Publications
270 results found
Klein KG, Spence H, Alexandrova O, et al., 2023, HelioSwarm: A Multipoint, Multiscale Mission to Characterize Turbulence, Space Science Reviews, Vol: 219, ISSN: 0038-6308
HelioSwarm (HS) is a NASA Medium-Class Explorer mission of the Heliophysics Division designed to explore the dynamic three-dimensional mechanisms controlling the physics of plasma turbulence, a ubiquitous process occurring in the heliosphere and in plasmas throughout the universe. This will be accomplished by making simultaneous measurements at nine spacecraft with separations spanning magnetohydrodynamic and sub-ion spatial scales in a variety of near-Earth plasmas. In this paper, we describe the scientific background for the HS investigation, the mission goals and objectives, the observatory reference trajectory and instrumentation implementation before the start of Phase B. Through multipoint, multiscale measurements, HS promises to reveal how energy is transferred across scales and boundaries in plasmas throughout the universe.
Laker R, Horbury TS, Woodham LD, et al., 2023, Coherent deflection pattern and associated temperature enhancements in the near-Sun solar wind, Monthly Notices of the Royal Astronomical Society, ISSN: 0035-8711
<jats:title>Abstract</jats:title> <jats:p>Measurements of transverse magnetic field and velocity components from Parker Solar Probe have revealed a coherent quasi-periodic pattern in the near-Sun solar wind. As well as being Alfvénic and arc-polarised, these deflections were characterised by a consistent orientation and an increased proton core temperature, which was greater parallel to the magnetic field. We show that switchbacks represent the largest deflections within this underlying structure, which is itself consistent with the expected outflow from interchange reconnection simulations. Additionally, the spatial scale of the deflections was estimated to be around 1 Mm on the Sun, comparable to the jetting activity observed at coronal bright points within the base of coronal plumes. Therefore, our results could represent the in situ signature of interchange reconnection from coronal bright points within plumes, complementing recent numerical and observational studies. We also found a consistent relationship between the proton core temperature and magnetic field angle across the Parker Solar Probe encounters and discussed how such a persistent signature could be more indicative of an in situ mechanism creating a local increase in temperature. In future, observations of minor ions, radio bursts and remote sensing images could help further establish the connection between reconnection events on the Sun and signatures in the solar wind.</jats:p>
Trotta D, Horbury TS, Lario D, et al., 2023, Irregular Proton Injection to High Energies at Interplanetary Shocks, Astrophysical Journal Letters, Vol: 957, ISSN: 2041-8205
How thermal particles are accelerated to suprathermal energies is an unsolved issue, crucial for many astrophysical systems. We report novel observations of irregular, dispersive enhancements of the suprathermal particle population upstream of a high-Mach-number interplanetary shock. We interpret the observed behavior as irregular “injections” of suprathermal particles resulting from shock front irregularities. Our findings, directly compared to self-consistent simulation results, provide important insights for the study of remote astrophysical systems where shock structuring is often neglected.
Trotta D, Pezzi O, Burgess D, et al., 2023, Three-dimensional modelling of the shock-turbulence interaction, Monthly Notices of the Royal Astronomical Society, Vol: 525, Pages: 1856-1866, ISSN: 0035-8711
The complex interaction between shocks and plasma turbulence is extremely important to address crucial features of energy conversion in a broad range of astrophysical systems. We study the interaction between a supercritical, perpendicular shock and pre-existing, fully developed plasma turbulence, employing a novel combination of magnetohydrodynamic and small-scale, hybrid-kinetic simulations where a shock is propagating through a turbulent medium. The variability of the shock front in the unperturbed case and for two levels of upstream fluctuations is addressed. We find that the behaviour of shock ripples, i.e. shock surface fluctuations with short (a few ion skin depths, di) wavelengths, is modified by the presence of pre-existing turbulence, which also induces strong corrugations of the shock front at larger scales. We link this complex behaviour of the shock front and the shock downstream structuring with the proton temperature anisotropies produced in the shock-turbulence system. Finally, we put our modelling effort in the context of spacecraft observations, elucidating the role of novel cross-scale, multispacecraft measurements in resolving shock front irregularities at different scales. These results are relevant for a broad range of astrophysical systems characterized by the presence of shock waves interacting with plasma turbulence.
