AUTHOR=Biasiotti Lorenzo , Ivanovski Stavro , Calderone Lorenzo , Jerse Giovanna , Laurenza Monica , Del Moro Dario , Longo Francesco , Plainaki Christina , Marcucci Maria Federica , Milillo Anna , Molinaro Marco , Feruglio Chiara 

TITLE=Evidence of Kelvin-Helmholtz and tearing mode instabilities at the magnetopause during space weather events

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2024.1395775

DOI=10.3389/fspas.2024.1395775

ISSN=2296-987X

ABSTRACT=<p><bold>Introduction:</bold> Kelvin-Helmholtz (KH) and tearing mode (TM) instabilities are one of the most important mechanisms of solar wind energy, momentum and plasma transport within the magnetosphere.</p><p><bold>Methods:</bold> To investigate the conditions under which KHTM instabilities occur in the Earth environment it is fundamental to combine simultaneous multipoint <italic>in situ</italic> measurements and MHD simulations. We analyzed data from the THEMIS and Cluster spacecraft considering two Space Weather (SWE) events starting with an M2.0 flare event (hereafter Case-1) that occurred on 21 June 2015 and the most-intensive flare (X9.3) of solar cycle 24 that occurred on 6 September 2017 (hereafter Case-2).</p><p><bold>Results:</bold> Our analysis utilized a 2D MHD model for incompressible and viscous flow. The results from Case-1 indicate the presence of KH and TM instabilities, suggesting existence of observed low-amplitude oscillations at the nose of the magnetopause. However, the MHD simulations for Case-2 did not show any evidence of KH vortices, but did reveal the presence of “magnetic island” structures during a low-shear condition. The reconnection rate derived from the observations is compared with the computed one in the presence of developed instabilities inside the Earth’s magnetopause.</p>