Geomagnetically quiet day ionospheric currents over the Indian sector—I. Worldwide part of Sq currents

Onwumechili, C. Agodi; Oko, S.O.; Ezema, P.O.

doi:10.1016/0021-9169(95)00055-0

Cited by 8 publications

(10 citation statements)

References 27 publications

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“…The results of Hasegawa [] and Onwumechili et al . [] did not support the suggestions of Butcher and Brown [] and Stening et al . [].…”

Section: Discussionmentioning

confidence: 68%

“…Hasegawa [], Onwumechili et al . [], and Butcher and Brown [] attributed the day‐to‐day shift in the position of the S q focus to the ionospheric dynamo variability, which result in redistribution and skewing of the S q current system. On the reduction of the equatorial electrojet amplitude at ABB, Stening et al .…”

Section: Discussionmentioning

confidence: 99%

“…Our results further support the results of Hasegawa [], Onwumechili et al . [], and Stening et al . [, ] that the seasonal S q focus is inconsistent, because it changes hour by hour and day by day across latitudes.…”

Section: Discussionmentioning

confidence: 99%

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Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

et al. 2015

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We have used chains of Magnetic Data Acquisition System (MAGDAS) magnetometer records of the horizontal (H) and vertical (Z) magnetic field intensities during September 2008 to August 2009 (year of deep minimum) across Africa to study their variability during the quietest international days, which coincidently associated with the sudden stratospheric warming (SSW) event in January 2009. This selection of the most international quiet days is indicative of 80% that are strongly associated with days when unusually strong and prolonged sudden SSW event occurs in January 2009. Interestingly, in January, a significant magnitude depletion of solar quiet (S q ) equivalent current was observed near noon hours around the magnetic equator (Addis Ababa, ABB) compared to any other months along with a consistent significantly reduced value across the Northern Hemisphere and moderate decrease at the Southern Hemisphere. Also, we found that Nairobi and Dar es Salaam at the Southern Hemisphere, which are close to ABB (dip equator), are strongly prone to westward electric field compared to the magnetic equator and Khartoum at the Northern Hemisphere. Significant negative values of MS q (Z) magnitudes observed near noon hours at Hermanus indicate the presence of induced currents that suggest ocean effects along with reversal to significant positive values in the afternoon, which subsided before 1800 LT in almost all the months, indicate stronger influence of ionospheric currents. On seasonal variability of S q (H), a slight depression at ABB during September equinox is one of the evidences of seasonal S q focus shift. Latitudinal variability of S q near-noon hours was also investigated.

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“…The results of Hasegawa [] and Onwumechili et al . [] did not support the suggestions of Butcher and Brown [] and Stening et al . [].…”

Section: Discussionmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 99%

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Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

et al. 2015

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“…The justification of the slice observatory chain (75øE geographic) and an empirical analytical method [Campbell, 1997], wherein the longitude coordinates and model based entirely on the latitudinal variation of H. While any time coordinates are regarded as inter-changeable, is based on the analytic empirical fit based only on H variations could have been implicit assumption of such a scenario. adopted, we use here the model of Onwumechili [1967] to obtain The picture of Earth rotating under a fixed current system in the main Sq parameters and its temporal and longitudinal space is conceptually elegant. It is also useful in analysis of data variations.…”

Section: Introductionmentioning

confidence: 99%

“…It is also useful in analysis of data variations. This empirical model is known to reproduce, in a from a single latitudinal chain of observatories, as it allows for use quantitative manner, the salient features of the Sq current system of the global spherical harmonic expansion, through the use of [Onwumechili, 1967;Arora et al, 1993;Onwumechili et al, 1996]. local time as a proxy for longitude [Campbell et al, 1993].…”

Section: Introductionmentioning

confidence: 99%

A test for the stationariness of the S_q current system

Patil¹,

Rajaram²

2001

J. Geophys. Res.

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Abstract. We have shown here that a single chain of geomagnetic observatories, located at a fixed longitude, can provide the longitudinal gradients in the strength of the current system. The empirical model of Onwumechili [ 1967] for low latitude Sq currents, which is based on the diurnal variation of the horizontal component of the geomagnetic field, has been augmented to reproduce D variations that are consistent with the curl-free nature of the surface magnetic field variations. It is then possible to use variations in declination to obtain the longitudinal gradients in the strength of the current system using data from a single longitude zone. The model is applied to the data from the Indian zone. A clear linear relation between the longitudinal and temporal variations of the strength of the current system is brought out. The result appears to indicate that, at least locally, in the 75øE longitude sector, the current system is stationary and the time dependence can be used to replicate the longitudinal variations.

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Geomagnetically quiet day ionospheric currents over the Indian sector—II. Equatorial electrojet currents

Oko

Onwumechili

Ezema

1996

Journal of Atmospheric and Terrestrial Physics

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Geomagnetically quiet day ionospheric currents over the Indian sector—I. Worldwide part of Sq currents

Cited by 8 publications

References 27 publications

Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

A test for the stationariness of the S_q current system

Geomagnetically quiet day ionospheric currents over the Indian sector—II. Equatorial electrojet currents

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Geomagnetically quiet day ionospheric currents over the Indian sector—I. Worldwide part of Sq currents

Cited by 8 publications

References 27 publications

Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

A test for the stationariness of the Sq current system

Geomagnetically quiet day ionospheric currents over the Indian sector—II. Equatorial electrojet currents

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A test for the stationariness of the S_q current system