March 31, 2001 geomagnetic storm
Auroral activity versus QSO activity
by Volker Grassmann, DF5AI, May 29, 2005
POES vs. QSOs
To compare the POES satellite data with the QSO data, the POES polar plots have been transfered to BeamFinder's Maidenhead grid locator map, see the lower panel. In the upper panel, we find the meridional distribution of the Aurora QSOs which has been discussed in the section operational results already. The following animation considers 28 sequences corresponding to the 28 satellite passages of the NOAA satellites on March 31, 2001. The dx QSOs are represented by blue lines which denote the great circle distance between the radio stations, i.e. the bending of the true radio propagation paths is not shown here.
Discussion of the results
Except of the map projection, we are facing the same POES data which we have discussed in the section Auroral activity. However, the westward drift of the Auroral activity appears in particular illustrative in this presentation. Note the bulge over the North American continent which results from the direction of the geomagnetic field, i.e. the southern expansion of Auroral activity follows the geomagnetic rather than the geographic latitudes.
Considering the North American sector, the amount of QSO data is clearly insufficient to support this analysis. A much more vivid QSO activity is available in the European sector. The animation documents several phases of high QSO activity and appears to reveal an unexpected feature: with high QSO activity, the blue lines show a criss-cross pattern which indicates a balance of north-south as well as east-west propagation paths. However, there are some sequences showing a pattern which appears dominated by east-west propagation paths, see fig. 2. Does this feature represent an accidential result or do Aurora band openings occasionally promote east-west propagation paths? Perhaps it is nothing else than a misinterpreation because east-west paths are generally longer than propagation paths in the north-south direction which affects the horizonatal and vertical size of the line pattern, of course - but why do we generally have a regular shaped criss-cross pattern then? Although mentioned here, this feature is currently not under investigation.
The most important question of this section addresses the correlation of the Auroral activity estimates derived from NOAA's POES data on one hand, and the occurence of Aurora dx QSOs on the other hand. Surprisingly, a systematical correlation does not become visible at all: we may find, for example, phases of low Auroral activity but high QSO activity (e.g., 13-14 UT) and we may find periods of high Auroral activity without any dx QSO at all (around 20 UT). Considering the results of the sections Auroral activity and Aurora QSOs & the interplanetary magnetic field, respectively, this result isn't actually that surprising. On March 31, 2001 the POES data shows high Auroral activity almost permanently independent, in particular, from the actual IMF direction, contrary to the QSO data which is strongly correlated to the Bz component of the interplanetary magnetic field. Thus, we actually need to address the question why the Auroral activity estimate appears almost independent from the actual field configuration. The author wishes to address the POES team again to clarify this question.