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AKR [Oulu]

Auroral kilometric radiation (AKR)

spaceweb@oulu.fi - last update: 2 December 1998, 1000 UT (RR)

Auroral kilometric radiation (AKR) is bursty electromagnetic emission at about 100 - 500 kHz related to auroral arcs, i.e., dusk and evening side discrete auroras. Because of this, field-aligned potential drops must play some role in AKR production. The source region altitude is about 3000 - 20000 km; however, at a given time only a small altitude range is operational.

The radiation is believed to be generated at frequencies near the local electron cyclotron frequency f_ce, which often acts as low-frequecy cutoff for the waves. It is composed of both extraordinary and ordinary modes, with the extraordinary mode dominating.

For more information see, e.g., Bahnsen et al. (1989).

References

Bahnsen, A., B. M. Pedersen, M. Jespersen, E. Ungstrup, L. Eliasson, J. S. Murphree, R. D. Elphinstone, L. Blomberg, G. Holmgren, and L. J. Zanetti, Viking observations at the source region of auroral kilometric radiation, J. Geophys. Res., 94, 6643-6654, 1989.