HR: 16:30h
AN: SH34A-05    [Abstracts]
TI: Folds in the Interplanetary Magnetic Field in High Speed Streams Observed with Ulysses and ACE
AU: * Steinberg, J T
EM: jsteinberg@lanl.gov
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Skoug, R M
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AB: Large rotations observed in the IMF can be due to true field polarity reversals, i.e. crossings of the heliospheric current sheet. But very often they are instead encounters with fields that are locally folded back upon themselves. Within coronal hole-related high-speed streams, we have found that folds can be readily distinguished from true polarity reversals by using the property of differential streaming between alpha particles and protons. The vector difference between the alpha particle velocity and the proton velocity lies parallel (or anti-parallel) to the magnetic field, but always points in the field-aligned direction away from the sun. At times, folded fields have been discussed in terms of static structures that are simply carried along with the solar wind flow. However in high-speed stream events, every fold we have examined to date shows correlations between the field turnings and variations in the solar wind velocity vector, indicating the folds are more likely propagating Alfvenic features. We present a comprehensive survey of large field folds within Ulysses and ACE observations of high-speed streams. We report how the frequency and duration of folded fields varies with radial distance, as well as how they differ between flow from large polar coronal holes at solar minimum and smaller coronal holes found at all latitudes around solar max.
DE: 2134 Interplanetary magnetic fields
DE: 2149 MHD waves and turbulence
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly