Disturbance storm time index; 1903 Sun outburst

Occurring in the weak Solar Cycle 14 just after its minimum, the extreme space weather event in 1903 October-November is one of these cases. Here, we reconstruct the time series of geomagnetic activity based on contemporary observational records.

With the mid-latitude magnetograms, the 1903 magnetic storm is thought to be caused by a fast coronal mass ejection (~1500km/s) and is regarded as a superstorm with an estimated minimum of the equivalent disturbance storm time index (Dst') of ~-531nT. The reconstructed time series has been compared with the equatorward extension of auroral oval (~44.1 in invariant latitude) and the time series of telegraphic disturbances.