空间科学学报

1989 Vol. 9, No. 4

Previous Issue | Next Issue

Select articles

Display Method:

Cover

NUMERICAL STUDY OF MAGNETIC RECONNECTION PROCESSES IN TWO-RIBBON FLARES

Jin Shu-ping, Hu You-qiu

1989, 9(4): 241-252. doi: 10.11728/cjss1989.04.241

Abstract(1738) PDF 739KB(986)

Abstract:
This paper is aimed at a numerical simulation of the main phase of two-ribbon flares by solving viscous MHDequations in terms of a multistep implicit scheme. The numerical results clearly show the transition from linear reconnection of tearing modes to quasisteady re-connection in the neutral sheet, the formation of post-flare loops, and the ejection of plas-moids.Two cases are considered respectively: one includes and the other does not include Joule heating in the energy equation. It is shown that including Joule heating leads to a substantial increase of temperature (with a factor of 2-3), but a negligible variation of velocity for the plasma within the neutral sheet. The plasma motions are always subsonic for both cases and therefore, no fast shocks are formed.The numerical results of including heating show two new features. One is a reduction and a tendency to saturation of the reconnection rate which is caused by the expansion of the high-density plasma in the neutral sheet, leading to an increase in the effective thickness of the neutral sheet. The other is the formation of ascending and descending plasmoids, and the coalesces of the latter with the post-flare loops.

A STATISTICAL ANALYSIS ON THE ABERRATION ANGLES OF I TYPE COMETS AS WELL AS THE FEATURES OF SOLAR WIND PRESENTED BY THE ANALYSIS

Li Zhong-yuan, Wang Cong-rong

1989, 9(4): 253-259. doi: 10.11728/cjss1989.04.253

Abstract(1848) PDF 468KB(968)

Abstract:
In this paper, it is shown that the aberration angles of Itype cometary tails do not have a clear change with the heliocentric distance, but they have a slow change with the solar latitude. It is also shown that the change of aberration angles with the tangential velocity of comets can be expressed by a monotonic, ascendant, relevant curve. Thus, it is further tested and verified that the dynamical aberration mechanism is a main reason for the formation of aberration angles.In addition, a further analysis by which the features of the velocity field of solar winds are discussed is presented. It is pointed out that the correlation of the average velocity of the solar wind with the heliocentric distance is weak, but the average velocity correlates to the solar latitude. Atrend which shows that the average velocity of solar winds strengthens slowly with the solar latitude is given in the paper.

SIMULATION STUDY OF THE MHD INSTABILITIES CAUSED BY THE SHEARED FLOW AT THE BOUNDARYLAYER OF THE MAGNETOSPHERE

Yan Ming, Pu Zu-yin

1989, 9(4): 260-270. doi: 10.11728/cjss1989.04.260

Abstract(1795) PDF 703KB(884)

Abstract:
Atwo dimension incompressive MHDsimulation is carried out to study the nonlinear waves caused by Kelvin-Helmholtz instability. It is found that three are two attractors. When M_A>8, the system develops towards a steady state one; When M_A<8, it develops towards a periodic attractor. At the boundarylayer of the magnetosphere, the condition of M_A<8 is sa-tified. As a result the amplitude of the K-Hwaves should change periodically. The role of magnetic field in K-Hinstability is also studied. The magnetic field may make the transport of the momentum more efficient.

THE MAIN FEATURES OF THE TURBULENCE SPECTRUM DISTRIBUTION OF THE LARGE SCALE EQUATORIAL SPREAD'F

Wu Ying, Wang Jing-fang, Liang Bai-xian

1989, 9(4): 271-279. doi: 10.11728/cjss1989.04.271

Abstract(1527) PDF 596KB(727)

Abstract:
Starting from the electron continuity equation and considering the effect of a weak geomagnetic shear, after a direct two point regularization, a equation for the evolution of the correlation function of the electron density fluctuation <δn(1)δn(2)> was established and analytically resolved. The resulting spectra are in fair agreement with the observational turbulence spectra of the large scale equatorial spread-F (λ≥100m) in spectral shape, intensity and indexes by the method of least variance fitting. Thus, a unified explaination of the experimental results generally for both the medium and intermediate scale are given, and the similarity of the shapes for above and below the Fpeak, or for parallel and perpendicular to the earth's surface is also explained.

