1992 Vol. 12, No. 3

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THE HEATING MECHANISM AND STABILITY OF THE GIANT POST FLARE ARCH OF 21-22 MAY, 1980
Tang Yu-hua, G. Poletto
1992, 12(3): 161-170. doi: 10.11728/cjss1992.03.161
Abstract(1564) PDF 783KB(844)
Abstract:
It is proposed in this paper that the fast tearing modes in cylindrical geometry is an effective heating mechanism for post-flare coronal arch of 21-22 May,1980 which have remained visible for more than 10 hours after the flare onset.The magnetic energy supplied by tearing modes,corresponding fast tearing modes grow the rate rt and growth time rt-1 are calculated.The MHD equilibrium and stability of the arch are discussed.Main conclutions are as follows:(1)When density of the arch is given by the observational value,for different shearing width,the equilibrium can be made between radiative loss and tearing modes heating by taking different shearing magnetic field.But,in considering that corresponding tearing modes growth rate must be coincide with observation time,only one situation is reasonable.For coronal arch of 21-22 May,ne=1.6×109 cm,only shearing width aa=1.8×108cm(1/10 minal radius of the arch),shearing magnetic field B=18-32×10-4T,rt=1.79×10-5-2.66×10-5s-1,rt-1=15.5-10.4h,this solution is in agreement with observational value.The free energy which supplied by tearing modes can afford the radiative loss.So,fast tearing modes is an effective reasonable heating mechanism for the coronal arch.(2) According to the discussion for MHD equilibrium and stability of the arch,the arch which lasted more than 10 hours,must be in mechanical equilibrium besides the equilibrium between tearing modes heating and radiative loss.The equilibrium conditions are BФ (axis magnetic field of arch)=2Bθ(toroidal field intensity) and (dp/dr)>0.If the equilibrium conditions are satisfied,the arch is in stability for sausage,kink,screw perturbation by the energy principle.The axis magnetic field and toroidal field components can not be observed directly but an average pressure of 1.4 bar in the arch was observed,usually pa (over the major active region)=2 bar.It can be thought that the arch of 12-22 May is in equilibrium condition and in a stable state.(3)According to observation and calculation for 21-22 May arch,when the tearing modes work,the thermal conduction in the coronal arch can be neglected.
2-D STRUCTURE OF SOLAR WIND SPEED AND HELIOSPHERIC CURRENT SHEET
Cai Hong-chang, Wei Feng-si
1992, 12(3): 171-177. doi: 10.11728/cjss1992.03.171
Abstract(1644) PDF 698KB(796)
Abstract:
The two-dimensional structure of solar wind speed with Carrington latitudes and longitudes is studied based on the analyses of the observations of flares,interplanetary scintillations.(IPS),and data from spacecraft and K-coronameter during the period of Carrington rotations 1733-1742.The results show that the structure is asymmetric with respect to the solar equator whatever the large-scale distribution of velocity,high-speed regions,velocity gradient,longitudinal nonuniformity and boundary shape;by comparing the perfect with the actual current sheets and the magnetic fields with the velocity from spacecraft measurements,it can be seen that the low speed regions exist near the current sheet but there is no simple correspondent relationship;the disturbed solar wind has important influence on the 2-D structure of the background solar wind;and significant difference exists between the perfect and the actual current sheets.
TWO-DIMENSIONAL MAGNETOHYDRODYNAMIC EQUILIBRIA IN THE SOLAR CORONA (II)
Liu Hang-yu, Wang Shui, Zheng Hui-nan
1992, 12(3): 178-184. doi: 10.11728/cjss1992.03.178
Abstract(1497) PDF 605KB(734)
Abstract:
Based on a combination of analytical and numerical methods,two-dimensional magneto-hydrodynamic equilibria in the non-uniform gravitational field for the solar corona are discussed.The critical points are carefully treated.The large-scale magnetic structures of corona,which include the closed-field region,the neutral sheet and the open-field region,are obtained.The closed-field region and the neutral sheet constitute a coronal streamer.On the high-and low-latitudes,the radial flow velocity of plasma exceeds the local sound and local Alfvenic velocities beyond several solar radii.The velocity of solar wind reaches 400 km/s at 1 AU.
TRIGGERED MAGNETIC RECONNECTION OF FORCE-FREE FIELDS AND SOLAR FLARES
Li Xing, Hu You-qiu
1992, 12(3): 185-191. doi: 10.11728/cjss1992.03.185
Abstract(1616) PDF 549KB(640)
Abstract:
This paper made a numerical simulation of magnetic reconnection of highly stressed force-free field triggered by an instantaneously forned current sheet,using the multistep implicit scheme.Magnetic reconnection takes place in the non-neutral current sheet between the two fields at first,and then extends toward the for ce-free field region.During the magnetic re-connection,a hightemperature loop structure forms in the force-free field.The mass in the loop flows to the photosphere whereas the mass in the newly emerging field region on the inner side of the loop moves upward.This result agrees with the observation that solar flares occur in the red shift side of the inversion line of H chromospheric Dopplergiram.Magnetic reconnection concentrates mainly in the highly stressed force-free field region on the exterior side of the car-rent sheet.The loop has a higher temperature at its apex and keeps nearly stationary.As the magnetic reconnection proceeds,the gradient of sheared magnetic field component decreases and force-free field factor becomes smaller.The results of this paper may be applied to elucidate single-loop flares.
