scholarly journals Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

2015 ◽  
Vol 33 (8) ◽  
pp. 983-990 ◽  
Author(s):  
H. Y. Fu ◽  
W. A. Scales ◽  
P. A. Bernhardt ◽  
S. J. Briczinski ◽  
M. J. Kosch ◽  
...  
Keyword(s):  
High Frequency ◽  
Brillouin Scattering ◽  
Electromagnetic Emission ◽  
Spectral Lines ◽  
Radio Waves ◽  
Pump Frequency ◽  
Incoherent Scatter ◽  
Ionospheric Modification ◽  
Stimulated Brillouin ◽  
Uhf Radar

Abstract. 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 narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

scholarly journals Saturation and hysteresis effects in ionospheric modification experiments observed by the CUTLASS and EISCAT radars

2006 ◽  
Vol 24 (2) ◽  
pp. 543-553 ◽  
Author(s):  
D. M. Wright ◽  
J. A. Davies ◽  
T. K. Yeoman ◽  
T. R. Robinson ◽  
H. Shergill
Keyword(s):  
High Frequency ◽  
Radio Waves ◽  
Heating Facility ◽  
Ionospheric Modification ◽  
Radiated Power ◽  
Pump Waves ◽  
Hybrid Waves ◽  
Electron Density Irregularities ◽  
Uhf Radar ◽  
Field Aligned Irregularities

Abstract. The results of high latitude ionospheric modification experiments utilising the EISCAT heating facility at Tromsø are presented. As a result of the interaction between the high power pump waves and upper hybrid waves in the ionosphere, field-aligned electron density irregularities are artificially excited. Observations of these structures with the CUTLASS coherent HF radars and the EISCAT incoherent UHF radar exhibit hysteresis effects as the heater output power is varied. These are explained in terms of the two-stage mechanism which leads to the growth of the irregularities. Experiments which involve preconditioning of the ionosphere also indicate that hysteresis could be exploited to maximise the intensity of the field-aligned irregularities, especially where the available heater power is limited. In addition, the saturation of the irregularity amplitude is considered. Although, the rate of irregularity growth becomes less rapid at high heater powers it does not seem to fully saturate, indicating that the amplification would continue beyond the capabilities of the Tromsø heater - currently the most powerful of its kind. It is shown that the CUTLASS radars are sensitive to irregularities produced by very low heater powers (effective radiated powers <4 MW). This fact is discussed from the perspective of a new heating facility, SPEAR, located on Spitzbergen and capable of transmitting high frequency radio waves with an effective radiated power ~10% of that of the Tromsø heater (28MW).

scholarly journals Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer

2006 ◽  
Vol 24 (7) ◽  
pp. 1819-1827 ◽  
Author(s):  
E. D. Tereshchenko ◽  
R. Yu. Yurik ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
B. Isham ◽  
...  
Keyword(s):  
High Frequency ◽  
Source Region ◽  
Emission Spectra ◽  
Electromagnetic Emission ◽  
Spectral Features ◽  
Frequency Range ◽  
Pump Frequency ◽  
Ionospheric Modification ◽  
Stimulated Electromagnetic Emission ◽  
Magnetic Zenith

Abstract. A high frequency (HF) ionospheric modification experiment was carried out between 25 September and 8 October 2004, using the EISCAT HF transmitter located near Tromsø, Norway. During this experiment the spectra of the stimulated HF sideband waves (stimulated electromagnetic emission or SEE) induced by the HF pump were observed using an interferometer consisting of three spaced receiving antennas with baselines both along and perpendicular to the meridian, and a multi-channel coherent receiver, installed in the vicinity of the HF facility. The transmitter operated at 4040kHz and its antenna beam was scanned to angles of 0°, 7°, 14°, and 21° south from vertical, pausing 4min at each position. This paper focuses on features of the downshifted peak (DP) emission, which has not been as thoroughly studied as many of the other SEE spectral features observable within the EISCAT pump frequency range. It was found that the signal-weighted direction of the DP source region remained within 5° of magnetic zenith as the HF beam was tilted between 0 and 21° south of vertical.

scholarly journals Variation in altitude of high-frequency enhanced plasma line by the pump near the 5th electron gyro-harmonic

2019 ◽  
Author(s):  
Jun Wu ◽  
Jian Wu ◽  
Michael T. Rietveld ◽  
Ingemar Haggstrom ◽  
Haisheng Zhao ◽  
...  
Keyword(s):  
Electron Temperature ◽  
High Frequency ◽  
Langmuir Wave ◽  
Decisive Role ◽  
Bragg Condition ◽  
Pump Frequency ◽  
Ionospheric Heating ◽  
Lower Altitude ◽  
Incoherent Scatter ◽  
Plasma Line

