are consistent with the following possibilities (which are not
  mutually exclusive): (1) large ~20 MeV SEP events result from strong
  shocks that are capable of persisting well beyond ~3 R<SUB>solar</SUB>
  (the nominal 14 MHz plasma level); (2) shock acceleration is most
  efficient above ~3 R<SUB>solar</SUB> and (3) shocks that survive
  beyond ~3 R<SUB>solar</SUB> are more likely to have broad longitudinal
  extents, enabling less well connected shocks to intercept open field
  lines connecting to Earth.

---------------------------------------------------------
Title: Solar energetic particle variations
Authors: Reames, D. V.
2004AdSpR..34..381R    Altcode:
  In the largest solar energetic-particle (SEP) events, acceleration
  occurs at shock waves driven out from the Sun by coronal mass ejections
  (CMEs). In fact, the highest proton intensities directly measured near
  Earth at energies up to ∼1 GeV occur at the time of passage of shocks,
  which arrive about a day after the CMEs leave the Sun. CME-driven shocks
  expanding across magnetic fields can fill over half of the heliosphere
  with SEPs. Proton-generated Alfvén waves trap particles near the shock
  for efficient acceleration but also throttle the intensities at Earth to
  the "streaming limit" early in the events. At high energies, particles
  begin to leak from the shock and the spectrum rolls downward to form an
  energy-spectral "knee" that can vary in energy from ∼1 MeV to ∼1
  GeV in different events. All of these factors affect the radiation
  dose as a function of depth and latitude in the Earth's atmosphere
  and the risk to astronauts and equipment in space. SEP ionization
  of the polar atmosphere produces nitrates that precipitate to become
  trapped in the polar ice. Observations of nitrate deposits in ice cores
  reveal individual large SEP events and extend back ∼400 years. Unlike
  sunspots, SEP events follow the ∼80-100 year Gleissberg cycle rather
  faithfully and are now at a minimum in that cycle. The largest SEP event
  in the last 400 years appears to be related to the flare observed by
  Carrington in 1859, but the probability of SEP events with such large
  fluences falls off sharply because of the streaming limit.

---------------------------------------------------------
Title: Global heliospheric disturbances near 1 AU caused by the
    launch of solar transients on January 1 and September 23, 1978.
Authors: Berdichevsky, D. B.; Reames, D. V.; Wu, C.; Schwenn, R.;
   Lepping, R. P.; Farrugia, C. J.; MacDowall, R. J.; Bougeret, J.; Ng,
   C. K.; Lazarus, A. J.; Richardson, I. G.
2003AGUFMSM22A0219B    Altcode:
  We revisit the transient events of January and September 1978. In
  the January event the ejecta (an interplanetary magnetic cloud, IMC)
  was studied using multiple spacecraft observations [Burlaga et al.,
  1981]. In the September event Reames et al., 1997 studied the spectral
  characteristics of the energetic particles of this big particle
  event with a driven shock passage observed at longitudes nearly 180°
  apart. Here we present a combined analysis of the overall solar wind
  and energetic particles (EP) features of the shock and the driver,
  observed at different locations in longitude. We further evaluate the
  Rankine-Hugoniot properties of the shock at the locations its passage is
  observed and add modeling of the driven shock using a three dimensional
  MHD code which, at this stage of the analysis, does not include the
  magnetic structure of the ejecta. For the study of the shock velocity
  we use remote type II radio burst observations from near Earth (the
  September event), and at different longitude locations we examine:
  (a) flux intensity of the energetic particles, (b) shock strength,
  (c) timing of the shock structure and the driver passage at each
  spacecraft to infer the possible location of the nose of the shock. A
  preliminary assessment on the connection between the global nature
  of the shock and the observed level of energetic particle flux will
  be presented. The data sets include the kilometric radio measurements
  on ISEE3, and the 3 to 80 MeV energetic proton flux data from IMP-8,
  and a similar energy range from Helios at wide longitudinal locations
  relative to Earth. For the solar wind parameters we use magnetic field
  and plasma parameters from instruments at Helios 1, and 2, and ISEE3
  and IMP-8. The data set is completed with the Dst index (Kyoto). We
  acknowledge partial support from NSF and NASA grants, and the NSSDC
  for on-line access to their space science data archives. Burlaga
  LF, E. Sittler, F. Mariani, and R. Schwenn, Magnetic loop behind
  an interplanetary shock: Voyager, Helios, and IMP-8 observations,
  J. Geophys. Res., 86, 6673, 1981. Reames, DV, SW Kahler,, and CK Ng,
  Spatial and temporal invariance in the spectra of gradual particles
  in gradual solar events, Astrophys. J., 491, 414, 1997.

---------------------------------------------------------
Title: Solar-Heliospheric-Magnetospheric Observations on March
23-April 26, 2001: Similarities to Observations in April 1979
Authors: Berdichevsky, D. B.; Farrugia, C. J.; Lepping, R. P.;
   Richardson, I. G.; Galvin, A. B.; Schwenn, R.; Reames, D. V.; Ogilvie,
   K. W.; Kaiser, M. L.
2003AIPC..679..758B    Altcode:
  We discuss the similarities and differences of two intervals of extreme
  interplanetary solar wind conditions, separated almost precisely by
  two solar cycles, in April 1979 and March-April 2001. The similarities
  extend to various data-sets: Energetic particles, solar wind plasma
  and interplanetary magnetic field. In April 1979 observations were made
  by three spacecraft covering a wide longitudinal range (~ 70°) in the
  heliosphere. Data are presented from Helios 2, located 28° East of the
  Sun-Earth line at ~ 2/3 AU, and from near the Earth. Observations of
  the 2001 interval are from Wind. We examine the geomagnetic activity
  during each interval.

---------------------------------------------------------
Title: Effect of CME Interactions on the Production of Solar
    Energetic Particles
Authors: Gopalswamy, N.; Yashiro, S.; Michalek, G.; Kaiser, M. L.;
   Howard, R. A.; Leske, R.; von Rosenvinge, T.; Reames, D. V.
2003AIPC..679..608G    Altcode:
  We analyzed a set of 52 fast and wide, frontside western hemispheric
  (FWFW) CMEs in conjunction with solar energetic particle (SEP) and
  radio burst data and found that 42 of these CMEs were associated
  with SEPs. All but two of the 42 SEP-associated FWFW CMEs (95%)
  were interacting with preceding CMEs or dense streamers. Most of
  the remaining 10 SEP-poor FWFW CMEs had either insignificant or no
  interaction with preceding CMEs or streamers, and were ejected into
  a tenuous corona. There is also a close association between type II
  radio bursts in the near-Sun interplanetary medium and SEP-associated
  FWFW CMEs suggesting that electron accelerators are also good proton
  accelerators.

---------------------------------------------------------
Title: Coronal Shocks and Solar Energetic Proton Events
Authors: Cliver, Edward W.; Kahler, S. W.; Reames, D. V.
2003ICRC....6.3331C    Altcode: 2003ICRC...28.3331C
  From July 1996 June 2001, &lt; 50% of favorably-lo cated metric type I I
  radio bursts had associated solar energetic protons (SEPs). When western
  hemisphere metric I Is were accompanied by decametric-hectometric (DH;
  1-14 MHz) type I I emission, their association with ∼20 MeV SEP events
  was 90% vs. only 25% for metric I Is without a DH counterpart. Overall,
  82% (63%) of all SEP events with visible disk origins were associated
  with metric (DH) type I Is, with percentage associations increasing
  with SEP event size to 88% (96%), respectively, for ∼20 MeV SEP events
  with peak intensities ≥ 10-1 pr cm-2 s-1 sr-1 MeV-1 . Our results are
  consistent with the following (not mutually exclusive) possibilities:
  (1) large ∼20 MeV SEP events result from strong shocks that can
  persist well beyond ∼3 R ; (2) shock acceleration is most efficient
  above ∼3 R ; (3) shocks that survive to ∼3 R are more likely to
  have broad longitudinal extents.

---------------------------------------------------------
Title: Onsets and Release Times in Solar Particle Events
Authors: Tylka, A. J.; Cohen, C. M. S.; Dietrich, W. F.; Krucker, S.;
   McGuire, R. E.; Mewaldt, R. A.; Ng, C. K.; Reames, D. V.; Share, G. H.
2003ICRC....6.3305T    Altcode: 2003ICRC...28.3305T
  The time at which solar energetic particles (SEPs) are first released
  into interplanetary space, and its relation to CMEs and various
  photon emissions, are important clues to the site and nature of the
  SEP acceleration mechanism [15,7,8,10,11]. We examine velocity disp
  ersion among onsets in electrons and ions from Wind, ACE, and IMP8,
  as well as available neutron monitors, to determine the solar release
  time. We present results for two large impulsive events (1 May 2000
  and 14 April 2001) and three western ground level events (GLEs;
  6 November 1997, 6 May 1998, and 15 April 2001). In the impulsive
  events, the particle release coincides with hard x-ray emission. But
  the large GLEs show delayed release with respect to γ -ray emission,
  consistent with acceleration by the CME-driven shock.

---------------------------------------------------------
Title: Modeling Shock-accelerated Solar Energetic Particles Coupled
    to Interplanetary Alfvén Waves
Authors: Ng, C. K.; Reames, D. V.; Tylka, A. J.
2003ApJ...591..461N    Altcode:
  We present an idealized model simulating the coupled evolution of the
  distributions of multispecies shock-accelerated energetic ions and
  interplanetary Alfvén waves in gradual solar energetic particle (SEP)
  events. Particle pitch-angle diffusion coefficients are expressed in
  terms of wave intensities, and wave growth rates in terms of momentum
  gradients of SEP distributions, by the same quasilinear theory augmented
  with resonance broadening. The model takes into consideration various
  physical processes: for SEPs, particle motion, magnetic focusing,
  scattering by Alfvén waves, solar wind convection, and adiabatic
  deceleration; for the waves, WKB transport and amplification by
  streaming SEPs. Shock acceleration is heuristically represented
  by continuous injection of prescribed spectra of SEPs at a moving
  shock front. We show the model predictions for two contrasting sets
  of SEP source spectra, fast weakening and softening in one case and
  long lasting and hard in the other. The results presented include
  concurrent time histories of multispecies SEP intensities and elemental
  abundance ratios, as well as sequential snapshots of the following:
  SEP intensity energy spectra, Alfvén wave spectra, particle mean
  free paths as functions of rigidity, and spatial profiles of SEP
  intensities and mean free paths. Wave growth plays a key role in both
  cases, although the magnitude of the wave growth differs greatly,
  and quite different SEP abundance variations are obtained. In these
  simulations, the maximum wave growth rate is large, but small relative
  to the wave frequency, and everywhere the total wave magnetic energy
  density remains small relative to that of the background magnetic
  field. The simulations show that, as the energetic protons stream
  outward, they rapidly amplify the ambient Alfvén waves, by several
  orders of magnitude in the inner heliosphere. Energetic minor ions find
  themselves traveling through resonant Alfvén waves previously amplified
  by higher velocity protons. The nonuniformly growing wave spectra alter
  the rigidity dependence of particle scattering, resulting in complex
  time variations of SEP abundances at large distances from the Sun. The
  greatly amplified waves travel outward in an expanding and weakening
  “shell,” creating an expanding and falling “reservoir” of SEPs with
  flat spatial intensity profiles behind, while in and beyond the shell
  the intensities drop steeply. The wave-particle resonance relation
  dynamically links the evolving characteristics of the SEP and Alfvén
  wave distributions in this new mode of SEP transport. We conclude that
  wave amplification, the counterpart to the scattering of streaming
  particles required by energy conservation, plays an essential role in
  the transport of SEPs in gradual SEP events. The steep proton-amplified
  wave spectra just upstream of the shock suggest that they may also be
  important in determining the elemental abundances of shock-accelerated
  SEP sources.

---------------------------------------------------------
Title: Solar Energetic Particle Driven Alfvén Wave Growth and
    Consequences
Authors: Ng, Chee K.; Reames, D. V.; Tylka, A. J.
2003ICRC....6.3339N    Altcode: 2003ICRC...28.3339N
  Our model shows that in large solar energetic particle (SEP) events,
  streaming protons amplify interplanetary (IP) Alfv´n waves by orders
  of magnitude near e the Sun. The wave intensity varies strongly and
  non-monotonically in wavenumb er, time, and space. It falls steeply with
  distance and may be difficult to observe at 1 AU. Wave amplification
  dynamically modifies the rigidity and radial dependence of SEP
  scattering and throttles SEP transport. It is essential in understanding
  the time and energy variations of SEP elemental abundances.

---------------------------------------------------------
Title: A comparative analysis of the helios and istp era sun-earth
    connection during solar minimum
Authors: Berdichevsky, D.; Reames, D.; Schwenn, R.; Lepping, R.;
   Farrugia, C.; Richardson, I.; Wu, C. -C.
2003EAEJA....13892B    Altcode:
  We discuss the similarities and differences of two intervals of extreme
  interplanetary solar wind conditions, separated almost precisely by
  two solar cycles, in Feb-Apr 1976 and Jan-Apr 2001. The similarities
  extend to various data-sets: Energetic particles, solar wind plasma
  and interplanetary magnetic field. In Jan-April 1979 observations were
  made by spacecraft at three locations covering a wide longitudinal range
  (from ~30 to 70°) in the heliosphere. Data are presented from Helios 2,
  Helios 1, and from near the Earth. Observations of the 1997 interval are
  from Wind, and solar conditions from SOHO. We examine the geomagnetic
  activity during each interval. This Study is partially supported by the
  following Grants: ATM-0208414 (NSF), and NASA NASW-02025 and NAG 5-10883

---------------------------------------------------------
Title: Wind Observations of Anomalous Cosmic Rays from Solar Minimum
    to Maximum
Authors: Reames, D. V.; McDonald, F. B.
2003ApJ...586L..99R    Altcode:
  We report the first observation near Earth of the time behavior of
  anomalous cosmic-ray N, O, and Ne ions through the period surrounding
  the maximum of the solar cycle. These observations were made by the
  Wind spacecraft during the 1995-2002 period spanning times from solar
  minimum through solar maximum. Comparison of anomalous and Galactic
  cosmic rays provides a powerful tool for the study of the physics of
  solar modulation throughout the solar cycle.

---------------------------------------------------------
Title: Solar Energetic Particle Production by Coronal Mass
    Ejection-driven Shocks in Solar Fast-Wind Regions
Authors: Kahler, S. W.; Reames, D. V.
2003ApJ...584.1063K    Altcode:
  Gradual solar energetic particle (SEP) events at 1 AU are produced
  by coronal/interplanetary shocks driven by coronal mass ejections
  (CMEs). Fast (v<SUB>CME</SUB>&gt;~900 km s<SUP>-1</SUP>) CMEs might
  produce stronger shocks in solar slow-wind regions, where the flow and
  fast-mode MHD wave speeds are low, than in fast-wind regions, where
  those speeds are much higher. At 1 AU the O<SUP>+7</SUP>/O<SUP>+6</SUP>
  ratios distinguish between those two kinds of wind streams. We use
  the 20 MeV proton event intensities from the EPACT instrument on Wind,
  the associated CMEs observed with the LASCO coronagraph on SOHO, and
  the ACE SWICS solar wind values of O<SUP>+7</SUP>/O<SUP>+6</SUP>
  to look for variations of peak SEP intensities as a function
  of O<SUP>+7</SUP>/O<SUP>+6</SUP>. No significant dependence of
  the SEP intensities on O<SUP>+7</SUP>/O<SUP>+6</SUP> is found for
  either poorly connected or well-connected CME source regions or for
  different CME speed ranges. However, in the 3 yr study period we
  find only five cases of SEP events in fast wind, defined by regions
  of O<SUP>+7</SUP>/O<SUP>+6</SUP>&lt;0.15. We suggest that in coronal
  holes SEP acceleration may take place only in the plume regions, where
  the flow and Alfvén speeds are low. A broad range of angular widths
  are associated with fast (v<SUB>CME</SUB>&gt;=900 km s<SUP>-1</SUP>)
  CMEs, but we find that no fast CMEs with widths less than 60° are
  associated with SEP events. On the other hand, nearly all fast halo CMEs
  are associated with SEP events. Thus, the CME widths are more important
  in SEP production than previously thought, but the speed of the solar
  wind source regions in which SEPs are produced may not be a factor.

---------------------------------------------------------
Title: Unusual Plasma Conditions during may 23-25, 2002
Authors: Berdichevsky, D. B.; Lepping, R. P.; Bougeret, J.; Farrugia,
   C. J.; Perche, C.; Vinas, A. F.; Lacombe, C.; Maksimovic, M.; Reames,
   D. V.; Scudder, J. D.; Evans, D. S.
2002AGUFMSH72C..04B    Altcode:
  We present an overview of the plasma conditions under the extreme
  tenuous plasma (Ne &lt; 0.2 part/cm<SUP>3</SUP>) which started on May
  23, 2002 and lasted for almost three days. During this unusual interval
  at times the magnetosonic speed is well above 300 km/s, and unusual
  close values in the ratio of plasma to cyclotron electron frequencies
  (fpe/fce ~ 10). Using waves and solar wind parameters from the Wind
  WAVES, EPAC, MFI and SWE experiments, we compare this event with other
  intervals during this solar cycle which also showed strong hindrance in
  the flow of the interplanetary solar wind. We further inquire on the
  nature of the event by looking at the earth's polar cusps response to
  the solar wind conditions, as illustrated by observations by satellites
  POLAR and POES, and investigate, using flux-rope models and energetic
  particles, the nature of this intriguing interplanetary structure.

---------------------------------------------------------
Title: Flare- and Shock-accelerated Energetic Particles in the Solar
    Events of 2001 April 14 and 15
Authors: Tylka, A. J.; Boberg, P. R.; Cohen, C. M. S.; Dietrich,
   W. F.; Maclennan, C. G.; Mason, G. M.; Ng, C. K.; Reames, D. V.
2002ApJ...581L.119T    Altcode:
  We report heavy-ion composition and spectra for the solar
  energetic particle (SEP) events of 2001 April 14 and 15, using
  the combined capabilities of the Advanced Composition Explorer
  (ACE), Wind, and the Interplanetary Monitoring Platform 8 (IMP-8)
  to cover the energy range from ~30 keV nucleon<SUP>-1</SUP> to ~400
  MeV nucleon<SUP>-1</SUP>. These two events are, respectively, the
  largest impulsive event and the largest ground-level event observed
  so far in solar cycle 23. These events arose from the same active
  region and launched into similar interplanetary conditions. Both were
  associated with large western flares and fast coronal mass ejections
  (CMEs). However, the two events are distinctly different, thereby
  providing useful reminders of the fundamental differences between flare-
  and shock-accelerated SEPs. The detailed observations present challenges
  for our theoretical understanding of SEP production. Of particular
  note is the fact that iron has a harder power-law energy spectrum than
  oxygen above ~3 MeV nucleon<SUP>-1</SUP> in the shock-dominated April
  15 event. This spectral difference, which is seen in many other gradual
  events of various sizes and heliolongitudes, leads to enhanced Fe/O
  at high energies. Simple shock acceleration models predict the same
  power-law index for all species. Thus, understanding the origin of this
  spectral difference will significantly contribute to the resolution
  of the ongoing debate about the relative roles of CME-driven shocks
  and flares in producing high-energy solar heavy ions.

---------------------------------------------------------
Title: Rise Times of Solar Energetic Particle Events and Speeds
    of CMEs
Authors: Kahler, S.; Reames, D.
2002AGUFMSH62A..08K    Altcode:
  Gradual solar energetic particle (SEP) events are assumed to be
  produced in coronal and interplanetary shocks driven by fast coronal
  mass ejections (CMEs). These fast CMEs are decelerated as they move
  through the slower ambient solar wind. However, the Alfven speed is
  decreasing with increasing distance. Faster CMEs may therefore continue
  to drive strong shocks for longer characteristic times than do the
  slower CMEs, such that shock production and injection of SEPs of a
  given energy will also continue longer with the faster CMEs. We test
  this proposition observationally by comparing the times to maxima of 20
  MeV SEP events with the observed speeds of associated CMEs. The SEP/CME
  events are sorted by solar longitude to factor out the longitudinal
  dependence of the SEP rise times. A preliminary analysis comparing 20
  MeV protons from the GSFC EPACT detector on the Wind satellite with
  CMEs observed by the LASCO coronagraph on the SOHO spacecraft showed
  a correlation between SEP rise times and CME speeds. We expand the
  database to include the 1996-2001 period for a more definitive test
  of the correlation. The implications of the results will be discussed.

---------------------------------------------------------
Title: Angular Distributions of Fe/O from Wind: New Insight into
    Solar Energetic Particle Transport
Authors: Reames, D. V.; Ng, C. K.
2002ApJ...577L..59R    Altcode:
  We examine the angular distributions of He, O, and Fe in large solar
  energetic particle (SEP) events measured on the Wind spacecraft. We
  report, for the first time, that in a fixed velocity interval, Fe/O
  is often larger for particles flowing sunward along the magnetic
  field than for particles flowing outward from the Sun in many SEP
  events. This occurs because the anisotropy for O exceeds that for Fe,
  even though both species are streaming outward. There are no examples
  of events for which the outward Fe/O dominates. The behavior of Fe
  and O conflicts with the expectations of simple diffusion theory,
  that angular distributions should be independent of species. It also
  seems to conflict with the idea that energetic Fe scatters less than O
  of the same velocity. However, preliminary modeling suggests that the
  presence of a reflecting magnetic boundary beyond 1 AU, together with
  the increased scattering of O over Fe due to proton-generated Alfvén
  waves, can explain the direction and magnitude of the effect. These
  observations add a new dimension to the study of SEP transport.

---------------------------------------------------------
Title: Energetic Particle Abundances as Probes of an Interplanetary
    Shock Wave
Authors: Reames, D. V.; Tylka, A. J.
2002ApJ...575L..37R    Altcode:
  We examine the unique abundance variations of Fe/O and He/H in solar
  energetic particles from a W09 event of 2001 April 10 that have leaked
  through the flank of an interplanetary shock launched from W04 on April
  9. Shock waves from both events reached the Wind spacecraft on April
  11. During the second event, both Fe/O and He/H began at low values and
  rose to maxima near the time of passage of the shock waves, indicating
  greater scattering for the species with the highest rigidity at a given
  velocity. Strong modulation of Fe/O suggests preferential scattering
  and trapping of Fe by the wave spectrum near and behind the intermediate
  shock. A significant factor may be the residual proton-generated waves
  from the very hard proton spectrum accelerated by the early shock wave
  prior to the onset of the second event. Thus, ion abundances from the
  later event probe the residual wave spectrum at the earlier shock.

