Universal time effect in the response of the thermosphere to electric field changes

Perlongo, N. J.; Ridley, A. J.

doi:10.1002/2015ja021636

Cited by 13 publications

(16 citation statements)

References 60 publications

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“…The modeled spatial and temporal variations of air mass density during substorm periods are in general consistent with those derived from CHAMP observations [Clausen et al, 2014]. Several studies have used GITM for ionosphere-thermosphere physical studies, and good agreements were achieved when model outputs were validated with observations and other modeling results [e.g., Pawlowski and Ridley, 2009;Deng et al, 2011;Yigit and Ridley, 2011;Ercha et al, 2012;Zhu and Ridley, 2014;Wang et al, 2015;Liu and Ridley, 2015;Wang and Luehr, 2016;Perlongo and Ridley, 2016].…”

Section: Modelsupporting

confidence: 71%

Universal time variation of high‐latitude thermospheric disturbance wind in response to a substorm

et al. 2017

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The temporal and spatial variation in thermospheric winds are studied at 400 km altitude in response to substorms that start at different universal time (UT), using a global ionosphere and thermosphere model. The substorm‐induced disturbance winds at high latitudes are mainly in the poleward, westward, and upward directions in the dusk sector and in the equatorward, westward, and upward directions in the nighttime. The daytime perturbation is due to ion drag, driven by variations in interplanetary magnetic field Bz, whereas the nighttime perturbation is due to both the Bz and hemispheric power input. The nightside disturbed winds respond somewhat later than the dayside owing to low background ion density. Ion drag is the dominant driving force in the daytime for both meridional and zonal disturbed winds, whereas Joule heating is the dominant factor for the vertical winds. The nighttime meridional and zonal winds are driven by a combination of ion drag, Joule heating, and heating of the auroral belt, whereas the vertical winds are mainly caused by auroral belt heating. The viscous force acts to resist the ion drag, whereas the Coriolis force is negligible. The disturbed winds exhibit large variations with UT during equinox and local winter conditions. With more solar illumination, stronger disturbed winds can be generated. Weak or even opposite variations with UT in the disturbed winds are found in local summer, which is due to a smaller UT variation of the daytime ion density and a larger contribution from auroral heating than from ion drag.

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Section: Modelsupporting

confidence: 71%

Universal time variation of high‐latitude thermospheric disturbance wind in response to a substorm

et al. 2017

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“…For t > 0, density is more strongly enhanced and immediately occurs in MLAT regions above 54° in both hemispheres. The asymmetric interhemispheric response is presumably related to the universal time of the main phase peak of each storm due to asymmetric energy input in high‐latitude regions caused by the offset and tilt of the Earth's dipole field (Perlongo & Ridley, ). The midlatitude response occurs more strongly and faster, with a lag time of 1.5 h, as indicated by the first two vertical blue lines in both hemispheres.…”

Section: Resultsmentioning

confidence: 99%

Thermosphere Global Time Response to Geomagnetic Storms Caused by Coronal Mass Ejections

et al. 2017

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We investigate, for the first time with a spatial superposed epoch analysis study, the thermosphere global time response to 159 geomagnetic storms caused by coronal mass ejections (CMEs) observed in the solar wind at Earth's orbit during the period of September 2001 to September 2011. The thermosphere neutral mass density is obtained from the CHAMP (CHAllenge Mini‐Satellite Payload) and GRACE (Gravity Recovery Climate Experiment) spacecraft. All density measurements are intercalibrated against densities computed by the Jacchia‐Bowman 2008 empirical model under the regime of very low geomagnetic activity. We explore both the effects of the pre‐CME shock impact on the thermosphere and of the storm main phase onset by taking their times of occurrence as zero epoch times (CME impact and interplanetary magnetic field Bz southward turning) for each storm. We find that the shock impact produces quick and transient responses at the two high‐latitude regions with minimal propagation toward lower latitudes. In both cases, thermosphere is heated in very high latitude regions within several minutes. The Bz southward turning of the storm onset has a fast heating manifestation at the two high‐latitude regions, and it takes approximately 3 h for that heating to propagate down to equatorial latitudes and to globalize in the thermosphere. This heating propagation is presumably accomplished, at least in part, with traveling atmospheric disturbances and complex meridional wind structures. Current models use longer lag times in computing thermosphere density dynamics during storms. Our results suggest that the thermosphere response time scales are shorter and should be accordingly adjusted in thermospheric empirical models.

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“…While there were some regions where the auroral Pedersen conductance was stronger than the dayside conductance, the conductance produced by photoionization is generally larger than conductance from the aurora. In addition, because of the summer conditions where the dayside solar EUV dominated the conductance pattern, weaker electric fields and stronger field‐aligned currents would be expected [ Cnossen and Richmond , ; Cnossen and Förster , ], as well as weaker responses to geomagnetic storms [ A et al , ; Perlongo and Ridley , ]. Since all of the storms chosen for this study were during the Northern Hemisphere summer, the amount of electrons making it beyond 06 MLT had little effect on the total Pedersen conductance on the dayside in any of the different simulations.…”

Section: Resultsmentioning

confidence: 99%

The effect of ring current electron scattering rates on magnetosphere‐ionosphere coupling

et al. 2017

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This simulation study investigated the electrodynamic impact of varying descriptions of the diffuse aurora on the magnetosphere‐ionosphere (M‐I) system. Pitch angle diffusion caused by waves in the inner magnetosphere is the primary source term for the diffuse aurora, especially during storm time. The magnetic local time (MLT) and storm‐dependent electrodynamic impacts of the diffuse aurora were analyzed using a comparison between a new self‐consistent version of the Hot Electron Ion Drift Integrator with varying electron scattering rates and real geomagnetic storm events. The results were compared with Dst and hemispheric power indices, as well as auroral electron flux and cross‐track plasma velocity observations. It was found that changing the maximum lifetime of electrons in the ring current by 2–6 h can alter electric fields in the nightside ionosphere by up to 26%. The lifetime also strongly influenced the location of the aurora, but the model generally produced aurora equatorward of observations.

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Universal time effect in the response of the thermosphere to electric field changes

Cited by 13 publications

References 60 publications

Universal time variation of high‐latitude thermospheric disturbance wind in response to a substorm

Universal time variation of high‐latitude thermospheric disturbance wind in response to a substorm

Thermosphere Global Time Response to Geomagnetic Storms Caused by Coronal Mass Ejections

The effect of ring current electron scattering rates on magnetosphere‐ionosphere coupling

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