scholarly journals Longitudinal Variations of Noontime Thermospheric Winds in Response to IMF Bz Temporal Oscillations: Broken Mean Circulation and Standing Feature

2020 ◽  
Author(s):  
Kedeng Zhang ◽  
Hui Wang ◽  
Wenbin Wang ◽  
Jing Liu ◽  
Jie Gao
Keyword(s):  
Southern Hemisphere ◽  
Periodic Oscillation ◽  
Meridional Wind ◽  
Field Configuration ◽  
Low Latitude ◽  
Ionosphere Model ◽  
Atmospheric Disturbances ◽  
Longitudinal Variations ◽  
Ionospheric Electric Field ◽  
Mean Circulation

Abstract By using coupled magnetosphere-thermosphere-ionosphere model, we explore the longitudinal/UT differences of the dayside neutral wind in response to the 60 min periodic oscillation of interplanetary magnetic field (IMF) Bz. The southward propagation of the travelling atmospheric disturbances (TADs) in meridional wind stands at about 20º MLat, which is related to the geomagnetic field configuration, neutral temperature and electron density changes. The meridional wind travels continuously from high to low latitude in the western southern hemisphere, while they are broken into pieces in the eastern southern hemisphere. The broken mean circulation is induced by the stronger roles of the ion drag than the pressure gradient. The ion drag shows obvious longitudinal differences associated with the penetration of the ionospheric electric field during the oscillation of IMF Bz.

scholarly journals Longitudinal variations of noontime thermospheric winds in response to IMF Bz temporal oscillations: broken mean circulation and standing feature

2021 ◽  
Author(s):  
Kedeng Zhang ◽  
Hui Wang ◽  
Wenbin Wang ◽  
Jing Liu ◽  
Jie Gao
Keyword(s):  
Periodic Oscillation ◽  
Meridional Wind ◽  
Field Configuration ◽  
Base Case ◽  
Ionosphere Model ◽  
Atmospheric Disturbances ◽  
Meridional Winds ◽  
Longitudinal Variations ◽  
Ionospheric Electric Field ◽  
Mean Circulation

Abstract By using the coupled magnetosphere-thermosphere-ionosphere model, we explore the longitudinal/UT dependences of the dayside neutral wind in response to the 60 min periodic oscillation of the interplanetary magnetic field (IMF) Bz. The southward propagation of the traveling atmospheric disturbances (TADs) in meridional wind stands at about 20º MLat, which is related to the geomagnetic field configuration, neutral temperature, and electron density changes. The meridional wind travels continuously from high to low latitude in the western southern hemisphere, with several sudden changes in the wave phase along the propagation direction. The broken mean circulation that is induced by the interaction between TADs and simultaneous responses of the meridional winds driven by oscillating solar wind conditions is induced by the stronger roles of the ion drag than the pressure gradient. Note here that the mean circulation is the background meridional winds in the base case with the IMF Bz setting to zero in the CMIT model. The ion drag shows obvious longitudinal differences associated with the penetration of the ionospheric electric field during the oscillation of IMF Bz.

scholarly journals Longitudinal variations of noontime thermospheric winds in response to IMF Bz temporal oscillations: broken mean circulation and standing feature

2020 ◽  
Author(s):  
Kedeng Zhang ◽  
Hui Wang ◽  
Wenbin Wang ◽  
Jing Liu ◽  
Jie Gao
Keyword(s):  
Southern Hemisphere ◽  
Periodic Oscillation ◽  
Meridional Wind ◽  
Field Configuration ◽  
Base Case ◽  
Ionosphere Model ◽  
Meridional Winds ◽  
Longitudinal Variations ◽  
Ionospheric Electric Field ◽  
Mean Circulation

