Is Nightside Outflow Required to Induce Magnetospheric Sawtooth Oscillations

Abstract

Ionospheric outflow plays an important role in the mass coupling between the ionosphere and the coupled solar wind-magnetosphere system. Previous modeling studies have shown that outflowing ionospheric ions may induce magnetospheric sawtooth oscillations through mass loading of the magnetotail, stretching the magnetic field lines, and reducing nightside reconnection. The spatial distribution of polar cap outflow in these simulation studies produces significant outflow in the auroral oval and lacks a distinct cusp source. Thus, the question arises whether cusp outflow can induce sawtooth oscillations. We show controlled numerical experiments with magnetospheric sawtooth oscillations induced by an idealized cusp outflow for driving conditions representative of the interaction of an interplanetary coronal mass ejection with Earth's magnetosphere. The analysis shows that although only a small portion (10%) of the cusp outflow is entrained within the plasma sheet, it is effective in inducing magnetospheric sawtooth oscillations, similar to previous experiments.