Abstract:
Several decades of remote and in-situ observations along with models, simulation, and kinetic studies, suggest that the cross-section of an ICME can vary from cylindrical, elliptical, toroidal, flattened, pancaked, etc. Here, we proposed a unique morphological characteristic of an ICME magnetic cloud 1 AU, where ICME MC transformed into a flattened quasi-2D structure named planar magnetic structure (PMS), using in-situ data from ACE spacecraft. We statistically shows that out of 469 ICME MCs from 1998 to 2017, 136 ( ∼29 ) ICME MCs shows PMS characteristic (named as planar MCs), whereas 333 ( ∼71 ) does not have PMS characteristic (non-planar MCs). Interestingly, the total IMF strength, the average plasma parameters, i.e., plasma density, beta, thermal pressure, and magnetic pressure in the planar MCs, are significantly higher than in non-planar MCs. Also, the thickness of planar MCs is less compared to non-planar MCs. These observations suggest that MCs can be transformed into planar-like structures due to the high compression from behind. We also observe the southward/northward magnetic field component's double strength during planar MCs compared to the non-planar MCs. It implies that planar MCs are more geo-effective than non-planar MCs. In addition to this, to explore does Planar ICME conversion happens close to the Sun or away from it? We analyzed several ICMEs using PSP data and found that ICMEs can be transformed into PMS-like configurations close to the Sun. A detailed study is needed to investigate the origin and effect of the planar sheath on the heliosphere and solar-terrestrial physics.
