Lf. Burlaga et Nf. Ness, GLOBAL PATTERNS OF HELIOSPHERIC MAGNETIC-FIELD POLARITIES AND ELEVATION ANGLES - 1990 THROUGH 1995, J GEO R-S P, 102(A9), 1997, pp. 19731-19742
From 1990 through 1995, Voyager 1 (V1) moved from 39.9 to 61.7 AU in t
he distant heliosphere at a latitude of approximate to 32 +/- 1 degree
s N. During this period of declining solar activity, the latitudinal e
xtent of the sector zone (the region containing sectors and the helios
pheric current sheet) was decreasing. From 1990 through 1992, V1 obser
ved both positive and negative magnetic polarities, indicating that it
was ja the sector zone. From 1993 through 1995, V1 observed primarily
positive magnetic polarities, indicating that it was above the sector
zone. The transition in the V1 polarity distribution at the beginning
of 1993 implies that the maximum latitudinal extent of the sector zon
e was then approximate to 32 degrees N; This transition is related to
a decrease in the maximum latitudinal extent of the computed neutral l
ine in the solar corona. The ''classic model'' of the neutral line pro
vides a better description of the V1 polarities than the ''radial mode
l.'' The latitudinal extent of the sector zone was nearly constant fro
m the Sun to 50 AU; A similar transition in the polarity distribution
was observed at approximate to 30 degrees S by Ulysses in early 1993 w
ithin 5 AU, establishing the minimum latitudinal extent of the sector
zone at that time. From 1990 through 1995, hear-Earth spacecraft (whic
h were near the solar equatorial plane, in the middle of the sector zo
ne) observed equal amounts of positive and negative polarities. The bi
modal two-polarity distributions observed by Voyager 2 Showed an incre
asing fraction bf negative polarities as it moved from 2.4 degrees N t
o 15.1 degrees S and from 31.1 to 47.7 AU. The distribution of elevati
on angles was gaussian both at V1 in the distant heliosphere and near
1 AU during the each of the years from 1990 through 1995. The width of
the distribution did not change significantly at V1 from 1986 through
1995, consistent with little (<5 degrees) or no variation with (1) ra
dial distance from 40 to 62 AU, (2) latitude from 31 degrees to 33 deg
rees, and (3) the solar cycle. The width of the distribution of elevat
ion angles at 1 AU did vary with Solar activity, being 5 degrees great
er at solar maximum than at solar minimum, possibly owing to the extre
me north-south fields in many ejecta, which are more frequent near sol
ar maximum.