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S‐transform view of geomagnetically induced currents during geomagnetic superstorms
Author(s) -
Pulkkinen Antti,
Kataoka Ryuho
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl025822
Subject(s) - geomagnetically induced current , earth's magnetic field , geomagnetic storm , substorm , local time , ionosphere , storm , geophysics , physics , magnetosphere , geology , meteorology , magnetic field , mathematics , statistics , quantum mechanics
A novel time‐frequency analysis method (S‐transform) capable of handling noisy non‐stationary signals is applied to study the properties of geomagnetically induced current (GIC) fluctuations in the Finnish natural gas pipeline. New local time‐ and storm phase‐dependent S‐transform spectral properties of auroral region GIC fluctuations during geomagnetic superstorms are reported. More specifically, the S‐transform spectra have two distinct regions containing the most of the spectral power that persisted from storm to storm: main phase‐related wide‐band fluctuations driven possibly by a substorm‐type ionospheric activity centered around the local midnight and recovery phase‐related narrow‐band fluctuations associated with Pc5 range geomagnetic pulsations in the local morning region. Based on this observed “stability”, a new S‐transform‐based statistical approach using, for example, an ensemble of different S‐transform responses for known storms is proposed for GIC prediction.