---------------------------------------------------------
Title: Relative recovery of galactic and anomalous cosmic rays at
1 AU: Further evidence for modulation in the heliosheath
Authors: McDonald, F. B.; Klecker, B.; McGuire, R. E.; Reames, D. V.
2002JGRA..107.1156M    Altcode:
  For solar cycle 22 the large-scale interplanetary disturbances produced
  by the intense solar activity of March/June 1991 had a long-term effect
  on the recovery of galactic cosmic rays throughout the heliosphere that
  persisted for almost 5 years. At 1 AU, the recovery of 13 MeV/nucleon
  anomalous cosmic ray oxygen (ACR O<SUP>+</SUP>) is much more rapid
  than that of 265 MeV/nucleon galactic cosmic ray helium (GCR He),
  consistent with previous observations in the distant heliosphere
  [McDonald et al., 2000] and strengthening the concept that the
  region of the heliosheath plays an important role in the modulation
  of galactic cosmic rays. A comparison of the time histories of GCR
  He and ACR O<SUP>+</SUP> at 1 and 44 AU observations suggest the
  recovery moves from the distant heliosphere inward toward 1 AU for
  this particular phase of the heliomagnetic cycle. There is a very low
  relative modulation potential, Φ, between 1 and 70 AU of 116 +/- 6 MV
  for GCR He at solar minimum using the force field approximation. When
  combined with the small radial intensity gradients in the distant
  heliosphere, a much lower modulation potential is implied between 1
  AU and the termination shock at solar minimum than had been assumed
  previously. There is no effect on the 13 MeV/nucleon ACR O<SUP>+</SUP>
  intensity as the inclination of the heliospheric neutral current sheet
  decreases from 32° to its minimum value of 8°.

---------------------------------------------------------
Title: Halo-coronal mass ejections near the 23rd solar minimum:
    lift-off, inner heliosphere, and in situ (1 AU) signatures
Authors: Berdichevsky, D. B.; Farrugia, C. J.; Thompson, B. J.;
   Lepping, R. P.; Reames, D. V.; Kaiser, M. L.; Steinberg, J. T.;
   Plunkett, S. P.; Michels, D. J.
2002AnGeo..20..891B    Altcode:
  The extreme ultraviolet (EUV) signatures of a solar lift-off, decametric
  and kilometric radio burst emissions and energetic particle (EP)
  inner heliospheric signatures of an interplanetary shock, and in
  situ identification of its driver through solar wind observations
  are discussed for 12 isolated halo coronal mass ejections (H-CMEs)
  occurring between December 1996 and 1997. For the aforementioned twelve
  and the one event added in the discussion, it is found that ten passed
  several necessary conditions for being a "Sun-Earth connection". It
  is found that low corona EUV and Ha

---------------------------------------------------------
Title: Interacting Coronal Mass Ejections and Solar Energetic
    Particles
Authors: Gopalswamy, N.; Yashiro, S.; Michałek, G.; Kaiser, M. L.;
   Howard, R. A.; Reames, D. V.; Leske, R.; von Rosenvinge, T.
2002ApJ...572L.103G    Altcode:
  We studied the association between solar energetic particle (SEP) events
  and coronal mass ejections (CMEs) and found that CME interaction is
  an important aspect of SEP production. Each SEP event was associated
  with a primary CME that is faster and wider than average CMEs and
  originated from west of E45°. For most of the SEP events, the primary
  CME overtakes one or more slower CMEs within a heliocentric distance of
  ~20 R<SUB>solar</SUB>. In an inverse study, we found that for all the
  fast (speed greater than 900 km s<SUP>-1</SUP>) and wide (width greater
  than 60°) western hemispheric frontside CMEs during the study period,
  the SEP-associated CMEs were ~4 times more likely to be preceded by
  CME interaction than the SEP-poor CMEs; i.e., CME interaction is a
  good discriminator between SEP-poor and SEP-associated CMEs. We infer
  that the efficiency of the CME-driven shocks is enhanced as they
  propagate through the preceding CMEs and that they accelerate SEPs
  from the material of the preceding CMEs rather than from the quiet
  solar wind. We also found a high degree of association between major
  SEP events and interplanetary type II radio bursts, suggesting that
  proton accelerators are also good electron accelerators.

---------------------------------------------------------
Title: Solar Energetic Particle Production by Shocks in Fast and
    Slow Solar Wind Structures
Authors: Kahler, S. W.; Reames, D. V.; Sheeley, N. R., Jr.
2002AAS...200.3702K    Altcode: 2002BAAS...34..694K
  Gradual solar energetic particle (SEP) events at 1 AU are produced
  by coronal and interplanetary shocks driven by coronal mass ejections
  (CMEs). Shocks from fast (V &gt; 900 km/s) CMEs should be produced more
  easily in slow solar wind regions where the flow and fast-mode MHD wave
  speeds are low and less easily in fast solar wind regions where those
  speeds are high. We might therefore expect to observe more intense SEP
  events at 1 AU when the Earth lies in a slow wind region than when it
  lies in a fast wind region. While stream-stream interactions wash out
  the slow-fast stream boundaries in the solar wind speed profiles at
  1 AU, the O+7/O+6 signatures of the streams are unchanged at 1 AU. We
  use the 20 MeV proton intensities from the EPACT instrument on Wind,
  the associated CMEs observed with the Lasco coronagraph on SOHO,
  and the ACE SWICS/SWIMS solar wind values of O+7/O+6 to look for
  variations of peak SEP intensities as a function of O+7/O+6. We find
  no significant dependence of the SEP intensities on O+7/O+6 for either
  poorly connected or well connected CME source regions or for different
  CME speed ranges. While a broad range of angular widths are associated
  with fast (V &gt; 900 km/s) CMEs, we find that no fast CMEs with widths
  &lt; 60 degrees are associated with SEP events. On the other hand,
  nearly all fast halo CMEs are associated with SEP events. Thus the CME
  widths are more important in SEP production than previously thought,
  but the solar wind source regions in which SEPs are produced are not
  a significant factor.

---------------------------------------------------------
Title: Variability in Elemental Composition in Large Solar Particle
    Events of Cycle 23
Authors: Tylka, A. J.; Boberg, P. R.; Cohen, C. M.; Dietrich, W. F.;
   Maclennan, C. G.; Mason, G. M.; Ng, C. K.; Reames, D. V.
2002AGUSMSH42B..05T    Altcode:
  Through December 2001, Cycle 23 has produced ~45 large solar
  energetic particle (SEP) events, in which the proton intensity above
  10 MeV exceeds galactic background rates by a factor of at least
  10<SUP>4</SUP>. We use these events to make a systematic study of SEP
  elemental composition in Cycle 23. Preliminary results show no strong
  evidence for systematic differences between the early and later phases
  of Cycle 23, at least in data at ~5-10 MeV/nucleon, the same energy
  range as used for most previous studies of SEP composition. However,
  comparing events over the wide range of energies covered by various
  instruments on Wind and ACE reveals a number of acceleration, transport,
  and seed population effects which are strongly dependent on the species'
  charge-to-mass (Q/A) ratio. We will discuss these effects and their
  potential importance for understanding the relative roles of flares and
  fast CMEs in producing large SEP events. We will also compare results
  from Cycle 23 with elemental composition results from Cycles 21 and 22.

---------------------------------------------------------
Title: Influence of CME Interaction on Solar Proton Events During
    Cycle 23
Authors: Gopalswamy, N.; Yashiro, S.; Michalek, G.; Kaiser, M. L.;
   Howard, R. A.; Reames, D. V.; Leske, R. A.; Von Rosenvinge, T.
2002AGUSMSH41A..06G    Altcode:
  We studied the association between solar proton events and white-light
  coronal mass ejections (CMEs) that occurred during the solar cycle
  23 until November 2001. Each of the SEP events was associated with
  a large-scale primary CME, that were faster and wider than average
  CMEs. For most of the proton events, the primary CME overtakes one or
  more slower CMEs. In order to confirm this result, we examined the
  association and CME interaction and energetic proton events for all
  the fast (speed &gt; 900 km~s<SUP>-1</SUP>) and wide (width &gt; 60
  deg) western hemispheric and halo CMEs during the study period. CMEs
  with energetic protons are 3 times more likely to be preceded by CME
  interaction than those without. We conclude that CME interaction is an
  important aspect of SEP acceleration. We infer that CME-driven shocks
  accelerate SEPs from the material of the preceding CMEs rather than
  from the quiet solar wind.

---------------------------------------------------------
Title: Magnetic Topology of Impulsive and Gradual Solar Energetic
    Particle Events
Authors: Reames, Donald V.
2002ApJ...571L..63R    Altcode:
  We examine the magnetic topology at the Sun that leads to the two
  classes of impulsive and gradual solar energetic particle (SEP)
  events so as to address new observations that seem to blur this
  classification, for example, that coronal mass ejections (CMEs) can
  accompany events of both classes. In our model, the unusual element
  abundances in impulsive SEP events result from resonant stochastic
  acceleration in magnetic reconnection regions that incorporate open
  magnetic field lines, allowing both accelerated ions and ejected
  plasma to escape. In the large gradual events that produce classic
  CMEs, reconnection occurs on closed field lines beneath the CME where
  the accelerated particles are trapped so they plunge into the solar
  atmosphere to produce a flare; they cannot escape. The SEPs seen at
  1 AU in these large gradual events are accelerated by the shock wave
  driven outward by the CME. The shock-accelerated particles are derived
  from the local plasma and from reaccelerated suprathermal ions from
  previous impulsive or gradual SEP events.

---------------------------------------------------------
Title: A comparative study of Solar-Heliospheric Observations during
    very active Sun intervals in the 21st and 23rd solar cycles (April
    1979 and March-April, 2001)
Authors: Berdichevsky, D. B.; Farrugia, C. J.; Lepping, R. P.;
   Richardson, I. G.; Galvin, A. B.; Schwenn, R.; Reames, D. V.
2002AGUSMSH51A..01B    Altcode:
  On March 24, 2001, the largest sun spot group in 10 years, consisting
  of three or more active regions (ARs) centered near AR 9393, emerged
  from behind the eastern limb of the Sun and began a 2-week passage
  across the visible hemisphere. During the same time, the Sun showed
  several other ARs so this period constituted a phase of unusually
  intense solar activity that continued almost 18 days beyond the
  disk passage of the largest sun spot group and included possibly
  the most energetic solar flare event in modern records (a &gt; X20
  flare in soft X-rays). We shall present an overview of the associated
  solar energetic particle events and an analysis of the thermodynamic
  characteristics of the shocks observed in the Earth's vicinity. The
  investigation includes cross-correlation analysis of interplanetary
  plasma and magnetic field observations at ACE (SWEPAM/MAG level-2 data)
  situated 250 Re upstream of Earth and at Wind (SWE/MFI data), which
  was ahead of Earth and executing a distant prograde orbit with large
  Y-coordinate. The interval under study bears a close resemblance to a
  similar active period during April 1979 (i.e., 2 solar cycles earlier)
  observed by the Helios 1/2 probes and Earth solar wind monitors (ISEE-3,
  IMP). The similarities and differences between the two intervals are
  examined further.

---------------------------------------------------------
Title: Colliding coronal mass ejections and particle acceleration
Authors: Gopalswamy, N.; Yashiro, S.; Kaiser, M.; Reames, D.;
   Howard, R.
2002cosp...34E1253G    Altcode: 2002cosp.meetE1253G
  Colliding Coronal Mass Ejections (CMEs) have important implications to
  a number of physical processes in the near-Sun interplanetary medium:
  Shock propagation, particle acceleration and solar wind composition. We
  present statistical results on large solar energetic particle events,
  associated CMEs and CME interaction during solar cycle 23. We show
  that most of the large SEP events are preceded by CME interaction. As
  an inverse study, we identified all the fast and wide front side CMEs
  from the western hemisphere and examined the SEP association and
  CME interaction. We found that fast and wide CMEs interacting with
  preceding CMEs are more likely to be associated with SEPs. We discuss
  the implications of the statistical results to the understanding of
  particle acceleration by CME-driven shocks.

---------------------------------------------------------
Title: Solar Wind: Energetic Particles
Authors: Reames, D.
2002eaa..bookE2312R    Altcode:
  The energetic particle populations that we observe in the SOLAR
  WIND are accelerated in a variety of local and distant sources. We
  distinguish different populations by their temporal, spatial and angular
  distributions, energy spectra, abundances and ionization states. They
  tell us the physics of acceleration mechanisms and the properties of
  remote sites that are otherwise invisible or inaccessibl...

---------------------------------------------------------
Title: Solar energetic particle variations
Authors: Reames, D.
2002cosp...34E.491R    Altcode: 2002cosp.meetE.491R
  In recent years we have learned that in the largest solar energetic
  particle (SEP) events, acceleration occurs at shock waves driven out
  from the Sun by coronal mass ejections (CMEs). In fact, the highest
  proton intensities directly measured near Earth at energies below
  ~1 GeV occur at the time of passage of shocks, which arrive about a
  day after the CMEs leave the Sun. CME-driven shocks can expand across
  magnetic fields to fill more than half of the heliosphere with SEPs;
  intensity-time profiles of the SEPs depend upon the observer's location
  relative to the CME source. Proton-generated Alfven waves trap particles
  near the shock for efficient acceleration but also bound intensities
  near Earth at the "streaming limit" early in the events. At high
  energies, particles begin to leak from the shock and the spectrum rolls
  downward to form an energy-spectral "knee." Knee energies can vary from
  ~10 MeV to ~1 GeV in different SEP events. All of these factors affect
  the radiation dose as a function of depth and latitude in the Earth's
  atmosphere and the risk to astronauts and equipment in space. Direct
  observations of SEP events show a rough correlation with the solar
  cycle for the last ~40 years. Observations of nitrate deposits in ice
  cores (~400 y) and radioactive isotopes in moon rocks (~1 My) extend
  the historic record and address the probability of occurrence of much
  larger SEP events.

---------------------------------------------------------
Title: The Bastille day Magnetic Clouds and Upstream Shocks:
    Near-Earth Interplanetary Observations
Authors: Lepping, R. P.; Berdichevsky, D. B.; Burlaga, L. F.; Lazarus,
   A. J.; Kasper, J.; Desch, M. D.; Wu, C. -C.; Reames, D. V.; Singer,
   H. J.; Smith, C. W.; Ackerson, K. L.
2001SoPh..204..285L    Altcode:
  The energetic charged particle, interplanetary magnetic field, and
  plasma characteristics of the `Bastille Day' shock and ejecta/magnetic
  cloud events at 1 AU occurring over the days 14-16 July 2000 are
  described. Profiles of MeV (WIND/LEMT) energetic ions help to organize
  the overall sequence of events from the solar source to 1 AU. Stressed
  are analyses of an outstanding magnetic cloud (MC2) starting late on
  15 July and its upstream shock about 4 hours earlier in WIND magnetic
  field and plasma data. Also analyzed is a less certain, but likely,
  magnetic cloud (MC1) occurring early on 15 July; this was separated
  from MC2 by its upstream shock and many heliospheric current sheet
  (HCS) crossings. Other HCS crossings occurred throughout the 3-day
  period. Overall this dramatic series of interplanetary events caused
  a large multi-phase magnetic storm with min Dst lower than −300
  nT. The very fast solar wind speed (≥ 1100 km s<SUP>−1</SUP>)
  in and around the front of MC2 (for near average densities) was
  responsible for a very high solar wind ram pressure driving in the
  front of the magnetosphere to geocentric distances estimated to be as
  low as ≈ 5 R<SUB>E</SUB>, much lower than the geosynchronous orbit
  radius. This was consistent with magnetic field observations from two
  GOES satellites which indicated they were in the magnetosheath for
  extended times. A static force-free field model is used to fit the two
  magnetic cloud profiles providing estimates of the clouds' physical
  and geometrical properties. MC2 was much larger than MC1, but their
  axes were nearly antiparallel, and their magnetic fields had the same
  left-handed helicity. MC2's axis and its upstream shock normal were
  very close to being perpendicular to each other, as might be expected
  if the cloud were driving the shock at the time of observation. The
  estimated axial magnetic flux carried by MC2 was 52×10<SUP>20</SUP>
  Mx, which is about 5 times the typical magnetic flux estimated for
  other magnetic clouds in the WIND data over its first 4 years and is
  17 times the flux of MC1. This large flux is due to both the strong
  axially-directed field of MC2 (46.8 nT on the axis) and the large
  radius (R<SUB>0</SUB>=0.189 AU) of the flux tube. MC2's average speed
  is consistent with the expected transit time from a halo-CME to which
  it is apparently related.

---------------------------------------------------------
Title: On the Phase of the 27 Day Modulation of Anomalous and Galactic
    Cosmic Rays at 1 AU during Solar Minimum
Authors: Reames, D. V.; Ng, C. K.
2001ApJ...563L.179R    Altcode:
  We report on the 27 day oscillations in the intensities of He and O
  ions of the anomalous cosmic rays (ACRs) observed near Earth by the
  Wind spacecraft during the 1995-1997 solar minimum period. Oscillations
  persist throughout the period with amplitudes as large as 50%. Galactic
  cosmic ray (GCR) oscillations, observed by neutron monitors, are in
  phase with the ACRs, but with much smaller amplitude (2%-3%). For
  a sustained period of almost a year, peak intensities occur near
  north-to-south crossings of the heliospheric current sheet and
  valleys near south-to-north crossings. In GCR observations in the
  1974-1976 solar minimum, 27 day oscillations with a similar phase
  are seen. Understanding these observations poses a severe challenge
  for models of solar modulation as well as for models of the solar and
  heliospheric magnetic fields.

---------------------------------------------------------
Title: Coronal Mass Ejections Associated with Impulsive Solar
    Energetic Particle Events
Authors: Kahler, S. W.; Reames, D. V.; Sheeley, N. R., Jr.
2001ApJ...562..558K    Altcode:
  An impulsive solar energetic particle (SEP) event observed on the
  Wind spacecraft on 2000 May 1 was associated with an impulsive solar
  active region M1 X-ray flare. The timing and position of a fast (v=960
  km s<SUP>-1</SUP>), narrow CME observed in the LASCO coronagraph on
  SOHO make clear the connection between the CME and the flare and SEP
  event. Impulsive SEP events have long been associated with impulsive
  flares, but only gradual SEP events have thus far been found to be
  associated with CMEs. A comparison of impulsive SEP events with CME
  observations from the Solwind and LASCO coronagraphs revealed further
  good cases of narrow (10°-40°) CMEs associated with impulsive SEP
  events. A recent model of impulsive flares includes jets or plasmoids
  that are ejected upward from magnetic reconnection sites over active
  regions and might therefore be expected to appear in exceptional
  cases as faint and narrow CMEs in coronagraphs. We suggest that this
  model allows us to understand better SEP production and propagation
  in impulsive flares.

---------------------------------------------------------
Title: Energetic particle composition
Authors: Reames, Donald V.
2001AIPC..598..153R    Altcode: 2001sgc..conf..153R
  Abundances of elements and isotopes have been essential for identifying
  and measuring the sources of the energetic ions and for studying the
  physical processes of acceleration and transport for each particle
  population in the heliosphere. Many of the sources are surprising, in
  a few cases the acceleration bias is extreme, but an understanding of
  the fundamental physics allows us to use energetic ions to determine
  abundances for the average solar corona, the high-speed solar wind,
  and the local interstellar medium. .

---------------------------------------------------------
Title: Evidence for Remnant Flare Suprathermals in the Source
    Population of Solar Energetic Particles in the 2000 Bastille Day Event
Authors: Tylka, A. J.; Cohen, C. M. S.; Dietrich, W. F.; Maclennan,
   C. G.; McGuire, R. E.; Ng, C. K.; Reames, D. V.
2001ApJ...558L..59T    Altcode:
  The energy spectra of Fe in the very large solar energetic particle
  (SEP) event of 2000 July 14 are strikingly different from those
  of lighter species. We show that this difference can be explained
  by shock acceleration from a two-component source population,
  comprising solar wind suprathermals and a small (~5%) admixture of
  remnant flare particles, as previously proposed to explain enhanced
  <SUP>3</SUP>He/<SUP>4</SUP>He in some gradual SEP events. Flare
  remnants can also account for several previously unexplained features
  of high-energy solar heavy ions as well as important aspects of SEP
  event-to-event variability. These results offer a new perspective on
  the enduring controversy over the relative roles of flares and coronal
  mass ejections (CMEs) in producing SEPs. Flare activity clearly makes
  a unique and critical contribution to the source population. But
  the predominate accelerator in large gradual SEP events is the
  CME-driven shock, and many spectral, compositional, and charge state
  characteristics of high-energy heavy ions can be understood without
  invoking other acceleration mechanisms.

---------------------------------------------------------
Title: A Comparative Study of the Cosmic Ray Recovery Process in
    the Inner and Outer Heliosphere
Authors: McDonald, F. B.; Klecker, B.; McGuire, R. E.; Reames, D. V.
2001ICRC....9.3762M    Altcode: 2001ICRC...27.3762M
  The cosmic ray recovery of galactic and anomalous cosmic rays for cycle
  22 over the 1991-1997 time period is strongly affected by the intense
  solar activity of March/June 1991. This results in a recovery that
  differ from that of cycle 20 and both in turn differs significantly
  from the cycle 21 recovery (1981-1987) in a qA&lt;0 epoch. For cycle 22
  it is found that the recovery time constants for 265 MeV/n GCR He are
  the same at 1 and 44 AU (τ = 1.9 years) which is much longer than the
  0.95 year time constant measured at these distances for ACR 0+ . This
  has previously been interpreted as evidence for cosmic ray modulation
  in the heliosheath. There is no evidence for similar effects in cycle
  21 following the large outburst of solar activity in mid 1982. What
  is most puzzling about the cycle 22 recovery is that the net increase
  in 150-380 MeV/n He between 1990 and 1997 is the same at 1 AU and at
  44 AU. However, for ACR 0+ the net increase at 44 AU is appreciably
  larger than at 1 AU. This analysis suggests that after 1993.2 (i.e.,
  following the passage of the global merged interaction region produced
  by the March/June activity) the continuing recovery of galactic cosmic
  rays proceed from the outer into the inner heliosphere. Again, this is
  different from the 1982 - 1987 recovery which appeared to be strongly
  controlled by changes in the inclination of the heliospheric neutral
  current sheet (HNCS).

---------------------------------------------------------
Title: Abundances, spectra, and anisotropies in the 1998 Sep 30 and
    2000 Apr 4 large Sep events
Authors: Ng, C. K.; Reames, D.; Tylka, A. J.
2001ICRC....8.3140N    Altcode: 2001ICRC...27.3140N
  The 1998 Sep 30 and 2000 Apr 4 events are both large western solar
  energetic particle (SEP) events, in which ∼ 1 MeV proton intensities
  exceed 103 particles (cm2 s sr MeV)-1 . Yet they exhibit quite different
  time variations of elemental abundance ratios and energy spectra. Using
  a model of SEP transport through self-amplified interplanetary Alfv´en
  waves, we fit the simultaneous observations of protons and ions of
  helium, oxygen, and iron. We conclude that wave amplification by high
  energy protons largely account for the differences in the observed
  time histories.

---------------------------------------------------------
Title: A CME associated with an impulsive SEP event
Authors: Kahler, S.; Reames, D.; Sheeley, N., Jr.
2001ICRC....8.3443K    Altcode: 2001ICRC...27.3443K
  An impulsive solar energetic particle (SEP) event observed on the Wind
  spacecraft on 2000 May 1 was associated with an impulsive solar active
  region M1 X-ray flare. The timing and position of a fast (v = 960 km s-1
  ), narrow CME observed in the Lasco coronagraph on SOHO make clear the
  connection between the CME and the flare and SEP event. Impulsive SEP
  events have long been associated with impulsive flares, but only gradual
  SEP events have thus far been found to be associated with CMEs. This is
  the first clear case of an impulsive SEP event with an associated CME.

