E. Joshua Rigler

Magnetic Storms and Induction Hazards

Magnetic storms are potentially hazardous to the activities and technological infrastructure of modern civilization. This reality was dramatically demonstrated during the great magnetic storm of March 1989, when surface geoelectric fields, produced by the interaction of the time-varying geomagnetic field with the Earths electrically conducting interior, coupled onto the overlying Hydro-Quebec electric power grid in Canada. Protective relays were tripped, the grid collapsed, and about 9 million people were temporarily left without electricity [Bolduc, 2002].

Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23–24

[1] Analysis is made of the geomagnetic-activity aa index covering solar cycle 11 to the beginning of 24, 1868–2011. Autocorrelation shows 27.0-d recurrent geomagnetic activity thatiswell-known tobeprominent duringsolar-cycle minima; some minima also exhibit a smaller amount of 13.5-d recurrence.Previous work hasshown that therecentsolar minimum 23–24 exhibited 9.0 and 6.7-d recurrence in geomagnetic and heliospheric data, but those recurrence intervals were not prominently present during the preceding minima 21–22 and 22–23. Using annual-averages and solar-cycle averages of autocorrelations of the historical aa data, we put these observations into a long-term perspective: none of the 12 minima preceding 23–24 exhibited prominent 9.0 and 6.7-d geomagnetic activity recurrence. We show that the detection of these recurrence intervals can be traced to an unusual combination of sectorial spherical-harmonic structure in the solar magnetic field and anomalously low sunspot number. We speculate that 9.0 and 6.7-d recurrence is related to transient large-scale, low-latitude organization of the solar dynamo, such as seen in some numerical simulations. Citation: Love, J. J., E. Joshua Rigler, and S. E. Gibson (2012), Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23–24, Geophys. Res. Lett., 39, L04102,

Methodology for time-domain estimation of storm time geoelectric fields using the 3-D magnetotelluric response tensors

Geoelectric fields at the Earths surface caused by magnetic storms constitute a hazard to the operation of electric-power grids and related infrastructure. The ability to estimate these geoelectric fields in close to real time and provide local predictions would better equip the industry to mitigate negative impacts on their operations. Here, we report progress towards this goal: development of robust algorithms that convolve a magnetic storm time series with a frequency domain impedance for a realistic three-dimensional (3D) Earth, to estimate the local, storm-time geoelectric field. Both frequency domain and time domain approaches are presented, and validated against storm-time geoelectric field data measured in Japan. The methods are then compared in the context of a real-time application.