Generation and Validation of Ion Energy Spectra Based on Cluster RAPID and CIS Measurements

Abstract

We present a method to combine spectral information from the Cluster RAPID (Research with Adaptive Particle Imaging) and CIS (Cluster Ion Spectroscopy) instruments. Preliminary results from the magnetotail show that the kappa distribution can fit the ion distributions in the magnetotail, for example in thin plasma sheets during quiet and disturbed times with kappa factors ≃ 4.4 and ≃ 10, respectively. With the most recent RAPID and CIS/CODIF calibration files the average ratio of CIS fluxes (approximated using the kappa-fit to the effective energy of the first RAPID energy channel) to the RAPID fluxes at the first energy channel is about 0.74 ± 0.24. This result is perfectly acceptable for these two experiments, based on two very different measurement principles, therefore no further spectral shift or recalibrations are needed.