Imperial College London

Dr Lorenzo Matteini

Faculty of Natural SciencesDepartment of Physics

Lecturer in Space Plasma Physics
 
 
 
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Contact

 

l.matteini

 
 
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Location

 

Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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98 results found

Laker R, Horbury TS, Woodham LD, Bale SD, Matteini Let al., 2024, Coherent deflection patternãndãssociated temperature enhancements in the near-Sun solar wind, Monthly Notices of the Royal Astronomical Society, Vol: 527, Pages: 10440-10447, ISSN: 0035-8711

Measurements of transverse magnetic fieldãnd velocity components from Parker Solar Probe hav e rev ealedã coherent quasi- periodic pattern in the near-Sun solar wind. As wellãs being Alfvénicãndãrc-polarized, these deflections were characterized byã consistent orientationãndãn 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 beãround 1 Mm on the Sun, comparable to the jettingãctivity observedãt 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 numericalãnd observational studies. Weãlso foundã consistent relationship between the proton core temperatureãnd magnetic fieldãngleãcross the Parker Solar Probe encountersãnd discussed how suchã persistent signature could be more indicative ofãn in situ mechanism creatingã local increase in temperature. In future, observations of minor ions, radio bursts,ãnd remote sensing images could help further establish the connection between reconnection events on the Sunãnd signatures in the solar wind.

Journal article

Horbury T, Bale S, mcmanus M, Larson D, Kasper J, Laker R, Matteini L, Raouafi N, Velli M, Woodham L, Woolley T, Fedorov A, Louarn P, Kieokaew R, Durovcova T, Chandran B, Owen Cet 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.

Journal article

Lewis HC, Stawarz JE, Franci L, Matteini L, Klein K, Salem CS, Burch JL, Ergun RE, Giles BL, Russell CT, Lindqvist P-Aet al., 2023, Magnetospheric Multiscale measurements of turbulent electric fields in earth's magnetosheath: How do plasma conditions influence the balance of terms in generalized Ohm's law?, PHYSICS OF PLASMAS, Vol: 30, ISSN: 1070-664X

Journal article

Huang Z, Sioulas N, Shi C, Velli M, Bowen T, Davis N, Chandran BDG, Matteini L, Kang N, Shi X, Huang J, Bale SD, Kasper JC, Larson DE, Livi R, Whittlesey PL, Rahmati A, Paulson K, Stevens M, Case AW, de Wit TD, Malaspina DMM, Bonnell JW, Goetz K, Harvey PRR, MacDowall RJJet al., 2023, New Observations of Solar Wind 1/<i>f</i> Turbulence Spectrum from Parker Solar Probe, ASTROPHYSICAL JOURNAL LETTERS, Vol: 950, ISSN: 2041-8205

Journal article

Franci L, Papini E, Del Sarto D, Micera A, Stawarz J, Horbury T, Lapenta G, Lewis H, Salem C, Landi S, Hellinger P, Matteini L, Cicone A, Piersanti M, Innocenti ME, Maksimovic M, Burgess Det al., 2023, On the nature of electric field fluctuations in the near-Sun solar wind and its implication for the turbulent energy transfer at ion and electron scales

<jats:p>We model plasma turbulence in the near-Sun solar wind by means of a high-resolution fully kinetic simulation initialised with average plasma conditions measured by Parker Solar Probe during its first solar encounter. Once turbulence is fully developed, the power spectra of the plasma and electromagnetic fluctuations exhibit clear power-law intervals down to sub-electron scales. Our simulation models the electron-scale electric field fluctuations with unprecedented accuracy. This allows us to perform the first detailed analysis of the different terms of the electric field in the generalised Ohm's law (MHD, Hall, and electron pressure terms) at ion and electron scales, both in physical space and in Fourier space. Such analysis suggests rewriting the Ohm&amp;#8217;s law in a different form, which disentangles the contribution of different underlying plasma mechanisms, characterising the nature of the electric field fluctuations in the different range of scales. This provides a new insight on how energy in the turbulent electromagnetic fields is transferred through ion and electron scales and seems to favour the role of pressure-balanced structures versus waves. We finally test our assumptions and numerical results by means of a statistical analysis using magnetic field, electric field, and electron density data from Solar Orbiter and Parker Solar Probe. Preliminary results show good agreement with our theoretical expectations inspired by our simulation.</jats:p>

Other

Lewis H, Stawarz J, Franci L, Matteini L, Klein K, Salem Cet al., 2023, Generalised Ohm’s Law in the Magnetosheath: How do plasma conditions impact turbulent electric fields?

