Prediction of the geomagnetic K index based on its previous value. Geophysica

• Main Authors: Ari Viljanen, Antti Pulkkinen, Risto Pirjola
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2008
• Subjects: Sodankylä
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.573.4975; http://www.geophysica.fi/pdf/geophysica_2008_44_1-2_003_viljanen.pdf

The statistical behaviour of the geomagnetic K index is studied at two observatories in Finland: Nurmijärvi in the subauroral region and Sodankylä near the auroral region. Using data of 19532006, we show that the present K index can be used as a proxy for predicting the future indices. Especially, the statistical prediction of the nearest future index yields a clearly different value compared to the overall average of the given UT time. Long-term statistical predictions up to three months forward also reveal the 27 days periodicity related to the solar rotation. We tested the prediction method by deriving statistics for the years 19532002 and applied the results for 2003. About 72 % of the predicted expectation values of the nearest future K are within one unit from the observed K and about 96 % differ at most two units. Analysis of the 20 cases with the prediction error larger than 3 units shows that a sudden start of a large storm is impossible to forecast by using ground magnetic field alone, as expected. Key words: geomagnetic forecasting, geomagnetic variations, K index 1.