Article
Astronomy & Astrophysics
Chong Chen, Ying D. Liu, Huidong Hu
Summary: Macro magnetic holes (MMHs) were frequently observed by the Parker Solar Probe, characterized by significant magnetic field decreases in the solar wind lasting tens of minutes. These events possibly result from brief encounters with the rippled heliospheric current sheet (HCS), showing lower magnetic field strength and enhanced plasma density inside.
ASTROPHYSICAL JOURNAL
(2021)
Article
Geosciences, Multidisciplinary
T. D. Phan, J. L. Verniero, D. Larson, B. Lavraud, J. F. Drake, M. Oieroset, J. P. Eastwood, S. D. Bale, R. Livi, J. S. Halekas, P. L. Whittlesey, A. Rahmati, D. Stansby, M. Pulupa, R. J. MacDowall, P. A. Szabo, A. Koval, M. Desai, S. A. Fuselier, M. Velli, M. Hesse, P. S. Pyakurel, K. Maheshwari, J. C. Kasper, J. M. Stevens, A. W. Case, N. E. Raouafi
Summary: This article reports the observation of reconnection exhausts in the Heliospheric Current Sheet (HCS) by the Parker Solar Probe at close proximity to the Sun. These exhausts accelerated protons and increased their energy, while also causing the leakage of separatrix field lines.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
T. D. Phan, B. Lavraud, J. S. Halekas, M. Oieroset, J. F. Drake, J. P. Eastwood, M. A. Shay, P. S. Pyakurel, S. D. Bale, D. Larson, R. Livi, P. L. Whittlesey, A. Rahmati, M. Pulupa, M. D. McManus, J. L. Verniero, J. W. Bonnell, N. A. Schwadron, M. Stevens, A. W. Case, J. C. Kasper, R. J. MacDowall, P. A. Szabo, A. Koval, K. E. Korreck, T. Dudok de Wit, D. Malaspina, K. Goetz, P. R. Harvey
Summary: During its early orbits around the Sun, Parker Solar Probe detected reconnection signatures in the heliospheric current sheet (HCS), indicating that reconnection is almost always active in this region and could produce large bulges with several solar radii in spatial dimensions. The prevalence of reconnection in the HCS near the Sun contrasts starkly with the apparent absence of reconnection in smaller, more intense current sheets encountered near perihelia. The findings suggest that large-scale dynamics play a critical role in triggering reconnection onset in the solar wind or within the coronal source of the HCS.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
V Reville, N. Fargette, A. P. Rouillard, B. Lavraud, M. Velli, A. Strugarek, S. Parenti, A. S. Brun, C. Shi, A. Kouloumvakos, N. Poirier, R. F. Pinto, P. Louarn, A. Fedorov, C. J. Owen, V Genot, T. S. Horbury, R. Laker, H. O'Brien, V Angelini, E. Fauchon-Jones, J. C. Kasper
Summary: Understanding the origin and characteristics of the highly dynamic solar wind observed by Solar Orbiter and Parker Solar Probe is the main objective of this study, focusing particularly on its vicinity to the heliospheric current sheet (HCS). By analyzing plasma data obtained from both spacecraft, it is found that the dynamic regions are permeated by flux ropes close to the HCS. These flux ropes are also present in simulations, forming at the base of the heliospheric current sheet as a result of a pressure-driven instability followed by fast tearing reconnection process. The analysis further characterizes the 3D spatial structure of the flux ropes, relating it to the network of quasi-separatrices.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Paulett C. Liewer, Angelos Vourlidas, Guillermo Stenborg, Russell A. Howard, Jiong Qiu, Paulo Penteado, Olga Panasenco, Carlos R. Braga
Summary: Parker Solar Probe (PSP) crossed the heliospheric current sheet (HCS) near the perihelion on encounters E8 and E11, enabling the Wide-field Imager for Solar Probe (WISPR) to image the streamer belt plasma in high resolution while flying through it. As PSP flies closer to the Sun, fine-scale structures are resolved within the coronal rays of the streamer belt. Near the HCS, WISPR observes a fan of rays of various sizes and brightnesses, indicating large density variations in the HCS plasma sheet transverse to the radial direction.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Chen Shi, Marco Velli, Anna Tenerani, Victor Reville, Franco Rappazzo
Summary: In this study, the effects of the heliospheric current sheet on the evolution of Alfvenic turbulence in the solar wind were investigated using MHD simulations and data analysis. The results showed a decrease in the Alfvenicity of the turbulence near the heliospheric current sheet, accompanied by an increase in magnetic energy excess. The simulations and data analysis supported each other, revealing that the weakening of the radial magnetic field and the effects of the transverse gradient in the background magnetic field were responsible for the decrease in Alfvenicity and the magnetic energy excess.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Mikhail Vokhmyanin, Nadezhda Zolotova
Summary: In this paper, the north-south asymmetry of the heliospheric current sheet (HCS) is evaluated using reconstructed interplanetary magnetic field (IMF) data. The findings suggest that the northern hemisphere dominates in the ascending phase of the solar cycle, while the southern hemisphere activity is stronger in the descending phase.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Multidisciplinary
Qiang Liu, Yan Zhao, Guoqing Zhao
Summary: This study surveyed 63 small-scale interplanetary magnetic flux ropes (SIMFRs) found within a 6-day window around the heliospheric current sheet (HCS) and found that the majority of SIMFRs were quasi-parallel to the associated HCS, with statistically shorter durations compared to cases quasi-perpendicular to the HCS. This suggests that most of these SIMFRs may be generated in the nearby HCSs.
