Please use this identifier to cite or link to this item:
http://hdl.handle.net/2248/3903
Full metadata record
DC Field | Value | Language |
---|---|---|
dc.contributor.author | Jayachandran, B | - |
dc.contributor.author | Balan, N | - |
dc.contributor.author | Rao, P. B | - |
dc.contributor.author | Sastri, J. H | - |
dc.contributor.author | Bailey, G. J | - |
dc.date.accessioned | 2008-09-26T16:56:23Z | - |
dc.date.available | 2008-09-26T16:56:23Z | - |
dc.date.issued | 1993 | - |
dc.identifier.citation | Journal of Geophysical Research, Vol. 98, No. A8, pp. 13741 - 13750 | en |
dc.identifier.issn | 0148-0227 | - |
dc.identifier.uri | http://hdl.handle.net/2248/3903 | - |
dc.description | Open Access | - |
dc.description.abstract | The relative importance of height, vertical drift velocity, and electron density gradient of the postsunset bottomside (5.5 MHz) equatorial F region for the onset of spread F is studied using simultaneous HF Doppler radar and ionosonde observations. The study conducted for the periods January-March of 1984 and 1985 shows that the height of the F layer, determined by the time history of the prereversal enhancement of the drift velocity, is the deciding factor for the onset of equatorial spread F (ESF) with little contribution from the electron density gradient. Maximum growth rate of linear collisional Rayleigh-Taylor instability occurs at the time of peak height rather than at the time of peak velocity confirming that, for the onset of ESF, the layer should attain a threshold height. The threshold (group) height of the 5.5 MHz layer falls from ∼450 km in 1984 (mean F10.7 equals 120) to ∼350 km in 1985 (mean F10.7 equals 70); the corresponding evening peak upward drift velocities decrease from about 30 m s−1 in 1984 to about 20 m s−1 in 1985. The significant fall of the thresholds with the declining solar activity is due to the decrease in the ion-neutral collision frequency with declining solar activity; the fall of the thresholds is reflected in large decreases in the intensity and duration of the spread F | en |
dc.language.iso | en | en |
dc.publisher | American Geophysical Union | en |
dc.relation.uri | http://www.agu.org/pubs/crossref/1993/93JA00302.shtml | en |
dc.subject | HF doppler radar | en |
dc.subject | Solar activity | en |
dc.title | HF doppler and ionosonde observations on the onset conditions of equatorial spread F | en |
dc.type | Article | en |
Appears in Collections: | IIAP Publications |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
HF doppler and ionosonde observations on the onset.... | Open Access | 500.27 kB | Adobe PDF | ![]() View/Open |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.