Evolution of ICME sheath and leading-edge structure in the inner heliosphere
Abstract
We investigate a data sample of 40 interplanetary CME (ICME) events from Helios 1 and 2 data that cover the distance range 0.3-1au. For comparison, we add a sample of 5 ICMEs observed with Parker Solar Probe during 2018-2021. From the solar wind plasma and magnetic field measurements, we extract the ICME sub-structures sheath, leading-edge, and magnetic ejecta. We analyze their characteristic parameters as function of distance and present the main findings of this study: a) the average starting distance for actual sheath formation appears to be located at a distance of about 13 Rs; b) the sheath density becomes dominant over the magnetic ejecta density beyond 38 Rs; c) the sheath size could be related to the ambient solar wind density and magnetic ejecta characteristics; d) a local linear relation between sheath density and ambient solar wind speed was found; e) the leading-edge does not increase in size over distance and might be an isolated structure wedged in between sheath and magnetic ejecta. With Parker Solar Probe approaching the Sun as close as 10Rs, we will certainly detect more CME events to obtain measurements that might re-affirm the presented results. The current findings can be applied to help improve CME propagation models.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1439T