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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 30, issue 1
Ann. Geophys., 30, 131–141, 2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 30, 131–141, 2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 13 Jan 2012

Regular paper | 13 Jan 2012

Storm-time longitudinally propagating asymmetric modes at low latitudes

A. K. Singh1, A. K. Sinha1, R. Rajaram1,2, and B. M. Pathan1 A. K. Singh et al.
  • 1Indian Institute of Geomagnetism, Kalamboli Highway, New Panvel (W), Navi Mumbai – 410218, Maharashtra, India
  • 2Micro Technologies (India) Ltd., MIDC, Mahape, Navi Mumbai – 400709, Maharashtra, India

Abstract. The westward flowing toroidal ring current at about 2–7 RE in the Earth's equatorial plane consists of symmetric and asymmetric parts. Zonal mean of H disturbances from longitudinally distributed low latitude stations represents the symmetric contribution, whereas departure from the zonal mean gives local time dependent asymmetric component at each of the stations. Through a standard analysis of closely spaced low latitude geomagnetic data we demonstrate 24 h periodicity in the asymmetric component of the storm-time ring current, which is related to the changing local time due to rotation of the Earth. Detailed examination of shorter period oscillations, when observed globally, often show westward propagating modes. Eastward propagating mode was also observed in one case. Based on satellite and radar observations covering a narrow longitude region, westward and eastward propagating modes had been reported in earlier studies. In this study, we report that similar propagating modes which are available on global scale, can be identified using ground-based magnetometer data. These globally propagating modes, observed from ground-based studies, find obvious practical application in diagnostics of the magnetosphere, especially the ring current region. Simultaneous use of satellite and ground-based data should establish the morphology of such modes.

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