<jats:p>Turbulence is a complex phenomenon whereby fluctuation energy is transferred between different scale sizes as a result of nonlinear interactions. Electromagnetic turbulence is ubiquitous within space plasmas, wherein it is associated with numerous nonlinear interactions. The dynamics of the magnetic field, which are widely studied in turbulence theory, are intimately linked to the electric field, which controls the exchange of energy between the magnetic field and the particles. Magnetospheric Multiscale (MMS) provides the unique opportunity to decompose electric field dynamics into contributions from different linear and nonlinear processes. The evolution of the electric field is described by generalised Ohm&amp;#8217;s law, which breaks down the dynamics into components arising from different physical effects. Using high-resolution multipoint measurements, we compute the MHD, Hall and Electron Pressure terms of generalised Ohm&amp;#8217;s law for 60 turbulent magnetosheath intervals. These terms, which have varying contributions to the dynamics as a function of scale, arise as a result of different physical effects related to a range of underlying turbulent phenomena. We examine how two characteristics of the turbulent electric field spectra depend on plasma conditions: the transition scale between MHD and Hall dominance (the &amp;#8216;Hall scale&amp;#8217;, kHall) and the relative amplitude of Hall and Electron Pressure contributions. Motivated by dimensional analysis arguments which appeal to characteristics of the plasma and the turbulence that can be quantified in a number of ways by MMS, we demonstrate the necessary refinements required to reproduce measured values. The scalar isotropic kinetic Alfven wave prediction for the ratio of Electron Pressure to Hall terms as a function of plasma beta is not consistent with measurements. We observe that the MHD and Hall terms are dominated by either nonlinear or linear dynamics, dependi

Other

Stawarz JE, Woodham L, Laker R, Matteini L, Horbury T, Woolley T, Bale S, Perrone D, Toledo-Redondo S, Sorriso-Valvo L, DAmicis R, Rivera Y, Paulson Ket al., 2023, The Evolution of Turbulence in the Inner Heliosphere: Insights from the February 2022 Radial Alignment between Parker Solar Probe and Solar Orbiter

<jats:p>The solar wind is filled with complex turbulent dynamics that transfer energy from large length scales to progressively smaller scales. This transfer of energy generates a multitude of thin structures, such as current sheets, in the plasma with a preference for forming particularly strong gradients &amp;#8211; a property know as intermittency &amp;#8211; that are thought to play a role in turbulent dissipation. One of the important problems in the study of solar wind turbulence is understanding how and to what extent the nature of the turbulent dynamics vary as the solar wind expands from the Sun. However, disentangling the dynamical evolution of the turbulence from variations in the properties of different solar wind streams and temporal variations in the source region of a given stream has traditionally been challenging in the solar wind. We make use of a fortuitous alignment between NASA&amp;#8217;s Parker Solar Probe and ESA&amp;#8217;s Solar Orbiter spacecraft, which occurred at the end of February 2022, to examine how the turbulent fluctuations in the solar wind evolve with radial distance. During this radial alignment the two spacecraft observed the same stream of solar wind plasma, and potentially nearly the same parcel of plasma, at two different radial distances allowing us to separate the evolution with radial distance from the other sources of variability. We explore both the statistical properties of the fluctuations as well as the nature of the most intermittent structures observed by the spacecraft at different length scales in the plasma. The results demonstrate that, while the intermittent fluctuations in the components perpendicular to the radial direction are statistically similar at different radial distances, the intermittency properties in the radial direction can significantly change with distance. Comparisons of the observational results with expanding box simulations of turbulence suggest that some of the key fe

Other

Raouafi NE, Matteini L, Squire J, Badman ST, Velli M, Klein KG, Chen CHK, Matthaeus WH, Szabo A, Linton M, Allen RC, Szalay JR, Bruno R, Decker RB, Akhavan-Tafti M, Agapitov OV, Bale SD, Bandyopadhyay R, Battams K, Berčič L, Bourouaine S, Bowen T, Cattell C, Chandran BDG, Chhiber R, Cohen CMS, D'Amicis R, Giacalone J, Hess P, Howard RA, Horbury TS, Jagarlamudi VK, Joyce CJ, Kasper JC, Kinnison J, Laker R, Liewer P, Malaspina DM, Mann I, McComas DJ, Niembro-Hernandez T, Panasenco O, Pokorný P, Pusack A, Pulupa M, Perez JC, Riley P, Rouillard AP, Shi C, Stenborg G, Tenerani A, Verniero JL, Viall N, Vourlidas A, Wood BE, Woodham LD, Woolley Tet 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.

