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3rd LOIS Workshop, November 24-25, 2002 Växjö University, Växjö, Sweden |
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Brett Isham
isham@129.242.31.34
EISCAT and University of Tromsø
Tromsø, Norway
AbstractSolar radar science goals encompass both space weather connections and cutting edge microphysics, including scattering processes and Langmuir turbulence. Because the radar probe signal backscatters at or close to the critical plasma level, solar radar transmissions undergo significant refraction effects during propagation, and modeling and ray tracing will therefore form key parts of the data analysis and interpretation. The required echo amplitude can be judged using data from the El Campo solar radar, which operated from 1961 to 1969. For imaging and other advanced analysis, a transmitter capable of radiating at least one and preferably several MW of continuous power is required.
Distributed transmission will be critical in traversing the
ionosphere. Such a system would use several or many transmitters,
relatively widely distributed in location, each at low or relatively
low power so as not to induce ionospheric modification effects. The
beams and waveforms would be designed to coherently merge on the way
to the sun into a single high-power beam. Reception would also be
distributed using the aperature synthesis technique, in order to form
a radar image of the sun. Aperature synthesis is already being used
on natural solar emissions and is planned for other new radio
telesopes including LOFAR, which could be used as a second, or
possibly bistatic, receiver for LOIS. The high level of background
solar emissions ("noise" for solar radar) and the many possibilities
for localized and distributed scattering centers will significantly
affect what we expect to see for a given transmitter power and
receiving antenna geometry; these details may be investigated using
experience already gained in the use of aperature synthesis in radio
astronomy.
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