Li Zhong-yuan

Bifurcated Current Sheet Structure in a Quiet Time by Cluster Spacecrafts

We analyse the vertical structure of the magnetotail current sheet for two time intervals during which the Cluster spacecrafts crossed the neutral sheet in a quiet time. In the intervals, the current sheet moved slowly, and the value of the AE index was relatively small, about 40–130 nT. We find two examples of current sheets, with the current density maximum at the magnetic equator (Bx = 0), as well as an example of off-centre or bifurcated current sheets. In the quiet time, without any fast plasma flow and without significant flapping motion, we also directly observed the bifurcated current sheet. The bifurcated current sheet is probably associated with instabilities in the current sheet. These may be important for researching the mechanism of current sheet bifurcation.

The geomagnetic storm of 1910 May 18 and the tail of Halley's comet

Abstract We argue that the geomagnetic storm observed on 1910 May 18 at the Lu-Kia-Pang Observatory near Shanghai is possibly connected with the tail of Halleys Comet, rather than originating in some solar activity.

Influence of Ion Nonlinear Polarization Drift and Warm Ions on Solitary Kinetic Alfvén Wave

Considering the effects of ion nonlinear polarization drift and warm ions, we adopt two-fluid model to investigate the character of low-frequency Solitary Kinetic Alfven Wave (SKAW hereafter) in a magnetic plasma. The results derived in this paper indicate that dip SKAW and hump SKAW both exist in a wide range in magnetosphere (for the pressure parameter , where is the ratio of thermal pressure to magnetic pressure, i.e. ). These two kinds of SKAWs propagate at either Super-Alfvenic velocity or Sub-Alfvenic velocity. In the inertial region , the Sub-Alfvenic velocity dip SKAWs and hump SKAWs both exist; in the transmittal region , dip SKAWs and hump SKAWs propagate at Super-Alfvenic velocity or Sub-Alfvenic velocity; Super-Alfvenic velocity hump SKAWs and Super-Alfvenic and Sub-Alfvenic velocity dip SKAWs are in the kinetic region . These results are different from previous ones. That indicates that the effects of ion nonlinear polarization drift and warm ions are important and they cannot be neglected. The SKAW has an electric field parallel to the ambient magnetic field, which makes the SKAW take an important role in the acceleration and energization of field-aligned charged particles in magnetic plasmas. And the SKAW is also important for the heating of a local plasma. So it makes a novel physical mechanism of energy transmission possible.

Effect of dust charge fluctuations on Kelvin–Helmholtz instability in a cold dust plasma

Effect of dust charge fluctuations on Kelvin–Helmholtz (K–H) instability driven by sheared dust flow with both perpendicular and parallel components to magnetic field is investigated in magnetized three-component cold dust plasma. It is found that K–H instabilities are mainly driven by the parallel component of the sheared dust flow. The perpendicular component of the sheared dust flow influences the extent of the oblique propagation of the unstable perturbed wave with respect to the ambient magnetic field. For a dense dust plasma, as the perturbed frequency is much higher than the dust charging frequency, the maximum damping rate of the perturbed wave due to dust charge fluctuations will reach the order of the dust charging frequency. In this case, the critical shear for the parallel K–H instability increases rapidly because of the charging processes in the long-wavelength perturbation.

THE RADIATION FEATURES OF THE MOVING CHARGES AND THE EFFECTS SUPPRESSED BY THE COSMIC PLASMAS IN PULSARS AND OTHER CELESTIAL BODIES

In this paper, we have discussed the feature of radiation resulting from the moving magnetic charges in detail. We have pointed out that there is the curvature radiation of the monopoles in pulsars and other celestial bodies, but this radiation can intensely be suppressed by the cosmic plasma.

The Influence of the non-linear term in the ionic polarization drift on solitary kinetic Alfven wavest☆☆☆

Abstract It is shown that the nonlinear term in the ionic polarization drift has a non-negligible effect on the solitary kinetic Alfven waves (SKAW) of the rarefied type in low-β plasmas (β is the heat to magnetic energy ratio) i.e. the nonlinear term allows the existence of SKAW with both sub- and super-Alfvenic speeds in the low-β regime. This result appears to be in good agreement with satellite observations of the magnetosphere.

The influence of comet passage on the magnetosphere

Abstract We make a data analysis and statistical study of possible effects on the earths magnetosphere caused by five passages at different times and under different circumstances of the three comets, Halley, Hyakutake and Hale-Bopp. We point out that while disturbance is entirely possible according to the physical properties of comets tail, whether or not disturbance will occur depends strongly on the circumstances of the passage.

Coronal expansion and the transfer of solar angular momentum to the interplanetary space

Abstract We discuss the question of loss of angular momentum through coronal expansion. From a large volume of data on Type-1 cometary tails we have confirmed the presence of a tangential component in the coronal expansion, which has not only a stochastic component but also a constant component of 9.8 km/s. Through coronal expansion the Sun has lost 80% of its angular momentum since it evolved on to the main sequence and the angular velocity of the Sun is decreasing exponentially. This result should have a large effect on the dynamical evolution of the Sun.

The curvature radiation of cosmic monopoles

Abstract It is shown that curvature radiation of magnetic monopole is suppressed in a plasma medium.

Proper motions of 64 RR Lyrae variable stars

Abstract The relative proper motions of 64 RR Lyrae variables are determined using Turners method. The first-epoch positions are taken from the Carte du Ciel Astrographic Catalogue, while the second-epoch positions are measured positions from plates taken with the 40-cm refractor ( f =6.9 m) of the Zo-Se Section, Shanghai Observatory, in 1962–1965. The average interval between the two epochs is about 60 years. The mean error in the proper motion is ± 0.005″/y. The absolute proper motions of these variables are found after correcting for the parallactic motions and the galactic differential rotation. The results are given in 3 TABLES.