Properties of the Sheath Regions of Coronal Mass Ejections with or without Shocks from STEREO in situ Observations near 1 AU. (arXiv:2011.06632v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Salman_T/0/1/0/all/0/1">T. M. Salman</a>, <a href="http://arxiv.org/find/physics/1/au:+Lugaz_N/0/1/0/all/0/1">N. Lugaz</a>, <a href="http://arxiv.org/find/physics/1/au:+Farrugia_C/0/1/0/all/0/1">C. J. Farrugia</a>, <a href="http://arxiv.org/find/physics/1/au:+Winslow_R/0/1/0/all/0/1">R. M. Winslow</a>, <a href="http://arxiv.org/find/physics/1/au:+Jian_L/0/1/0/all/0/1">L. K. Jian</a>, <a href="http://arxiv.org/find/physics/1/au:+Galvin_A/0/1/0/all/0/1">A. B. Galvin</a>
We examine 188 coronal mass ejections (CMEs) measured by the twin STEREO
spacecraft during 2007-2016 to investigate the generic features of the CME
sheath and the magnetic ejecta (ME) and dependencies of average physical
parameters of the sheath on the ME. We classify the MEs into three categories,
focusing on whether a ME drives both a shock and sheath, or only a sheath, or
neither, near 1 AU. We also reevaluate our initial classification through an
automated algorithm and visual inspection. We observe that even for leading
edge speeds greater than 500 km/s, 1 out of 4 MEs do not drive shocks near 1
AU. MEs driving both shocks and sheaths are the fastest and propagate in high
magnetosonic solar wind, whereas MEs driving only sheaths are the slowest and
propagate in low magnetosonic solar wind. Our statistical and superposed epoch
analyses indicate that all physical parameters are more enhanced in the sheath
regions following shocks than in sheaths without shocks. However, differences
within sheaths become statistically less significant for similar driving MEs.
We also find that the radial thickness of ME-driven sheaths apparently has no
clear linear correlation with the speed profile and associated Mach numbers of
the driver.
We examine 188 coronal mass ejections (CMEs) measured by the twin STEREO
spacecraft during 2007-2016 to investigate the generic features of the CME
sheath and the magnetic ejecta (ME) and dependencies of average physical
parameters of the sheath on the ME. We classify the MEs into three categories,
focusing on whether a ME drives both a shock and sheath, or only a sheath, or
neither, near 1 AU. We also reevaluate our initial classification through an
automated algorithm and visual inspection. We observe that even for leading
edge speeds greater than 500 km/s, 1 out of 4 MEs do not drive shocks near 1
AU. MEs driving both shocks and sheaths are the fastest and propagate in high
magnetosonic solar wind, whereas MEs driving only sheaths are the slowest and
propagate in low magnetosonic solar wind. Our statistical and superposed epoch
analyses indicate that all physical parameters are more enhanced in the sheath
regions following shocks than in sheaths without shocks. However, differences
within sheaths become statistically less significant for similar driving MEs.
We also find that the radial thickness of ME-driven sheaths apparently has no
clear linear correlation with the speed profile and associated Mach numbers of
the driver.
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