Local K-index scales correction for the high-latitude magnetic stations

Abstract

To assess the magnetic activity, various indices (numerical characteristics of the planetary and local disturbance of the Earth’s magnetic field) are used. Most widely used for various purposes are the planetary Kp-index and the local K-index, proposed by Bartels. The K-index characterizes the Earth’s magnetic field disturbance in a 3-hour interval (0–3, 3–6, etc. UTC) and is defined in a range from 0 to 9 by the amplitude of the horizontal component deviation from the quiet level. K = 0 indicates the absence of geomagnetic activity, and K = 9 corresponds to a strong geomagnetic storm. The lower limit of K = 9 is the amplitude of magnetic field horizontal component variation above which the K-index is assigned the maximum value of 9. This limit is selected individually for each station, depending on its geomagnetic latitude. The latest scales of the K-indices boundaries for the Russian Arctic stations were determined in the middle of the last century and have not been corrected since then. The significant discrepancy between the K-indices calculated using these scales and the planetary Kp-index shows that they had to be refined, and in some cases, they must be re-selected. The local indices lower boundaries (K = 9) for stations in the Arctic Russian sector were determined. K-indices lower boundaries were received for the strong magnetic storm according to the IAGA procedure. It is shown that for different magnetic field horizontal component variation values K-indices for different observation points practically coincide with the Kp-index. The lower value K = 9 dependence on the observation point geomagnetic latitude is presented. This relation can be used to obtain the lower boundary of K = 9 for any magnetic station. A table with local K-index scales for Russian Arctic magnetic stations has been compiled.