Seminars

Lecturer: Dr Peter Dalin (IRF-Kiruna)
Date: 2005-05-26 10:00
Place: Aniara

On the Nature of Polar Mesosphere Winter Echoes: Experimental Data and Modeling

Polar Mesosphere Summer Echoes (PMSE) are strong radar echoes returned by thin layers lying between 80-90 km altitude, close to the summer mesopause at high latitudes. PMSE are thought to be due to strong enhancements of the scattered signal due to the presence of small charged ice-aerosols. Low temperatures of the summer mesopause provide favorable conditions for formation of ice-particles and in turn the PMSE.

Relative new phenomena, Polar Mesosphere Winter Echoes (PMWE), are strong radar echoes scattered from heights of 50-80 km in winter and they are greatly resemble the PMSE in summer. However the nature of the former is completely unknown because winter mesospheric temperatures are too high for ice particles to be formed.

In this study we analyse strong PMWE occurrences observed during the MAGIC campaign in January 2005 by EISCAT and Esrange VHF radars. Using available models for incoherent scatter radar spectra we investigate the possible roles of turbulence, negative and positive ions, charged meteoric dust particles and chemical fluctuations in the creation of the PMWE. We compare these results with experimental spectra.

Created 2005-04-01 13:42:51 by Rick McGregor
Last changed 2005-05-17 13:54:06 by Rick McGregor