Protons and alpha particles in the expanding solar wind: Hybrid simulations

Hellinger, Petr; Trávníček, Pavel

doi:10.1002/jgra.50540

Cited by 39 publications

(34 citation statements)

References 45 publications

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“…These instabilities act locally to increase T α⊥ and decrease T α according to both theory (e.g. Verscharen et al 2013;Matteini et al 2015;Seough & Nariyuki 2016), and expanding box simulations of an electron-proton-alpha solar wind (Hellinger et al 2003;Hellinger & Trávníček 2013). In addition to temperature anisotropy instabilities there are many other proposed mechanisms that could influence the observed non-adiabatic behaviour: alpha streaming instabilities (e.g.…”

Section: Discussionmentioning

confidence: 95%

Alpha particle thermodynamics in the inner heliosphere fast solar wind

Stansby

Perrone

Matteini

et al. 2019

A&A

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Context. Plasma processes occurring in the corona and solar wind can be probed by studying the thermodynamic properties of different ion species. However, most in-situ observations of positive ions in the solar wind are taken at 1 AU, where information on their solar source properties may have been irreversibly erased. Aims. In this study we aimed to use the properties of alpha particles at heliocentric distances between 0.3 and 1 AU to study plasma processes occurring at the points of observation, and to infer processes occurring inside 0.3 AU by comparing our results to previous remote sensing observations of the plasma closer to the Sun. Methods. We reprocessed the original Helios positive ion distribution functions, isolated the alpha particle population, and computed the alpha particle number density, velocity, and magnetic field perpendicular and parallel temperatures. We then investigated the radial variation of alpha particle temperatures in fast solar wind observed between 0.3 and 1 AU. Results. Between 0.3 and 1 AU alpha particles are heated in the magnetic field perpendicular direction, and cooled in the magnetic field parallel direction. Alpha particle evolution is bounded by the alpha firehose instability threshold, which provides one possible mechanism to explain the observed parallel cooling and perpendicular heating. Closer to the Sun our observations suggest that the alpha particles undergo heating in the perpendicular direction, whilst the large magnetic field parallel temperatures observed at 0.3 AU may be due to the combined effect of double adiabatic expansion and alpha particle deceleration inside 0.3 AU.

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Section: Discussionmentioning

confidence: 95%

Alpha particle thermodynamics in the inner heliosphere fast solar wind

Stansby

Perrone

Matteini

et al. 2019

A&A

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“…Both Ulysses (Goldstein et al, ; Matteini et al, ) and Helios observations (Marsch and Livi, ) indicate a differential streaming between the proton core and beam populations. Hellinger and Travnicek (, ) have indicated that solar wind expansion leads to an increasing ratio between the differential particle velocity and the local Alfvén speed, also leading to the oblique Alfvén wave instability.…”

Section: Source Of the Alfvén Wavesmentioning

confidence: 99%

“…Matteini et al (, ) and Hellinger and Travnicek () have mentioned the possibility of local Alfvén wave generation though an oblique fire hose instability caused by the expanding solar wind. Another source of free energy for this instability is associated the differential speed between the proton core and beam (or He ++ ) distributions (Hellinger & Travnicek, , ).…”

Section: Final Commentsmentioning

confidence: 99%

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

et al. 2018

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Solar wind turbulence within high‐speed streams is reviewed from the point of view of embedded single nonlinear Alfvén wave cycles, discontinuities, magnetic decreases (MDs), and shocks. For comparison and guidance, cometary plasma turbulence is also briefly reviewed. It is demonstrated that cometary nonlinear magnetosonic waves phase‐steepen, with a right‐hand circular polarized foreshortened front and an elongated, compressive trailing edge. The former part is a form of “wave breaking” and the latter that of “period doubling.” Interplanetary nonlinear Alfvén waves, which are arc polarized, have a ~180° foreshortened front and with an elongated trailing edge. Alfvén waves have polarizations different from those of cometary magnetosonic waves, indicating that helicity is a durable feature of plasma turbulence. Interplanetary Alfvén waves are noted to be spherical waves, suggesting the possibility of additional local generation. They kinetically dissipate, forming MDs, indicating that the solar wind is partially “compressive” and static. The ~2 MeV protons can nonresonantly interact with MDs leading to rapid cross‐field (~5.5% Bohm) diffusion. The possibility of local (~1 AU) generation of Alfvén waves may make it difficult to forecast High‐Intensity, Long‐Duration AE Activity and relativistic magnetospheric electrons with great accuracy. The future Solar Orbiter and Solar Probe Plus missions should be able to not only test these ideas but to also extend our knowledge of plasma turbulence evolution.

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“…Similar ideas involving dissipative mechanisms related to interaction of Alfvén waves or KAWs and phase mixing have been examined in the context of the magnetospheric plasma sheet [ Lysak and Song , ] and in coronal loops [ Ofman and Aschwanden , ]. It has been shown that ion‐scale shear Alfvén waves can be excited by ion beams in the solar wind [ Hellinger and Trávníček , , ], and these can contribute to the formation of KAWs [ Nariyuki et al , ]. Many observations have shown that the proton distribution function in the solar wind can include a beam directed in the direction parallel to the local magnetic field [ Marsch , ; Marsch et al , ; Goodrich and Lazarus , ], with a drift speed of the order of the local Alfvén velocity [ Goldstein et al , ; Tu et al , ].…”

Section: Introductionmentioning

confidence: 98%

From Alfvén waves to kinetic Alfvén waves in an inhomogeneous equilibrium structure

et al. 2016

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Kinetic Alfvén waves are believed to primary form fluctuations in a hydromagnetic turbulence at scales of the order of the ion inertial length. We study a model where an initial Alfvén wave propagates inside an equilibrium structure which is inhomogeneous in the direction perpendicular to the equilibrium magnetic field. In a previous paper this situation has been considered in a particular configuration where the initial wave vector is parallel to the magnetic field and the wave is polarized perpendicular to the inhomogeneity direction. Here we consider other configurations, with a different polarization and possible initial oblique propagation. We employ numerical simulations, using both a Hall‐magnetohydrodynamics and a Hybrid Vlasov‐Maxwell model. Results show that in all the considered cases the time evolution leads to the formation of kinetic Alfvén waves within the inhomogeneity regions, which are identified by a comparison with analytical linear theory results. Then, in this context the formation of kinetic Alfvén waves seems to be a general phenomenon which could be also extended to more complex situations, like turbulence. Kinetic simulations show that kinetic Alfvén waves modify the ion distribution function, generating temperature anisotropy of both parallel and perpendicular to the local magnetic field as well as particle beams aligned along the local magnetic field. These results could be relevant both in the solar corona and in large‐scale structures of the solar wind, where Alfvénic fluctuations are present along with large‐scale inhomogeneities.

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Protons and alpha particles in the expanding solar wind: Hybrid simulations

Cited by 39 publications

References 45 publications

Alpha particle thermodynamics in the inner heliosphere fast solar wind

Alpha particle thermodynamics in the inner heliosphere fast solar wind

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

From Alfvén waves to kinetic Alfvén waves in an inhomogeneous equilibrium structure

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