An extended analysis of the September 1989 cosmic ray ground level enhancement

Abstract

Abstract. The September 29, 1989, cosmic ray ground level enhancement had a complex intensity-time profile with two distinct peaks observed at some neutron monitors. The event was detected by surface and some underground muon telescopes indicating the presence of particles up to •30 GV. We have modeled the response of neutron monitors and surface muon telescopes at the times of both intensity peaks and during the decay phase. We have determined particle rigidity spectra and pitch angle distributions centered on apparent arrival directions. Some evidence of bidirectional flow is present during the second peak. This may be due to backscattering of particles from beyond Earth. There was a high degree of scattering from all directions resulting in a significant isotropic component. Spectra derived from ground level responses are consistent with satellite observations. The specmma between a few MeV and a few tens of GeV is consistent with shock acceleration.

Shock as a black box: 2. Effects of adiabatic deceleration and convection included

“…In addition, for a wide dynamic range from about 50 keV to about 500 MeV, the injection spectrum will be not one smooth power law, but most likely a power In addition, at energies of a few hundred MeV the spectrum steepens a second time [e.g., Belov and Eroshenko, 1996;Lovell et al, 1998]. Attempts to fit particle events with this model thus should start with fitting the higher energies with the simpler KW97 model.…”

Solar Energetic Particles and Space Weather: Science and Applications

“…Such hybrid events may result from the re-acceleration of remnant flare suprathermals by shock waves (Mason et al 1999;Desai et al 2006) or from the interaction of CMEs (Gopalswamy et al 2002). It is noteworthy however, that based on large enhancements in the Fe/O during the initial phases of two large SEP events observed by Wind and Ulysses when the two spacecraft (s/c) were separated by 60 ı in longitude (Tylka et al 2013) argued that the initial Fe/O enhancements cannot be cited as evidence for a direct flare component, but instead Tylka et al 2000) and September 1989 (blue, Lovell et al 1998) are compared. In yellow the hazardous portion of the spectrum during the April 1998 event is highlighted.…”

Australian Cosmic Ray Modulation Research

“…The steepening of the spectra is similar to the Ellison & Ramaty (1985) form, and is consistent with shock acceleration rather than an impulsive injection of particles. Lovell et al (1998) extended the spectral analysis by including low-energy hourly average measurements from the IMP 8, GOES 6 and GOES 7 spacecraft. They fitted an Ellison & Ramaty (1985) shock acceleration spectrum to the increased energy range (now four orders of magnitude).…”

“…The underground muon increase was recorded with the Embudo telescope, which had a threshold of ∼15 GV, but was not recorded at the nearby Socorro telescope that was slightly deeper underground and had a threshold of ∼30 GV. Lovell, Duldig & Humble (1998) have published an extensive analysis of this GLE, including the responses of satellite instruments, neutron monitors and surface muon telescopes. In this analysis the muon telescope response was determined for nine directions in a manner similar to that used for the neutron monitors.…”

“…The derived attenuation length for solar particles was 120 g cm −2 . Lovell et al (1998) analysed three 5-min time intervals commencing at 1215 UT, 1325 UT and 1600 UT. These times were chosen because they were the times of the first and second peaks and late in the event during the recovery phase.…”