Indices of Geomagnetic Activity
Daily regular magnetic field variation arise from current systems caused by regular solar radiation changes. Other irregular current systems produce magnetic field changes caused by the interaction of the solar wind with the magnetosphere, by the magnetosphere itself, by the interactions between the magnetosphere and ionosphere, and by the ionosphere itself.
K-index is quasi-logarithmic local index of the 3-hourly range in magnetic activity relative to an assumed quiet-day curve for a single geomagnetic observatory site. First introduced by J. Bartels in 1938, it consists of a single-digit 0 thru 9 for each 3-hour interval of the universal time day (UT).
The K-index, presented on these pages, is calculated by the J. Bartels algorithm. The raw data are coming from the fluxgate magnetometer, operating in Borok Geophysical observatory. The quiet-day curve of magnetic field is calculated as median averages from quiet days for each month. The deviations are converted using a semi logarithmic table created by J. Bartels, in to 3 hour K indices. The K-index is calculated from the more disturbed component (X or Y).
Latest data (February, 2020)