Modeling the effects of ionospheric oxygen outflow on bursty magnetotail flows

Abstract

Using a global multifluid MHD model, we demonstrate the effects of magnetospheric O⁺ on bursty magnetotail flows. We carry out two simulations without ionospheric outflow to use as baseline, one driven by real solar wind data and one driven by idealized solar wind. Solar wind data from 1 October 2001 are used as a storm time solar wind driver. During this event, the plasma sheet was observed to be rich in O⁺, making the event of interest for a model analysis of the effects of ionospheric origin O⁺ on magnetospheric dynamics. We carry out outflow comparison simulations for both the realistic and idealized solar wind drivers using a simple empirical model that places auroral outflow in regions where downward propagating Poynting flux and electron precipitation are present, combined with a low-flux thermal energy O⁺ outflow over the entire polar region. We demonstrate the effects of O⁺ on magnetotail structure and the occurrence rate and strength of bursty, fast earthward flows. The addition of O⁺ to the magnetotail stretches the tail and increases the velocity of bursty earthward flows. This increase is shown to be produced by reconnection events in an extended current sheet created by tail stretching.