Paouris E, Vourlidas A, Kouloumvakos A, et al., 2023, The Space Weather Context of the First Extreme Event of Solar Cycle 25, on 2022 September 5, The Astrophysical Journal, Vol: 956, Pages: 58-58, ISSN: 0004-637X
<jats:title>Abstract</jats:title> <jats:p>The coronal mass ejection (CME) on 2022 September 5 was the fastest CME yet observed and measured in situ by a spacecraft inside the corona (0.06 au for the Parker Solar Probe). Here we assess the significance of this event for space weather studies by analyzing the source region characteristics and its temporal evolution via a magnetic complexity index. We also examine the kinematics and energetics of the CME. We find that it was a very fast and massive event, with a speed greater than 2200 km s<jats:sup>−1</jats:sup> and a mass of 2 × 10<jats:sup>16</jats:sup> g. Consequently, this is within the top 1% of all CMEs observed by SOHO/LASCO since 1996. It is therefore natural to ask, “What if this CME was an Earth-directed one?” To answer this question, we put the CME and the associated flare properties in the context of similar previous extreme events (namely, the 2012 July 23 and 2012 March 7 eruptions), discussing the possibility that these trigger a solar energetic particle (SEP) event. We find that 2022 September 5 could have resulted in a high-energy SEP event. We also estimate the transit time and speed of the CME and calculate the likely Dst variations if this was an Earth-directed event.</jats:p>
Horbury T, Bale S, mcmanus M, et al., 2023, Switchbacks, microstreams and broadband turbulence in the solar wind, Physics of Plasmas, Vol: 30, ISSN: 1070-664X
Switchbacks are a striking phenomenon in near-Sun coronal hole flows, but their origins, evolution, and relation to the broadband fluctuations seen farther from the Sun are unclear. We use the near-radial lineup of Solar Orbiter and Parker Solar Probe during September 2020 when both spacecraft were in wind from the Sun's Southern polar coronal hole to investigate if switchback variability is related to large scale properties near 1 au. Using the measured solar wind speed, we map measurements from both spacecraft to the source surface and consider variations with source Carrington longitude. The patch modulation of switchback amplitudes at Parker at 20 solar radii was associated with speed variations similar to microstreams and corresponds to solar longitudinal scales of around 5°–10°. Near 1 au, this speed variation was absent, probably due to interactions between plasma at different speeds during their propagation. The alpha particle fraction, which has recently been shown to have spatial variability correlated with patches at 20 solar radii, varied on a similar scale at 1 au. The switchback modulation scale of 5°–10°, corresponding to a temporal scale of several hours at Orbiter, was present as a variation in the average deflection of the field from the Parker spiral. While limited to only one stream, these results suggest that in coronal hole flows, switchback patches are related to microstreams, perhaps associated with supergranular boundaries or plumes. Patches of switchbacks appear to evolve into large scale fluctuations, which might be one driver of the ubiquitous turbulent fluctuations in the solar wind.