FRONTIERS IN PHYSICS
(2021)
Article
Astronomy & Astrophysics
J. P. Eastwood, J. E. Stawarz, T. D. Phan, R. Laker, S. Robertson, L-L Zhao, G. P. Zank, B. Lavraud, M. A. Shay, V Evans, V Angelini, H. O'Brien, T. S. Horbury
Summary: This study presents new observations of a flux rope confined to a bifurcated current sheet in the solar wind, providing new insights into the hierarchy of scales on which flux ropes can form. Comparative data from Wind extend the spatial scale over which reconnection signatures have been found at solar wind current sheets. The local orientations of the current sheet at Solar Orbiter and Wind are found to be rotated relative to each other, indicating potential implications for patchy vs. continuous reconnection scenarios.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Graham Barnes, Marc L. DeRosa, Shaela I. Jones, Charles N. Arge, Carl J. Henney, Mark C. M. Cheung
Summary: The concept of surface-flux transport (SFT) is commonly used to determine the large-scale structure of the solar magnetic field and predict solar wind and coronal magnetic field. We compare predictions from two SFT models for solar wind, magnetic footpoints, and coronal magnetic null points during different phases of the solar activity cycle. The comparison reveals cycle-dependent results and differences when new active regions are present. The evolution of the surface flux is influenced by both large-scale flows and small-scale convection motions, and the differences between models are primarily due to assumptions and implementations rather than the random evolution selection.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Stefan Eriksson, Marc Swisdak, James M. Weygand, Alfred Mallet, David L. Newman, Giovanni Lapenta, Lynn B. Wilson, Drew L. Turner, Bjorn Larsen
Summary: Wind spacecraft measurements were used to analyze magnetic reconnection exhausts in the ecliptic plane of the solar wind at 1 au. The study found an exponential decay in the distribution of current sheet widths, and a linear increase in the distribution of magnetic field rotation angles. The orientations of wide exhausts were consistent with a dominant Parker-spiral magnetic field, while narrow exhausts were isotropic. These findings suggest that CS bifurcation and turbulence play a role in aligning the exhaust directions with the large-scale heliospheric current sheet.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Lea Griton, Alexis P. Rouillard, Nicolas Poirier, Karine Issautier, Michel Moncuquet, Rui F. Pinto
Summary: By analyzing in situ measurements by the Parker Solar Probe, two distinct states of the slow solar wind have been identified within 50 solar radii from the Sun. These states differ in terms of plasma beta, flux, and magnetic pressure. Magnetic connectivity established by PSP reveals a transition from a streamer to an equatorial coronal hole, with significantly different expansion rates of magnetic field lines between the two states. This leads to varying wind flux and plasma heating patterns between the streamer and the coronal hole.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
D. Arrazola, J. J. Blanco, M. A. Hidalgo
Summary: This paper presents a revised method for estimating the physical properties of the heliospheric current sheet (HCS) by including the spacecraft's trajectory and reducing the number of required fit parameters. The results show that this method provides a qualitative description of the observed magnetic field and reduces the number of free parameters compared to the original method.
