空间科学学报

1995 Vol. 15, No. 3

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THE FORMATION AND EVOLUTION OF ASYMMETRICAL HIGH DENSITY CLOUD AND NON-LINEAR WAVE IN A CORONAL MASS EJECTION EVENT

Zhang Gong-liang

1995, 15(3): 169-178. doi: 10.11728/cjss1995.03.169

Abstract(1857) PDF 712KB(1174)

Abstract:
The SMM observation of the 18 August 1980 coronal mass ejection is analyzed thoroughly and quantitatively,using the function fitting and digital filtering tech niques.It is shown that the formation of an asymmetrical high density cloud is something related to the deviation in the location of eruptive prominence with respect to the asymmetrical axis of the streamer.The evolution of the asymmetrical structure and its influence on the development of the event are discussed.The dark cavity is proved to be an expanding structure with strong magnetic field. From the radial brightness profiles,the first observational evidence for the front steepening of a non-linear coronal wave during its evolution is found with the time and height for shock formation estimated.The results of the present study are in favor of the event driven by an expanding strong magnetic field structure,rather than by a thermal impulse.

MERGING OF MHD OBLIQUE SHOCKS

Hu You-qiu, Xun Xiao-dong

1995, 15(3): 179-186. doi: 10.11728/cjss1995.03.179

Abstract(2055) PDF 563KB(957)

Abstract:
This paper discusses.the merging of fast and slow MHD shocks.The main conclusions are as follows.(1)Merging of two forward fast shocks forms a stronger forward fast shock, followed by a forward slow rarefaction wave,a positive contact surface(with a larger density at the rear),a reverse slow shock,and a reverse fast rarefaction wave.(2)Merging of two forward slow shocks forms a stronger forward slow shock, followed by a positive contact surface,a reverse slow rarefaction wave, and a reverse fast shock.Aforward fast wave appears in front of the forward slow shock,being either a rarefaction wave for moderate shock angle case or a shock for large shock angle case.(3)Aforward fast shock will catch up with a forward slow shock.As a result,the two shocks exchange places andreduce in strength, followed by a positive contact surface and a pair of reverse rarefaction waves.

A NUMERICAL STUDY ON DYNAMICS OF COMETARY PLASMA TAIL

Zheng Hui-nan, Wang Shui

1995, 15(3): 187-195. doi: 10.11728/cjss1995.03.187

Abstract(1910) PDF 634KB(610)

Abstract:
In this paper,on the basis of a compressible magnetohydrodynamic model,the dynamics of the cometary plasma tail with a super-Alfvenic flow in the lobes arestudied numerically. The results show that the streaming tearing instability is excited by the sheared plasma flow which exists between the plasma sheet and the lobes.It causes magnetic reconnection and forms the magnetic islands and plasmoids with high plasma density in the plasma sheet of cometary tail.Furthermore the effect of a local driving force delivered by the solar wind on magnetic reconnection in the plasma tail of comets is also simulated.But its characteristic time is larger than that of the streaming tearing mode.It is suggested that some of knots and disconnection events observed in the plasma tail of comets may be mainly associated with the streaming tearing instability produced by the sheared plasma flow in cometary tail.

IONOSPHERIC SCINTILLATION OF COSMIC RADIO NOISE AND THE STRUCTURAL PARAMETERS OF IONOSPHERIC IRREGULARITIES

Chen Zhong-sheng, Ma Guan-yi

1995, 15(3): 196-206. doi: 10.11728/cjss1995.03.196

Abstract(2340) PDF 801KB(1278)

Abstract:
Based on the assumption that the Cosmic Radio Noise is an isotropic backgrouna electromagnetic radiation, by use of the ray-optics method the expression of the scintillation power spectrum of electron density space fluctuation is obtained,which obeys the inverse power low of the ionospheric irregularities.Compared with that of Radiostar and satellite beacon scintillation.the ionospheric scintillation of cosmic radio noise reduces the number of variables,the variable introduced by relative movement no longer exist.The effect of the structure parameters L_y、l_y、p、η, on the power spectrum is also studied using numerical simulation. As a result, it is found that more than 60% of the irregular strutures associated with the data recorded by Riometer during the period of the ionospheric absorption events have L_y> √λZ and 0.2<η <0.5.

CROSS-EQUATOR IPROPAGATION OF PLANETARY WAVES IN MIDDLE ATMOSPHERE

Ma Rui-ping

1995, 15(3): 207-214. doi: 10.11728/cjss1995.03.207

Abstract(1977) PDF 537KB(1202)

Abstract:
A semi-spectral model of global primitive equation is used to simulate the cross-equator propagation of quasi-stationary planetary waves.The results show that the amplitude fluctuation and phase variation of the quasi-stationary planetary waves at the tropopause in winter can cause the cross-equator propagation of the planetary waves in the middle atmosphere and create the transient planetary waves in the summer hemisphere.A new mechanism that the cross-equator propagation of the planetary waves in the middle atmosphere and the source of the planetary waves in summer hemisphere and the coupling between northern and southern hemispheres was advanced by the simulation.

