Strong cylindrical magnetogasdynamic shock waves in a rotating interplanetary medium

Strong cylindrical magnetogasdynamic shock waves in rotating interplanetary medium has been studied and an analytic solution for their propagation has been obtained. Using characteristic method and considering the effect of Coriolis force, we have shown that magnetic field has significant effect on the velocity of the shock wave.     

Wave propagation in rotating plasmas and influence of the Coriolis force

When assessing the influence of the Coriolis force on wave propagation in plasmas or other dielectric media, all the equations and relevant physical quantitities should be expressed in a rotating reference frame. Only then does the Coriolis force appear. However, most treatments for plasmas seem to fail in this respect because the Maxwell equations are used in their customary form, which in general is not valid in a rotating frame. A consistent approach requires the inclusion of Schiff charges and currents in the Maxwell equations. These Schiff sources are fictitious in the same way as the Coriolis force. The resulting wave equation has coefficients depending on the position and this precludes a plane wave solution, even in the slow rotation approximation where the centrifugal force may be neglected in comparison with the Coriolis force. Perturbation analysis then gives a dispersion law as if the system were not rotating. The wave electric field, however, now has a position dependent amplitude, which is not only stretched but also changed in direction compared to the previously known unperturbed or not rotating solution.     

Solar total irradiance variability from SOVA 2 on board EURECA

The rotation of the magnetic axes of sunspot groups is studied as a function of the expansion and contraction of the groups along their magnetic axes. In general, except for the extreme values of tilt-angle change, slow rates of rotation of the magnetic axes are associated with low values of expansion or contraction, and faster rotation of the magnetic axes is associated with rapid expansion or contraction. The direction of rotation of the magnetic axes is related to expansion or contraction in the sense that would be predicted by the Coriolis force. A comparison of the effect at high and low latitudes shows a difference that further supports the Coriolis force hypothesis, and an examination of the amplitude of the effect also suggests that the Coriolis force may be a factor in the tilt-angle rotation of spot groups.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation.     

Effect of Coriolis force on the shapes of rotating stars and stars in binary systems

In this paper an attempt has been made to determine the effect of Coriolis force on the shapes of Roche equipotential surfaces of rotating stars and stars in binary systems. Equations of Roche equipotential surfaces have been obtained for rotating and binary stars which take into account the effects of Coriolis force besides the centrifugal and gravitational forces. Shapes of Roche equipotentials and values of Roche limits are obtained for different values of angular velocity of rotation for rotating stars and for different values of mass ratios for the binary stars. The obtained results have been compared with the corresponding results in which the effect of Coriolis force has not been considered.     

Motion around the out-of-plane equilibrium points of the perturbed restricted three-body problem

This paper studies the motion of an infinitesimal body near the out-of-plane equilibrium points, L _6,7, in the perturbed restricted three-body problem. The problem is perturbed in the sense that the primaries of the system are oblate spheroids as well as sources of radiation and small perturbations are give to the Coriolis and centrifugal forces. It locates the positions and examines the stability of L _6,7 with a particular application to the binary system Struve 2398. It is observed that their positions are affected by the radiation, oblateness and a small perturbation in the centrifugal force, but is unaffected by that of the Coriolis force. They are also found to be unstable.     

Building the Fast Galactic Dynamo

In this paper we demonstrate the importance of cosmic rays for the dynamics of the interstellar medium. We present the first 3D-MHD numerical simulations of the Parker instability triggered by cosmic rays accelerated in randomly distributed supernova remnants. We show that in the presence of galactic rotation a net radial magnetic field is produced as a result of the cosmic ray injection and Coriolis force. This process provides a possibility of very efficient magnetic field amplification within the general frame of so called fast galactic dynamo proposed by Parker (1992).     

Sunspot velocity correlations: Are they due to Reynolds stresses or to the Coriolis force on rising flux tubes?

