Study of equatorial plasma bubble during January to April 2012 over Kolhapur (India)

Over 53 nights of all sky airglow imager data collected during January-April 2012 from the low latitude station Kolhapur (16.68°N, 74.26°E; 10.6°N dip latitude) have been analyzed to study the F-region dynamics through the imaging of OI 630 nm emission line. The observed night airglow data were supported by the ionosonde measurements from Tirunelveli (8.7°N, 77.8°E; 0.51°N dip latitude). Well defined magnetic field aligned depletions were observed during the observation period. Out of 53 nights, 40 nights exhibited the occurrence of north-south aligned equatorial plasma bubbles. These plasma bubbles were found moving towards east with drift speed in range between 70 to 200 m s-1. We have analyzed the zonal drift velocity variation and relation of bubble occurrence with the base height of the ionosphere together with the effects of the geomagnetic Ap and solar flux F10.7 cm index in its first appearance

Strength of the equatorial electro jet and geomagnetic activity control on VHF scintillations at the Indian longitudinal zone

163-171Amplitude scintillations on 244 MHz radio signals transmitted from geo-stationary satellite, FLEETSAT (73°E), were continuously recorded at a network extending from Ujjain (situated north of anomaly crest region) to the equatorial station, Trivandrum, by the Indian Institute of Geomagnetism, Mumbai. Parameters of geomagnetic activity like K-Alibag, Ap and electrojet strength are used to study the association of the amplitude scintillation recordings at the equatorial station, Trivandrum (dip 1° N ) and at Mumbai (dip 26°N), a station south of the anomaly crest region during the high solar activity period 1989-1991. It is observed that an increase in geomagnetic activity (K-Alibag or Ap) suppresses the occurrence of scintillation activity at both the stations, whereas the electrojet strength is found to have no association on the occurrence of scintillations. A total of 77 storms occurring during this period are classified into three types according to Aarons criterion. The time of the maximum intensity of ring current appears to play a role directly or indirectly in establishing the conditions necessary for the equatorial F-layer irrgularity generation and inhibition which, in turn, manifests itself in scintillation activity. However, there is about 30-40% of scintillation activity unaccounted by the magnetospheric electric field alone

Co-ordinated observations of VHF scintillations in India during February-March 1993

22-29The VHF scintillation observations made at a chain of stations in India during February-March 1993 under AICPITS (third campaign), using the 244 MHz radio beacon from FLEETSAT, and analysed jointly by all participating investigators at a workshop held at Raj kot are described. The occurrence features of scintillations during the third campaign were similar to those observed during the first campaign of March-April 1991. The maximum occurrence was, however, reduced to some extent due to the lower solar activity. The latitudinal variations showed an increased occurrence in the region of about 17-18o latitude. The data during the night of 19-20 Feb. 1993 when an extensive ‘Ionisation Hole Campaign’ was undertaken showed scintillations marked by earlier onset and longer duration at stations Waltair and Nuzvid than at the stat ions close to the magnetic equator. However, based on the average variations during February-March 1993 the onset at Tiruchendur, Anantpur and Walt air was at nearly the same time. The vertical rise velocity of the plasma depletions, estimated from the time delays in the onset of scintillations at latitudes away from the dip equator, was found to range from 40 m/s to 420 m/s in the altitude region 300-1350 km