A Ground-Up Data-Driven Approach to Distinguishing Magnetospheric
Sources of Geomagnetically Induced Currents > 10 A during
the 17 March 2013 Event
Abstract
We combine wavelet analysis and data fusion to investigate
geomagnetically induced currents (GICs) on the Mäntsälä pipeline and the
associated horizontal geomagnetic field, BH, variations during the late
main phase of the 17 March 2013 geomagnetic storm. The wavelet analysis
decomposes the GIC and BH signals at increasing ‘scales’ to show
distinct multi-minute spectral features around the GIC spikes. Four GIC
spikes > 10 A occurred while the pipeline was in the dusk
sector – the first sine-wave-like spike at ~16 UT was
‘compound.’ It was followed by three ‘self-similar’ spikes two hours
later. The contemporaneous multi-resolution observations from
ground-(magnetometer, SuperMAG, SuperDARN), and space-based (AMPERE,
TWINS) platforms capture multi-scale activity to reveal two
magnetospheric modes causing the spikes. The GIC at ~16
UT occurred in two parts with the negative spike associated with a
transient sub-auroral eastward electrojet that closed a developing
partial ring current (PRC) loop, whereas the positive spike developed
with the arrival of the associated mesoscale flow-channel in the auroral
zone. The three spikes between 18-19 UT were due to bursty bulk flows
(BBFs). We attribute all spikes to flow-channel injections (substorms)
of varying scales. We use previously published MHD simulations of the
event to substantiate our conclusions, given the dearth of timely
in-situ satellite observations. Our results show that multi-scale
magnetosphere-ionosphere activity that drives GICs can be understood
using multi-resolution analysis. This new framework of combining wavelet
analysis with multi-platform observations opens a research avenue for
GIC investigations and other space weather impacts.