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Full-Text Articles in Physics
The Condorequatorial Spread-F Campaign: Overview And Results Of The Large-Scale Measurements, M. C. Kelley, J. Labelle, E. Kudeki, Bela G. Fejer, S. Basu, Su. Basu, K. D. Baker, C. Hanuise, P. Argo, R. F. Woodland, W. E. Swartz, D. T. Farley, J. W. Meriwether
The Condorequatorial Spread-F Campaign: Overview And Results Of The Large-Scale Measurements, M. C. Kelley, J. Labelle, E. Kudeki, Bela G. Fejer, S. Basu, Su. Basu, K. D. Baker, C. Hanuise, P. Argo, R. F. Woodland, W. E. Swartz, D. T. Farley, J. W. Meriwether
Bela G. Fejer
During the Condor campaign a number of instruments were set up in Peru to support the rocket experiments. In this series of papers we report on the results of the experiments designed to study the equatorial F region. In this overview paper we summarize the main results as well as report upon the macroscopic developments of spread F as evidenced by data from backscatter radars, from scintillation observations, and from digital ionosonde meaurements. In this latter regard, we argue here that at least two factors other than the classical gravitational Rayleigh-Taylor plasma instability process must operate to yield the longest-scale …
Gigahertz Scintillations And Spaced Receiver Drift Measurements During Project Condorequatorial F-Region Rocket Campaign In Peru, S. Basu, Sa. Basu, J. Labelle, E. Kudeki, Bela G. Fejer, M. C. Kelley, H. E. Whitney
Gigahertz Scintillations And Spaced Receiver Drift Measurements During Project Condorequatorial F-Region Rocket Campaign In Peru, S. Basu, Sa. Basu, J. Labelle, E. Kudeki, Bela G. Fejer, M. C. Kelley, H. E. Whitney
Bela G. Fejer
Radar backscatter at 50 MHz, rocket, and VHF/GHz scintillation measurements of spread F irregularities at the magnetic equator in Peru were made during the Project Condor campaign in March 1983. The paper discusses the coordinated set of observations on two evenings, March 1 and March 14, 1983, when the altitude of the F region peak differed by more than 150 km. The full complement of equatorial spread F phenomena, namely, the occurrence of 3-m plume structures and VHF/GHz scintillations, were recorded on both these evenings. It was found that the radar backscatter with extended plumes occurs in association with maximum …
The Prereversal Enhancement Of Thezonal Electric Field In The Equatorial Ionosphere, D. T. Farley, E. Bonelli, Bela G. Fejer, M. F. Larsen
The Prereversal Enhancement Of Thezonal Electric Field In The Equatorial Ionosphere, D. T. Farley, E. Bonelli, Bela G. Fejer, M. F. Larsen
Bela G. Fejer
The electric fields in the ionospheric E and F regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward (normally) daytime field reverses to westward. Several theoretical models of the low-latitude fields suggest that this enhancement is caused mainly or entirely by F region winds (the F region dynamo), but some authors have suggested that it could be produced solely by E region tidal winds. We give here additional calculations and arguments in support of the F region source. The enhancement of the eastward field for an eastward F region wind turns …
Equatorial F-Region Zonal Plasma Drifts, Bela G. Fejer, E. Kudeki, D. T. Farley
Equatorial F-Region Zonal Plasma Drifts, Bela G. Fejer, E. Kudeki, D. T. Farley
Bela G. Fejer
We have examined in detail the F region plasma drifts measured at Jicamarca, Peru, during 1978–1981, a period of high solar activity, and compared these drifts with Jicamarca data taken during periods of lower activity, as well as with other equatorial zonal neutral wind and plasma drift measurements. The increase in solar activity causes larger nighttime eastward plasma drifts at Jicamarca and delays the morning reversal time from eastward nighttime to westward daytime drifts. The radar data seem to be in good agreement with nighttime neutral wind measurements made by the DE-2 satellite, but are systematically smaller than spaced receiver …
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 …
Theory Of Spectral Asymmetries And Nonlinear Currentsin The Equatorial Electrojet, E. Kudeki, D. T. Farley, Bela G. Fejer
Theory Of Spectral Asymmetries And Nonlinear Currentsin The Equatorial Electrojet, E. Kudeki, D. T. Farley, Bela G. Fejer
Bela G. Fejer
The spectral up-down asymmetry of type 1 echoes returned from the equatorial electrojet irregularities is shown to be a consequence of the nonlinear development of the horizontally propagating large scale primary waves which dominate the k spectrum of the electrojet turbulence. The waves reduce the vertical electric polarization field of the electrojet and suffer second harmonic distortion as they grow. These effects together could cause an asymmetry exceeding 20% between the upward and downward components of the relative (to the ions) electron velocity associated with the primary waves. This asymmetry, which changes its direction from day to night as does …
Refilling Of Geosynchronous Flux Tubes As Observed At The Equator By Geos 2, Jan Josef Sojka, G. L. Wrenn
Refilling Of Geosynchronous Flux Tubes As Observed At The Equator By Geos 2, Jan Josef Sojka, G. L. Wrenn
All Physics Faculty Publications
