Dynamic interaction of plasma flow with the hot boundary layer of a geomagnetic trap

The study of the interaction between collisionless plasma flow and stagnant plasma revealed the presence of an outer boundary layer at the border of a geomagnetic trap, where the super-Alfvén subsonic laminar flow changes over to the dynamic regime characterized by the formation of accelerated magnetosonic jets and decelerated Alfvén flows with characteristic relaxation times of 10–20 min. The nonlinear interaction of fluctuations in the initial flow with the waves reflected from an obstacle explains the observed flow chaotization. The Cherenkov resonance of the magnetosonic jet with the fluctuation beats between the boundary layer and the incoming flow is the possible mechanism of its formation. In the flow reference system, the incoming particles are accelerated by the electric fields at the border of boundary layer that arise self-consistently as a result of the preceding wave-particle interactions; the inertial drift of the incoming ions in a transverse electric field increasing toward the border explains quantitatively the observed ion acceleration. The magnetosonic jets may carry away downstream up to a half of the unperturbed flow momentum, and their dynamic pressure is an order of magnitude higher than the magnetic pressure at the obstacle border. The appearance of nonequilibrium jets and the boundary-layer fluctuations are synchronized by the magnetosonic oscillations of the incoming flow at frequencies of 1–2 mHz.     

Collisionless Plasma Processes at Magnetospheric Boundaries: Role of Strong Nonlinear Wave Interactions

JETP Letters - The sunward Poynting flux throughout the magnetosheath and foreshock (directly measured by INERBALL-1, CLUSTER-4, and DOUBLE STAR TC1) and its correlation and bi-correlation with the...     

Magnetopause charging and transfer of momentum and energy into magnetosphere

The theory of charged current sheets is compared with plasma data of Prognoz-8, Interball-1, Polar, and Cluster satellites. The possibility of momentum and energy transfer into the magnetosphere, irrespective of magnetic field line reconnection, as a specific dynamo effect, is shown. This relates statistical properties of the turbulent boundary layers with the character of the transfer through thin boundaries.     

Turbulent boundary layer at the border of geomagnetic trap

A new phenomenon was discovered on the basis of analysis of the Interball project data. A hot plasma flow is thermalized through the formation of “long-operating” vortex streets and local discontinuities and solitons in a distributed region over polar cusps. Plasma percolation through the structured boundary and secondary reconnection of fluctuating magnetic fields in a high-latitude turbulent boundary layer account for the main part of solar wind plasma inflow into the magnetospheric trap. Unlike local shocks, the ion thermalization is accompanied by the generation of coherent Alfvén waves on the scales ranging from ion gyroradius to the radius of curvature of the averaged magnetic field, as well as by the generation of diamagnetic bubbles with a demagnetized heated plasma inside. This “boiling” plasma has a frequency region where the spectrum is different from the Kolmogorov law (with slopes 1.2 and 2.4 instead of 5/3 or 3/2). The fluctuation self-organization in the boundary layer (synchronization of three-wave decays) was observed on certain frequency scales.     

A comparison between GEOS 1 magnetic-field measurements and some models of the geomagnetic field

Summary A comparison between the quiet-time magnetic-field measurements performed on the GEOS 1 spacecraft in the period May 13, 1977–December 13, 1977 and the predictions of four geomagnetic-field models is presented. For the explored magnetospheric region the best approximation to the GEOS 1 measurements is given by the 1976 Olson and Pfitzer model: the difference between its predictions and the experimental data never exceeds 3 per cent in the absolute value of the field and 3 degrees in the field direction.

---

Riassunto Si presentano i risultati di un confronto fra le misure di campo magnetico eseguite dal satellite GEOS 1 nel periodo 13 Maggio 1977–13 Dicembre 1977 e i corrispondenti valori previsti da quattro diversi modelli di campo geomagnetico. Il confronto è limitato a periodi di quiete geomagnetica. Per le regioni magnetosferiche esplorate, la migliore approssimazione alle misure di GEOS 1 è data dal modello Olson e Pfitzer 1976: la differenza fra i valori sperimentali e previsti è inferiore al 3% nel valore assoluto del campo e a 3° nella sua direzione.

---

Резюме Проводится сравнение измерений магнитного поля, проведенных на спутнике GEOS-I в период с 13 мая 1977 г. по 13 декабря 1977 г., с соответствуюъими предсказаниями четырех моделей геомагнитного поля. Для исследованной области магнитосферы наилучшая аппроксимация измерений, проведенных на GEOS-I, получается с помошью модели Олсона и Пфитцера. Различия между предсказаниями модели и экспериментальными данными никогда не превышают 3% для абсолютной величины поля и 3 градусов для направления поля.

