Plasma Seminar: The Effects of Outflow on CME and SIR Driven Sawtooth Events

Oliver Brambles, Thayer School of Engineering

Tuesday, January 15, 2013, 3:30pm

MacLean B01

Magnetosphere sawtooth oscillations have been observed during coronal mass ejection (CME) driven events when the solar wind conditions are relatively steady, and also during periods when the IMF fluctuates between northward and southward, such as during stream interaction regions (SIR).

The impact of ionospheric outflow on the CME-driven April 18, 2002 and SIR-driven October 24, 2002 sawtooth events is investigated using a multifluid adaptation of the Lyon-Fedder-Mobarry global simulation. The mechanisms that generate the sawtooth oscillations are investigated through the comparison of a baseline simulation without outflow and a simulation that includes an O+ outflow model. The ionospheric outflow is regulated by a statistical relationship between Alfvenic Poynting flux and O+ ion outflow flux.

In the baseline simulation for the April 18, 2002 event one substorm is observed which is generated by the southward turning of the IMF, after which the magnetosphere-ionosphere (MI) system settles in a quasi-steady convection mode. When outflow is included, quasi-periodic substorms are observed suggesting that the sawtooth oscillations are generated internally by the effects of the O+ ions. However, during the October 18, 2002 event quasi-periodic substorms are generated regardless of whether outflow is, or is not included. For this event, the generation and triggering of the substorms is controlled by the external driving of the solar wind. For both events, when outflow is included the signatures of the substorms are more typical of sawtooth substorms compared to the baseline simulation; the signatures of the substorms are more intense and more noticeable across a wider range of local times.