Some ionosonde observations of ionosphere modification by very high power, high frequency ground-based transmission

Utlaut, W. F.; Violette, E. J.; Paul, Adolf K.

doi:10.1029/ja075i031p06429

Cited by 49 publications

(14 citation statements)

References 5 publications

(2 reference statements)

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“…The long wavelength ('-'1 kin) field-aligned irregularities giving rise to artificial spread F (Utlaut et al, 1970;Utlaut and Violette, 1972;Wright, 1973) could not, however, be explained in terms of the above instability process. The causative mechanism for the generation of long wavelength irregularities remained obscure for quite a while and is now attributed to either a thermal self-focusing mechanism Thome and Perkins, 1974) or the alternative mechanisms of stimulated Brillouin scattering (Cragin and Fejer, 1974) and stimu-This paper is not subject to U.S. copyright.…”

Section: Introductionmentioning

confidence: 93%

Preliminary results of scintillation measurements associated with ionosphere Heating and possible implications for the solar power satellite

Basu¹,

Johnson²,

Klobuchar³

et al. 1980

Geophysical Research Letters

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Initial results of ground and air‐borne measurements of 250 MHz scintillations associated with ionospheric heating in both the overdense (heater frequency below the critical frequency) and underdense cases (heater frequency above the critical frequency) by the high‐power, high‐frequency transmitter at Platteville, Colorado are discussed. The ground stations and the geostationary satellites used in the experiment were so chosen that it was possible to explore the artificial irregularities both within and outside the central heated volume. One ground station was able to view LES‐8 in a field‐aligned direction while, at a second ground station, spaced receiver scintillation measurements were available using FLEETSATCOM. The instrumented aircraft recorded both phase and amplitude scintillations and flew missions in the north‐south and east‐west directions to define the region of artificial irregularities. The preliminary results indicate a prompt excitation of artificial irregularities in the overdense case causing 2‐10 dB scintillation at 244‐249 MHz and a lifetime of the order often minutes. In the underdense case, on the other hand, the response was delayed and effects were observed to be on the order of 1‐3 dB at 250 MHz, although a unique event of 10 dB scintillation was recorded along the field‐aligned propagation path. The presence of such scintillations in the underdense case and their implications for the proposed Solar Power Satellite (SPS) are indicated in the paper.

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Section: Introductionmentioning

confidence: 93%

Preliminary results of scintillation measurements associated with ionosphere Heating and possible implications for the solar power satellite

Basu¹,

Johnson²,

Klobuchar³

et al. 1980

Geophysical Research Letters

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“…Ionospheric modification experiments have been conducted since the early 1970s using high-power highfrequency (HF) radio waves to artificially modify the ionosphere [Utlaut et al, 1970;Gordon et al, 1971]. Two important observations made during these experiments entail the production of enhanced plasma waves in the ionosphere [Wong and Taylor, 1971;Carlson et al, 1972] and the excitation of artificial geomagnetic field-aligned irregularities (AFAIs) [Fialer, 1974].…”

Section: Introductionmentioning

confidence: 99%

Simultaneous measurements of HF‐enhanced plasma waves and artificial field‐aligned irregularities at Arecibo

