scholarly journals Excitation of Plasma Irregularities in the F Region of the Ionosphere by Powerful HF Radio Waves of X-Polarization

2018 ◽  
Vol 123 (6) ◽  
pp. 5246-5260 ◽  
Author(s):  
N. Borisov ◽  
F. Honary ◽  
H. Li
Keyword(s):  
Radio Waves ◽  
Plasma Irregularities ◽  
F Region

scholarly journals Plasma irregularities in the tropical F-region detected by OI 7774 Å and 6300 Å nightglow measurements

1981 ◽  
Vol 86 (A5) ◽  
pp. 3496 ◽  
Author(s):  
Y. Sahai ◽  
J. A. Bittencourt ◽  
N. R. Teixeira ◽  
H. Takahashi
Keyword(s):  
Plasma Irregularities ◽  
F Region

scholarly journals HF-Induced Modifications of the Electron Density Profile in the Earth’s Ionosphere Using the Pump Frequencies near the Fourth Electron Gyroharmonic

2021 ◽  
Vol 13 (23) ◽  
pp. 4895
Author(s):  
Alexey V. Shindin ◽  
Evgeny N. Sergeev ◽  
Savely M. Grach ◽  
Gennady M. Milikh ◽  
Paul Bernhardt ◽  
...  
Keyword(s):  
Density Profile ◽  
Ionospheric Plasma ◽  
Pump Wave ◽  
Electromagnetic Emission ◽  
Electron Density Profile ◽  
Radio Waves ◽  
F Region ◽  
Plasma Density Profile ◽  
Hybrid Region ◽  
Hf Heating

We discuss results on plasma density profile modifications in the F-region ionosphere that are caused by HF heating with the frequency f0 in the range [(−150 kHz)–(+75 kHz)] around the fourth electron gyroharmonic 4fc. The experiments were conducted at the HAARP facility in June 2014. A multi-frequency Doppler sounder (MDS), which measures the phase and amplitude of reflected sounding radio waves, complemented by the observations of the stimulated electromagnetic emission (SEE) were used for the diagnostics of the plasma perturbations. We detected noticeable plasma expulsion from the reflection region of the pumping wave and from the upper hybrid region, where the expulsion from the latter was strongly suppressed for f0 ≈ 4fc. The plasma expulsion from the upper hybrid region was accompanied by the sounding wave’s anomalous absorption (AA) slower development for f0 ≈ 4fc. Furthermore, slower development and weaker expulsion were detected for the height region between the pump wave reflection and upper hybrid altitudes. The combined MDS and SEE allowed for establishing an interconnection between different manifestations of the HF-induced ionospheric turbulence and determining the altitude of the most effective pump wave energy input to ionospheric plasma by using the dependence on the offset between f0 and 4fc.

scholarly journals Nonlinear forecasts of ƒ<i>o</i>F2: variation of model predictive accuracy over time

2002 ◽  
Vol 20 (7) ◽  
pp. 1031-1038 ◽  
Author(s):  
A. H. Y. Chan ◽  
P. S. Cannon
Keyword(s):  
Real Time ◽  
Space Weather ◽  
Predictive Accuracy ◽  
Radio Waves ◽  
New Techniques ◽  
Radio Science ◽  
F Region ◽  
Instruments And Techniques ◽  
Using Data ◽  
Hf Communications

Abstract. Space weather effects can strongly influence high-frequency (HF) communications by changing the ionospheric environment through which the radio waves propagate. Since many systems utilize HF communications, the ability to make real-time assessments of propagation conditions is an important part of space weather monitoring systems. In this paper, we present new techniques for measuring high-latitude HF communications link parameters using data from SuperDARN radars. These techniques use ground-scatter returns to define the variation in skip distance with frequency. From these data, the maximum usable frequency (MUF) as a function of range is determined and ionospheric critical frequencies are estimated. These calculations are made in near-real-time and the results are made available on the World Wide Web. F-region critical frequencies calculated using this method show good agreement with ionosonde data.Key words. Ionosphere (active experiments; instruments and techniques) – Radio science (ionospheric propagation)

scholarly journals Study of Equatorial Plasma Bubbles Using ASI and GPS Systems

2020 ◽  
Author(s):  
Dada P. Nade ◽  
Swapnil S. Potdar ◽  
Rani P. Pawar
Keyword(s):  
Electron Content ◽  
Gps Receiver ◽  
Plasma Bubble ◽  
Low Latitude ◽  
Total Electron ◽  
Plasma Irregularities ◽  
Plasma Bubbles ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Background Density

The plasma irregularities have been frequently observed in the F-region, at low latitude regions, due to the instability processes occurring in the ionosphere. The depletions in electron density, as compared to the background density, is a signature of the plasma irregularities. These irregularities are also known as the “equatorial plasma bubble” (EPB). These EPBs can measure by the total electron content (TEC) using GPS receiver and by images of the nightglow OI 630.0 nm emissions using all sky imager (ASI). The current chapter is based on the review on the signature of the EPBs in TEC and ASI. measurements. We have also discussed the importance of the study of EPBs.

