Space weather effects on the MAGION-4 and MAGION-5 solar cells

Abstract. Data on solar array efficiency measured on board two Czech MAGION micro-satellites between August 1995 and June 2002, during the period of increasing and high solar activity, were used to study the space weather effects on photo-voltaic solar cells. A stronger degradation of the solar array was observed on MAGION-5 in comparison with MAGION-4. This fact can be explained by the essential difference between the two orbits. The MAGION-5 s/c was in the radiation belts more than 40% of the time, whereas the MAGION-4 was only present about 4% of the time. The experimental data refer to periods of low as well as high solar activity, with an enhanced occurrence of strong solar events. The evaluation of the data set covering a period of more than 6 years has shown that solar proton flares can have an almost immediate effect on the solar array efficiency. However, in the case of MAGION-5, an important role in solar cell degradation is played by the long-term effect of energetic particles in the radiation belts. Periods with a distinctly steeper decrease in the solar array output power were observed and can be explained by an increase of particle flux density in the radiation belts. Periods in slower decline of the solar array output power correspond to periods in low radiation belt indices based on the NOAA POES s/c data.