An Interpretation of the Induction Arrows at Indian Stations

Srivastava, Bipin K.; Abbas, Habiba

doi:10.5636/jgg.32.supplement1_si187

Cited by 11 publications

(11 citation statements)

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“…Fukushima (1993) has shown that the daily variation of Z field at Koror followed the temporal gradient in H field and hence concluded that Z was affected by the induction effects due to ocean currents. The abnormal variation of Z at Trivandrum has been attributed to the increase electromagnetic induction due to ocean currents by Nityananda et al (1977) and Srivastava and Abbas (1978); and due to conducting channel between India and Sri Lanka by Rajaram et al (1979). From the present curves of Sq (Z ) it is to be noted that whatever may be reasons for induction, the effect is present at Trivandrum (by abnormal diurnal variation of the element) and to a lesser extent at Ettaiyapuram.…”

Section: Observationsmentioning

confidence: 70%

Solar flare effects on the geomagnetic elements during normal and counter electrojet periods

et al. 2014

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The paper describes the study of solar flare effects (sfe) on horizontal (H ), eastward (Y ) and vertical (Z ) components of the geomagnetic field at the Indo-USSR chain of magnetic observatories extending from the magnetic latitudes 0• to 45• N, a network not available any where else in the world. Events are selected when strong, normal and reversed (counter) equatorial electrojet are in existence as well as when only a partial counter electrojet is present.During a strong and normal electrojet event time, sfe consists of a positive impulse in H at all stations, the amplitude of H following the latitudinal variation similar to that of the quiet day monthly mean, Sq (H ). The sfe in Y is negative at all the stations. Sfe in Z shows positive impulse at the four-electrojet stations and negative at other stations. During a counter electrojet period the effect of solar flare on H field is negative impulse at electrojet stations, positive at low latitude and again negative at stations north of Sq focus. Sfe in Y is small at all the equatorial and negative at higher latitude stations. However, sfe (Z ) is negative at the equatorial latitudes.During a partial counter electrojet period the observed effect is the combination of an increase of the planetary current component and the decrease of the electrojet component, giving rise to a negative impulse in H at equatorial stations and a positive impulse in H , increasing with increasing distance from the equator. These results are presented and discussed.

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Section: Observationsmentioning

confidence: 70%

Solar flare effects on the geomagnetic elements during normal and counter electrojet periods

et al. 2014

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“…This anomaly was interpreted by Srivastava and Sankar Narayan (1970) in terms of ocean eects and electrical conductivity anomalies in the upper mantle at depths of 200±800 km. Srivastava and Abbas (1978) studied the induction arrows (Wiese vectors) for the nighttime SSCs. They found unusually large induction arrows at Trivandrum indicative of very strong induced current concentrations near and along the coast and the continental shelf and¯ow from north to south along the east coast.…”

Section: Discussionmentioning

confidence: 99%

Signatures of storm sudden commencements in geomagnetic H, Y and Z fields at Indian observatories during 1958−1992

Rastogi

1999

Ann. Geophys.

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Abstract. The work describes an intensive study of storm sudden commencement (SSC) impulses in horizontal (H), eastward (Y) and vertical (Z) ®elds at four Indian geomagnetic observatories between 1958±1992. The midday maximum of DH has been shown to exist even at the low-latitude station Alibag which is outside the equatorial electrojet belt, suggesting that SSC is associated with an eastward electric ®eld at equatorial and low latitudes. The impulses in Y ®eld are shown to be linearly and inversely related to DH at Annamalainagar and Alibag. The average SC disturbance vector is shown to be about 10±20°W of the geomagnetic meridian. The local time variation of the angle is more westerly during dusk hours in summer and around dawn in the winter months. This clearly suggests an eect of the orientation of shock front plane of the solar plasma with respect to the geomagnetic meridian. The DZ at SSC have a positive impulse as in DH. The ratio of DZ/DH are abnormally large exceeding 1.0 in most of the cases at Trivandrum. The latitudinal variation of DZ shows a tendency towards a minimum over the equator during the nighttime hours. These eects are explained as (1) resulting from the electromagnetic induction eects due to the equatorial electrojet current in the subsurface conducting layers between India and Sri Lanka, due to channelling of ocean currents through the Palk Strait and (2) due to the concentration of induced currents over extended latitude zones towards the conducting graben between India and Sri Lanka just south of Trivandrum.

