Accession Number:

ADA277552

Title:

The Ground-Level Enhancements of 29 September and 22 October 1989

Descriptive Note:

Corporate Author:

PHILLIPS LAB HANSCOM AFB MA

Report Date:

1993-01-01

Pagination or Media Count:

9.0

Abstract:

During the solar maximum of 1989-91 an unprecedented sequence of 13 cosmic ray ground-level enhancements GLEs was observed by the world-wide neutron monitor network. Of particular interest were two GLEs observed by the Australian network. The 1989 September 29 event was the largest GLE in the space era while the October 22 GLE included an highly anisotropic precursor peak. Analysis of both these GLES. taking into account disturbed geomagnetic conditions, shows that the particle arrivals at the earth were unusual. The September 29 GLE had significant particle propagation in the reverse direction and as the particle flux decreased following the peak the spectrum also softened. In contract, the 1989 October 22 precursor exhibited extreme anisotropy while the particles involved in the main GLE showed a complex temporal structure possibly indicating multiple particle injection at the solar acceleration region. Solar protons, Ground level events, Solar-terrestrial phenomena, Cosmic rays, Asymptotic directions, Geomagnetic field, Magnetosphere.

Subject Categories:

  • Astrophysics
  • Geomagnetism
  • Nuclear Physics and Elementary Particle Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE