Publications
276 results found
Sioulas N, Huang Z, Shi C, et al., 2023, Magnetic field spectral evolution in the inner heliosphere, Letters of the Astrophysical Journal, Vol: 943, Pages: 1-7, ISSN: 2041-8205
Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between 0.06 ≲ R ≲ 1 au. The spectrum is studied as a function of scale, normalized to the ion inertial scale di. In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, αB = −3/2, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening toward a αB = −5/3 scaling. It is observed that spectra for intervals with large magnetic energy excesses and low Alfvénic content steepen significantly with distance, in contrast to highly Alfvénic intervals that retain their near-Sun scaling. The occurrence of steeper spectra in slower wind streams may be attributed to the observed positive correlation between solar wind speed and Alfvénicity.
Persson M, Aizawa S, Andre N, et al., 2022, BepiColombo mission confirms stagnation region of Venus and reveals its large extent, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 2
Wimmer-Schweingruber RF, Andre N, Barabash S, et al., 2022, STELLA-Potential European contributions to a NASA-led interstellar probe, FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X
Trotta D, Vuorinen L, Hietala H, et al., 2022, Single-spacecraft techniques for shock parameters estimation: a systematic approach, Frontiers in Astronomy and Space Sciences, Vol: 9, Pages: 1-16, ISSN: 2296-987X
Spacecraft missions provide the unique opportunity to study the properties of collisionless shocks utilising in situ measurements. In the past years, several diagnostics have been developed to address key shock parameters using time series of magnetic field (and plasma) data collected by a single spacecraft crossing a shock front. A critical aspect of such diagnostics is the averaging process involved in the evaluation of upstream/downstream quantities. In this work, we discuss several of these techniques, with a particular focus on the shock obliquity (defined as the angle between the upstream magnetic field and the shock normal vector) estimation. We introduce a systematic variation of the upstream/downstream averaging windows, yielding to an ensemble of shock parameters, which is a useful tool to address the robustness of their estimation. This approach is first tested with a synthetic shock dataset compliant with the Rankine-Hugoniot jump conditions for a shock, including the presence of noise and disturbances. We then employ self-consistent, hybrid kinetic shock simulations to apply the diagnostics to virtual spacecraft crossing the shock front at various stages of its evolution, highlighting the role of shock-induced fluctuations in the parameters’ estimation. This approach has the strong advantage of retaining some important properties of collisionless shock (such as, for example, the shock front microstructure) while being able to set a known, nominal set of shock parameters. Finally, two recent observations of interplanetary shocks from the Solar Orbiter spacecraft are presented, to demonstrate the use of this systematic approach to real events of shock crossings. The approach is also tested on an interplanetary shock measured by the four spacecraft of the Magnetospheric Multiscale (MMS) mission. All the Python software developed and used for the diagnostics (SerPyShock) is made available for the public, including an example of parameter estimation fo
Laker R, Horbury TS, Matteini L, et al., 2022, Switchback deflections beyond the early parker solar probe encounters, Monthly Notices of the Royal Astronomical Society, Vol: 517, Pages: 1001-1005, ISSN: 0035-8711
Switchbacks are Aflvénic fluctuations in the solar wind, which exhibit large rotations in the magnetic field direction. Observations from Parker Solar Probe’s (PSP’s) first two solar encounters have formed the basis for many of the described switchback properties and generation mechanisms. However, this early data may not be representative of the typical near-Sun solar wind, biasing our current understanding of these phenomena. One defining switchback property is the magnetic deflection direction. During the first solar encounter, this was primarily in the tangential direction for the longest switchbacks, which has since been discussed as evidence, and a testable prediction, of several switchback generation methods. In this study, we re-examine the deflection direction of switchbacks during the first eight PSP encounters to confirm the existence of a systematic deflection direction. We first identify switchbacks exceeding a threshold deflection in the magnetic field and confirm a previous finding that they are arc-polarized. In agreement with earlier results from PSP’s first encounter, we find that groups of longer switchbacks tend to deflect in the same direction for several hours. However, in contrast to earlier studies, we find that there is no unique direction for these deflections, although several solar encounters showed a non-uniform distribution in deflection direction with a slight preference for the tangential direction. This result suggests a systematic magnetic configuration for switchback generation, which is consistent with interchange reconnection as a source mechanism, although this new evidence does not rule out other mechanisms, such as the expansion of wave modes.