ASTRONOMY & ASTROPHYSICS
(2022)
Review
Astronomy & Astrophysics
Anna Wawrzaszek, Marius Echim
Summary: This paper reviews the research progress of intermittency in solar wind plasma turbulence, revealing the variations of intermittency with radial distance and solar cycle phase through data analysis techniques. The study highlights the importance of understanding the origin of fast and slow solar wind for improving the knowledge of intermittency in the heliosphere.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2021)
Article
Astronomy & Astrophysics
Andreas Kopp, Jan Louis Raath, Horst Fichtner, Marius S. Potgieter, Stefan E. S. Ferreira, Bernd Heber
Summary: This study reviews the transport of energetic particles in the heliosphere, emphasizing the importance of gradient and curvature drifts in the propagation of cosmic rays. It also proposes a new approach to investigate solar magnetic activity cycles more closely in order to refine the description of magnetic field polarity.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Seong-Yeop Jeong, Joel B. Abraham, Daniel Verscharen, Laura Bercic, David Stansby, Georgios Nicolaou, Christopher J. Owen, Robert T. Wicks, Andrew N. Fazakerley, Jeffersson A. Agudelo Rueda, Mayur Bakrania
Summary: The study analyzes the micro-kinetic stability of the electron strahl in the solar wind and finds that the electron strahl is generally stable against the oblique FM/W instability in the inner heliosphere. The instability, if present, can only be sporadically excited and exists for short periods of time. Further numerical evaluation of individual distributions is recommended to consider uncertainties in the stability thresholds.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
Joel B. Abraham, Christopher J. Owen, Daniel Verscharen, Mayur Bakrania, David Stansby, Robert T. Wicks, Georgios Nicolaou, Phyllis L. Whittlesey, Jeffersson A. Agudelo Rueda, Seong-Yeop Jeong, Laura Bercic
Summary: We develop and apply a fitting routine to analyze solar wind electron distribution data measured by Parker Solar Probe during its first five orbits, revealing the radial evolution of electron core, halo, and strahl populations in the slow solar wind. The results show that the combined suprathermal halo and strahl populations grow from 0.13 to 0.17 au, contradicting previous observations at distances greater than 0.3 au where an increase in halo is accompanied by a decrease in strahl. Additionally, the halo is negligible at small heliocentric distances, and the fractional strahl density remains relatively constant below 0.2 au.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Seong-Yeop Jeong, Daniel Verscharen, Christian Vocks, Joel B. Abraham, Christopher J. Owen, Robert T. Wicks, Andrew N. Fazakerley, David Stansby, Laura Bercic, Georgios Nicolaou, Jeffersson A. Agudelo Rueda, Mayur Bakrania
Summary: We propose a transport theory for the kinetic evolution of solar-wind electrons in the heliosphere and provide evidence that the electron strahl is not scattered by the oblique fast-magnetosonic/whistler instability in the near-Sun environment. The study quantifies the parameters of the electron strahl and compares the results with measurements from the Parker Solar Probe.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Nikos Sioulas, Zesen Huang, Marco Velli, Rohit Chhiber, Manuel E. Cuesta, Chen Shi, William H. Matthaeus, Riddhi Bandyopadhyay, Loukas Vlahos, Trevor A. Bowen, Ramiz A. Qudsi, Stuart D. Bale, Christopher J. Owen, P. Louarn, A. Fedorov, Milan Maksimovic, Michael L. Stevens, Anthony Case, Justin Kasper, Davin Larson, Marc Pulupa, Roberto Livi
Summary: Parker Solar Probe and SolO data were used to investigate magnetic field intermittency in the solar wind. Small-scale intermittency was observed to strengthen radially, while no clear trend was observed at larger scales. Lower-order moment-based methods were considered more appropriate for examining the evolution of coherent structures. Intermittency was found to be related to plasma parameters and the angle between the magnetic field and solar wind flow.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
D. Perrone, S. Perri, R. Bruno, D. Stansby, R. D'Amicis, V. K. Jagarlamudi, R. Laker, S. Toledo-Redondo, J. E. Stawarz, D. Telloni, R. De Marco, C. J. Owen, J. M. Raines, A. Settino, B. Lavraud, M. Maksimovic, A. Vaivads, T. D. Phan, N. Fargette, P. Louarn, I. Zouganelis
