The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
R K Choudhary - One of the best experts on this subject based on the ideXlab platform.
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on the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the v2 layer characteristics of the venus ionosphere under different solar activity conditions
Icarus, 2019Co-Authors: K M Ambili, Sneha Susan Babu, R K ChoudharyAbstract:Abstract Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO 2 + , CO + , C + , N 2 + , N + , He + , O + ( 2 D ) , O + ( 2 P ) , O + ( 4 S ) , O 2 + and NO + , characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and temperature and considers Venus Atmosphere consisting of CO2, O, and N2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have O 2 + as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO2, O, CO, He, N, and N2), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV2) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV2). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV2 accurately, the hmV2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.
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on the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the v2 layer characteristics of the venus ionosphere under different solar activity conditions
URSI Asia-Pacific Radio Science Conference, 2019Co-Authors: K M Ambili, Sneha Susan Babu, R K ChoudharyAbstract:Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO $_{2}^{+}$, CO$^{+}, \mathrm{C}^{+}, \mathrm{N}_{2}^{+}, \mathrm{N}^{+}$, He$^{+}, \mathrm{O}^{+}(^{2}D)$, $\mathrm{O}^{+}(^{2}P), \mathrm{O}^{+}(^{4}S), \mathrm{O}_{2}^{+}$ and NO$^{+}$, characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and considers Venus Atmosphere consisting of CO 2 , O, and N 2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have $\mathrm{O}_{2}^{+}$ as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO 2 , O, CO, He, N, and N 2 ), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV 2 ) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV 2 ). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV 2 accurately, the hmV 2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.
K M Ambili - One of the best experts on this subject based on the ideXlab platform.
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on the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the v2 layer characteristics of the venus ionosphere under different solar activity conditions
Icarus, 2019Co-Authors: K M Ambili, Sneha Susan Babu, R K ChoudharyAbstract:Abstract Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO 2 + , CO + , C + , N 2 + , N + , He + , O + ( 2 D ) , O + ( 2 P ) , O + ( 4 S ) , O 2 + and NO + , characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and temperature and considers Venus Atmosphere consisting of CO2, O, and N2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have O 2 + as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO2, O, CO, He, N, and N2), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV2) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV2). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV2 accurately, the hmV2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.
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on the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the v2 layer characteristics of the venus ionosphere under different solar activity conditions
URSI Asia-Pacific Radio Science Conference, 2019Co-Authors: K M Ambili, Sneha Susan Babu, R K ChoudharyAbstract:Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO $_{2}^{+}$, CO$^{+}, \mathrm{C}^{+}, \mathrm{N}_{2}^{+}, \mathrm{N}^{+}$, He$^{+}, \mathrm{O}^{+}(^{2}D)$, $\mathrm{O}^{+}(^{2}P), \mathrm{O}^{+}(^{4}S), \mathrm{O}_{2}^{+}$ and NO$^{+}$, characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and considers Venus Atmosphere consisting of CO 2 , O, and N 2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have $\mathrm{O}_{2}^{+}$ as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO 2 , O, CO, He, N, and N 2 ), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV 2 ) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV 2 ). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV 2 accurately, the hmV 2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.
Sneha Susan Babu - One of the best experts on this subject based on the ideXlab platform.
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on the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the v2 layer characteristics of the venus ionosphere under different solar activity conditions
Icarus, 2019Co-Authors: K M Ambili, Sneha Susan Babu, R K ChoudharyAbstract:Abstract Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO 2 + , CO + , C + , N 2 + , N + , He + , O + ( 2 D ) , O + ( 2 P ) , O + ( 4 S ) , O 2 + and NO + , characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and temperature and considers Venus Atmosphere consisting of CO2, O, and N2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have O 2 + as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO2, O, CO, He, N, and N2), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV2) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV2). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV2 accurately, the hmV2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.
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on the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the v2 layer characteristics of the venus ionosphere under different solar activity conditions
URSI Asia-Pacific Radio Science Conference, 2019Co-Authors: K M Ambili, Sneha Susan Babu, R K ChoudharyAbstract:Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO $_{2}^{+}$, CO$^{+}, \mathrm{C}^{+}, \mathrm{N}_{2}^{+}, \mathrm{N}^{+}$, He$^{+}, \mathrm{O}^{+}(^{2}D)$, $\mathrm{O}^{+}(^{2}P), \mathrm{O}^{+}(^{4}S), \mathrm{O}_{2}^{+}$ and NO$^{+}$, characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and considers Venus Atmosphere consisting of CO 2 , O, and N 2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have $\mathrm{O}_{2}^{+}$ as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO 2 , O, CO, He, N, and N 2 ), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV 2 ) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV 2 ). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV 2 accurately, the hmV 2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.
