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Venkatesham, K.
- Extreme Space-Weather Effect on D-Region Ionosphere in Indian Low Latitude Region
Abstract Views :241 |
PDF Views:82
Authors
Affiliations
1 K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, IN
1 K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, IN
Source
Current Science, Vol 114, No 09 (2018), Pagination: 1923-1926Abstract
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.Full Text
References
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- Extreme space weather events of solar cycle 24: X-class solar flares and their impact on the low-latitude D-region ionosphere
Abstract Views :139 |
PDF Views:70
Authors
Affiliations
1 KSK Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Prayagraj 211 506, India., IN
2 Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow 226 025, India., IN
3 K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Prayagraj 221 002, India., IN
1 KSK Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Prayagraj 211 506, India., IN
2 Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow 226 025, India., IN
3 K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Prayagraj 221 002, India., IN
Source
Current Science, Vol 124, No 7 (2023), Pagination: 812-819Abstract
X-class solar flares, which occurred in the daytime from 2008 to 2016 during solar cycle 24, were studied for their influence on the lower ionosphere over the low-equatorial Indian region. To understand the D-region behaviour during flare events, we used the very low frequency (VLF) navigational transmitter NWC (19.8 kHz) signal recorded at Pryagraj, Uttar Pradesh, India. A total of seven parameters were estimated: (i) the magnitude of X-ray flux, (ii) VLF signal rising amplitude perturbation (SRAP), (iii) X-ray flux and NWC signal start time difference (STD), (iv) peak time difference (PTD), (v) Wait’s ionospheric parameters h′ (reference height), (vi) β (sharpness factor) and (vii) D-region electron density difference (EDD) to determine the overall effect of solar flares on the D-region. The results suggest that three parameters (X-ray flux, SRAP and h′) show a decreasing trend through the linear fit line, two parameters (β and EDD) show an increasing trend, while the remaining two parameters show a mixed trend (decrease during low activity and increase during high activity). Further, the trend line during the diurnal variation shows an increasing trend for X-ray flux, PTD and h′, and a decreasing trend for SRAP, STD, β and EDD. Deviation in the case of individual events may indicate the dependence of these parameters on the seasons as well. The present study will provide the base for more robust analysis and modelling work in the future to understand the complexity of ionospheric change during flare events, and to develop a predictive model for space weather mitigation.Keywords
D-Region Ionosphere, Space Weather, Solar Cycle, Solar Flares, Trend Line, Vlf Waves.Full Text
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