Journal of Geophysical Research: Space Physics

Cover image for Vol. 122 Issue 8

Impact Factor: 3.426

ISI Journal Citation Reports © Ranking: 2014: 19/175 (Geosciences Multidisciplinary)

Online ISSN: 2169-9402

Associated Title(s): Journal of Geophysical Research

Steady convection keeps Earth's magnetic field in balance

The onslaught of the solar wind on the Sun-facing side of Earth's magnetic field causes terrestrial magnetic field lines to break through magnetic reconnection. The persistent pressure of the solar wind pulls the field lines and the associated plasma around to the magnetotail on Earth's nightside, where magnetic reconnection occurs once again to form the plasma sheet region. This uneven distribution creates a pressure gradient that drives nightside plasma back toward the planet. The Earthward transport of this nightside magnetospheric plasma is known to occur in one of two ways: as a magnetic substorm or as steady magnetospheric convection (SMC). Substorms include acute inflows that cause plasma to pile up in the inner magnetosphere and have been tied to the onset of auroras. SMC, on the other hand, has been proposed as a mechanism for rebalancing the plasma gradient established between the day and night sides of Earth's magnetic fields. Kissinger et al. (2012) compiled 14 years of magnetic field and plasma observations to study how plasma flows and magnetospheric conditions differ between SMC events and substorms. In satellite observations from as far as 30 RE into the magnetotail, the authors identified 2853 SMC events and 8600 isolated substorms. They found that SMC events are marked by highly energetic magnetotail plasma and a high rate of Earthward magnetic flux transport. Also, they found that SMC events are typically preceded by a magnetic substorm. The authors propose that the high-pressure inner magnetospheric plasma region formed by the preceding substorm causes SMC plasma flows to be diverted away from the Earth, instead arcing toward the planetary flanks and around to the dayside magnetic field. They suggest that the amount of plasma redistributed in this way could be enough to balance out the disrupting force of the solar wind.

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