Mini magnetospheres in the laboratory

Abstract

The interaction between plasmas and magnetic obstacles often occur in astrophysical and space environments such as in ion-scale “mini magnetospheres”. Such systems display a wide range of physical mechanisms and provide a unique environment for studying kinetic-scale plasma physics. In this work, we present collisionless particle-in-cell (PIC) simulations of ion-scale magnetospheres that reproduce recent laboratory experiments performed on the Large Plasma Device (LAPD) at UCLA. In our PIC simulations, a driver plasma flows against a dipolar magnetic field that is embedded in a uniform magnetized background plasma. The simulations replicate the main magnetospheric structures observed in the experiments, namely the magnetopause and the plasma current distributions. We show the formation of a magnetic cavity and a magnetic compression and two main current structures in the dayside region. From multiple parameter scans, we show a reflection of the magnetic compression, bounded by the length of the driver plasma, and a higher separation of the main current structures for lower dipolar magnetic moments. Additionally, we develop a analytical model that characterize the coupling between the driver and the magnetized background plasmas. The model is compared with the simulations, showing good agreement.

(Contactar Ana Bela Cardoso para password) ana.bela.cardoso@tecnico.ulisboa.pt