Subionospheric VLF signatures of oblique (nonducted) whistler‐induced precipitation

Johnson, Mike; Inan, U. S.; Lauben, D.

doi:10.1029/1999gl010706

Cited by 46 publications

(80 citation statements)

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“…Such leakage would give a significantly larger precipitation footprint than the actual dimensions of the whistler duct. A different mechanism also leading to large WEP patch dimensions comes through the precipitation caused by obliquely (nonducted) propagating whistlers, creating an ionospheric disturbance of ∼1000 km spatial extent (Johnson et al, 1999). At this stage there is no clear experimental evidence to indicate whether quasi-ducted or nonducted whistler propagation dominates the overall WEP losses .…”

Section: Introductionmentioning

confidence: 96%

Investigating radiation belt losses though numerical modelling of precipitating fluxes

2004

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Abstract. It has been suggested that whistler-induced electron precipitation (WEP) may be the most significant inner radiation belt loss process for some electron energy ranges. One area of uncertainty lies in identifying a typical estimate of the precipitating fluxes from the examples given in the literature to date. Here we aim to solve this difficulty through modelling satellite and ground-based observations of onset and decay of the precipitation and its effects in the ionosphere by examining WEP-produced Trimpi perturbations in subionospheric VLF transmissions. In this study we find that typical Trimpi are well described by the effects of WEP spectra derived from the AE-5 inner radiation belt model for typical precipitating energy fluxes. This confirms the validity of the radiation belt lifetimes determined in previous studies using these flux parameters. We find that the large variation in observed Trimpi perturbation size occurring over time scales of minutes to hours is primarily due to differing precipitation flux levels rather than changing WEP spectra. Finally, we show that high-time resolution measurements during the onset of Trimpi perturbations should provide a useful signature for discriminating WEP Trimpi from non-WEP Trimpi, due to the pulsed nature of the WEP arrival.

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Section: Introductionmentioning

confidence: 96%

Investigating radiation belt losses though numerical modelling of precipitating fluxes

2004

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“…Such whistlers are called magnetospherically reflected (MR) whistlers (Smith and Angerami, 1968). Whistlers play an important role in radiation belt physics because both ducted (Burgess and Inan, 1993) and nonducted (Johnson et al, 1999) whistlers are known to precipitate energetic electrons via resonant wave-particle interactions. Various modeling studies indicate that whistlers may be important in determining the lifetimes of radiation belt electrons in the inner belt and slot regions (Abel and Thorne, 1998).…”

Section: Whistlersmentioning

confidence: 99%

First results from the Cluster wideband plasma wave investigation

et al. 2001

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Abstract. In this report we present the first results from the Cluster wideband plasma wave investigation. The four Cluster spacecraft were successfully placed in closely spaced, high-inclination eccentric orbits around the Earth during two separate launches in July -August 2000. Each spacecraft includes a wideband plasma wave instrument designed to provide high-resolution electric and magnetic field waveforms via both stored data and direct downlinks to the NASA Deep Space Network. Results are presented for three commonly occurring magnetospheric plasma wave phenomena: (1) whistlers, (2) chorus, and (3) auroral kilometric radiation. Lightning-generated whistlers are frequently observed when the spacecraft is inside the plasmasphere. Usually the same whistler can be detected by all spacecraft, indicating that the whistler wave packet extends over a spatial dimension at least as large as the separation distances transverse to the magnetic field, which during these observations were a few hundred km. This is what would be expected for nonducted whistler propagation. No case has been found in which a strong whistler was detected at one spacecraft, with no signal at the other spacecraft, which would indicate ducted propagation. Whistler-mode chorus emissions are also observed in the inner region of the magnetosphere. In contrast to lightninggenerated whistlers, the individual chorus elements seldom show a one-to-one correspondence between the spacecraft, indicating that a typical chorus wave packet has dimensions transverse to the magnetic field of only a few hundred km or less. In one case where a good one-to-one correspondence existed, significant frequency variations were observed between the spacecraft, indicating that the frequency of the wave packet may be evolving as the wave propagates. Auroral kilometric radiation, which is an intense radio emission generated along the auroral field lines, is frequently observed over the polar regions. The frequency-time structure of this radiation usually shows a very good one-to-one correspondence between the various spacecraft. By using the Correspondence to: D. A. Gurnett (donald-gurnett@uiowa.edu) microsecond timing available at the NASA Deep Space Network, very-long-baseline radio astronomy techniques have been used to determine the source of the auroral kilometric radiation. One event analyzed using this technique shows a very good correspondence between the inferred source location, which is assumed to be at the electron cyclotron frequency, and a bright spot in the aurora along the magnetic field line through the source.

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“…As such, these unducted whistlers may undergo numerous, repeated reflections that may lead to the formation of a uniform band of wave energy [Sonwalkar and Inan, 1989]. It has been demonstrated theoretically that whistler mode waves interact with high-energy radiation belt electron plasmas leading to a scattering of these electrons into the loss cone and their subsequent precipitation Johnson et al, 1999;Rodger et al, 2004]. Consequently, magnetospherically reflected lightning-generated whistlers may play a significant role in regulating the population of radiation belt electrons.…”

Section: Propagationmentioning

confidence: 99%

Whistlers observed outside the plasmasphere: Correlation to plasmaspheric/plasmapause features

et al. 2015

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Whistlers observed outside the plasmasphere by Cluster have been correlated with the global plasmasphere using Imager for Magnetopause-to-Aurora Global Exploration-Extreme Ultraviolet Imager (IMAGE-EUV) observations. Of the 12 Cluster-observed whistler events reported, EUV is able to provide global imaging of the plasmasphere for every event and demonstrates a direct correlation between the detection of lightning-generated whistlers beyond the plasmapause and the presence of a global perturbation of the local plasmapause. Of these 12 correlated events, seven of the Cluster-observed whistlers (or 58%) are associated with the Cluster spacecraft lying radially outward from a plasmaspheric notch. Two of the Cluster-observed whistlers (17%) are associated with the low-density region between the late afternoon plasmapause and the western wall of a plasmaspheric drainage plume. The final three Cluster-observed whistler events (25%) are associated with a nonradial, nonazimuthal depletion in plasmaspheric He + emission that are termed "notch-like" crenulations. In one of these cases, the notch-like crenulations appear to be manifestations entrained within the plasmasphere boundary layer of a standing wave on the surface of the plasmasphere. The correlated Cluster/IMAGE-EUV observations suggest that the depleted flux tubes that connect the ionosphere to the low-density regions of plasmaspheric trough and inner magnetosphere facilitate the escape of whistler waves from the plasmasphere.

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Subionospheric VLF signatures of oblique (nonducted) whistler‐induced precipitation

Cited by 46 publications

References 10 publications

Investigating radiation belt losses though numerical modelling of precipitating fluxes

Investigating radiation belt losses though numerical modelling of precipitating fluxes

First results from the Cluster wideband plasma wave investigation

Whistlers observed outside the plasmasphere: Correlation to plasmaspheric/plasmapause features

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