Noble¹,

Djuth²

1990

J. Geophys. Res.

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Two radar systems with beams intersecting in the HF‐modified F region were used to simultaneously measure HF‐enhanced plasma lines (HFPLs) and artificial geomagnetic field‐aligned irregularities (AFAIs). These measurements were made with the high‐power HF facility located near the Arecibo Observatory, Arecibo, Puerto Rico. The Arecibo 430‐MHz radar was used for the HFPL observations, and a portable 49.92‐MHz backscatter radar was deployed on the island of Guadeloupe to monitor the AFAIs. The experiment was designed to examine the degree to which HF‐induced plasma turbulence influences the development of AFAIs. When the HF beam is stepped up in power, sustained HFPLs and AFAIs are first observed at the same HF power level, indicating that ponderomotively driven instabilities may be involved in the early time development of AFAIs. As the HF power is increased, the HFPL backscatter power begins to saturate at ∼70 MW effective radiated power (ERP). However, the backscatter from AFAIs is linearly dependent on HF power, even at the highest (120 MW ERP) HF power levels available at Arecibo. This suggests that additional processes may contribute to the development of AFAIs. For example, ponderomotively driven instabilities may give rise to weak geomagnetic field‐aligned irregularities that are subsequently driven unstable by processes excited near the upper hybrid resonance. It is also likely that AFAIs greatly impact the development of HF‐induced plasma turbulence at late times (>1 s) following HF turn‐on. Once the ionosphere is preconditioned by high‐power HF modifications, AFAIs and HFPLs can be simultaneously sustained at a much lower HF power level than that needed to originally excite them. The nature of the preconditioning process is currently not well understood. New theoretical initiatives are clearly needed to guide future experimental activity in this area.

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“…Over the last decade and a half a continuing effort has been made to study artificial field aligned irregularities (AFAIs) generated by high-power high-frequency (HF) radio waves. Initial experiments designed to explore HF-induced phenomena were conducted at Platteville, Colorado [Utlaut et al, 1970], and shortly thereafter at Arecibo, Puerto Rico [' Gordon et al, 1971]. Many of the early experimental and theoretical discoveries of this era are presented in the November 1974 issue of Radio Science.…”

Section: Introductionmentioning

confidence: 99%

Multiple frequency radar observations of high‐latitude E region Irregularities in the HF modified ionosphere

Noble¹,

Djuth²,

Jost³

et al. 1987

J. Geophys. Res.

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In September 1983, experiments were conducted in Scandinavia using the high‐power heating facility near Tromsø, Norway, The purpose of the HF ionospheric modification experiments was to investigate the behavior of artificially produced E region irregularities at auroral latitudes. The majority of observations were made with backscatter radars operating at 46.9 and 143.8 MHz, but limited observations were also made at 21.4 and 140.0 MHz. These radars are sensitive to irregularities having scale lengths of between 1 and 7 m across the geomagnetic field lines. The growth and decay of the irregularities are scale length dependent with the shorter lengths growing and dissipating more rapidly than the longer lengths (e‐folding growth times = 10¹–10² ms; decay times = 10²–10³ ms). During periods of full power ordinary mode heating, irregularities having peak cross sections of 104 m² at 46.9 MHz and 105 m² at 143.8 MHz are observed. However, the cross sections normally measured are 1 to 2 orders of magnitude smaller than the peak values. The cross sections are nonlinearly dependent on the HF power and begin to saturate at levels greater than 50–75 percent of full power. Past E and F region data from Arecibo are used in conjunction with the Tromsø measurements to ascertain the relative roles played by various mechanisms in exciting irregularities. In the E region, the results tend to favor those instability processes which operate at the upper hybrid resonance level (e.g., thermal parametric and resonance instabilities) over those that operate at the reflection level (e.g., parametric decay instability). However, it is likely that any of the mechanisms studied could at times contribute to irregularity production in the E region. At F region altitudes, the findings show support for the parametric decay, four‐wave thermal parametric, and resonance instabilities. The aspect sensitivity of the irregularities is measured using the 140.0 and 143.8 MHz radars. The results indicate a reduction in echo strength of 8–14 dB/deg for geometries that do not match those for specular reflection.

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Some ionosonde observations of ionosphere modification by very high power, high frequency ground-based transmission

Cited by 49 publications

References 5 publications

Preliminary results of scintillation measurements associated with ionosphere Heating and possible implications for the solar power satellite

Preliminary results of scintillation measurements associated with ionosphere Heating and possible implications for the solar power satellite

Simultaneous measurements of HF‐enhanced plasma waves and artificial field‐aligned irregularities at Arecibo

Multiple frequency radar observations of high‐latitude E region Irregularities in the HF modified ionosphere

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