A new type of magnetic activity forecast for high geomagnetic latitudes.

Abstract

A new multi-zone concept for forecasting magnetic activity at high geomagnetic latitudes (above 55°N), resulting in more definitive medium-term forecasts (for up to 27 days in advance) for the Canadian region, shows good agreement between forecast and observed levels. A magnetic activity index DRX (being the daily mean of the 24 one-hour ranges in the north component) calculated for each of three zones—polar cap, auroral, and sub-auroral—demonstrates the distinctly different characters of these magnetic zones. Accordingly, values of DRX are forecast for each of these three zones. Recurrent patterns of solar phenomena and their observed interactions with the geomagnetic field form the basis of the forecasting technique. Coronal holes predominate as sources of recurrent magnetic. activity. During an interval in 1984-1985, 88% of solar coronal holes were followed by an increase in geomagnetic activity.