空间科学学报

1994 Vol. 14, No. 2

Previous Issue | Next Issue

Select articles

Display Method:

Cover

A MODEL FOR SIMPLE SPIKES OF SOLAR HARD X-RAY BURSTS

Zhang Jie, Zhang He-qi, Zhou Al-hua

1994, 14(2): 85-92. doi: 10.11728/cjss1994.02.085

Abstract(2064) PDF 567KB(911)

Abstract:
Based on the time profiles of 103 strong hard X-ray burst events (their peak rattes are more then₆₀₀₀ c/s according to Hard X-ray Burst Spectrometer) observed by GRS (γ-ray Spectrometer) aboard on SMM (Solar Maximum Mission) satellite from Feb. 1980 to Dec. 1982, it is identified that 24 of them contain the simple impulsive spikes characterized by large amplitude and smooth time profile. The statistical results of the 24 simple spikes in 54-100keVenerge range show that: 1) the spike time profiles' rising slopes correlate well with the falling slopes, and correlation coefficient is about 0.80. 2) rising slope is slightly larger than falling slope, and their averge ratio is about 1.37. Meanwhile, a standard spike is used for quantitative analyzing, whose rising phase characteristic time is about 12.7s and falling phase is 17.4s according to the mean value of the slopes. It then is concluded that the acceleration region continously and symmetrically inject energetic electrons into the loop, and trapplus-precipitation model in strong whistler scattering limit is a proper hard X-ray emission model.

PROPAGATION OF ALFVÉN WAVES IN HELIOSPHERIC MERIDIAN

Lu Jian-yong, Wei Feng-si, Huang Tian-qiao

1994, 14(2): 93-100. doi: 10.11728/cjss1994.02.093

Abstract(2281) PDF 512KB(1079)

Abstract:
Using the WKBsolutions of incompressible Alfvén waves, it is investigated that the propagation of Alfvén waves in the background solar wind with a helmet-shaped current sheet obtained by a time-dependent, two dimensional MHD numerical simulation. The results show that: (1) With increasing heliospheric distance, the Alfvénic magnetic amplitude b will decay Tepidly. Near the heliospkeric sheet, the more slowly of the decay, so that the amplitude of b is almost equal everywhere at large distances. (2) Within several solar radii, the velocity fluctuations reach rapidly the maximum at all latitudes, and after that begin to decay gradualy with increasing distances. At large distances the amplit U de of u over solar polar is a little larger than near the current sheet. (3) With increasing heliospheric distance, the relative magnetic field b/Bwill rise. Over the solar polar the b/B will increase much more slowly than near the current sheet, but above several solar radii, the values of b/B at all latitudes will no longer increase obviously with increasing distance, that is to say, the evolution of the flutuations will reach the so called "saturations", this result may be an important support for Alfvén wave acceleration of the solar wind. Another important result is that near the heliospheric current sheet, b/B > 1 so that Alfvénic fluctuations will be main maglletic field compositions at large distance regions. (4) Near the heliospheric current sheet, the values of the relative velocity fluctuation u/U are the largest and decrease most repidly, instead u/U varies vety slowly over the polar. Within several solar radii, the u/U at all latitudes rapidly becomes vary small, after that at almost same slope and same value, decreases very slowly with increasing distance. Above results show firstly that the propagation nature of polar Alfvén waves is different to that near the heliospheric current sheet.

CHAOTIC BEHAVIOUR OF MAGNETOSPHERE REVEALED BY AE INDEX

Gao Yu-fen, Zhou Rong-mao

1994, 14(2): 101-108. doi: 10.11728/cjss1994.02.101

Abstract(2208) PDF 517KB(869)

Abstract:
Nonlinear predictive error of a time series can be used to distinguish chaos from randomness for a dynamical system which generates the series. Based on this, we analysed a time series of AEindex (from 12h, Jan. 30, 1982) with a resolution of one min and 15000 data points. At first, using one part of the data, a wide predictive model is constructed. The model varies from nonlillear deterministic extreme to the linear stochastic extreme. Then another part of the data is Predicted by this model. The results of predictive error show that the magnetospheric process discribed by AEindex displays a chaotic behaviour. Using the same data and the method of time delay reconstructing phase space, the correction dimension of the attractor is computed, it is about 2.5.