Summary: This study investigates the radial evolution of solar wind plasma from coronal holes using measurements from Solar Orbiter and Parker Solar Probe. The observations reveal the radial trends of proton density, magnetic field, and proton temperature, as well as the characteristics of turbulence and coherent structures at different radial distances. This work provides valuable insights into the turbulent nature of solar wind plasma and its evolution from the Sun to the Earth.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
R. De Marco, R. Bruno, V. Krishna Jagarlamudi, R. D'Amicis, M. F. Marcucci, V. Fortunato, D. Perrone, D. Telloni, C. J. Owen, P. Louarn, A. Fedorov, S. Livi, T. Horbury
Summary: Researchers propose an alternative approach based on the statistical technique of clustering for the identification of proton core, proton beam, and alpha particles in solar wind ion measurements. The method was tested on synthetic data and applied to a time series of solar wind data, showing promising results in combination with traditional fitting algorithms for particle species identification in challenging cases.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Nikos Sioulas, Zesen Huang, Chen Shi, Marco Velli, Anna Tenerani, Trevor A. Bowen, Stuart D. Bale, Jia Huang, Loukas Vlahos, L. D. Woodham, T. S. Horbury, Thierry Dudok de Wit, Davin Larson, Justin Kasper, Christopher J. Owen, Michael L. Stevens, Anthony Case, Marc Pulupa, David M. Malaspina, J. W. Bonnell, Roberto Livi, Keith Goetz, Peter R. Harvey, Robert J. MacDowall, Milan Maksimovic, P. Louarn, A. Fedorov
Summary: Parker Solar Probe and Solar Orbiter data are used to study the radial evolution of magnetic turbulence between 0.06 ≤ R ≤ 1 au. The inertial range near the Sun is limited to a small range of scales, exhibiting a power-law exponent of α(B) = -3/2, independent of plasma parameters. As the distance increases, the inertial range gradually expands to larger scales with a steepening trend towards α(B) = -5/3. Steeper spectra in slower wind streams may be attributed to the positive correlation between solar wind speed and Alfvenicity.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Simon Opie, Daniel Verscharen, Christopher H. K. Chen, Christopher J. Owen, Philip A. Isenberg
Summary: By analyzing the solar wind observations from the Solar Orbiter mission, the interplay between background turbulent fluctuations and kinetic instabilities is investigated. It is found that the non-equilibrium conditions causing micro-instabilities are accompanied by increased variability in the magnetic field. The competition between turbulence and instabilities is shown to significantly regulate the proton-scale energetics of the solar wind.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
G. H. H. Suen, C. J. Owen, D. Verscharen, T. S. Horbury, P. Louarn, R. De Marco
Summary: This study analyzed data collected by the Solar Orbiter spacecraft and identified three instances of magnetic reconnection occurring at the trailing edge of magnetic switchbacks. The results suggest that magnetic reconnection may contribute to the erosion of switchbacks and explain the relative rarity of switchback observations at 1 au.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
D. Baker, P. Demoulin, S. L. Yardley, T. Mihailescu, L. van Driel-Gesztelyi, R. D'Amicis, D. M. Long, A. S. H. To, C. J. Owen, T. S. Horbury, D. H. Brooks, D. Perrone, R. J. French, A. W. James, M. Janvier, S. Matthews, M. Stangalini, G. Valori, P. Smith, R. Aznar Cuadrado, H. Peter, U. Schuehle, L. Harra, K. Barczynski, D. Berghmans, A. N. Zhukov, L. Rodriguez, C. Verbeeck
Summary: A narrow corridor of open magnetic field was observed, originating from a solar active region and producing a slow solar wind stream with extreme properties.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Ziqi Wu, Jiansen He, Die Duan, Xingyu Zhu, Chuanpeng Hou, Daniel Verscharen, Georgios Nicolaou, Christopher J. Owen, Andrey Fedorov, Philippe Louarn
