PROPAGATING WAVES TRANSVERSE TO THE MAGNETIC FIELD IN A SOLAR PROMINENCE

AbstractWe have observed a quiescent prominence with the Hinode Solar Optical Telescope (SOT) (Ca II and Hα lines), Sacramento Peak Dunn Solar Telescope using the Universal Birefringent Filter (DST/UBF, in Hα, Hβ and Sodium-D lines), THEMIS (Télescope Héliographique pour l Etude du Magnétisme et des Instabilités Solaires/MTR (Multi Raies) spectromagnetograph (He D3), and the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) in EUV over a 4 hour period on 2012 October 10. The small fields of view of the SOT, DST, and MTR are centered on a large prominence footpoint extending towards the surface. This feature appears in the larger field of view of the AIA/304 Å filtergram as a large, quasi-vertical pillar with loops on each side. The THEMIS/MTR data indicate that the magnetic field in the pillar is essentially horizontal and the observations in the optical domain show a large number of horizontally aligned features in the pillar. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and DST data show what appear to be moving wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along quasi-vertical columns of horizontal threads in the pillar. The pulses have a velocity of propagation of about 10 km/s, a wavelength about 2000 km in the plane of the sky, and a period about 280 sec. We interpret these waves in terms of fast magnetosonic waves.

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The nature of running penumbral waves revealed

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308014658 ◽

2007 ◽

Vol 3 (S247) ◽

pp. 55-58

Author(s):

D. S. Bloomfield ◽

A. Lagg ◽

S. K. Solanki

Keyword(s):

Magnetic Field ◽

Time Series ◽

Acoustic Waves ◽

Propagation Direction ◽

Line Of Sight ◽

Slow Mode ◽

Difference Analysis ◽

Propagating Waves ◽

The Magnetic Field ◽

Phase Differences

AbstractWe seek to clarify the nature of running penumbral (RP) waves: are they chromospheric trans-sunspot waves or a visual pattern of upward-propagating waves? Full Stokes spectropolarimetric time series of the photospheric Sii10827 Å line and the chromospheric Hei10830 Å multiplet were inverted using a Milne-Eddington code. Spatial pixels were paired between the outer umbral/inner penumbral photosphere and the penumbral chromosphere using inclinations retrieved by the inversion and the dual-height pairings of line-of-sight velocity time series were studied for signatures of wave propagation using a Fourier phase difference analysis. The dispersion relation for radiatively cooling acoustic waves, modified to incorporate an inclined propagation direction, fits well the observed phase differences between the pairs of photospheric and chromospheric pixels. We have thus demonstrated that RP waves are in effect low-β slow-mode waves propagating along the magnetic field.

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A first look into the magnetic field configuration of prominence threads using spectropolarimetric data

Proceedings of the International Astronomical Union ◽

10.1017/s174392131301082x ◽

2013 ◽

Vol 8 (S300) ◽

pp. 112-116

Author(s):

D. Orozco Suárez ◽

A. Asensio Ramos ◽

J. Trujillo Bueno

Keyword(s):

Magnetic Field ◽

High Spatial Resolution ◽

Zeeman Effect ◽

Field Vector ◽

Field Configuration ◽

Magnetic Field Vector ◽

Solar Prominence ◽

Physical Processes ◽

The Magnetic Field ◽

Initial Results

AbstractWe show preliminary results of an ongoing investigation aimed at determining the configuration of the magnetic field vector in the threads of a quiescent hedgerow solar prominence using high-spatial resolution spectropolarimetric observations taken in the He I 1083.0 nm multiplet. The data consist of a two-dimensional map of a quiescent hedgerow prominence showing vertical threads. The observations were obtained with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope at the Observatorio del Teide (Spain). The He I 1083.0 nm Stokes signals are interpreted with an inversion code, which takes into account the key physical processes that generate and/or modify circular and linear polarization signals in the He I 1083.0 nm triplet: the Zeeman effect, anisotropic radiation pumping, and the Hanle effect. We present initial results of the inversions, i.e, the strength and orientation of the magnetic field vector along the prominence and in prominence threads.

