20 Years of ACE Data: How Superposed Epoch Analyses Reveal Generic Features in Interplanetary CME Profiles

JANVIER, M.; STRUGAREK, A.; REGNAULT, F.; AUCHÈRE, F.; NOÛS, C.; DÉMOULIN, P.; DASSO, S.

Journal of Geophysical Research: Space Physics

AGU

Año: 2020 vol. 125

2169-9380

Interplanetary coronal mass ejections (ICMEs) are magnetic structures propagating from the Sun?s corona to the interplanetary medium. With over 20 years of observations at the L1 libration point, ACE offers hundreds of ICMEs detected at different times during several solar cycles, and with different features such as the propagation speed. We investigate a revisited catalog of more than 400 ICMEs using the superposed epoch method on the mean, median and the most probable values of the distribution of magnetic and plasma parameters. We also investigate the effects of the speed of ICMEs relative to the solar wind, the solar cycle, and the existence of a magnetic cloud on the generic ICME profile. We find that fast-propagating ICMEs (relatively to the solar wind in front)34 still show signs of compression at 1 au, as seen by the compressed sheath and the asymmetric profile of the magnetic field. While the solar cycle evolution doesn?t impact the generic features of ICMEs, there are more extreme events during the active part of the37 cycle, widening the distributions of all parameters. Finally, we find that ICMEs with or without a detected magnetic cloud show similar profiles, which confirms the hypothe39sis that ICMEs with no detected magnetic clouds are crossed further away from the flux rope core. Such a study provides a generic understanding of processes that shape the over all features of ICMEs in the solar wind, and can be extended with future missions at different locations in the solar system.