AN EXAMINATION OF DIRECTIONAL DISCONTINUITIES AND MAGNETIC POLARITY CHANGES AROUND INTERPLANETARY SECTOR BOUNDARIES USING E-GREATER-THAN-2 KEV ELECTRONS
Sw. Kahler et Rp. Lin, AN EXAMINATION OF DIRECTIONAL DISCONTINUITIES AND MAGNETIC POLARITY CHANGES AROUND INTERPLANETARY SECTOR BOUNDARIES USING E-GREATER-THAN-2 KEV ELECTRONS, Solar physics, 161(1), 1995, pp. 183-195
Past studies of interplanetary magnetic sector boundaries have been ba
sed on the assumption that one can determine the field polarities by c
omparing the field directions with those of the nominal Parker spiral
angles. Previous investigators have found evidence for decreases of \B
\, the magnitude of the magnetic field B, and increases of Theta, the
angle between B and the ecliptic plane, at sector boundaries. Others h
ave argued that the characteristic thickness of sector boundaries exce
eds that of tangential discontinuities, making sector boundaries a sep
arate class of structures. We use a simple technique for inferring the
polarities of interplanetary magnetic fields based on the assumption
that E > 2 keV electrons are always flowing along the magnetic field a
way from the Sun. Electron data from the UC Berkeley experiment on the
ISEE-3 spacecraft are used to examine periods around several apparent
sector boundaries in 1978 and 1979. We compare properties of (a) boun
daries with field polarity changes and (b) large-angle (omega > 60 deg
rees) directional discontinuities with no field polarity changes. We f
ind no significant differences between the sector boundaries and the d
irectional discontinuities in terms of associated decreases in \B\ or
of values of Theta. These results suggest no significant difference be
tween sector boundaries and directional discontinuities other than the
change in field polarities. Within limited statistics we find that ab
out half the polarity changes would not have been identified using a r
equirement that omega > 90 degrees and that half of the omega > 120 de
grees discontinuities would have been misidentified as polarity change
s.