The normal modes of a resonant cavity containing discrete inhomogeneities - The influence of fibril magnetic fields on the solar acoustic oscillations

1989 ◽  
Vol 342 ◽  
pp. 545 ◽  
Author(s):  
Thomas J. Bogdan ◽  
Fausto Cattaneo
Keyword(s):  
Magnetic Fields ◽  
Resonant Cavity ◽  
Normal Modes ◽  
Acoustic Oscillations ◽  
Discrete Inhomogeneities

Intraband Faraday and Voigt effects in lead telluride

1969 ◽  
Vol 47 (1) ◽  
pp. 31-37 ◽  
Author(s):  
K. K. Chandler ◽  
P. R. Wallace
Keyword(s):  
Magnetic Fields ◽  
Electromagnetic Fields ◽  
Plasma Frequency ◽  
Normal Modes ◽  
Lead Telluride ◽  
Coupled System ◽  
Major Axis ◽  
Transmitted Wave ◽  
Elliptically Polarized

The Faraday and Voigt coefficients—rotation of the axis of polarization, and the ratio of minor to major axis of the elliptically polarized transmitted wave—have been calculated at frequencies up to and beyond the intraband plasma frequency, and for magnetic fields up to 120 kG. The behavior of these coefficients is simply related to the spectrum of normal modes of the coupled system of electrons, ions, and electromagnetic fields.

Helioseismic insights into the generation and evolution of the Sun’s internal magnetic field

2019 ◽  
Vol 15 (S354) ◽  
pp. 94-106
Author(s):  
Anne-Marie Broomhall ◽  
René Kiefer
Keyword(s):  
Magnetic Fields ◽  
Meridional Circulation ◽  
Torsional Oscillation ◽  
Activity Cycle ◽  
Solar Interior ◽  
Acoustic Oscillations ◽  
Near Surface ◽  
Activity Cycles ◽  
The Impact ◽  
The Relationship

AbstractProperties of helioseismic acoustic oscillations (p modes) are modified by flows and magnetic fields in the solar interior, with frequencies, amplitudes and damping rates all varying systematically through the solar cycle. Crucially, now, we have a long enough baseline of helioseismic data to compare of the different activity cycles. We review recent efforts along these lines, from the impact of near-surface magnetic fields on p-mode frequencies to the evolution of the torsional oscillation and meridional circulation. We show that each activity cycle for which we have helioseismic data is slightly different in terms of the relationship between p mode frequencies and atmospheric proxies of activity, and in terms of the rotation and meridional circulation flows. However, many challenges remain, crucially including our ability to constrain flows and magnetic fields in the deep solar interior.

Magnetic field intermittency and fast dynamo action in random helical flows

1992 ◽  
Vol 241 ◽  
pp. 199-214 ◽  
Author(s):  
Andrew D. Gilbert ◽  
B. J. Bayly
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Growth Rates ◽  
Molecular Diffusion ◽  
Normal Modes ◽  
Magnetic Helicity ◽  
Dynamo Action ◽  
Random Flows

The evolution of passive magnetic fields is considered in random flows made up of single helical waves. In the absence of molecular diffusion the growth rates of all moments of a magnetic field are calculated analytically, and it is found that the field becomes increasingly intermittent with time. The evolution of normal modes of the ensemble-averaged field is determined; it is shown that the flows considered give fast dynamo action, and magnetic field modes with either sign of magnetic helicity may grow.

Ohmic dissipation induced by Earth's nutation

2020 ◽  
Author(s):  
Santiago Triana ◽  
Antony Trinh ◽  
Jeremy Rekier ◽  
Veronique Dehant
Keyword(s):  
Magnetic Fields ◽  
Inner Core ◽  
Normal Modes ◽  
Proof Of Concept ◽  
Ohmic Dissipation ◽  
Concept Model ◽  
The Core ◽  
Fluid Core ◽  
Radio Signals ◽  
Dynamical Treatment

<p>Radio signals from distant quasars allow us to determine Earth's rotation variations with exquisite accuracy. These observations can be used to estimate the amplitudes, frequencies and damping constants associated with Earth's rotational modes, particularly the Free Core Nutation (FCN) and the Free Inner Core Nutation (FICN). These estimates suggest, however, fluid core viscosities many orders of magnitude higher than expected, or rms magnetic fields at the core-mantle boundary (CMB) incompatible with downward continuation of the observed surface field. Aiming at resolve this difficulty, we have developed a proof-of-concept model where we incorporate an approximate fluid-dynamical treatment of the core flow associated with the FCN and the FICN. We show that, at least for the FCN, no abnormally high viscosities or magnetic fields are required. The model might provide in fact a robust, independent estimate of the rms magnetic field strength in the fluid core. Additionally, the model illustrates the importance of considering inter-mode resonances involving inertial modes (i.e. Coriolis-restored) and the rotational normal modes.</p>

scholarly journals Twisted Magnetic Fields in Conducting Fluids

1954 ◽  
Vol 7 (1) ◽  
pp. 5 ◽  
Author(s):  
JW Dungey ◽  
RE Loughhead
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Normal Modes ◽  
Loop Formation ◽  
Twisted Field ◽  
Conducting Fluids ◽  
Lines Of Force

The formation of loops in the lines of force of a twisted magnetic field confined within a cylinder of radius R, first suggested by AIfv�n (1950a), is discussed by the method of normal modes. The model first becomes unstable with respect to modes which do not lead to the formation of loops. Ignoring this, the condition obtained for loop formation is that the pitch of the twisted field be less than pR.

Sign in / Sign up

Export Citation Format

Share Document