---------------------------------------------------------
Title: Energy Spectra of Very Large Gradual Solar Particle Events
Authors: Tylka, A. J.; Boberg, P. R.; Cohen, C. M. S.; Dietrich,
   W. F.; Maclennan, C. G.; Mason, G. M.; Reames, D. V.; McGuire, R. E.;
   Ng, C. K.
2001ICRC....8.3189T    Altcode: 2001ICRC...27.3189T
  Energy spectra provide a powerful tool in understanding solar energetic
  particle (SEP) events, in that spectra contain information on all
  aspects of SEP production, including source plasma, interplanetary
  transport effects, and characteristics of the accelerator. We compare
  energy spectra of two very large gradual events (1998 April 20 and
  2000 July 14), produced by shocks driven by fast coronal mass ejections
  (CMEs). We show that differences in their Fe spectra can be understood
  in terms of a small, variable admixture of remant flare suprathermals
  in the SEP source population.

---------------------------------------------------------
Title: Associations of Accelerating CMEs with Solar Energetic
    Particle Events
Authors: Kahler, S.; Sheeley, N.; Reames, D.
2001AGUSM..SH22B03K    Altcode:
  Gradual solar energetic particle (SEP) events are well associated with
  fast coronal mass ejections (CMEs). The times of significant E &gt;
  10 MeV SEP events observed with the Goddard Space Flight Center EPACT
  detector on the Wind spacecraft have been compared with CME observations
  from the Lasco coronagraph on the SOHO spacecraft. As earlier studies
  have shown, a correlation exists between peak SEP intensities and
  the measured speeds of associated CMEs. Of the CMEs associated with
  SEP events in the period 1996 to 2000, we find 9 CMEs for which the
  height-time plots of the leading edges show accelerations of at least
  13 m/s/s. The heights at which those CMEs attained speeds of 600 km/s
  ranged from 7 to 20 Ro. The peak 20 MeV intensities of the 9 SEP events
  are relatively low compared with all gradual SEP events of the same
  period. We compare the energy spectra and solar event associations of
  these 9 SEP events with those of the SEP events associated with CMEs
  of uniform speeds.

---------------------------------------------------------
Title: Angular Distributions of Solar Energetic Particles
Authors: Reames, D. V.; Ng, C. K.; Berdichevsky, D.
2001ApJ...550.1064R    Altcode:
  We report observations, using data from the Wind spacecraft, of temporal
  variations in the angular distributions of H, He, O, and Fe ions at MeV
  energies during solar energetic particle (SEP) events under a variety
  of conditions. Detailed time-dependent angular distributions of O
  and Fe during SEP events are reported for the first time. Extended
  periods of particle streaming in small gradual events are consistent
  with continued acceleration that is expected at shock waves driven from
  the Sun by coronal mass ejections (CMEs). Particles accelerated from
  SEP events of moderate size show especially strong streaming along the
  magnetic fields inside an old CME. For the largest events, however,
  streaming rapidly diminishes, showing behavior that is qualitatively
  consistent with the theory of Ng et al. In very intense events, that
  theory predicts rapid growth of proton-generated Alfvén waves, even
  near and beyond 1 AU, that soon scatter and isotropize the particles. We
  show, for the first time, cases where SEP streaming is organized by
  the value of the plasma beta β<SUB>p</SUB>, the ratio of the proton
  thermal energy to magnetic energy. Higher initial turbulence in the
  high-β<SUB>p</SUB> plasma may require less additional wave growth to
  reach significant levels of scattering in the largest SEP events.

---------------------------------------------------------
Title: Heavy Ion Abundances and Spectra and the Large Gradual Solar
    Energetic Particle Event of 2000 July 14
Authors: Reames, D. V.; Ng, C. K.; Tylka, A. J.
2001ApJ...548L.233R    Altcode:
  We compare the spectra and abundances of heavy elements of atomic
  number Z in the range 34&lt;=Z&lt;=40 with those of He, C, O, Ne, Si,
  and Fe, as observed on the Wind spacecraft, in the large solar energetic
  particle (SEP) events of 1998 April 20 and 2000 July 14. This is the
  first time that spectra of the rare, trans-Fe, 34&lt;=Z&lt;=40 ions
  have been measured in SEP events. We use the systematic dependence of
  the spectral e-folding energies on the charge-to-mass ratio (Q/A) of
  the species to estimate ionization states of each species. Ionization
  states of Q~11 for ions with 34&lt;=Z&lt;=40 are comparable to those
  for Si and Fe.

---------------------------------------------------------
Title: Solar energetic particles and space weather
Authors: Reames, Donald V.; Tylka, Allan J.; Ng, Chee K.
2001AIPC..552.1185R    Altcode: 2001stai.conf.1185R
  The solar energetic particles (SEPs) of consequence to space weather
  are accelerated at shock waves driven out from the Sun by fast coronal
  mass ejections (CMEs). In the large events, these great shocks fill
  half of the heliosphere. SEP intensity profiles change appearance with
  longitude. Events with significant intensities of &gt;10 MeV protons
  occur at an average rate of ~13 yr<SUP>-1</SUP> near solar maximum
  and several events with high intensities of &gt;100 MeV protons occur
  each decade. As particles stream out along magnetic field lines from
  a shock near the Sun, they generate waves that scatter subsequent
  particles. At high intensities, wave growth throttles the flow
  below the “streaming limit.” However, if the shock maintains its
  strength, particle intensities can rise above this limit to a peak
  when the shock itself passes over the observer creating a `delayed'
  radiation hazard, even for protons with energies up to ~1 GeV. The
  streaming limit makes us blind to the intensities at the oncoming
  shock, however, heavier elements such as He, O, and Fe probe the shape
  of the wave spectrum, and variation in abundances of these elements
  allow us to evade the limit and probe conditions at the shock, with
  the aid of detailed modeling. At high energies, spectra steepen to
  form a spectral `knee.' The location of the proton spectral knee can
  vary from ~10 MeV to ~1 GeV, depending on shock conditions, greatly
  affecting the radiation hazard. Hard spectra are a serious threat to
  astronauts, placing challenging requirements for shielding, especially
  on long-duration missions to the moon or Mars. .

---------------------------------------------------------
Title: The observational consequences of proton-generated waves
    at shocks
Authors: Reames, Donald V.
2000AIPC..528...79R    Altcode: 2000atep.conf...79R
  In the largest solar energetic particle (SEP) events, acceleration
  takes place at shock waves driven out from the Sun by fast coronal
  mass ejections. Protons streaming away from strong shocks generate
  Alfvén waves that trap particles in the acceleration region, limiting
  outflowing intensities but increasing the efficiency of acceleration
  to higher energies. Early in the events, with the shock still near
  the Sun, intensities at 1 AU are bounded and spectra are flattened
  at low energies. Elements with different charge-to-mass ratios, Q/A,
  differentially probe the wave spectra near shocks, producing abundance
  ratios that vary in space and time. An initial rise in He/H, while Fe/O
  declines, is a typical symptom of the non-Kolmogorov wave spectra in the
  largest events. Strong wave generation can cause cross-field scattering
  near the shock and unusually rapid reduction in anisotropies even far
  from the shock. At the highest energies, shock spectra steepen to form
  a “knee.” For protons, this spectral knee can vary from ~10 MeV to
  ~1 GeV depending on shock conditions for wave growth. In one case, the
  location of the knee scales approximately as Q/A in the energy/nucleon
  spectra of other species. .

---------------------------------------------------------
Title: Abundances of Trans-Iron Elements in Solar Energetic Particle
    Events
Authors: Reames, Donald V.
2000ApJ...540L.111R    Altcode:
  We report the first comprehensive observation of the abundances
  of heavy elements of atomic number Z in the range 34&lt;=Z&lt;=82
  in solar energetic particle (SEP) events as observed on the Wind
  spacecraft. In large gradual SEP events, abundances of the element
  groups 34&lt;=Z&lt;=40, 50&lt;=Z&lt;=56, and 70&lt;=Z&lt;=82, relative
  to Fe, are similar to corresponding coronal abundances within a factor
  of ~2 and vary little with time during the events. However, in sharp
  contrast, abundances of these ions from impulsive flares increase
  dramatically with Z so that abundances of Fe, 34&lt;=Z&lt;=40, and
  50&lt;=Z&lt;=56, relative to O, are seen at ~10, ~100, and ~1000 times
  their coronal values, respectively.

---------------------------------------------------------
Title: Temporal evolution in the spectra of gradual solar energetic
    particle events
Authors: Tylka, Allan J.; Boberg, Paul. R.; McGuire, Robert. E.; Ng,
   Chee K.; Reames, Donald. V.
2000AIPC..528..147T    Altcode: 2000atep.conf..147T
  We examine solar energetic particle (SEP) spectra in two very large
  “gradual” events (20 April 1998 and 25 August 1998), in which
  acceleration is caused by fast CME-driven shocks. By combining
  data from ACE/SIS, Wind/EPACT/LEMT, and IMP8/GME, we examine all
  major species from H to Fe, from ~2 MeV/nuc to the highest energies
  measured. These events last for several days, so we have divided the
  events into 8-hour intervals in order to study the evolution of the
  spectra. The spectra reveal significant departures from simple power
  laws. Of particular note is the behavior at high energies, where the
  spectra exhibit exponential rollovers. We demonstrate that the fitted
  e-folding energies reflect both ionic charge states and a complex but
  orderly temporal evolution. We speculate that this behavior may be
  related to evolving rigidity dependence in the near-shock diffusion
  coefficient, which is of potentially great importance for models of
  SEP acceleration and transport. .

---------------------------------------------------------
Title: Particle acceleration by CME-driven shock waves
Authors: Reames, Donald V.
2000AIPC..516..289R    Altcode: 2000ICRC...26..289R
  In the largest solar energetic particle (SEP) events, acceleration
  occurs at shock waves driven out from the Sun by coronal mass ejections
  (CMEs). Peak particle intensities are a strong function of CME speed,
  although the intensities, spectra, and angular distributions of
  particles escaping the shock are highly modified by scattering on
  Alfvén waves produced by the streaming particles themselves. Element
  abundances vary in complex ways because ions with different values of
  Q/A resonate with different parts of the wave spectrum, which varies
  with space and time. Just recently, we have begun to model these
  systematic variations theoretically and to explore other consequences
  of proton-generated waves. .

---------------------------------------------------------
Title: Initial Time Dependence of Abundances in Solar Energetic
    Particle Events
Authors: Reames, D. V.; Ng, C. K.; Tylka, A. J.
2000ApJ...531L..83R    Altcode:
  We compare the initial behavior of Fe/O and He/H abundance ratios
  and their relationship to the evolution of the proton energy spectra
  in “small” and “large” gradual solar energetic particle (SEP)
  events. The results are qualitatively consistent with the behavior
  predicted by the theory of Ng et al. published in 1999. He/H ratios that
  initially rise with time are a signature of scattering by non-Kolmogorov
  Alfvén wave spectra generated by intense beams of shock-accelerated
  protons streaming outward in large gradual SEP events.

---------------------------------------------------------
Title: A Role for Ambient Energetic Particle Intensities in Shock
    Acceleration of Solar Energetic Particles
Authors: Kahler, S. W.; Reames, D. V.; Burkepile, J. T.
2000ASPC..206..468K    Altcode: 2000hesp.conf..468K
  No abstract at ADS

---------------------------------------------------------
Title: What We Don't Understand about Ion Accelaration in Flares
Authors: Reames, D. V.
2000ASPC..206..102R    Altcode: 2000hesp.conf..102R
  No abstract at ADS

---------------------------------------------------------
Title: Effect of Wave Generation on the Evolution of Elemental
    Abundances of Solar Energetic Particles
Authors: Ng, C. K.; Reames, D. V.; Tylka, A. J.
2000ASPC..206..162N    Altcode: 2000hesp.conf..162N
  No abstract at ADS

---------------------------------------------------------
Title: Energy-dependent ionization states of shock-accelerated
    particles in the solar corona
Authors: Reames, D. V.; Ng, C. K.; Tylka, A. J.
1999GeoRL..26.3585R    Altcode:
  We examine the range of possible energy dependence of the ionization
  states of ions that are shock-accelerated from the ambient plasma of the
  solar corona. If acceleration begins in a region of moderate density,
  sufficiently low in the corona, ions above ∼0.1 MeV/amu approach
  an equilibrium charge state that depends primarily upon their speed
  and only weakly on the plasma temperature. We suggest that the large
  variations of the charge states with energy for ions such as Si and Fe
  observed in the 1997 November 6 event are consistent with stripping
  in moderately dense coronal plasma during shock acceleration. In the
  large solar-particle events studied previously, acceleration occurs
  sufficiently high in the corona that even Fe ions up to 600 MeV/amu
  are not stripped of electrons.

---------------------------------------------------------
Title: Particle acceleration at the Sun and in the heliosphere
Authors: Reames, Donald V.
1999SSRv...90..413R    Altcode:
  Energetic particles are accelerated in rich profusion at sites
  throughout the heliosphere. They come from solar flares in the low
  corona, from shock waves driven outward by coronal mass ejections
  (CMEs), from planetary magnetospheres and bow shocks. They come
  from corotating interaction regions (CIRs) produced by high-speed
  streams in the solar wind, and from the heliospheric termination
  shock at the outer edge of the heliospheric cavity. We sample many
  populations near Earth, but can distinguish them readily by their
  element and isotope abundances, ionization states, energy spectra,
  angular distributions and time behavior. Remote spacecraft have
  probed the spatial distributions of the particles and examined new
  sources in situ. Most acceleration sources can be ‘seen’ only
  by direct observation of the particles; few photons are produced at
  these sites. Wave-particle interactions are an essential feature in
  acceleration sources and, for shock acceleration, new evidence of
  energetic-proton-generated waves has come from abundance variations
  and from local cross-field scattering. Element abundances often tell
  us the physics of the source plasma itself, prior to acceleration. By
  comparing different populations, we learn more about the sources, and
  about the physics of acceleration and transport, than we can possibly
  learn from one source alone.

---------------------------------------------------------
Title: Observations of systematic temporal evolution in elemental
    composition during gradual solar energetic particle events
Authors: Tylka, Allan J.; Reames, Donald V.; Ng, Chee K.
1999GeoRL..26.2141T    Altcode:
  The WIND/EPACT experiment offers a ∼100 fold increase in collecting
  power over instruments flown in previous solar cycles, thus allowing
  unprecedented detailed studies of temporal evolution in gradual
  solar energetic particle (SEP) events. We present hourly WIND/EPACT
  observations at ∼2-10 MeV/nuc from the 20 April 1998 and 26 August
  1998 SEP events. These observations show striking patterns in elemental
  composition which evolve in a systematic fashion throughout the events'
  several-day durations. These data, combined with theoretical modeling
  in a companion Letter [Ng et al. 1999], suggest that a dynamic Alfvén
  wave field, generated primarily by streaming energetic protons, is
  responsible for the complex behavior which is observed.

---------------------------------------------------------
Title: Effect of proton-amplified waves on the evolution of solar
    energetic particle composition in gradual events
Authors: Ng, Chee K.; Reames, Donald V.; Tylka, Allan J.
1999GeoRL..26.2145N    Altcode:
  We present a model of the coupled evolution of energetic ions and
  Alfvén waves, incorporating magnetic focusing, pitch-angle diffusion,
  wave amplification, and a traveling ion source. Ion transport through
  proton-amplified waves with non-Kolmogorov spectra produces the
  contrasting three-stage evolution of Fe/O and He/H ratios at several
  MeV/amu observed by Wind/EPACT in the 20 April 1998 gradual solar
  energetic particle event [Tylka et al., 1999].

---------------------------------------------------------
Title: Quiet-Time Spectra and Abundances of Energetic Particles
    During the 1996 Solar Minimum
Authors: Reames, Donald V.
1999ApJ...518..473R    Altcode:
  We report the energy spectra and abundances of ions with atomic
  number, Z, in the interval 2&lt;=Z&lt;=36 and energies ~3-20 MeV
  amu<SUP>-1</SUP> for solar and interplanetary quiet periods between 1994
  November and 1998 April, as measured by the large-geometry Low-Energy
  Matrix Telescope on the Wind spacecraft near Earth. The energy spectra
  show the presence of galactic and “anomalous” cosmic-ray components
  (GCR and ACR, respectively), depending on the element. ACR components
  are reported for Mg and Si for the first time at 1 AU, and the previous
  observation of S and Ar is confirmed. However, only GCR components are
  clearly apparent for the elements Ca, Ti, Cr, Fe, as well as for C. New
  limits are placed on a possible ACR contribution for other elements,
  including Kr.

---------------------------------------------------------
Title: Quiet-Time Spectra and Abundances of Energetic Particles
    During the 1996 Solar Minimum
Authors: Reames, Donald V.
1999STIN...9941072R    Altcode:
  We report the energy spectra and abundances of ions with atomic number,
  Z, in the interval Z is greater than or equal to 2 and Z is less than
  or equal to 36 and energies approximately 3-20 MeV/amu for solar and
  interplanetary quiet periods between 1994 November and 1998 April
  as measured by the large-geometry Low Energy Matrix Telescope (LEMT)
  telescope on the Wind spacecraft near Earth. The energy spectra show the
  presence of galactic (GCR) and "anomalous" cosmic ray (ACR) components,
  depending on the element. ACR components are reported for Mg and Si
  for the first time at 1 AU and the previous observation of S and Ar
  is confirmed. However, only GCR components are clearly apparent for
  the elements Ca, Ti, Cr, Fe, as well as for C. New limits are placed
  on a possible ACR contribution for other elements, including Kr.

---------------------------------------------------------
Title: Coronal Abundances
Authors: Fludra, A.; Saba, J. L. R.; Henoux, J. -C.; Murphy, R. J.;
   Reames, D. V.; Lemen, J. R.; Strong, K. T.; Sylwester, J.; Widing,
   K. G.
1999mfs..conf...89F    Altcode:
  Flare X-Ray Measurements from BCS Calcium Abundance Fe/H and Fe/Ca
  Abundance Relative Abundances of Ar. Ca. and Fe in Flares Factors
  Affecting Abundance Determinations from X-Ray Spectra FCS Abundances
  FCS Active-Region Abundances Abundance Variability in Active Regions
  Impact of Resonance Scattering Assessment of FCS Active-Region Abundance
  Results FCS Flare Abundance Studies Coronal CI/S and Ar/S Measurements
  Dem Studies of Flare Abuncances Determination of Solar Abundances
  by Solar Flare γ-Ray Spectrometry γ-Ray Spectral Analysis γ-Ray
  Results Solar Energetic Particles Major Proton Events CIR Events from
  Coronal Holes Impulsive Flare Events Theory of Abundance Fractionation
  Gravitational Settling Pressure Gradient and Stationary Diffusion
  Ion-Neutral Separation Due to Currents Ion-Neutral Separation Due to
  Electromagnetic Forces Discussion Summary

---------------------------------------------------------
Title: Coronal/Interplanetary Factors Contributing to the Intensities
    of E &gt; 20 MeV Gradual Solar Energetic Particle Events
Authors: Kahler, Stephen; Burkepile, Joan; Reames, Donald
1999ICRC....6..248K    Altcode: 1999ICRC...26f.248K
  Gradual solar energetic particle (SEP) events are produced in coronal
  and interplanetary shocks driven by fast coronal mass ejections
  (CMEs). There is a correlation between peak ∼ 20 MeV proton
  intensities of SEP events at 1 AU and the associated CME speeds measured
  in coronagraph white light images. However, a considerable scatter
  is found in that correlation, suggesting that factors other than CME
  speeds play significant roles in the production of SEP events. To
  search for these additional factors, we use peak 28 to 43 MeV proton
  intensities of 17 SEP events from IMP-8 and associated west limb CMEs
  from SMM with a restricted 650 to 850 km/s CME speed range. Despite
  the narrow CME speed range, the 17 SEP events ranged over more than 4
  orders of magnitude. We find that the SEP intensity does not depend on
  the CME latitude or even whether the CME lies in the ecliptic plane. SEP
  intensities are also independent of CME location in or out of coronal
  streamers. There is a weak correlation of SEP intensities with CME
  angular width and a strong correlation with ambient SEP intensity.

---------------------------------------------------------
Title: Streaming-limited Intensities of Solar Energetic Particles
Authors: Reames, D. V.; Ng, C. K.
1998ApJ...504.1002R    Altcode:
  Energetic particles streaming outward from an intense source near the
  Sun reach a maximum-intensity plateau when scattering by self-generated
  waves restricts the streaming. We compare calculated theoretical values
  of the streaming-limited intensities with observations from the Helios
  1 and 2 and the NOAA Geostationary Operational Environmental Satellites
  (GOES) spacecraft and examine the energy dependence and radial gradient
  of the intensities.

---------------------------------------------------------
Title: Evidence for multiple ejecta: April 7-11, 1997, ISTP Sun-Earth
    connection event
Authors: Berdichevsky, D.; Bougeret, J. -L.; Delaboudinière, J. -P.;
   Fox, N.; Kaiser, M.; Lepping, R.; Michels, D.; Plunkett, S.; Reames,
   D.; Reiner, M.; Richardson, I.; Rostoker, G.; Steinberg, J.; Thompson,
   B.; von Rosenvinge, T.
1998GeoRL..25.2473B    Altcode:
  Evidence is presented that the enhanced geomagnetic activity, on
  April 10-11, 1997, was caused by one of two ejecta that left the
  Sun at ≈ 14 UT on April 7. This ejecta was not directly detected
  at the Earth. The evidence for this interpretation is based on WIND
  spacecraft observations in the solar wind (SW). It is consistent with:
  (i) measured velocities of the coronal mass ejections from the SOHO
  coronagraph; (ii) the initial propagation speed of the shock generated
  in this event, estimation from type II radio burst observations from the
  WAVES instrument on WIND, and (iii) the time profile of energetic ions
  observed by EPACT on WIND. This locally unobserved ejecta (moving at 600
  to 700 kms<SUP>-1</SUP>) generated a fast shock which accelerated ions
  to several tens of MeV/amu. The inferred passage of the first ejecta
  close to Earth (on April 10 to 11) is based on the observation of an
  interplanetary shock (IS) ahead of a field and plasma compressional
  region where the draping of the SW flow and possibly the changes in
  the direction of the IMF are consistent with a location northward of a
  faster ejecta. This ejecta was responsible for disturbed SW conditions
  including approximately ten hours of southward orientation of the
  interplanetary magnetic field (IMF) and a ram pressure many times
  above normal. The slower moving ejecta was directed toward Earth and
  was observed with WIND from about 0550 until 1500 UT on April 11. It
  had a strong northward IMF and produced density enhancements which
  elevated the ram pressure to more than four times above normal.

---------------------------------------------------------
Title: Solar Energetic Particles: Sampling Coronal Abundances
Authors: Reames, Donald V.
1998SSRv...85..327R    Altcode:
  In the large solar energetic particle (SEP) events, coronal mass
  ejections (CMEs) drive shock waves out through the corona that
  accelerate elements of the ambient material to MeV energies in
  a fairly democratic, temperature-independent manner. These events
  provide the most complete source of information on element abundances
  in the corona. Relative abundances of 22 elements from H through Zn
  display the well-known dependence on the first ionization potential
  (FIP) that distinguishes coronal and photospheric material. For most
  elements, the main abundance variations depend upon the gyrofrequency,
  and hence on the charge-to-mass ratio, Q/A, of the ion. Abundance
  variations in the dominant species, H and He, are not Q/A dependent,
  presumably because of non-linear wave-particle interactions of H and
  He during acceleration. Impulsive flares provide a different sample of
  material that confirms the Ne:Mg:Si and He/C abundances in the corona.

