Interplanetary energy flux associated with magnetospheric substorms

It is shown that the interplanetary quantity ε(t), obtained by Perreault and Akasofu (1978), for intense geomagnetic storms, also correlates well with individual magnetospheric substonns. This quantity is given by $\text{ε(t) = VB}{}^2\text{sin}{}^4\text{(}\text{θ}\text{2}\text{)l}{}_{\mathrm{o}}{}^2$, where V and B denote the solar wind speed and the magnitude of the interplanetary magnetic field (IMF), respectively, and θ denotes the polar angle of the IMF; l_o is a constant ? 7 Earth radii. The AE index is used in this correlation study. The correlation is good enough to predict both the occurrence and intensity of magnetospheric substonns observed in the auroral zone, by monitoring the quantity ε(t) upstream of the solar wind.     

The solar wind-magnetosphere energy coupling and magnetospheric disturbances

The recent finding of the solar wind-magnetosphere energy coupling function ε has advanced significantly our understanding of magnetospheric disturbances. It is shown that the magnetosphere-ionosphere coupling system responds somewhat differently to three different input energy flux levels of ε. As ε increases from < 10¹⁷ erg s^?1 to > 0¹⁹ erg s^?1, typical responses of the magnetosphere-ionosphere coupling system are:ε < 10¹⁷ erg s^?1: an enhancement of the S_q^p, etc,ε ≈ 10¹⁸ erg s^?1: substorm onset,10¹⁸ erg s^?1 < ε < 10¹⁹ erg s^?1f: a typical substorm,ε >10¹⁹ erg s^?1: an abnormal growth of the ring current belt, resulting in a magnetospheric storm.It is stressed that the magnetospheric substorm results as a direct response of the magnetosphere to a rise and fall of ε above ≈ 10¹⁸ erg s^?1, so that it is not caused by a sudden conversion of magnetic energy accumulated prior to substorm onset. The variety of the development of the main phase of geomagnetic storms is also primarily controlled by ε.     

Correlation between the energy supplied by reconnection and the magnetospheric energy consumption

This study investigates the statistical correlation between the power input into the magnetosphere due to reconnection and the subsequent dissipation of this energy in the magnetosphere as measured by the U_T parameter (Perreault and Akasofu, 1978). It is found that of the three expressions for this energy input P_W, P_K (Gonzalez and Gonzalez, 1984) and ε (Perreault and Akasofu, 1975; Kan et al.,1980), P_W yields the highest correlation with the energy consumption of the magnetosphere.     

Scaling relations of field spirals at intermediate redshift

In the last few years, galaxies at redshifts up to z ∼ 1 have become accessible for medium-resolved spectroscopy thanks to the new generation of 10 m-class telescopes. With kinematic and photometric information on spiral galaxies in this regime, well-known scaling relations like the Tully-Fisher relation (TFR) can be studied over half a Hubble time. By comparison to local samples, these studies facilitate simultaneous tests of the hierarchical merging scenario and stellar population models. Using the Very Large Telescope, we obtained spatially resolved rotation curves of 78 spiral galaxies in the FORS Deep Field (FDF), covering all Hubble types from Sa to Sm/Irr at redshifts 0.1 < z < 1.0. We find evidence for a B-band luminosity increase of up to 2 mag for low-mass spirals, whereas the most massive galaxies are of the same luminosity as their local counterparts. In effect, the TFR slope decreases significantly. This would explain the discrepant results of previous observational studies. We also present the velocity-size relation and compare it to the predictions of numerical simulations based on the hierarchical merging scenario. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dynamo process governing solar wind-magnetosphere energy coupling

Based on the method of dimensional analysis, the energy transfer rate from the solar wind into the magnetosphere can be characterized by a magnetic coupling parameter α on open field lines and by a viscous coupling parameter β on closed field lines. By assuming that the energy transfer rate can be monitored by the total energy dissipation rate of the magnetosphere, the histogram of α is constructed and is found to peak around ?0.1 < α < 0.1. This result implies that the energy transfer is governed primarily by the MHD dynamo process on open field lines and indicates that the ? function obtained by Perreault and Akasofu is verified as the first approximation of the solar wind-magnetosphere energy coupling function.     

The magnetospheric plasma as a source of energy for space instrumentation

It is proposed to convert the thermal motion of a plasma into electrical power: energetic electrons collected by a plate dissipate their energy into a load, and are re-injected into the medium by means of an electron source. This concept may find applications in the magnetospheres of the outer planets, but present knowledge does not allow one to assess whether the energy fluxes are sufficient for practical applications. It is therefore neccessary to perform in situ preliminary investigations with electron emitters. It is pointed out that electron sources can be simultaneously used for additional tasks: spacecraft potential clamping, plasma diagnostics and detection of electromagnetic and electrostatic waves.     

Some new nonlinear relations of radiative transfer theory

This paper presents some new results concerning the generalization and physical interpretation of Rybicki's quadratic and bilinear relations. The fundamental equations obtained on the basis of Ambartsumian's invariance principle and regarded as its extension to all depths in the atmosphere, imply Q- and R-relations have a more general structure than those known up to the present. These equations admit a simple probabilistic interpretation. Some bilinear relations are derived to connect the transfer problems of different sorts. For the sources distributed in the semi-infinite atmosphere by exponential law, separate Q- and R-relations are obtained.Published in Astrofizika, Vol. 38, No. 4, pp. 577–586, October–December, 1995.     

