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

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.

Linear and Nonlinear Plasma Processes in Ionospheric HF Heating

Featured observations of high frequency (HF) heating experiments are first introduced; the uniqueness of each observation is presented; the likely cause and physical process of each observed phenomenon instigated by the HF heating are discussed. A special point in the observations, revealed through the ionograms, is the competition between the Langmuir parametric instability and upper hybrid parametric instability excited in the heating experiments and the impact of the natural cusp at foE (the peak plasma frequency of the ionospheric E region) on the competition. The ionograms also infer the generation of Langmuir and upper hybrid cavitons. Ray tracing theory is formulated. With and without the appearance of large-scale field-aligned density irregularities in the background ionosphere, ray trajectories of the ordinary mode (O-mode) and extraordinary mode (X-mode) sounding pulses are calculated numerically. The results explain the artificial Spread-F recorded by the digisondes in the heating experiments. Parametric instabilities, which are the directly relevant processes to achieve effective heating of the ionospheric F region, are formulated and analyzed. The threshold fields and growth rates of Langmuir and upper hybrid parametric instabilities are derived as the theoretical basis of many radar observations and electron-plasma wave interactions. Harmonic cyclotron resonance interaction processes between electrons and upper hybrid waves are introduced. Formulation and analysis are presented. The numerical results show that ultra-energetic electrons are generated. These electrons enhance airglow at 777.4 nm as well as cause ionization. Physical processes leading to the generation of artificial ionization layers are discussed. The nonlinear Schrodinger equation governing the nonlinear evolution of Langmuir waves and upper hybrid waves are derived and solved. The nonlinear periodic and solitary solutions of the equations are obtained. The localized Langmuir and upper hybrid waves generated by the HF heater form cavitons near the HF reflection layer and near the upper hybrid resonance layer, which induce bumps in the virtual height spread of the ionogram trace similar to that induced by the density cusp at E-F1 transition layer; the down-going Langmuir waves and upper hybrid waves evolve into nonlinear periodic waves propagating along the magnetic field, which backscatter incoherently the sounding pulses to cause downward virtual height spread.

Local High-Frequency Heating in Electronics Technology

Modeling and investigation of HF electromagnetic heating in induction devices with unclosed magnetic circuit has allowed to optimize heating speed in local zones of formation of soldering connections and to improve their quality due to joint action of superficial effects and electromagnetic forces. For all magnetic materials is nonlinear decrease in heating power depending on frequency of HF. Installed the optimal parameters of HF heating for soldering electronics modules by inductor with open-ended magnetic conductor.

Estudios recientes de ecos polares mesosféricos de verano bajo ondas HF

<p>La intensidad de una capa de los ecos polares mesosféricos de verano (EPMV) muestra una distribución con forma de “montaña”. En este trabajo se presenta evidencia que efectos en el EPMV, debido al calentamiento artificial de electrones ionosféricos causado por el HF heating, se manifiestan principalmente en la región interna alrededor del pico del EPMV. Evaluando sólo tal región interna conducirá a otras estimaciones de temperatura de electrones y otros estados de los procesos físicos como difusión de electrones y cargado de las partículas de polvo. En primera instancia, este descubrimiento puede servir a mejorar los modelos disponibles sobre EPMV bajo HFheating. Se discute acerca de posibles interpretaciones físicas considerando tamaño y densidad de electrones y las partículas de polvo. También se discute en términos de los principales procesos físicos: difusión de electrones y cargado eléctrico de partículas de polvo. No se ha encontrado efectos del HF-heating en los parámetros de la dinámica neutral: velocidad radial y ancho espectral. Un beneficio tecnológico del presente trabajo es que para detectar y evaluar los efectos del HF-hosting no se requieren potentes transmisiones de radar. Permitiendo usar tecnología más asequible que además permitirá realizar mediciones más continuas de la Mesosfera Polar.</p>