Penetration of magnetosheath plasma into dayside magnetosphere: 2. Magnetic field in plasma filaments

Abstract

In this paper, we examined plasma structures (filaments), observed in the dayside magnetosphere but containing magnetosheath plasma. These filaments show the stable antisunward motion (while the ambient magnetospheric plasma moved in the opposite direction) and the existence of a strip of magnetospheric plasma, separating these filaments from the magnetosheath. These results, however, contradict both theoretical studies and simulations by Schindler (1979), Ma et al. (1991), Dai and Woodward (1994, 1998), and other researchers, who reported that the motion of such filaments through the magnetosphere is possible only when their magnetic field is directed very close to the ambient magnetic field, which is not the situation that is observed. In this study, we show that this seeming contradiction may be related to different events as the theoretical studies and simulations are related to the case when the filament magnetic field is about aligned with filament orientation, whereas the observations show that the magnetic field in these filaments may be rotating. In this case, the rotating magnetic field, changing incessantly its direction, drastically affects the penetration of plasma filaments into the magnetosphere. In this case, the filaments with rotating magnetic field, even if in each moment it is significantly inclined to the ambient magnetic field, may propagate through the magnetosphere, if their average (for the rotation period) magnetic field is aligned with the ambient magnetic field. This shows that neglecting the rotation of magnetic field in these filaments may lead to wrong results.

A theoretic analysis of magnetoactive GES-based turbulent solar plasma instability

“…In a special case of reduced plane parallel geometry ( ξ → ∞ , planar), our spherical ( ξ ∞ , non-planar) analysis shows a fair corroboration with the previously reported planar investigation founded on the same GES-based solar plasma direction (Gohain & Karmakar 2018 ). It shows a unique feature of the proposed GESbased theory against the diversified sheath formalisms available in the literature (Formisano et al 1973 ;Fairfield 1976 ;Mozer et al 1978 ;Gravier et al 2000 Langner et al 2006 ;Phan et al 2007 ;Richardson et al, 2008Richardson et al, , 2022Siscoe & Odstrcil 2008 ;Lazarian & Opher 2009 ;Richardson & Wang 2010 ;Schoeffler et al 2011 ;Wang et al 2012 ;Petrinec 2013 ;Robertson 2013 ;Lyatsky et al 2016 ;Chowdhury et al 2017 ;Chasapis et al 2018 ;Macek et al 2018 ;Rout et al 2018 ;Janvier et al 2019 ;Shaikh et al 2020 ;Ala-Lahti et al 2021 ;Sow Mondal et al 2021 ). An e xtensiv e comparison of the salient parametric features of the modified GES structures of current concern (Dwivedi et al 2007 ;Karmakar & Dwivedi 2011 ;Goutam & Karmakar 2015 ;Das & Karmakar 2022 ;Sarma & Karmakar 2022 ) against various other sheath (non-GES) patterns based on our integrated conceptional fabric for the sake of instant reference is briefly given in Appendix C .…”

Penetration of magnetosheath plasma into dayside magnetosphere: 1. Density, velocity, and rotation

“…Another possible mechanisms are the direct penetration into the magnetosphere of plasma filaments with the enhanced momentum (known also as "plasma blobs") [Lemaire, 1977;Lemaire and Roth, 1978;Heikkila, 1982;Lemaire, 1985;Lundin and Dubinin, 1984;Lundin, 1997;Echim and Lemaire, 2000;Lundin et al, 2003;Gunell et al, 2012, 2014, andothers]. This mechanism, however, was met with a skepticism based on the lack of convincing explanation of how these plasma structures (we will call them the filaments) with the magnetic field, which may be significantly inclined to the ambient (Earth's) magnetic field, may penetrate into the magnetosphere and move earthward.…”