A “tongue” of neutral composition

Burns, A. G.; Wang, Wenbin; Killeen, T. L.; Solomon, Stanley C.

doi:10.1016/j.jastp.2004.04.009

Cited by 19 publications

(31 citation statements)

References 37 publications

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“…Prolss (1982) reported a time lag of about 4 h with respect to AE index at low latitudes. Burns et al (2004) also find from TING model that the high latitudinal thermosphere reacts to the geomagnetic forcing with in 1-3 h. These results clearly show that the time lag depends on the latitude. Volland (1967) was first to try to explain such time delays in upper atmosphere and ionosphere theoretically in a landmark paper in terms of downward propagating heat conduction waves.…”

Section: Introductionsupporting

confidence: 62%

On the response of the exospheric temperature to the auroral heating impulse during geomagnetic disturbances

Bhatnagar

Tan

Ramachandaran

2006

Journal of Atmospheric and Solar-Terrestrial Physics

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Section: Introductionsupporting

confidence: 62%

On the response of the exospheric temperature to the auroral heating impulse during geomagnetic disturbances

Bhatnagar

Tan

Ramachandaran

2006

Journal of Atmospheric and Solar-Terrestrial Physics

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“…These TEC enhancements were the results of enhanced high‐latitude convection patterns that transported plasma from daytime middle latitudes, across the polar cap and into the nighttime auroral region. These corresponded to a well‐known phenomenon at high latitudes: the tongue of ionization, which was significantly enhanced during these storm cases [e.g., Crowley , 1996; Schunk and Sojka , 1996; Burns et al , 2004b].…”

Section: Resultsmentioning

confidence: 71%

Ionospheric response to the initial phase of geomagnetic storms: Common features

et al. 2010

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[1] Ionospheric responses to the initial phases of three geomagnetic storms: 2-5 April 2004, 7-9 November 2004, and 13-16 December 2006, were compared using both groundbased GPS total electron content (TEC) data and coupled magnetosphere ionosphere thermosphere (CMIT) model simulations. The onset times for these storms all occurred at local daytime in the North American sector. This similarity of onset times and other factors resulted in some common features in their ionospheric response. These common features include (1) enhanced TEC (positive response) at low and middle latitudes in the daytime, (2) depleted TEC (negative response) around the geomagnetic equator in the daytime, (3) a north-south asymmetry in the positive response as the northern hemispheric response appeared to be more pronounced, and (4) negative response at high latitudes as the storms progressed. The CMIT model captured most of these features. Analysis of model results showed that storm-time enhancements in the daytime eastward electric field were the primary cause of the observed positive storm effects at low and middle latitudes as well as the negative response around the geomagnetic equator in the daytime. These eastward electric field enhancements were caused by the penetration of high latitude electric fields to low latitudes during southward interplanetary magnetic field (IMF) periods, when IMF B z oscillated between southward and northward direction in the initial, shock phase of the storms. Consequently, the ionosphere was lifted up at low and middle latitudes to heights where recombination was weak allowing the plasma to exist for a long period resulting in higher densities. In addition, the CMIT model showed that high-latitude negative storm responses were related to the enhancements of molecular nitrogen seen in TIMED/Global Ultraviolet Imager observations, whereas the negative storm effects around the geomagnetic equator were not associated with thermospheric composition changes; they were the result of plasma transport processes.

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“…However, they appeared to be stronger in the SAPS case. Plasma transport processes which concentrate plasma flux tubes in the ion convection entrance region around noon at high latitudes are the primary processes leading to these enhancements as well as those inside the polar cap known as tongues of ionization [e.g., Burns et al , 2004]. There are times when the downwelling of atomic oxygen rich air occurs inside the polar cap and around the noon sector at high latitudes (Figure 13a), which can also contribute to the increase of ionospheric electron densities there.…”

Section: Discussionmentioning

confidence: 99%

Thermosphere and ionosphere response to subauroral polarization streams (SAPS): Model simulations

Wang¹,

Talaat²,

Burns³

et al. 2012

J. Geophys. Res.

148

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[1] An empirical model of subauroral polarization streams (SAPS) has been incorporated into the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). This SAPS driven TIEGCM is used to simulate the effect of SAPS on the global thermosphere and ionosphere during a moderate geomagnetically active period between day of year (DOY) 329 and 333 in 2008. Model results show: (1) SAPS caused an increase in global thermospheric temperature which became stronger with time. This neutral temperature increase was more significant in subauroral and auroral regions. Joule heating by the SAPS and the redistribution of this heat by dynamic processes were the primary mechanisms for the simulated global neutral temperature changes. (2) In the SAPS driven TIEGCM, the strong ion drag effect in the subauroral SAPS channel drove large changes in thermospheric winds. Zonal neutral winds had either an extra, separate channel of westward flow in the subauroral region in the afternoon-midnight sector or a broad westward wind jet that merged with the regular duskside auroral westward zonal neutral wind driven by the high latitude convection pattern. The exact latitudinal profile of the zonal winds depended on local time. (3) The response of neutral temperature and wind to SAPS was more significant at higher altitudes and exhibited seasonal/hemispheric asymmetry. (4) The heating to the thermosphere by SAPS also resulted in changes in thermospheric composition with upwelling of molecular rich air in subauroral and auroral regions and downwelling of atomic oxygen rich air at other latitudes. These changes in thermospheric composition contributed to the deeper and more extended ionospheric electron density depletions in subauroral middle latitude regions, as well as electron density increases along the equatorward edge of the SAPS channel in the afternoon sector.

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A “tongue” of neutral composition

Cited by 19 publications

References 37 publications

On the response of the exospheric temperature to the auroral heating impulse during geomagnetic disturbances

On the response of the exospheric temperature to the auroral heating impulse during geomagnetic disturbances

Ionospheric response to the initial phase of geomagnetic storms: Common features

Thermosphere and ionosphere response to subauroral polarization streams (SAPS): Model simulations

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