Eigenmode analysis of the ITER ICRF antenna plug and electrical solution to the grounding of the antenna

Abstract It is known that concentric eyewalls can influence tropical cyclone (TC) intensity. However, they can also influence TC track. Observations indicate that TCs with concentric eyewalls are often accompanied by wobbling of the inner eyewall, a motion that gives rise to cycloidal tracks. Currently, there is no general consensus of what might constitute the dominant triggering mechanism of these wobbles. In this paper we revisit the fundamentals. The control case constitutes a TC with symmetric concentric eyewalls embedded in a quiescent environment. Two sets of experiments are conducted: one using a two-dimensional nondivergent nonlinear model and the other using a three-dimensional nonlinear model. It is found that when the system is two-dimensional, no wobbling of the inner eyewall is triggered. On the other hand, when the third dimension is introduced, an amplifying wobble is evident. This result contradicts the previous suggestion that wobbles occur only in asymmetric concentric eyewalls. It also contradicts the suggestion that environmental wind shear can be the main trigger. Examination of the dynamics along with complementary linear eigenmode analysis revealed the triggering mechanism to be the excitation of a three-dimensional exponentially growing azimuthal wavenumber-1 instability. This instability is induced by the coupling of two baroclinic vortex Rossby waves across the moat region. Additional sensitivity analyses involving reasonable modifications to vortex shape parameters, perturbation vertical length scale, and Rossby number reveal that this instability can be systematically the most excited. The growth rates are shown to peak for perturbations characterized by realistic vertical length scales, suggesting that this mechanism can be potentially relevant to actual TCs.

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Eigenmode analysis of ballooning perturbations in the inner magnetosphere of the Earth

Annales Geophysicae ◽

10.5194/angeo-25-1391-2007 ◽

2007 ◽

Vol 25 (6) ◽

pp. 1391-1403 ◽

Cited By ~ 14

Author(s):

A. S. Parnowski

Keyword(s):

Stability Criterion ◽

Geomagnetic Field ◽

Finite Conductivity ◽

Nonlinear Structures ◽

Magnetic Hydrodynamics ◽

Longitudinal Displacement ◽

Inner Magnetosphere ◽

Transversal Displacement ◽

The Earth ◽

Eigenmode Analysis

Abstract. We analyze coupled Alfvén and slow magnetosonic eigenmodes in a dipole geomagnetic field with different ionospheric conductivities in the framework of ideal magnetic hydrodynamics (MHD) with finite pressure. We use numerical and, if possible, analytical methods to describe eigenmode frequencies, growth rates and eigenfunctions. The spectrum of Alfvén and slow magnetosonic modes is discrete and equidistant. The frequencies of the first Alfvén and slow magnetosonic eigenmodes are estimated as ~1 Hz and ~1 mHz, respectively. In the case of finite conductivity, periodic and aperiodic modes are separated and their interaction analyzed. It was shown that periodic and aperiodic perturbations can mutually transform into each other. A new flute stability criterion is derived (α~4.25), which is stricter than the Gold criterion (α=20/3). Here, as usual, α=−L/p dp/dL. For flute perturbations, the deviations of transversal displacement from a constant are calculated. An approximation for longitudinal displacement is derived. We determined the position of the main longitudinal peak, which can be responsible for nonlinear structures observed by Freja. An influence of nonlinear terms in pressure is estimated as well.

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Theoretical and phase contrast microscopic eigenmode analysis of erythrocyte flicker : amplitudes

Journal de Physique II ◽

10.1051/jp2:1992199 ◽

1992 ◽

Vol 2 (5) ◽

pp. 1273-1285 ◽

Cited By ~ 43

Author(s):

Mark A. Peterson ◽

Helmut Strey ◽

Erich Sackmann

Keyword(s):

Phase Contrast ◽

Eigenmode Analysis

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Tidal disruption event discs around supermassive black holes: disc warp and inclination evolution

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1610 ◽

2019 ◽

Vol 487 (4) ◽

pp. 4965-4984 ◽

Cited By ~ 3

Author(s):

J J Zanazzi ◽

Dong Lai

Keyword(s):

Black Hole ◽

Equatorial Plane ◽

Accretion Rate ◽

Accretion Disc ◽

Precession Frequency ◽

Tidal Disruption ◽

Eigenmode Analysis ◽

Accretion Rates ◽

Rigid Disc ◽

Disruption Event

ABSTRACT After the tidal disruption event (TDE) of a star around a supermassive black hole (SMBH), the bound stellar debris rapidly forms an accretion disc. If the accretion disc is not aligned with the spinning SMBH’s equatorial plane, the disc will be driven into Lense–Thirring precession around the SMBH’s spin axis, possibly affecting the TDE’s light curve. We carry out an eigenmode analysis of such a disc to understand how the disc’s warp structure, precession, and inclination evolution are influenced by the disc’s and SMBH’s properties. We find an oscillatory warp may develop as a result of strong non-Keplarian motion near the SMBH. The global disc precession frequency matches the Lense–Thirring precession frequency of a rigid disc around a spinning black hole within a factor of a few when the disc’s accretion rate is high, but deviates significantly at low accretion rates. Viscosity aligns the disc with the SMBH’s equatorial plane over time-scales of days to years, depending on the disc’s accretion rate, viscosity, and SMBH’s mass. We also examine the effect of fallback material on the warp evolution of TDE discs, and find that the fallback torque aligns the TDE disc with the SMBH’s equatorial plane in a few to tens of days for the parameter space investigated. Our results place constraints on models of TDE emission which rely on the changing disc orientation with respect to the line of sight to explain observations.

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