Aún

Alazraki, Jaime; Neruda, Pablo

doi:10.2307/40125544

Cited by 21 publications

(21 citation statements)

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“…Alazraki & Couturier (1971) and Belcher (1971) inaugurated the concept of the wave-driven wind by noting that the waves exert a 'wave pressure' −∇ δB 2 /8π on the wind (in cgs units, which we shall use throughout); B is magnetic field, the prefix δ denotes a fluctuation, and the angle brackets denote a time-average. Hollweg (1973) showed how the wave energy equation could be extended to include dissipation and plasma heating.…”

Section: The Wave-driven Windmentioning

confidence: 99%

The solar wind: Our current understanding and how we got here

Hollweg

2008

J Astrophys Astron

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In the original theory for the solar wind, the electron pressure gradient was the principal accelerating force. This was soon recognized to be insufficient to drive the high-speed streams. Subsequently, the discovery of Alfvén waves in the solar wind led to a long series of models in which wave pressure provided additional acceleration, but these wavedriven models ultimately failed to explain the rapid acceleration of the fast wind close to the Sun. An alternate view was that the pressure of hot protons close to the Sun could explain the rapid acceleration, with the proton heating coming from the cyclotron resonance. SOHO has provided remarkable data which have verified some of the predictions of this view, and given impetus to ongoing studies of the ion-cyclotron resonance in the fast wind. After a historical review, we discuss the basic ideas behind current research, emphasizing the importance of particle kinetics. We conclude with some guesses as to how work might proceed in the future.

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Section: The Wave-driven Windmentioning

confidence: 99%

The solar wind: Our current understanding and how we got here

Hollweg

2008

J Astrophys Astron

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“…For instance, by employing the WKB approximation, Parker (1965) derived an expression for the pondermotive force through which the Alfvén waves may provide further acceleration to the solar wind. The wave acceleration was later incorporated in detailed numerical models by, e.g., Alazraki & Couturier (1971). It was soon realized that Alfvén waves may also heat the solar wind via dissipative processes such as the cyclotron resonance interaction between ions and high-frequency, parallel propagating waves generated by a turbulent cascade (cf.…”

Section: Introductionmentioning

confidence: 99%

Propagation of Non–Wentzel‐Kramers‐Brillouin Alfven Waves in a Multicomponent Solar Wind with Differential Ion Flow

2007

ApJ

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We investigate the propagation of dissipationless, hydromagnetic, toroidal Alfvén waves in a realistic background, low-latitude fast solar wind with differentially flowing protons and alpha particles. Symmetry about the magnetic axis is assumed. Without invoking the short-wavelength WKB approximation, we derive the equations governing the wave transport from standard five-moment equations. The Alfvénic point, where the combined poloidal Alfvén Mach number M T ¼ 1, is found to be a singular point for the wave equation, which is then numerically solved for three representative angular frequencies ! ¼ 10 À3 , 10 À4 , and 10 À5 rad s À1 , with an amplitude of 10 km s À1 imposed at the coronal base (1 R ). Between 1 R and 1 AU, the numerical solutions show substantial deviation from the WKB expectations. Even for the relatively high frequency ! ¼ 10 À3 rad s À1 , a WKB-like behavior can be seen only in regions r k10 R . For ! ¼ 10 À5 rad s À1 , the computed profiles of wave-related parameters show a spatial dependence distinct from the WKB one, the deviation being particularly pronounced in interplanetary space. In the inner corona r P 4 R , the computed ion velocity fluctuations and wave-induced acceleration exerted on protons or alpha particles are considerably smaller than their WKB counterparts. With the chosen base wave amplitude, the wave acceleration has negligible effect on the ion force balance in the corona. However, at large distances beyond the Alfvénic point, the low-frequency wave with ! ¼ 10 À5 rad s À1 can play an important role in the ion dynamics, with the net effect being to equalize the speeds of the two ion species considered.

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“…Among various types of waves, Alfvén(ic) waves have been highlighted as a reliable agent to effectively transfer the kinetic energy of convection to the corona and the solar wind via the Poynting flux (e.g., Belcher 1971;Shoda et al 2019;Sakaue & Shibata 2020;Matsumoto 2021). This is first because they are not so much affected by shock dissipation owing to their incompressible nature, unlike compressible waves, which easily steepen to form shocks as a result of the amplification of the velocity amplitude in the stratified atmosphere, and second because they do not refract, unlike fast-mode magnetohydrodynamical (MHD) waves (e.g., Matsumoto & Suzuki 2014), but do propagate along magnetic field lines (Alazraki & Couturier 1971;Bogdan et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Role of Longitudinal Waves in Alfvén-wave-driven Solar Wind

Shimizu

Shoda

Suzuki

2022

ApJ

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We revisit the role of longitudinal waves in driving the solar wind. We study how the p-mode-like vertical oscillation on the photosphere affects the properties of solar winds in the framework of Alfvén-wave-driven winds. We perform a series of one-dimensional magnetohydrodynamical numerical simulations from the photosphere to beyond several tens of solar radii. We find that the mass-loss rate drastically increases with the longitudinal-wave amplitude at the photosphere by up to a factor of ∼4, in contrast to the classical understanding that acoustic waves hardly affect the energetics of the solar wind. The addition of the longitudinal fluctuation induces longitudinal-to-transverse wave mode conversion in the chromosphere, which results in enhanced Alfvénic Poynting flux in the corona. Consequently, coronal heating is promoted to give higher coronal density by chromospheric evaporation, leading to the increased mass-loss rate. This study clearly shows the importance of longitudinal oscillation in the photosphere and mode conversion in the chromosphere in determining the basic properties of the wind from solar-like stars.

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Aún

Cited by 21 publications

References 0 publications

The solar wind: Our current understanding and how we got here

The solar wind: Our current understanding and how we got here

Propagation of Non–Wentzel‐Kramers‐Brillouin Alfven Waves in a Multicomponent Solar Wind with Differential Ion Flow

Role of Longitudinal Waves in Alfvén-wave-driven Solar Wind

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