THE WAKE OF THE SPACE PLASMA GENERATED BY LOW ORBIT SPACECRAFT

Gu Shi-fen, Shi Liqin, Song Li, Tian Bac-ning

1995, 15(3): 215-221. doi: 10.11728/cjss1995.03.215

Abstract(1863) PDF 386KB(991)

Abstract:
A computer two-dimension simulation model of the plasma wake generated by low orbit spacecraft in developed.Calculated results show:(1)With the increase of negative surface potential the wake becomes narrower.(2)With the increase of ion Mach number the potential well becomes wider and deeper.(3)The electrons are concentrated in the near wake region when the surface potential is positive while the ions are depleted in a larger region than when surface potential is negative.

DISTRIBUTION OF SOME PHYSICAL PARAMETERS IN THE LOOP-LIKE STRUCTURE FORMED IN THE DECAY OF A TORNADO PROMINENCE

Li Ke-jun, Zhong Shu-hua, Ding You-ji

1995, 15(3): 222-227. doi: 10.11728/cjss1995.03.222

Abstract(1563) PDF 391KB(911)

Abstract:
Geometrical configuration of a loop-like structure in solar atmosphere is usually determined by physical features in it.According to conservation of mass,the equation of state in a loop tube, and conservations of momentum along normal direction and inclination direction of a loop tube respectively, a loop-like flux tube of the tornado prominence on August 29,1990 is calculated and the velocity.density and the'magnetic field strength distributions along the loop-like flux tube of the tornado prominence are given in this paper. Results obtained show that the downward motion of the matter within the flux tube is mainly determined by gravity,meanwhile,the density and magnetic field strength distributions are closely related to the geometrical configuration of the flux tube.

THE OUTSTANDING OF THE SOLAR RADIO BURSTS AND TypE II RADIO BURSTS

Wang Shu-lan, Fu Qi-jun

1995, 15(3): 228-233. doi: 10.11728/cjss1995.03.228

Abstract(1812) PDF 337KB(566)

Abstract:
This discussion is based on the outstanding events of solar radio bursts observed by Beijing Astronomical Observatory and Type II, IV radio bursts during 60 months, from Jan.11989 to Dec.30,1993.The Data of radio bursts of Type IIand IVare from S. G. D.,The results of the correlation between S_p and △T and solar flux show that the higher the flux is,the shorter the △T. When solar flux is very high or even more than 500 s.f.u.,Type IIonset procedes microwave burst maximum or occurs later.These results show that they may connect with high particles'acceleration.

STUDY OF VARIATION THE CHANGE IN THE ELECTRON DENSITY POWER SPECTRA OF SOLAR WIND BEFORE AND AFTER A FLARE-SHOCK USING OBSERVED Ips DATA

Ye Pin-zhong, Ma Zhao-hui

1995, 15(3): 234-238. doi: 10.11728/cjss1995.03.234

Abstract(1981) PDF 347KB(684)

Abstract:
Applying the weak scattering and thin-screen approximation model,we have evaluated the observation data on the interplanetary scintillation(IPS)of a flareshock on June 15, 1972 by the use of the FFTand Abel transfer approaches.The electron density power spectra of solar wind before and after the shock are computed,respectively. The results suggest that the spectra are in the form of a power law function at small wave numbers (0.001 to 0.009km).The power law index after the shock are greater than those before the shock,implying that the power spectra at the small wave number range become slightly steeper after passing through the shock.

THE EQUATORIAL COUNTER ELECTROJET AND THE MAGNETOSPHERIC DISTURBANCES

Seen Changshou, Zi Min-yun

1995, 15(3): 239-244. doi: 10.11728/cjss1995.03.239

Abstract(1931) PDF 411KB(952)

Abstract:
The data of geomagnetic H-component from Trivandrum,India, during 21-the solar cycle have been analysed.Anew possible mechanism is introduced in discussion of the counter electrojet.The ionospheric disturbance dynamo and the ring current may drive strong westward ionospheric current on disturbed and following days. On the other hand, during quiet days the weak magnetospheric disturbance could impel the afternoon counter electrojet to disappear and this should be a normal phenomenon onreal quiet days.

SEVERAL METHODS OF DETERMINING SYNCHRO NIZATION SATELLITE POSITION AND CALCULATION ABOUT PDOP

Sun Hong-wei

1995, 15(3): 245-249. doi: 10.11728/cjss1995.03.245

Abstract(1889) PDF 198KB(1240)

Abstract:
In this paper,several methods of the synchronization satellite positioning with the second pulse in TV-signals transmmitted by communication satellite are introduced,and calculation methods about PDOP in each positioning model are given.Inaddition, some analysis and calculations for some practical problems are also provided.

中国地磁台网简介

1995, 15(3): 250-252. doi: 10.11728/cjss1995.03.250

Abstract(3019) PDF 2360KB(778)

Abstract: