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Four decades have gone by since the discovery that the solar wind at 1 AU seems to exist in two relatively distinct states: slow and fast. There is still no universal agreement concerning the primary physical cause of this apparently…

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

The properties of the solar wind measured in-situ in the heliosphere are largely controlled by energy deposition in the solar. Previous studies have shown that long duration and large scale magnetic structures show an inverse relation…

Solar and Stellar Astrophysics · Physics 2024-10-30 J-B. Dakeyo , A. P. Rouillard , V. Réville , P. Démoulin , M. Maksimovic , A. Chapiron , R. F. Pinto , P. Louarn

Novel results which reveal phase transition processes in the solar wind plasma during shock events are presented in this study which is the first part of a trilogy concerning the solar wind complexity. Solar wind plasma is a typical case of…

We resolve the paradox that although magnetic collimation of an isotropic solar wind results in an enhancement of its proton flux along the polar directions, several observations indicate a wind proton flux peaked at the equator. To that…

Astrophysics · Physics 2007-05-23 K. Tsinganos , S. Bogovalov

The electrons are an essential particle species in the solar wind. They often exhibit non-equilibrium features in their velocity distribution function. These include temperature anisotropies, tails (kurtosis), and reflectional asymmetries…

The evolution of the electron heat flux in the solar wind is regulated by the interplay between several effects: solar wind expansion, that can potentially drive velocity-space instabilties, turbulence and wave-particle interactions, and,…

Plasma Physics · Physics 2020-08-05 Maria Elena Innocenti , Elisabetta Boella , Anna Tenerani , Marco Velli

The acceleration of thermal solar wind protons at spherical interplanetary shocks driven by coronal mass ejections is investigated. The solar wind velocity distribution is represented using $\kappa$-functions, which are transformed in…

Space Physics · Physics 2019-08-07 P. L. Prinsloo , R. D. Strauss , J. A. le Roux

Both remote-sensing measurements using the interplanetary scintillation (IPS) technique and in situ measurements by the Ulysses spacecraft show a bimodal structure for the solar wind at solar minimum conditions. At present what makes the…

Solar and Stellar Astrophysics · Physics 2015-05-27 Bo Li , Li-Dong Xia , Yao Chen

The solar corona is a complex system, with nonisothermal plasma and being in the self-gravitating field of the Sun. So the corona plasma is not only a nonequilibrium system but also a nonextensive one. We estimate the parameter of…

Astrophysics · Physics 2015-09-09 Jiulin Du , Yeli Song

The impulsive phase of a solar flare is known to generate strong turbulence and to transfer magnetic energy into accelerated electrons. Recognizing the importance of angular diffusion on the dynamics of the accelerated electrons, we extend…

Solar and Stellar Astrophysics · Physics 2026-03-30 A. Gordon Emslie , Eduard P. Kontar

The formation of the observed core-halo feature in the solar wind electron velocity distribution function is a long-time puzzle. In this letter based on the current knowledge of nanoflares we show that the nanoflare-accelerated electron…

Solar and Stellar Astrophysics · Physics 2015-06-23 H. Che , M. Goldstein

The analysis of energy balance of coronal holes gives that to accelerate the fast solar wind streams the energy flux of the order of 800 erg/cm$^2$ s is needed. Axford and McKenzie suggested that the energy source, necessary to accelerate…

Plasma Physics · Physics 2007-05-23 Andrei Sadovski

The physical processes that heat the solar corona and accelerate the solar wind remain unknown after many years of study. Some have suggested that the wind is driven by waves and turbulence in open magnetic flux tubes, and others have…

Solar and Stellar Astrophysics · Physics 2015-05-19 Steven R. Cranmer , Adriaan A. van Ballegooijen

Particle velocity distributions measured in the weakly collisional solar wind are frequently found to be non-Maxwellian, but how these non-Maxwellian distributions impact the physics of plasma turbulence in the solar wind remains…

Space Physics · Physics 2015-03-16 Kristopher G. Klein , Gregory G. Howes

The solar wind is connected to the Sun's atmosphere by flux tubes that are rooted in an ever-changing pattern of positive and negative magnetic polarities on the surface. Observations indicate that the magnetic field is filamentary and…

Solar and Stellar Astrophysics · Physics 2015-06-15 Steven R. Cranmer , Adriaan A. van Ballegooijen , Lauren N. Woolsey

Solar flare electron acceleration is an efficient process, but its properties (mechanism, location) are not well constrained. Via hard X-ray (HXR) emission, we routinely observe energetic electrons at the Sun, and sometimes we detect…

Solar and Stellar Astrophysics · Physics 2023-10-09 Ross Pallister , Natasha L. S. Jeffrey

The solar-wind energy flux measured near the ecliptic is known to be independent of the solar-wind speed. Using plasma data from Helios, Ulysses, and Wind covering a large range of latitudes and time, we show that the solar-wind energy flux…

Solar and Stellar Astrophysics · Physics 2015-06-04 G. Le Chat , K. Issautier , N. Meyer-Vernet

We present a versatile family of model galactic outflows including non-uniform mass and energy source distributions, a gravitational potential from an extended mass source, and radiative losses. The model easily produces steady-state wind…

Astrophysics of Galaxies · Physics 2016-03-16 Chad Bustard , Ellen G. Zweibel , Elena D'Onghia

X-ray observations are a direct diagnostic of fast electrons produced in solar flares, energized during the energy release process and directed towards the Sun. Since the properties of accelerated electrons can be substantially changed…

Solar and Stellar Astrophysics · Physics 2015-10-28 Natasha Jeffrey , Eduard Kontar , Gordon Emslie , Nicolas Bian

A variety of nonthermal characteristics like kinetic, e.g., temperature, anisotropies and suprathermal populations (enhancing the high energy tails of the velocity distributions) are revealed by the in-situ observations in the solar wind…

Solar and Stellar Astrophysics · Physics 2016-12-06 S. M. Shaaban , M. Lazar , S. Poedts , A. Elhanbaly