| Abstrakt: |
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, many jets 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 spacecraft from 2008 to 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 over 17 times more likely to reach and potentially impact the magnetopause when the interplanetary magnetic field (IMF) orientation is at a low cone angle, and approximately 8 times more likely during high speed solar wind. Low IMF magnitude, high Alfvén Mach number, and low density approximately double the number of jets at the magnetopause, while β 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 magnetospheric effects of magnetosheath jets, as it allows for predictions of jet impact rates based on measurements of the upstream solar wind. Plain Language Summary: When the solar wind, a constant flow of plasma from the Sun, meets Earth's magnetic field, a shock wave forms in space. Like a rock in a stream, the plasma is diverted around the obstacle and a dense, turbulent layer—the magnetosheath—forms in front of it. We study instances of fast plasma jets bursting through the shock and traveling towards Earth. However, it appears that only a small proportion of jets hit the edge of our magnetic field—the magnetopause. To forecast their effects, we therefore need to know when jets will make it through. We use a database of 13,096 jets observed by spacecraft in the magnetosheath, alongside measurements of the solar wind, to determine when jets are most likely to hit the magnetopause. We find the highest probability is when the solar wind magnetic field is aligned with its flow direction and when it has a higher speed. We hope that, with this information, we may eventually be able to forecast space weather effects of jets based solely on measurements of the upstream solar wind. Key Points: Time History of Events and Macroscale Interactions during Substorms and OMNI data from 2008 to 2018 are used to constrain conditions for jet formation and propagation to the magnetopauseJets reach the magnetopause 17x more often during low IMF cone angles (<33°) and 8x more often during high solar wind speeds (>539 km/s)Low interplanetary magnetic field magnitude, high Alfvén Mach no., and low density double expected magnetopause impacts, dynamic pressure and β have no net effect [ABSTRACT FROM AUTHOR] |
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