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DC trains and Pc3s: Source effects in mid‐latitude geomagnetic transfer functions
Author(s) -
Egbert Gary D.,
Eisel Markus,
Boyd O. Sierra,
Morrison H. Frank
Publication year - 2000
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 - 10.1029/1999gl008369
Subject(s) - earth's magnetic field , geomagnetic latitude , ionosphere , latitude , geology , magnetotellurics , longitude , geophysics , range (aeronautics) , geodesy , physics , magnetic field , electrical resistivity and conductivity , materials science , quantum mechanics , composite material
Magnetotelluric (MT) data from two sites 150 and 300 km southeast of San Francisco, California (geomagnetic dipole latitude: 43 degrees, L approximately 1.9) show that the usual MT assumption of spatially uniform external magnetic fields is violated to a significant degree in the period range 10–30 s. Inter‐station transfer functions exhibit large systematic temporal variations which are consistent with a combination of two distinct sources: electromagnetic noise due to the San Francisco Bay Area Rapid Transit (BART) DC electric railway, and Pc3 geomagnetic pulsations. There is a suggestion in the data that some of the Pc activity may actually be excited by BART.