VLF observation of long ionospheric recovery events

Cotts, B. R. T.; Inan, U. S.

doi:10.1029/2007gl030094

Cited by 33 publications

(63 citation statements)

References 19 publications

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“…These early VLF events are also sometimes associated with Transient luminous events (TLEs) such as red sprites and elves (Inan et al, 1995;Dowden et al, 1996;Hobara et al, 2001). A new class of early VLF event associated with lighting with long recovery time up to 20 min has been reported (Cotts and Inan, 2007). Even this long recovery event may not have a recovery time long enough to affect three nighttime averaged statistical parameters.…”

Section: Discussionmentioning

confidence: 99%

Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

et al. 2015

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Abstract. We investigate quantitatively the effect of geomagnetic storms on the sub-ionospheric VLF/LF (Very Low Frequency/Low Frequency) propagations for different latitudes based on 2-year nighttime data from Japanese VLF/LF observation network. Three statistical parameters such as average signal amplitude, variability of the signal amplitude, and nighttime fluctuation were calculated daily for 2 years for 16-21 independent VLF/LF transmitter-receiver propagation paths consisting of three transmitters and seven receiving stations. These propagation paths are suitable to simultaneously study high-latitude, low-mid-latitude and midlatitude D/E-region ionospheric properties. We found that these three statistical parameters indicate significant anomalies exceeding at least 2 times of their standard deviation from the mean value during the geomagnetic storm time period in the high-latitude paths with an occurrence rate of anomaly between 40 and 50 % presumably due to the auroral energetic electron precipitation. The mid-latitude and lowmid-latitude paths have a smaller influence from the geomagnetic activity because of a lower occurrence rate of anomalies even during the geomagnetically active time period (from 20 to 30 %). The anomalies except geomagnetic storm periods may be caused by atmospheric and/or lithospheric origins. The statistical occurrence rates of ionospheric anomalies for different latitudinal paths during geomagnetic storm and non-storm time periods are basic and important information not only to identify the space weather effects toward the lower ionosphere depending on the latitudes but also to separate various external physical causes of lower ionospheric disturbances.

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Section: Discussionmentioning

confidence: 99%

Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

et al. 2015

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“…With regard to a recovery time of about 12 min the event is "slow", implicating persistent ionization. Cotts and Inan (2007) distinguish 3 types of long recovery events: long-amplitude/short-phase recovery (Type 1), longamplitude/long-phase recovery (Type 2), and step-change events (Type 3) in which the amplitude does not return to pre-event levels. With a recovery time of 12 min in amplitude and phase, an amplitude dip of −5 dB and a phase change of 35 • our reported event is of type 2 with regard to the GBZ signal, Figs.…”

Section: Introductionmentioning

confidence: 99%

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

Schmitter¹

2014

Adv. Radio Sci.

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Abstract. On the 4 November 2012 at 3:04:27 UT a strong lightning in the midst of the North Sea affected the propagation conditions of VLF/LF transmitter radio signals from NRK (Iceland, 37.5 kHz) and GBZ (UK, 19.58 kHz) received at 5246 • N 8 • E (NW Germany). The amplitude and phase dips show a recovery time of 6-12 min pointing to a LOng Recovery Early VLF (LORE) event. Clear assignment of the causative return stroke in space and time was possible with data from the WWLLN (Worldwide Lightning Location Network). Based on a return stroke current model the electric field is calculated and an excess electron density distribution which decays over time in the lower ionosphere is derived. Ionization, attachment and recombination processes are modeled in detail. Entering the electron density distribution in VLF/LF radio wave propagation calculations using the LWPC (Long Wavelength Propagation Capability) code allows to model the VLF/LF amplitude and phase behavior by adjusting the return stroke current moment. The results endorse and quantify the conception of lower ionosphere EMP heating by strong -but not necessarily extremely strong -return strokes of both polarities.

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“…The following scientific results were obtained and reported in the indicated papers: Cotts and Inan [2007a] documented the first observation of exceptionally short (>1 second, rapid initial) and very long (~20 minutes, long enduring) recovery components in some Early VLF events. The research showed that long recovery VLF events are 2.5 to 5 times more likely to be observed on oceanic paths, consistent with the oceanic storms where gigantic blue jets have predominantly been observed.…”

Section: Resultsmentioning

confidence: 99%

Optical and VLF Imaging of Lightning-Ionosphere Interactions

Inan¹

2007

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electrodynamic coupling between the troposphere, mesosphere, lower ionosphere, and magnetosphere. Lightning-induced electron precipitation encompasses all of these regions, from atmospheric and mesospheric electrodynamics, to radiation belt scattering, to precipitation and disturbances of ionospheric communication channels. Furthermore, observation of direct lightningionospheric coupling mechanisms can lead to the understanding of ion chemical dynamics in the upper-mesosphere, and lower-ionosphere, including determination of ambient electron density profiles and unknown chemical interaction parameters. Sprites and their possible conjugate effects due to relativistic electrons also constitute a coupling between the regions, including lightning effects on the mesosphere and ionosphere. Geomagnetic disturbances highlight the coupling between these regions, with the resulting perturbations in the magnetosphere and ionosphere easily detectable. OBJECTIVESObjectives of the current three-year effort are to address the following scientific questions: What role do lightning generated whistlers play in the formation of the slot region of the radiation belts? How can VLF remote sensing be used to quantitatively measure the energy spectra and flux of precipitating electrons associated with LEP events? What is the contribution of MR whistlers and lightningtriggered-plasmaspheric hiss to the loss of electron radiation? How do sprites evolve on a fine spatial and temporal scale, and how does this evolution compare to conventional and streamer breakdown theory? What is the cause of the fine-scale bead-like features of sprites? How does the thundercloud activity relate to the spatial and temporal evolution of sprites? How are sprites and sprite halos related to conductivity perturbations on the ionosphere, observed as early/fast perturbations to VLF transmitter signals? What is the effect of in-cloud lightning on the lower ionosphere? How can VLF remote sensing be used to quantify atmospheric ion-chemistry interaction parameters? Are long-recovering Early VLF events the result of a different causative mechanism than their short-recovery counterparts, and are long recovery events more likely to be observed on all ocean-based paths than paths over land?If so, what is the physical source of this preference? APPROACHOur approach consists of the use of optical and wideband VLF/LF measurements to document high altitude optical phenomena and VLF/LF holographic imaging of ionospheric disturbances together with the causative lightning flashes. The VLF/LF antennas are deployed at seven high schools and 1

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VLF observation of long ionospheric recovery events

Cited by 33 publications

References 19 publications

Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

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

Optical and VLF Imaging of Lightning-Ionosphere Interactions

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