Fritz Creek, AK, United States
Fritz Creek, AK, United States

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Pedersen T.,Air Force Research Lab | McCarrick M.,Marsh Creek LLC | Reinisch B.,University of Massachusetts Lowell | Watkins B.,University of Alaska Fairbanks | And 2 more authors.
Annales Geophysicae | Year: 2011

Artificial ionospheric plasmas descending from the background F-region have been observed on multiple occasions at the High Frequency Active Auroral Research Program (HAARP) facility since it reached full 3.6 MW power. Proximity of the transmitter frequency to the 2nd harmonic of the electron gyrofrequency (2 fce) has been noted as a requirement for their occurrence, and their disappearance after only a few minutes has been attributed to the increasing frequency mismatch at lower altitudes. We report new experiments employing frequency sweeps to match 2 fce in the artificial plasmas as they descend. In addition to revealing the dependence on the 2 fce resonance, this technique reliably produces descending plasmas in multiple transmitter beam positions and appears to increase their stability and lifetime. High-speed ionosonde measurements are used to monitor the altitude and density of the artificial plasmas during both the formation and decay stages. © 2011 Author(s).


Hysell D.L.,Cornell University | Nossa E.,Cornell University | McCarrick M.,Marsh Creek LLC
Radio Science | Year: 2010

Ionospheric modification experiments have been carried out using the HAARP facility along with a 30 MHz coherent scatter radar imager in Alaska to examine properties of artificial E region field-aligned plasma density irregularities (FAIs). In one set of experiments, the RF emission power was varied gradually in order to determine the threshold electric field for irregularity generation. A threshold O mode peak electric field amplitude of 170-195 mV/m at an altitude of 99 km and a heating frequency of 2.7 MHz was identified based on the full-wave formalism of Thidé and Lundborg (1986). In another, the pump frequency was varied gradually to investigate the suppression of the FAIs at frequencies near the second electron gyroharmonic frequency (2Ωe). Coherent echoes were found to be suppressed for pump frequencies in an asymmetric band 40-50 kHz wide around 2Ωe but only for irregularities driven marginally above threshold. Theoretical context for these results is provided. Copyright 2010 by the American Geophysical Union.


Hysell D.L.,Cornell University | Nossa E.,Cornell University | McCarrick M.,Marsh Creek LLC
Radio Science | Year: 2011

Ionospheric modification experiments have been performed at the High frequency Active Auroral Research Program involving the creation and suppression of artificial field-aligned density irregularities (AFAIs) using O-mode and X-mode continuous wave emissions, respectively. The emission frequencies were offset so that the O-mode upper hybrid interaction height nearly matched the X-mode reflection height in the ionospheric E region. AFAIs created by O-mode heating were observed using a 30 MHz coherent scatter radar imager. Simultaneous X-mode heating was found to suppress the AFAI intensity and increase the threshold power for excitation by approximately a factor of 5 in our experiments. The effects are attributed in part to the broadening of the upper hybrid interaction region and in part to increased O-mode absorption, which reduces the amplitude of the standing wave pattern in that region. Preliminary estimates based on local calculations suggest that the electron temperature in the E region was increased by a factor of about 1.6 in these experiments. Copyright 2011 by the American Geophysical Union.


Moore R.C.,University of Florida | Fujimaru S.,University of Florida | Cohen M.,Stanford University | Golkowski M.,University of Colorado at Denver | McCarrick M.J.,Marsh Creek LLC
Geophysical Research Letters | Year: 2012

[1] Modulated high frequency (HF, 3-10 MHz) heating of the ionosphere in the presence of the auroral electrojet currents is an effective method for generating extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) radio waves. The amplitudes of ELF/VLF waves generated in this manner depend sensitively on the auroral electrojet current strength, which varies with time. In an effort to improve the reliability of ELF/VLF wave generation by ionospheric heating, recent experiments at the Highfrequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska, have focused on methods that are independent of the strength of the auroral electrojet currents. One such potential method is so-called "beat-wave" ELF/VLF generation. Recent experimental observations have been presented to suggest that in the absence of a significant D-region ionosphere (∼60-100 km altitude), an ELF/VLF source region can be created within the F-region ionosphere (∼150-250 km altitude). In this paper, we use a time-ofarrival analysis technique to provide direct experimental evidence that the beat-wave source region is located in the D-region ionosphere, and possibly the lower E-region ionosphere (∼100-120 km altitude), even when ionospheric diagnostics indicate a very weak D-layer. These results have a tremendous impact on the interpretation of recent experimental observations. © 2012. American Geophysical Union. All Rights Reserved.


