Abstract

John Coxon from the University of Southampton is visiting the British Antarctic Survey on February 9th – join us for an exciting seminar on space physics and electrodynamic interactions in near-Earth space. All are welcome!

Abstract:

Birkeland currents, also known as field-aligned currents, are currents which flow along Earth’s magnetic field lines, electrodynamically linking the magnetopause and partial ring current to the ionosphere. I use six years of observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) to investigate how Birkeland currents react to magnetic reconnection in the context of the Dungey cycle. I begin by establishing a correlation between magnetic reconnection and the amount of Birkeland current flowing, and then compare the Milan model to AMPERE data, showing that the current flow can be considered as a function of reconnection and conductivity (via solar zenith angle). As part of this, I detail an apparent disparity between the Northern and Southern Hemisphere, which may indicate a fundamental asymmetry between the two. Then, I specifically consider the reaction of Birkeland currents to nightside reconnection during substorms by performing two superposed epoch analyses to examine the current flowing in the system and the size of the current ovals on either side of substorm expansion phase onset, addressing open questions on the nature of the substorm current wedge.