SuperDARN stands for Super Dual Auroral Radar Network. This network consists of over 20 radars operating on frequencies between 8 and 20 MHz and looking into the polar regions of the Earth. These radars can measure the position and velocity of charged particles in the Earth's ionosphere, the highest layer of the Earth's atmosphere. Because the movements of these particles are tied to the movements of the Earth's magnetic field which, in turn, extends into space, SuperDARN data provides scientists with information regarding the Earth's interaction with the space environment.

SuperDARN is an international collaboration involving scientists and funding agencies of over a dozen countries (see Chisham et al., 2007 and references therein). Information on the operation of SuperDARN, real time displays, and links to data archives can be found at the JHU/APL SuperDARN web site (http://superdarn.jhuapl.edu/). The Doppler shift of the backscatter is proportional to the line-of-sight component of the ExB plasma drift in the scattering region (Villain et al., 1985; Ruohoniemi et al., 1987).

At the present time there are fourteen SuperDARN radars in the northern hemisphere and eight in the southern hemisphere. A detailed description of SuperDARN as it existed at the start of the International Solar Terrestrial Physics mission is given in Greenwald et al. (1995). In brief, SuperDARN radars utilize an array of electronically phased antennae that can be steered in 16 beam directions stepping in azimuth every 3.3 degrees for a total sector of 50 degrees, repeating every one or two minutes. For each direction, the radar detects backscatter within 45 km long range gates that begin at 180 km and extend to a maximum range that is usually greater than 3500 km. All the radars are essentially identical, with some minor differences in antenna design and to accommodate the physical conditions at the site. Each of the radars has two arrays of antennae. The primary array consists of sixteen antennae, and the secondary, interferometer array, consists of four antennae. A phasing matrix attached to the antenna array is used for beam forming and electronically steers the radar into one of sixteen different beam directions. The radar transmits a short sequence of pulses in the HF band and samples the returning echoes. The sequence of pulses, referred to as a multi-pulse sequence, is carefully designed to allow the Doppler characteristics of different targets to be determined at multiple ranges by using the Auto-Correlation Function (ACF) of the received samples, while the secondary antenna array provides vertical angle-of-arrival information that can be used to determine their altitude. Many sequences are transmitted and the calculated ACFs integrated over a period of several seconds to minimize the effect of noise. The final average ACF is then used to calculate the backscattered power, spectral width and Doppler velocity of the plasma density irregularities in the ionosphere. All SuperDARN radars operate continuously (except for very infrequent data outages) and typically operate at a temporal resolution of 1-2 minutes.