Field-aligned ionospheric E-region irregularities and sporadic E
Article first published online: 7 DEC 2012
Copyright 1973 by the American Geophysical Union.
Volume 8, Issue 3, pages 235–246, March 1973
How to Cite
1973), Field-aligned ionospheric E-region irregularities and sporadic E, Radio Sci., 8(3), 235–246, doi:10.1029/RS008i003p00235., , and (
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Received: 29 JUN 1972
A continuous series of oblique backscatter observations at 19 MHz made at Plum Island, Massachusetts (56°N invariant), over nearly half a solar cycle is utilized to derive the occurrence characteristics of aspect-sensitive field-aligned irregularities in the E-layer and their association with ground-backscattered echoes which are propagated via sporadic E (E8) reflection. Under quiet magnetic conditions, it is found that the field-aligned echo from E-layer heights, FAE(E), displays a summer evening maximum in conjunction with the E8 echo. A weak secondary maximum is observed in the winter with no detectable field-aligned structures being evident in the daytime E8. During disturbed magnetic conditions, the E8 ground-backscattered echo is greatly suppressed together with a simultaneous increase of the FAE(E) which also appear in the daytime; no seasonal control is evident. One year's continuous observations at 49 MHz with a narrowbeam antenna showed the quiet time, E8-associated FAE(E) to be of the discrete type, whereas the FAE(E) obtained during storms were found to be diffuse in nature. These observations are discussed from the point of view of current plasma instability theories.