The polar mesospheric summer echoes (PMSE) are very strong radar echoes observed in the frequency range of 2 MHz up to 1 GHz. Such radar echoes are attributed to the ice clouds formed in the mesosphere and are widely believed to link to global climate change. PMSEs are coherent echoes produced by plasma density fluctuations at half the radar wavelengts. This paper investigates the unresolved problem of short durability of plasma fluctuations at smaller wavelengths in upper atmospheric physics.

This paper introduces a new method for mapping electric fields in the magnetosphere along geomagnetic field lines. This is important for conjugate studies of electric fields measured in the ionosphere by SuperDARN radars, and at spacecraft carrying electric field probes. First elementary methods in a dipole field are reviewed and then the theory of of a new method described for general magnetic field models. The method is tested in a dipole model with a Harris magnetotail field.

The method of electric field mapping along geomagnetic field lines, derived in an accompanying paper, is applied to the International Geomagnetic Reference Field. Formulae for the geomagnetic field gradient tensor are derived and these are used in a software package developed to map the electric field. A number of examples are presented illustrating the method. The method will be of importance in conjugate studies of ionospheric convection when the external magnetic field can be neglected.

The equation for conservation of wave action is explicitly derived for magnetohydrodynamic waves in a plasma that varies slowly in space and time. Together with generalized ray-tracing equations, it is equivalent to a WKBJ solution of the problem and allows the computation of energy exchange between wave and background plasma as well as the variation of the amplitudes of the field components along the ray. The method is illustrated by application to simple examples.