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

Förster, M.; Haaland, Stein; Doornbos, Eelco

doi:10.5194/angeo-29-181-2011

Cited by 39 publications

(74 citation statements)

References 32 publications

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“…Such a pattern corresponds to

B_{y}^{IMF} -

and

B_{z}^{IMF} -

(sector 5) neutral wind circulations at high latitudes [cf. Förster et al , ].…”

Section: Model Resultsmentioning

confidence: 99%

“…The guiding idea of this study is to analyze statistically the model simulation results of neutral thermospheric wind and ionospheric plasma drift at high latitudes in the same manner as it was done with the observational data of the CHAMP accelerometer wind estimations [ Förster et al , ; Förster et al , ] and the Cluster/Electron Drift Instrument (EDI) drift measurements [ Haaland et al , ; Förster et al , ]. We compare the two different model simulations with each other and consider their principal behavior in the context of observational findings.…”

Section: Methodsmentioning

confidence: 99%

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Upper atmosphere differences between northern and southern high latitudes: The role of magnetic field asymmetry

Förster

Cnossen

2013

JGR Space Physics

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[1] The nondipolar portions of the Earth's main magnetic field constitute substantial differences between the two hemispheres. Beside the magnetic flux densities and patterns being different in the Northern Hemisphere (NH) and Southern Hemisphere (SH), also the offset between the invariant magnetic and the geographic poles is larger in the SH than in the NH. We investigated the effects of this magnetic field asymmetry on the high-latitude thermosphere and ionosphere using global numerical simulations and compared our results with recent observations. While the effects on the high-latitude plasma convection are small, the consequences for the neutral wind circulation are substantial. The cross-polar neutral wind and ion drift velocities are generally larger in the NH than the SH, and the hemispheric difference shows a semidiurnal variation. The neutral wind vorticity is likewise larger in the NH than in the SH, with the difference probably becoming larger for higher solar activity. In contrast, the spatial variance of the neutral wind is considerably larger in the SH polar region, with the hemispheric difference showing a strong semidiurnal variation. Its phase is similar to the phase of the semidiurnal variation of the hemispheric magnitude differences. Hemispheric differences in ion drift and neutral wind magnitude are most likely caused partly by the larger magnetic flux densities in the near-polar regions of the SH and partly by the larger offset between the invariant and geographic pole in the SH, while differences in spatial variance are probably just caused by the latter. We conclude that the asymmetry of the magnetic field, both in strength and in orientation, establishes substantial hemispheric differences in the neutral wind and plasma drift in the high-latitude upper atmosphere, which can help to explain observed hemispheric differences found with the Cluster/Electron Drift Instrument (EDI) and the Challenging Minisatellite Payload (CHAMP).Citation: Förster, M., and I. Cnossen (2013), Upper atmosphere differences between northern and southern high latitudes: The role of magnetic field asymmetry,

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“…Such a pattern corresponds to

B_{y}^{IMF} -

and

B_{z}^{IMF} -

(sector 5) neutral wind circulations at high latitudes [cf. Förster et al , ].…”

Section: Model Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Upper atmosphere differences between northern and southern high latitudes: The role of magnetic field asymmetry

Förster

Cnossen

2013

JGR Space Physics

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“…In recent years, it has been found that the amplitude and direction of the IMF B y component, which plays an important role in the development of ionospheric storms, may be one of the factors that impacts the hemispheric asymmetry [Crowley et al, 2010;Förster et al, 2011;Mannucci et al, 2014;Astafyeva et al, 2015]. In recent years, it has been found that the amplitude and direction of the IMF B y component, which plays an important role in the development of ionospheric storms, may be one of the factors that impacts the hemispheric asymmetry [Crowley et al, 2010;Förster et al, 2011;Mannucci et al, 2014;Astafyeva et al, 2015].…”

Section: Discussionmentioning

confidence: 99%

Analysis of the global ionospheric disturbances of the March 2015 great storm

et al. 2016

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The global ionospheric storm in March 2015 was investigated by using data from over 3000 GPS stations worldwide. In this study, total electron content (TEC), rate of TEC (ROT), and ROT's standard deviation rate of the TEC index, as well as the second‐order difference operator TECT, were considered as main characteristic methods to distinguish ionosphereic disturbances. The results show that (1) based on the multiple methods above, we all observed that for the first time, there were three equatorward traveling ionospheric disturbances (TIDs) in the main phase of this storm. In North America, the disturbance zone expanded to ~40°N; the disturbance periods and AE peak stages were roughly synchronous. We suggest that these three TIDs were induced by the propagation of atmospheric gravity waves to low latitudes under the action of AE. (2) The most intense positive storm occurred over South America and the South Atlantic (over 300% enhancement; 00:00–05:00 UT on 18 March), whereas a negative storm was observed in the corresponding region of the Northern Hemisphere. Such inverse hemispheric asymmetry in intensity and structure can be explained by the variations of the thermospheric composition, the IMF By component, and the geomagnetic intensity. (3) On 18 March, a negative storm dominated globally (except at certain low latitudes), and tended to propagate equatorward and decay with time, which could be largely attributed to the storm circulation theory. And the evolution of the negative storm was further characterized by the foF2 variations of ionosondes.

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“…Ion drag at F region altitudes can accelerate the neutral wind toward the ion convection velocity. Both plasma drift and neutral wind are found to respond in the similar way to the interplanetary magnetic field (IMF) [e.g., Thayer et al , 1987; Emmert et al , 2006; Förster et al , 2011]. Emmert et al [2006] found that the response of high latitude wind to plasma convection is broadly maximized at a time lag of 1 hour at around 250 km altitude during quiet time.…”

Section: Introductionmentioning

confidence: 99%

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

Wang¹,

Lühr²,

Y.³

2012

J. Geophys. Res.

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The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations [1] We investigate the seasonal variation of the relation between SAPS (subauroral polarization streams) peak ion velocity and zonal wind velocity with coordinated DMSP and CHAMP satellite observations in both hemispheres, separately for Kp < 4 and Kp ≥ 4 geomagnetic conditions. Both SAPS and westward zonal wind peak almost at the same latitude. However, SAPS and zonal wind peak velocities show significantly different seasonal variations. SAPS peak velocities are larger in winter as compared to summer, while zonal wind peak velocities have opposite behavior, larger in summer and smaller in winter, which is valid in both hemispheres and for both geomagnetic activity levels. We reveal, for the first time, that SAPS peak westward ion fluxes, the product of SAPS ion velocity and ion density, exhibit similar seasonal variation as the zonal wind. The results indicate that the effect of SAPS on the zonal wind depends strongly on local ion densities. A linear relationship between SAPS ion fluxes and zonal wind is derived for both hemispheres, which is practically independent of geomagnetic activity. The scaling factor between ion flux and wind velocity is about the same in both hemispheres. Conversely, the background westward wind velocity (bias value in linear equation) is by about 100 m/s higher in the Northern than in the Southern Hemisphere. We attribute this difference to the effect of the large offset between geographic and magnetic poles in the Southern Hemisphere.Citation: Wang, H., H. Lühr, and S. Y. Ma (2012), The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations,

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

Cited by 39 publications

References 32 publications

Upper atmosphere differences between northern and southern high latitudes: The role of magnetic field asymmetry

Upper atmosphere differences between northern and southern high latitudes: The role of magnetic field asymmetry

Analysis of the global ionospheric disturbances of the March 2015 great storm

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

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