Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Equator (49)
- Ionosphere (26)
- Plasma (20)
- Electric (17)
- Electrojet (17)
-
- F region (17)
- Field (16)
- Drifts (15)
- Vertical (14)
- Radar (13)
- Drift (11)
- Equatorial (10)
- Latitude (10)
- Low (9)
- Winds (9)
- Auroral (8)
- Disturbance (8)
- Irregularities (8)
- Solar (8)
- Thermosphere (8)
- Zonal (8)
- Magnetic (6)
- Climatology (5)
- Density (5)
- Jicamarca (5)
- Mid (5)
- Neutral (5)
- Quiet (5)
- Satellite (5)
- Storm (5)
Articles 91 - 96 of 96
Full-Text Articles in Physical Sciences and Mathematics
Radar Observations Of Two Dimensional Turbulence In The Equatorial Electrojet, 2, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Radar Observations Of Two Dimensional Turbulence In The Equatorial Electrojet, 2, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Bela G. Fejer
Observations with an altitude resolution of about 1 km were made with the large, vertically directed 50-MHz radar system at the Jicamarca Radar Observatory during the day, when the electrojet was strong. Type 1 (‘two stream’) echoes were seen in a limited range of altitudes, with Doppler shifts corresponding to upward and downward motion at the acoustic velocity. Most of the radar returns were due to type 2 echoes, however. The direction of motion of the type 1 waves sometimes reversed in as little as 1 s, supporting a turbulent model of the electrojet region. During the day the upgoing …
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 …
Radar Studies Of Anomalousvelocity Reversals In The Equatorial Ionosphere, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Radar Studies Of Anomalousvelocity Reversals In The Equatorial Ionosphere, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Bela G. Fejer
Radar observations made at Jicamarca show that the equatorial electrojet current and the E and F region electric fields can reverse from their normal direction during the day or night and during magnetically quiet or disturbed conditions. The nighttime reversals can only be detected by such radar measurements. The observations support most of the current hypotheses concerning the electrojet plasma instabilities. The rapid reversals sometimes seen during disturbed conditions indicate that high-latitude currents and electric fields associated with substorm activity strongly perturb the dynamo current system at all latitudes.
The Effect Of The Gradient-Drift Term On Type I Electrojet Irregularities, D. T. Farley, Bela G. Fejer
The Effect Of The Gradient-Drift Term On Type I Electrojet Irregularities, D. T. Farley, Bela G. Fejer
Bela G. Fejer
We hypothesize that type 1 VHF radar echoes can only be observed when the electrojet plasma is linearly unstable at half the radar wavelength and that further, for reasons not yet understood, the phase velocity of the unstable waves always corresponds to the threshold conditions for instability, even when the destabilizing forces (electron drift and plasma density gradient) exceed the threshold. This phase velocity, which produces the Doppler shift of the radar echoes, is usually close to the ion acoustic velocity of the medium but can differ from it to some extent because of the effect of the density gradient. …
Vertical Structure Of The Vhf Backscattering Region In The Equatorial Electrojet And The Gradient Drift Instability, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Vertical Structure Of The Vhf Backscattering Region In The Equatorial Electrojet And The Gradient Drift Instability, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Bela G. Fejer
Radar measurements made with high spatial resolution and large dynamic range at the Jicamarca Radar Observatory near the time of reversal of the electrojet current provide further proof that the gradient drift instability is in fact responsible for the type 2 irregularities. Echoes are received over a much wider range of altitudes at night than during the day partly because of the change in character of the background electron density profile and partly because of recombination effects, which can be important during the day. It is also shown that one must be cautious, particularly at night, in associating the mean …
Oblique Vhf Spectral Studies Ofthe Equatorial Electrojet, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Oblique Vhf Spectral Studies Ofthe Equatorial Electrojet, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Bela G. Fejer
A new narrow-beam antenna at the Jicamarca Observatory permits oblique (zenith angle, 25°) radar spectral studies of the electrojet with an altitude resolution down to 1.1 km. Only daytime observations are possible presently, however. The general altitude variations in spectral shape observed are consistent with linear instability theory, if the effect of recombination is included. The height at which the mean Doppler shift of the echo maximizes, however, is about 4 km higher than one would expect on the basis of electrojet models. An increase in the assumed collision frequency would remove the discrepancy. Other data presented strongly suggest that …