Observations of mode coupling in the solar corona and bipolar noise storms

Solar Physics ◽  
1992 ◽  
Vol 138 (1) ◽  
pp. 163-187 ◽  
Author(s):  
S. M. White ◽  
G. Thejappa ◽  
M. R. Kundu
Keyword(s):  
Solar Corona ◽  
Mode Coupling

scholarly journals Mode Coupling in the Solar Corona. V. Reduction of the Coupled Equations

1977 ◽  
Vol 30 (6) ◽  
pp. 661 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Solar Corona ◽  
Mode Coupling ◽  
Mhd Waves ◽  
Fast Mode ◽  
Coupling Theory ◽  
Mode Coupling Theory ◽  
Coupled Equations

A simplified version of the mode-coupling theory of Clemmow and Heading is developed by reducing the set of coupled equations to two for the magnetoionic theory and three for the MHD theory. The simplified theory reproduces known results for coupling in the neighbourhood of coupling points. It is used to treat coupling between the MHD waves, and it is found that coupling between the fast mode and the Alfven mode for VA ;?; C, is stronger than the coupling between any other pair of modes. The strongest coupling of all is between the Alfven and slow (magnetoacoustic) modes for VA ~ C,.

scholarly journals Mode Coupling in the Solar Corona. IV. Magnetohydrodynamic Waves

1977 ◽  
Vol 30 (6) ◽  
pp. 647 ◽  
Author(s):  
DB Melrose ◽  
MA Simpson
Keyword(s):  
General Theory ◽  
Solar Corona ◽  
Mode Coupling ◽  
Stratified Medium ◽  
Mhd Waves ◽  
Fast Mode ◽  
Slow Mode ◽  
Magnetohydrodynamic Waves ◽  
Quartic Equation ◽  
Obliquely Incident

A general theory for coupling between MHD waves obliquely incident on a stratified medium is developed. Coupling between the Alfvtln mode and the magnetoacoustic mode (the fast mode for VA > cs and the slow mode for VA < cs) is affected little by the finiteness of Cs/VA for VA >> Cs and the coupling becomes weaker as Cs/VA is increased towards unity. Coupling between the fast and slow modes for VA ≈ C. is discussed qualitatively using solutions of the MHD counterpart of the Booker quartic equation.

scholarly journals Mode Coupling in the Solar Corona. I. Coupling Near the Plasma Level

1974 ◽  
Vol 27 (1) ◽  
pp. 31 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Plasma Level ◽  
Solar Corona ◽  
Mode Coupling ◽  
Solar Radio ◽  
Plasma Frequency ◽  
Type I ◽  
Radio Radiation ◽  
Coupling Ratio ◽  
Solar Radio Radiation ◽  
Solar Type

The theory of mode coupling in the radiation from solar type I storms is extended to treat coupling when the frequency! is near the plasma frequency!p. It is found that Cohen's coupling ratio Q = U/It)4, where It is the transition frequency (f'P It for strong coupling), is to be multiplied by a factor (1-!~/ J2)5/2 for QT regions, i.e. coupling is relatively suppressed close to the plasma level. The implications on the handedness of solar radio radiation are discussed. The possibility of depolarization due to mode coupling is considered briefly.

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.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

FeXIV Line Emission Polarization of the July 11, 1991 Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 541-547
Author(s):  
J. Sýkora ◽  
J. Rybák ◽  
P. Ambrož
Keyword(s):  
High Resolution ◽  
Solar Corona ◽  
Emission Line ◽  
Solar Eclipse ◽  
White Light ◽  
Preliminary Analysis ◽  
Line Emission ◽  
Total Solar Eclipse ◽  
Degree Of Polarization ◽  
High Resolution Images

AbstractHigh resolution images, obtained during July 11, 1991 total solar eclipse, allowed us to estimate the degree of solar corona polarization in the light of FeXIV 530.3 nm emission line and in the white light, as well. Very preliminary analysis reveals remarkable differences in the degree of polarization for both sets of data, particularly as for level of polarization and its distribution around the Sun’s limb.

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