Characteristics of the earth-ionosphere waveguide for VLF radio waves

Wait, James R.

doi:10.6028/nbs.tn.300

Cited by 491 publications

(485 citation statements)

References 11 publications

Supporting

Mentioning

466

Contrasting

Unclassified

Order By: Relevance

“…A similar, though smaller magnitude, ionospheric height variation has been reported by Han and Cummer [2010] based on frequencydomain measurements. The ionospheric heights cannot be compared directly between the two methods because the analysis in this paper determines the effective VLF/LF reflection height and the Han and Cummer method infers the exponential ionospheric profile height as defined in Wait and Spies [1964]. In addition to the general decrease in ionospheric height measured in this paper, ionospheric height splitting was detected in a localized region for a short time period (∼10 min), possibly indicating that two layers of higher electron density are present during that period.…”

Section: Summary and Discussionmentioning

confidence: 99%

High temporal and spatial-resolution detection of D-layer fluctuations by using time-domain lightning waveforms

Lay

Shao

2011

J. Geophys. Res.

View full text Add to dashboard Cite

[1] This paper presents a new method for probing ionospheric D-layer fluctuations with time-domain very-low and low-frequency (VLF/LF) lightning waveforms detected several hundred kilometers away from lightning storms. The technique compares the amplitude and the time delay between the direct ground wave and the first-hop ionospheric reflection of the lightning signal to measure the apparent D-layer reflectivity and height. This time-domain technique allows a higher time and spatial resolution measurement of the D-layer fluctuations compared to previously reported frequency-domain techniques. For a region near a nighttime thunderstorm, results demonstrate that the apparent reflectivity and height exhibit significant variation on spatial scales of tens of kilometers and over time periods of hours. The range of the reflectivity variation was observed as large as 100% away from the averaged reflectivity for some localized regions, and the height varies by as much as 5% (4 km). The time scales and propagation velocities of the fluctuations appear to be consistent with signatures of atmospheric gravity waves at D-layer altitudes, and the direction of the fluctuation propagation suggests that the gravity waves are originated from the storm. Superimposed on the fluctuations, a general decreasing trend (by ∼4-8 km) in reflection height over the nighttime is observed. In some localized ionosphere regions, apparent splitting of the D-layer by 2-4 km is observed to last a short time period of about 10 min.

show abstract

Section: Summary and Discussionmentioning

confidence: 99%

High temporal and spatial-resolution detection of D-layer fluctuations by using time-domain lightning waveforms

Lay

Shao

2011

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…The ambient electron density profile can be expressed as 29 : ARTICLE represent a typical nighttime electron density profile. The positive ion density n ion is assumed to be equal to the electron density at high altitudes where electron density has values larger than 10 8 m À 3 , and at lower altitudes the positive ion density is equal to 10 8 m À 3 .…”

Section: Methodsmentioning

confidence: 99%

Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation

et al. 2014

View full text Add to dashboard Cite

Sprites are spectacular optical emissions in the mesosphere induced by transient lightning electric fields above thunderstorms. Although the streamer nature of sprites has been generally accepted, how these filamentary plasmas are initiated remains a subject of active research. Here we present observational and modelling results showing solid evidence of pre-existing plasma irregularities in association with streamer initiation in the D-region ionosphere. The video observations show that before streamer initiation, kilometre-scale spatial structures descend rapidly with the overall diffuse emissions of the sprite halo, but slow down and stop to form the stationary glow in the vicinity of the streamer onset, from where streamers suddenly emerge. The modelling results reproduce the sub-millisecond halo dynamics and demonstrate that the descending halo structures are optical manifestations of the pre-existing plasma irregularities, which might have been produced by thunderstorm or meteor effects on the D-region ionosphere.

show abstract

“…To estimate the ED changes (gradients) we have calculated percentage decrease in the ED (Table 1) using two methods. The method 1, as used by Guha et al [2010], is based upon the change in the VLF signal amplitude as compared to normal day and is used to estimate the Wait ionospheric parameters (H′ and β) which are used to estimate ED profile using relation N e (z) = 1.43 × 10 7 exp(À0.15H ')exp[(β À 0.15)(z À H ')] where N e (z) is the ED in cm À3 and H / is the D region reference height in km and β is the sharpness factor in km À1 [Wait and Spies, 1964]. The changes in ED due to the eclipse were calculated using normal daytime H′ = 71 km and β = 0.43 km À1 [Clilvered et al, 2001] and eclipse time H′ and β estimated using change in JJI signal amplitude for each TRGCP.…”

Section: 1002/2013ja019521mentioning

confidence: 99%

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Maurya¹,

Phanikumar

Singh³

et al. 2014

JGR Space Physics

View full text Add to dashboard Cite

We present first report on the periodic wave-like signatures (WLS) in the D region ionosphere during 22 July 2009 total solar eclipse using JJI, Japan, very low frequency (VLF) navigational transmitter signal (22.2 kHz) observations at stations, Allahabad, Varanasi and Nainital in Indian Sector, Busan in Korea, and Suva in Fiji. The signal amplitude increased on 22 July by about 6 and 7 dB at Allahabad and Varanasi and decreased by about 2.7, 3.5, and 0.5 dB at Nainital, Busan, and Suva, respectively, as compared to 24 July 2009 (normal day). The increase/decrease in the amplitude can be understood in terms of modal interference at the sites of modes converted at the discontinuity created by the eclipse intercepting the different transmitter-receiver great circle paths. The wavelet analysis shows the presence of WLS of period~16-40 min at stations under total eclipse and of period~30-80 min at stations under partial eclipse (~85-54% totality) with delay times between~50 and 100 min at different stations. The intensity of WLS was maximum for paths in the partially eclipsed region and minimum in the fully eclipsed region. The features of WLS on eclipse day seem almost similar to WLS observed in the nighttime of normal days (e.g., 24 July 2009). The WLS could be generated by sudden cutoff of the photo-ionization creating nighttime like conditions in the D region ionosphere and solar eclipse induced gravity waves coming to ionosphere from below and above. The present observations shed additional light on the current understanding of gravity waves induced D region ionospheric perturbations.

show abstract

Characteristics of the earth-ionosphere waveguide for VLF radio waves

Cited by 491 publications

References 11 publications

High temporal and spatial-resolution detection of D-layer fluctuations by using time-domain lightning waveforms

High temporal and spatial-resolution detection of D-layer fluctuations by using time-domain lightning waveforms

Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Contact Info

Product

Resources

About