The dynamical background of polar mesosphere winter echoes from simultaneous EISCAT and ESRAD observations

• Main Authors: Belova, E., Kirkwood, S., Ekeberg, J., Osepian, A., Häggström, I., Nilsson, Hans, Rietveld, M.
• Other Authors: Swedish Institute of Space Physics Kiruna (IRF), Polar Geophysical Institute of Russian Academy of Sciences (PGI), Russian Academy of Sciences Moscow (RAS), EISCAT Scientific Association
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; EISCAT
• Online Access: https://hal.science/hal-00317706; https://hal.science/hal-00317706/document; https://hal.science/hal-00317706/file/angeo-23-1239-2005.pdf

International audience On 30 October 2004 during a strong solar proton event, layers of enhanced backscatter from altitudes between 55 and 75km have been observed by both ESRAD (52MHz) and the EISCAT VHF (224MHz) radars. These echoes have earlier been termed Polar Mesosphere Winter Echoes, PMWE. After considering the morphology of the layers and their relation to observed atmospheric waves, we conclude that the radars have likely seen the same phenomenon even though the radars' scattering volumes are located about 220km apart and that the most long-lasting layer is likely associated with wind-shear in an inertio-gravity wave. An ion-chemistry model is used to determine parameters necessary to relate wind-shear induced turbulent energy dissipation rates to radar backscatter. The model is verified by comparison with electron density profiles measured by the EISCAT VHF radar. Observed radar signal strengths are found to be 2-3 orders of magnitude stronger than the maximum which can be expected from neutral turbulence alone, assuming that previously published results relating radar signal scatter to turbulence parameters, and turbulence parameters to wind shear, are correct. The possibility remains that some additional or alternative mechanism may be involved in producing PMWE, such as layers of charged dust/smoke particles or large cluster ions.