THE 2-DAY OSCILLATIONS OF THE EQUATORIAL ANOMALY

Chen Pei-ren

1989, 9(4): 280-289. doi: 10.11728/cjss1989.04.280

Abstract(1667) PDF 637KB(1045)

Abstract:
The four features of the 2-day oscillations of the equatorial anomaly are revealed, the differences of the variations of the f₀F₂ caused by the ionospheric storm from the 2-day oscillations of the equatorial anomaly are found out, the superposition of the different periods of the planetary scale oscillations of the equatorial anomaly are discussed. Finaly the above results are applied to the ionosphere in east Asia and it is found that to the north of 35°N, the day-to-day variations of the f₀F₂ are caused by the Ionospheric storm and to the south of 31°Nthe day-to-day variations of the f₀F₂ are caused by the superposition of the planetary-scale oscillations of the equatorial anomaly with different period.

THE PROPAGATION OF THE ALFVEN WAVES IN THE FLOW AND THE MAGNETIC FIELD WITH AN ARBITRARY CONFIGURATIONS

Wei Feng-si

1989, 9(4): 290-295. doi: 10.11728/cjss1989.04.290

Abstract(1727) PDF 348KB(609)

Abstract:
This paper presents the propagation features of Alfven waves in the viscous and the thermal anisotropic plasma with an arbitrary flow and magnetic field configurations. The WKBapproximation is used for getting the tensor solution of the Alfven wave amplitude vector, which is a function of the density, velocity, magnetic field, Alfven speed, thermal ani-sotropy and viscosity. Some of simple cases are discussed and the result shows that the solution given by this paper is suitable for general cases and is convenient for studying three dimension propagation problems.

THE GLOBAL DISTRIBUTION OF THE IONIZATION IN THE IONOSPHERIC D-REGION BY GALACTIC COSMIC RAY

Ye Zong-hai, Zong Qiu-gang

1989, 9(4): 296-304. doi: 10.11728/cjss1989.04.296

Abstract(1873) PDF 571KB(1019)

Abstract:
The expressions of the ionizations in ionospheric D-region by relativistic, nonrelativistic and low energy particles of galactic cosmic ray are deduced individually, according to the theory of energy loss of charged particles in the earth's atmosphere. The global distribution of electron production rate q(h) and the electron density N(h) in the low ionospheric D-region by galactic cosmic ray is presented in this paper. The results show that the electron production rate and the electron density in the D-region by galactic cosmic ray have obvious latitude dependance. q(h) and N(h) at polar regions are 3-4 order of magnitude higher than that at low latitudes. The changes of q(h) and N(h) are quite small at R_c≥10GV. The effect of solar activity modulation on q(h) and N(h) are obvious, but its effects are far less than the effects of R_c on q(h) and N(h). The effects of p(h) on q(h) and N(h) are less.

INSTABILITY OF WHISTLER WAVES PRODUCED BY RELATIVISTIC ELECTRON BEAM

Li Fang

1989, 9(4): 305-310. doi: 10.11728/cjss1989.04.305

Abstract(1801) PDF 372KB(879)

Abstract:
According the characters of resonance of relativistic particles with electromagnetic waves, the instability of whistler waves produced by relativistic electron beam is studied. The resonant points in momentum space of particles lie in a series of hyperbolas. For a electron beam of lose-cone distribution this resonant phenomenon makes a rising of the threshold of the instability. This rising is effective in frequency band of w-0.5Ω_e and in case e-Ω_e, and it decreases with the increasing of the parameter w_e/w_e.

THE STRAY LIGHT DBSERVED DURING A PARTIAL ECLIPSE OF THE SUN

Hu Ju, Ni Xiang-bin

1989, 9(4): 311-316. doi: 10.11728/cjss1989.04.311

Abstract(1684) PDF 371KB(926)

Abstract:
In this paper, an diffusion function which discribes the scattering characteristics of the earth's atmosphere is obtained by fitting a theoretical profile with an aureole intensity profile, observed during a partial eclipse on July 31, 1981. This function may be applied to correction of scattered light in the photometry measurements of sunspots or other active phenomena.

MEASUREMENT OF SPACE RADIATION DOSE FOR THE SAMPLES ON BOARD THE SATELLITE

Qi Zhang-nian, Chen Mei

1989, 9(4): 317-320. doi: 10.11728/cjss1989.04.317

Abstract(1834) PDF 259KB(802)

Abstract:
The space radiation dose in the satellite cabin is measured with several dosimeters. They are strictly selected and calibrated using₆₀Co-r source. To determine the lissue doses, the results must be multiplied by 0.995 for LiF, by 0.93 for glass. Many charged particles are recorded by CR-39 plastic nuclear track detecters. The rediation doses measured in the cabin are 0.11 mGy/D. Acomparison of these doses with the previous results measured is made.