Solar wind interaction with the giant magnetospheres and Earth

Abstract:

Comparative studies are essential for testing our understanding of the terrestrial magnetosphere. However, comparative studies can run amok in a quagmire of paradoxes if hasty generalizations from one magnetosphere are applied to other magnetospheres. The solar wind interaction is perhaps the most debated comparative aspect between Earth and the giant magnetospheres. Jupiter and Saturn are fundamentally different from Earth, driven primarily through the combination of rapid rotation and internal plasma sources. Centrifugal stresses and the resulting outward plasma transport distort the planetary magnetic field into a magnetodisc structure with magnetosphere-ionosphere coupling currents that produce internally-driven auroral emissions. Eventually, plasma is lost to the solar wind through a centrifugally-driven, Vasyliunas-cycle of magnetic reconnection. One could argue that the Vasyliunas-cycle represents the zeroth order state of the giant magnetospheres with the solar wind simply providing the requisite pressure balance to shape the magnetospheric cavity. However, significant dawn-dusk asymmetries in magnetic field topology and plasma properties suggest that the solar wind must play a more significant role. Conditions for magnetopause reconnection coupled with the sheer physical scale might indicate that Jupiter and Saturn are not simple Dungey magnetospheres, driven by large-scale reconnection. Instead, the recent debate has also invoked viscous processes (e.g., Kelvin-Helmholtz instabilities) as a mediator of the solar wind interaction. This presentation will summarize the ongoing solar wind interaction debate and highlight lessons that can be applied to magnetospheric physics through comparative studies.