Radar Studies of the Solar Corona: A Review of Experiments Using HF Wavelengths.
NAVAL RESEARCH LAB WASHINGTON DC
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The use of high frequency 9 to 40 MHz, high power radars to study the solar corona has a remarkable history. Solar radar experiments were proposed and started at the beginning of the modern era of space physics research. Early in the 1960s the El Campo solar radar facility began routine operations. The published results from these pioneering experiments remain our largest resource of information on active probing of the solar corona. In 1969, solar radar experiments ceased even though experimental results suggested that significant diagnostics of the solar corona could be obtained with this technique. After the El Campo facility was decommissioned, a hiatus of about 25 years followed for further solar radar experiments. Recently, high frequency radar facilities in Russia and Ukraine have been used to conduct new solar radar experiments. The information that solar radars may provide is particularly relevant today, as we now recognize the important role of coronal mass ejections in geomagnetic disturbances. Solar radars offer the possibility of direct detection of earthward-moving coronal mass ejections, providing several days of advance warning to possible geomagnetic storms. In addition, investigations of wave scattering in the solar corona may provide information on coronal densities and irregularities. The techniques derived for studies of the earths ionosphere using incoherent scatter radars are potentially applicable to the solar corona as well. We will review the early and current solar radar experiments and also discuss future directions for radar studies of the solar corona.
- Active and Passive Radar Detection and Equipment