Browsing by Author "Rastogi, R. G."
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Item Open Access Abnormally large magnetospheric electric field on 9 November 2004 and its effect on equatorial ionosphere around the world(Springer Verlag, 2012-10) Rastogi, R. G.; Chandra, H.; Condori, Louis; Abdu, M. A.; Reinisch, B.; Tsunoda, R. T.; Prasad, D. S. V. V. D.; Pant, T. K.; Maruyama, T.There was a solar event around 1850 UT on 9th November 2004, associated with an abnormally large solar wind flow pressure and large southward interplanetary magnetic field, causing an abnormally large prompt penetration electric field between 1850 and 2100 UT. Abnormally large vertical F-region drifts by Jicamarca backscatter radar were reported associated with the event. The F-region over Jicamarca, Peru (14–16 LT) and Sao Luis, Brazil (16–18 LT) was lifted upward, broken into two portions and the upper one was blown out of the range of the ionosonde. At Fortaleza, an off-equatorial station in Brazil, the F-region was also lifted up but later the foF2 increased due to the flow of ionization from upper layer blown up over the equatorial region. The F-region at Ascension Island (19–21 LT), an off-equatorial station, was lifted up without any deformations till 1915 LT but descended at 1930 LT due to reversal of electric field polarity. At Indian stations, Trivandrum and Waltair (00–02 LT), the F-region was pushed down and later disappeared as a consequence of enhanced westward ionospheric electric field in the night sector. The ionosonde did not receive any echo for a couple of hours till the next sunrise. The F-region at Kototaban (03–05 LT), Indonesia also disappeared after a rapid descend. At Kwajelien (06–08 LT) there was no equatorial type of sporadic-E at 07 to 09 LT due to the westward electric field.Item Restricted Solar cycle effects on the electric fields in the equatorial ionosphere(American Geophysical Union, 1977-11-01) Woodman Pollitt, Ronald Francisco; Rastogi, R. G.; Calderón, C.The horizontal east‐west electric fields in the equatorial F region are estimated by using the vertical electron drift data over Jicamarca, Peru. The reversal of the electric field from west to east near the sunrise hours is not affected by solar cycle, but the evening reversal is found to occur about 1 hour earlier during low‐sunspot years. The average value of the electric field magnitude during noon hours is the same for different portions of the solar cycle; however, the day to day variation is larger during years of low solar activity. The postsunset increase of the electric field is characteristic of high‐sunspot periods only. Abnormal reversals of the electric field are seen on some occasions during the daytime hours, and these events are associated with the equatorial counter electrojets.Item Restricted Spread-F during the magnetic storm of 22 January 2004 at low latitudes: Effect of IMF-Bz in relation to local sunset time(Springer Verlag, 2014-08) Rastogi, R. G.; Chandra, H.; Janardhan, P.; Lan Hoang, Thai; Condori, Louis; Pant, T. K.; Prasad, D. S. V. V. D.; Reinisch, B.The paper describes the results of spread-F at low latitude stations around the world during the magnetic storm starting at 0130 UT on 22 January 2004. The storm can be divided into two phases, first phase up to 1000 UT when interplanetary magnetic field IMF-Bz was highly fluctuating around a small positive value and the second phase after a sudden large southward turning of IMF-Bz at 1030 UT. The first phase produced strong spread-F at Jicamarca, Sao Luis, and Ascension Island and caused complete inhibition of spread-F at Thumba and Waltair in India. It generated weak spread-F at Ho Chi Minh City in Vietnam and strong spread-F at Hainan and Chung Li. The strong spread-F at Hainan and Chung Li were caused by the positive IMF-Bz during the first phase of the storm and not by the negative pulse of IMF-Bz at 1000 UT.Item Restricted Sudden disappearance of vhf radar echoes from equatorial e-region irregularities(Council of Scientific and Industrial Research, 1977-01) Rastogi, R. G.; Fejer, B. G.; Woodman Pollitt, Ronald FranciscoThe Modified Range Time lntensity Technique for studying the height variation of the (back-scatter power of vhf radar echoes at Jicamarca has been used to show that the growth lime of E-region irregularities is less than 1 min. Further, these irregularities disappear or reappear precisely at the time when AH at an equatorial minus AH at a non-equatorial station is close to zero irrespective of absolute H over the dip equator. This is consistent with the idea that E-region irregularities over the dip equator scattering the hf or vhf radio waves are due to gradient drift instability and supports the double-current hypo1hcsis for the equatorial electrojet.