Solar wind electron characteristics inside and outside coronal mass ejections

R. M. Skoug, W. C. Feldman, J. T. Gosling, D. J. McComas, C. W. Smith

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47 Scopus citations


We present a study of 9 months of data from the solar wind plasma electron instrument on the ACE spacecraft. Electron pitch angle distributions were used to identify intervals of counterstreaming halo electrons, which were observed ∼16% of the time that the spacecraft was not magnetically connected to the Earth's bow shock. Counterstreaming electrons presumably indicate a closed magnetic field topology and thus indicate the passage of coronal mass ejections (CMEs) in the solar wind. In this study, we separately examine electron moments at times with and without counterstreaming electrons, including both magnetic clouds and noncloud CMEs. The properties of both the core and halo electron populations were nearly identical at times with and without counterstreaming electrons. Both low and high electron densities and temperatures were observed in either type of event. In contrast, magnetic clouds, on average, showed increased densities and reduced temperatures. The core/halo density ratio and the total electron density were anticorrelated in all cases, indicating that the halo contributes more to the total electron density at low density times, regardless of magnetic topology. Total electron temperature and density were anticorrelated in all types of events. This consistent anticorrelation implies that such single-spacecraft measurements of temperature and density cannot be used to determine a polytropic index for solar wind electrons. Instead, the anticorrelation may be due to pressure balance of the solar wind plasma or may be a remnant of coronal conditions.

Original languageEnglish (US)
Article number2000JA000017
Pages (from-to)23069-23084
Number of pages16
JournalJournal of Geophysical Research: Space Physics
Issue numberA10
StatePublished - 2000
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography


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