World-wide morphology of day-to-day variability of Sq

Schlapp, D. M.

doi:10.1016/0021-9169(68)90096-2

Cited by 45 publications

(27 citation statements)

References 8 publications

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“…Given the distribution of current and the magnetic field resulting therefrom, further increases in intensity such as we are discussing here are likely to arise from an increase in electron density or wind intensity among other factors. Such increases from electron density or wind are likely to cover the whole region of SCHLAPP (1968) found that the day-to-day variations of Sq intensity "were a local phenomenon, being correlated over distances of the order of 1000 to 2000 km;" but HIBBERD (1981) and BRIGGS (1984) found that they were correlated even between two hemispheres. Thus, these should lead to a general increase in the conductivity in the whole region.…”

Section: Resultsmentioning

confidence: 99%

Effect of equatorial electrojet intensity on its landmark distances.

Onwumechili

Agu

Ozoemena

1989

J. geomagn. geoelec

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From the correlations of seven landmark distances, s, of the equatorial electrojet with its peak eastward current intensity Jo and its space gradient dJo/ ds, we find that the entire electrojet current system, with its magnetic field, tends to contract; consequently, the current and magnetic field foci, as well as contours of equal current intensity or of equal magnetic field, move towards the magnetic dip equator as the electrojet intensity increases. Furthermore, for a given increase in intensity, the greater the landmark distance the greater its contraction; and for movement of unit distance, the nearer the position to the dip equator the greater the increase in intensity required. Three causes which possibly contribute to the contraction are briefly discussed.

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Section: Resultsmentioning

confidence: 99%

Effect of equatorial electrojet intensity on its landmark distances.

Onwumechili

Agu

Ozoemena

1989

J. geomagn. geoelec

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“…In many cases, poor correlation was found (Osborne 1963(Osborne , 1966(Osborne , 1968Ogbuehi et al 1967;Schlapp 1968;Mann and Schlapp 1988;Manoj et al 2006;Abdul Hamid et al 2014). The results were often taken as evidence that the equatorial electrojet is not a simple enhancement of Sq currents and hence other driving mechanisms exist for the EEJ.…”

Section: Sq-eej Relationshipmentioning

confidence: 99%

“…The following are some examples of the nighttime baseline in the literature: Schlapp (1968) used the hourly value nearest to local midnight as the baseline; and Bolaji et al (2015) used the average value for the two hours starting from local midnight; Siddiqui et al (2015a) used two hours before midnight and two hours after midnight; Pham Thi Thu et al (2011) used one hour before midnight and two hours after midnight; El Hawary et al (2012) used one hour before midnight and three hours after midnight; Takeda (1984), Malin and Winch (1996), Yamazaki et al (2012b) used the five hours nearest to local midnight.…”

Section: Determination Of Baselinesmentioning

confidence: 99%

“…The dayto-day variation of Sq is often "random-like", and the mechanism is not well understood. The correlation of Sq at a pair of stations decreases with increasing distance between the two stations, reaching 0.5 for separations of about 40°in longitude and 15°in latitude (Schlapp 1968;Greener and Schlapp 1979). In order to illustrate the nature of the day-to-day variability of Sq, we have analyzed the horizontal-component (H ) geomagnetic field obtained from the Indian longitude sector.…”

Section: Irregular Changesmentioning

confidence: 99%

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Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

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A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m 2 flowing on the sunlit side of the Eregion ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the nonspecialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

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“…However the daily ranges of H at different latitudes were found not to correlate well (Osborne, 1966;Schlapp, 1968;Kane, 1971). James et al (1996) has shown that the correlation of ΔH at an equatorial station, Trivandrum, with ΔH at other stations in India decreases with increasing latitude.…”

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confidence: 98%

Equatorial electrojet studies from rocket and ground measurements

2014

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Combining the data of in-situ measurements of ionospheric current, J m by rocket-borne instruments and the ground based geomagnetic H field close to the magnetic equator a linear relation has been found between the peak current density J m and the daily range of H, (R H ). This relationship has been used to convert long series of R H data into J m . Combining J m and the E-region peak electron density N m , the electron velocity in the ionosphere, V E has been calculated. It is shown that after all corrections are made of the solar zenith angle variations, the ionospheric current as well as electron drift in American and Indian sectors show strong equinoctial maxima, the mean values of both the parameters are larger at American than in Indian sector. The solar cycle variation of the electrojet current is primarily due to the variations of N m E, and not due to the variations of electric field. The diurnal variation of the electric field with peak at 09-10 LT interacting with noon peak of N m E making ΔH to peak at an hour earlier than noon. It is stressed to realise the importance of electric field in diurnal, seasonal and longitudinal variations of the equatorial electrojet current.at Yauca, Chimbote, Chiclayo and Talara covered the whole width of the EEJ. In India new observatories were established at Trivandrum and Annamalainagar. EEJ observatories were organised at Koror, Jarvis and Ibadan. Table 1 gives the coordinates and the magnetic field parameters of some of these observatories.Chapman and Rajarao (1965) showed that the seasonal variations of the range in H as well as in Z at the equatorial electrojet stations have strong semi-annual wave with maxima during equinoctial months. Analysing the lunar tides in the critical frequency of the F 2 layer, f o F 2 , at equatorial stations in Peru and in India during the IGY period, Rastogi (1962a) predicted that the equatorial electrojet current strength must be stronger in Peru than in India. Later using the geomagnetic data from the equatorial observatories during IGY, Rastogi (1962b) confirmed that the electrojet current is indeed stronger in Peru than in India. The strength of the electrojet current was shown to vary roughly inversally to the background mean value of the geomagnetic field H at the station. It was suggested that the electrical conductivity over the magnetic equator is inversally proportional to the strength of the H field.If equatorial electrojet is a part of the global S q current system, modified close to the magnetic equator, the day to day variations in the strength of the equatorial electrojet should correlate with the corresponding variations in the strength of the S q currents at low latitudes outside the electrojet belt. However the daily ranges of H at different latitudes were found not to correlate well (Osborne, 1966;Schlapp, 1968;Kane, 1971). James et al. (1996) has shown that the correlation of ΔH at an equatorial station, Trivandrum, with ΔH at other stations in India decreases with increasing latitude. It becomes almost zero ar...

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World-wide morphology of day-to-day variability of Sq

Cited by 45 publications

References 8 publications

Effect of equatorial electrojet intensity on its landmark distances.

Effect of equatorial electrojet intensity on its landmark distances.

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

Equatorial electrojet studies from rocket and ground measurements

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