Determination of the quiet daily geomagnetic variations for polar regions

Abstract

A novel procedure to derive the daily varying quiet level for polar geomagnetic data is presented. Recorded data from selected quiet intervals are weighted and superposed to form the basis for an estimate of the quiet daily curve (QDC) for the variation in each of the recorded components on any selected day. The quiet daily variation is controlled by the level of solar UV and X-ray emissions, and parameters in the solar wind in combination with the actual season and the location of the observatory. The procedure uses the variability in the recorded geomagnetic data rather than international magnetic indices like Kp to determine the quiet intervals in accordance with the concept proposed by Janzhura and Troshichev (2008). A special problem for the estimation of the QDC in polar regions is the influence from the solar wind sector structure acting particularly through the azimuthal component, IMF By, of the interplanetary magnetic field. In the superposition of recordings to estimate the QDC for any given day, the present procedure uses weighting functions to give preference to intervals with quietest conditions, closest to the day in question, exposed to the same face of the sun, and within the same sector of the solar wind. The effects of control parameters for the selection of quiet intervals and smoothing of the initial QDC values are carefully controlled. The procedure is fully automated and delivers quality control parameters in addition to the QDC values. It is considered a further step forward in the processing of geomagnetic data to derive reliable and reproducible QDCs for the difficult high-latitude regions.