Tidal Forcing in Icy‐Satellite Oceans Drives Mean Circulation and Ice‐Shell Torques

Tidal forces generate time‐varying currents in bodies with fluid layers, such as the icy ocean moons of the outer solar system. The expectation has been that tidal currents are periodic—they average to zero over a forcing period—so that they are not associated with a mean flow. This expectation arises from the assumption of linearity. Here, we relax this assumption and develop a theory that predicts the emergence of mean currents driven by any periodic forcing. The theory, derived in the context of a global, uniform, shallow ocean, constitutes a set of mean flow equations forced by non‐linear eddy fluctuations. The latter are the canonical, periodic tidal currents predicted by the Laplace Tidal equations. We show that the degree‐2 tide‐raising potential due to obliquity and/or orbital eccentricity can drive time‐averaged currents with zonal wavenumbers from 0 to 4. The most prominent of these is a retrograde zonal jet driven by the obliquity‐forcing potential. Assuming Cassini state obliquities, this jet has speeds ranging from 0.01 to 1 mm s−1, which can exert torques up to roughly 1015 N m at the ice–ocean interfaces of Europa, Callisto, Titan, and Triton. Depending on the viscosity of the ice shell, these torques could drive ice shell drift rates of tens to potentially hundreds of meters a year. Thinner or stably stratified global oceans can experience much faster mean currents

Powering the Galilean Satellites with Moon-Moon Tides

There is compelling evidence for subsurface water oceans among the three outer Galilean satellites, and evidence for an internal magma ocean in the innermost moon, Io. Tidal forces from Jupiter periodically deform these bodies, causing heating and deformation that, if measured, can probe their interior structures. In addition to Jupiter-raised tides, each moon also raises tides on the others. We investigate moon-moon tides for the first time in the Galilean moons, and show that they can cause significant heating through the excitation of high-frequency resonant tidal waves in their subsurface oceans. The heating occurs both in the crust and ocean, and can exceed that of other tidal sources and radiogenic decay if the ocean is inviscid enough. The resulting tidal deformation can be used to constrain subsurface ocean thickness. Our understanding of the thermal-orbital evolution and habitability of the Jovian system may be fundamentally altered as a result

The Association between Partnership Financial Integration and Risky Audit Client Portfolios

This study examines whether profit-sharing arrangements within accounting firms are associated with the riskiness of their client portfolios. Our results use unique data about the profit-sharing arrangements of the Big 8 firms during the period 1985 to 1994. We investigate whether there is a correlation between profit-sharing and risky clients. Firms consist of the financially integrated firms, i.e., those that share their profits across a large pool of partners across the country and the financially independent firms that share their profits in a small pool on a local office basis. The large-pool firms provide more incentive for partners to cooperate to audit high-risk clients than the small-pool firms. Our results show that the large-pool firms are associated with riskier client portfolios; this is indicated by a higher proportion of fees from clients that later suffer from bankruptcies. In contrast, a smaller proportion of the clients of the small-pool firms go bankrupt. Tests using financial distress as alternative measures of client risk confirm this result

Ocean tidal heating in icy satellites with solid shells

As a long-term energy source, tidal heating in subsurface oceans of icy satellites can influence their thermal, rotational, and orbital evolution, and the sustainability of oceans. We present a new theoretical treatment for tidal heating in thin subsurface oceans with overlying incompressible elastic shells of arbitrary thickness. The stabilizing effect of an overlying shell damps ocean tides, reducing tidal heating. This effect is more pronounced on Enceladus than on Europa because the effective rigidity on a small body like Enceladus is larger. For the range of likely shell and ocean thicknesses of Enceladus and Europa, the thin shell approximation of Beuthe (2016) is generally accurate to less than about 4%.The time-averaged surface distribution of ocean tidal heating is distinct from that due to dissipation in the solid shell, with higher dissipation near the equator and poles for eccentricity and obliquity forcing respectively. This can lead to unique horizontal shell thickness variations if the shell is conductive. The surface displacement driven by eccentricity and obliquity forcing can have a phase lag relative to the forcing tidal potential due to the delayed ocean response. For Europa and Enceladus, eccentricity forcing generally produces greater tidal amplitudes due to the large eccentricity values relative to the obliquity values. Despite the small obliquity values, obliquity forcing generally produces larger phase lags due to the generation of Rossby-Haurwitz waves. If Europa's shell and ocean are respectively 10 and 100 km thick, the tide amplitude and phase lag are 26.5 m and $<1$ degree for eccentricity forcing, and $<2.5$ m and $<18$ degrees for obliquity forcing. Measurement of the obliquity phase lag (e.g. by Europa Clipper) would provide a probe of ocean thicknessComment: Icarus, accepted for publicatio

First direct observation of two protons in the decay of 45^{45}Fe with a TPC

The decay of the ground-state two-proton emitter 45Fe was studied with a time-projection chamber and the emission of two protons was unambiguously identified. The total decay energy and the half-life measured in this work agree with the results from previous experiments. The present result constitutes the first direct observation of the individual protons in the two-proton decay of a long-lived ground-state emitter. In parallel, we identified for the first time directly two-proton emission from 43Cr, a known beta-delayed two-proton emitter. The technique developped in the present work opens the way to a detailed study of the mechanism of ground-state as well as beta-delayed two-proton radioactivity.Comment: 4 pages, 5 figure

Weighing the Milky Way

We describe an experiment to measure the mass of the Milky Way galaxy. The experiment is based on calculated light travel times along orthogonal directions in the Schwarzschild metric of the Galactic center. We show that the difference is proportional to the Galactic mass. We apply the result to light travel times in a 10cm Michelson type interferometer located on Earth. The mass of the Galactic center is shown to contribute 10^-6 to the flat space component of the metric. An experiment is proposed to measure the effect.Comment: 10 pages, 1 figur

Scattering length of the ground state Mg+Mg collision

We have constructed the X 1SIGMAg+ potential for the collision between two ground state Mg atoms and analyzed the effect of uncertainties in the shape of the potential on scattering properties at ultra-cold temperatures. This potential reproduces the experimental term values to 0.2 inverse cm and has a scattering length of +1.4(5) nm where the error is prodominantly due to the uncertainty in the dissociation energy and the C6 dispersion coefficient. A positive sign of the scattering length suggests that a Bose-Einstein condensate of ground state Mg atoms is stable.Comment: 15 pages, 3 figures, Submitted Phys. Rev.

International capital mobility in an era of globalisation: adding a political dimension to the 'Feldstein–Horioka Puzzle'

The debate about the scope of feasible policy-making in an era of globalisation continues to be set within the context of an assumption that national capital markets are now perfectly integrated at the international level. However, the empirical evidence on international capital mobility contradicts such an assumption. As a consequence, a significant puzzle remains. Why is it, in a world in which the observed pattern of capital flows is indicative of a far from globalised reality, that public policy continues to be constructed in line with more extreme variants of the globalisation hypothesis? I attempt to solve this puzzle by arguing that ideas about global capital market integration have an independent causal impact on political outcomes which extends beyond that which can be attributed to the extent of their actual integration