VLF scattering from red sprites: Application of numerical modeling

Rodger, Craig J.; Nunn, D.

doi:10.1029/1999rs900040

Cited by 19 publications

(16 citation statements)

References 28 publications

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“…There is now strong evidence that red sprites are closely associated with plasma columns with large electron densities in comparison with the ambient night-time ionosphere. The first evidence for this came from observations of VLF Sprites [Dowden et al, 1996a, b] and subsequent modeling suggesting that the difference in electron densities could be nearly five orders of magnitude larger than ambient at -70 km altitude [Rodger and Nunn, 1999]. This finding is supported by recent spectral measurements of red sprites reported at the 1998 AGU Fall meeting [e.g., Heavner et al, 1998].…”

Section: Introductionsupporting

confidence: 73%

Modeling the relaxation of red sprite plasma

Nunn¹,

Rodger²

1999

Geophysical Research Letters

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Abstract. Red sprites consist of multiple ionised columns extending above a thunderstorm from -30 km to -90 km.Electron densities in these columns are very much larger than the ambient background, perhaps fives orders of magnitude at 70 km. These highly ionized structures cause observable perturbations in subionospheric VLF transmissions known as "VLF Sprites". Three models of initial sprite electron density are considered, and using a realistic ionization relaxation model the time dependence of electron density is derived. A 3-D Born propagation code of is used to compute the time profile of a VLF sprite. Two profiles show good agreement with the time signature experimentally observed, in that scattered amplitude and phase decrease logarithmically with time. These simulations provide insight into the nature and structure of sprite columns, and indicate an additional constraint which should be applied to red sprite creation models.

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Section: Introductionsupporting

confidence: 73%

Modeling the relaxation of red sprite plasma

Nunn¹,

Rodger²

1999

Geophysical Research Letters

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“…The received amplitude and its polarity are strongly dependent on a number of parameters; in particular, the path length, the position of the disturbance relative to the receiver, ionospheric ground parameters, and the transmitter frequency . Based on the results from the VLF scattering from red sprites, Rodger and Nunn (1999) have shown that the internal electrical structure in a sprite could lead to four combinations of amplitude and phase perturbations (Aθ = ++, −−, −+, +−) of early VLF events, where + in amplitude means an increase, − in amplitude means a decrease, + in phase means advance and − in phase means retard. The large negative perturbations (≥1.5 dB, Fig.…”

Section: Resultsmentioning

confidence: 99%

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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“…One possible reason for this is that the expected maximum D region electron density change calculated for a reasonable representation of a typical relativistic electron microburst of 100 el. cm Rodger et al, 2007, Figure 5] is an increase of ∼20-40 times, while red sprites produce 4-6 order of magnitude electron density increases [e.g., Rodger and Nunn, 1999;Nunn and Rodger, 1999;Armstrong et al, 2000], in comparison with the ambient nighttime ionosphere. This suggests that a typical relativistic electron microburst is likely to be too small to lead to significant wide-angle VLF scattering.…”

Section: Discussionmentioning

confidence: 99%

Relativistic microburst storm characteristics: Combined satellite and ground-based observations

Dietrich

Rodger

Clilverd

et al. 2011

2011 XXXth URSI General Assembly and Scientific Symposium

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[1] We report a comparison of Solar Anomalous Magnetospheric Particle Explorer detected relativistic electron microbursts and short-lived subionospheric VLF perturbations termed FAST events, observed at Sodankylä Geophysical Observatory, Finland, during 2005. We show that only strong geomagnetic disturbances can produce FAST events, which is consistent with the strong link between storms and relativistic microbursts. Further, the observed FAST event perturbation decay times were consistent with ionospheric recovery from bursts of relativistic electron precipitation. However, the one-to-one correlation in time between microbursts and FAST events was found to be very low (∼1%). We interpret this as confirmation that microbursts have small ionospheric footprints and estimate the individual precipitation events to be <4 km radius. In contrast, our study strongly suggests that the region over which microbursts occur during storm event periods can be at least ∼90°in longitude (∼6 h in magnetic local time). This confirms earlier estimates of microburst storm size, suggesting that microbursts could be a significant loss mechanism for radiation belt relativistic electrons during geomagnetic storms. Although microbursts are observed at a much higher rate than FAST events, the ground-based FAST event data can provide additional insight into the conditions required for microburst generation and the time variation of relativistic precipitation.

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VLF scattering from red sprites: Application of numerical modeling

Cited by 19 publications

References 28 publications

Modeling the relaxation of red sprite plasma

Modeling the relaxation of red sprite plasma

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

Relativistic microburst storm characteristics: Combined satellite and ground-based observations

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