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A study of vTEC above Nepal exploring different calibration techniques, including a comparison with the NeQuick-2 model

Abstract : In this paper, we investigate the performance of the NeQuick 2 (NeQ-2) model with respect to Ciraolo's and Gopi's derived ionospheric vertical TEC (vTEC) during the years 2014 and 2015. GPS observables derived from dual-frequency receivers over western Nepal (Simikot, Bhimchula and Nepalganj) are processed to obtain the experimental vTEC utilizing Gopi's and Ciraolo's calibration procedures. The monthly and seasonal behavior of vTEC obtained from each calibration technique is compared with the vTEC obtained from the NeQ-2 model during a quiet period. It is observed that the vTEC value obtained from all studied approaches started to increase from 00:00 UT, reached a maximum around 08:00 UT, followed by declination, attaining a minimum value around 23:00 UT. Moreover, a comparative study showed that vTEC computed using the Ciraolo calibration technique overestimates GPS vTEC, calculated in all hours and months by Gopi's approach. In the spring and summer, vTEC derived using Ciraolo's TEC calibration overestimates NeQ-2 and underestimates it in the autumn and winter. Except for a few day hours in March and April 2014 (solar maximum), NeQ-2 prediction overestimated Gopi calibrated GPS vTEC. In daytime hours, a considerable difference is noted between one vTEC estimate with respect to another. NeQ-2 model vTEC is favourably associated with GPS vTEC obtained using the Gopi procedure in spring and correlates with the Ciraolo technique in autumn. Two GPS vTEC estimations demonstrate superior consistency in summer and winter 2 seasons over all studied stations. The study on geomagnetically disturbed conditions demonstrates that NeQ-2 is not responding to the storm influence. However, the mean absolute difference between NeQ-2 prediction and GPS vTEC procured through the Gopi approach is less on the storm event day. By contrast, it is discovered less by the Ciraolo technique when the storm is recovering (except for few cases).
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https://hal.archives-ouvertes.fr/hal-03708453
Contributor : Christine Amory-Mazaudier Connect in order to contact the contributor
Submitted on : Wednesday, June 29, 2022 - 11:18:25 AM
Last modification on : Tuesday, August 2, 2022 - 4:30:24 AM

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P. Poudel, A. Silwal, B D Ghimire, S P Gautam, M. Karki, et al.. A study of vTEC above Nepal exploring different calibration techniques, including a comparison with the NeQuick-2 model. Astrophysics and Space Science, Springer Verlag, 2022, 367 (4), pp.41. ⟨10.1007/s10509-022-04041-w⟩. ⟨hal-03708453⟩

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