Livi S, Lepri ST, Raines JM, et al., 2023, First results from the Solar Orbiter Heavy Ion Sensor, ASTRONOMY & ASTROPHYSICS, Vol: 676, ISSN: 0004-6361
Zhu X, He J, Duan D, et al., 2023, Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations, ASTROPHYSICAL JOURNAL, Vol: 953, ISSN: 0004-637X
Wimmer-Schweingruber RF, André N, Barabash S, et al., 2023, STELLA — In situ Investigations of the Very Local Interstellar Medium, Vol. 55, Issue 3 (Heliophysics 2024 Decadal Whitepapers)
Chen L-J, Spence H, Klein K, et al., 2023, Plasma turbulence: Challenges and next transformative steps from the perspective of multi-spacecraft measurements, Vol. 55, Issue 3 (Heliophysics 2024 Decadal Whitepapers)
Suen GHH, Owen CJ, Verscharen D, et al., 2023, Magnetic reconnection as an erosion mechanism for magnetic switchbacks, ASTRONOMY & ASTROPHYSICS, Vol: 675, ISSN: 0004-6361
Sioulas N, Velli M, Huang Z, et al., 2023, On the Evolution of the Anisotropic Scaling of Magnetohydrodynamic Turbulence in the Inner Heliosphere, ASTROPHYSICAL JOURNAL, Vol: 951, ISSN: 0004-637X
Duan D, He J, Zhu X, et al., 2023, Kinetic Features of Alpha Particles in a Pestchek-like Magnetic Reconnection Event in the Solar Wind Observed by Solar Orbiter, ASTROPHYSICAL JOURNAL LETTERS, Vol: 952, ISSN: 2041-8205
Yardley SL, Owen CJ, Long DM, et al., 2023, Slow Solar Wind Connection Science during Solar Orbiter's First Close Perihelion Passage, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 267, ISSN: 0067-0049
Bale SD, Drake JF, McManus MD, et al., 2023, Interchange reconnection as the source of the fast solar wind within coronal holes, NATURE, Vol: 618, Pages: 252-+, ISSN: 0028-0836
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- Citations: 8
Baker D, Demoulin P, Yardley SL, et al., 2023, Observational Evidence of S-web Source of the Slow Solar Wind, ASTROPHYSICAL JOURNAL, Vol: 950, ISSN: 0004-637X
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- Citations: 1
Fargette N, Lavraud B, Rouillard AP, et al., 2023, Clustering of magnetic reconnection exhausts in the solar wind: An automated detection study, Astronomy and Astrophysics: a European journal, Vol: 674, Pages: 1-15, ISSN: 0004-6361
Context. Magnetic reconnection is a fundamental process in astrophysical plasmas that enables the dissipation of magnetic energy at kinetic scales. Detecting this process in situ is therefore key to furthering our understanding of energy conversion in space plasmas. However, reconnection jets typically scale from seconds to minutes in situ, and as such, finding them in the decades of data provided by solar wind missions since the beginning of the space era is an onerous task.Aims. In this work, we present a new approach for automatically identifying reconnection exhausts in situ in the solar wind. We apply the algorithm to Solar Orbiter data obtained while the spacecraft was positioned at between 0.6 and 0.8 AU and perform a statistical study on the jets we detect.Methods. The method for automatic detection is inspired by the visual identification process and strongly relies on the Walén relation. It is enhanced through the use of Bayesian inference and physical considerations to detect reconnection jets with a consistent approach.Results. Applying the detection algorithm to one month of Solar Orbiter data near 0.7 AU, we find an occurrence rate of seven jets per day, which is significantly higher than in previous studies performed at 1 AU. We show that they tend to cluster in the solar wind and are less likely to occur in the tenuous solar wind (< 10 cm−3 near 0.7 AU). We discuss why the source and the degree of Alfvénicity of the solar wind might have an impact on magnetic reconnection occurrence.Conclusions. By providing a tool to quickly identify potential magnetic reconnection exhausts in situ, we pave the way for broader statistical studies on magnetic reconnection in diverse plasma environments.