Summary: This study focuses on ion heating mechanisms in two magnetic reconnection exhausts encountered by Solar Orbiter. Using a three-dimensional Hermite representation, the complex velocity-space structures are quantitatively investigated. Analysis of the enstrophy and Hermite spectra reveals energy conversion and transfer in phase space. The findings indicate a depletion of Hermite power at small m inside the reconnection exhaust region, accompanied by increased proton temperature and decreased enstrophy. The slopes of the 1D parallel Hermite spectra suggest the effect of phase mixing and weak collisionality in the thermalization process. The perpendicular heating is proposed to occur through perpendicular phase mixing due to finite Larmor radius effects.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Xingyu Zhu, Jiansen He, Die Duan, Daniel Verscharen, Christopher J. Owen, Andrey Fedorov, Philippe Louarn, Timothy S. Horbury
Summary: In this study, measurements from Solar Orbiter are analyzed and compared with theoretical predictions to explore the influence of proton beams on wave activity in the solar wind. It is found that the velocity distribution functions of protons can destabilize fast magnetosonic/whistler waves. The non-alignment of the velocity vectors of the core and the beam with the wave velocity is responsible for the wave growth/damping.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Nikos Sioulas, Marco Velli, Zesen Huang, Chen Shi, Trevor A. A. Bowen, B. D. G. Chandran, Ioannis Liodis, Nooshin Davis, Stuart D. D. Bale, T. S. Horbury, Thierry Dudok de Wit, Davin Larson, Michael L. L. Stevens, Justin Kasper, Christopher J. J. Owen, Anthony Case, Marc Pulupa, David M. M. Malaspina, Roberto Livi, Keith Goetz, Peter R. R. Harvey, Robert J. J. MacDowall, John W. W. Bonnell
Summary: In this study, a merged data set from Parker Solar Probe (PSP) and Solar Orbiter (SO) was analyzed to investigate the radial evolution of power and spectral index anisotropy in the wavevector space of solar wind turbulence. The results show that the anisotropic signatures of turbulence display a distinct radial evolution when considering fast and slow wind streams. The findings provide strong observational constraints for anisotropic theories of MHD turbulence in the solar wind.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Die Duan, Jiansen He, Xingyu Zhu, Rui Zhuo, Ziqi Wu, Georgios Nicolaou, Jia Huang, Daniel Verscharen, Liu Yang, Christopher J. Owen, Andrey Fedorov, Philippe Louarn, Timothy S. Horbury
Summary: The acceleration and heating of solar wind particles by magnetic reconnection are important mechanisms in space physics. The behavior of alpha particles (He-4(2+)) in solar wind magnetic reconnection is not well understood.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Stephanie L. Yardley, Christopher J. Owen, David M. Long, Deborah Baker, David H. Brooks, Vanessa Polito, Lucie M. Green, Sarah Matthews, Mathew Owens, Mike Lockwood, David Stansby, Alexander W. James, Gherardo Valori, Alessandra Giunta, Miho Janvier, Nawin Ngampoopun, Teodora Mihailescu, Andy S. H. To, Lidia van Driel-Gesztelyi, Pascal Demoulin, Raffaella D'Amicis, Ryan J. French, Gabriel H. H. Suen, Alexis P. Rouillard, Rui F. Pinto, Victor Reville, Christopher J. Watson, Andrew P. Walsh, Anik De Groof, David R. Williams, Ioannis Zouganelis, Daniel Mueller, David Berghmans, Frederic Auchere, Louise Harra, Udo Schuehle, Krysztof Barczynski, Eric Buchlin, Regina Aznar Cuadrado, Emil Kraaikamp, Sudip Mandal, Susanna Parenti, Hardi Peter, Luciano Rodriguez, Conrad Schwanitz, Phil Smith, Luca Teriaca, Cis Verbeeck, Andrei N. Zhukov, Bart De Pontieu, Tim Horbury, Sami K. Solanki, Jose Carlos del Toro Iniesta, Joachim Woch, Achim Gandorfer, Johann Hirzberger, David Orozco Suarez, Thierry Appourchaux, Daniele Calchetti, Jonas Sinjan, Fatima Kahil, Kinga Albert, Reiner Volkmer, Mats Carlsson, Andrzej Fludra, Don Hassler, Martin Caldwell, Terje Fredvik, Tim Grundy, Steve Guest, Margit Haberreiter, Sarah Leeks, Gabriel Pelouze, Joseph Plowman, Werner Schmutz, Sunil Sidher, William T. Thompson, Philippe Louarn, Andrei Federov
Summary: The Slow Wind SOOP was developed to utilize the instruments on board the Solar Orbiter mission to study the origin and formation of the slow solar wind. It successfully linked remote-sensing and in situ measurements of slow wind originating from magnetic field boundaries. Coordinated observation campaigns were conducted with Hinode and IRIS. The analysis showed that slow wind from two target regions arrived at the spacecraft with velocities between 210 and 600 km/s.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)