Abstract By using coupled magnetosphere-thermosphere-ionosphere model, we explore the longitudinal/UT differences of the dayside neutral wind in response to the 60 min periodic oscillation of interplanetary magnetic field (IMF) Bz. The southward propagation of the travelling atmospheric disturbances (TADs) in meridional wind stands at about 20º MLat, which is related to the geomagnetic field configuration, neutral temperature and electron density changes. The meridional wind travels continuously from high to low latitude in the western southern hemisphere, while they are broken into pieces in the eastern southern hemisphere. The broken mean circulation that is a combined effect of TADs and simultaneous responses of the meridional winds driven by oscillating solar wind conditions is induced by the stronger roles of the ion drag than the pressure gradient. Note here that the mean circulation is the background meridional winds in the base case. The ion drag shows obvious longitudinal differences associated with the penetration of the ionospheric electric field during the oscillation of IMF Bz.

scholarly journals Longitudinal variations of noontime thermospheric winds in response to IMF Bz temporal oscillations: broken mean circulation and standing feature

2020 ◽  
Author(s):  
Kedeng Zhang ◽  
Hui Wang ◽  
Wenbin Wang ◽  
Jing Liu ◽  
Jie Gao
Keyword(s):  
Southern Hemisphere ◽  
Periodic Oscillation ◽  
Meridional Wind ◽  
Field Configuration ◽  
Base Case ◽  
Ionosphere Model ◽  
Meridional Winds ◽  
Longitudinal Variations ◽  
Ionospheric Electric Field ◽  
Mean Circulation

Abstract By using the coupled magnetosphere-thermosphere-ionosphere model, we explore the longitudinal/UT differences of the dayside neutral wind in response to the 60 min periodic oscillation of the interplanetary magnetic field (IMF) Bz. The southward propagation of the traveling atmospheric disturbances (TADs) in meridional wind stands at about 20º MLat, which is related to the geomagnetic field configuration, neutral temperature, and electron density changes. The meridional wind travels continuously from high to low latitude in the western southern hemisphere, while they are broken into pieces in the eastern southern hemisphere. The broken mean circulation that is a combined effect of TADs and simultaneous responses of the meridional winds driven by oscillating solar wind conditions is induced by the stronger roles of the ion drag than the pressure gradient. Note here that the mean circulation is the background meridional winds in the base case. The ion drag shows obvious longitudinal differences associated with the penetration of the ionospheric electric field during the oscillation of IMF Bz.

scholarly journals Quasi-biennial and quasi-triennial oscillations in the growth rates of atmospheric chlorofluorocarbons 11 and 12

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 349-358
Author(s):  
R. P. KANE
Keyword(s):  
Southern Hemisphere ◽  
Growth Rates ◽  
Southern Oscillation ◽  
Spectral Characteristics ◽  
Linear Increase ◽  
Transport Processes ◽  
Emission Rates ◽  
Low Latitude ◽  
The Difference ◽  
Prominent Peak

The 12-monthly running means of CFC-11 and CFC-12 were examined for 1977-1992. As observed by earlier workers, during 1977-1988, there was a rapid, almost linear increase of these compounds, ~70% in the northern and ~77% in the southern hemisphere. From 1988 up to 1992, growth rates were slower, more so for CFC-11 in the northern hemisphere. Superposed on this pattern were QBO, QTO (Quasi-Biennial and Quasi-Triennial Oscillations). A spectral analysis of the various series indicated the following. The 50 hPa low latitude zonal wind had one prominent QBO peak at 2.58 years and much smaller peaks at 2.00 (QBO) and 5.1 years. The Southern oscillation index represented by (T-D), Tahiti minus Darwin atmospheric pressure, had a prominent peak at 4.1 years and a smaller peak at 2.31 years. CFC-11 had only one significant peak at 3.7 years in the southern hemisphere, roughly similar to the 4.1 year (T-D) peak. CFC-12 had prominent QBO (2.16-2.33 years) in both the hemispheres and a QTO (3.6 years) in the southern hemisphere. For individual locations, CFC-11 showed barely significant QBO in the range (1.95-3.07 years), while CFC 12 showed strong QBO in the range (1.86-2.38 years). The difference in the spectral characteristics of CFC-11 and CFC 12 time series is attributed to differences in their lifetimes (44 and 180 years), source emission rates and transport processes.

