STEP-F and SphinX particle and X-ray detector as sensitive actuators for radiation environment of near-Earth space

The state of geomagnetic environment as observed at the ground level is characterized by numerous indices, derived from measurements from numerous magnetic observatories scattered over many longitudes and latitudes. In support, patrol measurements of geomagnetic field components are carried out in near-Earth space using onboard magnetometers that constantly cross geomagnetic field thanks to the orbital motion of the spacecraft. In the same way, high-energy charged particle fluxes trapped by the Earth's magnetic field are monitored along the satellite orbit. In the geomagnetic radiation belts’ environment, the distribution of proton fluxes is mostly less variable, while electron fluxes experience strong variations associated even with weak fluctuations of well-known indices: mid-latitude K_p, and equatorial D_st (related to weak geomagnetic storms). During very strong geomagnetic storms an additional electron radiation belt appears in a slot between outer and inner Van Allen belts. However, even during the period of minimum solar activity when small variations of the geomagnetic field prevail, noticeable changes in electron fluxes are being recorded, including recently discovered presence of additional electron radiation belt at by L=1.6 McIllwain surface.

In present research, we used data collected by the two instruments placed next to each other aboard the low Earth (h ≈ 550 km) near polar (φ ≈ 82.5⁰) orbit CORONAS-Photon satellite. We studied responses of the Satellite Telescope of Electrons and Protons (STEP-F) and the Solar photometer in X-rays (SphinX) in May 2009, a period which was characterized by a very weak solar and geomagnetic activity. As geomagnetic indicators we used K_p, D_st-, and SYM-H indices. For SphinX measurements, we extracted 5-second data in the highest energy bin sensitive to detection of charged particles. For STEP-F we analysed 2-second data records in the upper silicon position-sensitive detector while the satellite crossed all three electron radiation belts present in the magnetosphere. We demonstrate variable, belt-dependent high amplitude responses due to energetic electron presence in all three belts as well as specific time-dependent features due to presence of directed particle streams. Examples will be provided and discussed.