Samimi A.,Virginia Polytechnic Institute and State University | Scales W.A.,Virginia Polytechnic Institute and State University | Bernhardt P.A.,U.S. Navy | Briczinski S.J.,U.S. Navy | And 2 more authors.
Annales Geophysicae | Year: 2012

Recent observations show that, during ionospheric heating experiments at frequencies near the second electron gyro-harmonic, discrete spectral lines separated by harmonics of the ion-gyro frequency appear in the stimulated electromagnetic emission (SEE) spectrum within 1 kHz of the pump frequency. In addition to the ion gyro-harmonic structures, on occasion, a broadband downshifted emission is observed simultaneously with these spectral lines. Parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and low-frequency ion Bernstein (IB) and oblique ion acoustic (IA) modes is considered responsible for generation of these spectral features. Guided by predictions of an analytical model, a two-dimensional particle-in-cell (PIC) computational model is employed to study the nonlinear processes during such heating experiments. The critical parameters that affect the spectrum, such as whether discrete gyro-harmonic on broadband structures is observed, include angle of the pump field relative to the background magnetic field, pump field strength, and proximity of the pump frequency to the gyro-harmonic. Significant electron heating along the magnetic field is observed in the parameter regimes considered. © Author(s) 2012.


Mahmoudian A.,Virginia Polytechnic Institute and State University | Scales W.A.,Virginia Polytechnic Institute and State University | Bernhardt P.A.,U.S. Navy | Fu H.,Virginia Polytechnic Institute and State University | And 2 more authors.
Radio Science | Year: 2013

Stimulated Electromagnetic Emissions (SEEs), secondary electromagnetic waves excited by high power electromagnetic waves transmitted into the ionosphere, produced by the Magnetized Stimulated Brillouin Scatter (MSBS) process are investigated. Data from four recent research campaigns at the High Frequency Active Auroral Research Program (HAARP) facility is presented in this work. These experiments have provided additional quantitative interpretation of the SEE spectrum produced by MSBS to yield diagnostic measurements of the electron temperature and ion composition in the heated ionosphere. SEE spectral emission lines corresponding to ion acoustic (IA) and electrostatic ion cyclotron (EIC) mode excitation were observed with a shift in frequency up to a few tens of Hz from the pump frequency for heating near the third harmonic of the electron gyrofrequency 3fce. The threshold of each emission line has been measured by changing the pump wave power. The excitation threshold of IA and EIC emission lines originating at the reflection and upper hybrid altitudes is measured for various beam angles relative to the magnetic field. Variation of strength of MSBS emission lines with pump frequency relative to 3fce and 4fce is also studied. A full wave solution has been used to estimate the amplitude of the electric field at the interaction altitude. The estimated instability threshold using the theoretical model is compared with the threshold of MSBS lines in the experiment and possible diagnostic information for the background ionospheric plasma is discussed. Simultaneous formation of artificial field-aligned irregularities (FAIs) and suppression of the MSBS process is investigated. This technique can be used to estimate the growth time of artificial FAIs which may result in determination of plasma waves and physical process involved in the formation of FAIs. Key Points excitation threshold of MSBS lines originated at UH and reflection altitudes Simultaneous observation of formation of FAIs and suppression of MSBS process variation of MSBS emission lines with pump frequency and heater beam angle © 2013. American Geophysical Union. All Rights Reserved.


