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The New England Narrative
Though equally successful, noteworthy, inspiring, and crucial as the contributions to American Independence made by New England women patriots, the contributions made by North Carolinian women patriots are excluded from the history of America’s founding as a direct result of sectional nationalism
Tidal inertial waves in the differentially rotating convective envelopes of low-mass stars - I. Free oscillation modes
Star-planet tidal interactions may result in the excitation of inertial waves
in the convective region of stars. In low-mass stars, their dissipation plays a
prominent role in the long-term orbital evolution of short-period planets.
Turbulent convection can sustain differential rotation in their envelope, with
an equatorial acceleration (as in the Sun) or deceleration, which can modify
the waves' propagation properties. We explore in this first paper the general
propagation properties of free linear inertial waves in a differentially
rotating homogeneous fluid inside a spherical shell. We assume that the angular
velocity background flow depends on the latitudinal coordinate only, close to
what is expected in the external convective envelope of low-mass stars. We use
i) an analytical approach in the inviscid case to get the dispersion relation,
from which we compute the characteristic trajectories along which energy
propagates. This allows us to study the existence of attractor cycles and infer
the different families of inertial modes; ii) high-resolution numerical
calculations based on a spectral method for the viscous problem. We find that
modes that propagate in the whole shell (D modes) behave the same way as with
solid-body rotation. However, another family of inertial modes exists (DT
modes), which can propagate only in a restricted part of the convective zone.
Our study shows that they are less common than D modes and that the
characteristic rays and shear layers often focus towards a wedge - or
point-like attractor. More importantly, we find that for non-axisymmetric
oscillation modes, shear layers may cross a corotation resonance with a local
accumulation of kinetic energy. Their damping rate scales very differently from
what we obtain for standard D modes and we show an example where it is
independent of viscosity (Ekman number) in the astrophysical regime in which it
is small.Comment: 17 pages, 15 figures, accepted for publication in A&
Development of low cost ablative nozzles for solid propellant rocket motors, volume 1 Final report
Evaluating low cost ablative materials for use in large solid propellant rocket motor
Impact of the frequency dependence of tidal Q on the evolution of planetary systems
Context. Tidal dissipation in planets and in stars is one of the key physical
mechanisms that drive the evolution of planetary systems.
Aims. Tidal dissipation properties are intrisically linked to the internal
structure and the rheology of studied celestial bodies. The resulting
dependence of the dissipation upon the tidal frequency is strongly different in
the cases of solids and fluids.
Methods. We compute the tidal evolution of a two-body coplanar system, using
the tidal quality factor's frequency-dependencies appropriate to rocks and to
convective fluids.
Results. The ensuing orbital dynamics comes out smooth or strongly erratic,
dependent on how the tidal dissipation depends upon frequency.
Conclusions. We demonstrate the strong impact of the internal structure and
of the rheology of the central body on the orbital evolution of the tidal
perturber. A smooth frequency-dependence of the tidal dissipation renders a
smooth orbital evolution while a peaked dissipation can furnish erratic orbital
behaviour.Comment: Accepted for publication as a letter in Astronomy And Astrophysic
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