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We investigate the wavevector and variance anisotropies in the inertial range of the young solar wind observed by the Parker Solar Probe (PSP). Using the first 19 encounters of PSP measurements, we identify the young solar wind from…

Solar and Stellar Astrophysics · Physics 2025-07-08 Wenshuai Cheng , Ming Xiong , Yiming Jiao , Hao Ran , Liping Yang , Huidong Hu , Rui Wang

This paper reviews the current state of our understanding of high-speed solar wind acceleration in coronal holes. Observations by SOHO, coupled with interplanetary particle measurements going back several decades, have put strong…

Astrophysics · Physics 2007-05-23 Steven R. Cranmer

In this letter we report observations of magnetic switchback (SB) features near 1 au using data from the \emph{Wind} spacecraft. These features appear to be strikingly similar to the ones observed by the Parker Solar Probe mission (PSP)…

Solar and Stellar Astrophysics · Physics 2022-06-29 S. Bourouaine , J. C. Perez , N. E. Raouafi , B. D. Chandran , S. D. Bale , M. Velli

A growing body of evidence suggests that the solar wind is powered to a large extent by an Alfv\'en-wave (AW) energy flux. AWs energize the solar wind via two mechanisms: heating and work. We use high-resolution direct numerical simulations…

Solar and Stellar Astrophysics · Physics 2021-05-05 Jean C. Perez , Benjamin D. G. Chandran , Kristopher G. Klein , Mihailo M. Martinović

Empirical solar wind speed models play an important role in enabling space weather forecasting with low computational cost. Among these, one model called WS model is based on the asymptotic expansion factor. However, it is known that it…

Solar and Stellar Astrophysics · Physics 2026-01-30 Kyogo Tokoro , Munehito Shoda , Shinsuke Imada

Parker Solar Probe measurements have recently shown that coherent fast magnetosonic and Alfv\'{e}n ion-cyclotron waves are abundant in the solar wind and can be accompanied by higher-frequency electrostatic fluctuations. In this letter we…

Solar and Stellar Astrophysics · Physics 2024-04-26 I. Y. Vasko , F. S. Mozer , T. Bowen , J. Verniero , X. An , A. V. Artemyev , J. W. Bonnell , J. Halekas , I. V. Kuzichev

The S-shaped magnetic structure in the solar wind formed by the twisting of magnetic field lines is called a switchback, whose main characteristics are the reversal of the magnetic field and the significant increase in the solar wind radial…

Solar and Stellar Astrophysics · Physics 2022-01-21 Mingming Meng , Ying D. Liu , Chong Chen , Rui Wang

The solar wind is found by Parker Solar Probe (PSP) to be abundant with Alfv\'enic velocity spikes and magnetic field kinks. Temperature enhancement is another remarkable feature associated with the Alfv\'enic spikes. How the prototype of…

Solar and Stellar Astrophysics · Physics 2023-01-11 Jiansen He , Xingyu Zhu , Liping Yang , Chuanpeng Hou , Die Duan , Lei Zhang , Ying Wang

Parker Solar Probe (PSP) is providing an unprecedented view of the Sun's corona as it progressively dips closer into the solar atmosphere with each solar encounter. Each set of observations provides a unique opportunity to test and…

Observations of plasma waves by the Fields Suite and of electrons by the Solar Wind Electrons Alphas and Protons Investigation (SWEAP) on Parker Solar Probe provide strong evidence for pitch angle scattering of strahl-energy electrons by…

{Parker Solar Probe's first solar encounter has revealed the presence of sudden magnetic field deflections that are called switchbacks and are associated with proton velocity enhancements in the slow alfv\'{e}nic solar wind.} {We study…

For the past 30+ years, the magnetic expansion factor ($f_s$) has been used in empirical relationships to predict solar wind speed ($v_{obs}$) at 1 AU, based on an inverse relationship between these two quantities. Coronal unipolar…

Solar and Stellar Astrophysics · Physics 2020-08-03 Samantha Wallace , Charles N. Arge , Nicholeen M. Viall , Ylva Pihlstrom

We employ Parker Solar Probe (PSP) observations during the latest solar minimum period (years 2018 -2021) to calibrate the version of the Wang-Sheeley-Arge (WSA) coronal model used in the European space weather forecasting tool EUHFORIA.…

Cool stars at giant and supergiant evolutionary phases present low velocity and high density winds, responsible for the observed high mass-loss rates. Although presenting high luminosities, radiation pressure on dust particles is not…

Astrophysics · Physics 2009-11-11 D. Falceta-Goncalves , A. A. Vidotto , V. Jatenco-Pereira

In this letter, we investigate the population of energetically-dominant sunward-propagating Alfv\'en waves (SAWs) using more than 20 years of data provided by the Wind spacecraft near 1 au. We refer to SAWs as energetically-dominant…

Space Physics · Physics 2025-12-23 Nickolas Giardetti , Sofiane Bourouaine , Jean C. Perez

One proposed mechanism for heating the solar wind, from close to the sun to beyond 10 AU, invokes low-frequency, oblique, Alfven-wave turbulence. Because small-scale oblique Alfven waves (kinetic Alfven waves) are compressive, the measured…

Solar and Stellar Astrophysics · Physics 2015-05-13 Benjamin D. G. Chandran , Eliot Quataert , Gregory G. Howes , Qian Xia , Peera Pongkitiwanichakul

The solar wind is typically categorized as fast and slow based on the measured speed ($v_\mathrm{sw}$). The separation between these two regimes is often set between 400 and 600 km/s without a rigorous definition. Observations of the solar…

Solar and Stellar Astrophysics · Physics 2025-02-19 B. L. Alterman , Y. J. Rivera , S. T. Lepri , R. M. Raines

The geometry of a star's Alfv\'en surface determines stellar angular momentum loss, separates a causally distinct 'corona' and stellar wind, and potentially affects exoplanetary habitability. The solar Alfv\'en surface is the only such…

Magnetic reconnection is a fundamental physical process that can drive rapid conversion of magnetic energy into plasma bulk flows, thermal heating, and particle acceleration in space and astrophysical plasmas. Classical reconnection theory…