Quiet ionospheric currents of the northern hemisphere derived from geomagnetic field records

Campbell, Wilbur H.; Schiffmacher, Edward R.

doi:10.1029/ja090ia07p06475

Cited by 59 publications

(41 citation statements)

References 15 publications

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“…The difference between the values of the northern and southern foci indicates the total current intensity, which is about 300 kA, for the summer season. This is very high, when compared with the summer current intensities of other global regions (Malin and Gupta, 1977;Campbell and Schiffmacher, 1985). As observed in this study, Malin and Gupta (1977) also have reported a maximum intensity of current for Sq when its focus is located at mid-Pacific.…”

Section: Equivalent Ionospheric Source Current Systemssupporting

confidence: 62%

“…Compared with the position of Sq foci in the North American and European regions, the Sq focus in the northern hemisphere in the East Asian sector is situated at a relatively lower latitude (Campbell and Schiffmacher, 1985). The mid-latitude pre-noon focus vortex of current, though not clearly seen in winter (Fig.…”

Section: Westward Lag Of Sq Focusmentioning

confidence: 99%

“…The computed Fourier spectra of all the data sets have clearly resolved the required periodicities in the data, in the form of distinct peaks at 24-, 12-, 8-and 6-hour periods, respectively corresponding to Sq and its first three harmonics. Using the spherical harmonic analysis technique detailed by Campbell and Schiffmacher (1985), we have separated the Sq field into external and internal parts. Spherical harmonic Gauss coefficients have been calculated up to maximum degree 12 and order 4. ing to the northern (LNP) and the southern (WEP) (Wepia) hemispheres for E-season (see Fig.…”

Section: Data Processing and Fourier Analysismentioning

confidence: 99%

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On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

2014

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We have utilized solar quiet daily variation (Sq) data recorded at a network of temporary and permanent magnetic observatories, operated along the western Pacific coast, in the 210• Magnetic Meridian (MM) region, spanning both hemispheres. The selected data sets correspond to solar-quiet year 1996. We have determined the ionospheric source current systems for all three Lloyd's seasons prior to calculating the Sq-induction response. As the selected data sets encompass the whole range of the western Pacific, we studied the role of self-induction effect (SIE) of the ocean at 24-hr period of Sq on the induction response, following the theory developed by Rikitake (1960). Our calculations show a considerable influence of the SIE on the induction response at 24-hr period, implying that ignoring the SIE in induction studies in oceanic regions leads to erroneous interpretation of the results. We have observed a large regional bias in the derived induction response estimates along the 210• MM region. As the ocean effect also depends on the regional subsurface structure and its conductivity, we believe that in addition to the SIE, the bias in the estimated response functions could be due to the strong influence of the coupling of the electric currents induced in the ocean and the highly heterogeneous upper mantle that has resulted from the active lithospheric convergence between the Pacific and Philippine Sea plates all along the western Pacific. We interpret the derived induction responses in the light of the tectonic significance of the 210• MM region. We also discuss the well-defined seasonal differences in ionospheric source current systems by comparing them with those reported for the East Asian sector.

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Section: Equivalent Ionospheric Source Current Systemssupporting

confidence: 62%

Section: Westward Lag Of Sq Focusmentioning

confidence: 99%

Section: Data Processing and Fourier Analysismentioning

confidence: 99%

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On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

2014

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“…5b are those for the intermediate latitude. The HA daily variation at this intermediate latitude was obtained in a manner similar to that used by Campbell and Schi macher (1985). They stated that it is a reasonable expectation that in quiet times the average surface ®eld signatures of ionospheric source currents should change smoothly with latitude.…”

Section: Resultsmentioning

confidence: 99%

The development of a regional geomagnetic daily variation model using neural networks

Sutcliffe¹

2000

Ann. Geophys.