Journal article

Laker R, Horbury TS, Matteini L, Bale SD, Stawarz JE, Woodham LD, Woolley Tet 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.

Journal article

Grant S, Jones G, Owen C, Matteini Let al., 2022, The Prediction of, and Results from Solar Orbiter's encounter with Comet C/2021 A1 (Leonard).

<jats:p>&amp;lt;p&amp;gt;As the solar wind encounters a comet, ionized gas released from the nucleus propagates away from the Sun with the wind, forming the ion tail of the comet that can stretch for multiple astronomical units. The transport of cometary material antisunward of the comet provides opportunities to measure the cometary composition and plasma interactions at a significant distance from a comet&amp;amp;#8217;s nucleus. Serendipitous crossings by spacecraft of comets&amp;amp;#8217; ion tails is a surprisingly commonplace occurrence, but can go unnoticed, as any measured plasma fluctuations can be small.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Using the measured flow of the solar wind at the spacecraft, we can estimate the motion of the solar plasma upstream of the spacecraft, and compare this trajectory with the locations of known comets. This method can uncover previously unnoticed ion tail encounters and predict future encounters.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;In December 2021, while comet C/2021 A1 (Leonard) traversed the ecliptic plane, sunward of the spacecraft Solar Orbiter, the spacecraft was immersed in the comet&amp;amp;#8217;s ion tail. This encounter was predicted using a range of estimated solar wind velocities to estimate the motion of solar wind plasma to the spacecraft. A wealth of data was collected during the encounter, including results from multiple instruments that support the prediction. We present data returned from the SWA and magnetometer instruments, providing information on the structure of the induced magnetotail. Additionally, images of comet Leonard&amp;amp;#8217;s ion tail from other spacecraft during the encounter provide a uniquely complete picture of the tail crossing.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;em&amp;gt;Fig: Orbital configuration of comet Leonard and Sola

Journal article

Franci L, Papini E, Del Sarto D, Hellinger P, Burgess D, Matteini L, Landi S, Montagud-Camps Vet al., 2022, Plasma Turbulence in the Near-Sun and Near-Earth Solar Wind: A Comparison via Observation-Driven 2D Hybrid Simulations, UNIVERSE, Vol: 8

Journal article

McManus MD, Verniero J, Bale SD, Bowen TA, Larson DE, Kasper JC, Livi R, Matteini L, Rahmati A, Romeo O, Whittlesey P, Woolley Tet al., 2022, Density and Velocity Fluctuations of Alpha Particles in Magnetic Switchbacks, ASTROPHYSICAL JOURNAL, Vol: 933, ISSN: 0004-637X

Journal article

Hellinger P, Montagud-Camps V, Franci L, Matteini L, Papini E, Verdini A, Landi Set al., 2022, Ion-scale Transition of Plasma Turbulence: Pressure-Strain Effect, ASTROPHYSICAL JOURNAL, Vol: 930, ISSN: 0004-637X

Journal article

Matteini L, Hellinger P, Landi S, Franci L, Tenerani A, Velli Met al., 2022, Kinetic Instabilities from Ion Beams and Differential Streaming in the Close-Sun Solar Wind: Hybrid Expanding Simulations

<jats:p>&amp;lt;p&amp;gt;Parker Solar Probe observations in the inner heliosphere have demonstrated that non-thermal features in solar wind ion distributions are particularly enhanced and dominant in the close-Sun environment. Proton beams and large differential flows of alpha particles are ubiquitously observed, also in slow, though Alfv&amp;amp;#233;nic, streams, qualitatively at odds with typical observations at 1AU, where non-Maxwellian features are usually less apparent in the slow solar wind. All this reinforces the idea, also supported by past Helios and Ulysses explorations, that preferential ion heating and acceleration take place already in the Corona and signatures of the kinetic processes involved are gradually washed out during expansion. To explore further properties of ion differential streaming during expansion, as well as associated kinetic instabilities and their possible role in plasma heating, we perform expanding box hybrid simulations of a multi-species solar wind composed by proton core, beam and alpha particles, focussing on the role of wave-particle interactions in shaping distribution functions and controlling relative drifts. Radial trends and typical distributions found in simulations are then compared with PSP and Solar Orbiter observations in the inner Heliosphere.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Hellinger P, Montagud-Camps V, Franci L, Matteini L, Papini E, Verdini A, Landi Set al., 2022, Ion-scale transition of plasma turbulence: Pressure-strain effect

