Articles written in Journal of Earth System Science
Volume 87 Issue 7 July 1978 pp 109-113
Geomagnetic disturbance effects on the occurrence of range and frequency spread at Huancayo are studied for the period 1957–74. The occurrence of frequency spread is decreased on disturbed days for
Volume 87 Issue 11 November 1978 pp 215-224
Daily variations of the E-W and N-S components of ionospheric drifts, measured using closely spaced receiver method over Tiruchirapalli near magnetic equator, are described for the periods 1973–75 for
Volume 88 Issue 1 March 1979 pp 41-49
A number of spaced fading records obtained at Buckland Park, South Australia, using partial reflection technique (at 80–100 km) have been subjected to different methods of analysis, viz., time delay methods, the full correlation method and the cross-spectrum method. True drift velocities derived from the full correlation method appear to be the most correct. The variation of velocity with fading frequency obtained from cross-spectrum method is most likely to be due to the variation of velocity with time within the record itself.
Volume 88 Issue 1 March 1979 pp 57-68
The nature of the
Volume 89 Issue 2 July 1980 pp 153-157
Faraday rotation measurements made at a chain of stations and group delay measurements made at Ootacamund from ATS-6 are examined for the partial solar eclipse event of 29 April 1976. There is no evidence of eclipse-induced gravity waves in these measurements extending from Ootacamund near dip equator to Patiala (dip 45° N). Eclipse-induced fluctuations were however reported at Trivandrum, about 300 km south of Ootacamund.
Volume 95 Issue 1 March 1986 pp 83-89
Ionospheric drift records obtained by the closely spaced receiver technique at Udaipur are subjected to low and high pass filtering with varying cutoff frequencies and the effects of filtering on various drift and anisotropy parameters as determined by full correlation analysis are studied. Limits in which filtering could be employed are suggested on the basis of results obtained.
Volume 100 Issue 3 September 1991 pp 255-265
Two meteor events which were sighted in the Gujarat skies of India, were accompained by the visibility of sporadic
Volume 125 Issue 3 April 2016 pp 669-675
The geomagnetic storm of November 1998 is a unique event where IMF-Bz remained southward withvalues exceeding –15 nT for more than a day. The SYM/H index decreased from about 07 hr on 13November 1998 reaching a minimum of about –120 nT around midnight of 13–14 November 1998.Features of the equatorial electrojet in the Indian region are studied during the geomagnetic storm eventof 13–14 November 1998, based on the geomagnetic data from the chain of observatories in India. Suddennorthward turning of IMF-Bz for a very short duration around 08 hr on 13 November 1998 resultedin a small and very short duration counter electrojet. A strong (–50 nT) and a long duration counterelectrojet, right from 08 to 13 hr on 14 November 1998 was observed resulting in the absence of equatorialEs at Thumba. Absence of the equatorial ionization anomaly was also observed as seen from theionograms over Thumba and ionspheric data from Ahmedabad. The delayed effect on 14 November 1998is due to the disturbance dynamo effect.
Volume 126 Issue 4 June 2017 Article ID 0051
The effect of solar flare, sudden commencement of magnetic storm and of the disturbances ring current on the equatorial electrojet in the Eastern Brazil region, where the ground magnetic declination is as large as 20∘W is studied based on geomagnetic data with one minute resolution from Bacabal during November–December 1990. It is shown that the mean diurnal vector of the horizontal field was aligned along 2∘E of north at Huancayo and 30∘W of north at Bacabal during the month of December 1990. Number of solar flares that occurred on 30 December 1990 indicated the direction of solar flare related $\Delta H$ vector to be aligned along 5∘E of north at Huancayo and 28∘W of north at Bacabal. This is expected as the solar flare effects are due to the enhanced conductivity in the ionosphere. The SC at 2230 UT on 26 November 1990 produced a positive impulse in $\Delta X$ and negative impulse in $\Delta Y$ at Bacabal with $\Delta H$ vector aligned along 27∘W of north. At Huancayo the $\Delta H$ vector associated with SC is aligned along 8∘E of north, few degrees east to the alignment of the diurnal vector of H. The magnetic storm that followed the SC had a minimum Dst index of –150 nT. The corresponding storm time disturbance in $\Delta X$ at Huancayo as well as at Bacabal were about –250 nT but $\Delta Y$ at Bacabal was about +70 nT and very small at Huancayo, that give the alignment of the H vector due to ring current about 16∘W of north at Bacabal and almost along N–S at Huancayo. Thus alignment of the $\Delta H$ vector due to ring current at Bacabal is 14∘E of the mean direction of $\Delta H$ vector during December 1990. This is consistent with the direction of ring current dependent on the dipole declination at the ring current altitude which is about 5∘W of north over Bacabal and the deviation of declination due to the ring current during disturbed period given by the angle $(\psi-D)$.