scholarly journals Sequential observations of the local neutral wind field structure associated with E region plasma layers

2005 ◽  
Vol 110 (A4) ◽  
Author(s):  
R. L. Bishop ◽  
G. D. Earle ◽  
M. F. Larsen ◽  
C. M. Swenson ◽  
C. G. Carlson ◽  
...  
Keyword(s):  
Wind Field ◽  
Field Structure ◽  
Neutral Wind ◽  
E Region ◽  
Region Plasma

scholarly journals A model of mid-latitude E-region plasma convergence inside a planetary wave cyclonic vortex

2002 ◽  
Vol 20 (8) ◽  
pp. 1193-1201 ◽  
Author(s):  
S. Shalimov ◽  
C. Haldoupis
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Planetary Wave ◽  
Numerical Solutions ◽  
Lower Thermosphere ◽  
Plasma Transport ◽  
Neutral Wind ◽  
Prevailing Wind Direction ◽  
E Region ◽  
Region Plasma

Abstract. Recently, Shalimov et al. (1999) proposed a new mechanism for large-scale accumulation of long-lived metallic ions in the mid-latitude ionosphere driven by planetary waves in the lower thermosphere. In this mechanism, the combined action of frictional and horizontal magnetic field forces at E-region altitudes causes the plasma to converge and accumulate in large areas of positive neutral wind vorticity within a propagating planetary wave. The present paper provides a theoretical formulation for this mechanism by modelling both horizontal and vertical plasma transport effects within a planetary wave vortex, of cyclonic neutral wind. Non-steady-state numerical solutions of the ion continuity equation show that the proposed accumulation process can enhance the ionization significantly inside the planetary wave vortex but its efficiency depends strongly on altitude, whereas on the other hand, it can be complicated by vertical plasma motions. The latter, which are driven by the same planetary wave wind field under the action of the vertical Lorentz force and meridional wind forcing along the magnetic field lines, can lead to either plasma compressions or depletions, depending on the prevailing wind direction. We conclude that, for shorter times, vertical plasma transport may act constructively to the horizontal gathering process to produce considerable E-region plasma accumulation over large sectors of a planetary wave vortex of cyclonic winds.Key words. Ionosphere (ionosphere-atmosphere interactions; mid-latitude ionosphere; sporadic E-layers) – Meteorology and atmospheric dynamics (waves and tides)

scholarly journals Measurements of the E region neutral wind field

1985 ◽  
Vol 33 (4) ◽  
pp. 373-379 ◽  
Author(s):  
L.L. Cogger ◽  
J.S. Murphree ◽  
C.A. Tepley ◽  
J.W. Meriwether
Keyword(s):  
Wind Field ◽  
Neutral Wind ◽  
E Region

The Change of Aerodynamic Parameters over Beijing Urban Area during 1991-2018

2020 ◽  
Author(s):  
Xiaoman Liu
Keyword(s):  
Wind Speed ◽  
Urban Area ◽  
Wind Direction ◽  
Wind Field ◽  
Atmospheric Stability ◽  
Meteorological Condition ◽  
Field Structure ◽  
Average Height ◽  
Growth Trend ◽  
Aerodynamic Parameters

<p>       Higher and denser building groups are the most concentrated reflection of urbanization on the underlying surface reconstruction. With the continuous city expanding, urban wind field structure was changed, also the aerodynamic parameters dependent on. Based on observational data (slow-response) collected at 15 levels on Beijing 325m meteorological tower from 1991-2018, time and vertical trends of atmospheric stability, wind direction, wind speed, aerodynamic parameters were analyzed. Through Sen's slope, Mann-Kendall trend test and mutation analysis, we believe that urbanization has made a significant influence on local meteorological condition, and all the above variables mutated around the year of 1999. Before 1999, the proportion of neutral and unstable conditions declined with a trend of -0.63% and -2.0% per year respectively, and increased with a trend of +0.08% and +0.06% per year after 1999. As for wind direction, the dominant wind direction below 47m turned from southwest/northwest before 1999 to southeast after 1999, while above 47m remain unchanged as southeast, reflecting that the action range of urban impact is clearly distinguished from that of atmospheric background field. In terms of wind speed, the annual mean value trended to decrease at -0.0019m/s per year, and vertical wind speed trended to increased with height (per meter) at m/s per year, which reflected the continuous enhancement of attenuation effect of complex underlying on the near-ground wind speed. Furthermore, we found that although there was indeed a weaken tendency for wind speed in Beijing urban areas, but near neutral wind speed maintained a growth trend under 140m during 1999-2018. It was possible the deal with urban wake effect, wind field structure mutation or turbulence effect. Aerodynamic parameters  and d have undergone significant changes during the peak stage of urbanization, and tended to develop steadily with a 7-years fluctuations trend after that. In the past 28 years, d has increased from 1.34m in 1991 to 26.19m in 2018, while  has decreased from 2.75m to 1.02m. This is due to the fact that the increase of buildings average height is the result of roughness superposition. If the 7-year fluctuations trend continues, d of Beijing urban area will soon enter the next uplift period, during which the wind speed may increase slightly under nearly neutral conditions, and the cleaning effect on the pollution may be gradually enhanced.</p><p> </p>

