Thermal Cavitons

Dysthe, Kristian B.; Mjølhus, E.; Pécseli, H. L.; Rypdal, Kristoffer

doi:10.1088/0031-8949/1982/t2b/040

Cited by 107 publications

(103 citation statements)

References 20 publications

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“…The FAIs we observe are understood to be produced at the upper-hybrid resonance height (Grach et al, 1977;Das and Fejer, 1979;Grach et al, 1981;Dysthe et al, 1982Dysthe et al, , 1983. On the basis of calculations outlined below, we expect Omode radiation from HAARP to penetrate to this height for both zenith and magnetic zenith pointing and to generate FAIs with roughly comparable characteristics in either case.…”

Section: Zenith and Magnetic Zenith Pointingmentioning

confidence: 79%

“…6, it appears that irregularities are not produced until the heater power reaches about one fifth its maximum while irregularities can be maintained virtually until the time heating is discontinued. Grach et al (1978) and Dysthe et al (1982) predicted this kind of hysteresis, arguing that it should be possible to maintain irregularities with less power than is necessary to excite them because differential heating by the the resonance instability increases in efficiency with the intensity of the irregularities. Some preliminary evidence for their hypothesis was available at that time (Erukhimov et al, 1978;Stubbe et al, 1982;Kopka et al, 1982).…”

Section: Hysteresis and Striation Formationmentioning

confidence: 99%

“…Excitation thresholds for the thermal oscillating two-stream instability, which is thought to initiate the resonance instability, were predicted by Grach et al (1977), Das and Fejer (1979), and Dysthe et al (1983). Grach et al (1978) and Dysthe et al (1982) also anticipated a hysteresis effect associated with the resonance instability and wave trapping, such that irregularities can be maintained by pump waves with amplitudes below their excitation threshold. Hysteresis was Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

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Radar observations of artificial E-region field-aligned irregularities

et al. 2009

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Abstract. Artificial E region field aligned plasma density irregularities (FAIs) were generated using HAARP in four different experimental modes and observed with a coherent scatter radar imager located 450 km to the southwest where it could detect field-aligned backscatter. The experiments were conducted in July of 2008, during the Polar Aeronomy and Radio Science Summer School (PARS), during quiet conditions in the daytime when the E layer was dense and absorption was modest. The echoes observed during zenith and magnetic zenith heating experiments were deflected from their nominally anticipated horizontal positions toward the midpoint position. The occurrence of hysteresis when heating with amplitude modulated pulses implied the development of the resonance instability, although the threshold for the onset of instability appeared to be higher than what has been predicted theoretically. Heating experiments involving pump frequencies slightly above and below the second electron gyroharmonic frequency produced no significant differences in the observed echoes. Finally, heating with a pump frequency slightly above the E region critical frequency appears to have produced FAIs at two distinct altitudes where the upper-hybrid resonance condition could be satisfied.

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Section: Zenith and Magnetic Zenith Pointingmentioning

confidence: 79%

Section: Hysteresis and Striation Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Radar observations of artificial E-region field-aligned irregularities

et al. 2009

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“…Artificial FAIs are generally believed to be generated by thermal parametric instabilities (TPIs) which form at altitudes slightly above the upper hybrid resonance height where the pump frequency is the Pythagorean sum of the plasma frequency and the electron gyrofrequency (Grach et al, 1977;Das and Fejer, 1979;Grach et al, 1981;Dsythe et al, 1982;Dsythe et al, 1983). In the nonlinear stage of evolution, the TPI goes over to the resonance instability developed by Gurevich (1975, 1977) and expanded upon by Inhester (1982).…”

Section: Discussionmentioning

confidence: 99%

“…Upper-hybrid waves can also be generated through the linear mode conversion of the pump wave in the vicinity of existing density striations (Mishin et al, 2004(Mishin et al, , 2005. Upper hybrid wave trapping within the striations leads to ohmic heating, deepening of the striations, and thermal parametric instability (Grach et al, 1981;Dsythe et al, 1982). Subsequent wave growth leads to explosive growth through resonance instability (Vas'kov and Gurevich, 1977).…”

Section: Discussionmentioning

confidence: 99%

30 MHz radar observations of artificial E region field-aligned plasma irregularities

Hysell

2008

Ann. Geophys.

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Abstract. Artificial E region field aligned irregularities (FAIs) have been observed during heating experiments at the HAARP facility using a new 30 MHz coherent scatter radar imager deployed near Homer, Alaska. Irregularities were observed during brief experiments on three quiet days in July and August, 2007, when the daytime E region critical frequency was close to 3 MHz. Irregularities were consistently generated and detected during experiments with O-mode HF pumping on zenith with a 1-min on, 1-min off CW modulation. The scattering cross sections, rise, and fall times of the echoes were observed as well as their spectral properties. Results were found to be mainly in agreement with observations from other mid-and high-latitude sites with some discrepancies. Radar images of the irregularity-filled volume on one case exhibited clear variations in backscatter power and Doppler shift across the volume. The images furthermore show the emergence of a small irregularity-filled region to the south southwest of the main region in the approximate direction of magnetic zenith.

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Numerical study of anomalous absorption of O mode waves on magnetic field‐aligned striations

Eliasson

Papadopoulos

2015

Geophysical Research Letters

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Simple expressions that describe mode conversion and anomalous absorption of ordinary (O) mode waves injected at angles between the vertical and magnetic zenith to upper hybrid (UH) oscillations in the presence of field‐aligned density striations are presented. The absorption takes place in a region above the UH resonance layer where the striations allow trapped eigenmodes, leading to excitation of large‐amplitude UH waves. The derivation of the expressions is guided by dimensional analysis and numerical simulations. The results are relevant in interpreting high‐latitude heating experiments where anomalous absorption due to striations plays a crucial role.

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Thermal Cavitons

Cited by 107 publications

References 20 publications

Radar observations of artificial E-region field-aligned irregularities

Radar observations of artificial E-region field-aligned irregularities

30 MHz radar observations of artificial E region field-aligned plasma irregularities

Numerical study of anomalous absorption of O mode waves on magnetic field‐aligned striations

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