THE EFFECTS OF EQUIVALENT THICKNESS AND DRIFT VELOCITY ON SCINTILLATION POWER SPECTUM IN IONOSPHERIC IRREGULAR STRUCTURE

Chen Zhong-sheng, Zhou Yong

1994, 14(2): 109-115. doi: 10.11728/cjss1994.02.109

Abstract(2200) PDF 439KB(633)

Abstract:
By use of the Fourier power expression of scintillation intensity of thin phase screen with limited thickness L, which is derived from principle theory of diffraction, the effects of the equivalent thickness L and the drift velocity V on the Fourier power spectum are studied. The results show that, as L increases, the Fresnel oscillation amplitude decreases and the Fresnel radius remains unchanged; as V increrases, the Fresnel oscillation amplitude remains unchanged and tEe Fresnel radius increases. The ratio of sequent frequences corresponding to the minimum values of poker is 1:2:3:.:n, not √2:√3:…:√n this is in good agreement with the observationa .data. Comparing the computer comulation results of power spectum wih observational data, both the,values of equivalent thickness and me drift velocity of real ionospheric irregular structure are obtained.

NUMERICAL SIMULATION OF IONOSPHERIC STRUCTURE BELOW F₂ PEAK

Zhang Shun-rong, Huang Xin-yu

1994, 14(2): 116-124. doi: 10.11728/cjss1994.02.116

Abstract(2074) PDF 2824KB(1200)

Abstract:
Taking account of the photo-chemical reactions and the transport processes induced by diffusion and neutral wind, a one-dimensional and time-dependent numerical model for the ionospheric profile is established, in which stable and metastable atomic ions [O⁺(⁴S), O⁺(²D) and O⁺(²P)]and molecular ions (O₂⁺, NO⁺ and N₂⁺) are involved. Based on the model, the ionospheric morphology and related processes at WUCHANG (30.5°N, 114.4°E) in the region below the F₂ peak, especially. within the E/F and F₁/F₂ valleys, are discussed, and the main results are summarized as follows:(1) With respect to atomic ions, the chemical reactions and the transport process for O⁺(⁴S) only are responsible for a shallow F₁/F₂ valley; the O⁺(²D)Patticipated reactions are more favourable to form a deep one conversely, O⁺(²P), when present, is an unfavourable factor for ie valley formation. As for molecular ions, the transport induced by neutral wind is also beneficial for a deep valley. (2) The atomic-molecular ions transit level is located at about 180-190 km with a larger value for morning and evening hours only above which the linear assumption of the loss rate is valid in the traditional continuity epuation with respect to electrons.(3) The widest F₁/F₂ valley occurs at ¹¹h (LT), and the deepest Due at local noon. The E/F valley width is generally about 20-30km for low solar activity and 25-45km for high one, and the morning and evening values are 10-20km larger. (4) O₂⁺ with a double-peak profile is the most important composition in for ining Eand F₁ ledges. Its low peak forms E-layer, while the upper one, in combination with NO⁺ contribution, makes up F₁-Layer.Good agreements are found between the simulated and the observational results as a whole. The present model exhibits great potentiality for the study of ionospheric profiles, such as its mathematical description, the ionogram inversion techniques. and also the morphological and related mechanical research for a particular geophysical event.

NONLINEAR INTERACTION EQUATIONS OF INERTIAL GRAVITY WAVES IN A DISSIPATIVE ATMOSPHERE AND THEIR PRELIMINARY DISCUSSION

Yi Fan, Xiao Zuo

1994, 14(2): 125-133. doi: 10.11728/cjss1994.02.125

Abstract(2315) PDF 585KB(1142)

Abstract:
Aset of the interaction equations of inertial gravity waves in a dissipative atmosphere on the basis of the weak nonlinear theory is derived. This work generalizes previous studies by including the effects of spatial propagation, viscous dissipation and continuous spectrum. It is shown that the wave dissipation rate produced by viscosity depends on the spatial scale and propagation direction of inertial gravity waves. Coriolis effect makes the interaction coefficients complex. Starting from the equations we examined the parametric instability of inertial gravity waves. It is indicated that there exists a threshold of primary wave amplitude. The magnitude of the threshold is proportional to the dissipation rate of secondary waves. When the primary wave amptitude exceeds the threshold, the secondary waves grow exponentially.The interaction brings about a variation in the frequencies of the secondary waves. The magnitude of the variation is proportional to the energy density of the primary wave.

