Figure 6From: The characteristics of geoelectric fields at Kakioka, Kanoya, and Memambetsu inferred from voltage measurements during 2000 to 2011The northward geoelectric field from 1 January 2002 to 31 December 2005 at Kakioka. (a) Observed hourly values, (b) the trend component estimated by the robust Kalman filter procedure, and (c) the residual of the geomagnetic field when the trend is subtracted.Back to article page