Observations have consistently pointed out that the longitudinal and latitudinal motions of sunspots are correlated. The magnitude of the covariance was found to increase with latitude, and its sign was found to be positive in the N-hemisphere and negative in the S-hemisphere. This correlation was believed to be due to the underlying turbulence where the sunspot flux tubes are anchored, and the covariance had the right sign and magnitude needed to explain the transfer of angular momentum toward the equator through Reynolds stresses.Here we present an alternate explanation for these sunspot velocity correlations: It is believed that the dynamo operates in a thin overshoot layer beneath the base of the convection zone, and the flux tubes generated there produce sunspots at the photosphere. By studying the dynamics of flux tubes emerging from the base of the convection zone to the photosphere, we show that these velocity correlations of sunspots could be merely a consequence of the effect of Coriolis force on rising flux tubes. The effect of the Coriolis force, as demonstrated by even a back-of-the-envelope calculation, is to push the faster rotating spots equatorward and the slower rotating spots poleward, giving rise to a correlation in their longitudinal and latitudinal velocities, which is positive in the N-hemisphere and negative in the S-hemisphere. The increase in the correlation with latitude is due to the increase in magnitude of the Coriolis force. Hence we show that these velocity correlations might have nothing to do with the Reynolds stresses of the underlying turbulence.We present analyses of observations, and show that the covariances of plages are an order of magnitude higher than the sunspot covariances. If plages and sunspots share the same origin, and if their horizontal velocity correlations are wholly due to the effect of Coriolis force on rising flux tubes, then the study of their dynamics suggests that the flux tubes that form plages should have diameters of a couple of thousand km at the base of the convection zone and remain intact until they reach the photosphere, whereas sunspots should be formed by a collection of small flux tubes (each measuring about a hundred km in diameter), that rise through the convection zone as individual elements and coalesce when they emerge through the photosphere.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation.     

The effect of Coriolis force on acceleration covariance in MHD turbulent dusty flow with rotational symmetry

In this paper we have considered MHD turbulent dusty flow of an incompressible, viscous fluid which is nearly isotropic with rotational and spatially homogeneous. The expression for acceleration covariance in the presence of Coriolis force has been derived and solution has been obtained in terms of defining scalars.     

Study on sheath formation in astroplasmas under Coriolis force and behavior of levitated dust grains forming nebulon around Moon

Pseudopotential analysis has been employed to derive a modified Sagdeev potential-like wave equation for studying the sheath formation in astroplasma problems. Complexity in process urges to derive the new findings numerically by using fourth-order Runge-Kutta method. Main emphasis has been given to investigate the role of Coriolis force on the formation and changes on coherent structures of sheath suitably thought for the configuration of astroplasma. Study determines the sheath thickness and potential variation with the interaction of Coriolis force and thereby finds dynamical behavior of levitated dust grains into the evaluated sheath region. This leads to find the dust size, and corresponding forces generated on dust grain with a view to relate theoretical observations to real astrophysical phenomena and could be of interest to explain formation of dust clouds in spaces. To support the observations, we some thoughtful numeric plasma parameters for the case of Earth’s Moon, have taken for graphical presentations. Overall observations expect the study could be of interest as an advanced knowledge in rotating astroplasmas, and expecting many salient features which are yet to be known.     

The effect of coriolis force on acceleration covariance in turbulent dusty flow with rotational symmetry

In this paper considering the turbulent dusty flow of an incompressible viscous fluid which is nearly isotropic and spatially homogeneous with an extra vector argument (rotation symmetry) the expression for acceleration covariance in the presence of the Coriolis force has been derived and solution has been obtained in terms of defining scalars.     

The effect of coriolis force on acceleration covariance in turbulent flow with rotational symmetry

In the present paper, we have considered turbulent flow of an incompressible, viscous fluid which is nearly isotropic with an extra vector argument (i.e. rotational symmetry) and spatially homogeneous. The expression for acceleration covariance in presence of Coriolis force has been derived and solution has been obtained in terms of defining scalars.     

Coupling of micropulsation wave modes by the Coriolis force

It is suggested that near to the Earth in the equatorial plane the Coriolis force is as important as the Hall effect in the coupling of micropulsation wave modes.     

The equilibrium points in the perturbed R3BP with triaxial and luminous primaries

This study explores the effects of small perturbations in the Coriolis and centrifugal forces, radiation pressures and triaxiality of the two stars (primaries) on the position and stability of an infinitesimal mass (third body) in the framework of the planar circular restricted three-body problem (R3BP). it is observed that the positions of the usual five (three collinear and two triangular) equilibrium points are affected by the radiation, triaxiality and a small perturbation in the centrifugal force, but are unaffected by that of the Coriolis force. The collinear points are found to remain unstable, while the triangular points are seen to be stable for 0<μ<μ _c and unstable for $\mu_{c} \le\mu\le\frac{1}{2}$ , where μ _c is the critical mass ratio influenced by the small perturbations in the Coriolis and centrifugal forces, radiation and triaxiality. It is also noticed that the former one and all the latter three posses stabilizing and destabilizing behavior respectively. Therefore, the overall effect is that the size of the region of stability decreases with increase in the values of the parameters involved.     

The nature of one mechanism of solar differential rotation

The mechanism of the solar differential rotation usually ascribed to an anisotropic viscosity action is shown to be caused by Coriolis forces which influence anisotropic convective elements in a stratified medium. The estimation of an anisotropy parameters as a function of the convective zone depth is given. The value of (s–1) is positive near the solar surface and negative at the convective zone base, which is in good agreement with observations and the dynamo theory.     