<jats:p>&amp;lt;p&amp;gt;We investigate properties of solar-wind like plasma turbulence using direct numerical simulations. We analyze the transition from large (magnetohydrodynamic) scales to ion ones using two-dimensional hybrid (fluid electrons, kinetic ions) simulations of decaying turbulence. To quantify turbulence properties we apply spectral transfer and Karman-Howarth-Monin equations for extended compressible Hall MHD to the simulated results. The simulation results indicate that the transition from MHD to ion scales (the so called ion break) results from a combination of an onset of Hall physics and of an effective dissipation owing to the pressure-strain energy-exchange channel and resistivity. We discuss the simulation results in the context of the solar wind.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Franci L, Papini E, Micera A, Matteini L, Stawarz J, Lapenta G, Burgess D, Hellinger P, Landi S, Verdini A, Montagud-Camps Vet al., 2022, Fully kinetic simulations of the near-Sun solar wind plasma: turbulence, reconnection, and particle heating

<jats:p>&amp;lt;p&amp;gt;We model the development of plasma turbulence in the near-Sun solar wind with high-resolution fully-kinetic particle-in-cell (PIC) simulations, initialised with plasma conditions measured by Parker Solar Probe during its first solar encounter (ion and electron plasma beta &amp;amp;#8804; 1 and a large amplitude of the turbulent fluctuations). The power spectra of the plasma and electromagnetic fluctuations are characterized by multiple power-law intervals, with a transition and a considerable steepening in correspondence of the electron scales. In the same range of scales, the kurtosis of the magnetic fluctuations is observed to further increase, hinting at a higher level of intermittency. We observe a number of electron-only reconnection events, which are responsible for an increase of the electron temperature in the direction parallel to the ambient field. The total electron temperature, however, exhibits only a small increase due to the cooling of electrons in the perpendicular direction, leading to a strong temperature anisotropy. We also analyse the power spectra of the different terms of the electric field in the generalised Ohm&amp;amp;#8217;s law, their linear and nonlinear components, and their alignment, to get a deeper insight on the nature of the turbulent cascade. Finally, we compare our results with those from hybrid simulations with the same parameters, as well as with spacecraft observations.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Montagud-Camps V, Hellinger P, Verdini A, Papini E, Franci L, Matteini L, Landi Set al., 2022, Quantification of the cross-helicity cascade with Karman-Howarth-Monin and Spectral transfer equations

<jats:p>&amp;lt;p&amp;gt;Spectral transfer equations allow to &amp;amp;#160;quantify the value of the energy flux of a turbulent flow across concentric shells in Fourier space. Karman-Howarth-Monin equations serve as a complement to the Spectral Transfer analysis, since they &amp;amp;#160;quantify &amp;amp;#160;as well the energy transfer rate of turbulence across scales via third-order structure functions, but also provide information on the directionality of the flux. We have extended the use of these methods to study the cascade of cross-helicity and compare it to the energy cascade &amp;amp;#160;in 3D compressible MHD simulations. Our results show that the cross-helicity cascade reaches stationarity after the energy cascade, thus indicating a slower turbulence development for this invariant. Once fully developed, the cross-helicity cascade matches the main features of the energy one.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Pisa D, Soucek J, Santolik O, Hanzelka M, Maksimovic M, Vecchio A, Khotyaintsev Y, Chust T, Kretzschmar M, Matteini L, Horbury Tet al., 2022, Observations of the Time Domain Sampler receiver from the Radio and Plasma Wave instrument during the Solar Orbiter Earth flyby&amp;#160;

