VLF observations of ionospheric disturbances in association with TLEs from the EuroSprite‐2007 campaign

Naitamor, S.; Alabdoadaim, Mohamed; Cohen, M. B.; Cotts, B. R. T.; Soula, Serge; Chanrion, Olivier; Neubert, Torsten; Abdelatif, Toufik E.

doi:10.1029/2009ja015026

Cited by 25 publications

(42 citation statements)

References 26 publications

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“…From early/fast events and sprite observations in the USA, Marshall et al (2006) reported that only a very small subset (9 out 250) of sprites shows characteristics of the VLF wide-angle scattering from the sprite body, and that all such cases correspond to multiple sprites or horizontally expansive sprites. Early/fast events associated with wide-angle scatterings have been reported under the EuroSprite-2007(NaitAmor et al, 2007. The narrowangle scattering of VLF signals has also been reported to be associated from smoother and larger regions of the enhanced electron density and wideangle scattering associated with columns of enhanced ionization due to strong sprites .…”

Section: Resultsmentioning

confidence: 92%

Lightning-associated VLF perturbations observed at low latitude: Occurrence and scattering characteristics

Kumar

2013

Earth Planet Sp

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The occurrence of short-timescale (∼1-100 s) perturbations (early VLF events) on four Very Low Frequency (VLF) transmitter signals (call signs: NWC, NPM, VTX, NLK), recorded at Suva (18.1• S, 178.5• E, L = 1.16), shows the most frequent occurrence on the NWC signal and least on the VTX. Daytime early/fast events on the NWC transmission are (0.2-0.5 dB) with only negative amplitude perturbations with comparatively lower recovery times (10-30 s) as compared with most nighttime events with amplitude perturbations of 0.2-1.5 dB and recovery times of 20-80 s. The World-Wide Lightning Location Network detected causative lightnings for 74 of 453 early VLF events out of which 54 (73%) were produced due to narrow-angle scattering, and by 20 (27%) due to wide-angle scattering. The recovery (decay) of the scattered amplitude of early/fast events on the NWC signal shows both exponential and logarithmic forms, but the linear correlation coef cient is better with a logarithm t. The rst observations of early/slow events in daylight propagation are presented. Initial results on early/fast events with unusually long recoveries (≥5 min) and strong perturbations (≥1 dB) indicate that they are mainly observed on the transmissions from NPM and NLK in the nighttime only, with rare occurrence on other transmissions. Such unusually long recovery of early/fast events may be associated with large ionic conductivity perturbations associated with gigantic jets.

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Section: Resultsmentioning

confidence: 92%

Lightning-associated VLF perturbations observed at low latitude: Occurrence and scattering characteristics

Kumar

2013

Earth Planet Sp

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“…This, combined with the fact that an event may not be detectable by all links that have similar GCPs, means that there are more reasons involved in LORE generation and/or VLF detection, such as the path geometry, as discussed by Nait Amor et al . []. This observation indicates that the requirement for a large peak current intensity and a short distance of discharge location to GCP is a strong contributing factor in the observation of LORE events, but this by itself is not a sufficient criterion for LORE detection.…”

Section: Resultsmentioning

confidence: 99%

“…The amplitude steps are ~1.0 dB, but in general, they can range from a fraction of decibels to several decibels. The perturbation amplitudes were not analyzed here, as they are affected in a complex way by many factors [ Marshall et al ., ] including the causative peak current intensity and the distance of discharge location relative to a VLF link GCP [ NaitAmor et al ., ], the VLF transmitter signal characteristics (e.g., power and frequency), complex waveguide modal propagation and scattering geometry effects [ Poulsen et al ., ], and ambient ionospheric conditions, whose effects on the signal amplitude are not easily quantified.…”

Section: Resultsmentioning

confidence: 99%

The VLF fingerprint of elves: Step‐like and long‐recovery early VLF perturbations caused by powerful ±CG lightning EM pulses

et al. 2013

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[1] Subionospheric VLF recordings are investigated in relation with intense cloud-to-ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long-recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short-lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long-lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ± CG lightning peak currents of typically > 250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within~250 km from the great circle path of a VLF transmitter-receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents ≥~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ± CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long-going VLF research of lightning effects in the lower ionosphere.Citation: Haldoupis, C., M. Cohen, E. Arnone, B. Cotts, and S. Dietrich (2013), The VLF fingerprint of elves:Step-like and long-recovery early VLF perturbations caused by powerful ±CG lightning EM pulses,

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“…On the other hand, Kotovsky and Moore [] point out that a large number of sprite halos are triggered by negative cloud‐to‐ground strokes and suggest a different mechanism. As if the lightning properties are not sufficiently complicated, NaitAmor et al [, ] suggest that the distance between the disturbed region to both the transmitter and the receiver, as well as the scattering angle, may be a more important factor than the parameters of the lightning, for both ordinary early and LORE events. These two studies included observations from multiple transmitters and receivers for the same event, which appeared very differently in VLF data.…”

Section: Introductionmentioning

confidence: 99%

TLEs and early VLF events: Simulating the important impact of transmitter‐disturbance‐receiver geometry

2017

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Early very low frequency (VLF) events are perturbations to subionospherically propagating VLF radio transmitters which sometimes occur when lightning activity is near the transmitter‐receiver path. They are often correlated to Transient Luminous Events (TLEs). Recent analysis have focused on a new type of early events whose recovery time persists for many minutes, called LOng Recovery Events (LOREs). The underlying cause of these events is still unclear. Curiously, LOREs sometimes appear on only one path, while the same event observed on a different transmitter‐receiver path does not indicate a LORE. In this paper we observe and simulate two cases of early signal perturbations: The first is a typical early VLF event, and the second is a LORE. Both were recorded by two AWESOME VLF receivers in North Africa on 12 December 2009, during the EuroSprite campaign. We combine observations with theoretical modeling to infer the electron density change that most closely reproduces the observed perturbation. Our results explain the cases where LOREs are detected on only one path as resulting from transmitter‐receiver geometry significantly which impacts the modal content and therefore the observed VLF recovery time.

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VLF observations of ionospheric disturbances in association with TLEs from the EuroSprite‐2007 campaign

Cited by 25 publications

References 26 publications

Lightning-associated VLF perturbations observed at low latitude: Occurrence and scattering characteristics

Lightning-associated VLF perturbations observed at low latitude: Occurrence and scattering characteristics

The VLF fingerprint of elves: Step‐like and long‐recovery early VLF perturbations caused by powerful ±CG lightning EM pulses

TLEs and early VLF events: Simulating the important impact of transmitter‐disturbance‐receiver geometry

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