ANGEO Annales Geophysicae ANGEO 1432-0576 Copernicus GmbH Göttingen, Germany 10.5194/angeo-28-2097-2010 Duskside F-region dynamo currents: its relationship with prereversal enhancement of vertical plasma drift Park J. 1 2 Lühr H. 1 Fejer B. G. 3 Min K. W. 2 GFZ, German Research Center for Geosciences, Germany Department of Physics, Korea Advanced Institute of Science and Technology, Korea Center for Atmospheric and Space Science, Utah State University, USA 12 11 2010 28 11 2097 2101 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.ann-geophys.net/28/2097/2010/angeo-28-2097-2010.html The full text article is available as a PDF file from http://www.ann-geophys.net/28/2097/2010/angeo-28-2097-2010.pdf

From magnetic field observations by CHAMP we estimate F-region dynamo current densities near the sunset terminator during solar maximum years from 2001 to 2002. The dynamo currents are compared with the pre-reversal enhancement (PRE) of vertical plasma drift as observed by ROCSAT-1. The seasonal-longitudinal variation of PRE can be largely related to the F-region dynamo current density, with the correlation coefficient reaching 0.74. The correlation can be further improved if we consider a zonal gradient of the E-region Pedersen conductivity, which also depends on season and longitude. It is widely accepted that the F-region dynamo drives PRE near sunset. For the first time, our observations provide confirmation for the close relationship between the F-region dynamo current density and PRE.

 References Eccles, J. V.: A simple model of low-latitude electric fields, J. Geophys. Res., 103(A11), 26699–26708, 1998a. Eccles, J.: Modeling investigation of the evening prereversal enhancement of the zonal electric field in the equatorial ionosphere, J. Geophys. Res., 103(A11), 26709–26719, 1998b. Farley, D. T., Bonelli, E., Fejer, B. G., and Larsen, M. F.: The Prereversal Enhancement of the Zonal Electric Field in the Equatorial Ionosphere, J. Geophys. Res., 91(A12), 13723–13728, 1986. Fejer, B. G., de Paula, E. R., Batista, I. S., Bonelli, E., and Woodman, R. F.: Equatorial F Region Vertical Plasma Drifts During Solar Maxima, J. Geophys. Res., 94(A9), 12049–12054, 1989. Fejer, B. G., Jensen, J. W., and Su, S.-Y.: Quiet time equatorial F region vertical plasma drift model derived from ROCSAT-1 observations, J. Geophys. Res., 113, A05304, doi:10.1029/2007JA012801, 2008. Heelis, R. A.: Electrodynamics in the low and middle latitude ionosphere: a tutorial, J. Atmos. Solar Terr. Phys., 66, 825–838, 2004. Kelley, M. C.: The Earth's Ionosphere: Plasma Physics and Electrodynamics, 2nd edition, Elsevier, London, 2009. Liu, H., Lühr, H., Watanabe, S., Köhler, W., Henize, V., and Visser, P.: Zonal winds in the equatorial upper thermosphere: Decomposing the solar flux, geomagnetic activity, and seasonal dependencies, J. Geophys. Res., 111, A07307, doi:10.1029/2005JA011415, 2006. Liu, H., Watanabe, S., and Kondo, T.: Fast thermospheric wind jet at the Earth's dip equator, Geophys. Res. Lett., 36, L08103, doi:10.1029/2009GL037377, 2009. Lühr, H. and Maus, S.: Direct observation of the F region dynamo currents and the spatial structure of the EEJ by CHAMP, Geophys. Res. Lett., 33, L24102, doi:10.1029/2006GL028374, 2006. Maeda, H., Iyemori, T., Araki, T., and Kamei, T.: New evidence of a meridional current system in the equatorial ionosphere, Geophys. Res. Lett., 9(4), 337–340, 1982. Murphy, J. A. and Heelis, R. A.: Implications of the Relationship Between Electromagnetic Drift Components at Mid and Low Latitudes, Planet. Space Sci., 34, 645–652, 1986. Park, J., Lühr, H., and Min, K. W.: Characteristics of F-region dynamo currents deduced from CHAMP magnetic field measurements, J. Geophys. Res., 115, A10302, doi:10.1029/2010JA015604, 2010. Pingree, J. E. and Fejer, B. G.: On the Height Variation of the Equatorial F Region Vertical Plasma Drifts, J. Geophys. Res., 92(A5), 4763–4766, 1987. Scherliess, L. and Fejer, B.: Radar and satellite global equatorial F region vertical drift model, J. Geophys. Res., 104(A4), 6829–6842, 1999. Takeda, M. and Maeda, H.: F-region dynamo in the evening. interpretation of equatorial D anomaly found by Magsat, J. Atmos. Terr. Phys., 45, 401–408, 1983. Tsunoda, R.: Control of the Seasonal and Longitudinal Occurrence of Equatorial Scintillations by the Longitudinal Gradient in Integrated E Region Pedersen Conductivity, J. Geophys. Res., 90(A1), 447–456, 1985.