Multi-frequency HF radar measurements of artificial F-region field-aligned irregularities

Senior, Andrew; Borisov, N. D.; Kosch, M. J.; Yeoman, T. K.; Honary, F.; Rietveld, M. T.

doi:10.5194/angeo-22-3503-2004

Cited by 20 publications

(22 citation statements)

References 27 publications

(39 reference statements)

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“…Previous studies by Jones et al (1984) and Robinson (1989) found e-folding scale lengths of 20 and 52 km, respectively. Although the results of Robinson et al (1989) do not necessarily support our findings, the figure of 20 km, obtained by both Senior et al (2004) and Jones et al (1984), provides evidence that the upper E-/lower F-region field-aligned density irregularities do not extend high enough to reach the region from where CUTLASS backscatter is usually observed. This supports the hypothesis that the SPEAR-enhanced backscatter does not originate from those F-region altitudes consistent with ray-tracing studies and from where previous SPEARenhanced CUTLASS backscatter has been observed.…”

Section: Discussioncontrasting

confidence: 49%

“…Since the irregularities are elongated and extend along the field lines, it is instructive to see whether, although the irregularities may be generated in the upper E-/lower F-region, the backscatter from them may originate from higher altitudes. Senior et al (2004), who followed on from studies undertaken previously (Jones et al 1984;Robinson et al, 1989), investigated the altitudinal extent of RF-induced artificial field-aligned irregularities and determined that they had e-folding scale lengths of approximately 20 km. Previous studies by Jones et al (1984) and Robinson (1989) found e-folding scale lengths of 20 and 52 km, respectively.…”

Section: Discussionmentioning

confidence: 99%

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EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere

2007

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Abstract. The Space Plasma Exploration by Active Radar (SPEAR) facility has successfully operated in the high-power heater and low-power radar modes and has returned its first results. The high-power results include observations of SPEAR-induced ion and plasma line spectral enhancements recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. These SPEAR-enhanced spectra possess features that are consistent with excitation of both the purely growing mode and the parametric decay instability. In this paper, we present observations of upper and lower E-region SPEAR-induced ion and plasma line enhancements, together with F-region spectral enhancements, which indicate excitation of both instabilities and which are consistent with previous theoretical treatments of instability excitation in sporadic E-layers. In agreement with previous observations, spectra from the lower Eregion have the single-peaked form characteristic of collisional plasma. Our observations of the SPEAR-enhanced E-region spectra suggest the presence of variable drifting regions of patchy overdense plasma, which is a finding also consistent with previous results.

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Section: Discussioncontrasting

confidence: 49%

Section: Discussionmentioning

confidence: 99%

EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere

2007

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“…When the radar beam is orientated in a less perpendicular manner, not all of the scattered signal will be received implying an apparent weakening of the striations [Senior et al, 2004]. Altering the radar frequency slightly to counteract the change in refraction would correct this.…”

Section: Resultsmentioning

confidence: 99%

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

et al. 2013

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[1] We test the existing theories regarding the thresholds for the parametric decay instability (PDI), the oscillating two-steam instability (OTSI), and the thermal parametric instability (TPI) using the European Incoherent Scatter (EISCAT) facility's ionospheric heater. In these processes, the pump wave can couple to various electrostatic waves in the F layer ionosphere, which can be observed using the EISCAT UHF radar (PDI and OTSI) or by HF radar (TPI). On 19 October 2012, the heater power was stepped from 0.5 MW to 100 MW effective radiated power in seven steps using a 1 min on, 1 min off cycle. We use an electric field model, taking into account D region absorption, to compare theory with our observations. In all three cases, we find good agreement. In addition, the growth of striations formed during the TPI causes anomalous absorption of the heater wave, which we observe as decreased UHF ion line and plasma line backscatter power. We show evidence that heating for a prolonged period of time reduces the UHF ion line intensity throughout the experiment.Citation: Bryers, C. J., M. J. Kosch, A. Senior, M. T. Rietveld, and T. K. Yeoman (2013), The thresholds of ionospheric plasma instabilities pumped by high-frequency radio waves at EISCAT,

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“…Here backscatter power and elevation angle of arrival calculated from a cross correlation between signals detected on the main radar array and the interferometer array are used. The accuracy of these elevation angles has been verified through a detailed calibration of the angles measured at a wide range of frequencies over a 1 2 -hop Hankasalmi-Tromsø path (see the experiment described in Senior et al, 2004), and through a comparison of the data recorded with raytrace calculations through a model ionosphere constrained by measurements taken from the EISCAT dynasonde, close to the midpoint of the Hankasalmi-SPEAR propagation path. A schematic of 1 1 2 -hop HF radar propagation paths to the ionosphere above the heating facilities is presented in Fig.…”

Section: Instrumentationmentioning

confidence: 99%

Mapping ionospheric backscatter measured by the SuperDARN HF radars – Part 2: Assessing SuperDARN virtual height models

et al. 2008

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Abstract. The Super Dual Auroral Radar Network (Super-DARN) network of HF coherent backscatter radars form a unique global diagnostic of large-scale ionospheric and magnetospheric dynamics in the Northern and Southern Hemispheres. Currently the ground projections of the HF radar returns are routinely determined by a simple rangefinding algorithm, which takes no account of the prevailing, or indeed the average, HF propagation conditions. This is in spite of the fact that both direct E-and F-region backscatter and 1 1 2 -hop E-and F-region backscatter are commonly used in geophysical interpretation of the data. In a companion paper, Chisham et al. (2008) have suggested a new virtual height model for SuperDARN, based on average measured propagation paths. Over shorter propagation paths the existing rangefinding algorithm is adequate, but mapping errors become significant for longer paths where the roundness of the Earth becomes important, and a correct assumption of virtual height becomes more difficult. The SuperDARN radar at Hankasalmi has a propagation path to high power HF ionospheric modification facilities at both Tromsø on a 1 2 -hop path and SPEAR on a 1 1 2 -hop path. The SuperDARN radar at Þykkvibaer has propagation paths to both facilities over 1 1 2 -hop paths. These paths provide an opportunity to quantitatively test the available SuperDARN virtual height models. It is also possible to use HF radar backscatter which has been artificially induced by the ionospheric heaters as an accurate calibration point for the Hankasalmi elevation angle of arrival data, providing a range correction algorithm for the SuperDARN radars which directly uses elevation angle. These developments enCorrespondence to: T. K. Yeoman (tim.yeoman@ion.le.ac.uk) able the accurate mappings of the SuperDARN electric field measurements which are required for the growing number of multi-instrument studies of the Earth's ionosphere and magnetosphere.

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Multi-frequency HF radar measurements of artificial F-region field-aligned irregularities

Cited by 20 publications

References 27 publications

EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere

EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

Mapping ionospheric backscatter measured by the SuperDARN HF radars – Part 2: Assessing SuperDARN virtual height models

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