Richard Swinbank - One of the best experts on this subject based on the ideXlab platform.
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The SPARC Intercomparison of Middle-Atmosphere Climatologies
Journal of Climate, 2004Co-Authors: William J. Randel, Petra M. Udelhofen, Eric Fleming, Marvin A. Geller, Mel Gelman, Kevin Hamilton, David J. Karoly, Dave Ortland, Steve Pawson, Richard SwinbankAbstract:An updated assessment of uncertainties in ‘‘observed’’ climatological winds and temperatures in the middle Atmosphere (over altitudes ;10‐80 km) is provided by detailed intercomparisons of contemporary and historic datasets. These datasets include global meteorological analyses and assimilations, climatologies derived from research satellite measurements, historical Reference Atmosphere circulation statistics, rocketsonde wind and temperature data, and lidar temperature measurements. The comparisons focus on a few basic circulation statistics (temperatures and zonal winds), with special attention given to tropical variability. Notable differences are found between analyses for temperatures near the tropical tropopause and polar lower stratosphere, temperatures near the global stratopause, and zonal winds throughout the Tropics. Comparisons of historical Reference Atmosphere and rocketsonde temperatures with more recent global analyses show the influence of decadal-scale cooling of the stratosphere and mesosphere. Detailed comparisons of the tropical semiannual oscillation (SAO) and quasibiennial oscillation (QBO) show large differences in amplitude between analyses; recent data assimilation schemes show the best agreement with equatorial radiosonde, rocket, and satellite data.
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Compilation of wind data for the Upper Atmosphere Research Satellite (UARS) Reference Atmosphere Project
Journal of Geophysical Research, 2003Co-Authors: Richard Swinbank, D. A. OrtlandAbstract:[1] The aim of the UARS (Upper Atmosphere Research Satellite) Reference Atmosphere Project (URAP) is to provide a comprehensive zonal mean Reference description of the stratosphere using measurements from instruments on board the UARS. A data set has been produced which describes the monthly zonal mean zonal winds from the surface to the upper mesosphere. Wind measurements from the High Resolution Doppler Imager (HRDI) were combined with results from the Met Office stratospheric data assimilation system. Balanced winds derived from the URAP temperature data set were used to bridge the gap between the stratospheric winds and HRDI mesospheric winds.
C Mclandress - One of the best experts on this subject based on the ideXlab platform.
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the seasonal variation of the propagating diurnal tide in the mesosphere and lower thermosphere part ii the role of tidal heating and zonal mean winds
Journal of the Atmospheric Sciences, 2002Co-Authors: C MclandressAbstract:A linear mechanistic tidal model is used to understand the mechanisms responsible for the seasonal variation of the propagating diurnal tide in the mesosphere and lower thermosphere simulated in the Canadian Middle Atmosphere Model (CMAM). The linear model uses a spectral approach to represent the horizontal structure of the tidal perturbations and employs dissipative processes that do not depend on season. By constraining the model with the zonal mean zonal winds, zonal mean temperatures, and tidal heating from the CMAM, the relative role of each of these terms is assessed. The linear model is able to reproduce all of the important tidal features found in the CMAM, in particular the semiannual amplitude variation in the lower thermosphere at low latitudes that is seen in observations. From this analysis the effects of both heating and mean winds are found to be responsible for the seasonal variation of the tidal amplitude, while variations in the tidal phase are attributed solely to changes in the mean winds. The strong sensitivity of the tide to the mean winds is the novel result of this study. This sensitivity is attributed to latitudinal shears in the zonal mean easterlies in the summer mesosphere. Although these shears occur on an annual basis, their impact on tidal amplitudes in the lower thermosphere is semiannual as a result of the 6-month shift in seasons between the two hemispheres. Simulations using observational datasets from the Committee on Space Research (COSPAR) International Reference Atmosphere (CIRA) and the High Resolution Doppler Imager (HRDI) reveal significant differences in the resulting tidal structure from that obtained using the CMAM winds, and point to possible deficiencies in these datasets.
