Polar Mesospheric Summer Echoes

Height-time-intensity diagram of Polar Mesospheric Summer Echoes, called "PMSE". These data were recorded in Trømso, Norway, with the EISCAT VHF radar operating on 224 MHz with vertical beam and about 1.2 MW peak power, applying a 64-bit complementary code with a height resolution of 150 meters. The color code covers signal levels of about 0 dB (blue) to 25 dB (red) above the background noise level.

These Polar Mesospheric Summer Echoes are not caused by the conventional incoherent or turbulence scatter process, but by some irregularity structure in the electron density profile, which may be related to steep electron density gradients, heavy positive ions, dressed aerosols, gravity waves and turbulence or other yet unknown mechanisms. These echoes frequently exhibit dramatic height and intensity variations as well as large variations in Doppler shift, i.e. vertical velocity. Some of the morphology of Polar Mesosphere Summer Echoes (observed also on other radar frequencies between 2 MHz and 1300 MHz) is quite similar to that of Noctilucent Clouds

[from EISCAT Annual Report 1988, © EISCAT Scientific Association, P.O. Box 812, S-981 28 Kiruna, Sweden]

Send mail to Jürgen Röttger (for more information on PMSE)