GLOBAL PATTERNS OF HELIOSPHERIC MAGNETIC-FIELD POLARITIES AND ELEVATION ANGLES - 1990 THROUGH 1995

Citation
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
Citations number
40
Categorie Soggetti
Geosciences, Interdisciplinary","Astronomy & Astrophysics","Metereology & Atmospheric Sciences
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
ISSN journal
21699380 → ACNP
Volume
102
Issue
A9
Year of publication
1997
Pages
19731 - 19742
Database
ISI
SICI code
2169-9380(1997)102:A9<19731:GPOHMP>2.0.ZU;2-A
Abstract
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.