Abstract. During an ionospheric heating campaign carried out at the European Incoherent Scatter Scientific Association (EISCAT), the ultra high frequency incoherent scatter (IS) radar observed a systematic variation in the altitude of the high-frequency enhanced plasma line (HFPL), which behaves depending on the pump frequency. Specifically, the HFPL altitude becomes lower when the pump lies above the 5th gyro-harmonic. The analysis shows that the enhanced electron temperature plays a decisive role in the descent in the HFPL altitude. That is, on the traveling path of the enhanced Langmuir wave, the enhanced electron temperature can only be matched by the low electron density at a lower altitude so that the Bragg condition can be satisfied, as expected from the dispersion relation of Langmuir wave.

scholarly journals Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic

2005 ◽  
Vol 23 (5) ◽  
pp. 1585-1592 ◽  
Author(s):  
M. J. Kosch ◽  
T. Pedersen ◽  
J. Hughes ◽  
R. Marshall ◽  
E. Gerken ◽  
...  
Keyword(s):  
High Frequency ◽  
Optical Emission ◽  
Particle Interactions ◽  
Auroral Ionosphere ◽  
Radio Waves ◽  
Pump Frequency ◽  
Optical Emissions ◽  
The Third ◽  
Active Experiments ◽  
First Time

Abstract. High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identical to natural aurora. Pumping at electron gyro-harmonic frequencies has special significance as many phenomena change their character. In particular, artificial optical emissions become strongly reduced for the third and higher gyro-harmonics. The High frequency Active Auroral Research Program (HAARP) facility is unique in that it can select a frequency near the second gyro-harmonic. On 25 February 2004, HAARP was operated near the third and passed through the second gyro-harmonic for the first time in a weakening ionosphere. Two novel observations are: firstly, a strong enhancement of the artificial optical emission intensity near the second gyro-harmonic, which is opposite to higher gyro-harmonics; secondly, the optical enhancement maximum occurs for frequencies just above the second gyro-harmonic. We provide the first experimental evidence for these effects, which have been predicted theoretically. In addition, irregular optical structures were created when the pump frequency was above the ionospheric critical frequency.Keywords. Active experiments – Auroral ionosphere – Wave-particle interactions

scholarly journals On ion gyro-harmonic structuring in the stimulated electromagnetic emission spectrum during second electron gyro-harmonic heating

2012 ◽  
Vol 30 (11) ◽  
pp. 1587-1594 ◽  
Author(s):  
A. Samimi ◽  
W. A. Scales ◽  
P. A. Bernhardt ◽  
S. J. Briczinski ◽  
C. A. Selcher ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Electromagnetic Emission ◽  
Spectral Lines ◽  
Critical Parameters ◽  
Pump Field ◽  
Pump Frequency ◽  
Ionospheric Heating ◽  
Background Magnetic Field ◽  
Stimulated Electromagnetic Emission

Abstract. 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.

scholarly journals Spatial observations by the CUTLASS coherent scatter radar of ionospheric modification by high power radio waves

1997 ◽  
Vol 15 (11) ◽  
pp. 1412-1421 ◽  
Author(s):  
G. E. Bond ◽  
T. R. Robinson ◽  
P. Eglitis ◽  
D. M. Wright ◽  
A. J. Stocker ◽  
...  
Keyword(s):  
Horizontal Distance ◽  
Radio Waves ◽  
Heated Region ◽  
Coherent Scatter ◽  
Heating Facility ◽  
Incoherent Scatter ◽  
Ionospheric Modification ◽  
Experimental Campaign ◽  
Scatter Radar ◽  
Field Aligned Irregularities

Abstract. Results are presented from an experimental campaign in April 1996, in which the new CUTLASS (Co-operative UK twin-located Auroral Sounding System) coherent scatter radar was employed to observe artificial field aligned irregularities (FAI) generated by the EISCAT (European Incoherent SCATter) heating facility at Tromsø, Norway. The distribution of backscatter intensity from within the heated region has been investigated both in azimuth and range with the Finland component of CUTLASS, and the first observations of artificial irregularities by the Iceland radar are also presented. The heated region has been measured to extend over a horizontal distance of 170±50km, which by comparison with a model of the heater beam pattern corresponds to a threshold electric field for FAI of between 0.1 and 0.01V/m. Differences between field-aligned and vertical propagation heating are also presented.

Stimulated Brillouin scattering of whistler waves in low-density collisionless plasmas

1986 ◽  
Vol 36 (3) ◽  
pp. 371-377
Author(s):  
S. Guha ◽  
C. Basu
Keyword(s):  
Growth Rate ◽  
Ponderomotive Force ◽  
Brillouin Scattering ◽  
Negative Ions ◽  
Stimulated Brillouin Scattering ◽  
Low Density ◽  
Whistler Waves ◽  
Ionospheric Modification ◽  
Collisionless Plasmas ◽  
Stimulated Brillouin

We present a theoretical investigation of stimulated Brillouin scattering (SBS) of whistler waves in low-density collisionless plasmas in the presence of negative ions and incorporating the effect of the ponderomotive force on electrons. It is found that the growth rate of the excited ion quasi-mode decreases with increasing concentration of negative ions. The effect of negative ions on the SBS of the whistler waves during the ionospheric modification is discussed.

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