The USGS Dst and Magnetic-Disturbance Mapping Project

Magnetic-observatory data and their derivative magnetic indices are useful for monitoring the conditions in Earth's surrounding space environment. The storm-time disturbance index, Dst, is of particular importance – it can be interpreted in terms of the energy of an equivalent magnetospheric ring-current, and, as such, it is a fundamental measure of magnetic-storm intensity. Dst was invented by Sugiura 50 years ago, as part of the International Geophysical Year (IGY), and today the Kyoto World Data Center provides an operational Dst service. Using data from four standard observatories, the Kyoto index is calculated once per hour and is available in near-real time (within the hour) over the internet. However, given the relatively large number of observatories that are now in operation, and the information-rich content of the data that they produce, there is abundant opportunity to develop a more refined version of Dst and other, more elaborate storm-time disturbance measures. Working in coordination with the US National Space Weather Program, and, in particular, the US Air Force, the Geomagnetism Program of the US Geological Survey has recently undertaken a multi-faceted project for measuring, monitoring, and analyzing low-latitude magnetic disturbance. This project is focused on four specific subjects: (1) developing algorithms for accurately extracting magnetic-disturbance signals from the data records of individual observatories, (2) re-analyzing historical magnetic-observatory data recording magnetic disturbance over the past 50 years, and, eventually, over the past 100+ years, (3) mapping the geography of storm-time disturbance and depicting results as movies, and (4) providing a 1-minute Dst and related magnetic-activity measures to the space-weather community in near-real time. In this presentation, all of this work will be discussed and summarized.