Examination of the 2002 major warming in the southern hemisphere using ground-based and Odin/SMR assimilated data: stratospheric ozone distributions and tropic/mid-latitude exchange

2007 ◽  
Vol 85 (11) ◽  
pp. 1287-1300 ◽  
Author(s):  
H Bencherif ◽  
L El Amraoui ◽  
N Semane ◽  
S Massart ◽  
D Vidyaranya Charyulu ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Southern Hemisphere ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Polar Vortex ◽  
Low Latitude ◽  
Height Range ◽  
Weather Forecasts ◽  
European Centre

Following an exceptionally active winter, the 2002 Southern Hemisphere (SH) major warming occurred in late September. It was preceded by three minor warming events that occurred in late August and early September, and yielded vortex split and break-down over Antarctica. Ozone (O3 and nitrous oxide (N2O) profiles obtained during that period of time (15 August – 4 October) by the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite are assimilated into MOCAGE (Modélisation Isentrope du transport Mésoéchelle de l'Ozone Stratosphérique par Advection), a global three-dimensional chemistry transport model of Météo-France. The assimilated algorithm is a three-dimensional-FGAT built by the European Centre for Research and Advance Training in Scientific Computation (CERFACS) using the PALM (Projet d'Assimilation par Logiciel Multi-méthode) software. The assimilated O3 and N2O profiles and isentropic distributions are compared to ground-based measurements (LIDAR and balloon-sonde) and to maps of advected potential vorticity (APV). The latter is computed by the MIMOSA (Modélisation Isentrope du transport Mésoéchelle de l'Ozone Stratosphérique par Advection) model, a high-resolution advection transport model, using meteorological fields from the European Centre for Medium-Range Weather Forecasts (ECMWF). It is found that O3 concentrations retrieved by the MOCAGE–PALM assimilation system show a reasonably good agreement in the 20–28 km height range when compared with ground-based profiles. This altitude range corresponds to the intersection between the MOCAGE levels (0–28 km) and SMR O3 retrievals (20–50 km). Moreover, comparison of N2O assimilated fields with MIMOSA APV maps indicates that the dramatic split and subsequent break-down of the polar vortex, as well as the associated mixing of mid- and low-latitude stratospheric air, are well resolved and pictured by MOCAGE–PALM. The present study demonstrates also that the tremendous dynamics and associated polar vortex deformations during the 2002-austral-winter have modified ozone and nitrous oxide distributions not only at the vicinity of the polar vortex, but over topics and subtropics as well. PACS Nos.: 92.60.H–, 92.60.Hd, 92.70.Cp, 92.70.Gt

scholarly journals Zonal/meridional wind and disturbance dynamo electric field control of the low-latitude ionosphere based on the SUNDIAL/ATLAS 1 Campaign

1996 ◽  
Vol 101 (A12) ◽  
pp. 26729-26740 ◽  
Author(s):  
M. A. Abdu ◽  
J. H. A. Sobral ◽  
P. Richards ◽  
Marta M. de Gonzalez ◽  
Y. N. Huang ◽  
...  
Keyword(s):  
Electric Field ◽  
Meridional Wind ◽  
Low Latitude ◽  
Field Control ◽  
Low Latitude Ionosphere

scholarly journals Modification of conductivity due to acceleration of the ionospheric medium

2008 ◽  
Vol 26 (8) ◽  
pp. 2111-2130 ◽  
Author(s):  
V. V. Denisenko ◽  
H. K. Biernat ◽  
A. V. Mezentsev ◽  
V. A. Shaidurov ◽  
S. S. Zamay
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Electric Current ◽  
Magnetic Field Line ◽  
Conducting Layer ◽  
Low Latitude ◽  
Ionosphere Model ◽  
Zero Current ◽  
Night Side ◽  
Low Latitude Ionosphere

