Effects of solar variability on thermosphere density from CHAMP accelerometer data

Guo, Jianpeng; Wan, Weixing; Forbes, Jeffrey M.; Sutton, E. K.; Nerem, R. S.; Woods, T. N.; Bruinsma, Sean; Liu, Libo

doi:10.1029/2007ja012409

Cited by 71 publications

(87 citation statements)

References 32 publications

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“…Recent studies show that P 10.7 is a better index to describe the thermospheric and ionospheric variations with solar radiation [Hinteregger et al, 1981;Richards et al, 1994;Liu et al, 2006;Guo et al, 2007;Ma et al, 2009].…”

Section: Discussionmentioning

confidence: 99%

“…Thermospheric mass density can also be obtained from satellite-born accelerometer measurements [Boudon et al, 1979;Falin et al, 1981;Reigber et al, 2002]. Recently, thermospheric mass density data derived from measurements by the accelerometer onboard the Challenging Minisatellite Payload (CHAMP) satellite have been used to study the global distributions of the thermospheric mass density and its changes with geophysical conditions [Bruinsma et al, 2004;Liu et al, 2005Liu et al, , 2007Guo et al, 2007Guo et al, , 2008Forbes et al, 2008;Müller et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

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Variations of the nighttime thermospheric mass density at low and middle latitudes

Wang

et al. 2010

J. Geophys. Res.

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[1] The latitudinal structure of the nighttime thermospheric mass density at 385 km has been investigated using observations made by the accelerometer onboard the CHAMP satellite between 2002 and 2007. The nighttime thermospheric mass density had a clear latitudinal variation. There was a local density peak around the geographic equator and two minima at about ±30°. This nighttime equatorial mass anomaly (NEMA) was opposite to the latitudinal variations of the daytime ionospheric equatorial anomaly and thermospheric mass density anomaly as both have minima at the magnetic dip equator and maxima around ±20°in magnetic latitudes. This anomalous behavior of the nighttime thermospheric mass density had strong local time, seasonal, hemispheric, and solar cycle dependences. The largest crest-to-trough ratio between the peak density at the equator and the minima at the anomaly latitudes (±30°) occurred between 0000 and 0200 local time. The NEMA appeared to be more pronounced during solstice seasons. It was also stronger during solar minimum than during solar maximum. In addition, under the same geophysical conditions, the empirical NRLMSISE-00 model shows similar but much weaker nighttime mass density anomaly features at low and middle latitudes. A highresolution National Center for Atmospheric Research-Thermosphere Ionosphere Mesosphere Energetics Global Circulation Model (TIMEGCM) simulation reproduced most of the observed latitudinal variations of the nighttime mass density as well as the thermospheric midnight temperature maximum (MTM). Model results suggest that superposition of diurnal and semidiurnal migrating tides of modes up to wave number 6 is the likely cause of both the NEMA and MTM phenomena.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variations of the nighttime thermospheric mass density at low and middle latitudes

Wang

et al. 2010

J. Geophys. Res.

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“…If the ρ maximum of an overpass was detected between |60 • | and |80 • | cgm latitude and 08:00 and 16:00 MLT we regard it as an anomaly event. We use P10.7 values with a time lag of 1 day, as recommended by Guo et al (2007). Most density peaks occur during phases of low solar activity (P10.7≤130) with highest occurrence numbers within the interval 95≤P10.7≤105.…”

Section: Discussionmentioning

confidence: 99%

“…The solar flux variation is approximated by the F10.7 and P10.7 indices, which reflect the strength of the EUV radiation. According to Guo et al (2007) a use of multiple solar irradiance indices, in fact a combination of F10.7, S EUV (30-120 nm) and S FUV (120-130 nm) with a time lag of 1 day provides a higher correlation than using exclusively F10.7. Similarly good results can be obtained when applying the P10.7 index from the previous day, which is calculated as: (Richards et al, 1994).…”

Section: Considered Parametersmentioning

confidence: 99%

Climatology of the cusp-related thermospheric mass density anomaly, as derived from CHAMP observations

Rentz

Lühr

2008

Ann. Geophys.

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Abstract. We report on the thermospheric mass density anomaly in the vicinity of the ionospheric cusp. A systematic survey of the anomalies is presented, based on a statistical analysis of 4 years of data (2002)(2003)(2004)(2005) obtained by the accelerometer onboard CHAMP. The anomalies are detected during all years and seasons in both hemispheres but with stronger signatures in the Northern Hemisphere. For the same geophysical conditions, solar flux and geomagnetic activity the anomalies in the north are larger by a factor of about 1.35. Over the course of the survey period the amplitude decreases by more than a factor of 5 while the level of solar flux reduces by a factor of 2. The anomaly strength also depends on the solar wind input. The merging electric field, E merg , is generally enhanced for about an hour before the anomaly detection. There is a quadratic response of the anomaly amplitude to E merg . For geophysical conditions of P10.7<150 and E merg <1 mV/m hardly any events are detected. Their amplitudes are found to be controlled by an additive effect of P10.7 and E merg , where the weight of E merg , in mV/m, is by about 50 times higher than that of the solar flux level. The solar zenith angle and the influence of particle precipitation are found to play a minor role as a controlling parameter of seasonal variation. The well-known annual variation of the thermospheric density with a minimum around June also influences the formation of the cusp anomalies. This leads to a clear hemispheric asymmetry with very weak anomalies in the south during June solstice, which is supposed to be a combined effect of the minimum in annual variation and the seasonal decrease of solar insolation in this region.

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“…Solar irradiance is a driving factor in determining the ion populations of the Earth's upper atmosphere (Solomon & Qian 2005). While Mg II h&k are unlikely to play a significant role in thermospheric photoionization, Mg II irradiance has been shown to be a superior proxy to EUV irradiance over the F10.7 radio index (Guo et al 2007;Lean et al 2009). …”

Section: Introductionmentioning

confidence: 99%

OBSERVED VARIABILITY OF THE SOLAR Mg II h SPECTRAL LINE

Schmit

Bryans

Pontieu

et al. 2015

ApJ

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The Mg II h&k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg II h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the variability of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the observed structure and formation of the Mg II profiles observed by IRIS.

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Effects of solar variability on thermosphere density from CHAMP accelerometer data

Cited by 71 publications

References 32 publications

Variations of the nighttime thermospheric mass density at low and middle latitudes

Variations of the nighttime thermospheric mass density at low and middle latitudes

Climatology of the cusp-related thermospheric mass density anomaly, as derived from CHAMP observations

OBSERVED VARIABILITY OF THE SOLAR Mg II h SPECTRAL LINE

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