scholarly journals A comparison of velocity measurements from the CUTLASS Finland radar and the EISCAT UHF system

1999 ◽  
Vol 17 (7) ◽  
pp. 892-902 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
S. E. Milan ◽  
T. K. Yeoman
Keyword(s):  
Total Duration ◽  
Field Of View ◽  
Simultaneous Occurrence ◽  
Plasma Convection ◽  
Contributing Factors ◽  
Plasma Irregularities ◽  
Incoherent Scatter ◽  
F Region ◽  
Initial Comparison ◽  
E Region

Abstract. The CUTLASS Finland radar, which comprises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a field-of-view which extends over some four million square kilometres. Within the Finland radar field-of-view lie both the EISCAT mainland and EISCAT Svalbard incoherent scatter radar facilities. Since the CUTLASS Finland radar commenced operation, in February 1995, the mainland EISCAT UHF radar has been run in common programme 1 and 2 modes for a total duration exceeding 1000 h. Simultaneous and spatially coincident returns from these two radars over this period provide the basis for a comparison of irregularity drift velocity and F-region ion velocity. Initial comparison is limited to velocities from four intervals of simultaneous radar returns; intervals are selected such that they exhibit a variety of velocity signatures including that characteristic of the convection reversal and a rapidly fluctuating velocity feature. Subsequent comparison is on a statistical basis. The velocities measured by the two systems demonstrate reasonable correspondence over the velocity regime encountered during the simultaneous occurrence of coherent and incoherent scatter; differences between the EISCAT UHF measurements of F-region ion drift and the irregularity drift velocities from the Finland radar are explained in terms of a number of contributing factors including contamination of the latter by E-region echoes, a factor which is investigated further, and the potentially deleterious effect of discrepant volume and time sampling intervals.Key words. Ionosphere (ionospheric irregularities; plasma convection)

Back-scattering of radio waves from the artificially perturbed F-region of the ionosphere

1976 ◽  
Vol 19 (7) ◽  
pp. 769-771 ◽  
Author(s):  
V. V. Belikovich ◽  
E. A. Benedictov ◽  
G. G. Getmantsev ◽  
Yu. A. Ignat'ev ◽  
G. P. Komrakov
Keyword(s):  
Radio Waves ◽  
F Region ◽  
Back Scattering

Diffusion spreading of middle-latitude ionospheric plasma irregularities

1995 ◽  
Vol 13 (6) ◽  
pp. 617-626 ◽  
Author(s):  
N. Blaunstein
Keyword(s):  
Ionospheric Plasma ◽  
Three Dimensional ◽  
Middle Latitude ◽  
Approximate Model ◽  
Ionospheric Irregularities ◽  
Radio Waves ◽  
Plasma Irregularities ◽  
Relaxation Effects ◽  
Artificial Heating ◽  
Actual Height

Abstract. In contrast to the way that the spreading of irregularities in a plasma is usually considered, the diffusion spreading of irregularities stretched along the geomagnetic field B is examined using a three-dimensional rigorous numerical model of quasi-neutral diffusion in the presence of a magnetic field, in conjunction with the actual height variations of the diffusion and conductivity tensors in the ionosphere. A comparison with the earlier constructed approximate model of unipolar diffusion was made. As in the previous case, the same peculiarities of irregularity spreading in the inhomogeneous background ionospheric plasma were observed. The accuracy of the approximate model for describing the process of spreading of anisotropic ionospheric irregularities is established. Time relaxation effects of real heating-induced ionospheric irregularities on their scale transverse to B are presented using the approximate analytical model for the case of a quasi-homogeneous ionospheric plasma. The calculated results have a vivid physical meaning and can be directly compared with experimental data on the radiophysical observations of artificial heating-induced irregularities created by powerful radio waves in the ionosphere.

scholarly journals Usage of regularization techniques for effective electron collision frequency determination from oblique ionospheric sounding

1996 ◽  
Vol 14 (8) ◽  
pp. 811-815 ◽  
Author(s):  
P. F. Denisenko ◽  
N. V. Nastasyina ◽  
V. I. Vodolazkin
Keyword(s):  
Measurement Errors ◽  
Computer Modelling ◽  
Collision Frequency ◽  
Electron Collision ◽  
Radio Waves ◽  
Absorption Data ◽  
Effective Electron ◽  
F Region ◽  
Electron Collision Frequency ◽  
Regularization Techniques

Abstract. Computer modelling is used to investigate the possibility of determining ionospheric parameters from slightly oblique ionospheric soundings, using absorption data for decametric radio waves of different polarization. It is shown that with mean square measurement errors of 0.5 dB, and using regularization algorithms to solve the inverse problems, electron collision frequency profiles can be obtained for the night F-region with errors of less than 30%. Both temperatures of electrons and neutrals are also determined to within 10%.

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