The Fe IX Line at 17.1 nm in the Radiation Spectrum of Slow Magneto-Acoustic Waves Propagating in the Solar Corona

2021 ◽  
Vol 37 (6) ◽  
pp. 300-309
Author(s):  
S. G. Mamedov ◽  
Z. F. Aliyeva ◽  
K. I. Alisheva
Keyword(s):  
Solar Corona ◽  
Acoustic Waves ◽  
Radiation Spectrum

scholarly journals Fundamental physical processes in coronae: Waves, turbulence, reconnection, and particle acceleration

2007 ◽  
Vol 3 (S247) ◽  
pp. 257-268
Author(s):  
Markus J. Aschwanden
Keyword(s):  
Particle Acceleration ◽  
Solar Corona ◽  
Acoustic Waves ◽  
Plasma Heating ◽  
High Energy ◽  
X Rays ◽  
Line Broadening ◽  
Routine Basis ◽  
Related Line ◽  
High Energy Particles

AbstractOur understanding of fundamental processes in the solar corona has been greatly progressed based on the space observations of SMM, Yohkoh, Compton GRO, SOHO, TRACE, RHESSI, and STEREO. We observe now acoustic waves, MHD oscillations, turbulence-related line broadening, magnetic configurations related to reconnection processes, and radiation from high-energy particles on a routine basis. We review a number of key observations in EUV, soft X-rays, and hard X-rays that innovated our physical understanding of the solar corona, in terms of hydrodynamics, MHD, plasma heating, and particle acceleration processes.

Ion Acoustic Waves in a Density Gradient

1976 ◽  
Vol 31 (6) ◽  
pp. 578-582 ◽  
Author(s):  
N. D'Angelo ◽  
P. Michelsen ◽  
H. L. Pécseli
Keyword(s):  
Solar Corona ◽  
Density Gradient ◽  
Acoustic Waves ◽  
Ion Acoustic Waves ◽  
Ion Acoustic ◽  
Uniform Plasma

A damping-growth transition for ion acoustic waves propagating in a non-uniform plasma (e-folding lengths for the density ln) is observed at wavelengths λc ≈ 2 π ln. The experiment, conducted in a Q-device, supports calculations performed in connection with the problem of solar corona heating

scholarly journals Plasma heating by magnetoacoustic wave propagation in the vicinity of a 2.5D magnetic null-point

2019 ◽  
Vol 623 ◽  
pp. A81 ◽  
Author(s):  
S. Sabri ◽  
S. Poedts ◽  
H. Ebadi
Keyword(s):  
Energy Transfer ◽  
Acoustic Wave ◽  
Solar Corona ◽  
Acoustic Waves ◽  
Mode Conversion ◽  
Plasma Heating ◽  
Null Point ◽  
Magnetoacoustic Waves ◽  
Magnetic Null ◽  
Magnetic Null Point

Context. Magnetohydrodynamic (MHD) waves have significant potential as a plasma heating mechanism. Finding a suitable wave dissipation mechanism is a very tough task, given the many observational constraints on the models, and this has resulted in the development of an important research community in solar physics. The magnetic field structure has an important role in the solar corona heating. Here, we investigate in detail current sheet mode generation via magnetic reconnection and mode conversion releases some of the free magnetic energy and produces heating. In addition, energy conversion is discussed completely. Moreover, nonlinear effects on density variations and, in turn, mode conversion are pursued. Aims. In order to assess the role of magnetoacoustic waves in plasma heating, we have modeled in detail a fast magneto-acoustic wave pulse near a magnetic null-point in a finite plasma-β. The behavior of the propagation and dissipation of the fast magneto-acoustic wave is investigated in the inhomogeneous magnetically structured solar corona. Particular attention is given to the dissipation of waves and coronal heating and energy transfer in the solar corona, focusing on the energy transfer resulting from the interaction of fast magneto-acoustic waves with 2.5D magnetic null-points. Methods. The shock−capturing Godunov−type PLUTO code was used to solve the ideal MHD set of equations in the context of wave-plasma energy transfer. Results. It is shown that magneto-acoustic waves could be a viable candidate to contribute significantly to the heating of the solar corona and maintain the solar corona at a temperature of a few million degrees. The temperature is not constant in the corona. Coronal heating occurs near magnetic null points. It is found that magnetic reconnection, phase mixing and mode conversion contribute to the heating. Moreover, nonlinear fast and slow magnetoacoustic waves are decoupled except in β = 1 layer.

scholarly journals Mode Coupling in the Solar Corona. III. Alfvén and Magnetoacoustic Waves

1977 ◽  
Vol 30 (4) ◽  
pp. 495 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Acoustic Waves ◽  
Mode Coupling ◽  
Stratified Medium ◽  
Magnetoacoustic Waves ◽  
Field Lines ◽  
Hydromagnetic Waves ◽  
Special Case ◽  
The Magnetic Field

Coupling between Alfven waves and fast mode waves obliquely incident on a stratified medium is treated using the method of Clemmow and Heading (1954) within the framework of the cold plasma approximation. A result due to Frisch (1964) is rederived in the special case of vertical incidence. The coupling is strongest for nearly parallel (to the magnetic field lines) propagation, and the coupling ratio may be approximated by Q = (00 /0)" where 0 is the angle between the wave vector and the magnetic field lines, while og = A/L, with A the wavelength and L the scalelength of the inhomogeneity. This result may be of significance in connection with the heating of the solar corona by the dissipation of waves generated initially as acoustic waves in the photosphere, and perhaps with the propagation of hydromagnetic waves in the interplanetary medium.

Colour Photometry of the Solar Corona of July 11, 1991

1994 ◽  
Vol 144 ◽  
pp. 597-599 ◽  
Author(s):  
I. V. Alexeyeva ◽  
N. L. Kroussanova ◽  
M. V. Streltsova
Keyword(s):  
Solar Corona ◽  
Red Emission ◽  
Coronal Structures

AbstractThe results of photometry of colour positives of the solar corona of July 11, 1991 are presented. Observations of the white corona were made without radial niters in Jojutla (Mexico). Dependences of coronal brightness on distance in the red (640 nm) and blue (420 nm) wavelength intervals are deduced for different coronal structures up to 3.0-3.5R⊙. The effect of ”reddening“ is noted. The excess of the red emission to the blue one (I640nm/I420nm) is found to be 1.20 and 1.17 at distance of 2.2R⊙for the N-E helmet streamer (P ≃ 37°) and the N-W region of low brightness (P ≃ 339°), respectively.

July 11, 1991 Eclipse Corona Photometry by the Results of Electropolarimetric and CCD-Matrix Observations

1994 ◽  
Vol 144 ◽  
pp. 567-569
Author(s):  
V. Kulidzanishvili ◽  
D. Georgobiani
Keyword(s):  
Solar Corona ◽  
Observational Data ◽  
Solar Limb ◽  
Ccd Matrix

AbstractThe observational data of July 11, 1991 eclipse solar corona obtained by both electropolarimeter (EP) and CCD-matrix were processed. Using these data, the solar corona photometry was carried out. The results of EP data are compared with the ones of CCD data. It must be noted here that the CCD data give us only characteristics of the inner corona, while the EP data show the features of both the inner and middle corona up to 4R⊙. Standard flattening indexϵis evaluated from both data. The dependence of the flattening index on the distance from the solar limb is investigated. The isophotes in Na and Ca lines are plotted. Based on these data some ideas and conclusions on the type of the solar corona are presented.

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