Quasi‐electrostatic whistler mode wave excitation by linear scattering of EM whistler mode waves from magnetic field‐aligned density irregularities

Foust, F.; Inan, U. S.; Bell, T. F.; Lehtinen, N. G.

doi:10.1029/2010ja015850

Cited by 11 publications

(20 citation statements)

References 25 publications

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“…The 20 dB whistler wave power deficit reported by Starks et al [2008] calls for such modeling efforts. The study by Foust et al [2010] show that the mode conversion of whistler wave to LH waves in the middle altitude can result in 7–10 dB power loss for whistler waves. Our simulations show that the mode conversion in the low‐altitude ionosphere can result in ∼10 dB power loss for whistler waves.…”

Section: Discussionmentioning

confidence: 99%

“…Recent observations [ Starks et al , 2008] from five different spacecraft indicate that the amplitude of the measured VLF signals in the 20 kHz range is lower by more than 20 dB at night and 10 dB during the day than used in the RB models. This has been termed as the “20 dB puzzle” and has been the subject of a number of recent studies [ Foust et al , 2010; Ganguli et al , 2010; Mishin et al , 2010; Bell et al , 2008]. Recent DEMETER plasma wave observations above the NWC VLF transmitter at 19.8 kHz also indicate that the nominal 20 dB intensity decrease occurs at altitudes lower than 700 km.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, there have been several studies [ Foust et al , 2010; Mishin et al , 2010] to identify the loss processes to account for the attenuation of whistler waves in the ionosphere. Mishin et al [2010] studied the nonlinear VLF effects (parametric instabilities) driven by intense VLF pump waves in the topside ionosphere above powerful VLF transmitters such as the NWC VLF transmitter in Australia.…”

Section: Introductionmentioning

confidence: 99%

“… Parrot et al [2007] observed the presence of ionospheric irregularities at altitude ∼700 km above NWC transmitter during VLF wave transmission. Motivated by this work, Foust et al [2010] presented studies of the “20 dB deficit.” To estimate the power loss of VLF whistler mode waves while propagating up to ∼700 km altitude at middle latitude, Foust et al [2010] used a full wave model [ Bell and Ngo , 1990; Lehtinen and Inan , 2008] and modeled whistler wave propagation assuming uniform background density corresponding to that at 700 km and a set of plausible field‐aligned density irregularities. They found that for short propagation paths of ∼15 km, the model predicts power losses ranging from 3 dB (25% probability) to 7 dB (2% probability).…”

Section: Introductionmentioning

confidence: 99%

“…For longer propagation paths of ∼150 km, the model predicts power losses ranging from 4 dB (25% probability) to over 10 dB (2% probability). The model of Foust et al [2010] neglects processes occurring below the F peak and especially at altitudes between 100 and 200 km.…”

Section: Introductionmentioning

confidence: 99%

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Attenuation of whistler waves through conversion to lower hybrid waves in the low‐altitude ionosphere

et al. 2012

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[1] VLF waves excited by powerful ground-based transmitters propagate in the Earth-ionosphere waveguide and leak through the ionosphere to the magnetosphere, where they are often recorded by satellites. Simulations of the propagation of whistler waves using coupled transionospheric VLF propagation and three-dimensional ray-tracing models have shown systematic overestimates of the VLF wavefield strength near 20 kHz in the magnetosphere by about 20 dB in the night and 10 dB during the day. The paper presents numerical simulations of the conversion between whistler and lower hybrid waves interactions in the presence of short-scale field-aligned density irregularities (striations) in Earth's lower ionosphere. The simulations, which incorporate a realistic ionospheric density profile, show that the mode conversion of whistler waves to lower hybrid waves leads to significant attenuation of whistler waves at altitudes between 90 and 150 km. The striation width plays an important role in the conversion efficiency between whistler and lower hybrid wave. Uniformly distributed striations with 8 m transverse size result in 15 dB attenuation in the 90-150 km propagation range, while a spectrum from 2 to 10 m results in 9 dB attenuation. It is argued that the attenuation of whistler waves in the presence of short-scale density striations in Earth's ionosphere can account for most of the observed $20 dB loss in VLF intensity. Furthermore, it predicts that VLF/ELF waves with frequencies below 5 kHz will not suffer similar attenuation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Attenuation of whistler waves through conversion to lower hybrid waves in the low‐altitude ionosphere

et al. 2012

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The effect of electron and ion temperature on the refractive index surface of 1–10 kHz whistler mode waves in the inner magnetosphere

et al. 2015

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Whistler mode waves in the magnetosphere play an important role in the energy dynamics of the Earth's radiation belts. Previous theoretical work has been extended to include ions in the fully adiabatic warm plasma theory. Using a finite electron and ion temperature of 1 eV, refractive index surfaces are calculated for 1–10 kHz whistler mode waves in the inner magnetosphere (L ≲ 2.5). For the frequencies of interest, a finite ion temperature is found to have a greater effect on the refractive index surface than the electron temperature and the primary effect is to close an otherwise open refractive index surface. Including a finite ion temperature is especially important when the wave frequency is just above the local lower hybrid resonance frequency. For wave frequencies more than ∼1 kHz above the local lower hybrid resonance frequency, including the ion temperature has a negligible effect on the refractive index surface calculation. The results are used to assess previous conclusions on whether in situ whistler mode sources can be realistically used to precipitate energetic electrons. It is found that the number of in situ sources needed to illuminate the inner plasmasphere (L≲2.5) with whistler mode energy may be greater than previously predicted.

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Line radiation events induced by very low frequency transmitters observed by the DEMETER spacecraft

et al. 2017

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Electromagnetic wave data measured by the low‐altitude Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft sometimes exhibit intense emissions at discrete, harmonically spaced frequencies. We present a comprehensive analysis of this type of phenomenon, and we demonstrate that it is caused by very low frequency (VLF) transmitters in Europe. All available data were investigated for a possible presence of the events. Altogether, 87 events were identified, occurring exclusively during the nighttime. The occurrence of the events does not show any clear relation to the AE and Dst geomagnetic activity indices. The events are clearly localized, occurring either close to Great Britain or in the vicinity of its geomagnetically conjugated region. The frequency spectra of the events typically consist of up to four spectral peaks at multiples of about 1.3 kHz. Additional weaker spectral peaks at frequencies of about 1.9 kHz and 3.2 kHz are occasionally present. The events observed in the Northern Hemisphere tend to have larger‐frequency bandwidths than the events observed in the Southern Hemisphere. The occurrence of these events is correlated with the simultaneous detection of signals from VLF transmitters. A bicoherence analysis is employed to demonstrate that wave‐wave coupling takes place. Finally, it is shown that the occurrence of the events is associated with a significantly increased precipitation of energetic electrons in a wide range of energies.

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Quasi‐electrostatic whistler mode wave excitation by linear scattering of EM whistler mode waves from magnetic field‐aligned density irregularities

Cited by 11 publications

References 25 publications

Attenuation of whistler waves through conversion to lower hybrid waves in the low‐altitude ionosphere

Attenuation of whistler waves through conversion to lower hybrid waves in the low‐altitude ionosphere

The effect of electron and ion temperature on the refractive index surface of 1–10 kHz whistler mode waves in the inner magnetosphere

Line radiation events induced by very low frequency transmitters observed by the DEMETER spacecraft

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