Solar activity variations in the composition of the low‐latitude topside ionosphere

West, Keith; Heelis, R. A.; Rich, F. J.

doi:10.1029/96ja03031

Cited by 44 publications

(67 citation statements)

References 12 publications

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“…The abundances of these ions are dominated by transport and chemical processes (e.g. Chandra and Rangaswamy, 1967;West et al, 1997;Zhao et al, 2005). The plasma distribution of the equatorial and midlatitude ionosphere is subject to a number of transport processes involving thermospheric neutral winds, E×B drifts, and field-aligned diffusions (Venkatraman and Heelis, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…This package has been described in many works (e.g. Rich et al, 2003;West et al, 1997). The sum of plasma densities over all species (referred to as the total ion density, or N i ) is measured with the onboard Scintillation Meter at a resolution of 24 Hz.…”

Section: Data Sourcementioning

confidence: 99%

“…Previous studies have shown that electron density in the ionosphere varies with solar activity in a Correspondence to: L. Liu (liul@mail.iggcas.ac.cn) rather complicated way (e.g. Balan et al, 1996;Kane, 2003;Liu et al, 2003;Richards, 2001;Sethi et al, 2002;Su et al, 1999;West et al, 1997). Considerable progress has been achieved in understanding the solar cycle variations of the F layer (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Kane, 2003;Lei et al, 2005;Liu et al, 2006b;Sethi et al, 2002), while limited analyses have been applied to the topside ionosphere (e.g. Rich et al, 2003;Su et al, 1999;West et al, 1997;Zhao et al, 2005). Evidence indicates that ionospheric variations have altitude dependencies (Rich et al, 2003;Su et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

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The dependence of plasma density in the topside ionosphere on the solar activity level

et al. 2007

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Abstract. In this paper, the ten-year (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) total ion density N i measurements from the Defense Meteorological Satellite Program (DMSP) spacecraft in the morning and evening (09:30 and 21:30 LT) sectors have been analyzed to explore the dependence of plasma densities in the topside ionosphere at middle and low latitudes on the solar activity level. Results indicate that there is a strong solar activity dependence of DMSP N i at 848 km altitude, which has latitudinal and seasonal features. The plasma density in the topside ionosphere has an approximately linear dependence on daily F107 and a strongly nonlinear dependence on SEM/SOHO EUV, such that the change rate of N i becomes greater with increasing solar EUV. This is quite different from the dependence of N i near the F-Region peak (NmF2), at which the rate of change of NmF2 decreases with increasing solar EUV. The rate of change of N i at the DMSP altitude is greatest in the latitude range where N i is greatest during high solar activity. We suggest that this greater rate of change (or amplification effect) of N i at the DMSP altitude is mainly a consequence of the solar activity variations of the topside scale height. The changes in the height of the F-Region peak (hmF 2 ) and the density NmF2 play a secondary role.

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Section: Discussionmentioning

confidence: 99%

Section: Data Sourcementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The dependence of plasma density in the topside ionosphere on the solar activity level

et al. 2007

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“…Although the maximal values are not located at the same longitudes in two seasons, the general feature of H + peak at the DMSP altitude is much more symmetrical relative to that at DEMETER altitude. West et al (1997) had studied the composition at topside ionosphere by using DMSP satellite data under high and low solar activities. Their results showed that H + became the main composition at 840 km altitude in lower solar activity levels, and H + latitude distribution remained quite symmetric at all local times.…”

Section: The Spatial Distribution Of H + From Dmsp Satellitementioning

confidence: 99%

The spatial distribution of hydrogen ions at topside ionosphere in local daytime

Shen¹,

Zhang²

2017

Terr. Atmos. Ocean. Sci.

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Using DEMETER and DMSP satellite data, the spatial distribution of hydrogen ion (H + ) in local daytime has been compared and analyzed. At 840 km of DMSP height, the seasonal variations of H + density is basically symmetric, with similar density values near to the magnetic equator at northern hemisphere in December and at southern hemisphere in June. But at DEMETER satellite height, the peak H + density shows obvious enhancement at northern hemisphere in December solstice, while with approximate small values at both hemispheres in June. This spatial distribution feature is totally different with other ions such as O + and He + at the topside ionosphere. And also it influences the transition height in topside ionosphere, with lower transition height over northern hemisphere in December season at 10 -20°N than those at equator and over southern hemisphere in June season. The solstitial asymmetry index (AI) of H + at 670 km altitude gives the significant December season enhancement over northern hemisphere, which is typically reversed with electron density (Ne) and ion density (Ni) with large numbers over southern hemisphere in December season. Finally combining with the distribution of H atoms and neutral wind velocity in upper atmosphere, the forming mechanism and asymmetry feature of peak H + density is discussed. It is illustrated that the upwelling movement at equatorial area and northward neutral wind play important roles in H + peak drift in December season at DEMETER satellite altitude below the transition height where H + is not the main composition in the local daytime in solar minimum years. Keywords:Hydrogen ion, Topside ionosphere, Seasonal asymmetry, DEMETER satellite Citation:Shen, X. and X. Zhang, 2017: The spatial distribution of hydrogen ions at topside ionosphere in local daytime.

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Global distribution of the He⁺ column density observed by Extreme Ultra Violet Imager on the International Space Station

et al. 2017

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The global distribution of He+ in the topside ionosphere was investigated using data of the He+ resonant scattering emission at 30.4 nm obtained by the Extreme Ultra Violet Imager (EUVI) onboard the International Space Station. The optical observation by EUVI from the low‐Earth orbit provides He+ column density data above the altitude of 400 km, presenting a unique opportunity to study the He+ distribution with a different perspective from that of past studies using data from in situ measurements. We analyzed data taken in 2013 and elucidated, for the first time, the seasonal, longitudinal, and latitudinal variations of the He+ column density in the dusk sector. It was found that the He+ column density in the winter hemisphere was about twice that in the summer hemisphere. In the December solstice season, the magnitude of this hemispheric asymmetry was large (small) in the longitudinal sector where the geomagnetic declination is eastward (westward). In the June solstice season, this relationship between the He+ distribution and the geomagnetic declination is reversed. In the equinox seasons, the He+ column densities in the two hemispheres are comparable at most longitudes. The seasonal and longitudinal dependence of the hemispheric asymmetry of the He+ distribution was attributed to the geomagnetic meridional neutral wind in the F region ionosphere. The neutral wind effect on the He+ distribution was examined with an empirical neutral wind model, and it was confirmed that the transport of ions in the topside ionosphere is predominantly affected by the F region neutral wind and the geomagnetic configuration.

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Solar activity variations in the composition of the low‐latitude topside ionosphere

Cited by 44 publications

References 12 publications

The dependence of plasma density in the topside ionosphere on the solar activity level

The dependence of plasma density in the topside ionosphere on the solar activity level

The spatial distribution of hydrogen ions at topside ionosphere in local daytime

Global distribution of the He⁺ column density observed by Extreme Ultra Violet Imager on the International Space Station

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Solar activity variations in the composition of the low‐latitude topside ionosphere

Cited by 44 publications

References 12 publications

The dependence of plasma density in the topside ionosphere on the solar activity level

The dependence of plasma density in the topside ionosphere on the solar activity level

The spatial distribution of hydrogen ions at topside ionosphere in local daytime

Global distribution of the He+ column density observed by Extreme Ultra Violet Imager on the International Space Station

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Global distribution of the He⁺ column density observed by Extreme Ultra Violet Imager on the International Space Station