Predicting storm-time thermospheric mass density variations at CHAMP and GRACE altitudes

Liu, R.; Ma, Shuang‐Gang; Lühr, H.

doi:10.5194/angeo-29-443-2011

Cited by 25 publications

(23 citation statements)

References 33 publications

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“…They suggest that the time delay can be further reduced at higher altitude and on the nightside. Previous studies showed that the thermosphere reaction during magnetic storms could be much faster, simultaneously or within 30 min (e.g Liu et al, 2011). Based on these results, we might use the location of the peak westward zonal wind deduced from CHAMP measurements to refer to the SAPS location in each MLT bin.…”

Section: Discussionmentioning

confidence: 99%

The spatial distribution of region 2 field-aligned currents relative to subauroral polarization stream

et al. 2014

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Abstract. To test the current-generation model of subauroral polarization stream (SAPS), we have investigated the relative positions of field-aligned currents (FACs) with respect to SAPS in a statistical way by using CHAMP (CHAllenging Minisatellite Payload) and DMSP (Defense Meteorological Satellite Program) satellite observations as well as model simulations. Comparative studies have been performed for consecutive CHAMP observations in different magnetic local time (MLT) sectors with respect to SAPS. The latitude of the peak westward zonal wind deduced from CHAMP measurements has been used to represent the location of the SAPS peak. Both the density and the sheet current strength of R2 (region 2) FACs are enhanced when SAPS occur. Subsequently R2 FACs decay in intensity and correspondingly the centers retreat poleward. The latitudes of the center of the R2 FAC, small-and medium-scale FACs, and SAPS shift equatorward with increasing MLT. The SAPS peaks are located between R2 and R1 (region 1) FAC peaks in all MLT bins under study. The SAPS peaks are closer to R2 centers in the later MLT sectors. The peaks of small-and mediumscale FACs are located poleward of SAPS, mainly in the upward R1 FACs region. The upward R1 FACs are partly closed by the downward R1 FACs in the dawn-morning sector. Based on model simulation, when R2 shifts equatorward to the subauroral region, the plasma flow also shifts equatorward with its peak located poleward of that of R2 FACs. Both the model and observations provide evidence that SAPS behave as caused by a magnetospheric current source.

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Section: Discussionmentioning

confidence: 99%

The spatial distribution of region 2 field-aligned currents relative to subauroral polarization stream

et al. 2014

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“…However, the study of the neutral mass component was often limited or not taken into account because of a lack of suitable in situ measurements. Since, 2000 with the launch of the CHAMP (CHAllenging Minisatellite Payload) and later the GRACE (Gravity Recovery And Climate Experiment) satellites it became possible to study thermospheric density in detail (Lühr et al, 2004;Liu et al, 2005;Schlegel et al, 2005;Bruinsma et al, 2006;Liu et al, 2011). Unfortunately, GRACE (Tapley et al, 2004) does not provide electrodynamic quantities, e.g.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

The relationship of thermospheric density anomaly with electron temperature, small-scale FAC, and ion up-flow in the cusp region, as observed by CHAMP and DMSP satellites

Kervalishvili

Lühr

2013

Ann. Geophys.

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Abstract. We present in a statistical study a comparison of thermospheric mass density enhancements (ρrel) with electron temperature (Te), small-scale field-aligned currents (SSFACs), and vertical ion velocity (Vz) at high latitudes around noon magnetic local time (MLT). Satellite data from CHAMP (CHAllenging Minisatellite Payload) and DMSP (Defense Meteorological Satellite Program) sampling the Northern Hemisphere during the years 2002–2005 are used. In a first step we investigate the distribution of the measured quantities in a magnetic latitude (MLat) versus MLT frame. All considered variables exhibit prominent peak amplitudes in the cusp region. A superposed epoch analysis was performed to examine causal relationship between the quantities. The occurrence of a thermospheric relative mass density anomaly, ρrel >1.2, in the cusp region is defining an event. The location of the density peak is taken as a reference latitude (Δ MLat = 0°). Interestingly, all the considered quantities, SSFACs, Te, and Vz are co-located with the density anomaly. The amplitudes of the peaks exhibit different characters of seasonal variation. The average relative density enhancement of the more prominent density peaks considered in this study amounts to 1.33 during all seasons. As expected, SSFACs are largest in summer with average amplitudes equal to 2.56 μA m−2, decaying to 2.00 μA m−2 in winter. The event related enhancements of Te and Vz are both largest in winter (Δ Te =730 K, Vz =136 m s−1) and smallest in summer (Δ Te = 377 K, Vz = 57 m s−1. Based on the similarity of the seasonal behaviour we suggest a close relationship between these two quantities. A correlation analysis supports a linear relation with a high coefficient greater than or equal to 0.93, irrespective of season. Our preferred explanation is that dayside reconnection fuels Joule heating of the thermosphere causing air upwelling and at the same time heating of the electron gas that pulls up ions along affected flux tubes.

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“…As with the response of neutral density to flares, the characteristics of an individual geomagnetic storm, such as the orientation, strength, and variability of the interplanetary magnetic field, and the solar wind speed and density, affect the magnitude, temporal, and spatial features of the resulting density changes (e.g., Liu et al 2010Liu et al , 2011. The level of solar activity, season, and UT at storm onset also has a significant effect (Burns et al 2004), due largely to variations in ionospheric conductivity.…”

Section: Response To Geomagnetic Stormsmentioning

confidence: 99%

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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Predicting storm-time thermospheric mass density variations at CHAMP and GRACE altitudes

Cited by 25 publications

References 33 publications

The spatial distribution of region 2 field-aligned currents relative to subauroral polarization stream

The spatial distribution of region 2 field-aligned currents relative to subauroral polarization stream

The relationship of thermospheric density anomaly with electron temperature, small-scale FAC, and ion up-flow in the cusp region, as observed by CHAMP and DMSP satellites

Thermospheric Density: An Overview of Temporal and Spatial Variations

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