SPRG Seminars

November 9, 2010:

" Solar Wind and Foreshock Electrons"

Dr. Marc Pulupa, University of California, Berkeley, Space Sciences Laboratory

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I will present recent work on two projects, both dealing with solar wind electrons.

I: Wind/3DP Solar Wind Electron Database

Solar wind electrons display significant non-equilibrium characteristics which are relevant to several outstanding problems in heliophysics, including the generation of plasma instabilities, transport processes in a weakly collisional plasma, and the origins of the solar wind.  Observed electron distribution functions comprise several distinct populations, including the cold and dense core electrons, the hotter and more tenuous halo electrons, and the field-aligned strahl beam.  We have analyzed electron distribution functions from the Wind/3DP instrument, generating an accurate database of core, halo and strahl electron parameters.  We will discuss the analysis technique in some detail, and also briefly discuss the science topics which will soon be addressed using this database.

II: STEREO Observations of Foreshock Electrons

Solar wind electrons are accelerated and reflected back upstream by the terrestrial  bow shock into a region known as the electron foreshock. These foreshock electron beams create a bump on tail instability which generates intense electrostatic waves  known as Langmuir waves. In the early part of its mission, the SWEA and STE electron detectors on the STEREO spacecraft  observed many examples of electron beams in the terrestrial foreshock, accompanied  by bursts of intense Langmuir wave activity.  We have examined the electron acceleration mechanism by comparing in situ measurements of the reflected electrons with predictions based on a Liouville mapping of upstream spectra through a bow shock interaction.