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The proton temperature anisotropy in the solar wind exhibits apparent bounds which are compatible with the theoretical constraints imposed by temperature-anisotropy driven kinetic instabilities. Recent statistical analyses based on…

Space Physics · Physics 2014-09-12 Petr Hellinger , Pavel M. Travnicek

Context. Recent studies on Kappa distribution functions invoked in space plasma applications have emphasized two alternative approaches which may assume the temperature parameter either dependent or independent of the power-index $\kappa$.…

Plasma Physics · Physics 2017-06-07 M. Lazar , V. Pierrard , S. M. Shaaban , H. Fichtner , S. Poedts

A semi-empirical, axisymmetric model of the solar minimum corona is developed by solving the equations for conservation of mass and momentum with prescribed anisotropic temperature distributions. In the high-latitude regions, the proton…

Astrophysics · Physics 2009-11-10 Alberto M. Vasquez , Adriaan A. van Ballegooijen , John C. Raymond

Aims: We develop a method for estimating the properties of stellar winds for low-mass main-sequence stars between masses of 0.4 and 1.1 solar masses at a range of distances from the star. Methods: We use 1D thermal pressure driven…

Solar and Stellar Astrophysics · Physics 2015-04-29 C. P. Johnstone , M. Güdel , T. Lüftinger , G. Toth , I. Brott

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

Where and under what conditions the transfer of energy between electromagnetic fields and particles takes place in the solar wind remains an open question. We investigate the conditions that promote the growth of kinetic instabilities…

Solar wind models predict that the mass flux carried away from the Sun in the solar wind should be extremely sensitive to the temperature in the corona, where the solar wind is accelerated. We perform a direct test of this prediction in…

Solar and Stellar Astrophysics · Physics 2021-06-02 D. Stansby , L. Berčič , L. Matteini , C. J. Owen , R. French , D. Baker , S. T. Badman

Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure-anisotropy-driven instabilities such as the…

Solar and Stellar Astrophysics · Physics 2015-06-17 Sofiane Bourouaine , Daniel Verscharen , Benjamin D. G. Chandran , Bennett A. Maruca , Justin C. Kasper

The hemispheric pattern of solar filaments is considered using newly-developed simulations of the real photospheric and 3D coronal magnetic fields over a 6-month period, on a global scale. The magnetic field direction in the simulation is…

Astrophysics · Physics 2015-05-13 A. R. Yeates , D. H. Mackay , A. A. van Ballegooijen

The physical processes in the solar corona that shape the solar wind remain an active research topic. Modeling efforts have shown that energy and plasma exchanges near the transition region plays a crucial role in modulating solar wind…

Protons in the solar corona and heliosphere exhibit anisotropic velocity distributions, violation of magnetic moment conservation, and a general lack of thermal equilibrium with the other particle species. There is no agreement about the…

Solar and Stellar Astrophysics · Physics 2015-06-19 Steven R. Cranmer

The ambient solar wind flows and fields influence the complex propagation dynamics of coronal mass ejections in the interplanetary medium and play an essential role in shaping Earth's space weather environment. A critical scientific goal in…

One of the basic properties of the solar wind, that is the high speed of the fast wind, is still not satisfactorily explained. This is mainly due to the theoretical difficulty of treating weakly collisional plasmas. The fluid approach…

Astrophysics · Physics 2009-11-11 I. Zouganelis , N. Meyer-Vernet , S. Landi , M. Maksimovic , F. Pantellini

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

We generate a model description of the solar wind based on an explicit wave-turbulence-driven heating mechanism, and constrain our model with observational data. We included an explicit coronal heating source term in the general 3D…

Solar and Stellar Astrophysics · Physics 2023-03-29 Simon Schleich , Sudeshna Boro Saikia , Udo Ziegler , Manuel Güdel , Michael Bartel

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

Estimating the temperature of the solar wind particles and their anisotropies is particularly important for understanding the origin of these deviations from thermal equilibrium as well as their effects. In the absence of energetic events…

Space Physics · Physics 2016-08-17 V. Pierrard , M. Lazar , S. Poedts , S. Stverak , M. Maksimovic , P. M. Travnicek

We expand upon our paper (Rice and Yeates, 2021) which introduced `Outflow Fields': alternatives to the widely-used potential field source surface (PFSS) extrapolations of the Sun's coronal magnetic field which take into account the effect…

Solar and Stellar Astrophysics · Physics 2026-03-24 Oliver Rice , Anthony Yeates

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