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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 1
Ann. Geophys., 27, 427-439, 2009
https://doi.org/10.5194/angeo-27-427-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: 12th International Symposium on Equatorial Aeronomy...

Ann. Geophys., 27, 427-439, 2009
https://doi.org/10.5194/angeo-27-427-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  23 Jan 2009

23 Jan 2009

Topside measurements at Jicamarca during solar minimum

D. L. Hysell1, J. L. Chau2, and J. D. Huba3 D. L. Hysell et al.
  • 1Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA
  • 2Radio Observatorio de Jicamarca, Instituto Geofísico del Perú, Lima
  • 3Plasma Physics Division, Naval Research Laboratory, Washington, D.C., USA

Abstract. Long-pulse topside radar data acquired at Jicamarca and processed using full-profile analysis are compared to data processed using more conventional, range-gated approaches and with analytic and computational models. The salient features of the topside observations include a dramatic increase in the Te/Ti temperature ratio above the F peak at dawn and a local minimum in the topside plasma temperature in the afternoon. The hydrogen ion fraction was found to exhibit hyperbolic tangent-shaped profiles that become shallow (gradually changing) above the O+-H+ transition height during the day. The profile shapes are generally consistent with diffusive equilibrium, although shallowing to the point of changes in inflection can only be accounted for by taking the effects of E×B drifts and meridional winds into account. The SAMI2 model demonstrates this as well as the substantial effect that drifts and winds can have on topside temperatures. Significant quiet-time variability in the topside composition and temperatures may be due to variability in the mechanical forcing. Correlations between topside measurements and magnetometer data at Jicamarca support this hypothesis.

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