<jats:p>&amp;lt;p&amp;gt;On November 27, 2021, Solar Orbiter completed its only flyby of Earth on its way to the following Sun&amp;amp;#8217;s encounter in March 2022. Although this fast flyby was performed primarily to decrease the spacecraft&amp;amp;#8217;s velocity and change orbit to get closer to the Sun, the Radio and Plasma Wave (RPW) instrument had the opportunity to perform high cadence measurements in the Earth&amp;amp;#8217;s magnetosphere. We review the main observation of the Time Domain Sampler (TDS) receiver, a part of the RPW instrument, made during this flyby at frequencies below 200 kHz. The TDS receiver operated in a high cadence mode providing us with the regular waveform snapshot with 62 ms length every ten seconds for two electric components. Besides the regular captures, we have got more than five hundred onboard classified snapshots and the statistical products with a sixteen-second cadence. Before entering the terrestrial magnetosphere around 02:30UT, the spacecraft wandered through the foreshock region, registering intense bursts of Langmuir waves. After the bowshock crossing, Solar Orbiter was for more than two hours in the morning sector of the magnetosphere, recording various plasma wave modes. The closest approach was reached at 04:30UT above North Africa at an altitude of 460 km. Then the spacecraft continued into the Earth&amp;amp;#8217;s tail and entered the magnetosheath around 13:00UT. After 15:00UT, the Solar Orbiter crossed the bowshock, and bursts of Langmuir waves were detected again pointing out to the deep downstream foreshock region. Further from the Earth, intense Auroral Kilometric Radiation (AKR) at frequencies above 100 kHz was also detected.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Laker R, Horbury T, Matteini L, Woolley T, Stawarz J, Bale Set al., 2022, On the Deflections of Switchbacks

<jats:p>&amp;lt;p&amp;gt;Following their presence during Parker Solar Probe&amp;amp;#8217;s (PSP) first encounter, switchbacks have become an active area of research with several proposed mechanisms for their formation. Many of these theories have testable predictions, although it is not trivial to compare simulation results with in-situ data from PSP. For example, there is some debate regarding the deflection direction of switchbacks, with some theories predicting a consistent magnetic deflection in the +T direction in the RTN coordinate system. Such arguments are largely focussed on the first two PSP encounters, as these are the most studied encounters in the literature. We examine the deflection direction of switchbacks for the first eight PSP encounters, with the aim to clear up any ambiguity regarding this property of switchbacks. Much like the earlier results of Horbury et al. 2020 (during the first encounter) we find that switchbacks tend to deflect in the same direction for hours at a time. Although there is some consistency in deflection direction within an individual encounter, crucially we find that there is no preferred deflection direction across all the encounters. We speculate about the cause of these results and what implications they may have for switchback formation theories.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Woolley T, Matteini L, Horbury TS, Bale SD, Laker R, Woodham LD, Stawarz JEet al., 2022, Linking In-situ Magnetic and Density Structures in the Low Latitude Slow Solar Wind to Solar Origins

<jats:p>&amp;lt;p&amp;gt;To date, Parker Solar Probe has completed ten solar encounters and measured a wealth of in-situ data down to heliocentric distances of ~13 solar radii. This data provides a novel opportunity to investigate the near-Sun environment and understand the young slow solar wind. Typically, the slow solar wind observed in the inner heliosphere is split into an Alfvenic and a non-Alfvenic component. The Alfvenic slow wind is thought to originate from overexpanded coronal hole field lines, whereas the non-Alfvenic slow wind could originate from active regions, transient events, or reconnection at the tips of helmet streamers. In this work, we find structures associated with non-Alfvenic slow wind in the low latitude wind measured by Parker Solar Probe. We identify at least two distinct types of structure using magnetic field magnitude, electron pitch angle distributions, and electron number density. After statistically analysing these structures, with a focus on their plasma properties, shape, and location with respect to the heliospheric current sheet, we link them to solar origins. We find structures that are consistent with the plasma blobs seen previously in remote sensing observations.&amp;lt;/p&amp;gt;</jats:p>

Journal article

Maksimovic M, Soucek J, Chust T, Khotyaintsev Y, Kretzschmar M, Bonnin X, Vecchio A, Alexandrova O, Bale SD, Berard D, Brochot J-Y, Edberg NJT, Eriksson A, Hadid LZ, Johansson EPG, Karlsson T, Katra B, Krasnoselskikh V, Krupar V, Lion S, Lorfevre E, Matteini L, Nguyen QN, Pisa D, Piberne R, Plettemeier D, Rucker HO, Santolik O, Steinvall K, Steller M, Stverak S, Travnicek P, Vaivads A, Zaslavsky A, Chaintreuil S, Dekkali M, Astier P-A, Barbary G, Boughedada K, Cecconi B, Chapron F, Collin C, Dias D, Gueguen L, Lamy L, Leray V, Malac-Allain LR, Pantellini F, Parisot J, Plasson P, Thijs S, Fratter I, Bellouard E, Danto P, Julien S, Guilhem E, Fiachetti C, Sanisidro J, Laffaye C, Gonzalez F, Pontet B, Queruel N, Jannet G, Fergeau P, de Wit TD, Vincent T, Agrapart C, Pragout J, Bergerard-Timofeeva M, Delory GT, Turin P, Jeandet A, Leroy P, Pellion J-C, Bouzid V, Recart W, Kolmasova I, Kruparova O, Uhlir L, Lan R, Base J, Andre M, Bylander L, Cripps V, Cully C, Jansson S-E, Puccio W, Brinek J, Ottacher H, Angelini V, Berthomier M, Evans V, Goetz K, Hellinger P, Horbury TS, Issautier K, Kontar E, Le Contel O, Louarn P, Martinovic M, Mueller D, O'Brien H, Owen CJ, Retino A, Rodriguez-Pacheco J, Sahraoui F, Sanchez L, Walsh AP, Wimmer-Schweingruber RF, Zouganelis Iet al., 2021, First observations and performance of the RPW instrument on board the Solar Orbiter mission, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361

