The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations

Wang, Hui; Lühr, H.; Y., Shu

doi:10.1029/2011ja017378

Cited by 28 publications

(48 citation statements)

References 58 publications

(72 reference statements)

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“…The elevated neutral temperature will increase the pressure gradient at high latitudes and further produces an enhanced equatorward meridional wind, which turns westward at middle and low latitudes under the Coriolis force. Observational evidence for that has also been provided by Wang et al []. They confirmed that both SAPS and westward zonal wind peak at almost the same latitude.…”

Section: Discussionsupporting

confidence: 72%

Global features of the disturbance winds during storm time deduced from CHAMP observations

2015

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A wind‐driven disturbance dynamo has been postulated many decades ago. But due to the sparseness of thermospheric wind measurements, details of the phenomena could not be investigated. In this study we use the CHAMP zonal wind observations from 2001 to 2005 to investigate the global features of the disturbance winds during magnetically disturbed periods. The disturbance zonal wind is mainly westward, which increases with magnetic activity and latitude. At subauroral region, the westward zonal wind is strongly enhanced in the magnetic local time (MLT) sector from afternoon to midnight, which we relate to the plasma drift within the subauroral polarization streams. At middle and low latitudes, the disturbance zonal wind is largely independent of season. Peak values of the disturbance zonal wind occur at different MLTs for different latitudes. That is around 1800 MLT at subauroal region, with average values of about 200 m/s; around 2300 MLT at middle latitudes, with average values of about 80 m/s; and around 0300 MLT at low latitudes, with average values up to 50 m/s. The shift of the peak values of the westward disturbance zonal wind in local time at different latitudes could be considered as a response of the disturbance wind when it propagates from high to low latitudes. Further by applying for the first time a superposed epoch analysis, we show that the disturbance zonal wind responds with a delay to the sudden changes of solar wind input, which is different for the various latitudinal ranges. The propagation time of disturbance wind from the auroral region to the equator is about 3–4 h. This is consistent with the speed of traveling atmospheric disturbances. Based on CHAMP observations, we try to illustrate the whole chain of processes from the solar wind driving to the ionospheric effects at lower latitudes.

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Section: Discussionsupporting

confidence: 72%

Global features of the disturbance winds during storm time deduced from CHAMP observations

2015

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“…But the plasma velocity is much higher than that of the wind (e.g. Wang et al, 2012). Ion friction may thus be a relevant heating source.…”

Section: Zonal Wind Dependence On Imf B Y Signmentioning

confidence: 99%

Climatology of zonal wind and large-scale FAC with respect to the density anomaly in the cusp region: seasonal, solar cycle, and IMF By dependence

Kervalishvili

Lühr

2014

Ann. Geophys.

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Abstract. We investigate the relationship of the thermospheric density anomaly (ρ rel ) with the neutral zonal wind velocity (U zonal ), large-scale field-aligned current (FAC), small-scale FAC, and electron temperature (T e ) using the superposed epoch analysis (SEA) method in the cusp region. The dependence of these variables on the sign of the interplanetary magnetic field (IMF) B y component and local season is of particular interest. Also, the conditions that lead to larger relative density enhancements are investigated. Our results are based on CHAMP satellite data and OMNI online data of IMF for solar maximum (March 2002-March 2007 and minimum (March 2004-March 2009 conditions in the Northern Hemisphere. In the cusp region the SEA technique uses the time and location of the mass density anomaly peaks as reference parameters. On average, the amplitude of the relative density anomaly, ρ rel , does not depend on the solar cycle phase, local season, and IMF B y sign. Also, it is apparent that the amplitude of IMF B y does not have a large influence on ρ rel , while the negative IMF B z amplitude prevailing about half an hour earlier is in good correlation with ρ rel . Both the zonal wind velocity and the large-scale FAC (LSFAC) distribution exhibit a clear dependence on the IMF B y sign. U zonal is directed towards dawn for both positive and negative IMF B y at all local seasons and for solar maximum and minimum conditions. There is a systematic imbalance between downward (upward) and upward (downward) large-scale FACs peaks equatorward and poleward of the reference point, respectively, for the IMF B + y (B − y ) case. Relative density enhancements appear halfway between region 1 and region 0 currents in closer proximity to the upward FAC region. FAC densities and mass density anomaly amplitudes are not well correlated, but it is apparent that there is a close spatial relationship between ρ rel and LSFAC. At this point we cannot offer any simple functional relation between these two variables, because there seem to be additional quantities controlling this relation.

