Study of the D-region ionosphere disturbances in low-mid latitudes due to solar flares

Abstract: 64 | PDF: 54

##plugins.themes.academic_pro.article.main##

Author

  • ThS. Lê Minh Tân*

Keywords:

VLF signal
solar flares
D-region ionosphere
reflection height
electron density gradient

Abstract

The radio waves at the Very Low Frequency (VLF) from the VLF transmitters can propagate in the Earth-ionosphere waveguide (EIWG). When solar flares occur, the D-region ionosphere induces disturbances of the VLF signals. Analyzing the perturbations of the VLF/19.8 kHz signal from North West Cap, Australia recorded at Tay Nguyen University (12.65o N, 108.02o E), Vietnam and Dunedin (45.78o S, 170.47o E), New Zealand to study the disturbances of the low-mid latitude D-region ionosphere. The results reveal that the variations of amplitude/phase and Wait’s parameters (reflection height h’ and electron density gradient β) are as the sigmoid function of the peaks of X-ray flux. The increase of β via X-ray intensity in mid-latitude region is faster than that in low-latitude region. The increase in β at the mid-latitude D region is also significantly contributed by ionization at the altitudes of 50–65 km as a result of galactic cosmic rays.

References

    [1] Hargreaves, J. K (1992), The Solar – Terrestrial environment, Cambridge Univesity Press.
    [2] Barr, R., D. L. Jones, and C. J. Rodger (2000), ELF and VLF radio waves, J. of Atmos. And Solar-Terr. Phys., 62,1689 - 1718.
    [3] Davies, K. (1965), Ionospheric radio propagation, National Bureau of Standard Monogragh 80.
    [4] Mitra, A. P (1974), Ionospheric effects of solar flares, D. Reidel, Dordrecht, Holland.
    [5] Kumar A. (2007), Amplitude and phase study of sub-ionospheric VLF radio signal receiver at Suva, Master Thesis, The University of the South Pacific, Suva, Fiji.
    [6] Basak T and S. K. Chakrabarti (2013), Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares, Astrophys. Space Sci., 348, 315-326.
    [7] Dahlgren, H., T. Sundberg, B. C. Andrew, E. Koen, and S. Meyer (2011), Solar flares detected by the new narrowband VLF receiver at SANAE IV, S. Afr. J. Sci., 107 (9/10), Art.#491, 8 pages.
    [8] Grubor, D., D. Šulíc and V. Žigman (2008), Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile, Ann. Geophys., 26, 1731 -1740.
    [9] Žigman, V., D. Grubor and D. Šulíc (2007), D-region electron density evaluated from VLF amplitude time delay during X-ray solar flares, J. Atmos. Sol. Terr Phys., 69(7), 775-792.
    [10] Kumar, A. and S. Kumar (2018), Solar flare effects on D-region ionosphere using VLF measurements during low- and high-solar activity phases of solar cycle 24, Earth, Planets and Space, 70:29.
    [11] Tan, L. M. and K. Ghanbari (2016), Development of the new ELF/VLF receiver for detecting the Sudden Ionospheric Disturbances, ACTA Technica Napocensis Electronica-Telecomunicatii, 57(1), 22-26.
    [12] Wood, G. T (2004), Geo-loaction of individual lightning discharges using impulsive VLF electromagnetic waveforms, Ph.D. Thesis, Stanford University, Department of Electrical Engineering.
    [13] http://ultramsk.com/gallery/
    [14] Wait, J. R. and K. P. Spies (1964), Characteristics of the Earth-ionosphere waveguide for VLF radio waves, NBS Tech. Not.
    [15] Venkatesham, K. and R. Singh (2018), Extreme space-weather effect on D-region ionosphere in Indian low latitude region, Current Science, 114 (9), 1923 – 1926.
    [16] Thomson N. R., and M.A. Clilverd (2001), Solar flare induced ionospheric D-region enhancements from VLF amplitude observations, J. Atmos. Sol. Terr Phys.,63,1729–1737.
    [17] Heaps, M. G. (1978), Parameterization of the cosmic ray ion-pair production rate above 18 km, Planet. Space Sci., 26, 513–517.
Read more

##plugins.themes.academic_pro.article.sidebar##

Published

Apr 30, 2019
Download
PDF (Tiếng Việt)
How to Cite
ThS. Lê Minh Tân*. “Study of the D-Region Ionosphere Disturbances in Low-Mid Latitudes Due to Solar Flares”. The University of Danang - Journal of Science and Technology, vol. 17, no. 4, Apr. 2019, pp. 47-51, https://jst-ud.vn/jst-ud/article/view/480.

##plugins.themes.academic_pro.article.details##