A scheme for forecasting severe space weather

<p>We have developed and tested a scheme for forecasting severe space weather (SvSW) that caused all known electric power outages and telecommunication system failures since 1957 and the Carrington event of 1859. The SvSW events of 04 August 1972 has puzzled the scientific community as it occurred during a moderate storm (DstMin = -124 nT) while all other SvSW events occurred during super storms (DstMin ≤ -250 nT). The solar wind velocity V and IMF Bz measured by ACE satellite at the L1 point since 1998 are used. For the earlier SvSW events such as the Carrington event of 1859, Quebec event of 1989, and the events in February 1958 and August 1972 we used the information from the literature. The coincidence of high ICME front (or shock) velocity ΔV (sudden increase in V over the background by over 275 km/s) and sufficiently large Bz southward at the time of the ΔV increase is associated with SvSW; and their product (ΔV×Bz) is found to exhibit a large negative spike at the speed increase. Such a product (ΔV×Bz) exceeding a threshold seems suitable for forecasting SvSW, with a maximum forecasting time of 35 minutes using ACE data. However, the coincidence of high V (not containing ΔV) and large Bz southward does not correspond to SvSW, indicating the importance of the impulsive action of high ΔV and large Bz southward coming through when they coincide. The need for the coincidence is verified using the CRCM.</p>