Investigation of Space Weather Effects by Swarm Magnetic Field Data: The
SFAC Index
Abstract
The three Swarm satellites provide an optimum, low Earth orbit (LEO) and
multi-spacecraft platform, to explore for the first time the local
correlation between field-aligned currents (FACs), auroral electrojets,
and magnetic perturbations at the Earth’s surface. By Swarm and ground
magnetic field data together, one can investigate systematically the
full correlation chain, whose final link controls the ground induced
currents and related space weather effects. We introduce an integrated
FAC product, the Sheet FAC (SFAC) index, as a convenient measure of the
in-situ FAC data, and check the correlations SFAC-AE, SFAC-PEJ and
SFAC-dH, with AE the standard auroral electrojet index, PEJ the local,
Swarm based, polar electrojet index, and dH the horizontal magnetic
field perturbation at the Earth’s surface. Given the good SFAC-dH
correlation, we also suggest an extension of SFAC to higher LEO
satellites, which cannot observe any more the electrojet currents, but
are fully capable to monitor SFAC.