Geoelectric power spectra over oceanic distances

Abstract

We present initial results of simultaneous measurements of the geoelectric potential as measured across two long cable routes in the Pacific (Guam to Philippines and California to Hawaii) separated by ∼6h in local time and ∼30° in latitude. Over the frequency range ∼10−5 to 1.67 × 10−3Hz the power levels tend to be enhanced near local noon along the two routes, especially during geomagnetic quiet intervals. During the seven days analyzed, geoelectric power levels up to 104 (mV/km)²/km were measured on a geomagnetically disturbed day. The power levels at the longest periods, ∼17m to ∼150m, are generally found to be largest along the route at lower geomagnetic latitudes (Guam to Philippines) when comparisons are made at equivalent local times. In contrast, the power levels for periods in the hydromagnetic wave region (periods ≲5m) tend to be larger at all local times for the higher geomagnetic latitude route. The nightside geoelectric power levels along the higher latitude route tend to increase with increasing geomagnetic activity.