Abundances of Heavy and Ultraheavy Ions in 3He-rich Solar Flares

We have surveyed 3He-rich solar energetic particle (SEP) events over the period 1997 September-2003 April in order to characterize abundances of heavy ions near 400 keV nucleon-1. The first part of the study focuses on 20 distinct SEP events that show the previously observed pattern in which, relative to O, heavy ions through Fe are enriched, with the enrichment increasing with mass. We find that these enrichments are well correlated such that 3He-rich SEP events with high Fe/C also show larger enrichments in other heavy ions. Ultraheavy (UH; taken as 78-220 amu) ions are routinely seen in these events with abundance enhancements correlating with Fe/C but with even larger flare-to-flare variations. In one event with unusually little interplanetary scattering, we are able to estimate the time of heavy- and UH-ion injections at the Sun and find them to be simultaneous. The second part of the study sums up many impulsive-event time periods in order to construct a mass histogram of UH nuclei; this histogram shows broad mass peaks similar to those in compilations of solar system abundances. In this summed period, relative to O, the average enhancement of heavy nuclei increases with mass with values of ~7 for Fe, ~40 for mass 78-100 amu, ~120 for mass 125-150 amu, and ~215 for 180-220 amu. The maximum UH enhancements seen in the most-enriched events are at least a factor of 5 larger. The enhancements are approximately proportional to the particle charge-to-mass ratio raised to a power, as seen previously in large, shock-associated SEP events.

[1]  S. M. Krimigis,et al.  Evidence for a Suprathermal Seed Population of Heavy Ions Accelerated by Interplanetary Shocks near 1 AU , 2003 .

[2]  J. Giacalone,et al.  Particle Acceleration in Solar Wind Compression Regions , 2002 .

[3]  S. M. Krimigis,et al.  Spectral Properties of He and Heavy Ions in 3He-rich Solar Flares , 2002 .

[4]  J. Dwyer,et al.  A New Heavy Ion Abundance Enrichment Pattern in 3He-rich Solar Particle Events , 2002 .

[5]  S. M. Krimigis,et al.  Isotopic Composition of Solar Energetic Particle Events Measured by Advanced Composition Explorer/ULEIS , 2001 .

[6]  N. Sheeley,et al.  Coronal Mass Ejections Associated with Impulsive Solar Energetic Particle Events , 2001 .

[7]  J. Dwyer,et al.  New Properties of 3He-rich Solar Flares Deduced from Low-Energy Particle Spectra , 2000 .

[8]  D. Reames.  Abundances of Trans-Iron Elements in Solar Energetic Particle Events , 2000 .

[9]  Mazur,et al.  Interplanetary Magnetic Field Line Mixing Deduced from Impulsive Solar Flare Particles , 2000, The Astrophysical journal.

[10]  Mazur,et al.  3He Enhancements in Large Solar Energetic Particle Events , 1999, The Astrophysical journal.

[11]  U. Feldman,et al.  Morphology of the Quiet Solar Upper Atmosphere in the 4 × 104 < Te < 1.4 × 106 K Temperature Regime , 1999 .

[12]  R. Mewaldt,et al.  Event‐to‐event variations in the isotopic composition of neon in solar energetic particle events , 1999 .

[13]  T. X. Zhang.  Solar 3He-rich Events and Electron Acceleration in Two Stages , 1999 .

[14]  R. Mewaldt,et al.  Inferred charge states of high energy solar particles from the solar isotope spectrometer on ACE , 1999 .

[15]  J. Geiss,et al.  Unusual composition of the solar wind in the 2–3 May 1998 CME observed with SWICS on ACE , 1999 .

[16]  D. Ellison,et al.  Galactic Cosmic Rays from Supernova Remnants. II. Shock Acceleration of Gas and Dust , 1997, astro-ph/9704293.

[17]  J. Steinacker,et al.  The Helium Valley: Comparison of Impulsive Solar Flare Ion Abundances and Gyroresonant Acceleration with Oblique Turbulence in a Hot Multi-Ion Plasma , 1997 .

[18]  J. Mazur,et al.  Charge State Measurements of Solar Energetic Particles Observed with SAMPEX , 1995 .

[19]  T. X. Zhang.  Solar 3He-rich Events and Ion Acceleration in Two Stages , 1995 .

[20]  D. Reames.  Coronal abundances determined from energetic particles , 1995 .

[21]  D. Ellison,et al.  The Influence of Particle Scattering on Acceleration Rates and Injection Efficiencies in Oblique Shocks , 1995, astro-ph/9506076.

[22]  J. Meyer,et al.  Energetic-particle abundances in impulsive solar flare events , 1994 .

[23]  M. Arnaud,et al.  Iron ionization and recombination rates and ionization equilibrium , 1992 .

[24]  M. Temerin,et al.  The production of He-3 and heavy ion enrichment in He-3-rich flares by electromagnetic hydrogen cyclotron waves , 1992 .

[25]  E. Stone,et al.  Isotope abundances of solar coronal material derived from solar energetic particle measurements , 1989 .

[26]  D. Ellison,et al.  Diffusive shock acceleration - comparison of a unified shock model to bow shock observations , 1987 .

[27]  Berndt Klecker,et al.  The mean ionic charge of silicon in 3HE-rich solar flares , 1987 .

[28]  B. Klecker,et al.  The heavy-ion compositional signature in He-3-rich solar particle events , 1986 .

[29]  H. Breneman,et al.  SOLAR CORONAL AND PHOTOSPHERIC ABUNDANCES FROM SOLAR ENERGETIC PARTICLE MEASUREMENTS , 1985 .

[30]  J. Geiss,et al.  Interpretation of3He abundance variations in the solar wind , 1984 .

[31]  B. Klecker,et al.  Direct determination of the ionic charge distribution of helium and iron in He-3-rich solar energetic particle events , 1984 .

[32]  Martin A. Lee.  Coupled hydromagnetic wave excitation and ion acceleration upstream of the earth's bow shock , 1982 .

[33]  D. Eichler,et al.  Cosmic ray drift, shock wave acceleration and the anomalous component of cosmic rays , 1981 .

[34]  D. Eichler.  Energetic particle spectra in finite shocks: the earth's bow shock , 1981 .

[35]  L. Fisk.  He-3-rich flares - A possible explanation , 1978 .

[36]  D. Eichler.  Particle acceleration in collisionless shocks: regulated injection and high efficiency. , 1978 .

[37]  Douglass E. Post,et al.  Steady-state radiative cooling rates for low-density, high-temperature plasmas , 1977 .

[38]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[39]  D. Ellison.  Shock acceleration of diffuse ions at the Earth's bow shock: Acceleration efficiency and A/Z enhancement , 1985 .