Are There Alfvén Waves in the Solar Atmosphere?

Erdélyi, R.; Fedun, V.

doi:10.1126/science.1153006

Cited by 157 publications

(131 citation statements)

References 13 publications

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“…Non-thermal line narrowing / broadening due to Alfvén waves has been reported by Harrison et al (2002) / Erdélyi et al (1998), Banerjee et al (1998) and O'Shea et al (2003). Alfvén waves have possibly been observed in the corona (Okamoto et al 2007;Tomczyk et al 2007) and chromosphere (De Pontieu et al 2007;Jess et al 2009), although these claims are subject to intense discussion (Erdélyi & Fedun 2007;Van Doorsselaere et al 2008).…”

Section: Introductionmentioning

confidence: 97%

Review Article: MHD Wave Propagation Near Coronal Null Points of Magnetic Fields

McLaughlin¹,

Hood²,

Moortel³

2010

Space Sci Rev

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We present a comprehensive review of MHD wave behaviour in the neighbourhood of coronal null points: locations where the magnetic field, and hence the local Alfvén speed, is zero. The behaviour of all three MHD wave modes, i.e. the Alfvén wave and the fast and slow magnetoacoustic waves, has been investigated in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null points, for a variety of assumptions, configurations and geometries. In general, it is found that the fast magnetoacoustic wave behaviour is dictated by the Alfvén-speed profile. In a β = 0 plasma, the fast wave is focused towards the null point by a refraction effect and all the wave energy, and thus current density, accumulates close to the null point. Thus, null points will be locations for preferential heating by fast waves. Independently, the Alfvén wave is found to propagate along magnetic fieldlines and is confined to the fieldlines it is generated on. As the wave approaches the null point, it spreads out due to the diverging fieldlines. Eventually, the Alfvén wave accumulates along the separatrices (in 2D) or along the spine or fan-plane (in 3D). Hence, Alfvén wave energy will be preferentially dissipated at these locations. It is clear that the magnetic field plays a fundamental role in the propagation and properties of MHD waves in the neighbourhood of coronal null points. This topic is a fundamental plasma process and results so far have also lead to critical insights into reconnection, mode-coupling, quasi-periodic pulsations and phase-mixing.

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Section: Introductionmentioning

confidence: 97%

Review Article: MHD Wave Propagation Near Coronal Null Points of Magnetic Fields

McLaughlin¹,

Hood²,

Moortel³

2010

Space Sci Rev

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“…In addition, propagating transverse waves in thin threads of solar prominences have been observed (e.g., Lin et al 2007Lin et al , 2009) and Alfvénic waves in bright points have been reported (Jess et al 2009). The role and implications of the observed Alfvénic waves for the heating of the solar atmosphere have been discussed by, e.g., Erdélyi & Fedun (2007); De Pontieu et al (2007); McIntosh et al (2011);Cargill & De Moortel (2011).…”

Section: Introductionmentioning

confidence: 99%

“…Based on MHD wave theory, a number of works have interpreted the observed waves as propagating kink MHD waves (e.g., Erdélyi & Fedun 2007;Van Doorsselaere et al 2008;Lin et al 2009;Pascoe et al 2010Pascoe et al , 2011Terradas et al 2010;Verth et al 2010Verth et al , 2011Soler et al 2011a,b,c). Kink waves are transverse waves with mixed fast MHD and Alfvénic properties (see, e.g., Edwin & Roberts 1983;Goossens et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Soler

Andries

Goossens

2012

A&A

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Context. Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. In magnetic waveguides resonant absorption due to plasma inhomogeneity naturally transfers wave energy from large-scale motions to small-scale motions. In the cooler parts of the solar atmosphere as, e.g., the chromosphere, effects due to partial ionization may be relevant for wave dynamics and heating. Aims. We study resonant Alfvén waves in partially ionized plasmas. Methods. We use the multifluid equations in the cold plasma approximation. We investigate propagating resonant MHD waves in partially ionized flux tubes. We use approximate analytical theory based on normal modes in the thin tube and thin boundary approximations along with numerical eigenvalue computations. Results. We find that the jumps of the wave perturbations across the resonant layer are the same as in fully ionized plasmas. The damping length due to resonant absorption is inversely proportional to the frequency, while that due to ion-neutral collisions is inversely proportional to the square of the frequency. For observed frequencies in the solar atmosphere, the amplitude of MHD kink waves is more efficiently damped by resonant absorption than by ion-neutral collisions. Conclusions. Most of the energy carried by chromospheric kink waves is converted into localized azimuthal Alfvén waves that can deposit energy in the coronal medium. The dissipation of wave energy in the chromosphere due to ion-neutral collisions is only effective for high-frequency waves. The chromosphere acts as a filter for kink waves with periods shorter than 10 s.

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“…Sakurai et al 1991;Goossens et al , 2011Ballai & Erdélyi 2002). Wave propagation in twisted magnetic tubes has been investigated by Bogdan (1984), Bennett et al (1999), Erdélyi & Carter (2006), Carter & Erdélyi (2007, Erdélyi & Fedun (2007), and Terradas & Goossens (2012).…”

Section: Introductionmentioning

confidence: 99%

Standing kink oscillations of thin twisted magnetic tubes with continuous equilibrium magnetic field

Terradas

2015

A&A

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In this article we study standing kink waves in twisted magnetic tubes. We use the cold plasma and thin tube approximation. We assume that the plasma density is constant inside and outside the tube. We also assume that the magnetic twist is weak and take the ratio of the azimuthal and axial component of the magnetic field to be of the order of ratio of the tube radius and tube length. The azimuthal component of the magnetic field is proportional to the distance from the tube axis inside the tube, and inversely proportional to this distance outside the tube. Using the method of asymptotic expansions we derived the governing integral equation that determines the eigenfrequencies and eigenmodes of the tube kink oscillations. In the approximation of a very weak twist, we calculated analytically the corrections to the frequencies of the fundamental mode and first overtone of a straight magnetic tube related to the presence of twist. The analytical results are compared with the numerical results obtained using the full set of linear ideal magnetohydrodynamic equations. We also calculated the ratio of frequencies of the fist overtone and fundamental mode. We found that the magnetic twist enhances this ratio for moderate values of the density ratio, and reduces this ratio for large values of the density ratio. In general, the deviation of the frequency ratio from 2 caused by the magnetic twist is comparable to that found in simultaneous observations of the fundamental mode and first overtone of the coronal loop kink oscillations. Finally, we studied the eigenmode polarization. We found that, in a particular case of linear polarization, the polarization direction rotates along the tube.

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Are There Alfvén Waves in the Solar Atmosphere?

Cited by 157 publications

References 13 publications

Review Article: MHD Wave Propagation Near Coronal Null Points of Magnetic Fields

Review Article: MHD Wave Propagation Near Coronal Null Points of Magnetic Fields

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Standing kink oscillations of thin twisted magnetic tubes with continuous equilibrium magnetic field

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