Temperatures and Temperature Anisotropies of Heavy Solar Wind Ions From Ulysses-SWICS

Details Temperatures and Temperature Anisotropies of Heavy Solar Wind Ions From Ulysses-SWICS Temperatures and Temperature Anisotropies of Heavy Solar Wind Ions From Ulysses-SWICS

Dec 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsh21a0732v&link_type=abstract

American Geophysical Union, Fall Meeting 2001, abstract #SH21A-0732

Physics

2100 Interplanetary Physics, 2149 Mhd Waves And Turbulence, 2164 Solar Wind Plasma, 7807 Charged Particle Motion And Acceleration, 7867 Wave/Particle Interactions

Scientific paper

The kinetic properties of heavy ions in the solar wind are indicative of processes affecting their distribution functions in interplanetary space. Observations at 1 AU reported earlier have established that all heavy ion species flow approximately at the same bulk speed and have approximately equal thermal speeds (i.e., mass-proportional temperatures), with exceptions at times when the solar wind density was unusually high. At 5 AU such exceptions no longer occur and the basic picture (of equal bulk speeds and thermal speeds) applies with very high accuracy. This was interpreted as evidence for the growing dominance of wave-particle interactions over Coulomb collisions with increasing heliocentric distance. Moreover, ubiquitous supra-thermal tails on the distribution functions of heavy ions (without any association to shocks) were interpreted as evidence for wave-particle interactions referentially heating and accelerating heavy ions from thermal energies to energies where they become amenable to shock acceleration, at about 2--3 v SW. In this work we examine yet another property of heavy ion distribution functions: their thermal anisotropy. This is not a straightforward matter since with SWICS only 1-dimensional cuts through the full, 3-d velocity distribution functions are measured. We therefore have to resort to a statistical approach, separating the particle data according to the instantaneous magnetic field pitch angle (and restricting ourselves to periods when this angle remains sufficiently constant over an instrument cycle of 13 minutes). We apply this analysis to the ions of He++ and O6+ during extended time periods in both the fast streams from the south and the north polar coronal holes observed by Ulysses in 1993--96. The results of this study are interpreted in relation to the observations made on Helios for He2+ in the 1970s, and to recent observations made on SOHO-UVCS, which show extreme temperature anisotropies of O vi, or O5+, at a few solar radii.

Affiliated with

Also associated with

No associations

Rating

Temperatures and Temperature Anisotropies of Heavy Solar Wind Ions From Ulysses-SWICS does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Temperatures and Temperature Anisotropies of Heavy Solar Wind Ions From Ulysses-SWICS, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperatures and Temperature Anisotropies of Heavy Solar Wind Ions From Ulysses-SWICS will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1381067