---------------------------------------------------------
Title: Solar Energetic Particles: Sampling Coronal Abundances
Authors: Reames, D. V.
1998sce..conf..327R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Spatial and Temporal Invariance in the Spectra of Energetic
    Particles in Gradual Solar Events
Authors: Reames, D. V.; Kahler, S. W.; Ng, C. K.
1997ApJ...491..414R    Altcode:
  We show evidence of spatial and temporal invariance in the energy
  spectra of ~1-100 MeV protons from large gradual solar energetic
  particle (SEP) events. Nearly identical spectra are seen over longitude
  intervals of up to 160°, and the intensities at all energies decline
  with e-folding time constants of 6-18 hr for periods of ~3 days. The
  region of the invariant spectra is associated with acceleration on
  the eastern flank of the shock wave driven out from the Sun by a
  coronal-mass ejection (CME). The quasi-parallel shock in this region
  changes only slowly with time, and a quasi equilibrium is established
  for particles stored on field lines in the expanding volume between the
  shock and the Sun. On the western flank of the shock, the SEP event is
  more dynamic. Here, the nearly quasi-perpendicular shock produces harder
  spectra that change more rapidly with time as regions of the shock with
  varying speed and angle sweep across the observer's field line. <P
  />Gradual SEP events arise from large CMEs with sufficient speeds
  to generate shocks that are fast enough to accelerate particles. In
  our study, shocks with transit speed &gt;750 km s<SUP>-1</SUP>
  always accelerate particles, while those with speeds of 500-750 km
  s<SUP>-1</SUP> sometimes do. However, invariant spectra seem to occur
  in all gradual SEP events as a consequence of the structure and topology
  of the CME and shock.

---------------------------------------------------------
Title: Late-phase acceleration of energetic ions in corotating
    interaction regions
Authors: Reames, D. V.; Ng, C. K.; Mason, G. M.; Dwyer, J. R.; Mazur,
   J. E.; von Rosenvinge, T. T.
1997GeoRL..24.2917R    Altcode:
  We report on new high-sensitivity measurements from the WIND spacecraft
  of the spatial distributions of 30 keV/amu to 10 MeV/amu ions from
  corotating interaction regions (CIRs) that extend far beyond the
  confines of the parent high-speed solar-wind stream. Not only do
  late-phase MeV ions persist far into the declining solar wind,
  but they also show a continual gain in energy, even after sector
  boundary passage, until the next small increase in solar wind speed
  occurs. These ions are accelerated in the distant heliosphere as the
  reverse shock from the CIR propagates completely across the rarefaction
  region produced by the declining solar wind, growing in acceleration
  efficiency as it propagates. Energetic ions from a single CIR event
  are seen for a period of 17 days and ∼225° in solar longitude. The
  observed energy spectra can be fit to the theory of Fisk and Lee
  [1980] only if shock compression increases with time so that the
  spectra harden significantly.

---------------------------------------------------------
Title: New Spectral and Abundance Features of Interplanetary Heavy
    Ions in Corotating Interaction Regions
Authors: Mason, G. M.; Mazur, J. E.; Dwyer, J. R.; Reames, D. V.;
   von Rosenvinge, T. T.
1997ApJ...486L.149M    Altcode:
  We have surveyed the composition and energy spectra of heavy ions
  accelerated in 17 corotating interaction regions (CIRs) during
  solar minimum conditions between 1992 December and 1995 July. Using
  new high-sensitivity instruments on WIND and SAMPEX, we are able to
  cover the energy range from approximately 20 keV nucleon<SUP>-1</SUP>
  to greater than 10 MeV nucleon<SUP>-1</SUP>, making it possible to
  distinguish differing forms of particle spectra. Previous measurements
  down to about 0.5 MeV nucleon<SUP>-1</SUP> found exponential energy
  spectra; however, at the even lower energies studied here, we find
  that the spectral forms become power laws in kinetic energy per
  nucleon. At 150 keV nucleon<SUP>-1</SUP> we find that the C:O and Ne:O
  ratios depend on solar wind speed. These variations suggest that in
  addition to the solar wind, other sources of heavy ions contribute to
  the CIR composition.

---------------------------------------------------------
Title: Energy Spectra of Ions Accelerated in Impulsive and Gradual
    Solar Events
Authors: Reames, D. V.; Barbier, L. M.; Von Rosenvinge; T. T.; Mason,
   G. M.; Mazur, J. E.; Dwyer; J. R.
1997ApJ...483..515R    Altcode:
  We report new high-sensitivity measurements of the energy spectra of
  ions from five impulsive solar flares and one gradual event observed
  during solar minimum by the Energetic Particles, Acceleration,
  Composition, and Transport (EPACT) experiment aboard the WIND
  spacecraft. All of the impulsive-flare events had intensities too low
  to be visible on previous spacecraft such as ISEE 3, which observed
  hundreds of impulsive-flare events. Often these events cluster in
  or behind a coronal mass ejection (CME) where magnetic field lines
  provide an excellent connection to a solar active region where flares
  are occurring. In most cases we can see velocity dispersion as the
  ions of 20 keV amu<SUP>-1</SUP> to 10 MeV amu<SUP>-1</SUP> streamed out
  from the impulsive flare at the Sun, arriving in inverse order of their
  velocity. Ions from a large, magnetically well-connected gradual event,
  associated with a CME-driven shock, also show velocity dispersion early
  in the event but show identical time profiles that last for several days
  late in the event. These time-invariant spectra of H, <SUP>4</SUP>He,
  C, O, and Fe in this gradual event are well represented as power laws in
  energy from 20 keV amu<SUP>-1</SUP> to ~100 MeV amu<SUP>-1</SUP>. In the
  impulsive-flare events, H, <SUP>3</SUP>He, <SUP>4</SUP>He, C, O, and Fe
  have more rounded spectra that flatten somewhat at low energies; yet the
  intensities continue to increase down to 20 keV amu<SUP>-1</SUP>. Most
  of the ion energy content appears to lie below 1 MeV in the impulsive
  events, where it would be invisible to γ-ray line observations.

---------------------------------------------------------
Title: A Comparison of Characteristic Shock Speeds and Interplanetary
    Energetic Particle Fluxes
Authors: Kahler, S. W.; Reames, D. V.
1997SPD....28.0267K    Altcode: 1997BAAS...29..905K
  Previous comparisons of solar energetic particle (SEP) events at 1 AU
  with associated coronal mass ejections (CMEs) have shown a correlation
  between peak SEP fluxes and CME speeds. These results have provided
  some of the evidence for acceleration of SEPs by CME-driven shocks. We
  compare SEP observations from the Helios spacecraft with associated CME
  and shock speeds reported by Sheeley et al. (JGR, 1985). We find that
  the 3 &lt; E &lt; 6 MeV peak proton fluxes correlate better with the
  in situ shock speeds than with either the CME speeds or the average
  transit speeds of the shocks. This establishes a closer physical
  connection between SEPs and CME-driven shocks than the previous work
  which used CME speeds as rough proxies for the shock speeds. We also
  examine the speed profiles of a number of fast CMEs observed with the
  SOHO LASCO coronagraph to look for distinguishing characteristics of
  CMEs associated with SEPs at 1 AU.

---------------------------------------------------------
Title: WIND/EPACT observations of anomalous cosmic rays
Authors: Reames, D. V.; Barbier, L. M.; von Rosenvinge, T. T.
1997AdSpR..19..809R    Altcode:
  The Energetic Particles, Acceleration, Composition and Transport (EPACT)
  Experiment on the WIND spacecraft, and especially its large-geometry
  Low Energy Matrix Telescope (LEMT), is capable of sensitive measurements
  of ions of the anomalous cosmic-ray (ACR) component above 2 MeV/amu. We
  report on the energy spectra of He, C, N, O, Ne, S, and Ar and estimate
  element abundances at the acceleration site.

---------------------------------------------------------
Title: The First Observation of Sulfur in Anomalous Cosmic Rays by
    the GEOTAIL and the WIND Spacecrafts
Authors: Takashima, T.; Doke, T.; Hayashi, T.; Kikuchi, J.; Kobayashi,
   M.; Shirai, H.; Takehana, N.; Ehara, M.; Yamada, Y.; Yanagita,
   S.; Hasebe, N.; Kashiwagi, T.; Kato, C.; Munakata, K.; Kohno, T.;
   Kondoh, K.; Murakami, H.; Nakamoto, A.; Yanagimachi, T.; Reames,
   D. V.; von Rosenvinge, T. T.
1997ApJ...477L.111T    Altcode:
  The Geotail high-energy particle instruments have observed cosmic-ray
  particles in the energy range from 3 MeV n<SUP>-1</SUP> to 150 MeV
  n<SUP>-1</SUP> at 1 AU during the period 1992 September-1995 August. A
  remarkable enhancement of anomalous cosmic-ray (ACR) N, O, Ne, and C
  is observed during the period. A measurable enhancement of the sulfur
  flux below about 20 MeV n<SUP>-1</SUP> was observed. This is the first
  evidence showing the existence of sulfur in the anomalous component. The
  flux increase of anomalous sulfur, with a first ionization potential
  (FIP) of 10.4 eV, is smaller than that of ACR carbon with an FIP
  of 11.3 eV and much smaller than those of high-FIP elements, which
  suggests that the fractions of neutral carbon and sulfur atoms are
  significantly low in the very local interstellar medium.

---------------------------------------------------------
Title: The Helium Valley: Comparison of Impulsive Solar Flare Ion
    Abundances and Gyroresonant Acceleration with Oblique Turbulence in
    a Hot Multi-Ion Plasma
Authors: Steinacker, Jürgen; Meyer, Jean-Paul; Steinacker, Adriane;
   Reames, Donald V.
1997ApJ...476..403S    Altcode:
  We present a detailed interpretation of the heavy ion abundance
  enhancements observed in impulsive flare energetic particles, in terms
  of the conditions for gyroresonant acceleration by moderately oblique
  waves in a hot solar coronal plasma. <P />On the basis of a realistic
  coronal plasma containing its complete set of minor ions, we analyze
  first all parallel wave modes in terms of their dispersion relation,
  damping timescale, and condition for gyroresonant acceleration of
  thermal ions, as a function of temperature. We identify the “Helium
  Valley,” the region in the frequency-wavenumber plane of strong wave
  damping by thermal <SUP>4</SUP>He<SUP>+2</SUP> ions, as crucial for
  explaining the observed abundances: any ions with charge-to-mass ratio
  in the neighborhood of 0.5 cannot be accelerated preferentially,
  relative to <SUP>4</SUP>He<SUP>+2</SUP>. <P />Then solving the
  dispersion relation equation for oblique waves in a hot e-p-He plasma,
  we discuss this general class of waves in terms of polarization and
  damping timescale. For waves propagating at moderate angles to the
  magnetic field (θ ≉ 90°), our calculations indicate that the first
  harmonic n = 1 gyroresonance is dominant, and that the corresponding
  He valley narrows down for increasing angle θ. Using this analysis, we
  calculate the limits of the He valley and investigate the preferential
  gyroresonant acceleration of heavy ions by moderately oblique waves
  (θ ≉ 90°) in a solar coronal plasma. Only for nearly perpendicular
  waves (θ ~ 90°), are higher order resonances important and regions
  of wave damping by interaction with thermal particles vanishingly
  narrow in frequency. <P />We estimate the fraction of ions of each
  element outside the He valley as a function of temperature and compare
  the resulting enhanced abundances with the observed enhancements, for
  the case of a spectrum of non-quasi-perpendicular waves, as produced
  by a cascading of the general turbulence. The results allow us to
  specify the range of possible temperatures for the source plasma of
  the accelerated particles to between ~2.4 and ~4.5 × 10<SUP>6</SUP>
  K, i.e., comparable to active region (AR), but not to flaring gas,
  temperatures. This points to an acceleration of the ions taking place,
  either in the AR gas surrounding the flare itself or within the flaring
  loop but before it became heated. Constraints are set on the typical
  time Δt over which the ions are accelerated preferentially. We
  find times between ~5 × 10<SUP>-4</SUP> and ~3 × 10<SUP>-2</SUP>
  s (for our nominal plasma with density and field of n<SUB>e</SUB> =
  10<SUP>10</SUP> cm<SUP>-3</SUP> and B = 100 G); it could be ~10 times
  larger, if the typical conditions in quiescent ARs (n<SUB>e</SUB> ~ 2
  × 10<SUP>9</SUP> cm<SUP>-3</SUP> and B ~ 200 G) apply also to the bulk
  ~3 × 10<SUP>6</SUP> K gas of flaring ARs. We discuss another physical
  interpretation of Δt, if wave cascading is effective. Preliminary
  calculations have shown that the proposed selective acceleration
  mechanism can be applied in underdense (ω<SUB>p</SUB>/Ω<SUB>e</SUB>
  &lt; 1) as well as in overdense plasmas (our nominal case), provided
  that quasi-perpendicular waves (generated, e.g., by an electron beam)
  are not dominant.

---------------------------------------------------------
Title: Solar Energetic-Particle Spectra and the Structure of Coronal
    Mass Ejections
Authors: Reames, D. V.; Kahler, S. W.; Ng, C. K.
1997ICRC....1..185R    Altcode: 1997ICRC...25a.185R
  No abstract at ADS

---------------------------------------------------------
Title: Intensity Gradients of Anomalous Cosmic Ray Oxygen Throughout
    the Heliosphere
Authors: Cummings, A. C.; Stone, E. C.; Klecker, B.; Marsden, R. G.;
   Mewaldt, R. A.; Reames, D. V.; Trattner, K. J.; von Rosenvinge, T. T.;
   Webber, W. R.
1997ICRC....2..257C    Altcode: 1997ICRC...25b.257C
  No abstract at ADS

---------------------------------------------------------
Title: New Spectral and Abundance Features in Low Energy CIR He
    vy Ions
Authors: Mason, G. M.; Mazur, J. E.; Dwyer, J. R.; Reames, D. V.;
   von Rosenvinge, T. T.
1997ICRC....1..377M    Altcode: 1997ICRC...25a.377M
  No abstract at ADS

---------------------------------------------------------
Title: The First Observation of Sulfur in Anomalous Cosmic Rays by
    the GEOTAIL and the WIND Spacecrafts
Authors: Takashima, T.; Doke, T.; Hayashi, T.; Kikuchi, J.; Itsumi,
   K.; Kobayashi, M.; Shirai, H.; Takehana, N.; Hasebe, N.; Kohdoh, K.;
   Kohno, T.; Numakata, K.; Kato, C.; Yanagita, S.; Yamada, Y.; Reames,
   D. V.; von Rosenvinge, T. T.
1997ICRC....2..285T    Altcode: 1997ICRC...25b.285T
  No abstract at ADS

---------------------------------------------------------
Title: The Spatial Distribution of Particles Accelerated by Coronal
    Mass Ejection--driven Shocks
Authors: Reames, D. V.; Barbier, L. M.; Ng, C. K.
1996ApJ...466..473R    Altcode:
  We use multispacecraft observations to examine the spatial and temporal
  distributions of energetic particles accelerated by shock waves driven
  by coronal mass ejections from the Sun. The behavior of the intensity
  time profiles ahead of the shock can depend strongly on the longitude
  of the point where the observer's magnetic flux tube connects to
  the shock, relative to the nose of the shock where acceleration is
  strongest. Particle intensities can increase (decrease) with time
  as this point swings eastward through ≥ 50° toward (away from)
  the shock nose because of solar rotation. Well behind the shock,
  intensities are often constant with longitude and the intensities of
  these quasi-trapped particles at all energies decrease continuously with
  time over many days as their containment volume expands. Delayed proton
  events are produced when shocks expand into slow solar wind so they
  suddenly encounter an observer's field line far from the Sun. Sunward
  flows are seen when the shock passes over the observer or when it
  suddenly strikes his field line at radial distances out beyond him.

---------------------------------------------------------
Title: Heavy ion acceleration by cascading Alfvén waves in impulsive
    solar flares
Authors: Miller, James A.; Reames, Donald V.
1996AIPC..374..450M    Altcode: 1996hesp.conf..450M
  We propose that the heavy ion abundance enhancements that are observed
  for impulsive solar flares result from stochastic acceleration by
  cascading Alfvén wave turbulence. In our model, Alfvén waves are
  generated at some large scale and nonlinearly cascade to higher
  wavenumbers and frequencies. As the waves increase in frequency,
  they will be able to cyclotron resonate with ions of progressively
  lower energy. For a thermal plasma there will be no damping at low
  wavenumbers and the waves will freely cascade. However, when the wave
  frequency becomes close to an ion cyclotron frequency, thermal ions will
  be accelerated out of the background and to relativistic energies. The
  first ion species encountered by the waves will be the one with the
  lowest cyclotron frequency, namely Fe. Due to the low Fe abundance,
  the waves will not be completely damped and will continue to cascade up
  to the group of ions with the next higher cyclotron frequency, namely
  Ne, Mg, and Si. Again, these ions will be accelerated but the waves
  will not be totally damped. After Ne, Mg, and Si the waves encounter
  <SUP>4</SUP>He, C, N, and O, which do completely dissipate the waves
  and halt the cascade. We show that abundance ratios similar to those
  observed can result from this process.

---------------------------------------------------------
Title: Energetic particles from solar flares and coronal mass
    ejections
Authors: Reames, Donald V.
1996AIPC..374...35R    Altcode: 1996hesp.conf...35R
  We review the recent evidence that distinguishes particles accelerated
  in flares and in shock waves driven by coronal mass ejections
  (CMEs). CME-driven shocks, not flares, produce most of the large
  particle events at 1 AU and can accelerate protons up to 20 GeV. In
  contrast, flare-accelerated ions have characteristic abundances produced
  by resonant wave-particle interactions in the flare plasma. Only the
  direct particle observations have allowed us to study this new physics
  of ion acceleration in flares, since the energetic ion abundances have
  been largely invisible in photons.

---------------------------------------------------------
Title: Pitch Angle Diffusion Coefficient in an Extended Quasi-linear
    Theory
Authors: Ng, C. K.; Reames, D. V.
1995ApJ...453..890N    Altcode:
  Using an extended quasi-linear theory that takes account of the
  distribution of medium-scale background interplanetary magnetic
  field, we calculate the pitch angle diffusion coefficients of
  interplanetary energetic ions, for a slab turbulence model consisting
  of a superposition of parallel and antiparallel transverse R and L
  waves. Our results show that the background variation broadens the
  resonance function significantly at pitch angles near 90°, so that
  protons down to ≍ 25 keV interact with hydromagnetic waves at all
  pitch angles, and the steepening of the magnetic field power spectrum
  in the dissipation range does not result in a resonance gap or infinite
  scattering mean free path.

---------------------------------------------------------
Title: Solar energetic particles: A paradigm shift
Authors: Reames, Donald V.
1995RvGeo..33S.585R    Altcode: 1995RvGeS..33..585R
  Laboratory for High Energy Astrophysics, NASA Goddard Space Flight
  Center, Greenbelt, MarylandThe first evidence of high-energy particles
  from the Sun was obtained 50 years ago when Forbush [1946] used
  sea-level ion chambers to study the large solar events of February
  and March of 1942. Over the next 20 years, observation of these
  solar energetic particle (SEP) events using neutron monitors and
  riometers (that measure radio opacity of the ionosphere) and, later,
  with detectors on balloons and satellites, led to an extensive body
  of knowledge on the time profiles, spectra and particle abundance in
  the large events. Meanwhile, there was already a rich history of the
  study of solar flares spanning 100 years since the first observations
  reported by Carrington [1860]. With no knowledge of the existence of
  coronal mass ejections (CMEs) [Kahler 1992], it was tempting to assume
  that the particle acceleration somehow occurred in spatial and temporal
  conjunction with the solar flare itself. Thus the "solar flare myth"
  [Gosling 1993] of particle acceleration began nearly 30 years ago.

---------------------------------------------------------
Title: Coronal abundances determined from energetic particles
Authors: Reames, D. V.
1995AdSpR..15g..41R    Altcode: 1995AdSpR..15R..41R
  Solar energetic particles (SEPs) provide a measurement of coronal
  element abundances that is highly independent of the ionization
  states and temperature of the ions in the source plasma. The most
  complete measurements come from large `gradual' events where ambient
  coronal plasma is swept up by the expanding shock wave from a coronal
  mass ejection. Particles from `impulsive' flares have a pattern
  of acceleration-induced enhancements superimposed on the coronal
  abundances. Particles accelerated from high-speed solar wind streams
  at corotating shocks show a different abundance pattern corresponding
  to material from coronal holes. Large variations in He/O in coronal
  material are seen for both gradual and impulsive-flare events but
  other abundance ratios, such as Mg/Ne, are remarkably constant. SEP
  measurements now include hundreds of events spanning 15 years of
  high-quality measurement.

---------------------------------------------------------
Title: The Energetic Particles: Acceleration, Composition, and
    Transport (EPACT) investigation on the WIND spacecraft
Authors: von Rosenvinge, T. T.; Barbier, L. M.; Karsch, J.; Liberman,
   R.; Madden, M. P.; Nolan, T.; Reames, D. V.; Ryan, L.; Singh, S.;
   Trexel, H.; Winkert, G.; Mason, G. M.; Hamilton, D. C.; Walpole, P.
1995SSRv...71..155V    Altcode:
  The Energetic Particles: Acceleration, Composition, and Transport
  (EPACT) investigation is designed to make comprehensive observations
  of solar, interplanetary, and galactic particles over wide ranges of
  charge, mass, energy, and intensity using a combination of 8 different
  particle telescopes. This paper summarizes the scientific goals of
  EPACT and provides a detailed description of the instrument design
  and capabilities. Electrons are measured from 0.2 to 10 MeV, primarily
  providing time markers for injections of solar particles. Hydrogen is
  measured from 1.4 to 120 MeV, and Helium is measured from 0.04 to 500
  MeV nucl<SUP>-1</SUP>. The collection powers and energy ranges for
  heavier nuclei up to iron are ideal for observations of quiet-time
  populations such as particles accelerated by interplanetary shocks
  and the anomalous cosmic rays (thought to be accelerated at the
  boundary of the heliosphere). The large collection power available
  is also ideal for observations of<SUP>3</SUP>He,<SUP>4</SUP>He, and
  heavier nuclei in impulsive<SUP>3</SUP>He-rich solar events. There
  is even the possibility of observing ultra heavy nuclei (Z&gt;30) in
  large solar events for the first time. Finally, there is a telescope
  designed to measure isotopes from He (3.4 55 MeV nucl<SUP>-1</SUP>)
  to Fe (12 230 MeV nucl<SUP>-1</SUP>), which is intended for solar
  particles, the anomalous cosmic rays and galactic cosmic rays. The
  overall capabilities of EPACT provide scientifically interesting
  measurements over all phases of the solar cycle. There will also be
  important opportunities for combined studies with other spacecraft,
  such as SAMPEX, Ulysses, and Voyagers 1 and 2.

