scholarly journals Yearly variations in the low-latitude topside ionosphere

2000 ◽  
Vol 18 (7) ◽  
pp. 789-798 ◽  
Author(s):  
G.J. Bailey ◽  
Y. Z. Su ◽  
K.-I. Oyama
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Plasma Temperature ◽  
Magnetic Activity ◽  
Topside Ionosphere ◽  
Low Latitude ◽  
Yearly Variation ◽  
The North ◽  
The Asymmetry ◽  
The Relationship

Abstract. Observations made by the Hinotori satellite have been analysed to determine the yearly variations of the electron density and electron temperature in the low-latitude topside ionosphere. The observations reveal the existence of an equinoctial asymmetry in the topside electron density at low latitudes, i.e. the density is higher at one equinox than at the other. The asymmetry is hemisphere-dependent with the higher electron density occurring at the March equinox in the Northern Hemisphere and at the September equinox in the Southern Hemisphere. The asymmetry becomes stronger with increasing latitude in both hemispheres. The behaviour of the asymmetry has no significant longitudinal and magnetic activity variations. A mechanism for the equinoctial asymmetry has been investigated using CTIP (coupled thermosphere ionosphere plasmasphere model). The model results reproduce the observed equinoctial asymmetry and suggest that the asymmetry is caused by the north-south imbalance of the thermosphere and ionosphere at the equinoxes due to the slow response of the thermosphere arising from the effects of the global thermospheric circulation. The observations also show that the relationship between the electron density and electron temperature is different for daytime and nighttime. During daytime the yearly variation of the electron temperature has negative correlation with the electron density, except at magnetic latitudes lower than 10°. At night, the correlation is positive.Key words: Ionosphere (equatorial ionosphere; ionosphere-atmosphere interactions; plasma temperature and density)

scholarly journals F-region electron density and <i>T<sub>e</sub> / T<sub>i</sub></i> measurements using incoherent scatter power data collected at ALTAIR

2006 ◽  
Vol 24 (5) ◽  
pp. 1333-1342 ◽  
Author(s):  
M. Milla ◽  
E. Kudeki
Keyword(s):  
Electron Density ◽  
Topside Ionosphere ◽  
Low Latitude ◽  
Aspect Angle ◽  
Incoherent Scatter ◽  
F Region ◽  
Regularized Inversion ◽  
The Pacific ◽  
Resolution Electron ◽  
Low Latitude Ionosphere

Abstract. The ALTAIR UHF radar was used in an incoherent scatter experiment to observe the low-latitude ionosphere during the Equis 2 rocket campaign. The measurements provided the first high-resolution electron density maps of the low-latitude D- and E-region in the Pacific sector and also extended into the F-region and topside ionosphere. Although the sampling frequency was well below the Nyquist frequency of F-region returns, we were able to estimate Te / Ti ratio and infer unbiased electron density estimates using a regularized inversion technique described here. The technique exploits magnetic aspect angle dependence of ISR cross-section for Te>Ti.

Topside observation of electron density variations (G-condition) at times of low magnetic activity

1969 ◽  
Vol 47 (23) ◽  
pp. 2683-2689 ◽  
Author(s):  
L. Herzberg ◽  
G. L. Nelms ◽  
P. L. Dyson
Keyword(s):  
Electron Temperature ◽  
Observational Data ◽  
Electron Density ◽  
Path Length ◽  
Gradual Increase ◽  
Magnetic Activity ◽  
Scale Height ◽  
Magnetic Disturbance

The so-called G-condition of the ionosphere (foF2 < foF1, with normal foF1) is investigated from the topside with the Alouette II satellite. In the absence of a severe magnetic disturbance, the condition is occasionally observed over a path length of the order of a thousand kilometers. In this case, one observes a characteristic development: in the F2 region at the levels below about 1000 km there is a systematic decrease of electron density to about one-half the original value, followed by a gradual increase to normal, and at the levels above about 1000 km there is a corresponding increase, followed by a decrease back to normal. This variation in electron density is accompanied, at levels below 2000 km, by significant increases in scale height. Cylindrical electrostatic probes carried on the satellite show, at the same time, increases in electron temperature. Possible interpretations of the observational data are discussed.

scholarly journals On the mechanism of the post-midnight winter <i>N<sub>m</sub>F<sub>2</sub></i> enhancements: dependence on solar activity

