email@example.com - last update: 11 May 1998, 1830 UT (RR)
Omega bands are large scale, discrete
auroral folds or wavy structures that may sometimes
develop into torch-like structures extending toward the
pole (Akasofu and Kimball, 1964; Akasofu, 1974).
Their main properties are:
For some recent modeling and observation of the omega bands, see Yamamoto et al.
(1997) and Pulkkinen et al. (1998), respectively.
- They occur typically during the recovery phase
of a substorm at the poleward boundary of a
diffuse aurora (equatorward oval of the
double oval structure typical for the recovery phase)
- The size of the structures can vary from a few hundred to several thousand kilometers
- They drift typically eastward at the velocity of 0.4 - 2 km/s (e.g., Opgenoorth et al., 1983),
although torches have sometimes seen drifting also westward
- The central regions of torch structures can be activity centers of
- The omega bands are accompanied by Ps 6 pulsations (T = 5 - 40 min)
- Akasofu, S.-I., A study of auroral displays photographed from the DMSP-2 satellite and from the
Alaska meridian chain of stations, Space Sci. Rev., 16, 617-, 1974.
- Akasofu, S.-I. and D. S. Kimball, The dynamics of aurora, 1, Instabilities of the aurora,
J. Atmos. Terr. Phys., 26, 205-, 1964.
- Opgenoorth, H., J. Oksman, K. U. Kaila, E. Nielsen, and W. Baumjohann, On the characteristics
of eastward drifting omega bands in the morning sector, J. Geophys. Res., 88, 9171-9185, 1983.
- Pulkkinen, T. I., D. N. Baker, L. A. Frank, J. B. Sigwarth, H. J. Opgenoorth,
R. Greenwald, E. Friis-Christensen, T. Mukai, R. Nakamura, H. Singer, G. D. Reeves,
and M. Lester, Two substorm intensifications compared: Onset, expansion, and global
consequences, J. Geophys. Res., 103, 15-27, 1998.
- Yamamoto, T., S. Inoue, and C.-I. Meng,
Formation of auroral omega bands in the paired region 1 and region 2 field-aligned
current system, J. Geophys. Res., 102, 2531-2544, 1997.