scholarly journals The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

2013 ◽  
Vol 118 (11) ◽  
pp. 7472-7481 ◽  
Author(s):  
C. J. Bryers ◽  
M. J. Kosch ◽  
A. Senior ◽  
M. T. Rietveld ◽  
T. K. Yeoman
Keyword(s):  
High Frequency ◽  
Ionospheric Plasma ◽  
Plasma Instabilities ◽  
Radio Waves

Reflection of high-frequency radio waves in inhomogeneous ionospheric layers

Radio Science ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Kenneth Davies ◽  
Charles M. Rush
Keyword(s):  
High Frequency ◽  
Radio Waves

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 Magnetic Fields in the Spiral Galaxy NGC 6946

1993 ◽  
Vol 157 ◽  
pp. 311-312
Author(s):  
Matthias Ehle ◽  
Rainer Beck
Keyword(s):  
Magnetic Field ◽  
Spiral Galaxy ◽  
High Frequency ◽  
Uniform Magnetic Field ◽  
Large Scale ◽  
Dynamo Model ◽  
Model Parameters ◽  
Radio Waves ◽  
Spiral Pattern ◽  
Ngc 6946

High frequency polarization observations reveal the existence of a large-scale ordered magnetic field in the disk of the spiral galaxy NGC 6946. At lower frequencies the disk is no longer transparent to polarized radio waves due to Faraday depolarization. The spiral pattern of the uniform magnetic field and the distribution of polarized intensities are fairly well simulated by a dynamo model. The model parameters indicate that the dynamo does not only operate in the disk, but also in the halo.

An Airplane Psychrograph*

1947 ◽  
Vol 28 (8) ◽  
pp. 363-370 ◽  
Author(s):  
Isadore Katz
Keyword(s):  
Water Vapor ◽  
High Frequency ◽  
Radio Waves ◽  
Ultra High Frequency ◽  
Anomalous Propagation

An airplane psychrograph has been designed to make measurements in the lowest several thousand feet of the atmosphere. These measurements are necessary in order to understand the phenomena causing anomalous propagation associated with the ultra-high frequency radio waves used for radar. The instrument employs ceramic resistors as wet and dry elements; they are rapid in response and sensitive enough for measuring sharp gradients of temperature and water vapor usually present close to the boundary between the air and the water or land. Detail of the construction and use of the airplane psychrograph are described.

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