Global quiet day field variation model WDCA/SQ1



The quiet daily variations of the geomagnetic field, called Sq, have been modeled for the extremely quiet (solar-terrestrial disturbance) conditions using the digital values from magnetograms obtained from a worldwide distribution of observatories. This model, WDCA/SQ1, has been deposited at World Data Center A for Solar Terrestrial Physics as a set of data files and a Fortran computer program for retrieving the quiet variation field values at any world location, day of the year, and time of day. The WDCA/SQ1 model does not yet contain a solar-cycle adjustment; it is a best representation for the sunspot minimum period. Presently, the dependence on year is just an adjustment for the geomagnetic coordinate system. Nevertheless, even in active years the model provides an adequate description of the minimum Sq changes.