Figure 2

Time series recording 20 min of east geoelectric field variation in the early stage of the 2003 Halloween storm. Shown are measured \({E_{y}^{m}}\) data (black), estimated G E _y variation for optimal model parameters determined from Kakioka data recording the 2003 Halloween storm (#4 in Table 1, purple), and estimated G E _y variation for model parameters determined from five different magnetic storms (#A in Table 1, green).