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“…In the region of the southern peninsular tip of India, the induction arrows ( Figure 2) are very large at the two coastal stations of Annamalainagar and Trivandrum as well as the inland station of Kodaikanal, indicating higher oceanic conductivity (Srivastava and Abbas, 1980). Not only are the Z variations anomalously large in the electrojet region, the HandD variations are also anomalous at Annamalainagar and Trivandrum (Srivastava and Sanker Narayan, 1969;Nityananda et al, 1977).…”

Section: The Coast Effectmentioning

confidence: 98%

“…The determinations of directions of rapid geomagnetic changes like bays at Alibag, Annamalainagar and Trivandrum by Srinivasan and Sastri (1964) and at Hyderabad by Srivastava et al (1968), following Parkinson's method (1959), showed that Parkinson's 'preferred plane' could not be estimated at these low latitude stations due to small D changes in the equatorial electrojet region and its vicinity. Subsequent computations based on transfer function and Wiese vector techniques respectively, gave the induction arrows at these stations (Nityananda et al, 1975;Srivastava and Abbas, 1980), which revised the Parkinson vector determiRations made earlier. Srivastava et al ( , 1974a Srivastava et al, 1974a).…”

Section: The Coast Effectmentioning

confidence: 99%

“…geomagnetic induction anomaly in short-period events and daily variation data respectively and established the existence of a coastal effect at Alibag. Later, Srivastava and Sanker Narayan (1967, 1969, Srivastava et al (1974a, b) and Srivastava and Prasad (1974), Nityananda et al (1975Nityananda et al ( , 1977Nityananda et al ( , 1981, Rajagopal et al (1976), Singh et al (1977), Srivastava (1977Srivastava ( , 1981, Rajaram et al (1979), Agarwal et al (1979) and Srivastava and Abbas (1980) investigated various aspects of geomagnetic induction anomalies in India. Based on detailed magnetometer array studies in India, exhaustive results have been reported by Lilley et al (1981), Thakur et al (1981) and Arora et al (1982).…”

Section: Geophysical Surveysmentioning

confidence: 99%

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Geomagnetic induction anomalies in India in relation to geology

Srivastava

Prasad

1982

Geophysical Surveys

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Abstract. Geomagnetic induction anomalies identified in India during the last fifteen years are discussed with emphasis on geology. The effects on both short period (SSCs and bays) and long period (Sq and Dst) geomagnetic variations are summarized. The induction effects observed in the southern tip of peninsular India are highly complex due to the coastal effect, to crustal and upper mantle conductivity anomalies between India and Sri Lanka and to the daytime equatorial electrojet. Further complications arise from the existence of a conductive step structure along the coastline at the Moho boundary and a 'graben' in the Palk Strait.The reversed coast effect in the Z-variation identified at Alibag situated on the Deccan Traps is accounted for by the remanent magnetization of the Deccan lavas, their thickness and the underlying conductive strucutres.Induced currents have been found to be channelled through conductive structures beneath the Aravallis along its strike following a path transverse to the Himalaya. An asthenospheric upwelling beneath the Aravallis has also been noted. Conductive step structures have also been invoked on the southern and the northern flanks of the Pamir-Himalaya with east-west current channelling at the Moho boundary.

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An Interpretation of the Induction Arrows at Indian Stations

Cited by 11 publications

References 10 publications

Solar flare effects on the geomagnetic elements during normal and counter electrojet periods

Solar flare effects on the geomagnetic elements during normal and counter electrojet periods

Signatures of storm sudden commencements in geomagnetic H, Y and Z fields at Indian observatories during 1958−1992

Geomagnetic induction anomalies in India in relation to geology

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