Movie‐maps of low‐latitude magnetic storm disturbance

We present 29 movie‐maps of low‐latitude horizontal‐intensity magnetic disturbance for the years 1999–2006: 28 recording magnetic storms and 1 magnetically quiescent period. The movie‐maps are derived from magnetic vector time series data collected at up to 25 ground‐based observatories. Using a technique similar to that used in the calculation of Dst, a quiet time baseline is subtracted from the time series from each observatory. The remaining disturbance time series are shown in a polar coordinate system that accommodates both Earth rotation and the universal time dependence of magnetospheric disturbance. Each magnetic storm recorded in the movie‐maps is different. While some standard interpretations about the storm time equatorial ring current appear to apply to certain moments and certain phases of some storms, the movie‐maps also show substantial variety in the local time distribution of low‐latitude magnetic disturbance, especially during storm commencements and storm main phases. All movie‐maps are available at the U.S. Geological Survey Geomagnetism Program Web site (http://geomag.usgs.gov).