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The Impact of PMSE and NLC Particles on VLF Propagation.

The Impact of PMSE and NLC Particles on VLF Propagation.
The Impact of PMSE and NLC Particles on VLF Propagation.
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. Associated phenomena at these altitudes are noctilucent clouds and electron density biteouts. The latter 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 500-6000 km. For profiles during the 10hrs 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 degrees 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.
Polar mesospheric Summer Echoes, VLF propagation
0992-7689
1563-1574
Nunn, D
5115be8c-b699-427b-b7df-8795398381e5
Clilverd, M
4c98eea5-db4e-4e6d-b8f5-6786819686c2
Rodger, C J
1d1e12d0-8c7e-4e33-bd69-b4fb7c397af0
Thomson, N R
ec90ccd8-7798-4e92-ae88-5ca476076492
Nunn, D
5115be8c-b699-427b-b7df-8795398381e5
Clilverd, M
4c98eea5-db4e-4e6d-b8f5-6786819686c2
Rodger, C J
1d1e12d0-8c7e-4e33-bd69-b4fb7c397af0
Thomson, N R
ec90ccd8-7798-4e92-ae88-5ca476076492

Nunn, D, Clilverd, M, Rodger, C J and Thomson, N R (2004) The Impact of PMSE and NLC Particles on VLF Propagation. Annales Geophysicae, 22 (5), 1563-1574.

Record type: Article

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. Associated phenomena at these altitudes are noctilucent clouds and electron density biteouts. The latter 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 500-6000 km. For profiles during the 10hrs 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 degrees 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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Published date: April 2004
Keywords: Polar mesospheric Summer Echoes, VLF propagation
Organisations: Electronics & Computer Science

Identifiers

Local EPrints ID: 260374
URI: http://eprints.soton.ac.uk/id/eprint/260374
ISSN: 0992-7689
PURE UUID: 042f5d83-13ef-467c-bb1f-876c91f982fe

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Date deposited: 26 Jan 2005
Last modified: 19 Jul 2019 22:38

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