Abstract. A quantitative division of the ionosphere into dynamo and motor regions is performed on the base of empirical models of space distributions of ionospheric parameters. Pedersen and Hall conductivities are modified to represent an impact of acceleration of the medium because of Ampére's force. It is shown that the currents in the F2 layer are greatly reduced for processes of a few hours duration. This reduction is in particular important for the night-side low-latitude ionosphere. The International Reference Ionosphere model is used to analyze the effect quantitatively. This model gives a second high conducting layer in the night-side low-latitude ionosphere that reduces the electric field and equatorial electrojets, but intensifies night-side currents during the short-term events. These currents occupy regions which are much wider than those of equatorial electrojets. It is demonstrated that the parameter σd=σP+σHΣH/ΣP that involves the integral Pedersen and Hall conductances ΣP, ΣH ought to be used instead of the local Cowling conductivity σC in calculations of the electric current density in the equatorial ionosphere. We may note that Gurevich et al. (1976) derived a parameter similar to σd for more general conditions as those which we discuss in this paper; a more detailed description of this point is given in Sect. 6. Both, σd and σC, appear when a magnetic field line is near a nonconducting domain which means zero current through the boundary of this domain. The main difference between σd and σC is that σd definition includes the possibility for the electric current to flow along a magnetic field line in order to close all currents which go to this line from neighboring ones. The local Cowling conductivity σC corresponds to the current closure at each point of a magnetic field line. It is adequate only for a magnetic field line with constant local conductivity at the whole line when field-aligned currents do not exist because of symmetry, but σC=σd in this case. So, there is no reason to use the local Cowling conductivity while the Cowling conductance ΣC=ΣP+ΣH2/ΣP is a useful and well defined parameter.

scholarly journals Quasi 10-day wave modulation of equatorial ionization anomaly during the Southern Hemisphere stratospheric warming of 2002

2019 ◽  
Author(s):  
Xiaohua Mo
Keyword(s):  
Southern Hemisphere ◽  
Phase Relationship ◽  
Periodic Oscillation ◽  
Electron Content ◽  
Stratospheric Warming ◽  
International Gnss Service ◽  
Total Electron ◽  
Stratospheric Temperature ◽  
Equatorial Ionization Anomaly ◽  
Gps Station

Abstract. The present paper studies the perturbations in equatorial ionization anomaly (EIA) region during the Southern Hemisphere (SH) sudden stratospheric warming (SSW) of 2002, using the location of EIA crests derived from Global Positioning System (GPS) station observations and the Total Electron Content (TEC) obtained by International GNSS Service (IGS) global ionospheric TEC map (GIMs) in Asian sector. A strong quasi 10-day periodic oscillation is clearly identified in EIA region, and it has in-phase relationship between northern and southern EIA crests. An eastward phase progression of quasi 10-day wave is also seen in polar stratospheric temperature during this period, suggesting the enhanced quasi-10-day planetary wave associated with SSW produced oscillation in EIA region through modulating the equatorial fountain effect. Our results reveal some newer features of ionospheric variation that have not been reported during Northern Hemisphere (SH) SSWs.

scholarly journals Observations and model calculations of an additional layer in the topside ionosphere above Fortaleza, Brazil

1997 ◽  
Vol 15 (6) ◽  
pp. 753-759 ◽  
Author(s):  
B. Jenkins ◽  
G. J. Bailey ◽  
M. A. Abdu ◽  
I. S. Batista ◽  
N. Balan
Keyword(s):  
Vertical Component ◽  
Topside Ionosphere ◽  
Neutral Wind ◽  
Geomagnetic Equator ◽  
Low Latitude ◽  
Model Calculations ◽  
Additional Layer ◽  
Ionosphere Model

Abstract. Calculations using the Sheffield University plasmasphere ionosphere model have shown that under certain conditions an additional layer can form in the low latitude topside ionosphere. This layer (the F3 layer) has subsequently been observed in ionograms recorded at Fortaleza in Brazil. It has not been observed in ionograms recorded at the neighbouring station São Luis. Model calculations have shown that the F3 layer is most likely to form in summer at Fortaleza due to a combination of the neutral wind and the E×B drift acting to raise the plasma. At the location of São Luis, almost on the geomagnetic equator, the neutral wind has a smaller vertical component so the F3 layer does not form.

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