ICS-13 Abstract View


Entropy in the plasmasheet/inner magnetospheric physics
Toffoletto, F., toffo@rice.edu (1)
Yang,.J., jian.yang@rice.edu (1)
Wolf, R. A., rawolf@rice.edu (1)
Sazykin, S., sazykin@rice.edu (1)
The flux tube entropy, defined as S=∫(p^(1/γ) ds/B), where p is the pressure and B is the magnetic field strength and the integral path (s) is over an entire flux tube, is conserved along a flow streamline in ideal MHD. On average, S increases tailward, so that the nightside tail region tends to be stable against interchange. In order for a plasma-sheet flux tube to be transported into the inner magnetosphere from the plasmasheet, its S value must be reduced so that it reaches equilibrium in a region where it matches the background value closer to the Earth. The most obvious way to reduce S is through magnetic reconnection in the tail, which is believed to be sporadic and results in transient bursts of rapid transport, termed "bursty bulk flows (BBFS) " or "bubbles". In this presentation, we will describe the impact of these low S bubbles on the inner magnetosphere and their role in substorms and ring current injection. For example, our simulations show that the main contribution to ring current energy during an intense storm main phase comes from particles inside bubble channels, and that during a substorm expansion such channels can contribute to the formation of the substorm current wedge.
(1) Physics and Astronomy Department, MS 108, Rice University, Houston, TX