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Found 3 entries in the Bibliography.
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2019 |
Seasonal and source variations of migrating and nonmigrating tides are studied using Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry temperature data at 10\textdegreeN (5\textendash15\textdegreeN) for the year 2009. The migrating DW1 shows equinoctial maximum and summer minimum at low latitudes. It shows equinoctial asymmetry with larger amplitudes during spring equinox than fall equinox. The migrating semidiurnal tidal amplitude (SW2) shows larger amplitudes (~20 K) during March\textendashOctober at 30\textendash60\textdegreeS. Its seasonal variation resembles stratospheric (10\ hPa) ozone variations at southern midlatitudes. During the sudden stratospheric warming of 2009, the SW1 shows larger amplitudes over the equator and it is generated due to nonlinear interaction between SW2 and planetary wave of zonal wave number 1. The eastward nonmigrating DE4 and DE3 tides enhance in summer. The DE3 and DE4 appear to be generated due to latent heat release in the troposphere, as their amplitudes in the National Center for Environmental Prediction (NCEP)\textquoterights Precipitable water vapor (proxy for latent heat release) enhance at similar times as in mesosphere. The DW2 and DW0 tides are likely to be generated due to nonlinear interaction between DW1 and planetary wave of zonal wave number 1. The SW3 enhancement during the early winter (November-December) may be due to nonlinear interaction between DW1 and the large-amplitude DW2. The nonlinear interactions of DW1 with planetary wave and nonmigrating tides explain the summer minimum and equinoctial asymmetry of DW1. Published by: Journal of Geophysical Research: Space Physics Published on: 04/2019 YEAR: 2019   DOI: 10.1029/2018JA026190 |
2014 |
The present work describes the low-latitude ionospheric variability during an unusually prolonged (~33 h) geomagnetically disturbed condition that prevailed during 15\textendash16 July 2012. The low-latitude electron density in summer hemisphere, investigated using ground- and satellite-based observations, responded to this by generating strong negative ionospheric storm on 16 July. The maximum electron density on 16 July over Indian low latitudes was reduced by more than 50\% compared to that on a geomagnetically quiet day (14 July 2012). In contrast to the extreme reduction in total electron content (TEC) in the Northern Hemisphere, TEC from a winter hemispheric station revealed substantial (~23 total electron content unit, 1 TECU = 1016 el m-2) enhancements on the same day. This contrasting hemispherical response in TEC is suggested to be due to the combined effects of strong interhemispheric and solar-driven day-night winds. Further, very weak equatorial electrojet (EEJ) strength on 16 July indicated that the westward electric field perturbations in the low-latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes. Interestingly, despite reduction in the integrated EEJ strength on 15 July, the low-latitude electron density showed substantial enhancement, highlighting the significant effect of the positive ionospheric storm on the low-latitude ionosphere. The roles of electrodynamical/neutral-dynamical and compositional disturbances are discussed in view of these observations to understand low-latitude ionospheric response when geomagnetic disturbance persists for longer duration. Bagiya, Mala; Hazarika, Rumajyoti; Laskar, Fazlul; Sunda, Surendra; Gurubaran, S.; Chakrabarty, D.; Bhuyan, P.; Sridharan, R.; Veenadhari, B.; Pallamraju, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2014 YEAR: 2014   DOI: 10.1002/2014JA020156 low-latitude ionosphere; neutral winds; prolonged southward IMF Bz; thermospheric neutral composition |
2011 |
Bagiya, Mala; Iyer, K.; Joshi, H.; Thampi, Smitha; Tsugawa, Takuya; Ravindran, Sudha; Sridharan, R.; Pathan, B.; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011   DOI: 10.1029/2010JA015845 |
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