Owen CJ, Abraham JB, Nicolaou G, et al., 2022, Solar Orbiter SWA Observations of Electron Strahl Properties Inside 1 AU, UNIVERSE, Vol: 8
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- Citations: 3
Aizawa S, Persson M, Menez T, et al., 2022, LatHyS global hybrid simulation of the BepiColombo second Venus flyby, PLANETARY AND SPACE SCIENCE, Vol: 218, ISSN: 0032-0633
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- Citations: 3
Trotta D, Pecora F, Settino A, et al., 2022, On the Transmission of Turbulent Structures across the Earth's Bow Shock, ASTROPHYSICAL JOURNAL, Vol: 933, ISSN: 0004-637X
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- Citations: 7
Dimmock AP, Khotyaintsev YV, Lalti A, et al., 2022, Analysis of multiscale structures at the quasi-perpendicular Venus bow shock Results from Solar Orbiter's first Venus flyby, ASTRONOMY & ASTROPHYSICS, Vol: 660, ISSN: 0004-6361
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- Citations: 3
Reville V, Fargette N, Rouillard AP, et al., 2022, Flux rope and dynamics of the heliospheric current sheet Study of the Parker Solar Probe and Solar Orbiter conjunction of June 2020, Astronomy and Astrophysics: a European journal, Vol: 659, Pages: 1-14, ISSN: 0004-6361
Context. Solar Orbiter and Parker Solar Probe jointly observed the solar wind for the first time in June 2020, capturing data from very different solar wind streams: calm, Alfvénic wind and also highly dynamic large-scale structures.Context. Our aim is to understand the origin and characteristics of the highly dynamic solar wind observed by the two probes, particularly in the vicinity of the heliospheric current sheet (HCS).Methods. We analyzed the plasma data obtained by Parker Solar Probe and Solar Orbiter in situ during the month of June 2020. We used the Alfvén-wave turbulence magnetohydrodynamic solar wind model WindPredict-AW and we performed two 3D simulations based on ADAPT solar magnetograms for this period.Results. We show that the dynamic regions measured by both spacecraft are pervaded by flux ropes close to the HCS. These flux ropes are also present in the simulations, forming at the tip of helmet streamers, that is, at the base of the heliospheric current sheet. The formation mechanism involves a pressure-driven instability followed by a fast tearing reconnection process. We further characterize the 3D spatial structure of helmet streamer born flux ropes, which appears in the simulations to be related to the network of quasi-separatrices.
Desai M, Mitchell DG, McComas DJ, et al., 2022, Suprathermal ion energy spectra and anisotropies near the heliospheric current sheet crossing observed by the Parker Solar Probe during encounter 7, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 927, Pages: 1-12, ISSN: 0004-637X
We present observations of ≳10–100 keV nucleon−1 suprathermal (ST) H, He, O, and Fe ions associated with crossings of the heliospheric current sheet (HCS) at radial distances of <0.1 au from the Sun. Our key findings are as follows: (1) very few heavy ions are detected during the first full crossing, the heavy-ion intensities are reduced during the second partial crossing and peak just after the second crossing; (2) ion arrival times exhibit no velocity dispersion; (3) He pitch-angle distributions track the magnetic field polarity reversal and show up to ∼10:1 anti-sunward, field-aligned flows and beams closer to the HCS that become nearly isotropic farther from the HCS; (4) the He spectrum steepens either side of the HCS, and the He, O, and Fe spectra exhibit power laws of the form ∼E−4–E6; and (5) maximum energies EX increase with the ion's charge-to-mass (Q/M) ratio as ${E}_{X}/{E}_{H}\propto {({Q}_{X}/{M}_{X})}^{\delta }$, where δ ∼ 0.65–0.76, assuming that the average Q states are similar to those measured in gradual and impulsive solar energetic particle events at 1 au. The absence of velocity dispersion in combination with strong field-aligned anisotropies closer to the HCS appears to rule out solar flares and near-Sun coronal-mass-ejection-driven shocks. These new observations present challenges not only for mechanisms that employ direct parallel electric fields and organize maximum energies according to E/Q but also for local diffusive and magnetic-reconnection-driven acceleration models. Reevaluation of our current understanding of the production and transport of energetic ions is necessary to understand this near-solar, current-sheet-associated population of ST ions.
