Alfvén Ion Cyclotron Waves in Sheath Regions Driven by Interplanetary Coronal Mass Ejections

0510735 - ÚFA 2020 RIV US eng J - Journal Article
Ala-Lahti, M. - Kilpua, E. K. J. - Souček, Jan - Pulkkinen, T. I. - Dimmock, A.
Alfvén Ion Cyclotron Waves in Sheath Regions Driven by Interplanetary Coronal Mass Ejections.
Journal of Geophysical Research-Space Physics. Roč. 124, č. 6 (2019), s. 3893-3909. ISSN 2169-9380. E-ISSN 2169-9402
R&D Projects: GA ČR(CZ) GA17-08772S
Institutional support: RVO:68378289
Keywords : low-frequency waves * temperature anisotropy * Earths magnetosheath * mirror instability * magnetic clouds * flux-rope * origin * shocks * CMEs * fluctuations
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 2.799, year: 2019
Method of publishing: Open access
https://helda.helsinki.fi/bitstream/10138/305158/1/AICwaves_in_ICMEsheaths.pdf

We report on a statistical analysis of the occurrence and properties of Alfven ion cyclotron (AIC) waves in sheath regions driven by interplanetary coronal mass ejections (ICMEs). We have developed an automated algorithm to identify AIC wave events from magnetic field data and apply it to investigate 91 ICME sheath regions recorded by the Wind spacecraft. Our analysis focuses on waves generated by the ion cyclotron instability. AIC waves are observed to be frequent structures in ICME-driven sheaths, and their occurrence is the highest in the vicinity of the shock. Together with previous studies, our results imply that the shock compression has a crucial role in generating wave activity in ICME sheaths. AIC waves tend to have their frequency below the ion cyclotron frequency, and, in general, occur in plasma that is stable with respect to the ion cyclotron instability and has lower ion beta(parallel to) than mirror modes. The results suggest that the ion beta anisotropy beta(perpendicular to)/beta(parallel to) > 1 appearing in ICME sheaths is regulated by both ion cyclotron and mirror instabilities.
Permanent Link: http://hdl.handle.net/11104/0301147