Turning Instrument Background Into Science Data for Structural Features of Radiation Belts

Approaches regarding how to turn the instrument background counts into scientifically valuable data are presented in this Technical Report on Methods. The background counts due to penetrating energetic particles of radiation belts detected on Cluster CIS HIA and CODIF instruments and the Double Star HIA instrument are used in these approaches. In HIA spectrograms, the background counts are seen simultaneously in all energy channels marking the entry and exit of the radiation belts by the spacecraft, therefore, the locations of the boundaries of the outer and inner belts can be determined. In the case when HIA measurements are not readily available, a new method is proposed in which supplementary data streams within the CODIF telemetry is exploited. It employs separate counts that register “start,” “stop,” and “non-valid” signals increasing in the presence of penetrating particles even when no corresponding increase are shown in the energy-time spectrograms. The locations of the radiation belt boundaries are defined by following the changes in counts gradients with time and visual inspection of all the available measurements. The July–August 2007 and September–October 2012 time periods are analyzed for method demonstration on a presence of a third radiation belt, or storage ring.