S. J. Briczinski

Electron gyroharmonic effects on ionospheric stimulated Brillouin scatter

Stimulated Brillouin scattering (SBS) and resonant phenomena are well known in the context of laser fusion, fiber optics, and piezoelectric semiconductor plasmas, as well as in various biological applications. Due to recent advances, active space experiments using high-power high-frequency (HF) radio waves may now produce stimulated Brillouin scattering (SBS) in the ionospheric plasma. The sensitivity of the narrowband SBS emission lines to pump frequency stepping across electron gyroharmonics is reported here for the first time. Experimental observations show that SBS emission sidebands are suppressed as the HF pump frequency is stepped across the second and third electron gyroharmonics. A correlation of artificially enhanced airglow and SBS emission lines excited at the upper hybrid altitude is observed and studied for second gyroharmonic heating. The SBS behavior near electron gyroharmonics is shown to have important diagnostic applications for multilayered, multi-ion component plasmas such as the ionosphere.

Ion gyroharmonic structures in stimulated radiation during second electron gyroharmonic heating: 2. Simulations

Characteristics of the Stimulated Electromagnetic Emission (SEE) spectrum recorded during ionospheric heating near the second electron gyroharmonic frequency, 2fce, have attracted attention due to their possible connection to artificially generated airglow and artificial ionospheric layers. Two newly discovered SEE spectral features within 1 kHz frequency shift relative to the pump frequency are (1) discrete narrowband structures ordered by the local ion gyrofrequency involving parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and ion Bernstein (IB) waves and (2) broadband structures that maximize around 500 Hz downshifted relative to the pump frequency involving parametric decay of the pump field into upper hybrid/electron Bernstein and oblique ion acoustic (IA) waves [Samimi et al., 2013]. In this paper, a two-dimensional particle-in-cell Monte Carlo Collision computational model is employed in order to consider nonlinear aspects such as (1) electron acceleration through wave-particle interaction, (2) more complex nonlinear wave-wave processes, and (3) temporal evolution of irregularities through nonlinear saturation. The simulation results show that the IB-associated parametric decay is primarily associated with electron acceleration perpendicular to the geomagnetic field. More gyroharmonic lines are typically associated with more electron acceleration. Electron acceleration is reduced when the pump frequency is sufficiently close to 2fce. The IA-associated parametric decay instability is primarily associated with electron tail heating along the magnetic field and electron acceleration is reduced when the pump frequency is sufficiently close to 2fce. Characteristics of caviton collapse behavior become prevalent in this case. Results are discussed within the context of some recent experimental observations.

A physics‐based model for the ionization of samarium by the MOSC chemical releases in the upper atmosphere

Atomic samarium has been injected into the neutral atmosphere for production of electron clouds that modify the ionosphere. These electron clouds may be used as high-frequency radio wave reflectors or for control of the electrodynamics of the F region. A self-consistent model for the photochemical reactions of Samarium vapor cloud released into the upper atmosphere has been developed and compared with the Metal Oxide Space Cloud (MOSC) experimental observations. The release initially produces a dense plasma cloud that that is rapidly reduced by dissociative recombination and diffusive expansion. The spectral emissions from the release cover the ultraviolet to the near infrared band with contributions from solar fluorescence of the atomic, molecular, and ionized components of the artificial density cloud. Barium releases in sunlight are more efficient than Samarium releases in sunlight for production of dense ionization clouds. Samarium may be of interest for nighttime releases but the artificial electron cloud is limited by recombination with the samarium oxide ion.

Large ionospheric disturbances produced by the HAARP HF facility

The enormous transmitter power, fully programmable antenna array, and agile frequency generation of the High Frequency Active Auroral Research Program (HAARP) facility in Alaska have allowed the production of unprecedented disturbances in the ionosphere. Using both pencil beams and conical (or twisted) beam transmissions, artificial ionization clouds have been generated near the second, third, fourth, and sixth harmonics of the electron gyrofrequency. The conical beam has been used to sustain these clouds for up to 5 h as opposed to less than 30 min durations produced using pencil beams. The largest density plasma clouds have been produced at the highest harmonic transmissions. Satellite radio transmissions at 253 MHz from the National Research Laboratory TACSat4 communications experiment have been severely disturbed by propagating through artificial plasma regions. The scintillation levels for UHF waves passing through artificial ionization clouds from HAARP are typically 16 dB. This is much larger than previously reported scintillations at other HF facilities which have been limited to 3 dB or less. The goals of future HAARP experiments should be to build on these discoveries to sustain plasma densities larger than that of the background ionosphere for use as ionospheric reflectors of radio signals.

