Alfven Waves and Turbulence in the Solar Atmosphere and Solar Wind

Verdini, A.; Velli, M.

doi:10.1086/510710

Cited by 241 publications

(237 citation statements)

References 44 publications

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“…The amount of power in parallel propagating waves at 1 AU is a matter of debate [16]. Some models suggest counterpropagating waves are much more intense in the subAlfvénic corona, below 10 − 15 solar radii [35]. Our observations, however, show a very sharp dependence on δv c αp as calculated with the local value of C A .…”

Section: Figmentioning

confidence: 61%

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

et al. 2013

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Plasma carrying a spectrum of counter-propagating field-aligned ion-cyclotron waves can strongly and preferentially heat ions through a stochastic Fermi mechanism. Such a process has been proposed to explain the extreme temperatures, temperature anisotropies, and speeds of ions in the solar corona and solar wind. We quantify how differential flow between ion species results in a Doppler shift in the wave spectrum that can prevent this strong heating. Two critical values of differential flow are derived for strong heating of the core and tail of a given ion distribution function. Our comparison of these predictions to observations from the Wind spacecraft reveals excellent agreement. Solar wind helium that meets the condition for strong core heating is nearly seven times hotter than hydrogen on average. Ion-cyclotron resonance contributes to heating in the solar wind, and there is a close link between heating, differential flow, and temperature anisotropy. Introduction.-The solar corona and solar wind are so tenuous that wave-particle interactions can dominate over fluid or collisional processes, resulting in highly nonthermal plasma as seen by spacecraft in interplanetary space. Heavier ions escape from the Sun at higher speeds than the ionized hydrogen (H + ) that dominates the solar wind. Within a given solar wind stream, different species flow through one another at speeds of up to several hundred km s −1 [1,2]. This differential flow appears to be stable as long as it is aligned with the local magnetic field B and below the Alfvén wave speed C A [3,4]. Heavier ions are also often much hotter than H + , with temperatures reaching and often exceeding mass proportionality [5][6][7][8]. These non-thermal properties can be used to identify the role wave-particle interactions play in heating the corona and solar wind [9][10][11]. If we can understand the underlying physics, we will be able to predict the relative heating of ions and electrons in the solar wind, the corona and other magnetized plasmas.

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Section: Figmentioning

confidence: 61%

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

et al. 2013

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“…For example, the production of reliable chromospheric magnetograms may replace, or at least complement, the current use of photospheric magnetograms. Additionally, the incorporation of self-consistent treatments for the heating of the corona and acceleration of the solar wind (Cranmer, 2010;Rappazzo et al, 2007;Buchlin and Velli, 2007;Verdini and Velli, 2007) should provide more accurate global solutions, as well as a basic test for the physics underlying these ideas. Finally, from an observational perspective, studies of STEREO remote-sensing observations and in-situ measurements are continuing to reveal new insights into the global properties of the inner heliosphere (e.g., Riley et al, 2010a).…”

Section: Discussion and Future Directionsmentioning

confidence: 99%

Global MHD Modeling of the Solar Corona and Inner Heliosphere for the Whole Heliosphere Interval

et al. 2011

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In an effort to understand the three-dimensional structure of the solar corona and inner heliosphere during the Whole Heliosphere Interval (WHI), we have developed a global magnetohydrodynamics (MHD) solution for Carrington rotation (CR) 2068. Our model, which includes energy-transport processes, such as coronal heating, conduction of heat parallel to the magnetic field, radiative losses, and the effects of Alfvén waves, is capable of producing significantly better estimates of the plasma temperature and density in the corona than have been possible in the past. With such a model, we can compute emission in extreme ultraviolet (EUV) and X-ray wavelengths, as well as scattering in polarized white light. Additionally, from our heliospheric solutions, we can deduce magnetic-field and plasma parameters along specific spacecraft trajectories. In this paper, we present a general analysis of the large-scale structure of the solar corona and inner heliosphere during WHI, focusing, in particular, on i) helmet-streamer structure; ii) the location of the heliospheric current sheet; and iii) the geometry of corotating interaction regions. We also compare model results with i) EUV observations from the EIT instrument onboard SOHO; and ii) in-situ measurements made by the STEREO-A and B spacecraft. Finally, we contrast the global structure of the corona and inner heliosphere during WHI with its structure during the Whole Sun Month (WSM) interval. Overall, our model reproduces the essential features of the observations; however, many discrepancies are present. We discuss several likely causes for them and suggest how model predictions may be improved in the future.

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“…Note here that a different approach in literature is based on a use of the Elsässer variables (Velli 1993;Hollweg & Isenberg 2007;Verdini & Velli 2007;Verdini et al 2009). For instance, Velli (1993) used a Fourier approach, demonstrating that wave reflection is a global phenomenon.…”

Section: Physical Model Considered In This Papermentioning

confidence: 99%

“…It has been shown that Alfvén waves may become nonlinear already in the chromosphere, exerting a ponderomotive force on magnetoacoustic waves (Suzuki & Inutsuka 2005;Verdini & Velli 2007;Verdini et al 2009;Matsumoto & Shibata 2010). Numerical simulations of Alfvén waves launched from the chromosphere reveal that high-frequency modes are attenuated before they reach the corona by coupling with magnetoacoustic waves (Matsumoto & Shibata 2010).…”

Section: Introductionmentioning

confidence: 99%

Linear Alfvén waves in the solar atmosphere

Murawski¹,

Musielak²

2010

A&A

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Aims. We aim to analytically and numerically explore small-amplitude Alfvén waves in the solar atmosphere. Methods. We transform the wave equations to obtain the cutoff-frequency and wave travel time for strictly linear Alfvén waves. The wave equations are solved numerically to find out spatial and temporal signatures of the waves. Results. The analytical predictions are verified by numerically solving the wave equations for linear Alfvén waves. The waves are impulsively generated and their characteristics and behavior in the solar atmosphere are investigated by the numerical simulations. The derived cutoff-frequency is used to determine regions in the solar atmosphere where strong reflection occurs for Alfvén waves of different frequencies. Conclusions. The numerical results reveal that impulsively generated small-amplitude waves exhibit characteristic spatial and temporal signatures which agree with the predictions of the analytical theory.

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Alfven Waves and Turbulence in the Solar Atmosphere and Solar Wind

Cited by 241 publications

References 44 publications

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

Global MHD Modeling of the Solar Corona and Inner Heliosphere for the Whole Heliosphere Interval

Linear Alfvén waves in the solar atmosphere

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