Bordikar M.R.,Virginia Polytechnic Institute and State University | Scales W.A.,Virginia Polytechnic Institute and State University | Samimi A.R.,Virginia Polytechnic Institute and State University | Bernhardt P.A.,U.S. Navy | And 2 more authors.
Geophysical Research Letters | Year: 2013

This work presents the first observations of unique narrowband emissions ordered near the hydrogen ion (H+) gyrofrequency (fcH) in the stimulated electromagnetic emission spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2fce) during ionospheric modification experiments. The frequency structuring of these newly discovered emission lines is quite unexpected since H+ is known to be a minor constituent in the interaction region which is near 160 km altitude. The spectral lines are typically shifted from the pump wave frequency by harmonics of a frequency about 10% less than fcH (≈ 800 Hz) and have a bandwidth of less than 50 Hz which is near the O+ gyrofrequency fcO. A theory is proposed to explain these emissions in terms of a parametric decay instability in a multi-ion species plasma due to possible proton precipitation associated with the disturbed conditions during the heating experiment. The observations can be explained by including several percent H+ ions into the background plasma. The implications are new possibilities for characterizing proton precipitation events during ionospheric heating experiments. Key Points First observations of H+ ion structuring in SEE during heating experiment Disturbed magnetic conditions imply proton precipitation likely plays a key role Theory is provided to explain emissions by PDI in multi-ion plasma. ©2013. American Geophysical Union. All Rights Reserved.


Samimi A.,Virginia Polytechnic Institute and State University | Scales W.A.,Virginia Polytechnic Institute and State University | Bernhardt P.A.,U.S. Navy | Briczinski S.J.,U.S. Navy | McCarrick M.J.,Marsh Creek LLC
Journal of Geophysical Research: Space Physics | Year: 2014

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. Key Points IB PDI is primarily associated with electron acceleration across magnetic field IA PDI is associated with electron tail heating along the magnetic field Heating is reduced for both PDIs when f0 approaches 2fce ©2013. American Geophysical Union. All Rights Reserved.


Samimi A.,Virginia Polytechnic Institute and State University | Scales W.A.,Virginia Polytechnic Institute and State University | Fu H.,Virginia Polytechnic Institute and State University | Bernhardt P.A.,U.S. Navy | And 2 more authors.
Journal of Geophysical Research: Space Physics | Year: 2013

Stimulated electromagnetic emissions (SEEs) may provide important diagnostic information about space plasma composition, energetics, and dynamics during active experiments in which ground-based high-powered radio waves are transmitted into the ionosphere. The nonlinear plasma processes producing this secondary radiation are not well understood particularly for some recent observations where the transmitter (pump) frequency is near the second harmonic of the electron gyrofrequency. New, more comprehensive, experimental observations of spectral features within 1 kHz of the pump wave frequency are reported here to begin more careful comparisons of the experimental observations and a possible theoretical underpinning, which is also provided. The experimental observations typically show two distinct types of secondary radiation spectra, which are (a) discrete narrowband harmonic spectral structures ordered by the ion gyrofrequency and (b) broadband spectral structure with center frequency near 500 Hz and similar spectral bandwidth. A theoretical model is provided that interprets these spectral features as resulting from parametric decay instabilities in which the pump field ultimately decays into high-frequency upper hybrid/electron Bernstein and low-frequency neutralized ion Bernstein and/or obliquely propagating ion acoustic waves at the upper hybrid interaction altitude. Detailed calculations of the threshold level, growth rate, unstable wave number, and frequency bandwidth of the instabilities are provided for comparisons with experimental observations. An assessment of the effect of the critical instability parameters are provided including pump electric field strength, proximity of the pump frequency to the electron gyrofrequency and pump electric field geometry. The model shows quite reasonable agreement with the experimental observations. Further discussions are provided of connections with past observed SEE spectral features and potential new diagnostic information provided by these newly categorized spectra. © 2012. American Geophysical Union. All Rights Reserved.


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Marsh Creek LLC | Date: 2012-05-15

Generator sets consisting primarily of diesel and gas powered electric generators, sold pre-packaged in portable prefabricated, insulated and acclimatized buildings.

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