---------------------------------------------------------
Title: Multispacecraft Studies of Coronal Mass Ejection Associated
    Energetic Particle Events
Authors: Barbier, L. M.; Ng, C. K.; Reames, D. V.
1995ICRC....4..365B    Altcode: 1995ICRC...24d.365B
  No abstract at ADS

---------------------------------------------------------
Title: Interplanetary Transport Coefficient in an Extended
    Quasi-linear Theory
Authors: Ng, C. K.; Reames, D. V.
1995ICRC....4..253N    Altcode: 1995ICRC...24d.253N
  No abstract at ADS

---------------------------------------------------------
Title: The dark side of the solar flare myth
Authors: Reames, D. V.
1995EOSTr..76..405R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar energetic particles: A paradigm shift (95RG00188)
Authors: Reames, Donald V.
1995iugg.rept..585R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Helium Spectra in Corotating Energetic Particle Streams
    Observed by EPACT on the Wind Spacecraft
Authors: Mazur, J. E.; Mason, G. M.; Reames, D. V.; von Rosenvinge,
   T. T.
1995ICRC....4..460M    Altcode: 1995ICRC...24d.460M
  No abstract at ADS

---------------------------------------------------------
Title: Acceleration of energetic particles which accompany coronal
    mass ejections
Authors: Reames, D. V.
1994ESASP.373..107R    Altcode: 1994soho....3..107R
  No abstract at ADS

---------------------------------------------------------
Title: Recombination energy of atomic oxygen and related species at
    the mesopause
Authors: Reames, Donald V.
1994AdSpR..14d.177R    Altcode: 1994AdSpR..14..177R
  Total chemical energy release of seven exothermic reactions involving
  odd-oxygen and odd-hydrogen species at mesopause heights is studied
  here. Monthly and zonally averaged heating rates are calculated on
  the basis of atomic oxygen densities and atomic hydrogen densities as
  these were measured by the SME satellite. The resulting heating rates
  are found to be rather high. Consequently they could help to balance
  the energy budget of the upper mesosphere and lower thermosphere.

---------------------------------------------------------
Title: Focused Interplanetary Transport of approximately 1MeV Solar
    Energetic Protons through Self-generated Alfven Waves
Authors: Ng, C. K.; Reames, D. V.
1994ApJ...424.1032N    Altcode:
  We present a model of the focused transport of approximately 1 MeV
  solar energetic protons through interplanetary Alfven waves that the
  protons themselves amplify or damp. It is based on the quasi-linear
  theory but with a phenomenological pitch angle diffusion coefficient in
  the 'resonance gap.' For initial Alfven wave distributions that give
  mean free paths greater than approximately 0.5 AU for approximately
  1 MeV protons in the inner heliosphere, the model predicts greater
  than roughly an order of magnitude amplification (damping) in the
  outward (inward) propagating resonant Alfven waves at less than or
  approximately equal to o.3 AU heliocentric distance. As the strength of
  proton source is increased, the peak differential proton intensity at
  approximately 1 MeV at 1 AU increases to a maximum of approximately 250
  particles (/(sq cm)(s)(sr)(MeV)) and then decreases slowly. It may be
  attenuated by a factor of 5 or more relative to the case without wave
  evolution, provided that the proton source is sufficiently intense
  that the resulting peak differential intensity of approximately
  1 MeV protons at 1 AU exceeds approximately 200 particles (/(sq
  cm)(s)(sr)(MeV)). Therefore, in large solar proton events, (1) one
  may have to take into account self-amplified waves in studying solar
  particle propagation, (2) the number of accelerated protons escaping
  from a flare or interplanetary shock may have been underestimated in
  past studies by a significant factor, and (3) accelerated protons
  escaping from a traveling interplanetary shock at r less than or
  approximately equal to 0.3 AU should amplify the ambient hydromagnetic
  waves siginificantly to make the shock an efficient accelerator, even
  if initially the mean free path is greater than or approximately equal
  to 1 AU.

---------------------------------------------------------
Title: Energetic-Particle Abundances in Impulsive Solar Flare Events
Authors: Reames, D. V.; Meyer, J. P.; von Rosenvinge, T. T.
1994ApJS...90..649R    Altcode: 1994IAUCo.142..649R
  We report on the abundances of energetic particles from impulsive solar
  flares, including those from a survey of 228 He-3 rich events, with
  He-3/He-4 is greater than 0.1, observed by the International Sun Earth
  Explorer (ISEE) 3 spacecraft from 1978 August through 1991 April. The
  rate of occurrence of these events corresponds to approximately 1000
  events/yr on the solar disk at solar maximum. Thus the resonant plasma
  processes that enhance He-3 and heavy elements are a common occurrence
  in impulsive solar flares. To supply the observed fluence of He-3
  in large events, the acceleration must be highly efficient and the
  source region must be relatively deep in the atmosphere at a density
  of more than 10<SUP>10</SUP> atoms/cu cm. He-3/He-4 may decrease in
  very large impulsive events because of depletion of He-3 in the source
  region. The event-to-event variations in He-3/He-4, H/He-4, e/p, and
  Fe/C are uncorrelated in our event sample. Abundances of the elements
  show a pattern in which, relative to coronal composition, He-4, C, N,
  and O have normal abundance ratios, while Ne, Mg, and Si are enhanced
  by a factor approximately 2.5 and Fe by a factor approximately 7. This
  pattern suggests that elements are accelerated from a region of the
  corona with an electron temperature of approximately 3-5 MK, where
  elements in the first group are fully ionized (Q/A = 0.5), those in
  the second group have two orbital electrons (Q/A approximately 0.43),
  and Fe has Q/A approximately 0.28. Ions with the same gyrofrequency
  absorb waves of that frequency and are similarly accelerated and
  enhanced. Further stripping may occur after acceleration as the ions
  begin to interact with the streaming electrons that generated the
  plasma waves.

---------------------------------------------------------
Title: Comparison of CMEs, magnetic clouds, and bidirectionally
    streaming proton events in the heliosphere using helios data
Authors: Webb, D.; Jackson, B.; Hick, P.; Schwenn, R.; Bothmer, V.;
   Reames, D.
1993AdSpR..13i..71W    Altcode: 1993AdSpR..13...71W
  Coronal Mass Ejections (CMEs) are large, energetic expulsions of mass
  and magnetic fields from the Sun; they can significantly affect large
  volumes of the heliosphere and appear to be a key cause of geomagnetic
  storms. We have compiled a list of all significant CMEs detected by
  the HELIOS white light photometers from 1975-1982. We are studying the
  characteristics of these CMEs, and present preliminary results of their
  associations with in-situ features, especially magnetic “clouds” and
  periods of bidirectionally streaming ions, two classes of structures
  considered indicative of interplanetary loops. Advantages of this data
  set include reliable association in the interplanetary medium of the
  white light CME plasma with the in-situ features, and observations of
  a large number of events over a long time base.

---------------------------------------------------------
Title: Non-thermal particles in the interplanetary medium
Authors: Reames, Donald V.
1993AdSpR..13i.331R    Altcode: 1993AdSpR..13..331R
  During the past few years we have found that the MeV ion populations
  from a variety different of solar and interplanetary sources have quite
  distinct abundances and spectra. Particles from impulsive flares are
  electron rich, have <SUP>3</SUP>He/<SUP>4</SUP>He enhancements of up to
  10<SUP>4</SUP>, and enhancements in heavy elements like Fe/C by factors
  of 10, relative to coronal abundances. The high ionization state of Fe,
  +20, indicates heating of the material to temperatures up to ~20 MK
  (1 MK = 10<SUP>6</SUP> K). The enhancements are probably produced by
  selective absorption of plasma waves in these events. In contrast,
  particles from gradual solar events have strong proton enhancements at
  high energies, but element abundances and ionization states are more
  typical of ambient coronal material. The abundances, time profiles,
  and extended longitude distribution of gradual events indicate that
  particles are accelerated from the ambient corona and solar wind by
  a shock wave that is driven by a coronal mass ejection.

---------------------------------------------------------
Title: Bidirectional approximately 1 MeV AMU -1 Ion Intervals in
    1973--1991 Observed by the Goddard Space Flight Center Instruments
    on IMP 8 and ISEE 3/ICE
Authors: Richardson, I. G.; Reames, D. V.
1993ApJS...85..411R    Altcode:
  Bidirectional energetic ion flows (BIFs) in the solar wind at 1AU
  during 1973-1991 are examined on the basis of about 1 MeV/amu data
  from the Goddard Space Flight Center instruments on ISEE3/ICE and IMP
  8. BIFs are observed more frequently around solar maximum, when they are
  observed about 12 percent of the time compared with about 5 percent at
  solar minimum. Intervals with durations greater than 4 hr are observed
  on average approximately every 3-4 d at solar maximum and every 2 wk
  at solar minimum, with about 33 percent of these intervals following
  within 2 d of an interplanetary shock. Various coronal mass ejection
  signatures and BIFs greater than 1 MeV/amu usually do not coincide
  exactly, and additional bidirectional ion events are identified.

---------------------------------------------------------
Title: The EPACT Experiment
Authors: Barbier, L. M.; Reames, D. V.; von Rosenvinge, T. T.
1993ICRC....3..222B    Altcode: 1993ICRC...23c.222B
  No abstract at ADS

---------------------------------------------------------
Title: Mean Element Abundances in Energetic Particles from Impulsive
    Solar Flares
Authors: Reames, D. V.
1993ICRC....3..388R    Altcode: 1993ICRC...23c.388R
  No abstract at ADS

---------------------------------------------------------
Title: Heavy Ion Acceleration and Abundance Enhancements in Impulsive
    Solar Flares
Authors: Miller, J.; Viñas, A.; Reames, D. V.
1993ICRC....3...17M    Altcode: 1993ICRC...23c..17M
  No abstract at ADS

---------------------------------------------------------
Title: Corotating MeV/amu ion enhancements at &lt;=1 AU from 1978
    to 1986
Authors: Richardson, I. G.; Barbier, L. M.; Reames, D. V.; von
   Rosenvinge, T. T.
1993JGR....98...13R    Altcode:
  MeV/amu ion enhancements associated with corotating high-speed
  solar wind streams in 1978-1986 during pre-solar maximum to near
  solar minimum conditions are studied using ISEE 3/ICE, IMP 8, and
  Helios 1 data. Around 50% of corotating streams contain energetic
  ion increases. These increases extend to ~25 MeV/amu, where they
  merge into the galactic cosmic ray background, and are most evident
  approaching solar minimum. Sunward ion streaming in the solar wind
  frame (first-order anisotropy ~20%) and positive radial intensity
  gradients (~400%/AU) are consistent with acceleration in the
  outer heliosphere at corotating shocks followed by streaming into
  the inner heliosphere. The spectra and intensities show little
  solar cycle variation. The spectra of ions from protons to Fe
  at ~2-20 MeV/amu are approximated equally well by exponentials
  in momentum dJ/dP~exp(-P/P<SUB>0</SUB>), P<SUB>0</SUB>=11-16
  MeV c<SUP>-</SUP><SUP>1</SUP> amu<SUP>-</SUP><SUP>1</SUP>, or by
  distribution functions f~exp(-v/v<SUB>0</SUB>), v<SUB>0</SUB>=0.18-0.25
  (MeV/amu)<SUP>1/2</SUP>, with equivalent power law in energy slopes
  in the range ~-3 to -4. Ion abundances are correlated with the
  stream peak solar wind speed. <P />In slower corotating streams
  (maximum solar wind speed &lt;600 km/s), mean abundance ratios are
  protons/<SUP>4</SUP>He=43+/-18 <SUP>4</SUP>He/O=54+/-23 C/O =0.62+/-0.06
  Mg/O=0.19+/-0.03, and Fe/O=0.14+/-0.02. These show some similarity
  to the corresponding ratios for “solar energetic particles” (SEP)
  (protons/<SUP>4</SUP>He=70+/-10 <SUP>4</SUP>He/O=55+/-3 C/O=0.48+/-0.02
  Mg/O=0.21+/-0.01 and Fe/O=0.16+/-0.02) which are typically accelerated
  by shocks passing through slow solar wind. In corotating events in
  higher-speed streams, these ratios become protons/<SUP>4</SUP>He=19+/-5
  <SUP>4</SUP>He/O=130+/-35 C/O=0.89+/-0.05 Mg/O=0.14+/-0.01, and
  Fe/O=0.10+/-0.01 and more closely resemble the corotating event
  abundance ratios measures in high-speed streams during the mid-1970s
  solar minimum (protons/<SUP>4</SUP>He=17+/-7 <SUP>4</SUP>He/O~160+/-50
  C/O=0.89+/-0.1 Mg/O=0.13+/-0.03, and Fe/O=0.096+/-0.05). Solar wind
  plasma may also show similar variations in composition with solar
  wind speed (based on the limited solar wind composition with solar
  wind speed (based on the limited solar wind composition measurements
  available) so that the energetic ion compositions are consistent with
  the acceleration of corotating event ions and SEPs from the solar
  wind. The ordering of corotating event and solar wind abundances by
  first ionization potential and their variation with solar wind speed
  suggest that conditions in the ion-neutral fractionation region in the
  upper chromosphere determine the abundances and are associated in some
  way with regulation of the solar wind speed.

---------------------------------------------------------
Title: Recent Observations and the Modeling of Solar Proton Events
Authors: Reames, D. V.
1993stp2.conf..302R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: An On-board Particle Identification Algorithm for the WIND
    Spacecraft
Authors: Von Rosenvinge, T. T.; Barbier, L. M.; Reames, D. V.
1993ICRC....3..400V    Altcode: 1993ICRC...23c.400V
  No abstract at ADS

---------------------------------------------------------
Title: Selective <SUP>3</SUP>He and Fe Acceleration in Impulsive
    Solar Flares
Authors: Miller, J.; Viñas, A.; Reames, D. V.
1993ICRC....3...13M    Altcode: 1993ICRC...23c..13M
  No abstract at ADS

---------------------------------------------------------
Title: Energetic particle observations and the abundances of elements
    in the solar corona.
Authors: Reames, Donald V.
1992ESASP.348..315R    Altcode: 1992cscl.work..315R
  During the last few years it has become clear that energetic particles
  in the largest solar events, where abundances are commonly measured,
  are not accelerated in flares. Rather they are accelerated from
  the ambient plasma above active regions by shock waves driven by
  coronal mass ejections. The lowest energy particles from these events
  have abundances that almost directly reflect those of the source
  plasma. Residual effects of acceleration, that depend smoothly on the
  ion's coronal Q/A, vanish when abundances are averaged over many events,
  yielding the characteristic dependence of the average coronal abundances
  on the first ionization potential (FIP) of the elments from H through
  Fe. In contrast, energetic ions accelerated out of the high-speed
  solar wind from large coronal holes show a reduced FIP effect with a
  different pattern.

---------------------------------------------------------
Title: Particle acceleration in solar flares: Observations
Authors: Reames, Donald V.
1992AIPC..264..213R    Altcode: 1992pacp.work..213R
  Contrary to our historical understanding, the energetic particles in
  most major solar proton events do not come from the flare itself. The
  particle abundances, ionization states, time evolution and longitude
  distributions all indicate that the particles are accelerated from the
  ambient plasma by a shock wave driven by a coronal mass ejection in
  these events. In contrast, the particles that do come from impulsive
  solar flares are unique in character. These particles are electron
  rich, have 3He/4He enhancements of up to 104, and enhancements in heavy
  elements such as Fe/C by factors of 10. The high ionization state of
  Fe, +20, indicates that the material has been heated to temperatures
  of ~2×107 K. It is generally believed that preferential heating
  by selective absorption of plasma waves is combined with stochastic
  acceleration in these events. Recent studies of the broad gamma-ray
  lines emitted by energetic particles within the flare loops indicate
  that they are also Fe rich, 3He rich and proton poor like the particles
  seen at 1 AU. In large impulsive events, particles from the impulsive
  phase may be re-accelerated by a coronal blast-wave shock.

---------------------------------------------------------
Title: Study of CMES Observed in the Heliosphere Using HELIOS
    Photometer, Magnetic Field and Plasma Data
Authors: Webb, D. F.; Jackson, B. V.; Reames, D. V.
1992AAS...180.1105W    Altcode: 1992BAAS...24..747W
  The zodiacal light photometers on the two Helios spacecraft have been
  used to identify and study the characteristics of solar mass ejections
  within 1 AU of the Sun. We have compiled a list of all significant
  CMEs detected by the photometers between 1975 and 1985. We examine
  the in-situ characteristics of a subset of these CMEs which enveloped
  the spacecraft. In particular, we present results of analyses of
  structures considered to be manifestations of interplanetary CMEs,
  such as magnetic "clouds", shocks and periods of bidirectionally
  streaming ions at energies of about 1 MeV. An important advantage of
  this data set is that it permits us to make reliable associations in
  the interplanetary medium over a long time base between many white
  light CMEs and their in-situ proxies.

---------------------------------------------------------
Title: Energy Spectra of Ions from Impulsive Solar Flares
Authors: Reames, D. V.; Richardson, I. G.; Wenzel, K. -P.
1992ApJ...387..715R    Altcode:
  A study of the energy spectra of ions from impulsive solar flares in
  the 0.1-100 MeV region is reported. Most of the events studied are
  dominated by He and these He spectra show a persistent steepening or
  break above about 10 MeV resulting in an increase in the power-law
  spectral indices from about 2 to about 3.5 or more. Spectra of H,
  He-3, O, and Fe have spectral indices that are consistent with a
  value of about 3.5 above about 2 MeV/amu. One event, dominated by
  protons, shows a clear maximum in the spectrum near 1 MeV. If the
  rollover in the spectrum below 1 MeV is interpreted as a consequence
  of matter traversal in the solar atmosphere, then the source of the
  acceleration would lie only about 800 km above the photosphere, well
  below the corona. Alternative interpretations are that trapping in
  the acceleration region directly causes a peak in the resulting ion
  spectrum or that low-energy particles encounter significant additional
  scattering during transport from the flare.

---------------------------------------------------------
Title: Trapping and Escape of the High Energy Particles Responsible
    for Major Proton Events
Authors: Reames, D. V.
1992LNP...399..180R    Altcode: 1992IAUCo.133..180R; 1992esf..coll..180R
  During the last few years, we have learned to distinguish the particle
  acceleration mechanisms involved in impulsive and gradual flares
  directly from particle observations at 1 AU. Energetic particles
  from impulsive flares are characterized as rich in electrons, 3He,
  and Fe and high ionization states of Fe indicate that the material
  has been heated in the flare. Particles from these events are only
  seen from magnetically well-connected flares, and the particles reach
  maximum intensity in a few hours. Particles from gradual events have
  heavy element abundances (e.g. Fe/C) and ionization states that are
  near their coronal values but protons are strongly enhanced. Gradual
  events come from a wide longitude region and particle intensities remain
  high for several days, much longer than the associated phenomena at the
  Sun. Most major proton events are gradual events, but some are impulsive
  or have both impulsive and gradual phases. The extended evolution of the
  major proton events in space and time can no longer be understood in
  terms of slow diffusive transport of particles through the corona and
  interplanetary medium, since particles from the impulsive events are
  found to behave much differently. The observations can be understood
  only if the major gradual events involve a large interplanetary shock
  wave that accelerates particles over an extended region of longitude
  for a long time. Wave-particle interactions play a major role in the
  trapping and acceleration of particles in large events. Streaming
  particles may be scattered by self-amplified waves that provide a
  throttling mechanism that limits the particle intensities from large
  events and distributes particles in time as they leak from the source
  region. Diffusive containment allows particle acceleration to occur on
  open as well as closed field lines in both impulsive and gradual events.

---------------------------------------------------------
Title: On the Differences in Element Abundances of Energetic Ions
    from Corotating Events and from Large Solar Events
Authors: Reames, D. V.; Richardson, I. G.; Barbier, L. M.
1991ApJ...382L..43R    Altcode:
  The abundances of energetic ions accelerated from high-speed solar
  wind streams by shock waves formed at corotating interaction regions
  (CIRs) where high-speed streams overtake the lower-speed solar wind are
  examined. The observed element abundances appear to represent those of
  the high-speed solar wind, unmodified by the shock acceleration. These
  abundances, relative to those in the solar photosphere, are organized
  by the first ionization potential (FIP) of the ions in a way that is
  different from the FIP effect commonly used to describe differences
  between abundances in the solar photosphere and those in the solar
  corona, solar energetic particles (SEPs), and the low-speed solar
  wind. In contrast, the FIP effect of the ion abundances in the CIR
  events is characterized by a smaller amplitude of the differences
  between high-FIP and low-FIP ions and by elevated abundances of He,
  C, and S.

---------------------------------------------------------
Title: Multispacecraft Observations of Solar 3He-rich Events
Authors: Reames, D. V.; Kallenrode, M. -B.; Stone, R. G.
1991ApJ...380..287R    Altcode:
  A systematic search of He isotope observations on the Helios 1 and
  2 spacecraft during the occurrence of 66 (He-3)-rich time periods
  observed on ISEE 3 over a 4-yr interval is reported. Seven time-periods
  show possible event associations but only three show confirmed events
  with similar He-3/He-4 ratios on Helios and ISEE 3. Kilometric radio
  observations of type III bursts produced by electrons associated with
  the (He-3)-rich events are used to map the interplanetary field lines
  outward from the events. The observations are best explained in terms
  of a narrow cone of emission of the particles from these events.

---------------------------------------------------------
Title: Element Abundances in Solar <SUP>3</SUP>He-Rich Events
Authors: Reames, D. V.; Cane, H. V.; von Rosenvinge, T. T.; Meyer,
   J. -P.
1991ICRC....3..319R    Altcode: 1991ICRC...22c.319R; 1991icrc...22....7R
  The results of a survey of over 228 (He-3)-rich events, with He-3/H-4
  of more than 0.1, observed by the ISEE-3 spacecraft from 1978 August
  through 1991 April. In these events the elements above C are enhanced
  relative to the corresponding abundances in the corona and the degree
  of enhancement increases with Z or A. The flare-to-flare variations
  in abundances are different in character from those seen in large
  proton events. For example, using Fe/C as a parameter to describe these
  variations, the slope of the least-squares fits to ln(X/C) vs ln(Fe/C),
  where X is the intensity of N, O, Ne, Mg, Si, or S. Slopes of these
  abundance-correlation lines are much steeper for the (He-3)-rich events
  than for a sample of 36 large proton events, especially for Ne and
  heavier ions. The event-to-event variations for the (He-3)-rich events
  distinguish 3 groups of elements, He-O, Ne-S, and Fe. The abundances
  of all of the species within each group seem to vary in unison.

---------------------------------------------------------
Title: Size Distributions of Solar Energetic Particle Events
Authors: Cliver, E.; Reames, D.; Kahler, S.; Cane, H.
1991ICRC....3...25C    Altcode: 1991ICRC...22c..25C; 1991icrc...22....2C
  NASA particle detectors on the IMP-8 are employed to determine the size
  distributions of the peak fluxes of events related to solar-energetic
  particles including protons and electrons. The energetic proton events
  show a flatter size distribution which suggests that not all flares
  are proton flares. Both the electron and proton events are classified
  as either 'impulsive' or 'gradual', and the impulsive events tend to
  have a steeper power-law distribution.

