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The fast solar wind is a collisionless plasma permeated by plasma waves on many different scales. A plasma wave represents the natural interplay between the periodic changes of the electromagnetic field and the associated coherent motions…

Space Physics · Physics 2011-07-29 Daniel Verscharen , Eckart Marsch

This letter presents the results of an advanced parametrization of the solar wind electron temperature anisotropy and the instabilities resulting from the interplay of the (bi-)Maxwellian core and (bi-)Kappa halo populations in the slow…

Solar and Stellar Astrophysics · Physics 2017-06-07 M. Lazar , S. M. Shaaban , V. Pierrard , H. Fichtner , S. Poedts

Spacecraft observations have shown that the proton temperature in the solar wind falls off with radial distance more slowly than expected for an adiabatic prediction. Usually, previous studies have been focused on the evolution of the…

Space Physics · Physics 2018-12-19 D. Perrone , D. Stansby , T. Horbury , L. Matteini

Firehose-like instabilities (FIs) are cited in multiple astrophysical applications. Of particular interest are the kinetic manifestations in weakly-collisional or even collisionless plasmas, where these instabilities are expected to…

Solar and Stellar Astrophysics · Physics 2022-05-25 R. A. López , A. Micera , M. Lazar , S. Poedts , G. Lapenta , A. N. Zhukov , E. Boella , S. M. Shaaban

Understanding the physical processes in the solar wind and corona which actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of coherent…

It is well known that the Solar System is presently moving through a partially ionized local interstellar medium. This gives rise to a counter-flow situation requiring a consistent description of behaviour of the two fluids -- ions and…

Astrophysics · Physics 2009-11-10 H. J. Fahr , Maciej Bzowski

The Sun is moving through a warm ($\sim$6500 K) and partly ionized local interstellar cloud (LIC) with a velocity of $\sim$26 km/s. Recent measurements of the ionization of the LIC (Wolff et al., 1999) suggest that interstellar helium in…

Astrophysics · Physics 2009-11-10 Vlad Izmodenov , Yury G. Malama , George Gloeckler , Johannes Geiss

Helioseismology has provided very precise information about the solar internal sound speed and density throughout most of the solar interior. The results are generally quite close to the properties of standard solar models. Since the solar…

Astrophysics · Physics 2007-05-23 J. Christensen-Dalsgaard

The linear stability of a stratified shear flow for smooth density profiles is studied. This work focuses on the nature of the stability boundaries of flows in which both Kelvin-Helmholtz and Holmboe instabilities are present. For a fixed…

Fluid Dynamics · Physics 2009-11-11 Alexandros Alexakis

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 main goal of the paper is to explore why observations of many astrospheres (or circumstellar bubbles) show quite stable and smooth structures of astropauses - the tangential discontinuities separating the stellar and interstellar winds,…

Solar and Stellar Astrophysics · Physics 2022-12-13 S. D. Korolkov , V. V. Izmodenov

Observations of nearby molecular clouds detect "shells", which are likely caused by winds from young main sequence stars. However, the progenitors of these observed features are not well characterized and the mass-loss rates inferred from…

Astrophysics of Galaxies · Physics 2015-10-07 S. S. R. Offner , H. G. Arce

The experimental uncertainties in G between different experiments have important implications for helioseismology. We show that these uncertainties for the standard solar model lead to a range in the value of the square of the sound speed…

Astrophysics · Physics 2009-09-25 Ilidio Lopes , Joseph Silk

Observations show various jets in the solar atmosphere with significant rotational motions, which may undergo instabilities leading to heat ambient plasma. We study the Kelvin-Helmholtz (KH) instability of twisted and rotating jets caused…

Solar and Stellar Astrophysics · Physics 2015-11-11 T. V. Zaqarashvili , I. Zhelyazkov , L. Ofman

Plasma turbulence cascading from MHD to kinetic scales in the heliospheric plasma is believed to play a key role in coronal heating and fast solar wind acceleration, but the properties of the turbulence remain poorly constrained by…

Solar and Stellar Astrophysics · Physics 2026-02-03 Eduard P. Kontar , A. Gordon Emslie , Daniel L. Clarkson , Alexander Pitna

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

Determining the mechanism responsible for the plasma heating and particle acceleration is a fundamental problem in the study of the heliosphere. Due to efficient wave-particle interactions of ion-scale waves with charged particles, these…

Solar and Stellar Astrophysics · Physics 2023-07-12 Wen Liu , Jinsong Zhao , Tieyan Wang , Xiangcheng Dong , Justin C. Kasper , Stuart D. Bale , Chen Shi , Dejin Wu

We investigate the conditions under which parallel-propagating Alfv\'en/ion-cyclotron (A/IC) waves and fast-magnetosonic/whistler (FM/W) waves are driven unstable by the differential flow and temperature anisotropy of alpha particles in the…

Space Physics · Physics 2013-08-07 Daniel Verscharen , Sofiane Bourouaine , Benjamin D. G. Chandran

In the solar wind electron velocity distributions reveal two counter-moving populations which may induce electromagnetic (EM) beaming instabilities known as heat flux instabilities. Depending on plasma parameters two distinct branches of…

Solar and Stellar Astrophysics · Physics 2018-07-16 S. M. Shaaban , M. Lazar , S. Poedts

As a follow-up of a recent study, we challenge the claim that the flow of interstellar helium through the solar system has changed substantially over the last decades. We argue that only the IBEX-Lo 2009-2010 measurements are discrepant…

Solar and Stellar Astrophysics · Physics 2015-06-23 J. L. Bertaux , R. Lallement