Journal article

D'Amicis R, Bruno R, Panasenco O, Telloni D, Perrone D, Marcucci MF, Woodham L, Velli M, De Marco R, Jagarlamudi V, Coco I, Owen C, Louarn P, Livi S, Horbury T, Andre N, Angelini V, Evans V, Fedorov A, Genot V, Lavraud B, Matteini L, Muller D, O'Brien H, Pezzi O, Rouillard AP, Sorriso-Valvo L, Tenerani A, Verscharen D, Zouganelis Iet 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

Journal article

Bale SD, Horbury TS, Velli M, Desai MI, Halekas JS, McManus MD, Panasenco O, Badman ST, Bowen TA, Chandran BDG, Drake JF, Kasper JC, Laker R, Mallet A, Matteini L, Phan TD, Raouafi NE, Squire J, Woodham LD, Woolley Tet al., 2021, A solar source of alfvenic magnetic field switchbacks: in situ remnants of magnetic funnels on supergranulation scales, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 923, Pages: 1-12, ISSN: 0004-637X

One of the striking observations from the Parker Solar Probe (PSP) spacecraft is the prevalence in the inner heliosphere of large amplitude, Alfvénic magnetic field reversals termed switchbacks. These $\delta {B}_{R}/B\sim { \mathcal O }(1$) fluctuations occur over a range of timescales and in patches separated by intervals of quiet, radial magnetic field. We use measurements from PSP to demonstrate that patches of switchbacks are localized within the extensions of plasma structures originating at the base of the corona. These structures are characterized by an increase in alpha particle abundance, Mach number, plasma β and pressure, and by depletions in the magnetic field magnitude and electron temperature. These intervals are in pressure balance, implying stationary spatial structure, and the field depressions are consistent with overexpanded flux tubes. The structures are asymmetric in Carrington longitude with a steeper leading edge and a small (∼1°) edge of hotter plasma and enhanced magnetic field fluctuations. Some structures contain suprathermal ions to ∼85 keV that we argue are the energetic tail of the solar wind alpha population. The structures are separated in longitude by angular scales associated with supergranulation. This suggests that these switchbacks originate near the leading edge of the diverging magnetic field funnels associated with the network magnetic field—the primary wind sources. We propose an origin of the magnetic field switchbacks, hot plasma and suprathermals, alpha particles in interchange reconnection events just above the solar transition region and our measurements represent the extended regions of a turbulent outflow exhaust.

Journal article

Matteini L, Laker R, Horbury T, Woodham L, Bale SD, Stawarz JE, Woolley T, Steinvall K, Jones GH, Grant SR, Afghan Q, Galand M, O'Brien H, Evans V, Angelini V, Maksimovic M, Chust T, Khotyaintsev Y, Krasnoselskikh V, Kretzschmar M, Lorfevre E, Plettemeier D, Soucek J, Steller M, Stverak S, Travnicek P, Vaivads A, Vecchio A, Wimmer-Schweingruber RF, Ho GC, Gomez-Herrero R, Rodriguez-Pacheco J, Louarn P, Fedorov A, Owen CJ, Bruno R, Livi S, Zouganelis I, Muller Det al., 2021, Solar Orbiter's encounter with the tail of comet C/2019 Y4 (ATLAS): Magnetic field draping and cometary pick-up ion waves, Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361