     

Planetary Fourier spectrometer: An interferometer for atmospheric studies on board Mars 94 mission

Summary PFS is a two-channel Fourier spectrometer operating in the infra-red wavelengths between 1.25 and 45 μm. The instrument will be used mainly in the study of the Martian atmosphere. The principal goals are the measurements of the atmospheric temperature and pressure, atmospheric constituents, aerosol and clouds, ground pressure for surface topography, optical and thermophysics properties of the Martian soil. PFS will fly on the Mars 94 spacecraft which should be launched in 1994 and reach the planet in 1995. It is essentially constituted by two different interferometers located in the same box which is divided into two parts. A dichroic placed on the PFS entrance is used to separate the spectral range into two parts, a division needed by the different optical materials which have to be used in each spectral range. The optical layout of the experiment is very compact. Each channel uses two cubic mirrors mounted on an L-structure pivoted on a motor. The motor moves the mechanics and permits the optical-path difference between the arms to be varied. Each interformeter operates in a different spectral range, respectively, between (1.25÷4.8) μm (8000÷2083cm⁻¹) and (6÷45)μm (1666÷220)cm⁻¹). The spectral resolution is 2 cm⁻¹. The entrance aperture area is 30 cm² per channel and the field of view is 2 and 4 degrees. Every measurement lasts about 4 s. The time and, therefore, the relative optical-path difference for the measurement of every point of the interferogram is given by the zero crossings of the interferogram of a reference monochromatic channel at 1.2 μm which uses a laser diode as source. The two interferograms are double-sided and will have 16384 and 4096 points, respectively, corresponding to spectra of 6250 and 1823 useful points. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

On nonlinear cascades and resonances in the outer magnetosphere

The paper addresses nonlinear phenomena that control the interaction between plasma flow (solar wind) and magnetic barrier (magnetosphere). For the first time we demonstrate that the dominant solar wind kinetic energy: (i) excites boundary resonances and their harmonics which modulate plasma jets under the bow shock; (ii) produces discrete three-wave cascades, which could merge into a turbulent-like one; (iii) jet produced cascades provide the effective anomalous plasma transport inside and out of the magnetosphere; (iv) intermittency and multifractality characteristics for the statistic properties of jets result in a super-ballistic turbulent transport regime. Our results could be considered as suggestive for the space weather predictions, for turbulent cascades in different media and for the laboratory plasma confinement (e.g., for fusion devices).     

13C-detection in RNA bases: revealing structure-chemical shift relationships

The chemical shifts of the unprotonated carbons in the proton-deficient nucleobases of RNA are rarely reported, despite the valuable information that they contain about base-pairing and base-stacking. We have developed 13C-detected 2D-experiments to identify the unprotonated 13C in the RNA bases and have assigned all the base nuclei of uniformly 13C,15N-labeled HIV-2 TAR-RNA. The 13C chemical shift distributions revealed perturbations correlated with the base-pairing and base-stacking properties of all four base-types. From this work, we conclude that the information contained in the chemical shift perturbations within the base rings can provide valuable restraint information for solving RNA structures, especially in conformational averaged regions, where NOE-based information is not available.     

High energy jets in the Earth’s magnetosheath: Implications for plasma dynamics and anomalous transport

High energy density jets in the magnetosheath near the Earth magnetopause were observed by Interball-1 [1]. In this paper, we continue the investigation of this important physical phenomenon. New data provided by Cluster show that the magnetosheath kinetic energy density during more than one hour exhibits an average level and a series of peaks far exceeding the kinetic energy density in the undisturbed solar wind. This is a surprising finding because the kinetic energy of the upstream solar wind in equilibrium should be significantly diminished downstream in the magnetosheath due to plasma braking and thermalization at the bow shock. We suggest resolving the energy conservation problem by the fact that the nonequilibrium jets appear to be locally superimposed on the background equilibrium magnetosheath, and, thus, the energy balance should be settled globally on the spatial scales of the entire dayside magnetosheath. We show that both the Cluster and Interball jets are accompanied by plasma superdiffusion and suggest that they are important for the energy dissipation and plasma transport. The character of the jet-related turbulence strongly differs from that of known standard cascade models. We infer that these jets may represent the phenomenon of the general physical occurrence observed in other natural systems, such as heliosphere, astrophysical, and fusion plasmas [2–10]. The text was submitted by the authors in English.