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Full-Text Articles in Physics

Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert Dec 2003

Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert

Bela G. Fejer

[1] Low-latitude ionospheric electric fields and currents are often strongly disturbed during periods of enhanced geomagnetic activity. These perturbations can last for several hours after geomagnetic quieting. We use incoherent scatter radar measurements from Jicamarca and Arecibo during 19–21 October 1998 to study, for the first time, the low-latitude disturbance electric fields during the recovery phase of a large magnetic storm. On 19 October the Jicamarca data showed initially large and short-lived (time scale of about 10–20 min) upward and westward drift perturbations in the early afternoon sector, due to the penetration of strong magnetospheric electric fields probably ...


Equatorial Counterelectrojetsduring Substorms, T. Kikuchi, K. Hashimoto, T. I. Kitamura, H. Tachihara, Bela G. Fejer Nov 2003

Equatorial Counterelectrojetsduring Substorms, T. Kikuchi, K. Hashimoto, T. I. Kitamura, H. Tachihara, Bela G. Fejer

Bela G. Fejer

[1] Equatorial counterelectrojet (CEJ) events are analyzed in association with changes in the interplanetary magnetic field (IMF), polar cap potential (PCP), and electric field measured in the equatorial ionosphere. In one event on 16 July 1995, the equatorial CEJ was observed at the afternoon dip equator during the recovery phase of the substorm when the IMF turned northward. Rapid decreases in the PCP and in the auroral electrojet occurred simultaneously with the equatorial CEJ, suggesting instantaneous equatorward penetration of the rapid decrease in the electric field associated with the region 1 field-aligned currents (R1 FACs) under the condition of a ...


Three-Dimensional Nonlinear Evolution Ofequatorial Ionospheric Spread-F Bubbles, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer Aug 2003

Three-Dimensional Nonlinear Evolution Ofequatorial Ionospheric Spread-F Bubbles, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer

Bela G. Fejer

[1] Using numerical simulation techniques, we present the first study of the three-dimensional nonlinear evolution of an equatorial spread-F bubble. The background ionosphere used to initialize the bubble evolution is computed using a time-dependent first-principles equatorial plasma fountain model together with a prereversal enhancement vertical drift model. We find that finite parallel conductivity effects slow down both the linear and nonlinear bubble evolution compared to the two-dimensional evolution. In addition we find that bubble-like structures with extremely sharp density gradients can be generated off the equator at equatorial anomaly latitudes in agreement with recent observations.


Climatology And Latitudinal Gradients Of Quiet-Timethermospheric Neutral Winds Over Millstone Hill From Fabry-Perot Interferometermeasurements, J. T. Emmert, Bela G. Fejer, D. P. Sipler Jan 2003

Climatology And Latitudinal Gradients Of Quiet-Timethermospheric Neutral Winds Over Millstone Hill From Fabry-Perot Interferometermeasurements, J. T. Emmert, Bela G. Fejer, D. P. Sipler

Bela G. Fejer

[1] Midlatitude nighttime thermospheric neutral winds are strongly dependent on season, solar activity, and latitude. We use an extensive database of wind measurements made during 1989–2001 by the Millstone Hill Fabry-Perot interferometer to study the detailed climatology of quiet time neutral winds near an altitude of 250 km. To facilitate the analysis of these data, we develop a local time, day-of-year, solar flux, and latitude-dependent empirical model, with the latitude dependence obtained by considering north looking and south looking observations separately. Our results show that the zonal winds are predominantly eastward after dusk and westward before dawn, with the ...