Visible Plasma Clouds With an Externally Excited Spherical Porous Cavity Resonator

A microwave driven resonator is as an electron/ion cloud generator for illumination and plasma source applications. A sustained porous cavity resonator (PCR) glow discharge is externally excited using a resonant frequency electromagnetic (EM) wave that excites large internal electric fields. The resonator with a Q of 300 amplifies the incident electric field by factors of about 100 causing a breakdown of the neutral gas inside the sphere. The rise time of the fields inside the sphere is Q times the wave period. A glowing plasma ball is sustained around the point where the maximum electric fields exceed the plasma-discharge threshold for the low-pressure gas inside the resonator. After the EM pump field is removed, the plasma light source is rapidly quenched. The externally driven spherical PCR was fabricated from a theoretical design of the PCR for a laboratory demonstration of the plasma ball generation system. Using both theory and experiment, basic research has been applied to understand: 1) the EMs of resonator excitation and amplification; 2) the generation of light by glow radio frequency discharge; and 3) the effect of background neutral density of the size and intensity of the glowing plasma clouds. For this study, plasma resonators were constructed for the spherical TM101 and TE101 modes and a TE011 circular-cylindrical cavity. All PCR structures provide the ability to confine a plasma into a desired spatial shape without magnetic fields.

New stimulated electromagnetic emission experiment at EISCAT

Observations of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power high frequency HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating Magnetized Stimulated Brillouin scatter MSBS and Stimulated Ion Bernstein scatter SIBS in the SEE spectrum. Narrowband SEE features have not been observed at EISCAT before. Narrowband MSBS spectrums are compared to such behavior previously observed at HAARP. Preliminary analyses of SEE data show observation of ion acoustic emission lines due to stimulated Brillouin scatter during the 2012 July EISCAT campaign. For varying heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics whereas electron temperature enhancement weakens measured by EISCAT/UHF radar.

Large area sea mapping with Ground-Ionosphere-Ocean-Space (GIOS)

The GIOS program has conducted HF scatter and ionosphere propagation tests to show that a single HF transmitter can illuminate greater than 1000 km of ocean surface and scatter waves to single satellite in low earth orbit. The receiver in orbit samples the HF illuminated area to measure Brag scatter from the ocean with signals that pass through the ionosphere. The Doppler shifts and group delays map to specific points on the ocean surface at each point in the satellite orbit. Using the theory of ocean scatter, both coherent (specular) and incoherent (Bragg) scatter components at HF frequency provides bistatic sampling of global ocean surface. Data based models of the waveheight spectrum have been used in simulations to validate this concept. Experimental tests with the HF transmitter of ROTHR/VA and space based receiver of ePOP/RRI have provided data that were collected in April 2015. Actual interpretation in of the satellite measurements in terms of ocean surface parameters is in progress. A practical GIOS system will require measurements from a spacecraft flying below the ionosphere. For this purpose, the Naval Research Laboratory has designed a satellite called CARINA which will orbit the earth at an altitude of 200 to 250 km for 60 days.

Stimulated Brillouin scattering in magnetized ionospheric plasmas

We compare observations of Stimulated Brillouin scattering produced during ionospheric modification experiments using ground-based high-power high frequency HF radio waves at both the High Frequency Active Auroral Research Program (HAARP) and the European Incoherent scatter (EISCAT).

Investigation of Stimulated Electromagnetic Emission SEE during second electron gyro-harmonic heating

Features in the Stimulated Electromagnetic Emission (SEE) spectrum during heating near the second electron gyro-harmonic frequency have recently attracted significant attention due to their possible connection to artificial airglow and artificially generated ionization layers. Experimentally, three new phenomenologically related spectral features within 1 kHz of the heater frequency have been recently discovered: (1) discrete narrowband spectral structures ordered by ion gyro-frequency, (2) broadband features with power spectral density maximum near 500 Hz and (3) the broadband features with embedded ion gyro-harmonic structures.

Transmitter power studies on meteor radar head echo returns

Meteor “head echo” intensities are typically recorded by high-power large-aperture (HPLA) radar systems. These meteor observations have been analyzed extensively to measure parameters such as Doppler velocities, composition and mass estimates. The majority of observations conducted with these radar instruments utilize the maximum available transmitter power in an attempt to obtain the highest meteor flux rate. But there are not direct power law studies on the role of transmitter power and the received backscatter signal. We present observations from three HPLAs to better assess this effect. These results are vital to estimating the Earths total meteor flux.