Acceleration of the solar wind

Leer, Egil; Holzer, T. E.; Flå, Tor

doi:10.1007/bf00213253

Cited by 201 publications

(103 citation statements)

References 59 publications

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“…where the mass density ρ and radial flow speed u are both functions of radial distance r (see, e.g., Hammer 1982;Hansteen & Leer 1995;Leer et al 1982;Withbroe 1988;Schwadron & McComas 2003). The kinetic energy flux is not always the largest term in the energy budget of individual "parcels" of solar wind (Le Chat et al 2012) or CME (Murphy et al 2011) plasma, but it serves well to quantify the overall amount of material ejected in this form.…”

Section: Mass Loss Rates and Kinetic Energy Fluxesmentioning

confidence: 99%

Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

Cranmer

2017

ApJ

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Coronal mass ejections (CMEs) are eruptive events that cause a solar-type star to shed mass and magnetic flux. CMEs tend to occur together with flares, radio storms, and bursts of energetic particles. On the Sun, CME-related mass loss is roughly an order of magnitude less intense than that of the background solar wind. However, on other types of stars, CMEs have been proposed to carry away much more mass and energy than the time-steady wind. Earlier papers have used observed correlations between solar CMEs and flare energies, in combination with stellar flare observations, to estimate stellar CME rates. This paper sidesteps flares and attempts to calibrate a more fundamental correlation between surface-averaged magnetic fluxes and CME properties. For the Sun, there exists a power-law relationship between the magnetic filling factor and the CME kinetic energy flux, and it is generalized for use on other stars. An example prediction of the time evolution of wind/CME mass-loss rates for a solar-mass star is given. A key result is that for ages younger than about 1 Gyr (i.e., activity levels only slightly higher than the present-day Sun), the CME mass loss exceeds that of the time-steady wind. At younger ages, CMEs carry 10-100 times more mass than the wind, and such high rates may be powerful enough to dispel circumstellar disks and affect the habitability of nearby planets. The cumulative CME mass lost by the young Sun may have been as much as 1% of a solar mass.

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Section: Mass Loss Rates and Kinetic Energy Fluxesmentioning

confidence: 99%

Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

Cranmer

2017

ApJ

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“…Lowfrequency (0.001È0.1 Hz) waves dominate the power Alfve n spectrum of magnetic Ñuctuations in the solar wind for r º 0.3 AU. These waves have been demonstrated to transport a signiÐcant outward momentum to the solar wind particles via a mean wave pressure (e.g., Belcher 1971 ;Leer, Holzer, & 1982 ;Ofman & Davila 1997). However, these Flalow-frequency waves are not likely to accelerate the Alfve n heavier ions (helium and oxygen) to Ñow speeds faster than that of protons or heat the heavier ions preferentially in the perpendicular direction (T M ?…”

Section: The Temperature Ratio Between O5`ions and Protons Is Much Lamentioning

confidence: 99%

Heating and Acceleration of Protons and Minor Ions by Fast Shocks in the Solar Corona

Lee

2000

ApJ

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We propose a new mechanism of coronal heating, in which protons and minor ions are heated and accelerated by fast shocks. The interaction between network magnetic Ðelds and emerging intranetwork Ðelds may lead to the formation of thin current sheets, which triggers magnetic reconnection and microÑares. The disruption of current sheet leads to fast shocks with an Mach number In Alfve n M A \ 2. addition, fast shocks that originate in the chromosphere by magnetic reconnection of a smaller scale may produce spicules and then enter the corona. The heating and acceleration by shocks are then examined based on a theoretical model and hybrid simulations. The results show the following : (1) the near nondeÑection of ion motion across the shock ramp leads to a large perpendicular thermal velocity which (v thM ), depends on the mass/charge ratio ; (2) for subcritical shocks with the shock heating leads 1.1 ¹ M A ¹ 1.5, to a large temperature anisotropy with for O5`ions and a mild anisotropy with.2 for protons ; (3) these subcritical shocks can directly drive an outward Ðeld-aligned velocity km s~1 for protons ; (4) the large perpendicular thermal velocity of O5`ions can be D0.1V A D 240 converted to the radial outÑow velocity (u) in the diverging coronal Ðeld lines ; and (5) the heating and acceleration by shocks with can lead to km s~1 for O5`ions

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“…The dissipation of waves has been proposed for some Alfve n time as a natural possibility in the corona and wind (Alfve n 1947 ;Osterbrock 1961 ;Kuperus, Ionson, & Spicer 1981). There is no consensus, however, about the speciÐc means of energy and momentum transfer from waves to particles (see, e.g., Leer, Holzer, & 1982 ;Isenberg & Hollweg 1982 ;FlaHollweg 1986 ;Chashey 1989 ;Ofman & Davila 1997 ;Cuseri et al 1999 ;Shukla et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Ion Cyclotron Wave Dissipation in the Solar Corona: The Summed Effect of More than 2000 Ion Species

Cranmer

2000

ApJ

156

129

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In this paper the dissipation of ion cyclotron resonant waves in the extended solar corona is Alfve n examined in detail. For the Ðrst time, the wave damping arising from more than 2000 low-abundance ion species is taken into account. Useful approximations for the computation of coronal ionization equilibria for elements heavier than nickel are presented. Also, the Sobolev approximation from the theory of hot-star winds is applied to the resonant wave dissipation in the solar wind, and the surprisingly e †ective damping ability of "" minor ÏÏ ions is explained in simple terms. High-frequency (10È10,000 Hz) waves propagating up from the base of the corona are damped signiÐcantly when they resonate with ions having charge-to-mass ratios of about 0.1, and negligible wave power would then be available to resonate with higher charge-to-mass ratio ions at larger heights. This result conÐrms preliminary suggestions from earlier work that the waves that heat and accelerate the high-speed solar wind must be generated throughout the extended corona. The competition and eventual equilibrium between wave damping and wave replenishment may explain observed di †erences in coronal O VI and Mg X emission line widths.

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Acceleration of the solar wind

Cited by 201 publications

References 59 publications

Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

Heating and Acceleration of Protons and Minor Ions by Fast Shocks in the Solar Corona

Ion Cyclotron Wave Dissipation in the Solar Corona: The Summed Effect of More than 2000 Ion Species

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