| 1. |
- Telloni, Daniele, et al.
(författare)
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Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations
- 2022
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Ingår i: Astrophysical Journal. - : IOP Publishing Ltd. - 0004-637X .- 1538-4357. ; 935:2
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Tidskriftsartikel (refereegranskat)abstract
- The solar wind measured in situ by Parker Solar Probe in the very inner heliosphere is studied in combination with the remote-sensing observation of the coronal source region provided by the METIS coronagraph aboard Solar Orbiter. The coronal outflows observed near the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and 6.3 R (circle dot) above the eastern solar limb, can be associated with the streams sampled by PSP at 0.11 and 0.26 au from the Sun, in two time intervals almost 5 days apart. The two plasma flows come from two distinct source regions, characterized by different magnetic field polarity and intensity at the coronal base. It follows that both the global and local properties of the two streams are different. Specifically, the solar wind emanating from the stronger magnetic field region has a lower bulk flux density, as expected, and is in a state of well-developed Alfvenic turbulence, with low intermittency. This is interpreted in terms of slab turbulence in the context of nearly incompressible magnetohydrodynamics. Conversely, the highly intermittent and poorly developed turbulent behavior of the solar wind from the weaker magnetic field region is presumably due to large magnetic deflections most likely attributed to the presence of switchbacks of interchange reconnection origin.
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| 2. |
- Telloni, Daniele, et al.
(författare)
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Observation and Modeling of the Solar Wind Turbulence Evolution in the Sub-Mercury Inner Heliosphere
- 2022
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Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 938:2
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Tidskriftsartikel (refereegranskat)abstract
- This letter exploits the radial alignment between the Parker Solar Probe and BepiColombo in late 2022 February, when both spacecraft were within Mercury's orbit. This allows the study of the turbulent evolution, namely, the change in spectral and intermittency properties, of the same plasma parcel during its expansion from 0.11 to 0.33 au, a still unexplored region. The observational analysis of the solar wind turbulent features at the two different evolution stages is complemented by a theoretical description based on the turbulence transport model equations for nearly incompressible magnetohydrodynamics. The results provide strong evidence that the solar wind turbulence already undergoes significant evolution at distances less than 0.3 au from the Sun, which can be satisfactorily explained as due to evolving slab fluctuations. This work represents a step forward in understanding the processes that control the transition from weak to strong turbulence in the solar wind and in properly modeling the heliosphere.
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| 3. |
- Telloni, Daniele, et al.
(författare)
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Observation of a Magnetic Switchback in the Solar Corona
- 2022
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Ingår i: Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205 .- 2041-8213. ; 936:2
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Tidskriftsartikel (refereegranskat)abstract
- Switchbacks are sudden, large radial deflections of the solar wind magnetic field, widely revealed in interplanetary space by the Parker Solar Probe. The switchbacks' formation mechanism and sources are still unresolved, although candidate mechanisms include Alfvenic turbulence, shear-driven Kelvin-Helmholtz instabilities, interchange reconnection, and geometrical effects related to the Parker spiral. This Letter presents observations from the Metis coronagraph on board a Solar Orbiter of a single large propagating S-shaped vortex, interpreted as the first evidence of a switchback in the solar corona. It originated above an active region with the related loop system bounded by open-field regions to the east and west. Observations, modeling, and theory provide strong arguments in favor of the interchange reconnection origin of switchbacks. Metis measurements suggest that the initiation of the switchback may also be an indicator of the origin of slow solar wind.
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