This page shows you what to look for in the live data links we provide. If you've read the introduction to aurorae then you'll recognise the terminology we use here.
Use the links below or in the text to open individual data windows.
Open a new window for the data.
This shows exactly what the earth's magnetic field is doing at the moment. The data is taken from a magnetometer near Aberdeen, Scotland.
Magnetic Field is measured in three different directions: the H-component is towards magnetic north; the D-component is along magnetic east-west; and the Z-component is perpendicular to the ground. The graph shows the H-component of the field as a black line, with a typical quiet day shown in blue. The difference between the current field and a quiet day is plotted as a colour-coded bar chart: green for quiet, orange for active and red for stormy.
The different stages of magnetic activity will all show up in the H-component. As a CME hits the magnetosphere, the compression of the magnetic field produces an increase in the field measured at ground level. This gives a characteristic rise in the field and is known as a Sudden Storm Commencement (SSC). Not all SSCs are followed by auroral activity, but it is a good early indicator. If the solar wind speed and IMF direction are favourable, the energy in the magnetosphere will gradually build up into a large storm, with the magnetic field decreasing and changing rapidly.
SAMNET York Data from 6/4/2000 - auroral activity was widely seen across England on this night.
|Sudden storm commencement (arrival of CME at magnetosphere).|
|Large deviations below the blue average line.|
|High activity towards midnight - the best observing time for aurorae.|