Jl. Cramp et al., THE EFFECT OF A DISTORTED INTERPLANETARY MAGNETIC-FIELD CONFIGURATIONON THE DECEMBER 7-8, 1982, GROUND-LEVEL ENHANCEMENT, J GEO R-S P, 102(A3), 1997, pp. 4919-4925
The cosmic ray ground level enhancement (GLE) of December 7-8, 1982, o
ccurred when the interplanetary magnetic field (IMF) direction measure
d near Earth indicated significant distortion from the nominal form. W
e have modeled the ground level response to this event to derive rigid
ity spectra and pitch angle distributions centered on apparent arrival
directions. A deficit region associated with a near-Earth magnetic cl
oud-like structure has been modeled during the initial phase of the GL
E. Using this modified model, we find agreement between the derived pa
rticle arrival directions and the measured IMF directions. We find a s
ignificant contribution from pitch angles greater than 90 degrees thro
ughout the event. This is probably due to scattering in the turbulent
region behind the cloud-like structure.