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Title: QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1–1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ∼0.1–1.5 keV to a Kappa distribution function with an index κ and effective temperature T{sub eff}. We also calculate the number density n and average energy E{sub avg} of strahl and halo electrons by integrating the electron measurements between ∼0.1 and 1.5 keV. We find a strong positive correlation between κ and T{sub eff} for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but themore » halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity)« less
Authors:
; ; ; ;  [1] ;  [2] ; ;  [3] ;  [4]
  1. School of Earth and Space Science, Peking University, Beijing 100871 (China)
  2. Department of Physics and CSPAR, University of Alabama in Huntsville, Alabama 35899 (United States)
  3. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
  4. Institute for Experimental and Applied Physics, University of Kiel, Leibnizstrasse 11, D-24118 Kiel (Germany)
Publication Date:
OSTI Identifier:
22518583
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 820; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; ANGULAR DISTRIBUTION; CORRELATIONS; DENSITY; DISTRIBUTION FUNCTIONS; EMISSION; ENERGY SPECTRA; KEV RANGE; SOLAR CYCLE; SOLAR ELECTRONS; SOLAR WIND; SUN; VELOCITY