Steepening of reflectivity structures detected in high-resolution Doppler spectra of polar mesosphere summer echoes (PMSE) observed with the EISCAT 224 MHz radar |
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| Institution: | 1. Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7, Canada;2. Space Weather Laboratoy, Mail Code 674, GSFC/NASA, Greenbelt, MD 20771, United States;3. Facultad de Cs. Astronomicas y Geofisicas, UNLP, y CONICET, Estacin Astronomica Rio Grande, Tierra del Fuego, Argentina |
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| Abstract: | Polar mesosphere summer echoes observed with the EISCAT 224 MHz radar frequently exhibit significant discontinuous offsets or jumps in the Doppler frequency. We can explain these frequency jumps as a result of a lifting of partially reflecting or scattering layers, which are distorted by bumps. These bumps can be caused by steepened refractivity variations, i.e. reflectivity structures. These suggestions are supported by model computations. We also notice that a relation exists between these structure shapes and gravity waves, which are steepened, but which do not necessarily break into enhanced turbulent velocity fluctuations. |
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