Principal Component Analysis of Birkeland Currents Determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment
Monday, 23 May 2016: 4:50 PM
Steve E. Milan1,2, Jennifer Carter2, Haje Korth3 and Brian J Anderson3, (1)University of Bergen, Birkeland Centre for Space Science, Bergen, Norway, (2)University of Leicester, Physics and Astronomy, Leicester, United Kingdom, (3)The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States
Abstract:
Principle Component Analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). PCA identifies the patterns in the FACs that respond coherently to different aspects of geomagnetic activity. The region 1 and 2 current system is shown to be the most reproducible feature of the currents, followed by cusp currents associated with magnetic tension forces on newly-reconnected field lines. The cusp currents are strongly modulated by season, indicating that their strength is regulated by the ionospheric conductance at the foot of the field lines. PCA does not identify a pattern that is clearly characteristic of a substorm current wedge. Rather, a superposed epoch analysis of the currents associated with substorms demonstrates that there is not a single mode of response, but a complicated and subtle mixture of different patterns.