During periods of extended quiet geomagnetic activity the geosynchronous satellite orbit lies inside the plasmasphere. Five such periods were observed by the GEOS 2 satellite. During the initial 48 hours of such periods the equatorial plasma flux tube density increases at 30 to 50 cm−3/day. However, on reaching ∼100 cm−3 the refilling rate decreases, and refilling is limited. Only when the density reaches ∼100 cm−3 do the plasma characteristics and fluctuations appear to be plasmaspheric and the flow predominantly corotational. The “hot outer zone” of the plasmasphere is highly structured in density and temperature when viewed …
Equatorial Disturbance Dynamo Electric Fields, Bela G. Fejer, M. F. Larsen, D. T. Farley
Equatorial Disturbance Dynamo Electric Fields, Bela G. Fejer, M. F. Larsen, D. T. Farley
Bela G. Fejer
F-region vertical drift data from Jicamarca, Peru show that equatorial east-west electric fields are sometimes perturbed 16-24 hours after the onset of geomagnetic storms. These disturbance dynamo electric fields, which must be caused primarily by the action of neutral winds at low and middle latitudes, decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime. The long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed. The data also show that after some storms there are no such delayed disturbances, a fact which may be due …
In-Situ Measurements Ofwave Electric Fields In The Equatorial Electrojet, R. C. Pfaff, M. C. Kelley, Bela G. Fejer, N. C. Maynard, K. D. Baker
In-Situ Measurements Ofwave Electric Fields In The Equatorial Electrojet, R. C. Pfaff, M. C. Kelley, Bela G. Fejer, N. C. Maynard, K. D. Baker
Bela G. Fejer
Electric field wave measurements have been performed on two sounding rockets in the equatorial ionosphere. During a daytime flight from Chilca, Peru, intense electrostatic waves were detected on the upward directed electron density gradient. During a nighttime flight from Kwajalein Atoll, similar waves were detected on a downward directed gradient. These results are in agreement with a gradient drift instability explanation of the generation of the waves. The wave amplitudes were as high as 5 mV/m implying perturbation drifts comparable to the driving drift velocities. Power spectra from the turbulent region show a peak at long wavelengths, followed by a …
Reply (To "Comment On 'The Absolute Scattering Cross Section At50 Mhz Of Equatorial Electrojet Irregularities' By Farley Et Al." By N. D'Angelo), D. T. Farley, Bela G. Fejer
Reply (To "Comment On 'The Absolute Scattering Cross Section At50 Mhz Of Equatorial Electrojet Irregularities' By Farley Et Al." By N. D'Angelo), D. T. Farley, Bela G. Fejer
Bela G. Fejer
No abstract provided.
The Absolute Scattering Cross Section At 50 Mhz Ofequatorial Electrojet Irregularities, D. T. Farley, H. M. Ierkic, Bela G. Fejer
The Absolute Scattering Cross Section At 50 Mhz Ofequatorial Electrojet Irregularities, D. T. Farley, H. M. Ierkic, Bela G. Fejer
Bela G. Fejer
We have made carefully calibrated radar scattering measurements by using the large 50-MHz Jicamarca antenna. Typical results from the altitudes of maximum echo power for the vertically directed beam are σradar ∼1–2 × 10−10 m−1 for strong daytime electrojet conditions with type 1 irregularities present, with values a factor of 10 or so smaller during moderate conditions when only type 2 are observed. These cross sections, which are very large in comparison with those for incoherent scatter (σradar ≃5 × 10−18 m−1 for an electron density of 1011 m−3), are not nearly large enough, however, to cause pseudo-absorption events on …
Interferometer Studies Of Equatorial Fregion Irregularities And Drifts, E. Kudeki, Bela G. Fejer, D. T. Farley, H. M. Ierkic
Interferometer Studies Of Equatorial Fregion Irregularities And Drifts, E. Kudeki, Bela G. Fejer, D. T. Farley, H. M. Ierkic
Bela G. Fejer
A radar interferometer technique developed at Jicamarca, Peru and first used to study electrojet irregularities has now been used successfully to study plasma turbulence in the equatorial F region. Our first results have shown that the most ‘turbulent’ echoes appear to come from a region that extends for tens of kilometers in altitude but for only a kilometer or less in the east-west direction. This slab may very well be the wall of a depleted region, a plasma ‘bubble’. Sometimes the irregularities can be tracked as they move eastward or westward. Velocity profiles for the evening period obtained in this …
The Dependence On Zenith Angle Of The Strength Of 3-Meter Equatorial Electrojet Irregularities, H. M. Ierkic, Bela G. Fejer, D. T. Farley
The Dependence On Zenith Angle Of The Strength Of 3-Meter Equatorial Electrojet Irregularities, H. M. Ierkic, Bela G. Fejer, D. T. Farley
Bela G. Fejer
Radar measurements in Peru were used to deduce the zenith angle dependence of the scattering cross section of plasma irregularities generated by instabilities in the equatorial electrojet. The irregularities probed by the 50 MHz Jicamarca radar had a wavelength of 3m. The cross section for the type 2 irregularities was isotropic in the plane perpendicular to the magnetic field, while the cross section for the stronger type 1 irregularities varied with zenith angle at a rate of approximately 0.3 dB/degree; the horizontally traveling waves were more than 100 times stronger than those traveling vertically.
