| 1. |
- Telloni, D., et al.
(författare)
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Study of two interacting interplanetary coronal mass ejections encountered by Solar Orbiter during its first perihelion passage Observations and modeling
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 656
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Tidskriftsartikel (refereegranskat)abstract
- Context. Solar Orbiter, the new-generation mission dedicated to solar and heliospheric exploration, was successfully launched on February 10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion passage in June 2020, two successive interplanetary coronal mass ejections (ICMEs), propagating along the heliospheric current sheet (HCS), impacted the spacecraft.Aims. This paper addresses the investigation of the ICMEs encountered by Solar Orbiter on June 7-8, 2020, from both an observational and a modeling perspective. The aim is to provide a full description of those events, their mutual interaction, and their coupling with the ambient solar wind and the HCS.Methods. Data acquired by the MAG magnetometer, the Energetic Particle Detector suite, and the Radio and Plasma Waves instrument are used to provide information on the ICMEs' magnetic topology configuration, their magnetic connectivity to the Sun, and insights into the heliospheric plasma environment where they travel, respectively. On the modeling side, the Heliospheric Upwind eXtrapolation model, the 3D COronal Rope Ejection technique, and the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) tool are used to complement Solar Orbiter observations of the ambient solar wind and ICMEs, and to simulate the evolution and interaction of the ejecta in the inner heliosphere, respectively.Results. Both data analysis and numerical simulations indicate that the passage of two distinct, dynamically and magnetically interacting (via magnetic reconnection processes) ICMEs at Solar Orbiter is a possible scenario, supported by the numerous similarities between EUHFORIA time series at Solar Orbiter and Solar Orbiter data.Conclusions. The combination of in situ measurements and numerical simulations (together with remote sensing observations of the corona and inner heliosphere) will significantly lead to a deeper understanding of the physical processes occurring during the CME-CME interaction.
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| 2. |
- Larosa, A., et al.
(författare)
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Evolution of the magnetic field rotation distributions in the inner heliosphere
- 2024
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 686
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Tidskriftsartikel (refereegranskat)abstract
- Context. The nature and evolution of the solar wind magnetic field rotations is studied in data from the Parker Solar Probe. Aims. We investigated the magnetic field deflections in the inner heliosphere below 0.5 au in a distance-and scale-dependent manner to shed some light on the mechanism behind their evolution. Methods. We used the magnetic field data from the FIELDS instrument suite to study the evolution of the magnetic field vector increment and rotation distributions that contain switchbacks. Results. We find that the rotation distributions evolve in a scale-dependent fashion. They have the same shape at small scales regardless of the radial distance, in contrast to larger scales, where the shape evolves with distance. The increments are shown to evolve towards a log-normal shape with increasing radial distance, even though the log-normal fit works quite well at all distances, especially at small scales. The rotation distributions are shown to evolve towards a previously developed rotation model moving away from the Sun. Conclusions. Our results suggest a scenario in which the evolution of the rotation distributions is primarily the result of the expansion-driven growth of the fluctuations, which are reshaped into a log-normal distribution by the solar wind turbulence.
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| 3. |
- Perrone, D., et al.
(författare)
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Evolution of coronal hole solar wind in the inner heliosphere : Combined observations by Solar Orbiter and Parker Solar Probe
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 668
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Tidskriftsartikel (refereegranskat)abstract
- We study the radial evolution, from 0.1 AU to the Earth, of a homogeneous recurrent fast wind, coming from the same source on the Sun, by means of new measurements by both Solar Orbiter and Parker Solar Probe. With respect to previous radial studies, we extend, for the first time, the analysis of a recurrent fast stream at distances never reached prior to the Parker Solar Probe mission. Confirming previous findings, the observations show: (i) a decrease in the radial trend of the proton density that is slower than the one expected for a radially expanding plasma, due to the possible presence of a secondary beam in the velocity distribution function; (ii) a deviation for the magnetic field from the Parker prediction, supported by the strong Alfvenicity of the stream at all distances; and (iii) a slower decrease in the proton temperature with respect to the adiabatic prediction, suggesting the local presence of external heating mechanisms. Focusing on the radial evolution of the turbulence, from the inertial to the kinetic range along the turbulent cascade, we find that the slopes, in both frequency ranges, strongly depend on the different turbulence observed by the two spacecraft, namely a mostly parallel turbulence in the Parker Solar Probe data and a mostly perpendicular turbulence in the Solar Orbiter intervals. Moreover, we observe a decrease in the level of intermittency for the magnetic field during the expansion of the stream. Furthermore, we perform, for the first time, a statistical analysis of coherent structures around proton scales at 0.1 AU and we study how some of their statistical properties change from the Sun to the Earth. As expected, we find a higher occurrence of events in the Parker Solar Probe measurements than in the Solar Orbiter data, considering the ratio between the intervals length and the proton characteristic scales at the two radial distances. Finally, we complement this statistical analysis with two case studies of current sheets and vortex-like structures detected at the two radial distances, and we find that structures that belong to the same family have similar characteristics at different radial distances. This work provides an insight into the radial evolution of the turbulent character of solar wind plasma coming from coronal holes.
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