ontext. Solar Orbiter is expected to have flown close to the tail of comet C/2019 Y4 (ATLAS) during the spacecraft’s first perihelion in June 2020. Models predict a possible crossing of the comet tails by the spacecraft at a distance from the Sun of approximately 0.5 AU.Aims. This study is aimed at identifying possible signatures of the interaction of the solar wind plasma with material released by comet ATLAS, including the detection of draped magnetic field as well as the presence of cometary pick-up ions and of ion-scale waves excited by associated instabilities. This encounter provides us with the first opportunity of addressing such dynamics in the inner Heliosphere and improving our understanding of the plasma interaction between comets and the solar wind.Methods. We analysed data from all in situ instruments on board Solar Orbiter and compared their independent measurements in order to identify and characterize the nature of structures and waves observed in the plasma when the encounter was predicted.Results. We identified a magnetic field structure observed at the start of 4 June, associated with a full magnetic reversal, a local deceleration of the flow and large plasma density, and enhanced dust and energetic ions events. The cross-comparison of all these observations support a possible cometary origin for this structure and suggests the presence of magnetic field draping around some low-field and high-density object. Inside and around this large scale structure, several ion-scale wave-forms are detected that are consistent with small-scale waves and structures generated by cometary pick-up ion instabilities.Conclusions. Solar Orbiter measurements are consistent with the crossing through a magnetic and plasma structure of cometary origin embedded in the ambient solar wind. We suggest that this corresponds to the magnetotail of one of the fragments of comet ATLAS or to a portion of the tail that was previously disconnected and advected past the spacec

Journal article

Papini E, Hellinger P, Verdini A, Landi S, Franci L, Montagud-Camps V, Matteini Let al., 2021, Properties of Hall-MHD Turbulence at Sub-Ion Scales: Spectral Transfer Analysis, ATMOSPHERE, Vol: 12

Journal article

Woolley T, Matteini L, McManus MD, Bercic L, Badman ST, Woodham LD, Horbury TS, Bale SD, Laker R, Stawarz JE, Larson DEet al., 2021, Plasma properties, switchback patches, and low alpha-particle abundance in slow Alfvenic coronal hole wind at 0.13 au, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 508, Pages: 236-244, ISSN: 0035-8711

The Parker Solar Probe (PSP) mission presents a unique opportunity to study the near-Sun solar wind closer than any previous spacecraft. During its fourth and fifth solar encounters, PSP had the same orbital trajectory, meaning that solar wind was measured at the same latitudes and radial distances. We identify two streams measured at the same heliocentric distance (∼0.13 au) and latitude (∼–3∘.5⁠) across these encounters to reduce spatial evolution effects. By comparing the plasma of each stream, we confirm that they are not dominated by variable transient events, despite PSP’s proximity to the heliospheric current sheet. Both streams are consistent with a previous slow Alfvénic solar wind study once radial effects are considered, and appear to originate at the Southern polar coronal hole boundary. We also show that the switchback properties are not distinctly different between these two streams. Low α-particle abundance (∼0.6 per cent) is observed in the encounter 5 stream, suggesting that some physical mechanism must act on coronal hole boundary wind to cause α-particle depletion. Possible explanations for our observations are discussed, but it remains unclear whether the depletion occurs during the release or the acceleration of the wind. Using a flux tube argument, we note that an α-particle abundance of ∼0.6 per cent in this low-velocity wind could correspond to an abundance of ∼0.9 per cent at 1 au. Finally, as the two streams roughly correspond to the spatial extent of a switchback patch, we suggest that patches are distinct features of coronal hole wind.

Journal article

Maksimovic M, Bale SD, Chust T, Khotyaintsev Y, Krasnoselskikh V, Kretzschmar M, Plettemeier D, Rucker HO, Soucek J, Steller M, Stverak S, Travnicek P, Vaivads A, Chaintreuil S, Dekkali M, Alexandrova O, Astier P-A, Barbary G, Berard D, Bonnin X, Boughedada K, Cecconi B, Chapron F, Chariet M, Collin C, de Conchy Y, Dias D, Gueguen L, Lamy L, Leray V, Lion S, Malac-Allain LR, Matteini L, Nguyen QN, Pantellini F, Parisot J, Plasson P, Thijs S, Vecchio A, Fratter I, Bellouard E, Lorfevre E, Danto P, Julien S, Guilhem E, Fiachetti C, Sanisidro J, Laffaye C, Gonzalez F, Pontet B, Queruel N, Jannet G, Fergeau P, Brochot J-Y, Cassam-Chenai G, Dudok de Wit T, Timofeeva M, Vincent T, Agrapart C, Delory GT, Turin P, Jeandet A, Leroy P, Pellion J-C, Bouzid V, Katra B, Piberne R, Recart W, Santolik O, Kolmasova I, Krupar V, Kruparova O, Pisa D, Uhlir L, Lan R, Base J, Ahlen L, Andre M, Bylander L, Cripps V, Cully C, Eriksson A, Jansson S-E, Johansson EPG, Karlsson T, Puccio W, Brinek J, ottacher H, Panchenko M, Berthomier M, Goetz K, Hellinger P, Horbury TS, Issautier K, Kontar E, Krucker S, Le Contel O, Louarn P, Martinovic M, Owen CJ, Retino A, Rodriguez-Pacheco J, Sahraoui F, Wimmer-Schweingruber RF, Zaslavsky A, Zouganelis Iet al., 2021, The Solar Orbiter Radio and Plasma Waves (RPW) instrument (vol 642, A12, 2020), ASTRONOMY & ASTROPHYSICS, Vol: 654, ISSN: 0004-6361

