The quick summary plots give 1-month overviews of the net auroral magnetic perturbations, or dB, (top panels, red & blue traces) recorded by the Iridium satellites together with the equatorward limit of these perturbations (lower panels, black trace). These are very useful for identifying periods have significant geomagnetic activity.

ASCII data files of the data shown in these quick summary plots are available.

Time is in Julian day with 1.000 = 0000 UTC on January 1.

The net dB is the difference between the maximum eastward and maximum westward directed perturbations. The dB are calculated as the average over the 95-100% (red) and 45-55% (blue) percentile ranges. The 95-100% range indicates the maximum net dB. The maximum dB that any given spacecraft would observe is roughly half of this value.

The minimum latitude is the lowest latitude at which perturbations above the noise detection threshold were observed. Because these are magnetic latitudes offset by 3 degrees toward midnight, the range of geographic latitudes is about 14 degrees poleward and equatorward from those shown here. (Because of the Earth's 11 degree dipole axis offset from the rotation axis, 70 degrees magnetic defines a circle in geographic latitude spanning roughly 59 to 81 degrees. In addition , the auroral oval is displaced to the nightside by about 3 degrees giving a net offset range of plus and minus 14 degrees from geographic.)

These data are derived from the daily data survey plots available under Daily Plots. See the descriptions under Daily Plots for more on how these quantities are evaluated.

There are some spikes in the data due to known hiccups in the processing. They have mostly been removed from the quick summary data but are still evident in the April data.

For the July 1999 example you should note the anti-correlation between dB and the minimum latitude - this reflects the fact that the auroral oval expands as the currents become more intense. You can readily identify the most geomagnetically active days as 202-203 (July 21-22), 209, and 211-212. For each of these cases dB exceeded 1000 nT and the auroral oval expanded equatorward of 60 degrees MLAT.