VLF phase and amplitude: daytime ionospheric parameters

McRae, Wayne; Thomson, Neil R.

doi:10.1016/s1364-6826(00)00027-4

Cited by 140 publications

(240 citation statements)

References 13 publications

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“…Inspection of published rocket profiles shows that at the time and place of PMSE events under well illuminated conditions, the electron density profiles have values of ∼4000 el/cc at 85 km altitude, which is consistent with the typical value reported by Rapp et al (2002). Typical "night-time" values for β and h at high latitudes during the summer months are likely to be 0.30 km −1 and 76 km, respectively, which give 500 el/cc at 85 km altitude (Thomson, 1993;McRae and Thomson, 2000;Friedrich et al, 2002). This coincides with the minimum 85 km background electron concentration for PMSE VHF/UHF radar observations.…”

Section: The Influence Of Biteouts On Subionospheric Vlf Propagationsupporting

confidence: 84%

“…We can estimate the electron number density levels at 85 km by using the solar zenith angle control of β and h and fitting of the ionospheric profile through experimentally determined (empirical) relationships (Thomson, 1993;McRae and Thomson, 2000). Figure 12 shows the expected diurnal variation of the electron density at the summer solstice on 21 June for latitudes of 60, 65, and 70 • .…”

Section: Profile and Frequency Dependence Of Vlf Propagation Disturbamentioning

confidence: 99%

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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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Section: The Influence Of Biteouts On Subionospheric Vlf Propagationsupporting

confidence: 84%

Section: Profile and Frequency Dependence Of Vlf Propagation Disturbamentioning

confidence: 99%

The impact of PMSE and NLC particles on VLF propagation

et al. 2004

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“…Cummer et al (1998), McRae and Thomson (2000), Han and Cummer (2010), Han and Cummer (2011), Thomson et al (2011a), Thomson et al (2011b). Han and Cummer (2010) model midlatitude daytime D region ionosphere variations also with regard to flares in the two-parameter e-density profile framework.…”

Section: Introductionmentioning

confidence: 99%

Modeling solar flare induced lower ionosphere changes using VLF/LF transmitter amplitude and phase observations at a midlatitude site

Schmitter¹

2013

Ann. Geophys.

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Remote sensing of the ionosphere bottom using long wave radio signal propagation is a still going strong and inexpensive method for continuous monitoring purposes. We present a propagation model describing the time development of solar flare effects. Based on monitored amplitude and phase data from VLF/LF transmitters gained at a mid-latitude site during the currently increasing solar cycle no. 24 a parameterized electron density profile is calculated as a function of time and fed into propagation calculations using the LWPC (Long Wave Propagation Capability). The model allows to include lower ionosphere recombination and attachment coefficients, as well as to identify the relevant forcing X-ray wavelength band, and is intended to be a small step forward to a better understanding of the solar–lower ionosphere interaction mechanisms within a consistent framework

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“…The ionospheric model is called "range exponential" with input data; the distance along the Great Circle Path (GCP) and its associated β and H parameters is used in the LWPC evaluations of VLF phase and amplitude. While Wait's parameters, β q and H q , describing the quiet diurnal, seasonal and solar cycle variations of the lower ionosphere are well determined, (Thomson, 1993;Thomson and Clilverd, 2000;McRae and Thomson, 2000), the values of these parameters describing the solar X-ray flare induced Dregion changes, are still under study. In recent papers, the β and H dependence on the solar X-ray flare peak irradiance has been deduced from VLF phase and amplitude observations (Thomson and Clilverd, 2001;McRae and Thomson, 2004;Thomson et al, 2004Thomson et al, , 2005.…”

Section: Introductionmentioning

confidence: 99%

Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

2008

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Abstract. The classification of X-ray solar flares is performed regarding their effects on the Very Low Frequency (VLF) wave propagation along the Earth-ionosphere waveguide. The changes in propagation are detected from an observed VLF signal phase and amplitude perturbations, taking place during X-ray solar flares. All flare effects chosen for the analysis are recorded by the Absolute Phase and Amplitude Logger (AbsPal), during the summer months of 2004-2007, on the single trace, Skelton (54.72 N, 2.88 W) to Belgrade (44.85 N, 20.38 E) with a distance along the Great Circle Path (GCP) D≈2000 km in length.The observed VLF amplitude and phase perturbations are simulated by the computer program Long-Wavelength Propagation Capability (LWPC), using Wait's model of the lower ionosphere, as determined by two parameters: the sharpness (β in 1/km) and reflection height (H in km). By varying the values of β and H so as to match the observed amplitude and phase perturbations, the variation of the D-region electron density height profile N e (z) was reconstructed, throughout flare duration. The procedure is illustrated as applied to a series of flares, from class C to M5 (5×10 −5 W/m 2 at 0.1-0.8 nm), each giving rise to a different time development of signal perturbation.The corresponding change in electron density from the unperturbed value at the unperturbed reflection height, i.e. N e (74 km)=2.16×10 8 m −3 to the value induced by an M5 class flare, up to N e (74 km)=4×10 10 m −3 is obtained. The β parameter is found to range from 0.30-0.49 1/km and the reflection height H to vary from 74-63 km. The changes in N e (z) during the flares, within height range z=60 to 90 km are determined, as well.

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VLF phase and amplitude: daytime ionospheric parameters

Cited by 140 publications

References 13 publications

The impact of PMSE and NLC particles on VLF propagation

The impact of PMSE and NLC particles on VLF propagation

Modeling solar flare induced lower ionosphere changes using VLF/LF transmitter amplitude and phase observations at a midlatitude site

Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

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