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“…During quiet times, zonal winds at middle and low latitudes are generally directed eastward from afternoon to early morning and westward for the other local times. The westward disturbance wind, which is partly related to the subauroral polarization streams (SAPS), is strongly enhanced from the afternoon to midnight sector, increasing with magnetic activity level (Wang et al, ). It is worthwhile to note that the CHAMP data in the paper of Xiong et al () do not represent winds well in the polar cap region.…”

Section: Introductionmentioning

confidence: 99%

“…The thermospheric convection response to ionospheric current systems was earlier investigated (e.g., Emmert et al, ; Förster et al, ; Lühr et al, ; Wang et al, ). The thermospheric vorticity was found to be closely related to the corresponding field‐aligned current (FAC) pattern (Förster et al, ).…”

Section: Introductionmentioning

confidence: 99%

The Relationship of High‐Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

et al. 2017

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The relationship between high‐latitude ionospheric currents (Hall current and field‐aligned current) and thermospheric wind is investigated. The 2‐D patterns of horizontal wind and equivalent current in the Northern Hemisphere derived from the CHAMP satellite are considered for the first time simultaneously. The equivalent currents show strong dependences on both interplanetary magnetic field (IMF) By and Bz components. However, IMF By orientation is more important in controlling the wind velocity patterns. The duskside wind vortex as well as the antisunward wind in the morning polar cap is more evident for positive By. To better understand their spatial relation in different sectors, a systematic superposed epoch analysis is applied. Our results show that in the dusk sector, the vectors of the zonal wind and equivalent current are anticorrelated, and both of them form a vortical flow pattern for different activity levels. The currents and zonal wind are intensified with the increase of merging electric field. However, on the dawnside, where the relation is less clear, antisunward zonal winds dominate. Plasma drift seems to play a less important role for the wind than neutral forces in this sector. In the noon sector, the best anticorrelation between equivalent current and wind is observed for a positive IMF By component and it is less obvious for negative By. A clear seasonal effect with current intensities increasing from winter to summer is observed in the noon sector. Different from the currents, the zonal wind intensity shows little dependence on seasons. Our results indicate that the plasma drift and the neutral forces are of comparable influence on the zonal wind at CHAMP altitude in the noon sector.

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The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations

Cited by 28 publications

References 58 publications

Global features of the disturbance winds during storm time deduced from CHAMP observations

Global features of the disturbance winds during storm time deduced from CHAMP observations

Climatology of zonal wind and large-scale FAC with respect to the density anomaly in the cusp region: seasonal, solar cycle, and IMF <i>B</i><sub><i>y</i></sub> dependence

The Relationship of High‐Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

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The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations

Cited by 28 publications

References 58 publications

Global features of the disturbance winds during storm time deduced from CHAMP observations

Global features of the disturbance winds during storm time deduced from CHAMP observations

Climatology of zonal wind and large-scale FAC with respect to the density anomaly in the cusp region: seasonal, solar cycle, and IMF &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;&lt;i&gt;y&lt;/i&gt;&lt;/sub&gt; dependence

The Relationship of High‐Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

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Climatology of zonal wind and large-scale FAC with respect to the density anomaly in the cusp region: seasonal, solar cycle, and IMF <i>B</i><sub><i>y</i></sub> dependence