Geomagnetic effects associated with relativistic flares

Abstract

Solar flare effects associated with the relativistic flares (flares during which very fast solar particles, mainly protons, of cosmic-ray energies were observed at ground level) are compared with those of non-relativistic flares. All flares accompanied by magnetic crochets in the horizontal force of the earth's field at Kodaikanal (lat. 10°. 2N; long. 77°. 5E; magnetic dip; 3°. 5N) during a six year period (1956 through 1961) have been classified into two types. The times of occurrence, amplitudes, durations and impulsive nature of the geomagnetic effects associated with the two types of flares are found to be different in nature. The plausible causes are discussed in terms of enhanced D-region ionization caused by strong hardening of X-ray burst of solar origin in the spectral range λλ 1–8 Å, associated with the high energy part of electron spectrum responsible for intense micro-wave bursts, during relativistic flares.