Agapitov V, Drake JF, Swisdak M, et al., 2022, Flux Rope Merging and the Structure of Switchbacks in the Solar Wind, ASTROPHYSICAL JOURNAL, Vol: 925, ISSN: 0004-637X
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- Citations: 9
Moestl C, Weiss AJ, Reiss MA, et al., 2022, Multipoint Interplanetary Coronal Mass Ejections Observed with Solar Orbiter, BepiColombo, Parker Solar Probe, Wind, and STEREO-A, ASTROPHYSICAL JOURNAL LETTERS, Vol: 924, ISSN: 2041-8205
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- Citations: 18
Angelini V, O'Brien H, Horbury T, et al., 2022, Novel magnetic cleaning techniques for Solar Orbiter magnetometer
Solar Orbiter is an ESA mission studying the heliosphere and the Sun. The magnetometer is designed to measure the magnetic field local to the spacecraft and is composed of two sensors located on a boom at different displacement from the spacecraft. This configuration reduces the electromagnetic interference caused by other on-board electrical systems and allows the exploitation of the 'gradiometer technique' to separate spacecraft generated signals from the solar magnetic field. This paper describes the analysis of the magnetometer data to develop a completely novel procedure for removing the magnetic field generated by the spacecraft-controlled heaters, the instruments, and the thrusters on the spacecraft. The difference between the data measured by the two sensors is used to identify this signal, which is then appropriately scaled and removed from the data. This approach produces cleaned magnetic field data which is routinely uploaded to the Solar Orbiter Archive for science exploitation.
Lavraud B, Kieokaew R, Fargette N, et al., 2021, Magnetic reconnection as a mechanism to produce multiple protonpopulations and beams locally in the solar wind, Journal of Astrophysics and Astronomy, Vol: 656, Pages: 1-8, ISSN: 0250-6335
Context. Spacecraft observations early revealed frequent multiple protonpopulations in the solar wind. Decades of research on their origin have focusedon processes such as magnetic reconnection in the low corona and wave-particleinteractions in the corona and locally in the solar wind.Aims.This study aimsto highlight that multiple proton populations and beams are also produced bymagnetic reconnection occurring locally in the solar wind. Methods. We use highresolution Solar Orbiter proton velocity distribution function measurements,complemented by electron and magnetic field data, to analyze the association ofmultiple proton populations and beams with magnetic reconnection during aperiod of slow Alfv\'enic solar wind on 16 July 2020. Results. At least 6reconnecting current sheets with associated multiple proton populations andbeams, including a case of magnetic reconnection at a switchback boundary, arefound during this day. This represents 2% of the measured distributionfunctions. We discuss how this proportion may be underestimated, and how it maydepend on solar wind type and distance from the Sun. Conclusions. Althoughsuggesting a likely small contribution, but which remains to be quantitativelyassessed, Solar Orbiter observations show that magnetic reconnection must beconsidered as one of the mechanisms that produce multiple proton populationsand beams locally in the solar wind.
