Solar and magnetospheric forcing of the low latitude thermospheric mass density as observed by CHAMP

Müller, Sevim; Lühr, H.; Rentz, S.

doi:10.5194/angeo-27-2087-2009

Cited by 57 publications

(80 citation statements)

References 23 publications

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“…3.5. Neutral density near June solstice is lower than the December solstice, and this annual asymmetry of neutral density is ∼70% in this simulation which is under solar minimum condition, consistent with various observations (Bowman 2004;Müller et al 2009;). Neutral density also shows asymmetry between the two equinoxes (Fig.…”

Section: Latitudinal Variationsupporting

confidence: 73%

“…In this simulation with constant solar minimum forcing, neutral density near March equinox is higher than the September equinox by ∼14%. This equinoctial asymmetry, with neutral density near March equinox being higher than that near the September equinox, is also observed by the CHAMP (Liu et al 2007b;Müller et al 2009). Furthermore, O number density shows similar annual/semiannual variations compared to the neutral density (Figs.…”

Section: Latitudinal Variationmentioning

confidence: 70%

“…Müller et al (2009) conducted statistical analysis to CHAMP neutral density at low latitude (±30 geographical latitude) and found that the ratio between the density on the dayside (10:30-16:30 LT) and night side (22:30-04:30 LT) is 2 ± 0.1 during geomagnetic quite time, nearly independent of solar activity level and season. Figure 3a shows neutral density from day 270 to day 274 of 2007 observed by CHAMP along CHAMP's ascending orbit (∼13:00LT) and descending orbit (∼01:00LT).…”

Section: Diurnal Variationmentioning

confidence: 99%

“…The peak-to-peak amplitudes of are consistent with the amplitude of Bowman (2004) for solar minimum conditions, but are considerably smaller for solar maximum conditions. Müller et al (2009) examined the annual/semiannul variation of neutral density using CHAMP data. They used data at the low latitude, at fixed local time intervals (10:30-16:30 LT and 22:30-04:30 LT), and under geomagnetic quiet conditions (Ap < 15).…”

Section: Annual/semiannual Variationmentioning

confidence: 99%

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Thermospheric Density: An Overview of Temporal and Spatial Variations

2011

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Neutral density shows complicated temporal and spatial variations driven by external forcing of the thermosphere/ionosphere system, internal dynamics, and thermosphere and ionosphere coupling. Temporal variations include abrupt changes with a time scale of minutes to hours, diurnal variation, multi-day variation, solar-rotational variation, annual/semiannual variation, solar-cycle variation, and long-term trends with a time scale of decades. Spatial variations include latitudinal and longitudinal variations, as well as variation with altitude. Atmospheric drag on satellites varies strongly as a function of thermospheric mass density. Errors in estimating density cause orbit prediction error, and impact satellite operations including accurate catalog maintenance, collision avoidance for manned and unmanned space flight, and re-entry prediction. In this paper, we summarize and discuss these density variations, their magnitudes, and their forcing mechanisms, using neutral density data sets and modeling results. The neutral density data sets include neutral density observed by the accelerometers onboard the Challenging Mini-satellite Payload (CHAMP), neutral density at satellite perigees, and global-mean neutral density derived from thousands of orbiting objects. Modeling results are from the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM), and from the NRLMSISE-00 empirical model.

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Section: Latitudinal Variationsupporting

confidence: 73%

Section: Latitudinal Variationmentioning

confidence: 70%

Section: Diurnal Variationmentioning

confidence: 99%

Section: Annual/semiannual Variationmentioning

confidence: 99%

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Thermospheric Density: An Overview of Temporal and Spatial Variations

2011

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“…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%

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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Altitude variations in the thermosphere mass density response to geomagnetic activity during the recent solar minimum

et al. 2014

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Accelerometer data from coplanar orbits of Challenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites were used to study the complex altitude and latitude variations of the thermosphere mass density response to geomagnetic activity during 1-10 December 2008 near 09 LT. Helium number densities near 500 km altitude were extracted from the CHAMP and GRACE measurements and clearly show the presence of a winter hemisphere helium bulge. This recent extreme solar minimum indicates that wintertime helium concentrations exceed NRLMSISE-00 model estimates by 30%-70% during quiet geomagnetic activity after adjusting F 10.7 input into MSIS. The perturbation in mass density from quiet to active conditions is found to be less enhanced in the winter hemisphere at the higher GRACE altitudes (25%) than at the lower CHAMP altitudes (60%) and is attributed to dynamic behavior in the helium/oxygen transition. The investigation revealed the maximum storm time density perturbation to occur near the He/O transition region with a much weaker maximum near the O/N 2 transition region. The altitude of maximum density perturbation occurs where the perturbation in the weighted pressure scale height is equal and opposite to the perturbation in the weighted mean molecular weight scale height. The altitude structure of density scale height perturbation is significantly influenced by the changes in the molecular weight scale height and can account for 50% of the change in mass density scale height in a region correspondingly close to the He/O transition during the 2008 solar minimum period.

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Solar and magnetospheric forcing of the low latitude thermospheric mass density as observed by CHAMP

Cited by 57 publications

References 23 publications

Thermospheric Density: An Overview of Temporal and Spatial Variations

Thermospheric Density: An Overview of Temporal and Spatial Variations

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

Altitude variations in the thermosphere mass density response to geomagnetic activity during the recent solar minimum

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