Total solar eclipse effects on VLF signals: Observations and modeling
Mark A. Clilverd,Craig J. Rodger,Neil R. Thomson,János Lichtenberger,Péter Steinbach,Paul S. Cannon,Matthew Angling +6 more
TLDR
In this article, the amplitude and phase of four VLF transmitters in the frequency range 16-24 kHz were measured during the total solar eclipse observed in Europe on August 11, 1999.Abstract:
During the total solar eclipse observed in Europe on August 11, 1999, measurements were made of the amplitude and phase of four VLF transmitters in the frequency range 16–24 kHz Five receiver sites were set up, and significant variations in phase and amplitude are reported for 17 paths, more than any previously during an eclipse Distances from transmitter to receiver ranged from 90 to 14,510 km, although the majority were 10,000 km Negative phase changes were observed on most paths, independent of path length Although there was significant variation from path to path, the typical changes observed were ∼3 dB and ∼50° The changes observed were modeled using the Long Wave Propagation Capability waveguide code Maximum eclipse effects occurred when the Wait inverse scale height parameter β was 05 km−1 and the effective ionospheric height parameter H′ was 79 km, compared with β=043 km−1 and H′=71 km for normal daytime conditions The resulting changes in modeled amplitude and phase show good agreement with the majority of the observations The modeling undertaken provides an interpretation of why previous estimates of height change during eclipses have shown such a range of values A D region gas-chemistry model was compared with electron concentration estimates inferred from the observations made during the solar eclipse Quiet-day H′ and β parameters were used to define the initial ionospheric profile The gas-chemistry model was then driven only by eclipse-related solar radiation levels The calculated electron concentration values at 77 km altitude throughout the period of the solar eclipse show good agreement with the values determined from observations at all times, which suggests that a linear variation in electron production rate with solar ionizing radiation is reasonable At times of minimum electron concentration the chemical model predicts that the D region profile would be parameterized by the same β and H′ as the LWPC model values, and rocket profiles, during totality and can be considered a validation of the chemical processes defined within the modelread more
Citations
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Sensitive Broadband ELF/VLF Radio Reception With the AWESOME Instrument
TL;DR: The performance characteristics of the Atmospheric Weather Electromagnetic System for Observation, Modeling, and Education (AWESOME) instrument are described, including sensitivity, frequency and phase response, timing accuracy, and cross modulation.
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Subionospheric VLF perturbations associated with lightning discharges
TL;DR: In this article, the authors review the current understanding of lightning discharge associated processes that lead to changes in the characteristics of the waveguide and thus variations in the received phase and/or amplitude of VLF transmissions.
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Modeling of sub-ionospheric VLF signal perturbations associated with total solar eclipse, 2009 in Indian subcontinent
TL;DR: In this paper, a week-long campaign was conducted in the Indian sub-continent to study the low-latitude D-region ionosphere using the very low frequency (VLF) signal from the Indian Navy transmitter (call sign: VTX3) operating at 18.2 kHz.
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Modeling a large solar proton event in the southern polar atmosphere
Mark A. Clilverd,Craig J. Rodger,Thomas Ulich,Annika Seppälä,Esa Turunen,Aurelein Botman,Neil R. Thomson +6 more
TL;DR: In this paper, the effects of the Sodankyla Ion Chemistry model (SIC) electron density profiles on VLF propagation across the southern polar region during the first few days of the 4-10 November 2001 solar proton event (SPE).
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On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere
TL;DR: In this paper, a review of the use of very low frequency (VLF, 3-30 kHz) signals generated by various natural and man-made sources for the study of the ionospheric D-region and the mesosphere-lower thermosphere is presented.
References
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Whistler-induced amplitude perturbation in VLF propagation
TL;DR: In this paper, the amplitude of long-distance subionospheric VLF transmissions were found at night in association with whistlers, and both increases and decreases in signal strength were observed, depending on signal frequency and the receiving antenna.
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Experimental daytime VLF ionospheric parameters
TL;DR: In this article, the authors used measured field strengths from VLF transmitters to determine improved day-time values of ionospheric parameters to enable improved VlF propagation predictions.
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Rapid onset, rapid decay (RORD), phase and amplitude perturbations of VLF subionospheric transmissions
TL;DR: In this article, it was shown that classic Trimpis and RORDs initiated by the same sferic usually come from measurably different directions, so the lightning-induced ionisation enhancements (LIEs) which cause them must be laterally displaced.