Ionospheric <i>D</i> region electron density profiles derived from the measured interference pattern of VLF waveguide modes

Bainbridge, G. R.; Inan, U. S.

doi:10.1029/2002rs002686

Cited by 28 publications

(19 citation statements)

References 25 publications

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“…Many VLF band measurements were made for D region perturbations, not ambient profile changes. Bainbridge and Inan [2003] studied the direct energy coupling between lightning and lower ionosphere using single frequency VLF data recorded at Huntsville (HU), Alabama and Arecibo (AR), and Puerto Rico stations. Peter and Inan [2004] studied the occurrence and spatial extent of D region perturbations caused by LEP using VLF data generated by large man‐made transmitters and recorded by the Holographic Array for Ionospheric/Lightning Research (HAIL).…”

Section: Introductionmentioning

confidence: 99%

Midlatitude nighttime D region ionosphere variability on hourly to monthly time scales

2010

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[1] Significant temporal variability of the nighttime D region is well known, but its inaccessibility means that the time scales, magnitudes, and sources for that variability are not well understood. We probed the ionospheric D region by measuring the high-power broadband very low frequency (VLF) signals launched by lightning and propagating in the Earth-ionosphere waveguide. We analyzed broadband sferic data of July and August 2005 recorded by our sensors located near Duke University by comparing measured sferic spectra to model results and extracted the height of an assumed exponential electron density profile for each measurement. The measured nighttime D region electron density profile heights showed large temporal variations of several kilometers on some nights and relatively stable behaviors on others. The measured hourly average heights in 260 h ranged between 82.0 and 87.2 km, with a mean value of 84.9 km and a standard deviation of 1.1 km. The maximum variation in the 5 h period was around just above 4.0 km and the maximum variation in the 1 h period was around 1.3 km, with sharper gradients observed over shorter time periods. We also observed spatial variability as large as 2.0 km over 5°latitudes on some nights and no spatial variability on others. On some nights, the temporal variability exhibited a close correlation with the occurrence rate of lightning discharges under the probed region. This suggests that the direct energy coupling between lightning discharges and lower ionosphere can be a significant source of the D region variability. However, on other nights, the measured height temporal variability showed weak to no correlation with local lightning, displaced lightning (as would be expected for lightning-induced electron precipitation), or geomagnetic activities. These measurements suggest that nighttime D region variability may be driven by many sources.Citation: Han, F., and S. A. Cummer (2010), Midlatitude nighttime D region ionosphere variability on hourly to monthly time scales,

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Section: Introductionmentioning

confidence: 99%

Midlatitude nighttime D region ionosphere variability on hourly to monthly time scales

2010

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“…Further discussion on the use of subionospheric VLF propagation as a remote sensing probe can be found in recent review articles (e.g. Barr et al, 2000; and studies (Cummer and Inan, 2000;McRae and Thomson, 2000;Bainbridge and Inan, 2003). WEP leads to localized ionospheric modifications produced by secondary ionisation just below the D-region of the ionosphere, which are observed as "Trimpi" perturbations in subionospheric VLF transmissions (Helliwell et al, 1973).…”

Section: Introductionmentioning

confidence: 99%

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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“…The Nançay receiver was recording the VLF background noise in the 350 Hz-50 kHz range with 100 kHz sampling frequency. It was possible to post-process this broadband signal and extract from it narrowband VLF transmitter signal time series (Bainbridge and Inan 2003).…”

Section: Instrumentationmentioning

confidence: 99%

VLF Studies During TLE Occurrences in Europe: A Summary of New Findings

Mika¹,

Haldoupis

2008

Space Sci Rev

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The paper reviews the past few years' European efforts for characterising the effects of TLEs, in particular sprites and elves, on the lower ionosphere. A mostly experimental approach was applied for the analysis of data collected during the EuroSprite campaigns by optical cameras, very low frequency (VLF, 3-30 kHz) receivers and lightning detection systems. The new findings of these multi-instrumental studies can be summarised as follows: 1) A close relationship between sprites and early VLF perturbations was established which constitutes evidence of upper D-region electron density changes in association with sprites. 2) VLF backscatter from the sprite-affected regions exists but it occurs rarely.3) Long-delayed sprites were present in a large percentage, contrary to previous reports; they occurred in relation to long-lasting continuing currents that contribute to the buildup of sprite-causative quasi-electrostatic fields. 4) Intracloud lightning was found to be the key-factor which determines the sprite morphological features. 5) A new subcategory of VLF events was discovered, termed early/slow, characterised by long onset durations from 100 ms up to ∼2 s. The slow onsets, which were attributed to a gradual ionisation build-up, are driven by a dense sequence of intracloud electromagnetic pulses that accompany the sprite-causative discharge. 6) A D-region chemical model was applied to simulate the measured recovery phases of the early VLF perturbations. This led to estimates about the mean altitude and electron density enhancements of the sprite-related ionospheric perturbations. 7) Early VLF events were identified for the first time to occur in association with elves, providing evidence that corroborates theoretical predictions on lower-ionospheric ionisation production by lightning-emitted electromagnetic pulses.

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Ionospheric D region electron density profiles derived from the measured interference pattern of VLF waveguide modes

Cited by 28 publications

References 25 publications

Midlatitude nighttime D region ionosphere variability on hourly to monthly time scales

Midlatitude nighttime D region ionosphere variability on hourly to monthly time scales

Investigating radiation belt losses though numerical modelling of precipitating fluxes

VLF Studies During TLE Occurrences in Europe: A Summary of New Findings

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