August 4, 1972 revisited: A new look at the geomagnetic disturbance that caused the L4 cable system outage

Abstract

Abstract. Space weather effects on the ground are produced by magnetic field changes associated with electric currents resulting from the solar wind/magnetosphere interaction. For most ground events the principal currents involved are the auroral electrojet systems. However, on August 4, 1972, there was a major magnetic disturbance and an outage of the L4 cable system in the mid-western US that was thought to be caused by currents on the magnetopause. New model calculations now show that the observed magnetic disturbance was too localised to have been caused by magnetopause currents. Contour plots of the disturbance are instead consistent with an ionospheric current as the source. Equivalent current plots derived from the observed magnetic field variations show that a rapid intensification of an eastward electrojet was responsi ble for the magnetic disturbance and the cable system outage.

Method of auxiliary sources for calculating the magnetic and electric fields induced in a layered Earth

“…The geoelectric and geomagnetic ÿelds calculated at the surface of the Earth using the CIM have been shown to agree very well with exact calculations for several models of the Earth's conductivity structure Pirjola and Viljanen, 1998;Pirjola and Boteler, 2002). The algebraic expressions for these ÿelds lead to very rapid computation making the CIM a desirable method for investigating geomagnetic induction and the resulting GICs (Viljanen et al, 1999a, b;Boteler and van Beek, 1999;Boteler et al, 2000;Pulkkinen et al, 2000;Pirjola et al, 2000;.…”

Space Weather

“…However, recent model calculations by Boteler and Jansen van Beek (1999) have shown that the observed magnetic disturbance was too localised to have been caused by magnetopause currents. Contour plots of the disturbance are instead consistent with an ionospheric current as the source.…”

“…The outage for nearly an hour of a major continental telecommunications cable that stretched from near Chicago to the west coast was disrupted between its Illinois and Iowa power stations by the magnetic storm of August 1972 [Anderson et al, 1974;Boteler and Jansen van Beek, 1999]. In March 1989, the entire province of Quebec suf fered a power outage for nearly a day as major transform ers failed under the onslaught of a large geomagnetic storm [Czech et al, 1992].…”

Space Storms and Space Weather Hazards

“…The magnetic storm of February 1958 disrupted voice communications on the first cross-Atlantic telecommunications cable, TAT-1, from Newfoundland to Scotland (and also plunged the Toronto area into darkness by the tripping of power company circuits). The outage for nearly an hour of a major continental telecommunications cable that stretched from near Chicago to the west coast was disrupted between the Illinois and Iowa powering stations by the magnetic storm of August 1972 Boteler and Jansen van Beek, 1999]. In March 1989, when the entire province of Quebec suffered a power outage for nearly a day as major transformers failed under the onslaught of a large geomagnetic storm [Czech et al, 1992], the first cross-Atlantic fibre voice cable was rendered nearly inoperative by the large potential difference that was established between the cable terminals on the coasts of New Jersey and England [Medford et al, 1989].…”