Solar wind control of spacecraft charging conditions in geostationary orbit during magnetic storms

• Published in: Advances in space research 2000, Vol.26 (1), p.37-40
• Main Authors: Degtjarev, V.I., Popov, G.V., Johnstone, A.D.
• Format: Article
• Language: English
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/S0273-1177(99)01024-8

Investigations of spacecraft charging at geostationary orbit reveal close relations between magnetospheric disturbances and electrostatic fields on spacecraft. These links provide a basis for forecasting spacecraft charging and the risk of spacecraft anomalies. In order to improve such forecasts the links between solar wind parameters, radiation conditions at geostationary orbit, and spacecraft charging have been studied. To reveal the relationships between the solar wind and the geostationary radiation environment, 37 magnetic storms between July 1976 and December 1978 were chosen for analysis. Data on electron fluxes in the energy range from 30 keV to 1360 keV from LANL geostationary spacecraft were also used. The analysis methods included moving averages, superposed epoch and correlation. It was found that the smoothed electron fluxes at geostationary orbit are controlled primarily by the solar wind velocity. The time delay between bursts of energetic electron fluxes and solar wind velocity disturbance depends on electron energy and may be up to tens of hours. This time lag makes it possible to separate surface and bulk charging disturbances during magnetic storms. An example of such a separation is shown.