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Abstract. Global and regional geomagnetic ®eld models give the components of the geomagnetic ®eld as functions of position and epoch; most utilise a polynomial or Fourier series to map the input variables to the geomagnetic ®eld values. The only temporal variation generally catered for in these models is the long term secular variation. However, there is an increasing need amongst certain users for models able to provide shorter term temporal variations, such as the geomagnetic daily variation. In this study, for the ®rst time, arti®cial neural networks (ANNs) are utilised to develop a geomagnetic daily variation model. The model developed is for the southern African region; however, the method used could be applied to any other region or even globally. Besides local time and latitude, input variables considered in the daily variation model are season, sunspot number, and degree of geomagnetic activity. The ANN modelling of the geomagnetic daily variation is found to give results very similar to those obtained by the synthesis of harmonic coe cients which have been computed by the more traditional harmonic analysis of the daily variation.

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“…The position of Sq currents was affected by the position of the geographic and geomagnetic poles with respect to these regions (Campbell and Schiffmacher, 1985). In the African sector of the Northern Hemisphere at Tamanrasset and M'bour (row 11, columns 2, 3), the Y morning maximum, in winter, is very small or disappears: this was previously observed on magnetic data by Van Sabben (1964), Mayaud (1965b) and also on incoherent scatter sounder data by Mazaudier and Venkateswaran (1985).…”

Section: Discussionmentioning

confidence: 99%

Sq field characteristics at Phu Thuy, Vietnam, during solar cycle 23: comparisons with Sq field in other longitude sectors

2011

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Abstract. Quiet days variations in the Earth's magnetic field (the Sq current system) are compared and contrasted for the Asian, African and American sectors using a new dataset from Vietnam. This is the first presentation of the variation of the Earth's magnetic field (Sq), during the solar cycle 23, at Phu Thuy, Vietnam (geographic latitudes 21.03 • N and longitude: 105.95 • E). Phu Thuy observatory is located below the crest of the equatorial fountain in the Asian longitude sector of the Northern Hemisphere. The morphology of the Sq daily variation is presented as a function of solar cycle and seasons. The diurnal variation of Phu Thuy is compared to those obtained in different magnetic observatories over the world to highlight the characteristics of the Phu Thuy observations. In other longitude sectors we find different patterns.At Phu Thuy the solar cycle variation of the amplitude of the daily variation of the X component is correlated to the F.10.7 cm solar radiation (∼0.74). This correlation factor is greater than the correlation factor obtained in two observatories located at the same magnetic latitudes in other longitude sectors: at Tamanrasset in the African sector (∼0.42, geographic latitude ∼22.79) and San Juan in the American sector (∼0.03, geographic latitude ∼18.38).At Phu Thuy, the Sq field exhibits an equinoctial and a diurnal asymmetry:-The seasonal variation of the monthly mean of X component exhibits the well known semiannual pattern with 2 equinox maxima, but the X component is larger in spring than in autumn. Depending of the phase of the sunspot cycle, the maximum amplitude of the X component varies in spring from 30 nT to 75 nT and in autumn from 20 nT to 60 nT. The maximum amplitude of the X component exhibits roughly the same variation in bothCorrespondence to: H. Pham Thi Thu (hongnd76@yahoo.com) solstices, varying from about ∼20 nT to 50 nT, depending on the position into the solar cycle.-In all seasons, the mean equinoctial diurnal Y component has a morning maximum Larger than the afternoon minimum i.e. the equivalent current flow over a day is more southward than northward. During winter, the asymmetry is maximum, it erases the afternoon minimum. At the Gnangara observatory, in Asian Southern Hemisphere, the diurnal Y pattern is opposite and the current flow is more northward. It seems that in the Asian sector, the northern and southern Sq current cells both contribute strongly to the equatorial electrojet. The pattern is different in the African and American sectors where the northern Sq current cell contribution to the equatorial electrojet is smaller than the southern one. These observations can explain the unexpected maximum of amplitude of the equatorial electrojet observed in the Asian sector where the internal field is very large. During winter the Y component flow presents an anomaly, it is always southward during the whole day and there is no afternoon northward circulation.

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Quiet ionospheric currents of the northern hemisphere derived from geomagnetic field records

Cited by 59 publications

References 15 publications

On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

The development of a regional geomagnetic daily variation model using neural networks

Sq field characteristics at Phu Thuy, Vietnam, during solar cycle 23: comparisons with Sq field in other longitude sectors

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