The role of external triggers in flow shear arcs in the dayside aurora

Sandholt, P. E.; Farrugia, Charles J.

doi:10.5194/angeo-26-2159-2008

Cited by 5 publications

(6 citation statements)

References 40 publications

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“…Also, the statistical result reported here does not discriminate between the two different types of cusp aurorae (two modes of solar wind‐magnetosphere coupling) appearing for northward and southward IMF orientations [ Sandholt et al ., ]. In addition, from the large IMF conditions where the number of the statistical points is less than 10, we note that large flow shears in IMF B y ‐distorted flow patterns tend to enhance the brightness of dayside discrete arcs (so‐called flow shear arcs), as has been demonstrated in a case study by Sandholt and Farrugia []. This effect may be seen also in Figure .…”

Section: Discussionmentioning

confidence: 99%

Influence of interplanetary magnetic field and solar wind on auroral brightness in different regions

Yang

Wang

et al. 2013

JGR Space Physics

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[1] By integrating and averaging the auroral brightness from Polar Ultraviolet Imager auroral images, which have the whole auroral ovals, and combining the observation data of interplanetary magnetic field (IMF) and solar wind from NASA Operating Missions as a Node on the Internet (OMNI), we investigate the influence of IMF and solar wind on auroral activities, and analyze the separate roles of the solar wind dynamic pressure, density, and velocity on aurora, respectively. We statistically analyze the relations between the interplanetary conditions and the auroral brightness in dawnside, dayside, duskside, and nightside. It is found that the three components of the IMF have different effects on the auroral brightness in the different regions. Different from the nightside auroral brightness, the dawnside, dayside, and duskside auroral brightness are affected by the IMF B x , and B y components more significantly. The IMF B x and B y components have different effects on these three regional auroral brightness under the opposite polarities of the IMF B z . As expected, the nightside aurora is mainly affected by the IMF B z , and under southward IMF, the larger the |B z |, the brighter the nightside aurora. The IMF B x and B y components have no visible effects. On the other hand, it is also found that the aurora is not intensified singly with the increase of the solar wind dynamic pressure: when only the dynamic pressure is high, but the solar wind velocity is not very fast, the aurora will not necessarily be intensified significantly. These results can be used to qualitatively predict the auroral activities in different regions for various interplanetary conditions.

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Section: Discussionmentioning

confidence: 99%

Influence of interplanetary magnetic field and solar wind on auroral brightness in different regions

Yang

Wang

et al. 2013

JGR Space Physics

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“…At Earth, the reconnection process evolves in a transient manner with the occurrence of quasiperiodic bursts, known as flux transfer events [e.g., Russell and Elphic , ]. Ionospheric signatures of bursty magnetopause reconnection at Earth have been observed in the form of poleward‐moving auroral structures (PMAF) [e.g., Milan et al , ; Sandholt and Farrugia , ] and have been associated with mixed magnetospheric and magnetosheath plasma connected to field lines of newly opened flux produced by reconnection [ Lockwood and Wild , ]. Fasel [] performed a statistical study of the properties of these auroral events, including a classification of the different types based on their brightenings history.…”

Section: Introductionmentioning

confidence: 99%

Auroral signatures of multiple magnetopause reconnection at Saturn

Radioti

Grodent

Gérard

et al. 2013

Geophysical Research Letters

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Auroral observations capture the ionospheric response to dynamics of the whole magnetosphere and may provide evidence of the significance of reconnection at Saturn. Bifurcations of the main dayside auroral emission have been related to reconnection at the magnetopause and their surface is suggested to represent the amount of newly opened flux. This work is the first presentation of multiple brightenings of these auroral features based on Cassini ultraviolet auroral observations. In analogy to the terrestrial case, we propose a process, in which a magnetic flux tube reconnects with other flux tubes at multiple sites. This scenario predicts the observed multiple brightenings, it is consistent with subcorotating auroral features which separate from the main emission, and it suggests north‐south auroral asymmetries. We demonstrate that the conditions for multiple magnetopause reconnection can be satisfied at Saturn, like at Earth.

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“…At Earth the reconnection process evolves in a transient manner with the occurrence of quasiperiodic bursts, known as flux transfer events (FTEs) [e.g., Russell and Elphic , 1979]. Ionospheric signatures of FTEs at Earth have been observed in the cusp region where they vary with the form of poleward‐moving auroral structures [e.g., Sandholt et al , 1986; Milan et al , 2000b; Sandholt and Farrugia , 2007, 2008]. They are suggested to be associated with mixed magnetospheric and magnetosheath plasma connected to field lines of newly opened flux produced by reconnection [ Lockwood and Wild , 1993].…”

Section: Introductionmentioning

confidence: 99%

Bifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause

et al. 2011

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[1] This work reports for the first time on bifurcations of the main auroral ring at Saturn observed with the UVIS instrument onboard Cassini. The observation sequence starts with an intensification on the main oval, close to noon, which is possibly associated with dayside reconnection. Consecutive bifurcations appear with the onset of dayside reconnection, between 11 and 18 magnetic local time, while the area poleward of the main emission expands to lower latitudes. The bifurcations depart with time from the main ring of emission, which is related to the open-closed field line boundary. The augmentation of the area poleward of the main emission following its expansion is balanced by the area occupied by the bifurcations, suggesting that these auroral features represent the amount of newly open flux and could be related to consecutive reconnection events at the flank of the magnetopause. The observations show that the open flux along the sequence increases when bifurcations appear. Magnetopause reconnection can lead to significant augmentation of the open flux within a couple of days and each reconnection event opens ∼10% of the flux contained within the polar cap. Additionally, the observations imply an overall length of the reconnection line of ∼4 hours of local time and suggest that dayside reconnection at Saturn can occur at several positions on the magnetopause consecutively or simultaneously.

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The role of external triggers in flow shear arcs in the dayside aurora

Cited by 5 publications

References 40 publications

Influence of interplanetary magnetic field and solar wind on auroral brightness in different regions

Influence of interplanetary magnetic field and solar wind on auroral brightness in different regions

Auroral signatures of multiple magnetopause reconnection at Saturn

Bifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause

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