A Novel Magnetosphere–Ionosphere Coupling Model for the Onset of Substrom Expansion Phase

A novel magnetosphere–ionosphere (M-I) coupling model is proposed to simulate the brightening of the onset auroral arc of a magnetospheric substorm event. The new M-I coupling model is modified from the M-I coupling model proposed by the Alaska research team in 1988. We adjust the magnetospheric boundary conditions by including the Hall effects in the thin current sheet and allowing the spatial distributions of the reflection–transmission coefficient to vary with time. As a result, brightening and poleward drifting of multiple auroral arcs appear for the first time in an M-I coupling model. The new results indicate that the coupled Hall effects in the near-Earth plasma sheet and the E-region ionosphere play a vital role in triggering the onset of a magnetospheric substorm.

Solar wind-magnetosphere coupling in the form of recurrent substorms with one-hour periodicity

<p>The magnetospheric substorm is a response mode of the magnetosphere to solar wind driving. It has been shown that substorms can show repetitive behavior (that is, three or more substorms following each other with a quasi-period). The most common period is approximately three hours. A conclusive and satisfactory answer to the cause of this periodicity has not yet been given. Very limited mentioning of a shorter recurrence period, namely around one hour, has sparsely been appeared in the literature. In this presentation, we report on this lesser studied periodicity, giving observational examples from the THEMIS fleet. We compare the observations with global magnetosphere MHD simulations (BATS-R-US) of solar wind-magnetosphere coupling that incorporate kinetic corrections at the reconnection site. The similarity is striking, suggesting that indeed kinetic effects in tail reconnection are responsible - at least in some cases - for this periodic behavior of the magnetosphere.</p>

Embedding particle-in-cell simulations in global magnetohydrodynamic simulations of the magnetosphere

We have combined global magnetohydrodynamic (MHD) simulations of the solar wind and magnetosphere interaction with an implicit particle-in-cell simulation (PIC) and used this approach to model magnetic reconnection at both the dayside magnetopause and in the magnetotail plasma sheet. In this approach, we first model the magnetospheric configuration driven by the solar wind using the MHD simulation. At a time of interest (usually when a thin current sheet has formed in the MHD simulation), we load a large particle-in-cell simulation with plasma and fields based on the MHD state. We use the MHD results to set the boundary conditions on the PIC simulation. The coupling between the two models is one way – the PIC results do not change the MHD results. In these calculations, we use the UCLA global MHD code and the iPic3D implicit particle-in-cell code. In this paper we describe this technique in detail. As an example of this approach, we present PIC results on reconnection in the magnetotail during a magnetospheric substorm.