Dst (Disturbance Storm Time) is an index designed to measure the intensity of geomagnetic activity over the Atlantic region.

Original attempts for defining Dst were made by Kertz (1958 and 1964) and Sugiura (1964) with a derivation scheme first proposed by Sugiura and Hendricks (1967) and further improved by Sugiura and coworkers (1969) when it was adopted by the International Association for Geomagnetism and Aeronomy (IAGA). The definitive values of Dst are published by Data Analysis Center for Geomagnetism and Space Magnetism, Kyoto, Japan on behalf of the International Service for Geomagnetic Indices (ISGI), a service of IAGA.

The version presented here is an estimate, derived from measurements made at the near-equatorial magnetic observatory on Ascension Island (ASC), in the Atlantic. Dst (ASC) index is derived from the ASC one-minute horizontal magnetic field variations.

Following the method deployed for the derivation of the official Dst, the secular variation trend and solar quiet (Sq) diurnal variations are estimated and removed from the observatory measurements. The data are then transformed to the dipole equator equivalent, giving Dst (ASC).

About the data:

Data supplied here are real-time estimates derived by BGS and, unlike the definitive Dst, which is an hourly index, Dst (ASC) is computed for every one-minute.

Rollover the data values on the plot or in the table for pop-up information. All estimates are marked with the letters \"BGS-estimate\".

Main page

To select the data set you want to see, and the range of dates and/or times you want to see it over, click the Select Data button and enter the relevant information in the dialog.

For data sets that can be viewed at different dates and/or times, use the Previous and Next buttons to step backward and forward by the date/time range currently shown on the page. Use the Most Recent button to see the most recently available data. The Next and Most Recent buttons will be disabled when the most recent data is displayed. The Previous button will be disabled when the page is showing the earliest data available for the current data set.

Select Data dialog

Select the data set you want to see from the drop-down menu.

Where applicable, select the observatory (observatories) or region(s) from the drop-down menu.

Where applicable, enter two dates/times separated by '-' in the input box to specify the date/time you want to see. Alternatively, select a date/time range using the date picker.