Experimental Observation of Magnetic Field Effects on VLF Propagation at Night

Bickel, J. E.; Ferguson, J. A.; Stanley, Gordon

doi:10.1029/rs005i001p00019

Cited by 60 publications

(42 citation statements)

References 6 publications

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“…Airborne amplitude recordings, conducted continuously along flights over portions of the propagation baselines, observed that there was more attenuation on the east-to-west than on the west-to-east path (see Figs. 7-8 and discussion thereof, in Bickel et al, 1970). On the other hand, the amplitudes on the east-to-west path were highly variable from day to day.…”

Section: Discussionmentioning

confidence: 97%

“…Two of these reports are from the United States Naval Electronics Laboratory Center or NELC (subsequently named Naval Ocean Systems Center or NOSC) and deal with the same dataset, gathered in 1969. The earlier of these reports (Bickel et al, 1970) compared signal-propagation paths from Hawaii roughly east-to-west to Wake Island, and from Hawaii roughly west-to-east to southern California. The signal was the 23.4-kHz transmission from the NPM beacon in Hawaii.…”

Section: Discussionmentioning

confidence: 99%

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Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: energy-reflectivity spectrum

2008

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Abstract. We analyze data on radio-reflection from the D-region of the lower ionosphere, retrieving the energyreflection coefficient in the frequency range ∼5-95 kHz. The data are the same as developed for a recent study of ionospheric-reflection height, and are based on recordings of powerful (multi-Gigawatt) radio emissions from a type of narrow (∼10 µs) lightning discharge known as "Narrow Bipolar Events". The sequential appearance of first the groundwave signal, and then the ionospheric single-hop reflection signal, permits us to construct the energy-reflection ratio. We infer the energy reflection's statistical variation with solar zenith angle, angle-of-incidence, frequency, and propagation azimuth. There is also a marginally-significant response of the energy reflectivity to solar X-ray flux density. Finally, we review the relationship of our results to previous published reports.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: energy-reflectivity spectrum

2008

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“…Moreover, an MF radar requires a large facility. Standard radio wave signals propagated from VLF and low frequency (LF) transmitters have also been used to measure the height variation of the D region, based on phase and intensity modulations [e.g., Bickel et al, 1970;Thomas and Harrison, 1970;Thomson et al, 2007], but the possible region for electron density measurements is limited along the propagation path between the transmitter and the receiver.…”

Section: Introductionmentioning

confidence: 99%

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

2011

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[1] We investigated, for the first time, long-term variations in reflection heights of tweek atmospherics based on very low frequency (VLF) observations at Kagoshima, Japan. The results revealed the effects of the solar cycle on the nighttime lower ionosphere at low to middle latitudes. The tweek reflection heights on geomagnetically quiet days were analyzed every month over three solar cycles by using an automated spectral fitting procedure to estimate the cutoff frequency. The average and standard deviation of the reflection height were 95.9 km and ±3.1 km, respectively. Typical periods of time variation for the reflection height were 13.3, 3.2, 1.3, 1.0, 0.6, and 0.5 years. The variations in tweek reflection heights did not show simple anticorrelation with solar activity. The correlation coefficient between tweek reflection height and sunspot number was 0.03 throughout the three solar cycles. Hilbert-Huang transform analysis successfully indicated the presence of 0.5-1.5 year and ∼10 year variations as intrinsic mode functions (IMF). The decomposed IMF with the ∼10 year variation had a positive correlation with sunspot numbers and a negative correlation with galactic cosmic rays (GCRs). We hypothesize that these variations in tweek reflection heights could be caused by coupling of several ionization effects at the D and lower E regions, effects such as geocorona, GCRs, particle precipitation, and variations in neutral density in the lower thermosphere. Among these processes, the geocorona and particle precipitation could show negative correlation, while the GCRs and neutral density could show positive correlation with solar activities.Citation: Ohya, H., K. Shiokawa, and Y. Miyoshi (2011), Long-term variations in tweek reflection height in the D and lower E regions of the ionosphere,

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“…The program used for the mode parameter calculations reported here is a slightly modified version of the NOSC program MODEFNDR which is very similar to MODESRCH. Further discussion of the very complex mathematical details of the NOSC VLF propagation program and comparisons with experimental data can be found in Bickel et al (1970) and Pappert and Hitney (1988). The output of MODEFNDR then comprises the excitation factors, height gain functions, attenuation factors and horizontal wave numbers for allowable VLF modes.…”

Section: Details Of the Computation Of Vlf Propagation Perturbationsmentioning

confidence: 99%

The impact of PMSE and NLC particles on VLF propagation

et al. 2004

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Abstract. PMSE or Polar Mesosphere Summer Echoes are a well-known phenomenon in the summer northern polar regions, in which anomalous VHF/UHF radar echoes are returned from heights ∼85 km. Noctilucent clouds and electron density biteouts are two phenomena that sometimes occur together with PMSE. Electron density biteouts are electron density depletion layers of up to 90%, which may be several kms thick. Using the NOSC Modefndr code based on Wait's modal theory for subionospheric propagation, we calculate the shifts in received VLF amplitude and phase that occur as a result of electron density biteouts. The code assumes a homogeneous background ionosphere and a homogeneous biteout layer along the Great Circle Path (GCP) corridor, for transmitter receiver path lengths in the range of 500-6000 km.For profiles during the 10 h about midnight and under quiet geomagnetic conditions, where the electron density at 85 km would normally be less than 500 el/cc, it was found that received signal perturbations were significant, of the order of 1-4 dB and 5-40 • of phase. Perturbation amplitudes increase roughly as the square root of frequency. At short range perturbations are rather erratic, but more consistent at large ranges, readily interpretable in terms of the shifts in excitation factor, attenuation factor and v/c ratios for Wait's modes. Under these conditions such shifts should be detectable by a well constituted experiment involving multiple paths and multiple frequencies in the north polar region in summer. It is anticipated that VLF propagation could be a valuable diagnostic for biteout/PMSE when electron density at 85 km is under 500 el/cc, under which circumstances PMSE are not directly detectable by VHF/UHF radars.

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Experimental Observation of Magnetic Field Effects on VLF Propagation at Night

Cited by 60 publications

References 6 publications

Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: energy-reflectivity spectrum

Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: energy-reflectivity spectrum

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

The impact of PMSE and NLC particles on VLF propagation

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