ANOMALOUS CHARACTERISTICS OF S_q IN EAST ASIA

Xu Wen-yao, Li Wei-dong

1994, 14(2): 134-143. doi: 10.11728/cjss1994.02.134

Abstract(2419) PDF 633KB(796)

Abstract:
The magnetic records of the world station network during IGY/IGC with additional data at Changchun, Beijing, Shanghai and Lahsa of China have been used to study the characteristics of S_q in East Asia magnetic anomaly region. The results show that the principal harmonics (lst and 2nd harmonics) of S_q have special features different from those in other regions. The amplitudes of Xcomponent in the anomaly region are larger than those at other stations of similar latitude. The latitude of minimums amplitude is lower by 20° , and the minimum value is also smaller. The current intensity caculated on the basis of the data in East Asia region is similar to that from other regions data. However, the geomagnetic latitude of the current focus is lower by 10°. The S_q dynamo current depends on the earth's magnetic field and ionospheric conductivity structure, and the latter is affected by the magnetic field. Consequently, the above-mentioned features of S_q in East Asia region can be attributed to effects of magnetic field on ionospheric dynamo process.Numerial simulations show that the combined effects of the geomagnetic axis tiltand the magnetic anomaly in this region can explain these features of S_q. It is suggested from this study that the magnetic anomaly remarkably affects the electromagnetic environment of the near-earth space.

A NEW METHOD FOR DETERMING THE VELOCITY OF TIDs BASED ON RADIO ASTRONOMICAL OBSERVATIONS

Han Wen-jun, Zhang Xi-zhen, Zheng Yi-jia

1994, 14(2): 144-150. doi: 10.11728/cjss1994.02.144

Abstract(2060) PDF 428KB(833)

Abstract:
When the field of view in metric wave radio telescope observation contains more than three radio sources, considering the effect of antenna tracking to the source, a new method for determing the horizontal velocity of TIDs is presented in this paper. Some calculated examples are given, and the errors induced by this method are discussed.

OBSERVATIONS OF SMALL SCALE WIND SHEARS IN THE MESOSPHERE

Wu Yong-fu

1994, 14(2): 151-156. doi: 10.11728/cjss1994.02.151

Abstract(2155) PDF 399KB(902)

Abstract:
Ten wind profiles were measured in summer 1988 in the upper mesosphere over And ya (69°N) with foil chaff. Anew kind of foil chaff was used then, which covers the height range of 103-85 km. The height resolution of the measurement was 25 m. The measured wind shears are observed to have a multi-layered structure whih has three to nine shear layers. The thickness of these shear layers is usually less than 200m. Very large wind shears as high as 40-90 m/s/km are observed and such large shears are present at various heights in the mesosphere. The strong wind shears revealed in a series of five shear profiles have stable and persistent features with a lifetime of at least 2.5 h, an apparent downward motion of 0.4 m/s, and a maximum shear amplitude of 180 m/s/km.

A METHOD IN DRAWING LIGHT CURVES OF SOLAR FLARES WITH HIGH ACCURACY AND RESOLUTION

Li Zhi, Zhou Wei-hong

1994, 14(2): 157-159. doi: 10.11728/cjss1994.02.157

Abstract(2320) PDF 182KB(934)

Abstract:
In this paper, a new method to draw the light curves for solar flares is proposed. This method is characterized by high accuracy, great speed and flexible handling.

A METHOD FOR REMOVING THE INTERFERENCE AND NOISE ON BACKSCATTER IONOGRAM

Cheng Xiao-mei, Guo Bac-hua

1994, 14(2): 160-162. doi: 10.11728/cjss1994.02.160

Abstract(2215) PDF 204KB(978)

Abstract:
An effective method for removing the ninterference and noise on the backscatter ionogram is proposed and used in a backscatter sounding system. The processing re.sult is given in detail.

STABILITY OF A PENDULUM CONTAINING SLOSHING FLUID AND A FLYWHEEL

Bac Guang-wei

1994, 14(2): 163-168. doi: 10.11728/cjss1994.02.163

Abstract(2019) PDF 399KB(688)

Abstract:
Stability of a pendulum containing sloshing fluid stabilized by a flywheel is investigated in the present paper. Using the envelope method, the stable and unstable domains of the system in the parameterized space are determined and used to discuss the attitude stability of a three-axis stabilized vehicle containing fluid. The stabilizing effectiveness of the flywheel versus variation of the tank's relative position is evaluated.