---------------------------------------------------------
Title: Focused Interplanetary Transport of Solar Energetic Particles
    Through Self-Generated Alfven Waves
Authors: Ng, C. K.; Reames, D. V.
1991ICRC....3..209N    Altcode: 1991ICRC...22c.209N; 1991icrc...22....4N
  The coupled evolution of solar-flare protons and interplanetary Alfven
  waves based on the quasi-linear theory implies an order of magnitude
  amplification (damping) in the outward (inward) propagating left helical
  resonant Alfven waves at less than 0.4-AU helioradius, if the proton
  intensity at 1 AU exceeds 300 particles/(sq cm s sr MeV) at 1 MeV,
  and the initial wave intensities give mean free paths of more than 0.5
  AU. The wave growth significantly retards solar-particle transport,
  and has implications on the nature of solar-wind turbulence.

---------------------------------------------------------
Title: Bidirectional MeV/n Ion Intervals: Observations from the
    Goddard Space Flight Center Instruments on the ISEE 3/ICE, IMP 8,
    Helios-1 and Helios-2 Spacecraft
Authors: Richardson, I. G.; Reames, D. V.
1991ICRC....3..292R    Altcode: 1991icrc...22....6R; 1991ICRC...22c.292R
  A search is made for intervals of bidirectional energetic ion streaming
  in approximately 1 MeV data from the instruments on ISEE 3/ICE,
  IMP 8 and Helios 1 and 2 during 1973 to 1989. The longest duration
  intervals are found around solar maximum, consistent with the expected
  association with coronal mass ejections. The ISEE 3/ICE intervals are
  associated with previously identified bidirectional 35-1000 keV ions
  and solar-wind electron heat fluxes, though additional bidirectional
  intervals are found.

---------------------------------------------------------
Title: Radial Propagation of Solar Energetic Particles Assuming
    Large Scattering Mean Free Paths in the Interplanetary Medium
Authors: Mason, G. M.; Reames, D. V.; Ng, C. K.
1991ICRC....3..197M    Altcode: 1991icrc...22....3M; 1991ICRC...22c.197M
  Observations of two flares which fit the diffusive model by Beeck
  et al. (1987) are employed to determine whether large solar-particle
  events can be explained by the mechanisms of small impulsive events. It
  is shown that the injection of particles at the source is extended in
  time and lasts more than approximately 10 hours. The extended injection
  at the sun is hypothesized to be the reason that large solar particles
  do not demonstrate the 'pulse/wake' behavior associated with the small
  impulsive events.

---------------------------------------------------------
Title: MeV/n Ions Associated with Corotating High-speed Solar Wind
    Streams at &lt; 1 AU during 1978 to 1986
Authors: Richardson, I. G.; Barbier, L. M.; Reames, D. V.; von
   Rosenwinge, T. T.
1991ICRC....3..288R    Altcode: 1991ICRC...22c.288R; 1991icrc...22....5R
  Data from the Goddard Space Flight Center experiments on the ISEE 3/ICE,
  IMP 8, and Helios 1 spacecraft are used to investigate ion enhancements
  of more than 1 MeV/n associated with corotating high-speed solar wind
  streams at least 1 AU during 1978-1986. The observations are consistent
  with ion acceleration from the solar wind by corotating shocks in the
  outer heliosphere.

---------------------------------------------------------
Title: Energy Spectra of Ions from Impulsive Solar Flares
Authors: Reames, D. V.; Richardson, I. G.; Wenzel, K. -P.
1991ICRC....3...13R    Altcode: 1991ICRC...22c..13R; 1991icrc...22....1R
  A study of the energy spectra of ions from impulsive solar flares
  in the 0.1 to 100 MeV region is reported with data from the combined
  observations of experiments on the ISEE 3 and IMP 8 spacecraft. Most
  of the events studied are dominated by He, and these He spectra show
  a persistent steepening or break above about 10 MeV resulting in
  an increase in the power-law spectral indices from about 2 to about
  3.5 or more. One event, dominated by protons, shows a clear maximum
  in the spectrum near 1 MeV. If the rollover in the spectrum below 1
  MeV is interpreted as a consequence of matter traversal in the solar
  atmosphere, then the source of the acceleration would lie only about
  800 km above the photosphere, well below the corona. An alternative
  interpretation is that trapping in the acceleration region directly
  causes a peak in the spectrum.

---------------------------------------------------------
Title: Abundance variations in solar energetic particles
Authors: Cane, H. V.; Reames, D. V.; von Rosenvinge, T. T.
1991ICRC....3..327C    Altcode: 1991ICRC...22c.327C; 1991icrc...22....8C
  Abundance variations are examined in a large number of events including
  smaller nonimpulsive events not previously considered. Whereas a
  comparison at equal energy per nucleon is appropriate for heavy ions
  this is not the case when including H. The best representation is
  either in terms of rigidity or energy per charge depending on the
  type of event under consideration. For the majority of large events,
  where particles are primarily accelerated at interplanetary shocks, if
  abundances relative to H are evaluated at equal energy per charge then
  abundance ratios are compatible with solar wind values and spectral
  shapes agree. Furthermore the behavior of H is then compatible with
  that of other high FIP elements.

---------------------------------------------------------
Title: Probing the magnetic topologies of magnetic clouds by means
    of solar energetic particles
Authors: Kahler, S. W.; Reames, D. V.
1991JGR....96.9419K    Altcode:
  Magnetic clouds are large (&lt;0.25 AU) interplanetary regions with
  topologies consistent with those of magnetic loops. They are of
  interest because they may be an interplanetary signature of coronal
  mass ejections. Clouds have been identified in solar wind data by
  their magnetic properties and by the presence of bidirectional particle
  fluxes. Two possible closed magnetic topologies have been considered for
  clouds: (1) an elongated bottle with field lines rooted at both ends
  in the Sun and (2) a detached magnetic bubble or plasmoid consisting
  of closed field lines. The inferred topologies are also consistent
  with open field lines that converge beyond 1 AU. We have used solar
  energetic particles (SEPs) as probes of the cloud topologies. The rapid
  access of SEPs to the interiors of many clouds indicates that the cloud
  field lines extend back to the Sun and hence are not plasmoids. The
  small modulation of galactic cosmic rays associated with clouds also
  suggests that the magnetic fields of clouds are not closed. ©1991
  American Geophysical Union

---------------------------------------------------------
Title: Solar Particle Abundances at Energies Greater than 1 MeV per
    Nucleon and the Role of Interplanetary Shocks
Authors: Cane, H. V.; Reames, D. V.; von Rosenvinge, T. T.
1991ApJ...373..675C    Altcode:
  The abundances of elements in large solar energetic-particle events
  in the energy range of 2-12 MeV per nucleon are examined. It is
  confirmed that the abundances relative to mean values vary approximately
  monotonically as a function of mass, except for He-4; some events show
  a gradual depletion of heavy ions, whereas a small number displays a
  gradual increase. A further organization of abundance data is shown,
  which depends on the longitude of the source region. Enhancements in
  Fe/C and other heavy elements relative to C occur when source regions
  are near west 60 deg; the enhancements are attributed to the sampling
  of a flare-heated material. Depletions of these elements are found to
  be greatest for source regions near central meridian; they are matched
  by a steepening of the spectrum and can be understood in terms of
  diffusive shock acceleration.

---------------------------------------------------------
Title: Solar Abundances from Gamma-Ray Spectroscopy: Comparisons
    with Energetic Particle, Photospheric, and Coronal Abundances
Authors: Murphy, R. J.; Ramaty, R.; Kozlovsky, B.; Reames, D. V.
1991ApJ...371..793M    Altcode:
  Accelerated particle and ambient gas abundances have been derived using
  solar flare gamma-ray spectroscopy. The results with photospheric
  and coronal abundances, as well as with solar energetic particle
  abundances. This is the first time that the composition of accelerated
  particles interacting in an astrophysical source has been compared with
  the composition of particles escaping from the source. The analysis
  shows that the derived composition of the accelerated particles is
  different from the composition of particles observed in large proton
  flares; rather, it resembles the composition observed in He-3-rich
  flares. The analysis also suggests an ambient gas composition which
  differs from the composition of both the photosphere and the corona.

---------------------------------------------------------
Title: Quiet-Time Properties of Low-Energy (&lt; 10 MeV per Nucleon)
    Interplanetary Ions during Solar Maximum and Solar Minimum
Authors: Richardson, I. G.; Reames, D. V.; Wenzel, K. -P.;
   Rodriguez-Pacheco, J.
1990ApJ...363L...9R    Altcode:
  The abundances and spectra of 1-10 MeV per nucleon protons, He-3, He-4,
  C, O, and Fe have been exmained during solar quiet periods from 1978
  to 1987 in an effort to investigate the recent suggestion by Wenzel et
  al. (1990) that the ions may be of solar origin. It is found that the
  intensities of the ions, other than O, fall by an order of magnitude
  between solar maximum and solar minimum, and that the greater than 1
  MeV per nucleon ions exhibit weak streaming away from the sun. More
  significantly, the quiet-time ions during solar maximum have He-3-rich
  and Fe-rich abundances which are established characteristics of small
  impulsive solar flares. Thus, it is suggested that small unresolved
  impulsive flares make a substantial contribution to the 'quiet-time'
  fluxes. He-4 from these flares may also contribute strongly to the ion
  spectra that were reported for the 35-1600 keV energy range by Wenzel
  et al.

---------------------------------------------------------
Title: Acceleration of Energetic Particles by Shock Waves from Large
    Solar Flares
Authors: Reames, Donald V.
1990ApJ...358L..63R    Altcode:
  Time-intensity profiles for solar proton events are analyzed with
  respect to the acceleration of energetic particles from the ambient
  solar wind by an interplanetary shock. The time-intensity profiles
  are derived from the Helio 1 particle data base for 1974 to 1984. It
  is found that many of the large proton events display a prolonged
  plateau. The Fe/O abundances in the large proton events are studied. It
  is observed that initially the Fe/O ratio is high (about 1.0), but
  after proton intensities increase to about 100 protons/sq cm sr sec
  MeV the Fe/O ratio decreases to a value near 0.1.

---------------------------------------------------------
Title: Energetic Particle Abundances in Solar Electron Events
Authors: Reames, D. V.; Cane, H. V.; von Rosenvinge, T. T.
1990ApJ...357..259R    Altcode:
  The results of a comprehensive search of the ISEE 3 energetic particle
  data for solar electron events with associated increases in elements
  with atomic number Z = 6 or greater are reported. A sample of 90 such
  events was obtained. The events support earlier evidence of a bimodal
  distribution in Fe/O or, more clearly, in Fe/C. Most of the electron
  events belong to the group that is Fe-rich in comparison with the
  coronal abundance. The Fe-rich events are frequently also He-3-rich
  and are associated with type III and type V radio bursts and impulsive
  solar flares. Fe-poor events are associated with type IV bursts and with
  interplanetary shocks. With some exceptions, event-to-event enhancements
  in the heavier elements vary smoothly with Z and with Fe/C. In fact,
  these variations extend across the full range of events despite inferred
  differences in acceleration mechanism. The origin of source material
  in all events appears to be coronal and not photospheric.

---------------------------------------------------------
Title: Energetic Particles from Impulsive Solar Flares
Authors: Reames, Donald V.
1990ApJS...73..235R    Altcode:
  Observations of solar energetic particles from impulsive flares are
  reviewed. Consideration is given to observations of electron events,
  He-3 rich events, and heavy-nuclei-rich events. It is found that these
  observations can be unified into a description of the particles from
  impulsive flares. The observations are compared with observations of
  gamma-ray line in impulsive flares and particles in flares and compared
  with particles in space. A model for accelerating the unique particle
  abundances of energetic particles is proposed.

---------------------------------------------------------
Title: Solar Neutron Decay Proton Observations in Cycle 21
Authors: Evenson, Paul; Kroeger, Richard; Meyer, Peter; Reames, Donald
1990ApJS...73..273E    Altcode: 1990ApJS...73..272E
  Measurement of the flux and energy spectrum of the protons resulting
  from the decay of solar flare neutrons gives unique information on the
  spectrum of neutrons from 5 to 200 MeV. Neutrons from three flares
  have been observed in this manner during solar cycle 21. The use of
  the decay protons to determine neutron energy spectra is reviewed,
  and new and definitive energy spectra are presented for the two large
  flares on June 3, 1982 and April 25, 1984.

---------------------------------------------------------
Title: The Relationship between Energetic Particles and Flare
    Properties for Impulsive Solar Flares
Authors: Cane, H. V.; Reames, D. V.
1990ApJS...73..253C    Altcode:
  The impulsive mode of particle acceleration is studied by searching
  for 0.2-2 MeV electron increases associated with intense type
  III/V bursts. It is found that the presence of a type III/V burst
  in association with a relatively intense flare event indicates the
  acceleration and escape of greater than 100 KeV electrons. A list
  of type III/V electron events is compiled, showing that the majority
  included greater than 10 MeV proton increases, although they were not
  followed by a type II burst. The results suggest that there are two
  different modes of proton acceleration with the second mode becoming
  significant only for larger, gradual flares.

---------------------------------------------------------
Title: The energetic particles: Acceleration, composition, and
    transport (EXPACT) experiment on the ISTP/wind spacecraft
Authors: Reames, D. V.; von Rosenvinge, T. T.; Ramaty, R.; Mason,
   G. M.; Hamilton, D. C.; Forman, M. A.; Webber, W. R.
1990AIPC..203...32R    Altcode: 1990pacr.rept...32R
  The EPACT experiment will measure abundances, spectra and angular
  distributions of particles from 20 keV/amu to 500 MeV/amu. At high
  energies, isotopes will be resolved up through Z=26, at intermediate
  energies elements with 1&lt;Z&lt;82 will be observed at at low energies
  element abundances above Z=2 will be resolved for the first time.

---------------------------------------------------------
Title: POsitron Electron Magnet Spectrometer (POEMS) for the Eos
    Mission
Authors: Evenson, Paul; Wefel, John P.; Swordy, Simon; Streitmatter,
   Robert; Salamon, Michael; Barbier, Louis; Guzik, T. Gregory;
   Magee-Sauer, Karen P.; Mitchell, John W.; Ormes, Jonathan; Ramaty,
   Reuven; Reames, Donald
1990AIPC..203...58E    Altcode: 1990pacr.rept...58E
  The POsitron Electron Magnet Spectrometer (POEMS) has been selected to
  enter definition phase study for flight on one of the Earth Observing
  System (Eos) polar platforms. Following launch, which could comes as
  early as 1997, POEMS will measure the critical positron and electron
  components of the cosmic radiation and utilize this information to trace
  processes occurring within our geospace environment, in solar flares,
  in the solar wind, and elsewhere in the galaxy. In addition, POEMS will
  measure heavier charged particles to complement the electron/positron
  measurements. With POEMS data we will investigate the origin (primary
  or secondary) of galactic positrons, study the charge sign dependence
  of solar modulation over a large fraction of a solar magnetic cycle,
  measure positron and neutral particle emission from solar flares,
  and monitor the temporal variations of the charged intensities and
  energy spectra in the Eos orbit. Two orthogonal charged particle
  telescopes are used, each terminating in a shared bismuth germanate
  (BGO) detector array that also serves as a calorimeter for neutral
  particles, specifically neutrons and gamma-rays from solar flares.

---------------------------------------------------------
Title: The EPACT Experiment for the WIND Spacecraft
Authors: von Rosenvinge, T. T.; Reames, D. V.
1990ICRC....5..125V    Altcode: 1989ICRC....5..125V; 1990ICRC...21e.125V
  The Energetic Particle: Acceleration, Composition and Transport (EPACT)
  experiment for the WIND spacecraft to be launched in late 1992 is
  presented. This experiment is designed to study the acceleration,
  composition and transport of a wide variety of energetic particle
  populations, including particles accelerated in interplanetary shocks,
  particles from solar flares, the anomalous component, and the Galactic
  cosmic rays.

---------------------------------------------------------
Title: Coronal Mass Ejections and the Injection Profiles of Solar
    Energetic Particle Events
Authors: Kahler, S. W.; Reames, D. V.; Sheeley, N. R., Jr.
1990ICRC....5..183K    Altcode: 1989ICRC....5..183K; 1990ICRC...21e.183K
  Previous studies using Skylab and Solwind coronagraph observations have
  shown that almost all E greater than 10 MeV solar energetic proton (SEP)
  events are associated with the occurrence of a coronal mass ejection
  (CME). These earlier studies did not address the relationship between
  the position of the associated CME and the timing of the injection
  of particles into the interplanetary medium. Ten cases are selected
  in which a SEP event observed with the GSFC detectors on the IMP 8 or
  ISEE 3 spacecraft was correlated to a CME well observed by the Solwind
  coronagraph. The height of the leading edge of the CME is compared with
  the particle injection profiles for several energy ranges using the
  solar release times for the particles. The derived injection profiles
  are found to be increasing and sometimes reaching maximum while the
  associated CMEs are at heights of 2-10 Ro.

---------------------------------------------------------
Title: The Origin of Solar Particle Events With Low Fe/O
Authors: Cane, H. V.; Reames, D. V.; von Rosenvinge, T. T.
1990ICRC....5..370C    Altcode: 1990ICRC...21e.370C
  The origins of particle events which have low Fe/O are studied, and
  it is found that the majority are associated with interplanetary
  shocks. Separately Fe/O associated with all strong shocks in the
  same time period are examined. The important role played by shocks
  is substantiated by establishing that the average Fe/O ratio for days
  when a strong shock passes is 0.1, below the average value of 0.2 for
  large solar proton events and the solar wind. The variations of other
  elements are also shown.

---------------------------------------------------------
Title: Solar Energetic Particles as Probes of the Structures of
    Magnetic Clouds
Authors: Kahler, S. W.; Reames, D. V.
1990ICRC....5..245K    Altcode: 1990ICRC...21e.245K
  Two possible closed magnetic topologies are considered for clouds:
  an elongated bottle with field lines rooted at both ends in the
  sun and a magnetic bubble or plasmoid consisting of closed field
  lines. Solar energetic particles (SEPs) are used as probes of the
  cloud topologies. The rapid access of SEPs to clouds in many events
  indicates that the cloud field lines extend back to the sun.

---------------------------------------------------------
Title: Positron Electron Magnet Spectrometer (POEMS) for the Eos
    Mission
Authors: Evenson, P.; Wefel, P. J.; Swordy, S.; Streitmatter, R.;
   Salamon, M.; Barbier, L.; Guzik, G. T.; Magee-Sauer, P. K.; Mitchell,
   W. J.; Ormes, J.; Ramaty, R.; Reames, D.
1990ICRC....3..265E    Altcode: 1989ICRC....3..265E; 1990ICRC...21c.265E
  No abstract at ADS

---------------------------------------------------------
Title: Energetic-Particle Abundances in Impulsive Solar Flares
Authors: Reames, D. V.; Cane, H. V.; von Rosenvinge, T. T.
1990ICRC....5..108R    Altcode: 1989ICRC....5..108R; 1990ICRC...21e.108R
  The abundances of elements and of He-3 in 90 solar electron events
  have been examined. It is found that the events fall into two distinct
  groups based upon their F/C ratio. Events in the F-rich group frequently
  have high He-3/He-4 ratios and are associated with type III and type
  V radio bursts in the parent flare. The F-poor events are associated
  with type IV bursts. These results on individual events support the
  conclusions of earlier work done with daily-averaged abundances.

---------------------------------------------------------
Title: Solar Flare Nuclear Gamma Rays and Interplanetary Proton Events
Authors: Cliver, E. W.; Forrest, D. J.; Cane, H. V.; Reames, D. V.;
   McGuire, R. E.; von Rosenvinge, T. T.; Kane, S. R.; MacDowall, R. J.
1989ApJ...343..953C    Altcode:
  Gamma-ray line (GRL) and solar energetic proton (SEP) events observed
  from February 1980 through January 1985 are compared in order to
  substantiate and better characterize the lack of correlation between
  GRL fluences and SEP event peak fluxes. The scatter plot of SEP event
  peak flux vs. GRL fluence is presented, and the ratio of 'solar' to
  'interplanetary', about 10 MeV protons, is presented. It is shown that,
  while even large SEP events can originate in flares lacking detectable
  GRL emission, the converse case of flares with a significant GRL line
  fluence by lacking protons in space is rare. The ratio R of the number
  of about 10 MeV protons that produce GRL emission at the flare site
  to the number of about 10 MeV protons detected in space can vary from
  event to event by four orders of magnitude. There is a clear tendency
  for impulsive flares to have larger values of R than long-duration
  flares, where the flare time scale is given by the e-folding decay
  time of the associated soft X-ray emission.

---------------------------------------------------------
Title: Wave Generation in the Transport of Particles from Large
    Solar Flares
Authors: Reames, Donald V.
1989ApJ...342L..51R    Altcode:
  The growth rate of Alfven waves produced by energetic solar
  protons streaming outward from large solar flares is estimated. The
  mathematical development is directly analogous to that used to describe
  the self-containment of cosmic rays in the Galaxy. It is found that
  sufficient intensities of streaming protons can generate Alfven waves
  that reduce the scattering mean free path of the particles that produce
  the waves. This scattering impedes further flow of particles. The
  estimated growth rate of the waves depends linearly upon the particle
  intensity so that lower energy particles are much more strongly affected
  than high-energy particles for typical solar spectra.

---------------------------------------------------------
Title: The Properties of Energetic Particles Associated with Type
    III Bursts
Authors: Cane, H. V.; Reames, D. V.
1989BAAS...21..836C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar Energetic Particles as Probes of the Structure of
    Magnetic Clouds
Authors: Kahler, S. W.; Reames, D. V.; McGuire, R. E.
1989BAAS...21Q.857K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar particle composition, spectra, and frequency of
    occurrence
Authors: Reames, D. V.
1989AIPC..186...86R    Altcode: 1989herb.book...86R
  The radiation background from solar-particle events can assume different
  forms as the energy and composition of the particles changes from
  event to event. It has recently become clear that different particle
  composition and spectra arise from different classes of events at
  the sun and we have learned how to associate the properties of the
  particles with the radio, X-ray and optical observations of the parent
  flares or with the related interplanetary shock.

---------------------------------------------------------
Title: An explanation of the correlation between <SUP>3</SUP>He rich
    flares and non-relativistic electron events.
Authors: Cargill, P. J.; Ramadurai, S.; Reames, D. V.
1989BAAS...21.1027C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The role of interplanetary shocks in the longitude distribution
    of solar energetic particles
Authors: Cane, H. V.; Reames, D. V.; von Rosenvinge, T. T.
1988JGR....93.9555C    Altcode:
  A study of solar proton events with well-identified sources has
  been carried out using data from Goddard particle experiments on
  IMPs 4, 5, 7, and 8 and ISEE 3. The experiments cover the energy
  range from about 1 to 300 MeV. The 235 events of our study represent
  approximately 70% of all increases above 10<SUP>-</SUP><SUP>3</SUP>
  particles cm<SUP>-</SUP><SUP>2</SUP> sr<SUP>-</SUP><SUP>1</SUP>
  MeV<SUP>-</SUP><SUP>1</SUP> at energies &gt;20 MeV detected
  in a 19.7-year period commencing mid-May 1967. It is shown that
  intensity-time profiles of solar proton events display an organization
  with respect to heliolongitude. Whilst it has been known for many years
  that the profile of a proton event depends on the longitude of the solar
  event relative to the observer, we suggest that the major controlling
  agent is the existence of an interplanetary (IP) shock. Furthermore, we
  explain the change in shape as a function of heliolongitude within the
  framework of a recently derived model for the large-scale structure of
  IP shocks. In particular, the long delay to maximum intensity for far
  eastern events (a property previously ascribed to coronal processes)
  and the overall extended duration can be accounted for by IP shock
  acceleration and continued magnetic connection to the shock even after
  it has propagated beyond 1 AU.