Application of alternating codes for EISCAT observations during the ERRRIS campaign for E-region plasma irregularities

1990 ◽  
Vol 52 (6-8) ◽  
pp. 431-438 ◽  
Author(s):  
I Häggström ◽  
H Opgenoorth ◽  
P.J.S Williams ◽  
G.O.L Jones ◽  
K Schlegel
Keyword(s):  
Plasma Irregularities ◽  
E Region ◽  
Region Plasma

scholarly journals Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

2008 ◽  
Vol 26 (7) ◽  
pp. 1865-1876 ◽  
Author(s):  
D. V. Phanikumar ◽  
A. K. Patra ◽  
C. V. Devasia ◽  
G. Yellaiah
Keyword(s):  
Seasonal Variation ◽  
Seasonal Variations ◽  
Low Latitude ◽  
Plasma Irregularities ◽  
Daytime Activity ◽  
Significant Difference ◽  
E Region ◽  
Region Plasma ◽  
Present Understanding ◽  
Field Aligned Irregularities

Abstract. In this paper, we present seasonal variation of E region field-aligned irregularities (FAIs) observed using the Gadanki radar and compare them with the seasonal variation of Es observed from a nearby location SHAR. During daytime, FAIs occur maximum in summer and throughout the day, as compared to other seasons. During nighttime, FAIs occur equally in both summer and winter, and relatively less in equinoxes. Seasonal variations of Es (i.e. ftEs and fbEs) show that the daytime activity is maximum in summer and the nighttime activity is maximum in equinoxes. No relation is found between FAIs occurrence/SNR and ftEs/fbEs. FAIs occurrence, however, is found to be related well with (ftEs−fbEs). This aspect is discussed in the light of the present understanding of the mid-latitude Es-FAIs relationship. The seasonal variations of FAIs observed at Gadanki are compared in detail with those of Piura, which show a significant difference in the daytime observations. The observed difference has been discussed considering the factors governing the generation of FAIs.

Tidal signatures in sporadic E occurrence rates - migrating and nonmigrating components, and comparison with neutral wind shear

2021 ◽  
Author(s):  
Christoph Jacobi ◽  
Kanykei Kandieva ◽  
Christina Arras
Keyword(s):  
Wind Shear ◽  
Signal To Noise Ratio ◽  
Ion Concentration ◽  
Vertical Shear ◽  
Neutral Wind ◽  
High Electron ◽  
Phase Measurements ◽  
Middle Latitudes ◽  
E Region ◽  
Sporadic E

<p>In the lower ionospheric E region, shallow regions of high electron density are found, which are called sporadic E (ES) layers. ES layers consist of thin clouds of accumulated ions. They occur mainly at middle latitudes, and they are most frequently found during the summer season. ES are generally formed at heights between 90 and 120 km. At midlatitudes, their occurrence can be described through the wind shear theory. According to this theory, ES formation is due to interaction between the metallic ion concentration, the Earth’s magnetic field, and the vertical shear of the neutral wind. Here, we analyze ES occurrence rates (OR) obtained from ionospheric radio occultation measurements by the FORMOSAT-3/COSMIC constellation. To derive information on ES from RO, we use the Signal-to-Noise ratio (SNR) profiles of the GPS L1 phase measurements. If large SNR standard deviation values occur that are concentrated within a layer of less than 10 km thickness, we assume that the respective SNR profile disturbance is owing to an ES layer.</p><p>Midlatitude ES are found to be mainly connected with a migrating diurnal and semidiurnal component. Especially at high latitudes of the southern hemisphere, nonmigrating components such as a diurnal westward wave 2 and a semidiurnal westward wave 1 are also visible. Near the equator, a strong diurnal eastward wavenumber 3 component and a semidiurnal eastward wavenumber 2 component are found in summer and autumn. Terdiurnal and quarterdiurnal components are weaker than the diurnal and semidiurnal ones. We discuss seasonal and global distributions of migrating and nonmigrating components, and their relation to neutral wind shear derived from ground-based observations and numerical modeling.</p>

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