Large-scale longitudinal variation in ionospheric height and equatorial spread F occurrences observed by ionosondes
Article first published online: 29 AUG 2007
Copyright 2007 by the American Geophysical Union.
Geophysical Research Letters
Volume 34, Issue 16, 28 August 2007
How to Cite
2007), Large-scale longitudinal variation in ionospheric height and equatorial spread F occurrences observed by ionosondes, Geophys. Res. Lett., 34, L16109, doi:10.1029/2007GL030618., and (
- Issue published online: 29 AUG 2007
- Article first published online: 29 AUG 2007
- Manuscript Accepted: 31 JUL 2007
- Manuscript Revised: 29 JUL 2007
- Manuscript Received: 8 MAY 2007
- equatorial ionosphere;
- equatorial spread F;
- longitudinal structure
 Variations in ionospheric height associated with the prereversal enhancement (PRE) at two equatorial ionosonde stations separated by 6.34° in longitude were studied for the first time. The stations used were in Chumphon (10.7°N, 99.4°E, 3.3 Mag. Lat.), Thailand and Bac Lieu (9.3°N, 105.7°E, 1.6 Mag. Lat.), Vietnam. Variations in the virtual height of the bottomside of the F region (h′F) at 2.5 MHz observed at these two stations were analyzed for a period in March and April 2006. When the equatorial spread F (ESF) was not observed, h′F variations at the two stations were very similar, with a local time shift corresponding to the longitude separation. However, when ESF was observed, they were often significantly different. Our results show that h′F enhancement, which could be interpreted as being due to the eastward electric field enhancement, is quite localized in longitude when ESF occurs.