SuperDARN stands for Super Dual Auroral Radar Network. This network consists of 32 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 plasma irregularities in the Earth's ionosphere, the highest layer of the Earth's atmosphere. The movements of these irregularities are tied to the movements of the Earth's geomagnetic field which, in turn, extends into space. Furthermore, the irregularities respond to energy coupled into the auroral regions from the solar wind and magnetosphere. Therefore, 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, as well as our U.S. partner institutions linked in the footer of this page. At the present time there are 21 SuperDARN radars in the northern hemisphere and 11 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 antennas 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 of radars are essentially identical in operational concept, although there are several antenna antenna element designs and interferometer configurations to accommodate the physical conditions at the site. Each of the radars has two arrays of antennas. The primary array consists of sixteen antennas, and the secondary interferometer array consists of four antennas. 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. Although, special processing and operating programs can be employed upon request.
