scholarly journals Annual and seasonal variations in the low-latitude topside ionosphere

1998 ◽  
Vol 16 (8) ◽  
pp. 974-985 ◽  
Author(s):  
Y. Z. Su ◽  
G. J. Bailey ◽  
K.-I. Oyama
Keyword(s):  
Seasonal Variations ◽  
Topside Ionosphere ◽  
Neutral Wind ◽  
Electron Densities ◽  
Low Latitude ◽  
Time Model ◽  
Model Calculations ◽  
Neutral Gas ◽  
Summer Hemisphere ◽  
Winter Hemisphere

Abstract. Annual and seasonal variations in the low-latitude topside ionosphere are investigated using observations made by the Hinotori satellite and the Sheffield University Plasmasphere Ionosphere Model (SUPIM). The observed electron densities at 600 km altitude show a strong annual anomaly at all longitudes. The average electron densities of conjugate latitudes within the latitude range ±25° are higher at the December solstice than at the June solstice by about 100 during daytime and 30 during night-time. Model calculations show that the annual variations in the neutral gas densities play important roles. The model values obtained from calculations with inputs for the neutral densities obtained from MSIS86 reproduce the general behaviour of the observed annual anomaly. However, the differences in the modelled electron densities at the two solstices are only about 30 of that seen in the observed values. The model calculations suggest that while the differences between the solstice values of neutral wind, resulting from the coupling of the neutral gas and plasma, may also make a significant contribution to the daytime annual anomaly, the E×B drift velocity may slightly weaken the annual anomaly during daytime and strengthen the anomaly during the post-sunset period. It is suggested that energy sources, other than those arising from the 6 difference in the solar EUV fluxes at the two solstices due to the change in the Sun-Earth distance, may contribute to the annual anomaly. Observations show strong seasonal variations at the solstices, with the electron density at 600 km altitude being higher in the summer hemisphere than in the winter hemisphere, contrary to the behaviour in NmF2. Model calculations confirm that the seasonal behaviour results from effects caused by transequatorial component of the neutral wind in the direction summer hemisphere to winter hemisphere.

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.

scholarly journals Effects of neutral wind on the electron temperature at a height of 600 km in the low latitude region

1996 ◽  
Vol 14 (3) ◽  
pp. 290-296 ◽  
Author(s):  
S. Watanabe ◽  
K.-I. Oyama
Keyword(s):  
Electron Temperature ◽  
Thermal Structure ◽  
Early Morning ◽  
Neutral Wind ◽  
Low Latitude ◽  
Magnetic Declination ◽  
Flux Intensity ◽  
Latitude Region ◽  
Low Latitude Ionosphere ◽  
Winter Hemisphere

Abstract. Electron temperature observed by the Hinotori satellite with the low inclination at the height of ~600 km was studied in terms of local time, season, latitude, magnetic declination and solar flux intensity during a 16-month period from 1981 to 1982. The electron temperatures show steep rise in the early morning (well known as morning overshoot), decrease after that and again increase at ~18 hours (hereafter named as evening overshoot). Generally the morning overshoot becomes more enhanced in the winter hemisphere and for higher solar fluxes. The evening overshoot becomes more pronounced in the mid-latitude in all seasons and more enhanced in the winter hemisphere in the same way as the morning overshoot. A difference is seen between 210°–285° and 285°–360° longitudes where magnetic declination is different. The longitudinal dependence of electron temperature indicates that the neutral wind also contributes to the thermal structure in the low latitude ionosphere.

A computational study of the effect of geomagnetic activity on the planetary circulation of the Earth’s atmosphere

2016 ◽  
pp. 4451-4459
Author(s):  
I. V. Mingalev ◽  
K. G. Orlov ◽  
V. S. Mingalev
Keyword(s):  
Mathematical Model ◽  
Geomagnetic Activity ◽  
Computational Study ◽  
Three Dimensional ◽  
Neutral Wind ◽  
Wind System ◽  
Model Calculations ◽  
Global Circulation ◽  
Neutral Gas ◽  
The Mathematical Model

The effect of geomagnetic activity on the global circulation in the Earth’s atmosphere is studied with the help of the non-hydrostatic mathematical model, developed earlier in the Polar Geophysical Institute. The mathematical model allows us to calculate three-dimensional global distributions of the zonal, meridional, and vertical components of the wind velocity and neutral gas density in the layer surrounding the Earth globally and stretching from the ground up to the altitude of 126 km. Simulations were performed for the summer period in the northern hemisphere (16 July) and for three distinct values of geomagnetic activity (Kp=1, 4 and 7). The simulation results indicated that the effect of geomagnetic activity on the global neutral wind system may be essential not only above 80 km but also below this altitude (in the mesosphere, stratosphere and troposphere). A physical mechanism, responsible for the influence of geomagnetic activity on the global neutral wind system in the mesosphere, stratosphere and troposphere, has been established with the help of the model calculations.

