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Full-Text Articles in Physical Sciences and Mathematics
Average Nighttime F Region Disturbance Neutral Winds Measured By Windi Uars: Initial Results, J. T. Emmert, Bela G. Fejer, G. G. Shepard, B. H. Solheim
Average Nighttime F Region Disturbance Neutral Winds Measured By Windi Uars: Initial Results, J. T. Emmert, Bela G. Fejer, G. G. Shepard, B. H. Solheim
Bela G. Fejer
[1] We use low- and mid-latitude wind data from the Wind Imaging Interferometer (WINDII) on board the Upper Atmosphere Research Satellite (UARS) to study the average response of nighttime upper thermospheric winds to geomagnetic activity. We calculate perturbation winds in magnetic coordinates and analyze them as a function of magnetic local time, latitude, geomagnetic activity, and solar EUV flux. The nighttime zonal disturbance winds are predominately westward, with the strongest effects extending from dusk at 70° to midnight at 45°. Westward disturbance winds are also observed throughout most of the night at low latitudes, where they change to eastward at …
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
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 strongest …
Climatology And Storm Time Dependence Ofnighttime Thermospheric Neutral Winds Over Millstone Hill, Bela G. Fejer, J. T. Emmert, D. P. Sipler
Climatology And Storm Time Dependence Ofnighttime Thermospheric Neutral Winds Over Millstone Hill, Bela G. Fejer, J. T. Emmert, D. P. Sipler
Bela G. Fejer
[1] We use 630.0 nm nightglow Fabry-Perot measurements over Millstone Hill from 1989–1999 to study the climatology and storm time dependence of the midlatitude thermospheric winds. Our quiet time wind patterns are consistent with results from earlier studies. We determine the perturbation winds by subtracting from each measurement the corresponding quiet time averages. The climatological zonal disturbance winds are largely independent of season and solar flux and show large early night westward and small late-night eastward winds similar to disturbance ion drifts. The meridional perturbation winds vary strongly with season and solar flux. When the solar flux is low, the …
Altitude Dependence Of Middleand Low-Latitude Thermospheric Disturbance Winds Measured By Windii, J. T. Emmert, Bela G. Fejer, G. G. Shepard, B. H. Solheim
Altitude Dependence Of Middleand Low-Latitude Thermospheric Disturbance Winds Measured By Windii, J. T. Emmert, Bela G. Fejer, G. G. Shepard, B. H. Solheim
Bela G. Fejer
[1] Thermospheric neutral winds exhibit strong altitudinal and latitudinal variation during geomagnetically quiet and active times. We use daytime middle and low-latitude neutral winds measured by the Wind Imaging Interferometer (WINDII) instrument on board the Upper Atmosphere Research Satellite (UARS) over the 90–275 km height range to study the altitude and season dependent climatology of disturbance winds (i.e., with quiet time patterns removed) in magnetic coordinates. The daytime perturbations winds are generally equatorward and westward and decrease toward the magnetic equator. Both the zonal and meridional components decrease sharply below 120 km and are essentially insignificant below 100 km. The …
Climatology Of Mid- And Low-Latitude F Region Disturbance Winds Measured By Windii, J. T. Emmert, Bela G. Fejer, C. G. Fesen, G. G. Shepherd, B. H. Solheim
Climatology Of Mid- And Low-Latitude F Region Disturbance Winds Measured By Windii, J. T. Emmert, Bela G. Fejer, C. G. Fesen, G. G. Shepherd, B. H. Solheim
Bela G. Fejer
No abstract provided.
Average Daytime Disturbanceneutral Winds Measured By Uars: Initial Results, Bela G. Fejer, J. T. Emmert, G. G. Shepard, B. H. Solheim
Average Daytime Disturbanceneutral Winds Measured By Uars: Initial Results, Bela G. Fejer, J. T. Emmert, G. G. Shepard, B. H. Solheim
Bela G. Fejer
Thermospheric neutral winds play important roles on the dynamics of the upper atmosphere. We use extensive F region zonal and meridional wind data measured by the Wind Imaging Interferometer (WINDII) instrument on board the Upper Atmosphere Research Satellite (UARS) to study the mid-and low-latitude daytime average perturbation winds during magnetically disturbed periods. We have determined the perturbation winds by subtracting the quiet time wind values along the satellite orbits. Our data indicate large changes in the latitudinal profiles of both the zonal and meridional disturbance winds from morning to afternoon hours. The early morning zonal disturbance winds are eastward near …
Equatorial And Low Latitude Thermospheric Winds: Measured Quiet Time Variations With Season And Solar Flux From 1980 To 1990, M. A. Biondi, S. Y. Sazykin, Bela G. Fejer, J. W. Meriwether, C. G. Fesen
Equatorial And Low Latitude Thermospheric Winds: Measured Quiet Time Variations With Season And Solar Flux From 1980 To 1990, M. A. Biondi, S. Y. Sazykin, Bela G. Fejer, J. W. Meriwether, C. G. Fesen
Bela G. Fejer
Thermospheric winds have been systematically determined at Arequipa, Peru, and Arecibo, Puerto Rico, from Fabry-Perot interferometer measurements of Doppler shifts in the nightglow 630 nm line. The wind databases (1983 – 1990 at Arequipa and 1980 – 1990 at Arecibo) have been edited to eliminate measurements during geomagnetically disturbed conditions, then sorted by season and solar flux level. Following this, they were averaged to obtain the climatological behavior of the nighttime wind variations at the two locations. A new averaging technique, multivariate regression analysis, has been applied to the data, and the results compared to our prior binning averages. The …
Interaction Of The Zonalwinds With The Equatorial Midnight Pressure Bulge In The Earth's Thermosphere: Empiricalevidence Of Momentum Balance, F. A. Herrero, H. G. Mayr, N. W. Spencer, A. E. Hedin, Bela G. Fejer
Interaction Of The Zonalwinds With The Equatorial Midnight Pressure Bulge In The Earth's Thermosphere: Empiricalevidence Of Momentum Balance, F. A. Herrero, H. G. Mayr, N. W. Spencer, A. E. Hedin, Bela G. Fejer
Bela G. Fejer
A minimum is observed at midnight in the time variation of averaged zonal winds measured in-situ near the equator at an average altitude of about 350 km, and we inquire whether observations of the equatorial midnight pressure bulge are consistent with this feature. The observed zonal wind maintains an eastward direction all night. It increases steadily in the early evening reaching a maximum of about 160 m/s at 2100 hrs local time (LT), dropping to a minimum of about 70 m/s around 2400 LT, then up to about 120 m/s around 0300 LT, decreasing thereafter and turning westward in the …
Radar Measurements Of Neutral Winds And Temperatures In The Equatorial E Region, B. B. Balsley, Bela G. Fejer, D. T. Farley, R. F. Woodman
Radar Measurements Of Neutral Winds And Temperatures In The Equatorial E Region, B. B. Balsley, Bela G. Fejer, D. T. Farley, R. F. Woodman
Bela G. Fejer
The phase velocity of type 1 irregularities in the equatorial electrojet, which can be easily measured by radar, depends upon both the ion acoustic velocity (and hence the temperature) in the medium and the neutral wind velocity. By measuring the phase velocity at several zenith angles both of these quantities in principle can be determined. This note describes the technique and its limitations and presents a few preliminary results obtained at 50 MHz at the Jicamarca Radar Observatory in Peru. These results show E region east-west wind velocities as large as 100 m/s, temperature variations of greater than 100°K, and …