---------------------------------------------------------
Title: Solar Neon Abundances from Gamma-Ray Spectroscopy and 3He-rich
    Particle Events
Authors: Reames, D. V.; Ramaty, R.; von Rosenvinge, T. T.
1988ApJ...332L..87R    Altcode:
  The authors compare ambient solar atmospheric abundances derived
  from gamma-ray spectroscopy with observations of solar energetic
  particles. They find agreement between the gamma-ray derived Ne/O ratio
  and the corresponding mean ratio for <SUP>3</SUP>He-rich flares. Both
  of these values are significantly higher than inferred coronal Ne/O
  ratios. It is suggested that the mean Ne/O ratio in <SUP>3</SUP>He-rich
  flares reflects the composition of the flare plasma rather than the
  acceleration process.

---------------------------------------------------------
Title: Bimodal Abundances in the Energetic Particles of Solar and
    Interplanetary Origin
Authors: Reames, Donald V.
1988ApJ...330L..71R    Altcode:
  This letter reports the first results from an examination of the
  daily-averaged abundances of the elements from H through Fe as well
  as electrons and isotopes of He in energetic particles observed
  in interplanetary space by the ISEE 3 spacecraft over an 8.5 yr
  period. The abundances of heavy elements such as Fe/O show, for the
  first time, clear evidence of the presence of two distinct populations
  of particles. Earlier observations could be interpreted as extreme
  variations within a single population. The population with enhanced
  Fe/O shows correlated enhancements in He-3/He-4, p/e, and He/H. This
  population is consistent with material that has been processed to high
  temperatures in the impulsively heated regions of solar flares. The
  second population, with more normal abundances, is probably accelerated
  from ambient material by coronal and interplanetary shocks.

---------------------------------------------------------
Title: X-Ray and Radio Properties of Solar 3He-rich Events
Authors: Reames, D. V.; Dennis, B. R.; Stone, R. G.; Lin, R. P.
1988ApJ...327..998R    Altcode:
  Radio and X-ray properties of solar flares associated with a new sample
  of individual (He-3) rich solar particle events are examined. Given the
  association between kilometric type III bursts and (He-3) rich events,
  the timing of the radio events is used to identify the related X-ray
  increases. The X-ray events exhibit a rich variety, from the standpoint
  of both intensity and complexity. Examination of the events shows
  statistically significant anticorrelations between the He-3/He-4 ratio
  and the intensity of the event as measured at kilometric wavelengths
  and in hard and soft X-rays; larger He-3/He-4 ratios occur in smaller
  flares. The result suggests that a coupling may exist between the
  preheating phase and the acceleration phase of these events or that
  mixing occurs between an enriched particle population accelerated
  within the compact flare and a normal population accelerated by a
  shock propagating away from an intense flare.

---------------------------------------------------------
Title: Solar Flare Nuclear Gamma Rays and Interplanetary Proton Events
Authors: Cliver, E. W.; Forrest, D. J.; McGuire, R. E.; von Rosenvinge,
   T. T.; Reames, D. V.; Cane, H. V.; Kane, S. R.; MacDowall, R. J.
1988BAAS...20..740C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Temperature Dependence of the Abundances of Elements in Solar
    3He-rich Events
Authors: Reames, D. V.
1988ApJ...325L..53R    Altcode:
  The element abundances in solar He-3-rich events are observed to vary
  with the soft X-ray temperature of the parent flare. The observations
  are consistent with thermal collisional ionization of the elements to
  the equilibrium-charge states expected within the flare-heated plasma at
  (10-15) x 10 to the 6th K. Proposed photoionization mechanisms appear
  to be excluded. Rapid ionization of the ions requires that the heating
  occur sufficiently low in the corona that the electron density exceed
  about (1-5) x 10 to the 8th/cu cm. Heavy-element enhancements might
  be a signature of material processed in the flash phase of events in
  contrast to unheated ambient material accelerated by a coronal shock.

---------------------------------------------------------
Title: Soft X-Ray Emissions, Meter-Wavelength Radio Bursts, and
    Particle Acceleration in Solar Flares
Authors: Cane, H. V.; Reames, D. V.
1988ApJ...325..895C    Altcode:
  A detailed study of the relationship between metric radio bursts and
  soft X-ray flares has been made using an extensive data set covering
  15 yr. It is found that type IV emission is mainly associated with
  long-duration 1-8 A events that are known to be well associated with
  coronal mass ejections. In contrast, type II and type III bursts
  originate primarily in impulsive soft X-ray events that are not
  necessarily accompanied by mass ejection. Strong type III bursts,
  in particular, appear to occur only in association with relatively
  impulsive flares. It is suggested that coronal shocks responsible for
  type II bursts are blast waves generated in impulsive energy releases.

---------------------------------------------------------
Title: Some Statistics of Solar Radio Bursts of Spectral Types II
    and IV
Authors: Cane, H. V.; Reames, D. V.
1988ApJ...325..901C    Altcode:
  The properties of meter wavelength solar emissions are studied using a
  sample of all type II and type IV radio bursts detected by the Culgoora
  radio observatory during 1968-1983. It is found that type IV emission
  generally occurs in conjunction with type II emission. For type III
  bursts preceding type II bursts, the delay to type II onset is 6.5
  min on average. The intensities and durations of type II bursts are
  not dependent on the heliolongitude of the associated flares.

---------------------------------------------------------
Title: Characteristics of solar coronal source regions producing
    <SUP>3</SUP>He-rich particle events
Authors: Kahler, S. W.; Lin, R. P.; Reames, D. V.; Stone, R. G.;
   Liggett, M.
1987SoPh..107..385K    Altcode:
  We use Hα, X-ray, and kilometric radio data to examine
  the solar coronal activity associated with energetic (∼1
  MeV/nucl<SUP>−1</SUP>) <SUP>3</SUP>He-rich particle events observed
  near Earth. The basis of the study is the 12 <SUP>3</SUP>He-rich
  events observed in association with impulsive 2 to 100 keV electron
  events reported by Reames et al. (1985). We find that when Hα and
  X-ray brightenings can be associated with <SUP>3</SUP>He/electron
  events, they have onsets coinciding to within 1 min of that of the
  associated metric type III bursts. In three or four events we found
  no associated Hα or X-ray flares, and in two events even the metric
  type III bursts were weak or absent. The measured low-energy (2 keV)
  electron spectra for these events show no evidence of a flattening due
  to Coulomb collisional losses. These results and several other recent
  findings are consistent with the idea that the <SUP>3</SUP>He/electron
  events are due to particle acceleration in the corona well above the
  associated Hα and X-ray flares.

---------------------------------------------------------
Title: Solar Flare Nuclear Gamma-Rays and Interplanetary Proton Events
Authors: Cane, H. V.; Cliver, E. W.; Forrest, D. J.; Kane, S. R.;
   McGuire, R. E.; Reames, D. V.; von Rosenvinge, T. T.
1987ICRC....3...61C    Altcode: 1987ICRC...20c..61C
  No abstract at ADS

---------------------------------------------------------
Title: The Reappearance of the Anomalous Oxygen Component at 1 A.U.
Authors: von Rosenvinge, T. T.; Reames, D. V.
1987ICRC....3..434V    Altcode: 1987ICRC....3..434R; 1987ICRC...20c.434V
  No abstract at ADS

---------------------------------------------------------
Title: Solar Energetic Proton Events and Coronal Mass Ejections Near
    Solar Minimum
Authors: Kahler, S. W.; Cliver, E. W.; Cane, H. V.; McGuire, R. E.;
   Reames, D. V.; Sheeley, N. R., Jr.; Howard, R. A.
1987ICRC....3..121K    Altcode: 1987ICRC...20c.121K; 1987ICRC....3..121C
  No abstract at ADS

---------------------------------------------------------
Title: X-Ray and Radio Emission in Solar (3)HE-RICH Events
Authors: Reames, D. V.; Lin, R. P.; Sonte, R. L.; Dennis, B. R.
1987ICRC....3..271R    Altcode: 1987ICRC...20c.271R; 1987ICRC....3..271D
  No abstract at ADS

---------------------------------------------------------
Title: On the Sources of Solar Energetic Particles
Authors: Cane, H. V.; Reames, D. V.; von Rosenvinge, T. T.
1987ICRC....3..217C    Altcode: 1987ICRC...20c.217C
  No abstract at ADS

---------------------------------------------------------
Title: The Identification of Solar 3He-rich Events and the Study of
    Particle Acceleration at the Sun
Authors: Reames, D. V.; Stone, R. G.
1986ApJ...308..902R    Altcode:
  Kilometric radio observations are to associate type III radio bursts
  with solar He-3-rich events and to identify and study the sources of
  those events at the sun and the transport of the particles outward
  toward earth. The events exhibit an impulsive behavior that earns
  them a natural role in the event classification scheme based upon the
  time scale of the particle acceleration process. Multiple He-3-rich
  events are observed frequently from a single active region where they
  provide a convenient signature to test theories of particle storage
  and transport. These multiple events act as impulsive probes of the
  condition of the interplanetary medium. Their profiles contrast with
  the source-acceleration-induced profiles of the long-duration events
  from the same active region that are interspersed among them.

---------------------------------------------------------
Title: The Heavy-Ion Compositional Signature in 3He-rich Solar
    Particle Events
Authors: Mason, G. M.; Reames, D. V.; Klecker, B.; Hovestadt, D.;
   von Rosenvinge, T. T.
1986ApJ...303..849M    Altcode:
  A survey of the approx. 1 MeV/nucleon heavy ion abundances
  in 66 He-3-rich solar particle events was performed using the
  Max-Planck-Institut/University of Maryland and Goddard Space Flight
  Center instruments on the ISEE-3 spacecraft. The observations were
  carried out in interplanetary space over the period 1978 October
  through 1982 June. Earlier observations were confirmed which show an
  enrichment of heavy ions in He-3-rich events, relative to the average
  solar energetic particle composition in large particle events. For
  the survey near 1.5 MeV/nucleon the enrichments compared to large
  solar particle events are approximately He4:C:O:Ne:Mg:Si:Fe =
  0.44:0.66:1.:3.4:3.5:4.1:9.6. Surprising new results emerging from
  the present broad survey are that the heavy ion enrichment pattern
  is the same within a factor of approx. 2 for almost all cases, and
  the degree of heavy ion enrichment is uncorrelated with the He-3
  enrichment. Overall, the features established appear to be best
  explained by an acceleration mechanism in which the He-3 enrichment
  process is not responsible for the heavy ion enrichment, but rather the
  heavy ion enrichment is a measure of the ambient coronal composition
  at the sites where the He-3-rich events occur.

---------------------------------------------------------
Title: The heavy ion compositional signature in 3He-rich solar
    particle events
Authors: Mason, G. M.; Reames, D. V.; Klecker, B.; Hovestadt, D.;
   von Rosenvinge, T. T.
1985STIN...8617255M    Altcode:
  A survey of the approx. 1 MeV/nucleon heavy ion abundances
  in 66 He3-rich solar particle events was performed using the
  Max-Planck-Institut/University of Maryland and Goddard Space Flight
  Center instruments on the ISEE-3 spacecraft. The observations were
  carried out in interplanetary space over the period 1978 October
  through 1982 June. Earlier observations were confirmed which show an
  enrichment of heavy ions in HE3-rich events, relative to the average
  solar energetic particle composition in large particle events. For
  the survey near 1.5 MeV/nucleon the enrichments compared to large
  solar particle events are approximately He4:C:O:Ne:Mg:Si:Fe =
  0.44:0.66:1.:3.4:3.5:4.1:9.6. Surprising new results emerging from
  the present broad survey are that the heavy ion enrichment pattern
  is the same within a factor of approx. 2 for almost all cases,
  and the degree of heavy ion enrichment is uncorrelated with the
  He3 enrichment. Overall, the features established appear to be best
  explained by an acceleration mechanism in which the He3 enrichment
  process is not responsible for the heavy ion enrichment, but rather the
  heavy ion enrichment is a measure of the ambient coronal composition
  at the sites where the He3-rich events occur.

---------------------------------------------------------
Title: **3HE in Solar Non-Relativistic Electron Events
Authors: Reames, D. V.; Lin, R. P.; Reames, D. V.
1985ICRC....4..273R    Altcode: 1985ICRC...19d.273R
  The authors report on a systematic study of the presence of
  <SUP>3</SUP>He in 187 solar electron events observed on the ISEE-3
  spacecraft during a 9-month period beginning in Aug 1978. <SUP>3</SUP>He
  is present in over half of the events and in 2/3 of events with 19
  keV electrons, suggesting that <SUP>3</SUP>He would be found in all
  electron events given somewhat greater collection efficiency.

---------------------------------------------------------
Title: Solar Source Regions of 3**HE-RICH Particle Events
Authors: Kahler, S. W.; Lin, R. P.; Reames, D. V.; Stone, R. G.;
   Liggett, M.
1985ICRC....4..269K    Altcode: 1985ICRC...19d.269K
  Hydrogen alpha X-ray, and metric and kilometric radio data to examine
  the solar sources of energetic 3He-rich particle events observed near
  earth in association with impulsive 2 to 100 keV electron events were
  applied. Each 3He/electron event is associated with a kilometric type
  3 burst belonging to a family of such bursts characterized by similar
  interplanetary propagation paths from the same solar active region. The
  3He/electron events correlate very well with the interplanetary low
  frequency radio brightnesses of these events, but progressively worse
  with signatures from regions closer to the Sun. When H alpha brightnings
  can be associated with 3He/electron events, they have onsets coinciding
  to within 1 min of that of the associated metric type 3 burst but
  are often too small to be reported. The data are consistent with the
  earlier idea that many type 3 bursts, the 3He/electron events, are
  due to particle acceleration in the corona, well above the associated
  H alpha and X-ray flares.

---------------------------------------------------------
Title: The Heavy Ion Composition in **3HE-RICH Solar Flares
Authors: Mason, G. M.; Reames, D. V.; Hovestadt, D.; von Rosenvinge,
   T. T.
1985ICRC....4..281M    Altcode: 1985ICRC...19d.281M
  The 3He-rich flares show a tendency to be enriched in heavy ions, and
  that this enrichment covers the charge range through Fe. The discovery
  of this association was responsible, in part, for the discarding of
  3He enrichment models which involved spallation or thermonuclear
  reactions, since such models were unable to produce heavy nuclei
  enhancement. Results of a survey of heavy nucleus abundances observed
  in 66 3He-rich flares which occurred over the period October 1978 to
  June 1982 are presented.

---------------------------------------------------------
Title: Variation in Elemental Composition of Several Mev/nucleon
    Ions Observed in Interplanetary Space
Authors: McGuire, R. E.; von Rosenvinge, T. T.; Reames, D. V.
1985ICRC....4..225M    Altcode: 1985ICRC...19d.225M
  The authors have surveyed six years of accumulated ISEE-3 and IMP-8
  data to study variations in elemental relative abundances among the
  different populations of energetic (1.5 to &gt;10 MeV/nuc) ions seen in
  interplanetary space. They present evidence suggestive that heavy ion
  enrichments may be organized (with substantial scatter) by a rigidity
  scaling factor A/Z<SUP>*</SUP> over the range H to Fe. They also show
  some data to support the hypothesis that shock-associated particles
  are probably accelerated from ambient energetic fluxes.

---------------------------------------------------------
Title: Type III Solar Radio Bursts and **3HE-RICH Events
Authors: Reames, D. V.; Stone, R. G.
1985ICRC....4..265R    Altcode: 1985ICRC...19d.265R
  The authors investigate the kilometric radio data for
  <SUP>3</SUP>He-rich events during the 1979 - 82 time period. Type
  III bursts are present for each event as expected from the previous
  electron/<SUP>3</SUP>He-event association. A list of identified solar
  events is presented.

---------------------------------------------------------
Title: Solar He-3-rich events and nonrelativistic electron events -
    A new association
Authors: Reames, D. V.; von Rosenvinge, T. T.; Lin, R. P.
1985ApJ...292..716R    Altcode:
  In 15 months of observation by the ISEE-e spacecraft, it was found
  that virtually all solar greater than or approximately equal to
  1.3 MeV/nucleon He-3-rich events are associated with impulsive 2
  to approximately 100 keV electron events, although many electron
  events were not accompanied by detectable He-3 increases. Both the
  He-3 and the electrons exhibit nearly scatter-free propagation in the
  interplanetary medium, and the times of onset and maximum for the He-3
  and electron increases are closely related by velocity dispersion. The
  electron events and their related type III solar radio bursts provide,
  for the first time, identification of the flares which produce the
  He-3-rich events. He-3 appears to be accelerated at the flash phase
  of solar flares along with nonrelativistic electrons.

---------------------------------------------------------
Title: A comparison of solar helium-3-rich events with type II bursts
    and coronal mass ejections
Authors: Kahler, S.; Reames, D. V.; Sheeley, N. R., Jr.; Howard,
   R. A.; Michels, D. J.; Koomen, M. J.
1985ApJ...290..742K    Altcode:
  The authors ask whether the energetic particles of <SUP>3</SUP>He-rich
  events are accelerated in the same process as that resulting in
  particles of normal-abundance events. They first present a list
  of 66 <SUP>3</SUP>He-rich events observed with the Goddard Space
  Flight Center particle detector on ISEE 3. It is then shown that
  these events are not statistically associated with either of the two
  common signatures of normal-abundance events, metric type II bursts
  and coronal mass ejections. This indicates that enhanced abundance
  events may be produced only in the impulsive phases of flares, while
  normal abundance events are produced in subsequent flare shock waves.

---------------------------------------------------------
Title: Solar He-3-rich events and non-relativistic electron events:
    A new association
Authors: Reames, D. V.; von Rosenvinge, T. T.; Lin, R. P.
1984STIN...8515652R    Altcode:
  In 15 months of observation by the ISEE-e spacecraft, it was found
  that virtually all solar greater than or approximately equal to
  1.3 MeV/nucleon He-3-rich events are associated with impulsive 2 to
  approximately 100 keV electron events, although many electron events
  were not accompanied by detectable He-3 increases. Both the He-3 and the
  electrons exhibit nearly scatter-free propagation in the interplanetary
  medium, and the times of onset and maximum for the He-3 and electron
  increases are closely related by velocity dispertion. The electron
  events and their related type III solar radio bursts provide, for
  the first time, identification of the flares which produce He-3-rich
  events. He-3 appears to be accelerated at the flash phase of solar
  flares along with nonrelativistic electrons.

---------------------------------------------------------
Title: Associations beteen coronal mass ejections and solar energetic
    proton events
Authors: Kahler, S. W.; Sheeley, N. R., Jr.; Howard, R. A.; Michels,
   D. J.; Koomen, M. J.; McGuire, R. E.; von Rosenvinge, T. T.; Reames,
   D. V.
1984JGR....89.9683K    Altcode:
  We have used data from the Naval Research Laboratory (NRL) white
  light coronograph on the P78-1 spacecraft and energetic (E&gt;4 MeV)
  proton data from the Goddard Space Flight Center (GSFC) detectors
  on the IMP 8 and ISEE 3 spacecraft to investigate the association
  between proton events originating in flares and coronal mass ejections
  (CME's). The primary data were 50 prompt proton events observed between
  April 1979 and February 1982 for which reduced coronograph data were
  available. H alpha flares could be confidently associated with 27 of
  these events, and in 26 of these 27 cases an associated CME was found,
  indicating a high but not perfect association of prompt proton events
  with CME's. Peak proton fluxes correlate with both the speeds and the
  angular sizes of the associated CME's. We show that the CME speeds do
  not significantly correlate with CME angular sizes, so that the peak
  proton fluxes are correlated with two independent CME parameters. With
  larger angular sizes, CME's are more likely to be loops and fans
  rather than jets and spikes and are more likely to intersect the
  ecliptic. Which of these factors is important to the peak proton flux
  correlation cannot be determined from the data. We find weak evidence
  that steeper proton spectra are associated with faster and wider
  CME's. Two of the 50 proton events of the study and two additional
  events, all with no associated CME's share common characteristics:
  relatively short duration (~1) day proton events with low fluxes,
  parent flares with short (~10 min) soft x ray duration, close magnetic
  connection to the earth, and gamma ray and metric type II emission.

---------------------------------------------------------
Title: Solar Energetic Proton Events Unassociated with Coronal
    Mass Ejections
Authors: Kahler, S.; Evenson, P.; McGuire, R. E.; Reames, D. V.;
   von Rosenvinge, T. T.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen,
   M. J.; Michels, D. J.
1984BAAS...16..453K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Correlation of Coronal Mass Ejections with Energetic
    Flare Proton Events
Authors: Kahler, S. W.; McGuire, R. E.; Reames, D. V.; von Rosenvinge,
   T. T.; Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen,
   M. J.
1983ICRC....4....6K    Altcode: 1983ICRC...18d...6K
  Proton events of energies of at least 4 MeV presumed due to solar
  flares are compared with coronal mass ejections (CMEs) observed with
  an orbiting coronagraph. H alpha flares are associated with 27 of
  the 50 flare proton events of the study. Each of these 27 flares
  is then associated temporally and spatially with a CME, confirming
  the earlier conclusion, based on Skylab data, that a CME may be a
  necessary condition for a flare proton event. Peak 4-22 MeV proton
  fluxes correlate with both the speeds and the angular sizes of the
  associated CMEs. CMEs of larger angular sizes are more likely to
  be loops or fans rather than jets or spikes and are more likely to
  intersect the ecliptic.

---------------------------------------------------------
Title: Association of interplanetary particles with radio S.A. (shock
    acceleration) events.
Authors: von Rosenvinge, T. T.; Reames, D. V.; Cane, H. V.
1983ICRC....4...10V    Altcode: 1983ICRC...18d..10V
  No abstract at ADS

---------------------------------------------------------
Title: Solar <SUP>3</SUP>HE-RICH Events Observed on ISEE-3
Authors: Reames, D. V.; von Rosenvinge, T. T.
1983ICRC....4...48R    Altcode: 1983ICRC...18d..48R
  A scan has been made of ISEE-3 data for all events with He-3/He-4
  between 0.20 and 1.3 MeV/nucl. The 67 events found show some evidence
  of 27-day recurrence. Larger events show both velocity dispersion
  and magneic field-aligned arrival from the solar direction. At
  least one third of the events are preceded by increases in about
  300 keV electrons, although several larger events show no electron
  increases. Spike events also exist suggesting nearly scatter-free
  propagation of He-3 from well-connected events.

---------------------------------------------------------
Title: The delayed energetic particle event of June 6 - 10, 1979.
Authors: von Rosenvinge, T. T.; Reames, D. V.
1983ICRC...10..373V    Altcode: 1983ICRC...18j.373V
  Energetic particle observations carried out with the ISEE-3
  Medium-Energy Cosmic Ray experiment during the flare event of June 6-10,
  1979 are reported. An expanded time history of the He nuclei particle
  spectra is given, and particle trajectory angles are identified with
  respect to the earth-sun line. The backward flow of the particle
  stream following the shock was analyzed, and it is found that the
  shock continued to accelerate particles beyond 1 AU from the sun. Polar
  plots of the number of protons counted in each sector of observation
  are given with their corresponding magnetic field directions.