2000 ◽  
Vol 18 (11) ◽  
pp. 1422-1434 ◽  
Author(s):  
A. V. Mikhailov ◽  
M. Förster ◽  
T. Y. Leschinskaya
Keyword(s):  
Solar Activity ◽  
Electron Temperature ◽  
Electron Density ◽  
Opposite Sign ◽  
Plasma Temperature ◽  
Ionosphere Plasma ◽  
Recombination Efficiency ◽  
Thermospheric Winds ◽  
Flux Increase ◽  
Different Levels

Abstract. The mechanism of the NmF2 peak formation at different levels of solar activity is analyzed using Millstone Hill IS radar observations. The hmF2 nighttime increase due to thermospheric winds and the downward plasmaspheric fluxes are the key processes responsible for the NmF2 peak formation. The electron temperature follows with the opposite sign the electron density variations in this process. This mechanism provides a consistency with the Millstone Hill observations on the set of main parameters. The observed decrease of the nighttime NmF2 peak amplitude with solar activity is due to faster increasing of the recombination efficiency compared to the plasmaspheric flux increase. The E×B plasma drifts are shown to be inefficient for the NmF2 nighttime peak formation at high solar activity.Key words: Ionosphere (ionosphere-atmosphere interactions; mid-latitude ionosphere; plasma temperature and density)

scholarly journals Equinoctial Asymmetry in Solar Quiet Fields along the 120° E Meridian Chain

2021 ◽  
Vol 11 (19) ◽  
pp. 9150
Author(s):  
Yingyan Wu ◽  
Libo Liu ◽  
Zhipeng Ren
Keyword(s):  
Field Measurements ◽  
Low Latitude ◽  
Positive Dependence ◽  
Latitude Distribution ◽  
Regional Factors ◽  
The Asymmetry ◽  
The Relationship ◽  
Quiet Day ◽  
Possible Cause ◽  
Dynamo Process

Equinoctial asymmetry of the range of the solar quiet day variation (Sq) of the horizontal geomagnetic field (H) has been found in some low latitude geomagnetic observatories. This study conducted an investigation of its latitude distribution and the relationship with the solar cycle by using the H field measurements from six observatories along the 120° E meridian chain in the years 1957–2013. Results illustrate a significant equinoctial asymmetry of the SqH range at all observatories. Three main features were identified. First, the signature of the equinoctial asymmetry of the SqH range is opposite for observatories located at the northern and southern sides of the Northern Hemisphere Sq current focus. It shows larger values around spring than autumn equinox at southern observatories, and the converse is seen at northern observatories. Second, the asymmetry increases with the distance from the Sq current focus, suggesting the stronger sensitivity of the distant observatories than observatories around the focus. The result of linear fitting presents a positive dependence of the asymmetry coefficient on geographic latitude, with a reversal of the asymmetry occurring at 28.1° N near the focus of the average Sq current. Third, there is no obvious dependence of the equinoctial asymmetry of the SqH range on solar activity, suggesting a possible cause from some regional factors related to the ionospheric dynamo process.

Rola Avarského Kaganátu Pri Vzniku Slovenčiny

2018 ◽  
Vol 69 (2) ◽  
pp. 199-236
Author(s):  
Martin Braxatoris ◽  
Michal Ondrejčík
Keyword(s):  
Slavic Language ◽  
The West ◽  
The North ◽  
Danube Region ◽  
The Absolute ◽  
North Edge ◽  
The Relationship ◽  
Slovak Language

Abstract The paper proposes a basis of theory with the aim of clarifying the casual nature of the relationship between the West Slavic and non-West Slavic Proto-Slavic base of the Slovak language. The paper links the absolute chronology of the Proto-Slavic language changes to historical and archaeological information about Slavs and Avars. The theory connects the ancient West Slavic core of the Proto-Slavic base of the Slovak language with Sclaveni, and non-West Slavic core with Antes, which are connected to the later population in the middle Danube region. It presumes emergence and further expansion of the Slavic koiné, originally based on the non-West Slavic dialects, with subsequent influence on language of the western Slavic tribes settled in the north edge of the Avar Khaganate. The paper also contains a periodization of particular language changes related to the situation in the Khaganate of that time.

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