The role of the Coriolis force on the stability of rotating magnetic stars and the origin of convective motions

Based on the method of the energy principle, the effect of the Coriolis force in the stability of rotating magnetic stars is examined and the conditions for instability is derived. It is shown that, in these stars, the effect of this force is to inhibit the onset of convective motion. Discussion is given on the possibility of hydromagnetic dynamo processes in respect to the convective motion inside these stars.     

Effect of Coriolis force on the equilibrium structures of rotating stars and stars in binary systems

Kopal (Adv. Astron. Astrophys. 9:1–65, 1972) introduced the concept of Roche equipotentials to incorporate the effects of rotation and tidal distortions on the equilibrium structure and periods of small oscillations of rotating stars and stars in binary systems. However his expression for the Roche equipotential accounts for only the effects of centrifugal and gravitational forces and does not take into account the effect of Coriolis force. In this paper we have suitably modified Kopal’s expression for Roche equipotentials to incorporate into it the effect of Coriolis force as well. The modified expression for the Roche equipotential has then been used to compute the equilibrium structures and shapes of polytropic models of rotating stars and stars in binary systems.     

The evolution of loop structures in flux rings within the solar convection zone

Choudhuri and Gilman (1987) considered certain implications of the hypothesis that the magnetic flux within the Sun is generated at the bottom of the convection zone and then rises through it. Taking flux rings symmetric around the rotation axis and using reasonable values of different parameters, they found that the Coriolis force deflects these flux rings into trajectories parallel to the rotation axis so that they emerge at rather high latitudes. This paper looks into the question of whether the action of the Coriolis force is subdued when the initial configuration of the flux ring has non-axisymmetries in the form of loop structures. The results depend dramatically on whether the flux ring with the loops lies completely within the convection zone or whether the lower parts of it are embedded in the stable layers underneath the convection zone. In the first case, the Coriolis force supresses the non-axisymmetric perturbations so that the flux ring tends to remain symmetric and the trajectories are very similar to those of Choudhuri and Gilman (1987). In the second case, however, the lower parts of the flux ring may remain anchored underneath the bottom of the convection zone, but the upper parts of the loops still tend to move parallel to the rotation axis and emerge at high latitudes. Thus the problem of the magnetic flux not being able to come out at the sunspot latitudes still persists after the non-axisymmetries in the flux rings are taken into account.National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Strong spherical magnetogasdynamic shock waves in rotating stellar atmosphere

An analytic expression for the velocity of magnetogasdynamic shock wave, propagating in rotating inter stellar atmosphere has been obtained by using the method of characteristics and considering the effect of coriolis force. It has been shown that in the outer convective layer of the star Coriolis force and magnetic field both have significant effect on the shock velocity.     

Axial tilt angles of active regions and their polarity separations

Sunspot group and magnetic (plage) data are examined to search for a relationship between the tilt angles of active regions and the separations of their leading and following portions. A relationship is found in the sense that larger positive tilt angles are associated with larger polarity separations. This is the direction predicted by recent theoretical work (D'Silva and Choudhuri, 1992). The explanation for this appears to be that smaller surface polarity separations lead to larger magnetic tension forces, which diminish the effect of the Coriolis force that acts to twist rising flux tubes.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation.     

Interpretation of an anticipated long-lived vortex in the lower thermosphere following simulation of an isolated substorm

Using a three-dimensional, time-dependent, global model, we have simulated the response of the thermosphere to an isolated substorm. The substorm is characterized by a time variance of the high latitude convective electric field with an associated enhancement of auroral E region electron density, from an initially quiet thermosphere. We have simulated such an impulsive energy input with both separated and co-incident geographic and geomagnetic poles and have found that, in both cases, in the lower thermosphere ( ～ 120 km), a long-lived vortex phenomenon is generated. Initially, two contra-rotating vortices are generated by the effects of ion drag during the period of enhanced high latitude energy input centred on the polar cap/auroral oval boundary, one at dusk (18.00 L.T.) and the other at dawn (06.00 L.T.). After the end of the substorm, the cyclonic vortex (dawn) dissipates rapidly while the dusk anti-cyclonic vortex appears virtually self-sustaining and survives many hours after the substorm input has ceased. A theory is derived to explain and interpret the results and it appears that the effect is analogous to a meteorological weather system. In this case, however, the dusk anti-cyclonic vortex has, instead of pressure, the centrifugal acceleration balancing the Coriolis force. The equivalent anti-clockwise dawn vortex, unlike a low pressure system, has no balancing force, since Coriolis and the centrifugal term assist and this vortex rapidly disappears.