Adhikari L, Zank GP, Zhao L-L, et al., 2021, Evolution of anisotropic turbulence in the fast and slow solar wind: Theory and Solar Orbiter measurements, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 11
Louarn P, Fedorov A, Prech L, et al., 2021, Multiscale views of an Alfvenic slow solar wind: 3D velocity distribution functions observed by the Proton-Alpha Sensor of Solar Orbiter, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 8
Aran A, Pacheco D, Laurenza M, et al., 2021, Evidence for local particle acceleration in the first recurrent galactic cosmic ray depression observed by Solar Orbiter The ion event on 19 June 2020, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 1
Chust T, Kretzschmar M, Graham DB, et al., 2021, Observations of whistler mode waves by Solar Orbiter's RPW Low Frequency Receiver (LFR): In-flight performance and first results, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 6
Fedorov A, Louarn P, Owen CJ, et al., 2021, Switchback-like structures observed by Solar Orbiter, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 4
Owen CJ, Foster AC, Bruno R, et al., 2021, Solar Orbiter observations of the structure of reconnection outflow layers in the solar wind, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 5
Allen RC, Cernuda I, Pacheco D, et al., 2021, Energetic ions in the Venusian system: Insights from the first Solar Orbiter flyby, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 7
D'Amicis R, Bruno R, Panasenco O, et al., 2021, First Solar Orbiter observation of the Alfvenic slow wind and identification of its solar source, Astronomy and Astrophysics: a European journal, Vol: 656, Pages: 1-17, ISSN: 0004-6361
Context. Turbulence dominated by large-amplitude, nonlinear Alfvén-like fluctuations mainly propagating away from the Sun is ubiquitous in high-speed solar wind streams. Recent studies have demontrated that slow wind streams may also show strong Alfvénic signatures, especially in the inner heliosphere.Aims. The present study focuses on the characterisation of an Alfvénic slow solar wind interval observed by Solar Orbiter between 14 and 18 July 2020 at a heliocentric distance of 0.64 AU.Methods. Our analysis is based on plasma moments and magnetic field measurements from the Solar Wind Analyser (SWA) and Magnetometer (MAG) instruments, respectively. We compared the behaviour of different parameters to characterise the stream in terms of the Alfvénic content and magnetic properties. We also performed a spectral analysis to highlight spectral features and waves signature using power spectral density and magnetic helicity spectrograms, respectively. Moreover, we reconstruct the Solar Orbiter magnetic connectivity to the solar sources both via a ballistic and a potential field source surface (PFSS) model.Results. The Alfvénic slow wind stream described in this paper resembles, in many respects, a fast wind stream. Indeed, at large scales, the time series of the speed profile shows a compression region, a main portion of the stream, and a rarefaction region, characterised by different features. Moreover, before the rarefaction region, we pinpoint several structures at different scales recalling the spaghetti-like flux-tube texture of the interplanetary magnetic field. Finally, we identify the connections between Solar Orbiter in situ measurements, tracing them down to coronal streamer and pseudostreamer configurations.Conclusions. The characterisation of the Alfvénic slow wind stream observed by Solar Orbiter and the identification of its solar source are extremely important aspects for improving the understanding of future observ
Kollhoff A, Kouloumvakos A, Lario D, et al., 2021, The first widespread solar energetic particle event observed by Solar Orbiter on 2020 November 29, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 28
Hadid LZ, Edberg NJT, Chust T, et al., 2021, Solar Orbiter's first Venus flyby: Observations from the Radio and Plasma Wave instrument, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 13
Telloni D, Scolini C, Moestl C, et al., 2021, Study of two interacting interplanetary coronal mass ejections encountered by Solar Orbiter during its first perihelion passage Observations and modeling, Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361
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.
Maksimovic M, Soucek J, Chust T, et al., 2021, First observations and performance of the RPW instrument on board the Solar Orbiter mission, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
Kilpua EKJ, Good SW, Dresing N, et al., 2021, Multi-spacecraft observations of the structure of the sheath of an interplanetary coronal mass ejection and related energetic ion enhancement, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 11
Davies EE, Mostl C, Owens MJ, et al., 2021, In situ multi-spacecraft and remote imaging observations of the first CME detected by Solar Orbiter and BepiColombo, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 22
Zhao L-L, Zank GP, He JS, et al., 2021, Turbulence and wave transmission at an ICME-driven shock observed by the Solar Orbiter and Wind, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361
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- Citations: 10
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