Plasma-sheet dynamics and magnetospheric substorms

We present a conceptual model of the formation of the plasma sheet and of its dynamical behavior in association with magnetospheric substorms. We assume that plasma mantle particles $\text{E}\text{～}\text{×}\text{B}\text{～}$ drift toward the current sheet in the center of the tail where they are accelerated by magnetic-field annihilation to form the plasma sheet. Because of the velocity-dependent access of mantle particles to the current sheet, we argue that the convection electric field and the corresponding rate of field annihilation decrease with increasing radial distance. As a consequence, there exists no steady-state configuration for the plasma sheet, which must instead shrink continuously in thickness until the near-earth portion of the current sheet is disrupted by the formation of a magnetic neutral line. The current-sheet disruption launches a large-amplitude hydromagnetic wave which is largely reflected from the ionosphere. The reflected wave sets the neutral line in motion away from the earth; the neutral line comes to rest at a distance (which we estimate to be a few hundred earth radii) where the incoming mantle particles enter the current sheet at the local Alfvén velocity. At this “Alfvén point” reconnection ceases and the thinning of the plasma sheet begins again. Within this model, the magnetospheric substorm (which is associated with the current-sheet disruption) is a cyclical phenomenon whose frequency is proportional to the rate of convection in the magnetospheric tail.     

Some critical issues on magnetospheric substorms

Several evidences for the directly driven aspect of magnetospheric substorms are presented by reinterpreting what have been thought to be supporting evidences for the unloading process. Further, it is stressed that some of our confusions in substorm studies could be resolved by understanding that the magnetospheric substorm is primarily a directly driven phenomenon, but has a variety of internal processes. A method is suggested tto identify the directly driven and the unloading components. It is also demonstrated that the magnetosphere is intrinsically a non-linear system and that a quantitative study of magnetospheric substorms is not possible without taking into account this non-linearity.     

A modeling of the magnetospheric substorm

This paper reports some results of an attempt to simulate the large-scale changes of the internal structure of the magnetosphere during the magnetospheric substorm by assuming the growth of two current systems, one in the nightside and the other in the day-side.     

Interplanetary shock waves and magnetospheric substorms

It is shown that substorm activity after a storm sudden commencement (S.S.C.) depends on whether or not an interplanetary shock wave is accompanied by a large increase of the solar wind-magnetosphere energy coupling function ε. It has long been thought that substorm activity associated with an S.S.C. results from sudden conversion of magnetic energy stored in the magnetotail and that this conversion is triggered by the shock wave. However, the present result implies that the magnetospheric substorm is not a sudden conversion of stored magnetic energy, but is a direct consequence of increased efficiency of the solar wind-magnetosphere dynamo.     

ROY—A multiscale magnetospheric mission

The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations of plasma processes in the key magnetospheric regions with strong plasma gradients, turbulence and magnetic field annihilation in the range from electron inertial length to MHD scales.The main scientific aims of ROY mission include explorations of:

(a)

turbulence on a non-uniform background as a keystone for transport processes;

(b)

structures and jets in plasma flows associated with anomalously large concentration of kinetic energy; their impact on the energy balance and boundary formation;

(c)

transport barriers: plasma separation and mixing, Alfvenic collapse of magnetic field lines and turbulent dissipation of kinetic energy;

(d)

self-organized versus forced reconnection of magnetic field lines;

(e)

collisionless shocks, plasma discontinuities and associated particle acceleration processes.

In the case of autonomous operation, 4 mobile spacecrafts of about 200 kg mass with 60 kg payload equipped with electro-reactive plasma engines will provide 3D measurements at the scales of 100-10000 km and simultaneous 1D measurements at the scales 10-1000 km. The latter smaller scales will be scanned with the use of radio-tomography (phase-shift density measurements within the cone composed of 1 emitting and 3 receiving spacecrafts).We also discuss different opportunities for extra measurement points inside the ROY mission for simultaneous measurements at up to 3 scales for the common international fleet.Combined influence of intermittent turbulence and reconnection on the geomagnetic tail and on the nonlinear dynamics of boundary layers will be explored in situ with fast techniques including particle devices under development, providing plasma moments down to 30 ms resolution.We propose different options for joint measurements in conjunction with the SCOPE and other missions:

•

simultaneous sampling of low- and high-latitudes magnetopause, bow shock and geomagnetic tail at the same local time;

•

tracing of magnetosheath streamlines from the bow shock to near-Earth geomagnetic tail;

•

passing “through” the SCOPE on the inbound orbit leg;

•

common measurements (with SCOPE and other equatorial spacecraft) at distances of ∼ few thousand km for durations of ∼several hours per orbit.

The orbit options and scientific payload of possible common interest are discussed in this work, including FREGAT cargo opportunities for extra payload launching and the “Swarm” campaigns with ejection of nano- and pico-satellites.     

Persistent particle anisotropies and magnetospheric models

The influence of an interplanetary particle anisotropy on the asymmetry of solar particle entry into the magnetotail is analysed in the diffusion as well as in the reconnection model. By time dependent diffusion calculations with an asymmetric boundary condition in a cylindrical tail lobe it can be shown that a north-south interplanetary anisotropy leads in the open as well as in the closed magnetosphere to essentially the same polar cap structures when observed with a dawn-dusk polar orbiting satellite. However, depending on the satellite orbit, an east-west interplanetary anisotropy can serve to distinguish between rival magnetospheric models. Comparison of our diffusion calculations with polar cap measurements during an east-west interplanetary anisotropy, as presented in Morfill and Scholer (1972), show a large discrepancy, whereas an open tail model fits these observations best.