Upper thermosphere winds and temperatures in the geomagnetic polar cap: Solar cycle, geomagnetic activity, and interplanetary magnetic field dependencies

Killeen, T. L.; Won, Young-Shin; Niciejewski, R. J.; Burns, A. G.

doi:10.1029/95ja01208

Cited by 99 publications

(108 citation statements)

References 66 publications

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“…It shows the strong dependence of the thermospheric wind at F-region heights (∼400 km) on the IMF conditions. These patterns confirm previous findings based on early satellite data in the 1980s (e.g., Killeen and Roble, 1988;Killeen et al, 1995), but can now rest upon a much broader statistical base due to the good coverage of the CHAMP data. This allowed for the first time a systematic analysis of the solar wind and IMF dependences with respect to the thermospheric vorticity pattern at high geomagnetic latitudes.…”

Section: Discussionsupporting

confidence: 80%

“…It has long been known that the high-latitude thermospheric wind is governed by solar wind conditions, in particular by direction and strength of the IMF (Rees and Fuller-Rowell, 1989;Killeen et al, 1995). It is generally accepted that this coupling occurs by means of ion drag between ionospheric ions set in motion by solar wind induced magnetospheric convection and thermospheric neutrals.…”

Section: Introductionmentioning

confidence: 99%

“…The comprehensive CHAMP data set and the novel methodology of its data analysis as elaborated in Sect. 2 allow detailed studies of the high-latitude thermospheric wind behaviour at Fregion height like those of the DE-2 mission about two solar cycles earlier (Killeen and Roble, 1988;Killeen et al, 1995;Thayer and Killeen, 1991). The novelty of our study, based on well-founded statistics, consists in the first systematic analysis of the thermospheric vorticity in polar regions of both hemispheres in dependence on the IMF orientation, which is presented in Sect.…”

Section: Introductionmentioning

confidence: 99%

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Thermospheric vorticity at high geomagnetic latitudes from CHAMP data and its IMF dependence

Förster

Haaland

Doornbos³

2011

Ann. Geophys.

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Abstract. Neutral thermospheric wind pattern at high latitudes obtained from cross-track acceleration measurements of the CHAMP satellite above both polar regions are used to deduce statistical neutral wind vorticity distributions and were analyzed in their dependence on the Interplanetary Magnetic Field (IMF). The average pattern confirms the large duskside anticyclonic vortex seen in the average wind pattern and reveals a cyclonic vorticity on the dawnside, which is almost equal in magnitude to the duskside minimum. The outer shape of the vorticity pattern agrees approximately with the outer boundary of region-1 currents in the well-known average current distributions of Iijima and Potemra (1976). The IMF dependence of the vorticity pattern resembles the characteristic FAC and ionospheric plasma drift pattern known from various statistical studies obtained under the same sorting conditions.

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Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermospheric vorticity at high geomagnetic latitudes from CHAMP data and its IMF dependence

Förster

Haaland

Doornbos³

2011

Ann. Geophys.

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“…One important result was presented by Killeen et al (1995). They showed thermospheric temperature variations at the F region height in the winter polar cap region during the solar minimum and maximum periods from Fabry-Perot interferometer measurements.…”

Section: Introductionmentioning

confidence: 96%

Polar cap ionosphere and thermosphere during the solar minimum period: EISCAT Svalbard radar observations and GCM simulations

et al. 2012

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The IPY long-run data were obtained from the European Incoherent Scatter Svalbard radar (ESR) observations during March 2007 and February 2008. Since the solar and geomagnetic activities were quite low during the period, this data set is extremely helpful for describing the basic states (ground states) of the thermosphere and ionosphere in the polar cap region. The monthly-averaged ion temperatures for 12 months show similar local time (or UT) variations to each other. The ion temperatures also show significant seasonal variations. The amplitudes of the local time and seasonal variations observed are much larger than the ones predicted by the IRI-2007 model. In addition, we performed numerical simulations with a general circulation model (GCM), which covers all the atmospheric regions, to investigate variations of the neutrals in the polar thermosphere. The GCM simulations show significant variations of the neutral temperature in the polar region in comparison with the NRLMSISE-00 empirical model. These results indicate that both the ions and neutrals would show larger variations than those described by the empirical models, suggesting significant heat sources in the polar cap region even under solar minimum and geomagnetically quiet conditions.

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“…In practice, the scale height used for such normalization is estimated by means of empirical thermosphere models. Such models tend to underestimate the disturbances in the exospheric temperature in presence of magnetic activity Killeen et al, 1995), by as much as 70% (Lathuillère and Menvielle, 2004) which in turn leads to errors in scale height that can reach 15%, and errors in the normalized densities (over one scale height) of the same order of magnitude. These errors depend on the geomagnetic activity through the model imperfectness, which introduce unknown biases to the normalized densities.…”

Section: Introductionmentioning

confidence: 99%

A new method for studying the thermospheric density variability derived from CHAMP/STAR accelerometer data for magnetically active conditions

Menvielle

Lathuillére

Bruinsma³

et al. 2007

Ann. Geophys.

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Abstract. Thermospheric densities deduced from STAR accelerometer measurements onboard the CHAMP satellite are used to characterize the thermosphere and its response to space weather events. The STAR thermospheric density estimates are analysed using a Singular Value Decomposition (SVD) approach allowing one to decouple large scale spatial and temporal variations from fast and local transients. Because SVD achieves such decomposition by using the reproducibility of orbital variations, it provides more meaningful results than any method based upon data smoothing or filtering.SVD analysis enables us to propose a new thermosphere proxy, based on the projection coefficient of the CHAMP densities on the first singular vector. The large scale spatial variations in the density, mostly related to altitude/latitude variations are captured by the first singular vector; time variations are captured by the associated projection coefficient.The study presented here is focused on time dependent global scale variations in the thermospheric density between 50 N and 50 S geographic latitudes. We show that the time variations in the projection coefficient do in fact represent those in the global density that are associated with magnetic activity as well as with solar EUV radiations. We also show that the NRLMSISE-00 empirical model better accounts for the density forcing by Solar radiations when tuned using Mg II indices. Using the so modified model with an additional geomagnetic parameterization corresponding to quiet geomagnetic situation enables one to define time reference values which are then used to evaluate the impact of geomagnetic activity. The ratio of CHAMP density projection coefficient to the quiet model projection coefficient is a global Correspondence to: M. Menvielle (michel.menvielle@cetp.ipsl.fr) quantity, independent of altitude and latitude, which quantifies the thermospheric density response to auroral energy deposition. It will serve as a proxy of the response of thermospheric density to geomagnetic activity forcing.

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Upper thermosphere winds and temperatures in the geomagnetic polar cap: Solar cycle, geomagnetic activity, and interplanetary magnetic field dependencies

Cited by 99 publications

References 66 publications

Thermospheric vorticity at high geomagnetic latitudes from CHAMP data and its IMF dependence

Thermospheric vorticity at high geomagnetic latitudes from CHAMP data and its IMF dependence

Polar cap ionosphere and thermosphere during the solar minimum period: EISCAT Svalbard radar observations and GCM simulations

A new method for studying the thermospheric density variability derived from CHAMP/STAR accelerometer data for magnetically active conditions

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