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Title: Solar wind suprathermal electron Stahl widths across high-speed stream structures

Abstract

Suprathermal electrons (100-1500 eV) observed in the solar wind typically show a strahl distribution, that is, a beam directed away from the Sun along the magnetic field direction. The strahl width observed at 1 AU is highly variable, ranging from 10-70 degrees. The obsenred finite width of the strahl results from the competition between beam focusing as the interplanetary magnetic field strength drops with distance from the Sun, and pitch-angle scattering as the beam interacts with the solar wind plasma in transit from the sun. Here we examine strahl width, observed with ACE SWEPAM across high-speed stream structures to investigate variations in electron scattering as a function of local plasma characteristics. We find that narrow strahls (less than 20 degrees wide), indicating reduced scattering, are observed within high-speed streams. Narrow strahls are also observed in both very low temperature solar wind, in association with ICMEs. Case studies of high-speed streams typically show the strahl narrowing at the leading edge of the stream. In some cases, the strahl narrows at the reverse shock or pressure wave, in other cases at the stream interface. The narrowing can either occur discontinuously or gradually over a period of hours. Within the high-speed wind, themore » strahl remains narrow for a period of hours to days, and then gradually broadens. The strahl width is roughly constant at all energies across these structures. For some fraction of high-speed streams, counterstreaming is associated with passage of the corotating interaction region. In these cases, we find the widths of the two counterstreaming beams frequently differ by more than 40 degrees. This dramatic difference in strahl width contrasts with observations in the solar wind as a whole, in which counterstreaming strahls typically differ in width by less than 20 degrees.« less

Authors:
 [1];  [1];  [1];  [2]
  1. Los Alamos National Laboratory
  2. DARTMUTH UNIV.
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1045405
Report Number(s):
LA-UR-11-00017; LA-UR-11-17
TRN: US201215%%17
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Conference
Resource Relation:
Conference: Fall 2009 AGU Meeting ; December 15, 2010 ; San Francisco, CA
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DISTRIBUTION; ELECTRONS; FOCUSING; INCLINATION; INTERPLANETARY MAGNETIC FIELDS; MAGNETIC FIELDS; PLASMA; SCATTERING; SOLAR WIND; SUN

Citation Formats

Skoug, Ruth M, Steinberg, John T, Goodrich, Katherine A, and Anderson, Brett R. Solar wind suprathermal electron Stahl widths across high-speed stream structures. United States: N. p., 2011. Web.
Skoug, Ruth M, Steinberg, John T, Goodrich, Katherine A, & Anderson, Brett R. Solar wind suprathermal electron Stahl widths across high-speed stream structures. United States.
Skoug, Ruth M, Steinberg, John T, Goodrich, Katherine A, and Anderson, Brett R. Mon . "Solar wind suprathermal electron Stahl widths across high-speed stream structures". United States. https://www.osti.gov/servlets/purl/1045405.
@article{osti_1045405,
title = {Solar wind suprathermal electron Stahl widths across high-speed stream structures},
author = {Skoug, Ruth M and Steinberg, John T and Goodrich, Katherine A and Anderson, Brett R},
abstractNote = {Suprathermal electrons (100-1500 eV) observed in the solar wind typically show a strahl distribution, that is, a beam directed away from the Sun along the magnetic field direction. The strahl width observed at 1 AU is highly variable, ranging from 10-70 degrees. The obsenred finite width of the strahl results from the competition between beam focusing as the interplanetary magnetic field strength drops with distance from the Sun, and pitch-angle scattering as the beam interacts with the solar wind plasma in transit from the sun. Here we examine strahl width, observed with ACE SWEPAM across high-speed stream structures to investigate variations in electron scattering as a function of local plasma characteristics. We find that narrow strahls (less than 20 degrees wide), indicating reduced scattering, are observed within high-speed streams. Narrow strahls are also observed in both very low temperature solar wind, in association with ICMEs. Case studies of high-speed streams typically show the strahl narrowing at the leading edge of the stream. In some cases, the strahl narrows at the reverse shock or pressure wave, in other cases at the stream interface. The narrowing can either occur discontinuously or gradually over a period of hours. Within the high-speed wind, the strahl remains narrow for a period of hours to days, and then gradually broadens. The strahl width is roughly constant at all energies across these structures. For some fraction of high-speed streams, counterstreaming is associated with passage of the corotating interaction region. In these cases, we find the widths of the two counterstreaming beams frequently differ by more than 40 degrees. This dramatic difference in strahl width contrasts with observations in the solar wind as a whole, in which counterstreaming strahls typically differ in width by less than 20 degrees.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {1}
}

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