Zonal flows and magnetic fields driven by large-amplitude Rossby-Alfvén-Khantadze waves in theE-layer ionosphere

2013 ◽  
Vol 118 (12) ◽  
pp. 7822-7833 ◽  
Author(s):  
T. D. Kaladze ◽  
W. Horton ◽  
L. Z. Kahlon ◽  
O. Pokhotelov ◽  
O. Onishchenko
Keyword(s):  
Magnetic Fields ◽  
Large Amplitude ◽  
Zonal Flows

scholarly journals 18. Stellar magnetic fields

1958 ◽  
Vol 6 ◽  
pp. 161-165
Author(s):  
Horace W. Babcock
Keyword(s):  
Magnetic Fields ◽  
Large Amplitude ◽  
Zeeman Effect ◽  
Type A ◽  
Magnetic Fluctuations ◽  
Sharp Line ◽  
Stellar Magnetic Fields ◽  
Observational Program

A report is given of a ten-year observational program directed toward the discovery and investigation of the magnetic fields of stars through the Zeeman effect in their spectra. The emphasis has been on the sharp-line stars of type A, of which ten have been found to show irregular magnetic fluctuations without reversal of polarity, ten others to fluctuate irregularly with occasional reversals of polarity, and six to show essentially periodic variations; of the latter group, four are large-amplitude reversers with periods near one week.

scholarly journals Rapid inverting of the polarization of a neutron beam using large amplitude oscillating magnetic fields

1970 ◽  
Vol 79 (1) ◽  
pp. 82-92 ◽  
Author(s):  
H. Kendrick ◽  
J.S. King ◽  
S.A. Werner ◽  
A. Arrott
Keyword(s):  
Magnetic Fields ◽  
Neutron Beam ◽  
Large Amplitude

Large-Amplitude Coherent Anomalies in Baroclinic Zonal Flows

1995 ◽  
Vol 52 (10) ◽  
pp. 1615-1629 ◽  
Author(s):  
Karl R. Helfrich ◽  
Joseph Pedlosky
Keyword(s):  
Large Amplitude ◽  
Zonal Flows

scholarly journals Cyclic fluctuations in the differential rotation of active stars

2006 ◽  
Vol 2 (14) ◽  
pp. 280-281
Author(s):  
Pascal Petit
Keyword(s):  
Magnetic Fields ◽  
Differential Rotation ◽  
Time Scale ◽  
Large Amplitude ◽  
Modeling Tools ◽  
Temporal Fluctuations ◽  
Active Stars ◽  
Stellar Magnetic Fields ◽  
The Impact ◽  
Stellar Dynamo

AbstractDifferential rotation is described in stellar dynamo models as one of the fundamental phenomena governing the amplification of magnetic fields in active stars.Using indirect imaging methods, the measurement of photospheric differential rotation is now achieved on a growing number of very active stars, a fraction of which exhibit temporal fluctuations of potentially large amplitude in their latitudinal shear, on a time-scale of a few years. I first describe the modeling tools on which such analysis is based, then discuss the implications of this observational work on our understanding of stellar dynamos and of the impact stellar magnetic fields may have on the dynamics of convective envelopes.

Waves in a time-dependent magnetized electron–positron plasma

1999 ◽  
Vol 61 (1) ◽  
pp. 135-150
Author(s):  
E. T. ROWE
Keyword(s):  
Magnetic Fields ◽  
Large Amplitude ◽  
Phase Speed ◽  
Three Solutions ◽  
Amplitude Wave ◽  
Weak Magnetic Fields ◽  
Electron Positron ◽  
The Magnetic Field ◽  
Large Amplitude Wave ◽  
Insight Into

Waves in a magnetized electron–positron plasma, supporting a large-amplitude electric field E0 of superluminal phase speed, are considered. The case of perturbations with the same phase speed as the large-amplitude wave can be treated exactly, and we restrict our attention to this case, obtaining analytical results. The exact analytical results provide insight into the effect of the magnetic field and the large-amplitude wave on the harmonic structure of the perturbations. Three solutions are found for waves polarized perpendicular to E0. Waves are amplitude-modulated for weak magnetic fields (relative to the strength of the large-amplitude wave) and frequency-modulated for strong magnetic fields. This suggests that frequency modulation may be relevant to pulsars.

