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Extreme Space-Weather Effect on D-Region Ionosphere in Indian Low Latitude Region


Affiliations
1 K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, India
 

The present study delineates on the observations and modelling of low latitude D-region ionosphere perturbations caused by strongest solar flare (X6.9) of solar cycle 24. An extreme space weather event occurred on 9 August 2011. To understand the severity of X-class flare on ionosphere, a comparative study was made with a low intensity C-class flare of 6 August 2011. Both flares originated from the same sunspot AR#1263. Very low frequency (VLF) waves propagating in the Earth’s ionosphere wave guide (EIWG) measured from VLF transmitter NWC (19.8 kHz) located in Australia, and recorded at Allahabad (India) were used. The recorded VLF amplitude and phase were modelled with long wavelength propagation capability code to understand solar flare-induced ionospheric variation. Modelling results revealed that the lower boundary of D-region ionosphere is lowered by 10 km during X-class and 1.0 km for C-class flare. This implies change in the properties of EIWG, and hence becomes important to observe our ionosphere on continuous basis for space weather events since ionosphere is the key medium of propagation for radio waves.

Keywords

Low Latitude, D-Region Ionosphere, Solar Flare, Solar Cycle 24, Very Low Frequency Waves.
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  • Mitra, A. P., Ionospheric Effects of Solar Flares, D. Reidel, Dordrecht-Holland, 1974.

  • Hargreaves, J. K., The Solar-Terrestrial Environment, Cambridge University Press, New York, 2003.

  • Thomson, N. R., Rodger, C. J. and Clilverd, M. A., Large solar flares and their ionospheric D-region enhancements. J. Geophys. Res., 2005; doi:10.1029/2005JA011008.

  • Maurya, A. K. et al., Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low-latitude Indian sector. J. Geophys. Res., 2012; doi:10.1029/2011JA016976.

  • Rajesh, S. et al., Very low latitude (L = 1.08) whistlers. J. Geophys. Res., 2012; doi:10.1029/2012GL054122.

  • Thomson, N. R. and Clilverd, M. A., Solar flare induced ionospheric D-region enhancements from VLF amplitude observations. J. Atmos. Solar Terr. Phys., 2001, 63(7), 1729–1737.

  • McRae, W. M. and Thomson, N. R., Solar flare induced ionospheric D-region enhancement from VLF phase and amplitude observations. J. Atmos. Solar Terr. Phys., 2004, 66, 77–87.

  • Ferguson, J. A. and Snyder, F. P., Computer programs for assessment of long wavelength radio communications, version 1.0: Full FORTRAN code user’s guide. Nav. Ocean Syst. Cent., Tech. Doc. 1773, DTIC AD-B144 839, Def. Tech. Inf. Cent, Alexandria, Va, 1990.

  • Wait, J. R. and Spies, K. P., Characteristics of the earth-ionosphere waveguide for VLF radio waves. Tech. Note 300, Natl. Bur. of Stand., Boulder, Colorado, 164.

  • Kumar, S. et al., Response of the low-latitude D region ionosphere to extreme space weather event of 14–16 December 2006. J. Geo-phys. Res., 2015; doi:10.1002/2014JA020751.


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  • Extreme Space-Weather Effect on D-Region Ionosphere in Indian Low Latitude Region

Abstract Views: 355  |  PDF Views: 119

Authors

K. Venkatesham
K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, India
Rajesh Singh
K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, India

Abstract


The present study delineates on the observations and modelling of low latitude D-region ionosphere perturbations caused by strongest solar flare (X6.9) of solar cycle 24. An extreme space weather event occurred on 9 August 2011. To understand the severity of X-class flare on ionosphere, a comparative study was made with a low intensity C-class flare of 6 August 2011. Both flares originated from the same sunspot AR#1263. Very low frequency (VLF) waves propagating in the Earth’s ionosphere wave guide (EIWG) measured from VLF transmitter NWC (19.8 kHz) located in Australia, and recorded at Allahabad (India) were used. The recorded VLF amplitude and phase were modelled with long wavelength propagation capability code to understand solar flare-induced ionospheric variation. Modelling results revealed that the lower boundary of D-region ionosphere is lowered by 10 km during X-class and 1.0 km for C-class flare. This implies change in the properties of EIWG, and hence becomes important to observe our ionosphere on continuous basis for space weather events since ionosphere is the key medium of propagation for radio waves.

Keywords


Low Latitude, D-Region Ionosphere, Solar Flare, Solar Cycle 24, Very Low Frequency Waves.

References





DOI: https://doi.org/10.18520/cs%2Fv114%2Fi09%2F1923-1926