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

Hysell, D. L.

doi:10.5194/angeo-26-117-2008

Cited by 14 publications

(16 citation statements)

References 39 publications

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“…This phenomenon, which suggests outward expansion, was also noted by Hysell (2008) and seems to be present in either pointing position.…”

Section: Observationsmentioning

confidence: 84%

“…The imaging radar is capable of resolving two-dimensional fine structure in backscatter from the common volume with kilometric resolution. Specifications for the radar and its operating mode were given by Hysell (2008). The HAARP ionosonde and riometer were also operating for the study.…”

Section: Observationsmentioning

confidence: 99%

“…New developments in the area of aperture synthesis radar imaging allow the creation of similarly revealing images from coherent scatter radar data (Hysell and Chau, 2006). A new imaging radar system located near Homer, Alaska, offers a powerful new diagnostic for E region FAI research at HAARP (Hysell, 2008).…”

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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“…This phenomenon, which suggests outward expansion, was also noted by Hysell (2008) and seems to be present in either pointing position.…”

Section: Observationsmentioning

confidence: 84%

Section: Observationsmentioning

confidence: 99%

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Radar observations of artificial E-region field-aligned irregularities

et al. 2009

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“…Reception is performed using 6 spaced antenna arrays, providing 15 approximately coplanar, nonredundant baselines for interferometry. Additional details about the system and some of the diagnostics it can perform were given by Hysell (2008).…”

Section: Observationsmentioning

confidence: 99%

“…The prediction has especially important implications for artificial E region FAIs, which are routinely and often necessarily (in view of the low E-region critical frequency) generated using pump frequencies below and often well below 2 e (e.g. Fialer, 1974;Hysell, 2008). For example, the FAIs observed by Nossa et al (2009) were mainly generated using a pump frequency of just 2.75 MHz.…”

Section: Introductionmentioning

confidence: 99%

Artificial E-region field-aligned plasma irregularities generated at pump frequencies near the second electron gyroharmonic

Hysell

Nossa

2009

Ann. Geophys.

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Abstract. E region ionospheric modification experiments have been performed at HAARP using pump frequencies about 50 kHz above and below the second electron gyroharmonic frequency. Artificial E region field-aligned plasma density irregularities (FAIs) were created and observed using the imaging coherent scatter radar near Homer, Alaska. Echoes from FAIs generated with pump frequencies above and below 2 e did not appear to differ significantly in experiments conducted on summer afternoons in 2008, and the resonance instability seemed to be at work in either case. We argue that upper hybrid wave trapping and resonance instability at pump frequencies below the second electron gyroharmonic frequency are permitted theoretically when the effects of finite parallel wavenumbers are considered. Echoes from a sporadic E layer were observed to be somewhat weaker when the pump frequency was 50 kHz below the second electron gyroharmonic frequency. This may indicate that finite parallel wavenumbers are inconsistent with wave trapping in thin sporadic E ionization layers.

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Sporadic E ionization layers observed with radar imaging and ionospheric modification

Hysell

Munk

McCarrick

2014

Geophysical Research Letters

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Sporadic E ionization layers have been observed in the daytime subauroral ionospheric E layer by a 30 MHz radar in Alaska. The radar detects coherent backscatter from meter-scale field-aligned plasma density irregularities. The irregularities were generated by ionospheric modification-by the emission of strong HF electromagnetic waves directly beneath the layers-making the layers visible to the radar. Aperture-synthesis methods are used to generate imagery of the layers from the radar data. The layers are patchy, with patches organized along fronts spaced by tens of kilometers and propagating slowly toward the southwest. Similar, naturally occurring layers are commonly observed at middle latitudes at night in the absence of ionospheric modification. That the patchy layers can be found at high magnetic latitudes during the day argues that they are most likely produced through the interaction of the ionospheric layer with neutral atmospheric waves and instabilities. Attenuation of the radar echoes when the HF emission frequency exceeded the third harmonic of the electron gyrofrequency was observed and is discussed.

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

Cited by 14 publications

References 39 publications

Radar observations of artificial E-region field-aligned irregularities

Radar observations of artificial E-region field-aligned irregularities

Artificial E-region field-aligned plasma irregularities generated at pump frequencies near the second electron gyroharmonic

Sporadic E ionization layers observed with radar imaging and ionospheric modification

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