Effects of HF heater‐produced ionospheric depletions on the ducting of VLF transmissions: A ray tracing study

Starks, M.

doi:10.1029/2001ja009197

Cited by 13 publications

(17 citation statements)

References 28 publications

(40 reference statements)

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“…Bundles of rays are traced from initial points spread over a 97,200‐point equal‐area grid defined within the ionosphere and with intensities given by the outputs of the transmitter and ionospheric absorption models. As in the work of Starks [2002], no horizontal density gradients are postulated and it is assumed that owing to refraction the wave normals of the upgoing rays are initially aligned with the gradient of the ionospheric density, i.e., in the radial direction. Rays are then traced in the whistler mode into the plasmasphere until they reenter the ionosphere and are presumed lost.…”

Section: Modelsmentioning

confidence: 99%

Illumination of the plasmasphere by terrestrial very low frequency transmitters: Model validation

et al. 2008

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[1] A composite model of wave propagation from terrestrial very low frequency (VLF) transmitters has been constructed to estimate the wave normal angles and fields of whistler mode waves in the plasmasphere. The model combines a simulation of the fields in the Earth-ionosphere waveguide, ionospheric absorption estimates, and geomagnetic field and plasma density models with fully three-dimensional ray tracing that includes refraction, focusing, and resonant damping. The outputs of this model are consistent with those of several previous, simpler simulations, some of which have underlying component models in common. A comparison of the model outputs to wavefield data from five satellites shows that away from the magnetic equator, all of the models systematically overestimate the median field strength in the plasmasphere owing to terrestrial VLF transmitters by about 20 dB at night and at least 10 dB during the day. In addition, wavefield estimates at L < 1.5 in the equatorial region appear to be about 15 dB too low, although measured fields there are extremely variable. Consideration of the models' similarities and differences indicates that this discrepancy originates in or below the ionosphere, where important physics (as yet not conclusively identified) is not being modeled. Adjustment of the low-altitude field estimates downward by constant factors brings the model outputs into closer agreement with satellite observations. It is concluded that past and future use of these widely employed trans-ionospheric VLF propagation models should be reevaluated.

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Section: Modelsmentioning

confidence: 99%

Illumination of the plasmasphere by terrestrial very low frequency transmitters: Model validation

et al. 2008

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“…However, proper inclusion of longitudinal density gradients would involve use of a three‐dimensional ray tracing program, which is beyond the scope of the present work. While such programs do exist and have been used [ Green et al , 2002; Starks , 2002] their use in our analysis is computationally prohibitive in view of the fact that many thousands of rays need to be run to properly construct the wave property tables.…”

Section: Precipitation Hot Spot In Geographic Coordinatesmentioning

confidence: 99%

Temporal signatures of radiation belt electron precipitation induced by lightning‐generated MR whistler waves: 2. Global signatures

Bortnik¹,

Inan²,

Bell³

2006

J. Geophys. Res.

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[1] We use the methodology presented in a companion paper to calculate the temporal and spatial precipitation signatures of energetic radiation-belt electrons due to pitch-angle scattering by magnetospherically reflecting (MR) whistler waves generated by lightning discharges at geomagnetic source latitudes of l s = 25°, 35°, 45°, and 55°. We show precipitated energy and number fluxes, as well as average precipitated energy as a function of time and L-shell for all four l s cases, and then extrapolate the results of the l s = 35°case in longitude to produce a time-sequence of geographic 'hot spots' which are affected by the MR whistler induced electron precipitation. We then discuss the total precipitation in both hemispheres due to the various l s cases. Our major findings are that the precipitation region moves to higher L-shells as a function of time, on short (0.1 sec, at the start of the event) and long (10 sec) timescales, corresponding to the first hop of the wave, and the MR portion of the whistler wave, respectively. There is also structure within the long-timescale precipitation on the order of $1 sec, reflecting the periodic MR of the underlying whistler wave. As l s increases, an additional precipitated flux signature which is more incoherent and discontinuous, begins to form at higher L-shells and later times, due to MR whistler wave reflections from the plasmapause. At lower L-shells, a pronounced maximum occurs in the number flux of $1 keV electrons at L $ 2-3 due to the Landau resonance. The geographic hot spot affected by the precipitation can split into two separate regions per hemisphere, and occur simultaneously in both hemispheres so that up to four distinct precipitation hot spots can occur on the Earth at any instant, driven by a single lightning discharge. We also discuss potential sources of error, and comparison to related modeling efforts, and to observations using a either satellite-borne instruments or ground-based techniques.

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“…Ducted NAU‐generated 28.5 kHz whistler mode was recorded in Trelew, Argentina near the magnetic conjugate point of Arecibo [ Starks et al , 2001]. Ray tracing work by Starks [2002] suggests that significant quantities of radiation from NAU should enter the magnetosphere. However, the occurrence probability of magnetospheric ducts decreases with L‐shell and they had never been observed to occur naturally below L = 1.7, according to Cerisier [1974].…”

Section: Introductionmentioning

confidence: 99%

Electron precipitation from the inner radiation belt above Arecibo

Pradipta

Labno

Lee

et al. 2007

Geophysical Research Letters

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[1] We examine possible correlations between occurrences of nighttime E-region plasma line (PL) enhancements over Arecibo and 40.75 kHz NAU emissions. On the night of January 1 -2, 2006, the experiments were conducted from 22:00 to 6:00 local time (LT). NAU transmitter was initially turned off until 01:45 LT, when continuous operations resumed for the remainder of the experiments. Enhanced PL events lasting <10 s had central frequencies and bandwidths of about 2.5 and 1.5 MHz, respectively, indicating that Arecibo radar detected 2.3 to 8.5 eV suprathermal electrons streaming along geomagnetic fields. The rate of PL event detections increased by a factor of 2.8 after NAU turn-on. We suggest that 40.75 kHz radiation sporadically leaked though local ionosphere, probably abetted by field-aligned irregularities. The radiation propagated in whistler mode into the L = 1.35 inner radiation belt where gyroresonant interactions with trapped 390 keV electrons increased the precipitation rate. Citation: Pradipta, R

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Effects of HF heater‐produced ionospheric depletions on the ducting of VLF transmissions: A ray tracing study

Cited by 13 publications

References 28 publications

Illumination of the plasmasphere by terrestrial very low frequency transmitters: Model validation

Illumination of the plasmasphere by terrestrial very low frequency transmitters: Model validation

Temporal signatures of radiation belt electron precipitation induced by lightning‐generated MR whistler waves: 2. Global signatures

Electron precipitation from the inner radiation belt above Arecibo

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