Remote sensing and modeling of lightning caused long recovery events within the lower  ionosphere using VLF/LF radio wave propagation

Schmitter, Ernst D.

doi:10.5194/ars-12-241-2014

Cited by 10 publications

(11 citation statements)

References 26 publications

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“…The main evidence is the tendency for the LOREs to occur with higher lightning peak current of both positive and negative polarities, which are also known to trigger elves [Haldoupis et al, 2013], whereas sprites are largely associated with positive strokes. Schmitter [2014] reached a similar conclusion theoretically. On the other hand, Kotovsky and Moore [2016] point out that a large number of sprite halos are triggered by negative cloud-to-ground strokes and suggest a different mechanism.…”

Section: Introductionsupporting

confidence: 63%

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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Section: Introductionsupporting

confidence: 63%

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

2017

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“…Its conductivity is primarily determined by (1) the electron density, (2) the electron mobility (inversely related to the electron‐neutral collision rate), and (3) the Earth's magnetic field. In our simplified model, we assumed that all the effects that materially influence ionospheric reflections can be captured in the exponential conductivity profile expressed as follows (Schmitter, ; Wait & Spies, ):

σ ((), h) = σ_{0} exp ([], β ((), h - h^{'}))

where h is the altitude above ground, h ′ and β are the reference height and the steepness of the electron density profile, and σ 0 = 2.22 μS/m is the conductivity at h = h ′. Note that sometimes h ′ is referred to as the virtual reflection height of the ionosphere for VLF waves.…”

Section: Methodsmentioning

confidence: 88%

“…They found that the apparent ionospheric reflection height, estimated from measured sky wave delays relative to the ground wave, tends to decrease with stroke order within the same flash, at least under daytime conditions. This result (interpreted by the authors as being, at least in part, due to additional ionization associated with elves) is inconsistent with predictions of existing models (e.g., Marshall, ), except for that of Schmitter ().…”

Section: Introductionmentioning

confidence: 99%

“…More recently, a 3-D spherical FDTD model, including nonlinear effects, was developed by Marshall (2012). Schmitter (2014) used the Hertzian-dipole return-stroke model and LWPC to find the electron density profile disturbed by lightning. The return-stroke current waveform was represented by Heidler's function (Heidler, 1985) with a peak of 50 kA and a peak rate-of-rise (dI/dt) of 25 kA/μs.…”

Section: Introductionmentioning

confidence: 99%

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FDTD Modeling of LEMP Propagation in the Earth‐Ionosphere Waveguide With Emphasis on Realistic Representation of Lightning Source

et al. 2017

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The finite difference time domain (FDTD) method in the 2‐D cylindrical coordinate system was used to compute the nearly full‐frequency‐bandwidth vertical electric field and azimuthal magnetic field waveforms produced on the ground surface by lightning return strokes. The lightning source was represented by the modified transmission‐line model with linear current decay with height, which was implemented in the FDTD computations as an appropriate vertical phased‐current‐source array. The conductivity of atmosphere was assumed to increase exponentially with height, with different conductivity profiles being used for daytime and nighttime conditions. The fields were computed at distances ranging from 50 to 500 km. Sky waves (reflections from the ionosphere) were identified in computed waveforms and used for estimation of apparent ionospheric reflection heights. It was found that our model reproduces reasonably well the daytime electric field waveforms measured at different distances and simulated (using a more sophisticated propagation model) by Qin et al. (2017). Sensitivity of model predictions to changes in the parameters of atmospheric conductivity profile, as well as influences of the lightning source characteristics (current waveshape parameters, return‐stroke speed, and channel length) and ground conductivity were examined.

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“…Remote VLF/LF sensing therefore since decades proves as an inexpensive and reliable way to assess forcing processes in this layer, also with regard to auroral pre- cipitation activity (Cummer et al, 1996(Cummer et al, , 1998. During the last years we have developed a modeling scheme that allows to assess ionospheric forcing parameters from VLF/LF amplitude and phase recordings of distant Minimum Shift Keying (MSK) transmitters (Schmitter, 2010(Schmitter, , 2011(Schmitter, , 2012(Schmitter, , 2013(Schmitter, , 2014. As the amplitude of these transmissions is constant, any observed variations are caused along the propagation path.…”

Section: Introductionmentioning

confidence: 99%

Remote sensing and modeling of energetic electron precipitation into the lower ionosphere using VLF/LF radio waves and field aligned current data

Schmitter

2015

Adv. Radio Sci.

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Abstract.A model for the development of electron density height profiles based on space time distributed ionization sources and reaction rates in the lower ionosphere is described. Special attention is payed to the definition of an auroral oval distribution function for energetic electron energy input into the lower ionosphere based on a Maxwellian energy spectrum. The distribution function is controlled by an activity parameter which is defined proportional to radio signal amplitude disturbances of a VLF/LF transmitter. Adjusting the proportionality constant allows to model precipitation caused VLF/LF signal disturbances using radio wave propagation calculations and to scale the distribution function. Field aligned current (FAC) data from the new Swarm satellite mission are used to constrain the spatial extent of the distribution function. As an example electron precipitation bursts during a moderate substorm on the 12 April 2014 (midnight-dawn) are modeled along the subauroral propagation path from the NFR/TFK transmitter (37.5 kHz, Iceland) to a midlatitude site.

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Remote sensing and modeling of lightning caused long recovery events within the lower ionosphere using VLF/LF radio wave propagation

Cited by 10 publications

References 26 publications

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

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

FDTD Modeling of LEMP Propagation in the Earth‐Ionosphere Waveguide With Emphasis on Realistic Representation of Lightning Source

Remote sensing and modeling of energetic electron precipitation into the lower ionosphere using VLF/LF radio waves and field aligned current data

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