Equatorial spread-F campaign over SHAR

A comparison of the equatorial spread F derived by the International Reference Ionosphere and the S 4 index observed by FORMOSAT-3/COSMIC during the solar minimum period of 2007–2009

“…The occur- rence of spread-F irregularities is associated with post sunset height rise in the F-region (Chandra and Rastogi, 1972) which is highly affected by the upward E × B drifts in prereversal enhancement (PRE), and is strongly dependent on the solar activity level and season (Fejer et al, 1991(Fejer et al, , 2008Scherliess and Fejer, 1999). Thus, it is conceivable to expect higher spread-F occurrence percentages by IRI during the sunspot maximum, which, in general, establishes a positive correlation between them (Fig.…”

Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

“…However, several investigators have reported ESF in post midnight period during geomagnetic disturbances earlier. Statistical analysis of ESF on geomagnetic quiet and disturbed days showed that ESF in the post midnight period could be more on disturbed days during low sunspot years and J-months (northern summer months) (Chandra and Rastogi, 1972). showed increase of ESF on disturbed days or high Kp days at Huancayo, Peru, in post midnight periods.…”

Statistical study of the night-time F-layer dynamics at the magnetic equator in West Africa during the solar minimum period 1995–1997

“…We have also compared our results to those of Chandra and Rastogi (1972b). These authors investigated the nocturnal variations in h F at different stations near the equator from 1955 to 1964.…”

“…This is probably because the h F data were averaged monthly in the above work, a method that sometimes conceals (or suppresses) variable and relatively lowamplitude variations such as the peak of phase III during the equinox periods. We should state here that, although Chandra and Rastogi (1972b) observed this seasonal dependence of the h F variation, they did not clearly show the transition period from the winter (the summer) to the summer (the winter) patterns. To our knowledge, the current study is the first to show the transition state between the two solstices which exhibits the evening and midnight uplifts on the same nights.…”

“…The transition from the A-type (E-type) to the E-type (A-type) patterns occurs in a few weeks around the equinox, during which both the uplifts are observed. Chandra and Rastogi (1972b) • N dip lat), India, they observed the presence of a sharp height peak at about 19:00 LT in DecemberJanuary that, progressively, becomes smooth and shifts to a later time around the midnight sector in June-July; it then, gradually, becomes sharp and shifts back to 19:00 LT by December. The authors attributed these changes to local seasonal effects or an asymmetry of the post-sunset height rise of the F layer over the magnetic equator during different seasons.…”