Study of oblique whistler waves in coronal mass ejections observed by Solar Orbiter

Sammanfattning: In this paper a search routine in MATLAB was developed in order to find and analyze oblique whistler waves in the data from the ESA and NASA spacecraft Solar Orbiter. Oblique whistler waves are a type of plasma wave which propagate at an angle with respect to the background magnetic field. They are efficient at scattering electrons in the solar wind but their role in interplanetary coronal mass ejections (ICMEs) is yet unknown. Magnetic field data from 1-31st of June 2022, as well as the 24th and 27-28th of January 2022 was examined. The search routine found six whistler waves in June and 12 for the dates in January. Among these, all found whistler waves were found in the sheath region of the ICMEs, and all had a plasma beta > 1. However due to instrumental artefacts the values of θk were found to be smaller than detected by the search routine, indicating less obliqueness than first expected. Some of the whistler waves seemed to have an obliqueness that changed with time and the bandwidth of the waves varied among the identified.