Observations of effects from magnetospheric cusp movement during a solar proton event

• Main Authors: Brown, R. R., Barcus, J. R., Stauning, P., Karas, R. H.
• Format: Other/Unknown Material
• Language: unknown
• Published: 1981
• Subjects: 46; Greenland; Sondre Stromfjord
• Online Access: http://ntrs.nasa.gov/search.jsp?R=19810065282

Observations of a magnetospheric cusp motion event during a solar proton event are presented. The observations were made by a series of riometers and balloon-borne radiation detectors and conductivity probes near Sondre Stromfjord, Greenland. During the arrival of solar protons on August 19, 1979, the balloon-borne detectors recorded two rises and declines in nuclear gamma ray intensity accompanied by a marked softening in the photon spectrum. The observations are interpreted as a shift in detector position from the dayside of the magnetosphere to the polar cap resulting from an equatorward displacement or expansion of the polar cusp by 5 deg in 15 min with a southward turning of the IMF. Instruments on ISEE 3 confirm this interpretation, showing a southward turning of the IMF and a solar wind speed increase. Results imply a proton cutoff energy in the range 6-10 MeV at Sondre Strombjord prior to the cusp motion, and reflect the early effects of field line erosion.