Helicity generation and subcritical behaviour in rapidly rotating dynamos

2011 ◽  
Vol 688 ◽  
pp. 5-30 ◽  
Author(s):  
Binod Sreenivasan ◽  
Chris A. Jones
Keyword(s):  
Magnetic Field ◽  
Rayleigh Number ◽  
Magnetic Fields ◽  
Critical Rayleigh Number ◽  
Zonal Flow ◽  
Reynolds Stresses ◽  
Dynamo Action ◽  
Zonal Flows ◽  
Seed Field ◽  
The Magnetic Field

AbstractNumerical dynamo models based on convection-driven flow in a rapidly rotating spherical shell frequently give rise to strong, stable, dipolar magnetic fields. Dipolar dynamos can be subcritical in the sense that strong magnetic fields are sustained at a Rayleigh number lower than that required for a dynamo to grow from a small seed field. In this paper we find subcritical behaviour in dynamos in line with previous studies. We explore the action of Lorentz force in a rotating dynamo which gives rise to a strong preference for dipolar modes over quadrupolar modes, and also makes subcritical behaviour more likely to occur. The coherent structures that arise in rapidly rotating convection are affected by the magnetic field in ways which strongly increase their helicity, particularly if the magnetic field is dipolar. As helicity enhances dynamo action, an existing magnetic field can hold itself up, which leads to subcritical behaviour in the dynamo. We investigate this mechanism by means of the asymptotic small Ekman number theory of rapidly rotating magnetoconvection, and compare our results with fully nonlinear dynamo simulations. There are also other mechanisms which can promote subcritical behaviour. When Reynolds stresses are significant, zonal flows can lower the helicity and disrupt the onset of dynamo action, but an established dipole field can suppress the zonal flow, and hence boost the helicity. Subcriticality means that a slow gradual reduction in Rayleigh number can lead to a catastrophic collapse of the dynamo once a critical Rayleigh number is reached. While there is little evidence that the Earth is currently in a subcritical regime, this may have implications for the long-term evolution of the geodynamo.

scholarly journals Field–Frequency-Dependent Non-linear Rheological Behavior of Magnetorheological Grease Under Large Amplitude Oscillatory Shear

2021 ◽  
Vol 8 ◽  
Author(s):  
Huixing Wang ◽  
Tianxiao Chang ◽  
Yancheng Li ◽  
Shaoqi Li ◽  
Guang Zhang ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Large Amplitude ◽  
Three Dimensional ◽  
Viscoelastic Behavior ◽  
Shear Thickening ◽  
Oscillatory Shear ◽  
Large Amplitude Oscillatory Shear ◽  
Field Frequency ◽  
Frequency Dependent ◽  
Non Linear

This article investigates the influence of frequency on the field-dependent non-linear rheology of magnetorheological (MR) grease under large amplitude oscillatory shear (LAOS). First, the LAOS tests with different driving frequencies were conducted on MR grease at four magnetic fields, and the storage and loss moduli under the frequency of 0.1, 0.5, 1, and 5 Hz were compared to obtain an overall understanding of the frequency-dependent viscoelastic behavior of MR grease. Based on this, the three-dimensional (3D) Lissajous curves and decomposed stress curves under two typical frequencies were depicted to provide the non-linear elastic and viscous behavior. Finally, the elastic and viscous measures containing higher harmonics from Fourier transform (FT)-Chebyshev analysis were used to quantitatively interpret the influence of the frequency on the non-linear rheology of MR grease, namely, strain stiffening (softening) and shear thickening (thinning), under LAOS with different magnetic fields. It was found that, under the application of the magnetic field, the onset of the non-linear behavior of MR grease was frequency-dependent. However, when the shear strain amplitude increased in the post-yield region, the non-linear rheology of MRG-70 was not affected by the oscillatory frequency.

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