3 Apr 2008; Mat-Nat Faculty (UiTø), room A228. Thursday 12:15-14:00

Einar Mjølhus

The ”Z mode”.

I have recently become a little bit engaged into some work with a group at Lancaster, GB. The explanation of certain observations made using Heating and EISCAT at Ramfjordmoen, which they wish to pursue, involves the so-called “Z-mode” of electromagnetic propagation. This is a topic on which I worked and published during the 1980s, partially together with Tor Flå (Mjølhus and Flå, J. Geophys. Res. 89A, 3921-3928, 1984). The group at Lancaster needed a ray tracing of the Z mode as illustration in the paper that they wish to write, and then asked me to provide the ray tracing (presumably because they are quite busy themselves).

In the seminar, I shall start by showing the experimental results from EISCAT for which an explanation is needed. Then I shall give a brief introduction to the “Cold plasma” theory of electromagnetic propagation, leading to the O and X modes, and explain what the physicists mean by the Z mode. I shall probably also include a brief historical account. Finally, I shall tell about my work on the ray tracing computation during this winter, which is not at all research, but which nevertheless implied some minor challenges, and a surprise which turned into a useful lesson.