Evidence of solar geomagnetic seasonal control of the topside ionosphere

Taylor, H. A.

doi:10.1016/0032-0633(71)90068-7

Cited by 52 publications

(18 citation statements)

References 13 publications

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“…The most striking thing about the data is the longitudinal variation in the He + concentrations. Longitudinal variations in He + have been known since the earliest investigations [ Taylor , 1971]. The variations seen here are consistent with zonal winds blowing from east to west.…”

Section: Discussionsupporting

confidence: 85%

Observations of He⁺ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

West

2009

J. Geophys. Res.

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[1] Average He + concentrations are examined for solar maximum conditions at equinox using data from Defense Meteorological Satellite Program (DMSP) flights F13 and F15. The DMSP spacecraft have Sun-synchronous orbits at 800 km altitude. F13 data were taken under presunrise conditions, while F15 data were taken at midmorning local times. Data are averaged for 31 days centered on the northern spring and fall equinoxes between ±40°m agnetic latitude. Both the He + concentration and He + fraction show significant longitudinal and latitudinal variation, which can be accounted for by neutral wind induced ion drag. The He + fraction can reach as much as 40% of the total plasma density in the presunrise hours, but 10% or less of the total plasma density at midmorning. While the He + concentrations before sunrise and at midmorning have comparable magnitudes, the midmorning values of the He + fraction are much more uniform than in the presunrise data. Examination of the F10.7 cm solar flux and geomagnetic activity implies solar flux has a much greater influence on He + concentrations. The level of solar flux as well as the amount of variability in the solar flux appear to influence the average He + concentrations and fractions.

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Section: Discussionsupporting

confidence: 85%

Observations of He⁺ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

West

2009

J. Geophys. Res.

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“…The importance of considering both geographic and magnetic season in the study of ion composition data has been demonstrated in earlier reports on the Explorer 32 (Brinton et aI., 1969;Brinton et aI., 1970) and OGO 4 Taylor, 1970b) spectrometer measurements.…”

mentioning

confidence: 95%

Altitude variation of ion composition in the midlatitude trough region: Evidence for upward plasma flow

Brinton

Grebowsky²,

Mayr³

1971

J. Geophys. Res.

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Midday ion composition measurements made by the Explorer 32 ion mass spectrometer in the midlatitude trough region (L = 5.0–10.5) are compared with measurements made within the plasmasphere (L = 1.8–2.2). In the trough the light ion (H+ and He+) concentrations are observed to decrease with altitude between 600 and 2500 km, a region in which O+ is the major ion. Within the plasmasphere, however, the concentrations of the light ions, when minor, increase with altitude. Model calculations indicate that the behavior of the plasmasphere profiles is consistent with a state of stationary diffusive equilibrium, whereas a dynamic plasma state is required to account for the trough distributions. Upward‐directed H+ fluxes with near sonic speeds above 2000 km are required to reproduce the measured trough variations. This ‘trough wind,’ consisting of a rapid upward flow of H+, can be interpreted as evidence for the convection of the supersonic polar wind on to closed trough field lines.

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“…Relatively small counts observed by EUVI around the dip equator correspond to the equatorial trough. Some previous studies reported that the equatorial trough of He + is often observed at the dip equator [ Chandra et al , ; Taylor , ; Iwamoto , ; Sidorova , ].…”

Section: Resultsmentioning

confidence: 99%

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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Evidence of solar geomagnetic seasonal control of the topside ionosphere

Cited by 52 publications

References 13 publications

Observations of He⁺ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

Observations of He⁺ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

Altitude variation of ion composition in the midlatitude trough region: Evidence for upward plasma flow

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

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Evidence of solar geomagnetic seasonal control of the topside ionosphere

Cited by 52 publications

References 13 publications

Observations of He+ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

Observations of He+ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

Altitude variation of ion composition in the midlatitude trough region: Evidence for upward plasma flow

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

Contact Info

Product

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Observations of He⁺ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

Observations of He⁺ concentrations in the topside ionosphere under equinox conditions near solar maximum: Morningside morphology

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