Field-aligned electron density irregularities near 500 km: Equator to polar cap topside sounder observations
Article first published online: 7 DEC 2012
This paper is not subject to U.S. copyright. Published in 1985 by the American Geophysical Union.
Volume 20, Issue 3, pages 477–485, May-June 1985
How to Cite
1985), Field-aligned electron density irregularities near 500 km: Equator to polar cap topside sounder observations, Radio Sci., 20(3), 477–485, doi:10.1029/RS020i003p00477.(
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Accepted: 17 DEC 1984
- Manuscript Received: 9 AUG 1984
Striking evidence, in addition to spread F, for field-aligned electron density irregularities is commonly observed on postsunset Alouette 2 topside sounder ionograms recorded near perigee (500 km). This evidence is provided by distinctive signal returns from sounder-generated Z mode waves. At low latitudes these waves become guided in wave ducts caused by field-aligned electron density irregularities and give rise to strong long-duration echoes. At high latitudes, extending well into the polar cap, transmitted Z mode waves (and stimulated electrostatic waves at the plasma frequency and trapped ordinary mode echoes) produce a series of vertical bars on the ionogram display as the satellite traverses discrete field-aligned density structures. Within 15° dip latitude of the dip equator, Z mode wave ducts were encountered on about one third of the ionograms sampled; beyond 75° invariant latitude, vertical bar phenomena were encountered on more than three fourths of the ionograms sampled.