Getting to grips with gravity

Rhaana Starling and Houri Ziaeepour review the 10th Marcel Grossmann meeting, one of the largest international conferences on gravity and related subjects, held this year in Rio de Janeiro, Brazil. It encompassed a wide range of hot topics in fundamental physics and astronomy and this year brought together theorists and observers.     

How to make a magnetosphere

X Blanco-Cano, N Omidi and C T Russell examine the effect of finite ion scale lengths on the formation of planetary magnetospheres.     

Observations of large-scale plasma convection in the magnetosphere with respect to the geomagnetic activity level

The data of the ionospheric observations (the daily f plots) at the Yakutsk meridional chain of ionosondes (Yakutsk–Zhigansk–Batagai–Tixie Bay) with sharp decreases (breaks) in the critical frequency of the regular ionospheric F2 layer (foF2) are considered. The data for 1968–1983 were analyzed, and the statistics of the foF2 break observations, which indicate that these breaks are mainly registered in equinoctial months and in afternoon and evening hours under moderately disturbed geomagnetic conditions, are presented. Calculations performed using the prognostic model of the high-latitude ionosphere indicate that the critical frequency break position coincides with the equatorial boundary of large-scale plasma convection in the dusk MLT sector.     

The magnetosphere of Jupiter: Coupling the equator to the poles

Jupiter is a planet of superlatives: the most massive planet in the solar system, rotates the fastest, has the strongest magnetic field, and has the most massive satellite system of any planet. These unique properties lead to volcanoes on Io and a population of energetic plasma trapped in the magnetic field that provides a physical link between the satellites, particularly Io, and the planet Jupiter. There are strong differences between the magnetospheres of Earth and Jupiter but there are also underlying basic physical principles that all magnetospheres share in common. This paper provides a rough sketch of the magnetosphere of Jupiter, briefly describes the current understanding and lists outstanding issues. As at Earth, a major issue of the jovian system is how the magnetospheric plasma is coupled to the planet's ionosphere.     

Multiscale phenomena in the near-Earth magnetosphere

Several studies on the scaling properties of the near-Earth magnetosphere and auroral phenomena are reviewed. These studies employ modern analysis techniques that include fractal, multifractal, wavelet, wavelet bicoherence, and sign-singularity analyses as well as cellular automaton simulations of sandpile and avalanches. The results provide strong evidence for the multiscale, cross-scale coupling, and reorganization nature of auroral and magnetospheric phenomena, suggesting the possibility that the magnetosphere is in a forced and/or self organized critical state. Signatures of inverse cascade are found in magnetic fluctuations in current disruption events, which may indicate large-scale substorm features such as substorm current wedge and plasmoid may be evolved from small-scale plasma turbulence structures. Insights gained from these studies help to discriminate the existing competing substorm models. The multiscale properties of magnetospheric substorms are consistent with substorm models with intrinsic multiscale processes and not with substorm models with only a macroscopic process.     

Solitons tracked spreading into the magnetosphere

Solitary waves that propagate without losing energy, in theory, have been observed in the Earth's magnetosphere by the Cluster mission.     

Energy regimes in the Earth's magnetosphere

Summary The dynamics of the main processes of energy accumulation and dissipation in the Earth's magnetosphere at various geomagnetic disturbance levels is examined. The results of the relevant calculations are tabulated. The relationships between the energy parameters of the solar wind and the Earth's magnetosphere are analyzed. Some conclusions concerning the field-aligned currents in polar caps, the Joule dissipation of energy and the energy injection into the ring current, the energy releases in the upper ionosphere, etc., are drawn.

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Supply of energy to the magnetosphere during the main phase of magnetic storms

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地球磁层的磁场模型

1958年卫星探测发现了磁层,至今已有半个世纪,对磁层电场、电流体系、磁场、粒子分布和等离子体波的探测研究构成了空间物理的重要内容,其结果是各种磁层模型的出现.本文简要综述磁层磁场建模的基本原理、方法和发展历史,对十几种重要的磁层模型的特点、局限性和适用范围进行了对比分析,以Tyganenko模型为例,讨论了磁层模型发展的趋势.     

Physical mechanisms of man-made influences on the magnetosphere

Since the discovery of the Luxembourg effect in the 1930s, it is clear that man-made activities can perturb the ionosphere and the magnetosphere. The anthropogenic effects are mainly due to different kinds of waves coming from the Earth's surface. Acoustic-gravity waves are generated by large explosions, spacecraft launches, or flight of supersonic planes. Electromagnetic waves are active in different frequency ranges. Power line harmonic radiation which is radiated in the ELF range by electrical power systems can be observed over industrial areas. At VLF and HF, the ground-based transmitters used for communications or radio-navigation heat the ionosphere and change the natural parameters. A large variety of phenomena is observed: wave-particle interaction, precipitation of radiation belt electrons, parametric coupling of EM whistler waves, triggered emissions, frequency shift, and whistler spectrum broadening. This paper will review the different physical mechanisms which are relevant to such perturbations. The possibility of direct chemical pollution in the ionosphere due to gas releases is also discussed.     

Erosion of the inner magnetosphere during geomagnetic storms

Using the empirical magnetic field model dependent on the Dst index and solar wind dynamic pressure, we calculated the behaviour of the contour B = B_s in the equatorial plane of the magnetosphere where B_s is the magnetic field in the subsolar point at the magnetopause. The inner domain of the magnetosphere outlined by this contour contains the bulk of geomag-netically trapped particles. During quiet time the boundary of the inner magnetosphere passes at the distance ∼10R_E at noon and at ∼7R_E at midnight. During very intense storms this distance can be reduced to 4–5 R_E for all MLT. The calculation results agree well with the satellite measurements of the magneto-pause location during storms. The ionospheric projection of the B = B_s contour calculated with the Euler potential technique is close to the equatorward edge of the auroral oval.     

Field-aligned currents of zones 1 and 2 in the magnetosphere according to the experimental data

The discrepancy between the model and measured magnetic fields, which can be described by the contribution of field-aligned currents, has been determined. The division of the initial data array into the individual data sets with different IMF values makes it possible to estimate the dependence of field-aligned currents on IMF.     

Magnetospheric-ionospheric convection in an open model of the magnetosphere

Magnetospheric-ionospheric convection has been calculated for an open model of the magnetosphere with an ellipsoidal magnetopause in an approximation of uniform IMF. It is assumed that only 0.1 part of IMF falls in the magnetosphere as a result of the effect of IMF shielding by the magnetopause. The modeling of convection has been performed for the cases when the IMF B _z component is directed southward and the B _y component is westward or eastward. A Tsyganenko 96 model has been used as a magnetospheric model. The model calculations are compared with the data on the ion drift in the ionosphere. A certain disagreement between the experimental and calculated data has been found in the pattern of convection on the dayside of the ionosphere for the case of B _y >0, which manifested itself in the dimensions of a convection “tongue” and in the position of the convection throat on the dayside. It has been indicated that the convection pattern agrees with the results of observations if the azimuthally inhomogeneous magnetospheric conductivity is taken into account.     

Relation of geomagnetic disturbances to the dynamics of the magnetosphere and the parameters of the interplanetary medium

The results of studying the dependence of the earthward shift of the magnetospheric boundaries on the magnetic storm power are generalized. The magnetosphere saturation effect, a sharp deceleration of the boundary shift at an increase in the ring current power above a certain critical level, is discussed. The geoeffectiveness of the solar wind parameters is discussed.