Statistics on Jupiter's Current Sheet with Juno Data: Geometry, Magnetic Fields and Energetic Particles

<p>Jupiter's magnetosphere contains a current sheet of huge size near its equator. The current sheet not only mediates the global mass and energy cycles of Jupiter's magnetosphere, but also provides an occurring place for many localized dynamic processes, such as reconnection and wave-particle interaction. To correctly evaluate its role in these processes, a statistical description of the current sheet is required. To this end, here we conduct statistics on Jupiter's current sheet, with four-year Juno data recorded in the 20-100 Jupiter radii, post-midnight magnetosphere. The results suggest a thin current sheet whose thickness is comparable with the gyro-radius of dominant ions. Magnetic fields in the current sheet decrease in power-law with increasing radial distances. At fixed energy, the flux of electrons and protons increases with decreasing radial distances. On the other hand, at fixed radial distances, the flux decreases in power-law with increasing energy. The flux also varies with the distances to the current sheet center. The corresponding relationship can be well described by Gaussian functions peaking at the current sheet center. In addition, the statistics show the flux of oxygen- and sulfur-group ions is comparable with the flux of protons at the same energy and radial distances, indicating the non-negligible effects of heavy ions on current sheet dynamics. From these results, a statistical model of Jupiter's current sheet is constructed, which provides us with a start point of understanding the dynamics of the whole Jupiter's magnetosphere.</p>

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.

Current sheets with multi-component plasma in planetary magnetospheres

<p>The self-consistent hybrid model of a thin current sheet with a thickness about several proton gyroradii in a space plasma is proposed, taking into account multicomponent collisionless space plasma. Several plasma components are often presented in planetary magnetotails (Hermean, Martian, Terrestrial and other ones). Influence of heavy oxygen ions with different properties on current sheet structure is analyzed. It is shown that high relative concentrations of oxygen ions, as well as their relatively high temperatures and flow drift speeds lead to a significant thickening of the sheet and a formation of an additional embedding scale. For some real parameters the profiles of self-consistent current densities and magnetic field have symmetrical jumps of derivatives, i.e. sharp changes of gradients. The comparison is made with observations in the Martian magnetosphere. The qualitative agreement of simulation results with observational data is shown.</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.