Flow and Aspect Angle Characteristics of 12-MHz and 50-MHz Coherent Echoes
In this study nearly simultaneous observations of auroral coherent echoes at Antarctic Syowa station at 12-MHz (SuperDARN) and 50-MHz (CRL radar) are considered to address several issues on the plasma physics of E-region irregularities. One event with large Doppler velocities of more than 600 m/s wa...
| Main Authors: | , , , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.540.8984 http://www.tiger.latrobe.edu.au/darn2000/cd/sessions/se/papers/koustov02.pdf |
| Summary: | In this study nearly simultaneous observations of auroral coherent echoes at Antarctic Syowa station at 12-MHz (SuperDARN) and 50-MHz (CRL radar) are considered to address several issues on the plasma physics of E-region irregularities. One event with large Doppler velocities of more than 600 m/s was selected. We show for this event that while 50-MHz echoes exhibit strong flow angle variation of the power, 12-MHz echoes do not. This means that the electrojet instability evolves into a more uniform flow angle distribution of density fluctuations at decameter scales as opposed to the meter scales. In spite of the expected differences in Doppler velocities of echoes due to significantly different scales of observed irregularities, data show that the velocities are very comparable, especially for observations along the magnetic L-shells (assumed electrojet direction). The aspect angle attenuation of Doppler velocity is found to be about the same at 12- and 50-MHz and consistent with earlier observations at 50-MHz. Estimates of the aspect angle effect for power are also consistent with earlier measurements. Both factors, ionospheric propagation conditions for radio waves and plasma physical effects for irregularities are considered in an attempt to explain several observed features. 1. |
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