Abstract
Abstract. The antennas of EISCAT have been used for interplanetary scintillation (IPS) studies of the solar wind for many years. The main science found from these studies is obtained through the cross-correlation of signals from antennas having the longest baseline, providing more accurate information on the different solar wind streams which may be present in the line of sight. The development of dual-frequency IPS observations between the 1.4 GHz receivers at the remote sites and Tromsø, has allowed the use of the EISCAT Svalbard Radar for IPS, increasing the available baselines to the extent that three solar wind streams can sometimes be identified in the cross-correlation functions. A weak-scattering model incorporating three possible solar wind streams and dual observing frequencies is discussed and some results presented. A recent study found that the current sampling bandwidth limits the sensitivity of IPS observations at EISCAT. Methods of increasing the sensitivity, and the results of trials, are discussed.
Highlights
Interplanetary scintillation (IPS) arises from the diffraction of radio waves from a distant, compact source by density variations within the solar wind
An added advantage of this ability is the use of the European Incoherent SCATter radar (EISCAT) Svalbard Radar (ESR) for IPS observations (Fallows et al, 2006), further increasing the length of baseline available and with it the accuracy with which solar wind speed and direction may be determined (Breen et al, 2006)
Whilst this is more than adequate for most EISCAT operations, it places a severe constraint on the recordable bandwidth for the much higher sampling rate used for IPS measurements
Summary
Interplanetary scintillation (IPS) arises from the diffraction of radio waves from a distant, compact source by density variations within the solar wind. The complication of a transmitting system has meant that the remaining antenna, at Tromsø, has yet to be upgraded and still uses the original observing frequency of 928 MHz. Whilst it is possible to obtain a reliable estimate of the mean solar wind velocity in the line of sight from a single-site IPS observation (Manoharan and Ananthakrishnan, 1990), cross-correlation over a long baseline provides a more accurate estimate of solar wind velocities even when more than one stream is present. An added advantage of this ability is the use of the EISCAT Svalbard Radar (ESR) for IPS observations (Fallows et al, 2006), further increasing the length of baseline available and with it the accuracy with which solar wind speed and direction may be determined (Breen et al, 2006).
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