---------------------------------------------------------
Title: The Delayed Energetic Particle Event of June 6, 1979
Authors: Rosenvinge, T. T. V.; Reames, D. V.
1983ICRC....4..148R    Altcode: 1983ICRC...18d.148R
  No abstract at ADS

---------------------------------------------------------
Title: Association of Interplanetary Particles with Radio S. a. Events
Authors: Rosenvinge, T. T. V.; Reames, D. V.; Cane, H. V.
1983ICRC....4...10R    Altcode: 1983ICRC...18d..10R
  No abstract at ADS

---------------------------------------------------------
Title: Associations between Coronal Mass Ejections and Solar Energetic
    Proton Events
Authors: Kahler, S. W.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen,
   M. J.; Michels, D. J.; McGuire, R. E.; von Rosenvinge, T. T.; Reames,
   D. V.
1983BAAS...15..699K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Heavy-Element Abundances in HE3 - Rich Events
Authors: Reames, D. V.; von Rosenvinge, T. T.
1981ICRC....3..162R    Altcode: 1981ICRC...17c.162R
  Abundances of the elements He through Fe observed on the ISEE-3
  during He(3) rich events are reported. Ratios of He(3)-He(4) of not
  less than about 1, and Fe/O of greater than 1 are found, and rather
  large event-to-event variations in C, O, Ne, Mg, Si, and S are seen
  superposed upon the general trend of heavy element enhancement. It is
  concluded that the discontinuous variation of the neighboring elements
  in the He(3) rich events could result from differences in the electron
  temperature of the material prior to injection that give rise to
  differences in the dominant charge states and cyclotron frequencies
  of different elements.

---------------------------------------------------------
Title: Interplanetary Particle Observations Associated with Solar
    Flare Gamma-Ray Line Emission
Authors: von Rosenvinge, T. T.; Ramaty, R.; Reames, D. V.
1981ICRC....3...28V    Altcode: 1981ICRC...17c..28V
  Observations of particle emissions during three solar flares which were
  observed to emit 2.22 MeV gamma rays as recorded by the Solar Maximum
  Mission are discussed. The 2.22 MeV line is produced by neutron capture
  by hydrogen, and additional attention is given to a 4.4 MeV emission
  line of June 7, 1980, with estimates made of the particle density 1
  AU from the sun assuming a good magnetic connection between the earth
  and the sun. The measurements were made from the ISEE-3 and HELIOS-1
  spacecraft. The connectedness of the earth and the sun in a magnetic
  field leads to conclusions that few particles actually escaped into
  interplanetary space.

---------------------------------------------------------
Title: ISEE-3 Measurements of Solar Energetic Particle Composition
Authors: von Rosenvinge, T. T.; Reames, D. V.
1979ICRC....5...68V    Altcode: 1980ICRC....5...68V; 1979ICRC...16e..68V
  Preliminary observations of energetic particles from solar flares
  beginning on September 23 and November 10, 1978 are reported. The
  measurements were made from the ISEE-3 spacecraft using very thin, large
  area solid-state detectors. Charge composition was measured for all
  elements from Z = 2 to Z = 26 above approximately 2 MeV/nucleon. More
  than 100,000 nuclei with Z greater than 2 were pulse-height analyzed
  during the course of the first event, while the second was substantially
  smaller. These good statistics enable the observation of variations
  in composition at low energies as a function of time. For example,
  the Fe/O ratio (2.0-3.1 MeV/n) was observed in the September event
  to decrease by a factor of approximately 5. By contrast, this same
  ratio increased by a factor of approximately 1.5 during the November
  10 event. Similar variations have been reported earlier by Scholer
  et al. (1978). These authors, however were unable to observe the He/O
  ratio which has now been observed also to show significant variation.

---------------------------------------------------------
Title: Enhancement of solar heavy nuclei at high energies in the 4
    July 1974 event.
Authors: Bertsch, D. L.; Reames, D. V.
1977SoPh...55..491B    Altcode:
  Relative abundances of energetic nuclei in the 4 July 1974 solar event
  are presented. The results show a marked enhancement of abundances
  that systematically increase with nuclear charge numbers in the
  range of the observation, 6 ≤ Z ≤ 26 for energies above 15 MeV
  nucl.<SUP>−1</SUP> While such enhancements are commonly seen below
  10 MeV nucl<SUP>−1</SUP>, most observations at higher energies
  are found to be consistent with solar system abundances. The energy
  spectrum of oxygen is observed to be significantly steeper than most
  other solar events studied in this energy region. It is proposed
  that these observations are characteristic of particle populations at
  energies ∼1 MeV nucl<SUP>−1</SUP>, and that the anomalous features
  observed here may be the result of the high energy extension of such
  a population that is commonly masked by other processes or populations
  that might occur in larger solar events.

---------------------------------------------------------
Title: Enhancement of solar heavy nuclei at high energies in the 4
    July 1974 event
Authors: Bertsch, D. L.; Reames, D.
1976STIN...7715970B    Altcode:
  Relative abundances of energetic nuclei in the 4 July 1974 solar event
  are presented. The results show a marked enhancement of abundances
  that systematically increase with nuclear charge numbers in the range
  of the observation, 6 less than or equal to Z less than or equal
  to 26 for energies above 15 MeV/nucleon. While such enhancements
  are commonly seen below 10 MeV/nucleon, most observations at higher
  energies are found to be consistent with solar system abundances. The
  energy spectrum of oxygen is observed to be significantly steeper than
  most other solar events studied in this energy region. It is proposed
  that these observations are characteristic of particle populations at
  energies approximately 1 MeV/nucleon, and that the anomalous features
  observed here may be the result of the high energy extension of such
  a population that is commonly masked by other processes or populations
  that might occur in larger solar events.

---------------------------------------------------------
Title: Solar Cosmic Ray Composition above 10 MeV/Nucleon and Its
    Energy Dependence in the 4 August 1972 Event
Authors: Bertsch, D. L.; Biswas, S.; Reames, D. V.
1974SoPh...39..479B    Altcode:
  Observations of the proton, helium, (C, N, O) and Fe-group nuclei
  fluxes made during the large 4 August 1972 solar particle event are
  presented. The results show a small, but significant variation of the
  composition of multiply-charged nuclei as a function of energy in the
  energy region above 10 MeV nucleon<SUP>−1</SUP>. In particular, the
  He/(C, N, O) abundance ratio varies by a factor ∼ 2 between 10 and 50
  MeV nucleon<SUP>−1</SUP> and the Fe-group/(C, N, O) ratio suggests a
  similar variation. Abundance ratios from the 4 August 1972 event are
  compared as a function of energy with ratios measured in other solar
  events to show that several of the earlier results are consistent with
  an energy variation like that observed in August 1972, while certain
  other events must have had a substantially different dependence of
  composition on energy. At energies ≳50 MeV nucleon<SUP>−1</SUP>,
  the He/(C, N, O) abundance ratio for August 1972 is consistent with
  all earlier measurements made above that energy which suggests that
  variations may vanish at high energies.

---------------------------------------------------------
Title: The Abundances of Nuclei in the Cosmic Radiation
Authors: Reames, D. V.
1974hepq.conf...54R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Variations of the Relative Abundances of He, (C, N, O) and
    Fe-Group Nuclei in Solar Cosmic Rays and Their Relationship to Solar
    Particle Acceleration
Authors: Bertsch, D. L.; Biswas, S.; Fichtel, C. E.; Pellerin, C. J.;
   Reames, D. V.
1973SoPh...31..247B    Altcode:
  Measurements of the flux of helium nuclei in the 24 January, 1971, event
  and of helium and (C, N, O) nuclei in the 1 September, 1971, event are
  combined with previous measurements to obtain the relative abundances of
  helium, (C, N, O), and Fe-group nuclei in these events. These data are
  then summarized together with previously reported results to show that,
  even when the same detector system using a dE/dx plus range technique is
  used, differences in the He/(C, N, O) value in the same energy/nucleon
  interval are observed in solar cosmic ray events. Further, when
  the He/(C, N, O) value is lower the He/(Fe-group nuclei) value is
  also systematically lower in these large events. When solar particle
  acceleration theory is analyzed, it is seen that the results suggest
  that, for large events, Coulomb energy loss probably does not play a
  major role in determining solar particle composition at higher energies
  (&gt; 10 MeV). The variations in multicharged nuclei composition are
  more likely due to partial ionization during the acceleration phase.

---------------------------------------------------------
Title: Measurements of the Iron-Group Abundance in Energetic Solar
    Particles
Authors: Bertsch, D. L.; Fichtel, C. E.; Pellerin, C. J.; Reames, D. V.
1973ApJ...180..583B    Altcode:
  The abundance of iron-group nuclei in the energetic solar particles
  was measured twice in the 1971 January 24 event and once in the 1971
  September 2 event. Including earlier results from the 1966 September
  2 event, the experimental series being discussed in this article has
  found the iron- group abundance to be in the range from 3-6 percent
  of the oxygen nuclei in the energy interval from 21 to 50 MeV per
  nucleon, in those events where the iron-group abundance could be
  measured. Iron-nuclei have a different charge-to-mass ratio from
  that of the C, N, 0 nuclei, so small variations in the Fe abundance
  in solar particles are not unexpected due to rigidity-dependent
  propagation effects and possibly rigidity-dependent acceleration. In
  the three exposures where the statistics were adequate to construct
  an energy spectrum, the iron-group nuclei were seen to have an
  energy per nucleon spectrum similar to that of the C, N, 0 nuclei;
  however, the energy per nucleon range was limited. The abundance for
  the iron-group nuclei mentioned above is consistent with the present
  solar spectroscopic abundance estimates. Subject headings: abundances,
  cosmic-ray abundances, solar

---------------------------------------------------------
Title: Composition of Cosmic Rays in the January 24 and September 2,
    1971 Solar Events
Authors: Fichtel, C. E.; Bertsch, D. L.; Biswas, S.; Pellerin, C. J.;
   Reames, D. V.
1973BAAS....5R.272F    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Measurements of Solar Protons, Helium and Heavy Nuclei in
    the Aug. 4, 1972 Solar Event
Authors: Biswas, S.; Bertsch, D. L.; Fichtel, C. E.; Pellerin, C. J.;
   Reames, D. V.
1973BAAS....5T.269B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Relative Abundances and Energy Spectra of Solar Cosmic Ray
    Nuclei in the August 4, 1972 Event
Authors: Biswas, S.; Bertsch, D. L.; Fichtel, C. E.; Pellerin, C.;
   Reames, D. V.
1973ICRC....2.1543B    Altcode: 1973ICRC...13.1543B
  No abstract at ADS

---------------------------------------------------------
Title: Variations in the Nuclear Abundances in Solar Particle Events
Authors: Bertsch, D. L.; Biswas, S.; Fichtel, C. E.; Pellerin, C. J.;
   Reames, D. V.
1973ICRC....2.1526B    Altcode: 1973ICRC...13.1526B
  No abstract at ADS

---------------------------------------------------------
Title: Solar Cosmic Ray Composition Measured With Nuclear Emulsions
    Flown On Sounding Rockets During 1971
Authors: Fichtel, C. E.; Bertsch, D. L.; Pellerin, C. J.; Reames, D. V.
1972BAAS....4Q.382F    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Nuclear Composition and Energy Spectra in the 1969 April 12
    Solar-Particle Event
Authors: Bertsch, D. L.; Fichtel, C. E.; Reames, D. V.
1972ApJ...171..169B    Altcode:
  The charge composition for several of the multicharged nuclei and
  the energy spectra for hydrogen, helium, and medium (6 &lt; Z &lt; 9)
  nuclei were measured in the 1969 April 12 solar-particle event. The
  energy/nucleon shape of the medium nuclei was again the same as that of
  the helium nuclei, and the ratio of these two species was consistent
  with the present best average of 58 * 5. By combining the results
  obtained here with previous work, improved estimates of the Ne/O
  and Mg/O values of 0.16 * 0.03 and 0.056 i 0.014, respectively, were
  obtained. Silicon and sulfur abundances relative to 0 were determined
  to be 0.208 i 0.010 and 0.008 i 0.006, respectively, and 85 percent
  confidence upper limits for Ar and Ca relative to 0 of 0.017 and 0.010
  were obtained. Previously, these last four nuclei had only been listed
  as a group.

---------------------------------------------------------
Title: Solar Particle Composition Measurements
Authors: Reames, Donald V.
1972NASSP.312..122R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar Fe abundance deduced from solar particle measurements
    made with nuclear emulsions.
Authors: Fichtel, C. E.; Bertsch, D. L.; Pellerin, C. J.; Reames, D. V.
1972BAAS....4S.259F    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A comparison of measurements of the charge spectrum of solar
    cosmic rays from nuclear emulsions and the Explorer 35 solid-state
    detector
Authors: Armstrong, T. P.; Krimigis, S. M.; Reames, D. V.; Fichtel,
   C. E.
1972JGR....77.3607A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Charge Composition of Solar Cosmic Rays.
Authors: Bertsch, D. L.; Fichtel, C. E.; Reames, D. V.
1971ICRC....2..455B    Altcode: 1971ICRC...12..455B
  No abstract at ADS

---------------------------------------------------------
Title: ^{53}Mn and the Age of Galactic Cosmic Rays
Authors: Reames, Donald V.
1970ApJ...162..837R    Altcode:
  A new measurement is suggested for obtaining information on the mean
  age of the galactic cosmic rays. The technique is based on a half-life
  of 2 X 10' years for 53Mn which may be produced copiously below 200
  MeV per nucleon by the fragmentation of cosmic-ray 56Fe during its
  passage through interstellar or intergalactic hydrogen.

---------------------------------------------------------
Title: Statistical Discrete-Source Model of Local Cosmic Rays
Authors: Ramaty, R.; Reames, D. V.; Lingenfelter, R. E.
1970PhRvL..24..913R    Altcode:
  The anisotropy, lifetime, and fluctuations of the cosmic rays are
  considered for a model in which the cosmic-ray sources are random
  discrete events in space-time.

---------------------------------------------------------
Title: Chemical Composition of Relativistic Cosmic Rays Detected
    above the Atmosphere
Authors: Durgaprasad, N.; Fichtel, C. E.; Guss, D. E.; Reames, D. V.;
   O'dell, F. W.; Shapiro, M. M.; Silberberg, R.; Stiller, B.; Tsao, C. H.
1970PhRvD...1.1021D    Altcode:
  Final results on the first satellite experiment on abundances of
  cosmic-ray nuclei having a mean energy of several GeV per nucleon
  are presented. A nuclear-emulsion detector, exposed on Gemini XI in
  a near-equatorial orbit ranging between geographic latitudes +/-29°,
  collected 619 high-quality tracks above the earth's atmosphere. Time
  resolution (within about 5 min) was provided by movement of a lower
  emulsion stack relative to an upper one. The detector was covered by
  only 0.07 g/cm<SUP>2</SUP> of aluminum and was favorably oriented for
  18 h. The results on abundances, requiring no correction for secondary
  production in the atmosphere, are characterized by (a) a pronounced
  odd-even effect, with low abundances for elements of atomic number 7,
  9, 11, and 13, compared to those of neighboring elements with even Z;
  (b) approximately equal fluxes of neon, magnesium, and silicon, each
  being about one-fourth that of oxygen; and (c) an abundance gap in the
  region 15&lt;=Z&lt;=19. The observed ratios of Be+B, 10&lt;=Z&lt;=19,
  and Z&gt;=20 to the medium group, 6&lt;=Z&lt;=9, provide no evidence for
  significant variation of composition with rigidity between 3.5 and 30
  GV. A primordial composition-prior to interactions of the cosmic rays
  with the interstellar medium-is calculated. This source composition
  is compared with "universal" and solar abundances.

---------------------------------------------------------
Title: Discrete Sources and the Statistics of Cosmic-Ray Propagation
Authors: Reames, D. V.; Ramaty, R.
1970cora.conf...39R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Composition of relativistic cosmic rays detected on Gemini XI
Authors: O'dell, F. W.; Shapiro, M. M.; Silberberg, R.; Stiller, B.;
   Tsao, C. H.; Durgaprasad, N.; Fichtel, C. E.; Guss, D. E.; Reames,
   D. V.
1970ICRC....1..457O    Altcode: 1970ICRC...11a.457O
  No abstract at ADS

---------------------------------------------------------
Title: Relative Abundance of Iron-Group Nuclei in Solar Cosmic Rays
Authors: Bertsch, D. L.; Fichtel, C. E.; Reames, D. V.
1969ApJ...157L..53B    Altcode:
  The abundance of the iron-group nuclei relative to oxygen in a solar
  cosmic-ray event has been de- termined for the first time in the
  event of September 2, 1966; it was found to be (1.1 ± 0.3) X 1O~
  above 24.5 MeV nucleon1. This ratio is consistent with the solar value
  determined spectroscopically but is over an order of magnitude smaller
  than the galactic cosmic-ray ratio. This result is in agreement with
  the concept already evolving from measurements on other nuclei that
  the relative abundances of solar cosmic rays reflect those of the
  solar photosphere for multicharged nuclei with approximately the same
  nuclear charge-to-mass ratio

---------------------------------------------------------
Title: Iron Nuclei in Solar Cosmic Radiation
Authors: Bertsch, D. L.; Fichtel, C. E.; Reames, D. V.
1969BAAS....1R.273B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The charge composition of solar cosmic rays and solar
    abundances
Authors: Reames, D. V.; Fichtel, C. E.
1969sfsr.conf..277R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Composition of cosmic rays measured in Gemini XI.
Authors: O'Dell, F. W.; Shapiro, M. M.; Silberberg, R.; Stiller, B.;
   Tsao, C. H.; Durgaprasad, N.; Fichtel, C. E.; Guss, D. E.; Reames,
   D. V.
1969spre.conf..215O    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Nuclear-Charge Spectra and Energy Spectra in the September 2,
    1966, Solar-Particle Event
Authors: Durgaprasad, N.; Fichtel, C. E.; Guss, D. E.; Reames, D. V.
1968ApJ...154..307D    Altcode:
  Heavy nuclei (Z »= 3) were detected in the September 2, 1966,
  solar-particle event. This brings to five the number of events in which
  these particles have been detected. The proton energy spectrum was
  measured down to energies as low as 3 MeV and up to energies as high as
  100 MeV, with measurements on the helium and heavier nuclei covering
  a more restricted range. The relative abundances of helium, light (3
  «= Z «= 5), medium (6 «= Z «= 9), and heavier nuclei obtained in
  this experiment in the energy range from about 14 to 35 MeV nucleon'
  agree with those measured in previous solar-particle events at higher
  energies and hence with those of the solar photosphere. This result
  strengthens the concept of a multicharged nuclear composition, which
  is a characteristic of solar-particle events. Use of the recent solar
  spectroscopic data and the ratio of helium to medium nuclei observed
  in the solar cosmic rays results in a hydrogen-to-helium ratio of 16
  ± 2. An examination of the relative abundances of protons and medium
  nuclei shows that the propagation of solar particles in this event
  cannot be described by a simple diffusion model with a diffusion
  coefficient proportional to j3 or 13R

---------------------------------------------------------
Title: The Composition and Energy Spectra of Energetic Particles.
Authors: Reames, D. V.; Fichtel, C. E.
1968AJS....73R..74R    Altcode:
  The composition and energy spectra of particles observed during
  the solar particle event of 2 Sept. 1966 are compared with similar
  measurements on previous events. Perhaps the most striking feature
  of these measurements is the constancy of the relative abundances of
  the multicharged nuclei with time during an event and from event to
  event; this composition is apparently the same as that of the solar
  photosphere. In contrast the proton to helium ratio is observed to
  vary markedly with time and from one event to another. The latter
  observation precludes the possibility of a purely velocity-dependent
  propagation mechanism, and together with the spectral measurements
  shows that any simple diffusion model is probably inadequate.

---------------------------------------------------------
Title: High-energy galactic cosmic-ray composition measured in
    Gemini XI
Authors: O'dell, F. W.; Shapiro, M. M.; Silberberg, R.; Stiller, B.;
   Tsao, C. H.; Durgaprasad, N.; Fichtel, C. E.; Guss, D. E.; Reames,
   D. V.
1968CaJPS..46..569O    Altcode: 1968ICRC...10..569O; 1968CaJPh..46S.569O; 1968CaJPh..46..569O
  No abstract at ADS

---------------------------------------------------------
Title: The composition of galactic cosmic rays
Authors: Reames, D. V.; Fichtel, C. E.
1968CaJPS..46..544R    Altcode: 1968ICRC...10..544R; 1968CaJPh..46S.544R; 1968CaJPh..46..544R
  No abstract at ADS

---------------------------------------------------------
Title: Composition of the September 2, 1966 solar particle event
Authors: Durgaprasad, N.; Fichtel, C. E.; Guss, D. E.; Reames, D. V.
1968CaJPS..46..749D    Altcode: 1968ICRC...10..749D; 1968CaJPh..46S.749D
  No abstract at ADS

---------------------------------------------------------
Title: Nuclear Cross Sections Required in Studies of Cosmic Rays
Authors: Reames, D. V.
1967henr.book..273R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Source Spectra and Composition of Cosmic Rays Implied by an
    Analysis of Interstellar and Interplanetary Travel
Authors: Fichtel, C. E.; Reames, D. V.
1966PhRv..149..995F    Altcode:
  The implications of a simple set of assumptions related to galactic
  cosmic rays are examined and compared with the existing data. These
  assumptions are that (a) the multiply charged cosmic-ray nuclei
  all have the same spectral shape at the source, (b) the relative
  abundances of He<SUP>3</SUP> and light nuclei (3&lt;=Z&lt;=5) are
  negligible at the source, and (c) the average amount of interstellar
  material traversed is independent of particle energy. The results show
  that within the present uncertainties of the experimental data and of
  the interaction cross sections, the data agree with the predictions
  without additional assumptions if the differential source spectra are
  relatively flat at low energies and the average interstellar path is
  2.8+/-0.4 g/cm<SUP>2</SUP>. In particular, the nearly constant relative
  abundances of the helium, medium (6&lt;=Z&lt;=9), and (Z&gt;=10)
  nuclei for different values of energy/nucleon can be explained, and
  the observed variation of the flux ratio of light to medium nuclei with
  energy/nucleon can be brought into fair agreement with predictions. The
  calculations also imply that, if the analysis does represent the true
  situation, then there is little or no solar modulation of the cosmic
  rays near solar minimum, and protons and helium nuclei have different
  source spectra.

---------------------------------------------------------
Title: Very Low Energy Cosmic Bay Heavy Nuclei
Authors: Fichtel, C. E.; Guss, D. E.; Neelakantan, K. A.; Reames, D. V.
1966crep.conf..121F    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: An experimental examination of low energy cosmic ray heavy
    nuclei
Authors: Fichtel, C. E.; Guss, D. E.; Neelakantan, K. A.; Reames, D. V.
1965ICRC....1..400F    Altcode: 1965ICRC....9..400F
  No abstract at ADS