scholarly journals A modelling study of the latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum

2000 ◽  
Vol 18 (11) ◽  
pp. 1435-1446 ◽  
Author(s):  
G. J. Bailey ◽  
M. H. Denton ◽  
R. A. Heelis ◽  
S. Venkatraman
Keyword(s):  
Zonal Wind ◽  
Solar Maximum ◽  
Meridional Wind ◽  
Topside Ionosphere ◽  
Longitudinal Variations ◽  
Summer Hemisphere ◽  
Declination Angle ◽  
Northern Winter ◽  
Latitudinal Variations ◽  
Winter Hemisphere

Abstract. Latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum have been examined by using values modelled by SUPIM (Sheffield University Plasmasphere Ionosphere Model) and observations made by the DMSP F10 satellite at 21.00 LT near 800 km altitude. The modelled values confirm that the crests observed near 15° latitude in the winter hemisphere are due to adiabatic heating and the troughs observed near the magnetic equator are due to adiabatic cooling as plasma is transported along the magnetic field lines from the summer hemisphere to the winter hemisphere. The modelled values also confirm that the interhemispheric plasma transport needed to produce the required adiabatic heating/cooling can be induced by F-region neutral winds. It is shown that the longitudinal variations in the observed troughs and crests arise mainly from the longitudinal variations in the magnetic meridional wind. At longitudes where the magnetic declination angle is positive the eastward geographic zonal wind combines with the northward (summer hemisphere to winter hemisphere) geographic meridional wind to enhance the northward magnetic meridional wind. This leads to deeper troughs and enhanced crests. At longitudes where the magnetic declination angle is negative the eastward geographic zonal wind opposes the northward geographic meridional wind and the trough depth and crest values are reduced. The characteristic features of the troughs and crests depend, in a complicated manner, on the field-aligned flow of plasma, thermal conduction, and inter-gas heat transfer. At the latitudes of the troughs/crests, the low/high plasma temperatures lead to increased/decreased plasma concentrations.Key words: Ionosphere (equatorial ionosphere; ionosphere-atmosphere interactions)

The characteristics of transforming coordinates from the geocentric system WGS-84 for the Mercator projection under low latitudes conditions

2018 ◽  
Vol 940 (10) ◽  
pp. 2-6
Author(s):  
J.A. Younes ◽  
M.G. Mustafin
Keyword(s):  
Coordinate System ◽  
Satellite System ◽  
Programming Algorithm ◽  
Low Latitude ◽  
Model Calculations ◽  
Mercator Projection ◽  
Low Latitudes ◽  
Rectangular Coordinates ◽  
Global Navigation Satellite ◽  
Coordination Methods

The issue of calculating the plane rectangular coordinates using the data obtained by the satellite observations during the creation of the geodetic networks is discussed in the article. The peculiarity of these works is in conversion of the coordinates into the Mercator projection, while the plane coordinate system on the base of Gauss-Kruger projection is used in Russia. When using the technology of global navigation satellite system, this task is relevant for any point (area) of the Earth due to a fundamentally different approach in determining the coordinates. The fact is that satellite determinations are much more precise than the ground coordination methods (triangulation and others). In addition, the conversion to the zonal coordinate system is associated with errors; the value at present can prove to be completely critical. The expediency of using the Mercator projection in the topographic and geodetic works production at low latitudes is shown numerically on the basis of model calculations. To convert the coordinates from the geocentric system with the Mercator projection, a programming algorithm which is widely used in Russia was chosen. For its application under low-latitude conditions, the modification of known formulas to be used in Saudi Arabia is implemented.

Isopotential points in square-wave voltammetry of reversible electrode reactions

2009 ◽  
Vol 74 (10) ◽  
pp. 1489-1501 ◽  
Author(s):  
Marina Zelić ◽  
Milivoj Lovrić
Keyword(s):  
Square Wave Voltammetry ◽  
Electrode Reaction ◽  
Time Model ◽  
Model Calculations ◽  
Square Wave ◽  
Electrode Reactions ◽  
Wave Voltammetry ◽  
Electron Transfer Processes ◽  
Diagnostic Criterion ◽  
First Time

