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Solar Wind Control of Magnetosheath Jet Formation and Propagation to the Magnetopause
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  • Adrian T. LaMoury,
  • Heli Hietala,
  • Ferdinand Plaschke,
  • Laura Vuorinen,
  • Jonathan P. Eastwood
Adrian T. LaMoury
Imperial College London

Corresponding Author:adrian.lamoury15@imperial.ac.uk

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Heli Hietala
Imperial College London
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Ferdinand Plaschke
Space Research Institute, Austrian Academy of Sciences
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Laura Vuorinen
University of Turku
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Jonathan P. Eastwood
Imperial College London
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Magnetosheath jets are localized high-dynamic pressure pulses originating at Earth’s bow shock and propagating earthward through the magnetosheath. Jets can influence magnetospheric dynamics upon impacting the magnetopause; however a significant fraction dissipate before reaching it. In this study we present a database of 13,096 jets observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft from 2008–2018, spanning a solar cycle. Each jet is associated with upstream solar wind conditions from OMNI. We statistically examine how solar wind conditions control the likelihood of jets forming at the shock, and the conditions favorable for jets to propagate through the magnetosheath and reach the magnetopause. We see that, for each solar wind quantity, these two effects are separate, but when combined, we find that jets are nearly 12 times more likely to reach and potentially impact the magnetopause when the interplanetary magnetic field (IMF) is at a low cone angle, and approximately 5 times more likely during fast solar wind. Low IMF magnitude, high Alfvén Mach number, and low density approximately double the number of jets at the magnetopause, while plasma beta and dynamic pressure display no net effect. Due to the strong dependence on wind speed, we infer that jet impact rates may be solar cycle dependent as well as vary during solar wind transients. This is an important step towards forecasting the space weather effects of magnetosheath jets, as it allows for predictions of jet impact rates based on measurements of the upstream solar wind.
Sep 2021Published in Journal of Geophysical Research: Space Physics volume 126 issue 9. 10.1029/2021JA029592