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Whistler-mode polarization in a hot anisotropic plasma

Journal of Plasma Physics ◽

10.1017/s0022377800002804 ◽

1985 ◽

Vol 34 (2) ◽

pp. 213-226 ◽

Cited By ~ 11

Author(s):

S. S. Sazhin

Keyword(s):

Magnetic Field ◽

Thermal Motion ◽

Anisotropic Plasma ◽

Whistler Mode ◽

Electrostatic Waves ◽

Electric And Magnetic Fields ◽

Propagating Waves ◽

Whistler Mode Waves ◽

Electric Field Polarization ◽

The Magnetic Field

Polarization of whistler-mode waves in a hot anisotropic plasma is considered in the two limiting cases of quasi-longitudinal and quasi-electrostatic propagation. It is pointed out that electron thermal motion never influences the phase of the propagating waves; the polarization of whistler-mode waves propagating along the magnetic field is totally independent of electron thermal motion. The deformation of polarization (in both electric and magnetic fields), of obliquely propagating whistler-mode waves could be, in principle, observed in magnetospheric conditions and thus could be used to estimate electron temperature and anisotropy. This deformation seems to be especially pronounced for the electric field polarization of quasi-electrostatic waves.

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Cross-field plasma acceleration and potential formation induced by electromagnetic waves in a magnetized plasma

Journal of Plasma Physics ◽

10.1017/s0022377801001234 ◽

2001 ◽

Vol 66 (3) ◽

pp. 143-155 ◽

Cited By ~ 4

Author(s):

R. SUGAYA

Keyword(s):

Magnetic Field ◽

Particle Acceleration ◽

Electric Field ◽

Electromagnetic Waves ◽

Collisionless Plasma ◽

Magnetized Plasma ◽

Propagating Waves ◽

Potential Formation ◽

Dynamo Effect ◽

The Magnetic Field

A single-particle theory is developed to investigate particle acceleration along and across a magnetic field and the generation of an electric field transverse to the magnetic field induced by electromagnetic waves in a magnetized plasma. The almost perpendicularly propagating waves accelerate particles via their Landau and cyclotron damping, and the ratio of parallel and perpendicular drift velocities vs∥/vd can be proved to be proportional to k∥/k⊥. Simultaneously, an intense cross-field electric field E0 = B0×vd/c is generated via the dynamo effect owing to perpendicular particle acceleration to satisfy the generalized Ohm’s law. This means that this cross-field particle drift in a collisionless plasma is identical to E×B drift. It is verified that the transport equations obtained are exactly equivalent to those derived from the θ-dependent quasilinear velocity-space diffusion equation obtained from the Vlasov–Maxwell equations.

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Inferring physical parameters in solar prominence threads

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834406 ◽

2019 ◽

Vol 622 ◽

pp. A88 ◽

Cited By ~ 1

Author(s):

M. Montes-Solís ◽

I. Arregui

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Model Comparison ◽

Resonant Absorption ◽

Physical Parameters ◽

Solar Prominence ◽

Period Ratio ◽

Types Of Information ◽

The Magnetic Field

Context. High resolution observations have permitted the resolution of solar prominences/filaments into sets of threads/fibrils. However, the values of the physical parameters of these threads and their structuring remain poorly constrained. Aims. We use prominence seismology techniques to analyse transverse oscillations in threads by comparing magnetohydrodynamic (MHD) models and observations. Methods. We applied Bayesian methods to obtain two different types of information. We first inferred the marginal posterior distribution of physical parameters such as the magnetic field strength or length of the thread, when a totally filled tube, partially filled tube, and three damping models are considered as certain; the three damping models are resonant absorption in the Alfvén continuum, resonant absorption in the slow continuum, and Cowling’s diffusion. Then, we compared the relative plausibility between alternative MHD models by computing the Bayes factors. Results. Well-constrained probability density distributions can be obtained for the magnetic field strength, length of the thread, density contrast, and parameters associated with the damping models. In a comparison of the damping models of resonant absorption in the Alfvén continuum, resonant absorption in the slow continuum, and Cowling’s diffusion due to partial ionisation of prominence plasma, the resonant absorption in the Alfvén continuum is the most plausible mechanism to explain the existing observations. Relations between periods of fundamental and first overtone kink modes with values around 1 are better explained by expressions of the period ratio in the long thread approximation, while the rest of the values are more probable in the short thread limit for the period ratio. Conclusions. Our results show that Bayesian analysis offers valuable methods to perform parameter inference and a model comparison in the context of prominence seismology.

