Updated: 13 March 2013
Geomagnetic Data from Australia
Geomagnetic indices have been developed to characterise the variability of the Earth's magnetic field, in all its complexity, in a single number. There are many such indices that each characterise a different aspect or time-frame of the dynamic geomagnetic field. The most widely used of these is the K index, a quasi-logarithmic index of geomagnetic activity relative to an estimated undisturbed or regular quiet day variation for the recording site. Links to sites with other magnetic indices and information can also be accessed from this page.
The k index is a quasilogarithmic index of geomagnetic activity relative to an assumed quiet day curve for the recording site. k is a code from 0-9 that characterizes magnetic activity (0 being the least active field and 9 the most active field) over a 3 hour period.
k indices from the Canberra (from 1980 to present) and Gnangara (1995 to present) observatories are available online.
An estimated k index for Learmonth is available from IPS.
The aa index is three hourly index of geomagnetic activity determined from the k indices scaled at two antipodal subauroral stations: Canberra Australia, and Hartland England.
For each three hour interval, k indices measured at the two stations are converted back into amplitude. A three hour aa index is the mean of the northern and southern values, weighted to account for the small differences in the latitudes of the two stations.
The index is calculated at the International Service for Geomagnetic Indices (ISGI), France.
The International Services of Geomagnetic Indices (ISGI) is in charge of elaboration and dissemination of magnetic indices. Any magnetic indices not found on this website can be accessed through the ISGI site.
International Quiet Days (IQD's) are the days where the geomagnetic variations are a minimum in each month.
International Disturbed Days (IDD's) are 5 days in each month where the geomagnetic variations are maximum.
The classification of days is relative only to the month of calculation. The average disturbance level in one month may differ from another.
IQDs and IDDs are derived at Potsdam - GFZ.
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