The 3-hour telluric index is a measure of disturbance in the horizontal component of the geoelectric field over a 3-hour interval. Each period is designated with a code in the range 0-9, with 1 or less being 'quiet' and 5 or more indicating storm levels.

The designated code is derived from the range of the variations in each 3-hour period

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.