Isopotential points in square-wave voltammetry are described for the first time. Model calculations and real measurements (performed with UO22+ and Eu3+ in perchlorate and bromide solutions, respectively) indicate that such an intersection could be observed when backward components of the net response, resulting from an increase in frequency or reactant concentration, are presented together. The electrode reaction should be fully reversible because quasireversible or slower electron transfer processes give the isopoints only at increasing reactant concentrations but not at increasing square-wave frequencies. The effect could be used as an additional diagnostic criterion for recognition of reversible electrode reactions where products remain dissolved in the electrolyte solution.

scholarly journals Time delay and duration of ionospheric total electron content responses to geomagnetic disturbances

2010 ◽  
Vol 28 (3) ◽  
pp. 795-805 ◽  
Author(s):  
J. Liu ◽  
B. Zhao ◽  
L. Liu
Keyword(s):  
Time Delay ◽  
Local Time ◽  
Positive Phase ◽  
Negative Phase ◽  
Electron Content ◽  
Geomagnetic Disturbances ◽  
Total Electron ◽  
Low Latitudes ◽  
Summer Hemisphere ◽  
Winter Hemisphere

Abstract. Although positive and negative signatures of ionospheric storms have been reported many times, global characteristics such as the time of occurrence, time delay and duration as well as their relations to the intensity of the ionospheric storms have not received enough attention. The 10 years of global ionosphere maps (GIMs) of total electron content (TEC) retrieved at Jet Propulsion Laboratory (JPL) were used to conduct a statistical study of the time delay of the ionospheric responses to geomagnetic disturbances. Our results show that the time delays between geomagnetic disturbances and TEC responses depend on season, magnetic local time and magnetic latitude. In the summer hemisphere at mid- and high latitudes, the negative storm effects can propagate to the low latitudes at post-midnight to the morning sector with a time delay of 4–7 h. As the earth rotates to the sunlight, negative phase retreats to higher latitudes and starts to extend to the lower latitude toward midnight sector. In the winter hemisphere during the daytime and after sunset at mid- and low latitudes, the negative phase appearance time is delayed from 1–10 h depending on the local time, latitude and storm intensity compared to the same area in the summer hemisphere. The quick response of positive phase can be observed at the auroral area in the night-side of the winter hemisphere. At the low latitudes during the dawn-noon sector, the ionospheric negative phase responses quickly with time delays of 5–7 h in both equinoctial and solsticial months. Our results also manifest that there is a positive correlation between the intensity of geomagnetic disturbances and the time duration of both the positive phase and negative phase. The durations of both negative phase and positive phase have clear latitudinal, seasonal and magnetic local time (MLT) dependence. In the winter hemisphere, long durations for the positive phase are 8–11 h and 12–14 h during the daytime at middle and high latitudes for 20≤Ap<40 and Ap≥40.

scholarly journals Numerical Modeling of the Influence of Solar Activity on the Global Circulation in the Earth’s Mesosphere and Lower Thermosphere

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Igor Mingalev ◽  
Victor Mingalev
Keyword(s):  
Solar Activity ◽  
Large Scale ◽  
Input Parameter ◽  
Lower Thermosphere ◽  
Vertical Component ◽  
Neutral Wind ◽  
Wind System ◽  
Model Calculations ◽  
Global Circulation ◽  
Mesosphere And Lower Thermosphere

The nonhydrostatic model of the global neutral wind system of the earth’s atmosphere, developed earlier in the Polar Geophysical Institute, is utilized to investigate how solar activity affects the formation of the large-scale global circulation of the mesosphere and lower thermosphere. The peculiarity of the utilized model consists in that the internal energy equation for the neutral gas is not solved in the model calculations. Instead, the global temperature field is assumed to be a given distribution, that is, the input parameter of the model. Moreover, in the model calculations, not only the horizontal components but also the vertical component of the neutral wind velocity is obtained by means of a numerical solution of a generalized Navier-Stokes equation for compressible gas, so the hydrostatic equation is not applied. The simulation results indicate that solar activity ought to influence considerably on the formation of global neutral wind system in the mesosphere and lower thermosphere. The influence is conditioned by the vertical transport of air from the lower thermosphere to the mesosphere and stratosphere. This transport may be rather different under distinct solar activity conditions.

DMSP F8 observations of the mid-latitude and low-latitude topside ionosphere near solar minimum

1994 ◽  
Vol 99 (A3) ◽  
pp. 3817 ◽  
Author(s):  
M. E. Greenspan ◽  
W. J. Burke ◽  
F. J. Rich ◽  
W. J. Hughes ◽  
R. A. Heelis
Keyword(s):  
Solar Minimum ◽  
Topside Ionosphere ◽  
Low Latitude
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