Supervisor : Prof Mark Lester (mle@le.ac.uk)

Details of Project

The Polar Mesosphere is the coldest naturally occurring place in the earth's environment reaching a minimum temperature of 130 degrees Kelvin. The mesospheric temperature reaches a minimum at its upper boundary, the mesopause, which is also the boundary between the ionised elements of the upper atmosphere and the neutral middle and lower atmosphere and so is a unique and important location for understanding processes external to the earth which may affect the climate of the planet. It is becoming increasingly clear that such effects may contribute to climate variability and as a boundary within the atmosphere, the mesopause is an important place to look for signs of such effects.

Noctilucent cloud over Stonehenge. These clouds are thought to be associated with Polar Mesospheric Summer Echoes.

The Super Dual Auroral Radar Network (SuperDARN) is a network of HF coherent scatter radars which are operate din both northern and southern polar regions. SuperDARN is considered to have started as a network in 1995 when there were 6 radars in the north and 4 in the south. Currently there are 17 in the north and 9 in the south, with more being deployed in 2012. The radars have identified signatures of echoes from between 80 and 90 km, the mesopause region, and these echoes have been related to Polar Mesosphere Summer Echoes (see Ogawa et al., 2002, 2003). but unlike other systems operating at VHF and LF the HF SuperDARN signatures occur at oblique incidence.

The main purpose of this project will be to determine a method by which the oblique incidence PMSE-like scatter in the SuperDARN radars can be identified routinely. This will then be followed by a series of studies investigating the variation of the scatter over the lifetime of the network, some 17 years currently, to investigate the annual variability, the solar cycle variability and the interhemispheric variability. 

Background Reading

Ogawa, T., et al., Geophys. Res. Lett., 29(7), DOI: 10.1029/2001GL014094, 2002.
Ogawa T., et al., Ann. Geophys., 21, 1047-1055, 2003
Ogawa T., et al., Ann. Geophys., 22, 4049-4059, 2004
Hosokawa K., et al., 31(2), L02106 DOI: 10.1029/2003GL018776, 2004
Hosokawa K., et al., 32(12), L12801 DOI: 10.1029/2005GL022788, 2005