Department of Geophysics



Parameters α, β and φ are used to calculate PC index basing on data of magnetic measurements at stations Thule and Vostok. Angle φ determines the optimal orientation of the magnetic disturbance vector δF related to the geoeffective interplanetary electric field EKL in different UT times. Coefficients α and β are the linear regression parameters, slope and intersection, connecting values δF and PC. The parameters α, β and φ were derived independently by data for solar maximum epoch (1998-2001) and by data for solar minimum epoch (1997, 2007-2009). It was demonstrated that usage of a proper quiet daily variation (QDC), as a level of reference for values of the polar cap magnetic disturbance, leads to invariance of the parameters a, β and f irrespective of the solar activity epoch. Afterwards, the parameters α, β and φ were calculated by data for full cycle of solar activity (1995-2005) to derive the statistically justified quantities for any minute of any day of year. Thus, parameters a, β and f presented in Table with 1-min resolution are regarded as valid for ever provided the appropriate quite daily variation (QDC) are used. The  parameters are given for leap and usual years.

Parameters α, β and φ