Safrankova J, Nemecek Z, Nemec F, et al., 2023, Evolution of Magnetic Field Fluctuations and Their Spectral Properties within the Heliosphere: Statistical Approach, ASTROPHYSICAL JOURNAL LETTERS, Vol: 946, ISSN: 2041-8205
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- Citations: 1
Raouafi NE, Stenborg G, Seaton DB, et al., 2023, Magnetic Reconnection as the Driver of the Solar Wind, ASTROPHYSICAL JOURNAL, Vol: 945, ISSN: 0004-637X
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- Citations: 17
Brandt PC, Provornikova E, Bale SD, et al., 2023, Future Exploration of the Outer Heliosphere and Very Local Interstellar Medium by Interstellar Probe, SPACE SCIENCE REVIEWS, Vol: 219, ISSN: 0038-6308
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- Citations: 4
Krasnoselskikh V, Tsurutani BT, Dudok de Wit T, et al., 2023, ICARUS: in-situ studies of the solar corona beyond Parker Solar Probe and Solar Orbiter, Experimental Astronomy, Vol: 54, Pages: 277-315, ISSN: 0922-6435
The primary scientific goal of ICARUS (Investigation of Coronal AcceleRation and heating of solar wind Up to the Sun), a mother-daughter satellite mission, proposed in response to the ESA “Voyage 2050” Call, will be to determine how the magnetic field and plasma dynamics in the outer solar atmosphere give rise to the corona, the solar wind, and the entire heliosphere. Reaching this goal will be a Rosetta Stone step, with results that are broadly applicable within the fields of space plasma physics and astrophysics. Within ESA’s Cosmic Vision roadmap, these science goals address Theme 2: “How does the Solar System work?” by investigating basic processes occurring “From the Sun to the edge of the Solar System”. ICARUS will not only advance our understanding of the plasma environment around our Sun, but also of the numerous magnetically active stars with hot plasma coronae. ICARUS I will perform the first direct in situ measurements of electromagnetic fields, particle acceleration, wave activity, energy distribution, and flows directly in the regions in which the solar wind emerges from the coronal plasma. ICARUS I will have a perihelion altitude of 1 solar radius and will cross the region where the major energy deposition occurs. The polar orbit of ICARUS I will enable crossing the regions where both the fast and slow winds are generated. It will probe the local characteristics of the plasma and provide unique information about the physical processes involved in the creation of the solar wind. ICARUS II will observe this region using remote-sensing instruments, providing simultaneous, contextual information about regions crossed by ICARUS I and the solar atmosphere below as observed by solar telescopes. It will thus provide bridges for understanding the magnetic links between the heliosphere and the solar atmosphere. Such information is crucial to our understanding of the plasma physics and electrodynamics of the solar atmosph
Raouafi NE, Matteini L, Squire J, et al., 2023, Parker solar probe: four years of discoveries at solar cycle minimum, Space Science Reviews, Vol: 219, Pages: 1-140, ISSN: 0038-6308
Launched on 12 Aug. 2018, NASA’s Parker Solar Probe had completed 13 of its scheduled 24 orbits around the Sun by Nov. 2022. The mission’s primary science goal is to determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Parker Solar Probe returned a treasure trove of science data that far exceeded quality, significance, and quantity expectations, leading to a significant number of discoveries reported in nearly 700 peer-reviewed publications. The first four years of the 7-year primary mission duration have been mostly during solar minimum conditions with few major solar events. Starting with orbit 8 (i.e., 28 Apr. 2021), Parker flew through the magnetically dominated corona, i.e., sub-Alfvénic solar wind, which is one of the mission’s primary objectives. In this paper, we present an overview of the scientific advances made mainly during the first four years of the Parker Solar Probe mission, which go well beyond the three science objectives that are: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles.
Trotta D, Hietala H, Horbury T, et al., 2023, Multi-spacecraft observations of shocklets at an interplanetary shock, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 520, Pages: 437-445, ISSN: 0035-8711
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- Citations: 2
De Marco R, Bruno R, Jagarlamudi VK, et al., 2023, Innovative technique for separating proton core, proton beam, and alpha particles in solar wind 3D velocity distribution functions, ASTRONOMY & ASTROPHYSICS, Vol: 669, ISSN: 0004-6361
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- Citations: 1
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
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