| 1. |
- Hietala, H., et al.
(författare)
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Supermagnetosonic subsolar magnetosheath jets and their effects : from the solar wind to the ionospheric convection
- 2012
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 30:1, s. 33-48
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Tidskriftsartikel (refereegranskat)abstract
- It has recently been proposed that ripples inherent to the bow shock during radial interplanetary magnetic field (IMF) may produce local high speed flows in the magnetosheath. These jets can have a dynamic pressure much larger than the dynamic pressure of the solar wind. On 17 March 2007, several jets of this type were observed by the Cluster spacecraft. We study in detail these jets and their effects on the magnetopause, the magnetosphere, and the ionospheric convection. We find that (1) the jets could have a scale size of up to a few RE but less than similar to 6 R-E transverse to the XGSE axis; (2) the jets caused significant local magnetopause perturbations due to their high dynamic pressure; (3) during the period when the jets were observed, irregular pulsations at the geostationary orbit and localised flow enhancements in the ionosphere were detected. We suggest that these inner magnetospheric phenomena were caused by the magnetosheath jets.
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| 2. |
- Karlsson, Tomas, et al.
(författare)
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Quiet, Discrete Auroral Arcs-Observations
- 2020
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Ingår i: Space Science Reviews. - : Springer. - 0038-6308 .- 1572-9672. ; 216:1
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Forskningsöversikt (refereegranskat)abstract
- Quiet, discrete auroral arcs are an important and fundamental consequence of solar wind-magnetosphere interaction. We summarize the current standing of observations of such auroral arcs. We review the basic characteristics of the arcs, including occurrence in time and space, lifetimes, width and length, as well as brightness, and the energy of the magnetospheric electrons responsible for the optical emission. We briefly discuss the connection between single and multiple discrete arcs. The acceleration of the magnetospheric electrons by high-altitude electric potential structure is reviewed, together with our current knowledge of these structures. Observations relating to the potential drop, altitude distribution and lifetimes are reviewed, as well as direct evidence for the parallel electric fields of the acceleration structures. The current closure in the ionosphere of the currents carried by the auroral electrons is discussed together with its impact on the ionosphere and thermosphere. The connection of auroral arcs to the magnetosphere and generator regions is briefly touched upon. Finally we discuss how to progress from the current observational status to further our understanding of auroral arcs.
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| 3. |
- Norenius, Linus, et al.
(författare)
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Ground-Based Magnetometer Response to Impacting Magnetosheath Jets
- 2021
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Ingår i: Journal of Geophysical Research - Space Physics. - : John Wiley & Sons. - 2169-9380 .- 2169-9402. ; 126:8
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Tidskriftsartikel (refereegranskat)abstract
- Localized dynamic pressure pulses in the magnetosheath, or jets, have been a popular topic for discussion in recent decades. Studies show that they can propagate through the magnetosheath and impact the magnetopause, possibly showing up as geoeffective elements at ground level. However, questions still remain on how geoeffective they can be. Previous studies have been limited to case studies during few days and with only a handful of events. In this study we have found 65 cases of impacting jets using observations from the Multiscale Magnetospheric mission during 2015–2017. We examine their geoeffectiveness using ground-based magnetometers (GMAGs). From our statistics we find that GMAGs observe responses as fluctuations in the geomagnetic field with amplitudes of 34 nT, frequencies of 1.9 mHz, and damping times of 370 s. Further, the parallel length and the maximum dynamic pressure of the jet dictate the amplitude of the observed GMAG response. Longer and higher pressure jets inducing larger amplitude responses in GMAG horizontal components. The median time required for the signal to be detected by GMAGs is 190 s. We also examine if jets can be harmful for human infrastructure and cannot exclude that such events could exist.
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