IONOSPHERIC SCINTILATION OF COSMIC RADIO NOISE
Chen Zhong-sheng, Zhao Fa-xin, Ma Jun
1992, 12(3): 192-24. doi: 10.11728/cjss1992.03.192
Abstract(1677) PDF 1134KB(1057)
Abstract:
This paper gives the relation between the Fourier and Bessel power spectra of ionospheric scintilation and the fluctuations in electron density of irregularities when a thin phase-screen approximation is justifies.And analysed the data obtained by Riometer with narrow lobe-beam antannas.It shows that the Riometer data contain the information of irregularities in the ionosphere,and these data could be used to study the ionospheric scintilation.
A GLOBAL PRIMITIVE EQUATIONS SEMI-SPECTRAL MODEL TO STUDY THE INFLUENCE OF QBO ON PLANETARY WAVE PROPAGATION
Ma Rui-ping, Zhang Yang, Peng Xiao-Ian
1992, 12(3): 205-213. doi: 10.11728/cjss1992.03.205
Abstract(1750) PDF 678KB(924)
Abstract:
A global primitive equations semi-spectral model is used to simulate numerically the influences of Quasi-Binnial Osillation (QBO) of the equatorial stratospheric wind and its corresponding compatible subtropical jet strength on the upward propagation of north hemisphere planetary waves in winter.The results discover there is obvious influence on the upward propagation of the planetary waves and the stratospheric sudden wairming : for the general amplitude waves,wave 1 propagate upward more easily in the easterly phase of QBO than in the westerly phase,but counter to wave 1,the wave 2 propagate upward easily in the westerly phase;for the large amplitude waves,wave 1 create the stratospheric sudden warming faster and create larger warming amplitude in the eaterly phase than in the westerly phase,counter to wave 1,wave 2 create the stratospheric sudden warming more fast and create more large warming amplitude in the westerly phase than in the westerly phase.
MICRO-DISTRIBUTION PATTERNS OF TRACE ELEMENTS IN NANDAN IRON METEORITE
Li Xue-jun, Chai Zhi-fang, Liu Yong-zhong, Chao Zhi-yu, Xiao Ya-nan, Mao Xue-ying
1992, 12(3): 214-221. doi: 10.11728/cjss1992.03.214
Abstract(2064) PDF 702KB(1273)
Abstract:
In this paper the micro-distribution patterns of trace elements in the Nandan iron meteorite are studied by a synchrotron radiation X-ray fluorescence micro-scanning method (SRXRFMS).On the basis of our experimental results the classification,origin,evolution and other aspects are discussed.It seems reasonable that the Nandan iron meteorite should be classified to the group IAB.Further,it might be formed from the source matter with the chondritic composition,which experienced the impact and partial melting.
THE INVERSION OF CURVES OF MINIMUM TIME DELEY OF SWEEP-FREQUENCY HF BACKSCATTER
Zheng Chuan-qing
1992, 12(3): 222-227. doi: 10.11728/cjss1992.03.222
Abstract(1623) PDF 680KB(919)
Abstract:
A method is presented to derive the structure for a quasiparabolic ionospheric layer from the curve of minimum time deley of a sweep-frequency HF backscatter without any requirement of other parameters.Provided that there is a relation between the maximum hight and se-mithickness of the layer,the data of only two points are needed for the inversion.The method is illustrated with some numerical examples.The use of the method in the practice is discussed.
A MULTISTATION OBSERVATION OF LOW-LATITUDE Pc3 GEOMAGNETIC PULSATIONS
Yang Shao-feng
1992, 12(3): 228-234. doi: 10.11728/cjss1992.03.228
Abstract(1528) PDF 570KB(1146)
Abstract:
In this paper the observational information of geomagnetic pulsations at 3 low-latitude stations,Changchun,Beijing,Lanzhou is used to analyse the characteristics of spectrum and polarization for Pc3 pulsations.Based on the nalysis the generation and propagation mechanism of low-latitude Pc3 pulsations are discussed.
SABRE RADAR AND ITS OBSERVATIONS ON Pc5 PULSATION I. THE RESULTS OF STATISTICAL ANALYSIS
Tian Mao, T. K. Yeoman, M. Lester T. B. Jones
1992, 12(3): 235-240. doi: 10.11728/cjss1992.03.235
Abstract(1603) PDF 507KB(675)
Abstract:
It is briefly described of coherent scattering radar SABRE and its working principle in observing Pc5 geomagnetic pulsations.The statistical analysis shows that the occurrence of poleward propagating events peaks near local midnight whereas for equatorward events the occurrence peaks at about 18:00 LT.The statistical results are presented here of the diurnal variation of occurrence frequency,the correlation with geomagnetic activity and the relationship with the background plasma convection pattern for above two types of pulsation events.