ASPI experiment: measurements of fields and waves on board the INTERBALL-1 spacecraft

The plasma-wave experiment ASPI (analysis of spectra of plasma waves and instabilities) on board the INTERBALL spacecraft is a combined wave diagnostics experiment. It performs measurements of the DC and AC magnetic field vector by flux-gate and searchcoil sensors, the DC and AC electric field vector by Langmuir double probes and the plasma current by Langmuir split probe. Preliminary data analysis shows the low noise levels of the sensors and the compatibility of new data with the results of previous missions. During several months of in-orbit operation a rich collection of data was acquired, examples of which at the magnetopause and plasma sheet are presented in second part of the paper.     

Numerical modeling of ocean hydrodynamics with variational assimilation of observational data

Models and methods of the numerical modeling of ocean hydrodynamics dating back to the pioneering works of A.S. Sarkisyan are considered, with emphasis on the formulation of problems and algorithms of mathematical modeling and the four-dimensional variational assimilation of observational data. An algorithm is proposed for studying the sensitivity of the optimal solution to observational data errors in a seasurface temperature assimilation problem in order to retrieve heat fluxes on the surface. An example of a solution of the optimal problem of the World Ocean hydrodynamics with the assimilation of climatic temperature and salinity observations is offered.     

On the meridional circulation and balance of momentum in the Southern Ocean of POP

 The circulation of the Southern Ocean is studied in the eddy-resolving model POP (Parallel Ocean Program) by an analysis of zonally integrated balances. The TEM formalism (Transformed Eulerian Mean) is extended to include topography and continental boundaries, thus deviations from a zonally integrated state involve transient and standing eddies. The meridional circulation is presented in terms of the Eulerian, eddy-induced, and residual streamfunctions. It is shown that the splitting of the meridional circulation into Ekman and geostrophic transports and the component induced by subgrid and Reynolds stresses is identical to a particular form of the zonally integrated balance of zonal momentum. In this balance, the eddy-induced streamfunctions represent the interfacial form stresses by transient and standing eddies and the residual streamfunction represents the acceleration of the zonal current by density fluxes in a zonally integrated frame. The latter acceleration term is directly related to the surface flux of density and interior fluxes due to the resolved and unresolved eddies. The eddy-induced circulation is extremely vigorous in POP. In the upper ocean a shallow circulation, reversed in comparison to the Deacon cell and mainly due to standing eddies, appears to the north of Drake Passage latitudes, and in the Drake Passage belt of latitudes a deep-reaching cell is induced by transient eddies. In the resulting residual circulation the Deacon cell is largely cancelled and the residual advection of the zonal mean potential density is balanced by diapycnal eddy and subgrid fluxes which are strong in the upper few hundred meters but small in the ocean interior. The balance of zonal momentum is consistent with other eddy-resolving models; a new aspect is the clear identification of density effects in the zonally integrated balance. We show that the wind stress and the stress induced by the residual circulation drive the eastward current, whereas both eddy species result in a braking. Finally, we extend the Johnson–Bryden model of zonal transport to incorporate all relevant terms from the zonal momentum balance. It is shown that wind stress and induction by the residual circulation carry an eastward transport while bottom form stress and the stress induced by standing eddies yield westward components of transport. Received: 26 June 2001 / Accepted: 2 November 2001     

Dynamics of artificial plasma clouds in “SPOLOKH“ experiments : Cloud deformation

Data on the evolution of the density profiles of the neutral and ionized components of barium clouds obtained in “Spolokh” experiments are presented. The ion density in the cigar-like structure exceeds by more than an order of magnitude that of the background plasma, while the density in the plasma tail out flowing from the cigar-like structure is of the same order as that of the background plasma. The Ba⁺ outflow rate is determined. The results agree with observed cloud motion and with the estimates following from Dzubenko et al. (1983).     

Phenomenological Model of Natural Dispersion of an Oil Spill in the Sea and Some Associated Parameterization Processes

Oceanology - The paper proposes a new parameterization of natural dispersion of a marine oil spill due to wind-wave breakup of the oil slick and penetration of oil droplets into the water. The...     

Dynamics of artificial plasma clouds in “Spolokh” experiments: Movement pattern

The data on space location and movement of the high-density (n_c? n_b) barium clouds injected at midlatitudes during the “Spolokh-1” and “Spolokh-2” shaped-charge experiments in the ionosphere are presented. At the initial stage, the neutral and ionized components move together at a speed of the neutral wind. An outflow of ions in the form of a stratified tail was also observed. Its movement is interpreted as a drift in [E₀ × B] fields. The evolution pattern of artificial plasma clouds agrees with the qualitative scheme described in the paper.     

On the equatorward phase propagation of high-m ULF pulsations observed by radars

An often observed and still unexplained feature of the high-m Alfvén waves in the terrestrial magnetosphere is their equatorward phase motion, in contrast with low-m waves. We suggest an explanation of this fact in terms of a model of wave excitation by an azimuthally drifting particle inhomogeneity injected during substorm activity. The azimuthal direction of the phase velocity coincides with that of the cloud. If the drift velocity increases with the radial coordinate, the particle cloud is stretched into spiral in the equatorial plane which leads to a radial component of the phase velocity directed toward Earth, that is, an equatorward phase propagation.     

Simultaneous observations of small multi-scale structures in an auroral arc

Auroral arcs can develop small-scale distortions known as vortex streets or curls. Other common and somewhat larger spatially periodic distortions are auroral folds. In this event study we present simultaneous wide and narrow field imager observations of a third kind of structuring, on even smaller spatial scales. Boundary undulations, or “ruffs”, have been observed to form on the edge of an auroral arc and they occur superimposed on curls, folds or at times of auroral shear. The undulations typically have wavelengths of less than 3 km and amplitudes of less than 800 m. They are observed to move on the edge of the arc, with velocities of about 11 km/s. These observations, with multi-scale deformations, reveal a much more intricate structuring of auroral arcs than previously found.     

Diffusion-Rotational Parameterization of Eddy Fluxes of Potential Vorticity: Barotropic Flow in the Zonal Channel

Izvestiya, Atmospheric and Oceanic Physics - The problem of parameterizing the eddy flux of a potential vorticity is discussed. The traditional diffusion parameterization is complemented by the...