Growing drift-cyclotron modes in the hot solar atmosphere

Vranjes, Jovo; Poedts, Stefaan

doi:10.1051/0004-6361:20078682

Cited by 17 publications

(27 citation statements)

References 27 publications

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“…The analysis performed in Vranjes & Poedts (2008a) and in the previous sections, demonstrates that such a source (the density gradient) exists, and the mechanism which it implies is well known in the literature but not used or studied in the context of the solar plasma, and it is able to produce growing ICD modes on massive scales. For example, in Fig.…”

Section: Ion‐cyclotron Drift Wavementioning

confidence: 95%

“…Clearly, to have this, the equilibrium density scalelength must be very short to make the frequency of the drift part high, this because for the drift wave ω r ∼ 1/ L n . An application to solar plasma of this instability is discussed in Vranjes & Poedts (2008a). As shown in Ichimaru (1980), the ICD mode grows if the following instability condition is satisfied: Here, .…”

Section: Ion‐cyclotron Drift Wavementioning

confidence: 99%

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The universally growing mode in the solar atmosphere: coronal heating by drift waves

Vranjes¹,

Poedts²

2009

Monthly Notices of the Royal Astronomical Society

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The heating of the plasma in the solar atmosphere is discussed within both frameworks of fluid and kinetic drift wave theory. We show that the basic ingredient necessary for the heating is the presence of density gradients in the direction perpendicular to the magnetic field vector. Such density gradients are a source of free energy for the excitation of drift waves. We use only well‐established basic theory, verified experimentally in laboratory plasmas. Two mechanisms of the energy exchange and heating are shown to take place simultaneously: one due to the Landau effect in the direction parallel to the magnetic field, and another one, stochastic heating, in the perpendicular direction. The stochastic heating (i) is due to the electrostatic nature of the waves, (ii) is more effective on ions than on electrons, (iii) acts predominantly in the perpendicular direction, (iv) heats heavy ions more efficiently than lighter ions and (v) may easily provide a drift wave‐heating rate that is orders of magnitude above the value that is presently believed to be sufficient for the coronal heating, that is ≃6 × 10−5 J m−3 s−1 for active regions and ≃8 × 10−6 J m−3 s−1 for coronal holes. This heating acts naturally through well‐known effects that are, however, beyond the current standard models and theories.

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Section: Ion‐cyclotron Drift Wavementioning

confidence: 95%

Section: Ion‐cyclotron Drift Wavementioning

confidence: 99%

The universally growing mode in the solar atmosphere: coronal heating by drift waves

Vranjes¹,

Poedts²

2009

Monthly Notices of the Royal Astronomical Society

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“…However, regarding the lower limits, those short scales cannot be excluded in view of the expected small diffusion in the presence of the density gradients. It turns out (Vranjes & Poedts 2008, 2009b) that for L n = 10 m and 10 5 m, the diffusion velocity takes values 10 −3 m s −1 and 10 −7 m s −1 , respectively. On the other hand, the drift-wave instability can be easily demonstrated also for L n values above the mentioned upper limit (Vranjes & Poedts 2009b).…”

Section: Growth Ratesmentioning

confidence: 97%

“…The characteristic diffusion time is in fact orders of magnitude above the drift-wave growth time. More details on that issue are available in Vranjes & Poedts (2008, 2009b.…”

Section: Basic Equationsmentioning

confidence: 99%

Kinetic Instability of Drift-Alfvén Waves in Solar Corona and Stochastic Heating

Vranjes

Poedts

2010

ApJ

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The solar atmosphere is structured and inhomogeneous, both horizontally and vertically. The omnipresence of coronal magnetic loops implies gradients of the equilibrium plasma quantities such as the density, magnetic field, and temperature. These gradients are responsible for the excitation of drift waves that grow both within the twocomponent fluid description (both in the presence of collisions and without it) and within the two-component kinetic descriptions (due to purely kinetic effects). In this work, the effects of the density gradient in the direction perpendicular to the magnetic field vector are investigated within the kinetic theory, in both electrostatic (ES) and electromagnetic (EM) regimes. The EM regime implies the coupling of the gradient-driven drift wave with the Alfvén wave. The growth rates for the two cases are calculated and compared. It is found that, in general, the ES regime is characterized by stronger growth rates, as compared with the EM perturbations. Also discussed is the stochastic heating associated with the drift wave. The released amount of energy density due to this heating should be more dependent on the magnitude of the background magnetic field than on the coupling of the drift and Alfvén waves. The stochastic heating is expected to be much higher in regions with a stronger magnetic field. On the whole, the energy release rate caused by the stochastic heating can be several orders of magnitude above the value presently accepted as necessary for a sustainable coronal heating. The vertical stratification and the very long wavelengths along the magnetic loops imply that a drift-Alfvén wave, propagating as a twisted structure along the loop, in fact occupies regions with different plasma-β and, therefore, may have different (EM-ES) properties, resulting in different heating rates within just one or two wavelengths.

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“…Clearly, the observable characteristic dimensions of the density irregularities are limited by the presently available spatial resolutions of the current instruments (presently a fraction of an arcsecond). However, even extremely short, meter-size scales cannot be excluded, especially in the solar corona (Vranjes & Poedts 2008); hence, the density inhomogeneity scale lengths may have any values from the meter size up to thousands of kilometers in the case of coronal plumes.…”

Section: Introductionmentioning

confidence: 99%

Diamagnetic current does not produce an instability in the solar corona

Vranjes

Poedts

2009

A&A

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Context. The solar atmosphere contains density irregularities of various sizes embedded in magnetic fields. In the case of a density gradient perpendicular to the magnetic field vector, the plasma supports drift waves that are usually growing as a result of the free energy stored in the density gradient. Aims. Some basic features of the drift wave are discussed here and, in particular, the gyro-viscosity stress tensor effects and the properties of the diamagnetic drift. Also, the recently proposed "new" instability due to the diamagnetic drift is checked. Methods. This analysis involves a calculation that considers some terms missing in previous calculations that have appeared in the literature.Results. It is shown that the diamagnetic drift, which is essential for the recently proposed new physical phenomenon, cannot contribute to the flux in the continuity equation. Moreover, the part of the ion polarization drift contribution to the ion flux cancels out exactly with the contribution of the part of the stress tensor drift to the same flux. Conclusions. Thus, the ion diamagnetic current does not produce an instability in the solar corona.

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Growing drift-cyclotron modes in the hot solar atmosphere

Cited by 17 publications

References 27 publications

The universally growing mode in the solar atmosphere: coronal heating by drift waves

The universally growing mode in the solar atmosphere: coronal heating by drift waves

Kinetic Instability of Drift-Alfvén Waves in Solar Corona and Stochastic Heating

Diamagnetic current does not produce an instability in the solar corona

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