Radiation-belt and transient solar-magnetospheric effects on Hipparcos radiation background

Abstract

The Hipparcos astrometry satellite operated in a near-geostationary transfer orbit between August 1989 and August 1993. Its telescopes were sensitive to background signals induced by energetic electrons and protons, and by bremsstrahlung. The observations yielded a long-term data-set which strongly reflects the structure of the radiation belts, their dynamics and the effects of solar particle events. Investigation of these data includes qualitative comparisons with GOES and CRRES data.

Super storms

“…Since the start of the space program in the 1960s, measurements within the magnetosphere have revealed the profound influence of extremely large magnetic storms on space plasma and particle populations. Two of the most documented storms occurred in August 1972 (see Spjeldvik and Fritz [1981a] for a list of references) and March 1991 [Blake et al, 1992b;Daly et al, 1992;Fredrickson et al, 1992;Gussenhoven et al, 1992;Mullen et al, 1991;Mullen and Gussenhoven, 1994; Ray, 1994; Shea et al, 1992;•iolet and Fredrickson, 1992]. These major magnetic storms, which we call super storms, are of great interest to the scientific community for two main reasons: (1) they drive the magnetosphere to an extreme state where dynamic processes, obscure under lesser conditions, can be clearly identified and studied; and (2) they create extremely enhanced electromagnetic fields and particle environments that behave differently than predicted by conventional theory.…”

<i>Editorial</i>The science of space weather

“…In Europe this has recently been addressed as part of two ESA studies of a European space weather pro- (Daly et al, 1994). Due to launch problems, Hipparcos ended up on a elliptical orbit through the radiation belts.…”