التفاصيل البيبلوغرافية
| العنوان: |
PIC Simulations of Overstretched Ion‐Scale Current Sheets in the Magnetotail. |
| المؤلفون: |
Arnold, H.1 (AUTHOR) harryarnold@gmail.com, Sitnov, M. I.1 (AUTHOR) |
| المصدر: |
Geophysical Research Letters. 8/16/2023, Vol. 50 Issue 15, p1-10. 10p. |
| مصطلحات موضوعية: |
*CURRENT sheets, *MAGNETIC fields, *CURRENT distribution, *FORCE density, *ORBITS (Astronomy) |
| مستخلص: |
Onset of reconnection in the tail requires the current sheet thickness to be of the order of the ion thermal gyroradius or smaller. However, existing isotropic plasma models cannot explain the formation of such thin sheets at distances where the X‐lines are typically observed. Here we reproduce such thin and long sheets in particle‐in‐cell simulations using a new model of their equilibria with weakly anisotropic ion species assuming quasi‐adiabatic ion dynamics, which substantially modifies the current density. It is found that anisotropy/agyrotropy contributions to the force balance in such equilibria are comparable to the pressure gradient in spite of weak ion anisotropy. New equilibria whose current distributions are substantially overstretched compared to the magnetic field lines are found to be stable in spite of the fact that they are substantially longer than isotropic sheets with similar thickness. Plain Language Summary: Ion scale current sheets forming sufficiently far from Earth are necessary to explain its stretched magnetic field reconfiguration on the night side. However, isotropic plasmas form magnetic fields that inflate with distance from Earth and cannot reproduce the observed stretched geometry. We present kinetic simulations of current sheets that inflate more gradually with distance due to slight field‐aligned anisotropy of the ion species. Their formation is provided by a special population of suprathermal ions with figure‐of‐eight orbits. We find that the resulting current sheets are stable over a long time scale and have a thickness comparable to the size of these orbits. Key Points: Two‐dimensional ion‐scale current sheets stretched way beyond the isotropic limit are reproduced in particle‐in‐cell simulationsWeak ion anisotropy and agyrotropy substantially modify the current density and the isotropic force balanceIon‐scale current sheets are stable in spite of the fact that they are longer compared to isotropic sheets with similar thickness [ABSTRACT FROM AUTHOR] |
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