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Attenuation of non-adiabatic oscillations in a cartesian prominence fibril

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308014841 ◽

2007 ◽

Vol 3 (S247) ◽

pp. 173-177 ◽

Cited By ~ 1

Author(s):

R. Soler ◽

R. Oliver ◽

J. L. Ballester

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Thermal Conduction ◽

Finite Width ◽

Solar Prominence ◽

Radiation Losses ◽

Fine Structures ◽

The Magnetic Field

AbstractOne of the typical features shown by observations of solar prominence oscillations is that they are quickly damped in time by one or several not well-known mechanisms. In addition, recent high resolution observations have revealed that the prominence fine structures, called fibrils, can oscillate with their own periods, independently from the rest of the prominence. The main aim of the present work is to study the attenuation of oscillations supported by a single prominence fibril. We consider an equilibrium made of a prominence plasma Cartesian slab of finite width embedded in a coronal medium, and assume non-adiabatic effects (thermal conduction, radiation losses and heating) as damping mechanisms. The magnetic field is taken uniform and parallel to the slab axis. We find that the efficiency of the non-adiabatic effects as damping mechanisms is different for each magnetoacoustic mode. The obtained values of the damping time are compatible with those observed in the case of the slow modes, but the fast modes are much less attenuated.

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The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He i 10 830 Å triplet

Astronomy and Astrophysics ◽

10.1051/0004-6361/201322903 ◽

2014 ◽

Vol 566 ◽

pp. A46 ◽

Cited By ~ 38

Author(s):

D. Orozco Suárez ◽

A. Asensio Ramos ◽

J. Trujillo Bueno

Keyword(s):

Magnetic Field ◽

Field Configuration ◽

Solar Prominence ◽

Magnetic Field Configuration ◽

The Magnetic Field

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Inference of magnetic field strength and density from damped transverse coronal waves

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834324 ◽

2019 ◽

Vol 625 ◽

pp. A35

Author(s):

I. Arregui ◽

M. Montes-Solís ◽

A. Asensio Ramos

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

A Priori ◽

Resonant Absorption ◽

Density Contrast ◽

Minimal Impact ◽

Propagating Waves ◽

Transverse Inhomogeneity ◽

The Magnetic Field

A classic application of coronal seismology uses transverse oscillations of waveguides to obtain estimates of the magnetic field strength. The procedure requires information on the density of the structures. Often it ignores the damping of the oscillations. We computed marginal posteriors for parameters such as the waveguide density, the density contrast, the transverse inhomogeneity length scale, and the magnetic field strength under the assumption that the oscillations can be modelled as standing magnetohydrodynamic (MHD) kink modes damped by resonant absorption. Our results show that the magnetic field strength can be properly inferred, even if the densities inside and outside the structure are largely unknown. Incorporating observational estimates of plasma density further constrains the obtained posteriors. The amount of information that is included a priori for the density and the density contrast influences their corresponding posteriors, but very little the inferred magnetic field strength. The decision to include or leave out the information on the damping and the damping timescales has a minimal impact on the obtained magnetic field strength. In contrast to the classic method, which provides numerical estimates with error bars or possible ranges of variation for the magnetic field strength, Bayesian methods offer the full distribution of plausibility over the considered range of possible values. The methods applied to available datasets of observed transverse loop oscillations can be extended to prominence fine structures or chromospheric spicules, and implemented to propagating waves in addition to standing oscillations.

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