Journal article

Tenerani A, Sioulas N, Matteini L, Panasenco O, Shi C, Velli Met al., 2021, Evolution of switchbacks in the inner heliosphere, Letters of the Astrophysical Journal, Vol: 919, Pages: 1-7, ISSN: 2041-8205

We analyze magnetic field data from the first six encounters of Parker Solar Probe, three Helios fast streams and two Ulysses south polar passes covering heliocentric distances 0.1 ≲ R ≲ 3 au. We use this data set to statistically determine the evolution of switchbacks of different periods and amplitudes with distance from the Sun. We compare the radial evolution of magnetic field variances with that of the mean square amplitudes of switchbacks, and quantify the radial evolution of the cumulative counts of switchbacks per kilometer. We find that the amplitudes of switchbacks decrease faster than the overall turbulent fluctuations, in a way consistent with the radial decrease of the mean magnetic field. This could be the result of a saturation of amplitudes and may be a signature of decay processes of large amplitude Alfvénic fluctuations in the solar wind. We find that the evolution of switchback occurrence in the solar wind is scale dependent: the fraction of longer-duration switchbacks increases with radial distance, whereas it decreases for shorter switchbacks. This implies that switchback dynamics is a complex process involving both decay and in situ generation in the inner heliosphere. We confirm that switchbacks can be generated by the expansion, although other types of switchbacks generated closer to the Sun cannot be ruled out.

Journal article

Laker R, Horbury TS, Bale SD, Matteini L, Woolley T, Woodham LD, Stawarz JE, Davies EE, Eastwood JP, Owens MJ, O'Brien H, Evans V, Angelini V, Richter I, Heyner D, Owen CJ, Louarn P, Fedorov Aet al., 2021, Multi-spacecraft study of the solar wind at solar minimum: Dependence on latitude and transient outflows, Astronomy and Astrophysics: a European journal, Vol: 652, Pages: 1-10, ISSN: 0004-6361

Context. The recent launches of Parker Solar Probe, Solar Orbiter (SO), and BepiColombo, along with several older spacecraft, have provided the opportunity to study the solar wind at multiple latitudes and distances from the Sun simultaneously.Aims. We take advantage of this unique spacecraft constellation, along with low solar activity across two solar rotations between May and July 2020, to investigate how the solar wind structure, including the heliospheric current sheet (HCS), varies with latitude.Methods. We visualise the sector structure of the inner heliosphere by ballistically mapping the polarity and solar wind speed from several spacecraft onto the Sun’s source surface. We then assess the HCS morphology and orientation with the in situ data and compare this with a predicted HCS shape.Results. We resolve ripples in the HCS on scales of a few degrees in longitude and latitude, finding that the local orientations of sector boundaries were broadly consistent with the shape of the HCS but were steepened with respect to a modelled HCS at the Sun. We investigate how several CIRs varied with latitude, finding evidence for the compression region affecting slow solar wind outside the latitude extent of the faster stream. We also identified several transient structures associated with HCS crossings and speculate that one such transient may have disrupted the local HCS orientation up to five days after its passage.Conclusions. We have shown that the solar wind structure varies significantly with latitude, with this constellation providing context for solar wind measurements that would not be possible with a single spacecraft. These measurements provide an accurate representation of the solar wind within ±10° latitude, which could be used as a more rigorous constraint on solar wind models and space weather predictions. In the future, this range of latitudes will increase as SO’s orbit becomes more inclined.

Journal article

Hellinger P, Papini E, Verdini A, Landi S, Franci L, Matteini L, Montagud-Camps Vet al., 2021, Spectral Transfer and Karman-Howarth-Monin Equations for Compressible Hall Magnetohydrodynamics, ASTROPHYSICAL JOURNAL, Vol: 917, ISSN: 0004-637X

Journal article

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