Interhemispheric observations of emerging polar cap asymmetries

Laundal, K. M.; Østgaard, Nikolai; Snekvik, K.; Frey, H. U.

doi:10.1029/2009ja015160

Cited by 29 publications

(33 citation statements)

References 51 publications

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“…Aurora associated particles change not only the conductivity and Joule heating in the high‐latitude ionosphere but also the ionosphere and thermosphere convection. Moreover, they in turn affect the magnetosphere convection and auroral precipitation through magnetosphere‐ionosphere interactions [ Prölss and Craven , ; Laundal et al , ].…”

Section: Introductionmentioning

confidence: 99%

Solar activity dependence of nightside aurora in winter conditions

2016

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The dependence of the nightside (21:00–03:00 MLT; magnetic local time) auroral energy flux on solar activity was quantitatively studied for winter/dark and geomagnetically quiet conditions. Using data combined from Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager and Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations, we separated the effects of geomagnetic activity from those of solar flux on the nightside auroral precipitation. The results showed that the nightside auroral power was reduced by ~42% in solar maximum (F10.7 = 200 sfu; solar flux unit 1 sfu = 10−22 W m−2 Hz−1) with respect to that under solar minimum (F10.7 = 70 sfu) for the Kp = 1 condition, and this change rate became less (~21%) for the Kp = 3 condition. In addition, the solar cycle dependence of nightside auroral power was similar with that from both the premidnight (21:00–23:00 MLT) and postmidnight (01:00–03:00 MLT) sectors. These results indicated that as the ionospheric ionization increases with the enhanced auroral and geomagnetic activities, the solar activity dependences of nightside auroral power become weaker, at least under geomagnetically quiet conditions.

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Section: Introductionmentioning

confidence: 99%

Solar activity dependence of nightside aurora in winter conditions

2016

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“…We use the poleward boundary of the aurora as a proxy for 5 the open-closed boundary (OCB) (Laundal et al, 2010) plasma, according to the derived convection pattern, flows across the OCB. We can identify dayside reconnection between 11 MLT and 15 MLT that opens magnetic flux and tail reconnection between 18 MLT and 22 MLT that closes magnetic flux.…”

Section: Convection Pattern In the Northern Hemispherementioning

confidence: 99%

The asymmetric geospace as displayed during the geomagnetic storm on August 17, 2001

Østgaard¹,

Reistad²,

Tenfjord³

et al. 2018

Preprint

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“…Because the response of the SI12 camera depends on the proton energy, a decrease in the proton energy could reduce the emission below the observable level [ Frey et al , 2003b]. Note that it is also possible that there are significant differences between the auroral emissions in the Northern and Southern hemispheres at the foot of the field line that maps to the magnetopause [ Laundal et al , 2010]. The fact that the event occurred near the fall equinox makes this less likely since illumination would be comparable for the two polar caps.…”

Section: Discussionmentioning

confidence: 99%

Observations of a high-latitude stable electron auroral emission at ∼16 MLT during a large substorm

et al. 2011

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[1] During an interval when the interplanetary magnetic field was large and primarily duskward and southward, a stable region of auroral emission was observed on 17 August 2001 by IMAGE at ∼16 magnetic local time, poleward of the main aurora, for 1 h, from before the onset of a large substorm through the recovery phase. In a region where ions showed the energy dispersion expected for the cusp, strong field-aligned currents and Poynting flux were observed by Polar (at 1.8 R E in the Southern Hemisphere) as it transited field lines mapping to the auroral spot in the Northern Hemisphere. The data are consistent with the hypothesis that the long-lasting electron auroral spot maps to the magnetopause region where reconnection was occurring. Under the assumption of conjugacy between the Northern and Southern hemispheres on these field lines, the Polar data suggest that the electrons on these field lines were accelerated by Alfvén waves and/or a quasi-static electric field, primarily at altitudes below a few R E since the in situ Poynting flux (mapped to 100 km) is comparable to the energy flux of the emission while the mapped in situ electron energy flux is much smaller. This event provides the first example of an emission due to electrons accelerated at low altitudes at the foot point of a region of quasi-steady dayside reconnection. Cluster data in the magnetotail indicate that the Poynting flux from the reconnection region during this substorm is large enough to account for the observed nightside aurora.

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Interhemispheric observations of emerging polar cap asymmetries

Cited by 29 publications

References 51 publications

Solar activity dependence of nightside aurora in winter conditions

Solar activity dependence of nightside aurora in winter conditions

The asymmetric geospace as displayed during the geomagnetic storm on August 17, 2001

Observations of a high-latitude stable electron auroral emission at ∼16 MLT during a large substorm

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