Type I Radar Echoes From Theequatorial Electrojet With Double Peaked Doppler Spectra, Bela G. Fejer, D. T. Farley, P. Johnston, B. B. Balsley
Type I Radar Echoes From Theequatorial Electrojet With Double Peaked Doppler Spectra, Bela G. Fejer, D. T. Farley, P. Johnston, B. B. Balsley
Bela G. Fejer
Normal type 1 radar echoes obtained from relatively large zenith angles have a power spectrum with a single narrow peak whose Doppler shift corresponds approximately to the acoustic velocity in the medium. On some occasions, however, this single maximum splits into two distinct peaks, separated in phase velocity on one occasion by 270 m/s. This bifurcation is most easily observed at large zenith angles during daytime when a narrow antenna beam is used. It has also been seen in a daytime experiment in which radars at Jicamarca and Huancayo simultaneously probed the same region from two different radar zenith angles. …
Equatorial Electricfields During Magnetically Disturbed Conditions, 1. The Effect Of The Interplanetary Magneticfield, Bela G. Fejer, C. A. Gonzales, D. T. Farley, M. C. Kelley, R. F. Woodman
Equatorial Electricfields During Magnetically Disturbed Conditions, 1. The Effect Of The Interplanetary Magneticfield, Bela G. Fejer, C. A. Gonzales, D. T. Farley, M. C. Kelley, R. F. Woodman
Bela G. Fejer
Radar measurements of E and F region drift velocities have been used to look for correlations between changes in equatorial electric fields and the interplanetary magnetic field (IMF). The east-west component of the IMF appears to be unimportant, but the north-south component has some effect; rapid reversals from south to north are sometimes correlated with reversals of the equatorial east-west electric field during both daytime and nighttime. This is not always true, however, the IMF may reverse without any apparent effect at the equator. Furthermore, large equatorial field perturbations are sometimes observed when the IMF Bz is large and southward …
Equatorialelectric Fields During Magnetically Disturbed Conditions, 2. Implications Of Simultaneousauroral And Equatorial Measurements, C. A. Gonzales, M. C. Kelley, Bela G. Fejer, J. F. Vickrey, R. F. Woodman
Equatorialelectric Fields During Magnetically Disturbed Conditions, 2. Implications Of Simultaneousauroral And Equatorial Measurements, C. A. Gonzales, M. C. Kelley, Bela G. Fejer, J. F. Vickrey, R. F. Woodman
Bela G. Fejer
Simultaneous auroral and equatorial electric field data are used along with magnetic field data to study anomalous electric field patterns during disturbed times. During some substorms, accompanied by ring current activity, the worldwide equatorial zonal electric field component reverses from the normal pattern. This is interpreted as a partial closure of high latitude field aligned currents in the dayside, low latitude ionosphere. These currents flow westward across the dayside. In several cases the zonal equatorial electric field component was nearly identical in form to the zonal auroral component, indicating the close electrical coupling between these regions. Less certain, but equally …
Radar Observations Of Two Dimensional Turbulencein The Equatorial Electrojet, 3. Nighttime Observations Of Type I Waves, D. T. Farley, Bela G. Fejer, B. B. Balsley
Radar Observations Of Two Dimensional Turbulencein The Equatorial Electrojet, 3. Nighttime Observations Of Type I Waves, D. T. Farley, Bela G. Fejer, B. B. Balsley
Bela G. Fejer
The large vertically directed 50-MHz radar at Jicamarca has sufficient sensitivity to study nighttime echoes from the equatorial electrojet in detail with good resolution. Here we concentrate on type 1 (‘two-stream’) echoes. We find that (1) these echoes sometimes dominate the spectrum (which is never the case in daytime for a vertically directed radar), (2) they are observed over a much wider range of altitudes than they are during daytime, (3) they show an asymmetry which reverses from day to night (downgoing waves are more common at night), (4) the magnitude of the mean Doppler shift appears to increase somewhat …
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.
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 …