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Found 6 entries in the Bibliography.
Showing entries from 1 through 6
| 2020 |
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Yasyukevich (2018) showed an increase in the daytime GUVI [O/N2] along 88E during the peak and decaying period of major warmings. Furthermore, Pedatella et al. (2016), using Kakoti, Geetashree; Kalita, Bitap; Bhuyan, PK; Baruah, S; Wang, K; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2020 DOI: 10.1029/2020JA028570 |
| 2017 |
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TEC measured at Dibrugarh (27.5\textdegreeN, 94.9\textdegreeE, 17.5\textdegreeN Geomag.) from 2009 to 2014 is used to study its temporal characteristics during the ascending half of solar cycle 24. The measurements provide an opportunity to assess the diurnal, seasonal and longterm predictability of the IRI 2012 (with IRI Nequick, IRI01-corr, IRI 2001topside options) during this solar cycle which is distinctively low in magnitude compared to the previous cycles. The low latitude station Dibrugarh is normally located at the poleward edge of the northern EIA. A semi-annual variation in GPS TEC is observed with the peaks occurring in the equinoxes. The peak in spring (March, April) is higher than that in autumn (September, October) irrespective of the year of observation. The spring autumn asymmetry is also observed in IRI TEC. In contrast, the winter (November, December, January, February) anomaly is evident only in high activity years. TEC bears a distinct nonlinear relationship with 10.7\ cm solar flux (F10.7). TEC increases linearly with F10.7 up to about 125\ sfu beyond which it tends to saturate. The correlation between TEC and solar flux is found to be a function of local time and peaks at 10:00\ LT. TEC varies nonlinearly with solar EUV flux similar to its variation with F10.7. The nonlinearity is well captured by the IRI. The saturation of TEC at high solar activity is attributed to the inability of the ionosphere to accommodate more ionization after it reaches the level of saturation ion pressure. Annual mean TEC increased from the minimum in 2009 almost linearly till 2012, remains at the same level in 2013 and then increased again in 2014. IRI TEC shows a linear increase from 2009 to 2014. IRI01-corr and IRI-NeQuick TEC are nearly equal at all local times, season and year of observation while IRI-2001 simulated TEC are always higher than that simulated by the other two versions. The IRI 2012 underestimates the TEC at about all local times except for a few hours in the midday in all season or year of observation. The discrepancy between model and measured TEC is high in spring and in the evening hours. The consistent underestimation of the TEC at this longitude by the IRI may be attributed to the inadequate ingestion of F region data from this longitude sector into the model and exclusion of the plasmaspheric content. Kakoti, Geetashree; Bhuyan, Pradip; Hazarika, Rumajyoti; Published by: Advances in Space Research Published on: 07/2017 YEAR: 2017 DOI: 10.1016/j.asr.2016.09.002 |
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Kakoti, Geetashree; Bhuyan, Pradip; Hazarika, Rumajyoti; Published by: Advances in Space Research Published on: |
| 2016 |
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The effects of the St. Patrick\textquoterights Day geomagnetic storms of 2013 and 2015 in the equatorial and low-latitude regions of both hemispheres in the 100\textdegreeE longitude sector is investigated and compared with the response in the Indian sector at 77\textdegreeE. The data from a chain of ionosondes and GPS/Global Navigation Satellite Systems receivers at magnetic conjugate locations in the 100\textdegreeE sector have been used. The perturbation in the equatorial zonal electric field due to the prompt penetration of the magnetospheric convective under shielded electric field and the over shielding electric field gives rise to rapid fluctuations in the F2 layer parameters. The direction of IMF Bz and disturbance electric field perturbations in the sunset/sunrise period is found to play a crucial role in deciding the extent of prereversal enhancement which in turn affect the irregularity formation (equatorial spread F) in the equatorial region. The northward (southward) IMF Bz in the sunset period inhibited (supported) the irregularity formation in 2015 (2013) in the 100\textdegreeE sector. Large height increase (hmF2) during sunrise produced short-duration irregularities during both the storms. The westward disturbance electric field on 18 March inhibited the equatorial ionization anomaly causing negative (positive) storm effect in low latitude (equatorial) region. The negative effect was amplified in low midlatitude by disturbed thermospheric composition which produced severe density/total electron content depletion. The longitudinal and hemispheric asymmetry of storm response is observed and attributed to electrodynamic and thermospheric differences. Kalita, Bitap; Hazarika, Rumajyoti; Kakoti, Geetashree; Bhuyan, P.; Chakrabarty, D.; Seemala, G.; Wang, K.; Sharma, S.; Yokoyama, T.; Supnithi, P.; Komolmis, T.; Yatini, C; Le Huy, M.; Roy, P.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2016 YEAR: 2016 DOI: 10.1002/2016JA023119 |
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The GUVI data used here are provided through support from the NASA MO&DA program. The GUVI instrument was designed and built by The Aerospace Corporation and The John Kalita, Bitap; Hazarika, Rumajyoti; Kakoti, Geetashree; Bhuyan, PK; Chakrabarty, D; Seemala, Gopi; Wang, K; Sharma, S; Yokoyama, T; Supnithi, P; , others; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2016 DOI: 10.1002/2016JA023119 |
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Kalita, Bitap; Hazarika, Rumajyoti; Kakoti, Geetashree; Bhuyan, PK; Chakrabarty, D; Seemala, Gopi; Wang, K; Sharma, S; Yokoyama, T; Supnithi, P; , others; Published by: Journal of Geophysical Research: Space Physics Published on: |
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