Disturbed region and a shock wave driven by a coronal mass ejection

The existence of a disturbed region in front of a coronal mass ejection (CME) has been proved; its variation with increasing CME velocity has been investigated. It has been shown that a plasma density discontinuity, which can be interpreted as a shock wave, is formed in front of the disturbed region at CME velocities that are about or above the local Alfvén velocity. Within the experimental error, the observed shock-front width is estimated to be about the mean free path for proton-proton collisions at distances R < 15−20 R _⊙ from the center of the Sun; i.e., the energy dissipation mechanism in the front is conceivably collisional at these distances.     

On the formation mechanism of the sporadic solar wind

In this paper, we examine the nature of the main source of the sporadic solar wind on the Sun: coronal mass ejections (CMEs). Analysis of data from Mark 3 and Mark 4, the Digital Prominence Monitor (MLSO), and STEREO (EUVI) spacecraft has revealed the existence of two types of CMEs: gradual and impulse. They differ in the place, velocity, and angular size at the instant of their emergence. The source of gradual CMEs is located in the corona, at a distance of 1.1 R ₀ < R ≤ 1.7 R ₀ from the center of the Sun. They start moving from a state of rest, having an angular size ≈15–65° (in the heliographic coordinate system). Impulse CMEs are probably formed under the Sun’s photosphere. This may be due to the supersonic emergence of magnetic tubes (ropes) from the convective zone. The possibility of this phenomenon has been demonstrated earlier in theory. The radial velocity of such tubes at the photospheric level may be 100 km/s or higher; the minimum angular size is ∼1°.     

The main features of solar wind plasma correlations of importance to space weather strategy

In this work solar wind measurements from several spacecraft were used to investigate the correlations of solar wind plasma parameters. These results provide a test of the concept of predicting space weather by monitoring the condition of the solar wind at a large distance (up to 230R_e, the L1 point) upstream from the Earth.We compared the ion flux and bulk velocity time behavior measured by widely-separated spacecraft: the spacecraft pairs INTERBALL-1 and IMP 8 (separations up to 30R_e), INTERBALL-1 and WIND, and IMP 8 and WIND (both with separations up to 250R_e). The average value of the ion flux correlation coefficient is about 0.73. But in some cases the plasma parameters from two spacecraft are very different in both behavior and value, so correlations are very poor.The technique of multifactorial analysis was used to obtain the physical dependences of the correlations on the spacecraft separation and on different plasma and magnetic field parameters. We found that the correlation values have a weak but significant dependence on the separation perpendicular to the Sun–Earth line (YZ_se-separations up to 90R_e).The most important factors influencing the correlation level are density (or ion flux) variability, the direction of the IMF vector to the Sun–Earth line (cone angle), and the solar wind bulk velocity.     

Plasma pressure distribution in the equatorial plane of the Earth’s magnetosphere at geocentric distances of 6–10<Emphasis Type="Italic">R</Emphasis><Subscript><Emphasis Type="Italic">E</Emphasis></Subscript> according to the international THEMIS mission data

The structure of the averaged plasma pressure distribution in the plasma ring around the Earth at geocentric distances of ∼6–10R _E has been determined. The distribution function moments measured on the international THEMIS mission satellites have been used. The plasma pressure distribution in the equatorial plane at 15R _E > X_SM > −15R _E and 15R _E > Y_SM > −15R _E has been statistically studied. The radial dependence of the plasma pressure at the day-night and morning-evening meridians has been analyzed. It has been indicated that the plasma ring around the Earth has a structure, which is close to being azimuthally symmetric. The achieved results have been compared with the pressure distributions obtained previously. It has been indicated that in the overlapping regions, the achieved results agree with the previously obtained data within the pressure determination errors.     

Diagnostics of solar wind streams and their sources in the solar corona

The studies are based on the experimental mass sounding of the interplanetary plasma near the Sun at radial distances of R = 4−70 R _S, performed at Pushchino RAO, Russian Academy of Sciences, and on the calculated magnetic fields in the solar corona based on the magnetic field strength and structure measured on the Sun’s surface at J. Wilcox Solar Observatory, United States. The experimental data make it possible to localize the position of the boundary closest to the Sun of the transition transonic region of the solar wind in the near-solar space (R ≈ 10−20 R _S) and to perform an interrelated study of the solar wind structure and its sources, namely, the magnetic field components in the solar corona based on these data. An analysis of the evolution of the flow types in 2000–2007 makes it possible to formulate the physically justified criterion responsible for the time boundaries of different epochs in the solar activity cycle.     

The response of thunderstorm VLF radio noise to solar activity according to observations in Yakutsk

The relation between the long-term variations in the thunderstorm VLF radio noise intensity and solar activity in 1979–2006 has been studied. The sunspot number (the Wolf number) was used as a parameter characterizing solar activity. The intensity of VLF noise registered in Yakutsk characterizes thunderstorm activity in Eastern Siberia (0100–0500 UT) and in the African thunderstorm center (1300–1700 UT). Using the results of a correlation analysis, it has been found that thunderstorm activity in Eastern Siberia and in the African world centre is in antiphase with a change in the sunspot number. The highest anticorrelation coefficients between solar activity and thunderstorm discharge intensity were obtained for thunderstorms in Eastern Siberia. In this case the maximal correlation coefficients (R = −0.59 and −0.75) were obtained for the average monthly values of the VLF radio noise intensity in August, measured at 0400 UT and 1600 UT, respectively.     

EISCAT measurements of the solar wind

EISCAT observations of interplanetary scintillation have been used to measure the velocity of the solar wind at distances between 15 and 130R (solar radii) from the Sun. The results show that the solar wind consists of two distinct components, a fast stream with a velocity of 800 km s^–1 and a slow stream at 400 kms^–1. The fast stream appears to reach its final velocity much closer to the Sun than expected. The results presented here suggest that this is also true for the slow solar wind. Away from interaction regions the flow vector of the solar wind is purely radial to the Sun. Observations have been made of fast wind/slow wind interactions which show enhanced levels of scintillation in compression regions.     

Ionospheric index of solar activity based on the data of measurements of the spacecraft signals characteristics

The method for estimating an ionospheric index of solar-activity (IISA) based on the processing of spacecraft radio signals is suggested. The IISA values have been obtained by comparison between the measured and calculated variations of radio-signal characteristics. To calculate the variations of radio-signal characteristics, the straight rays approximation and the solar-activity index (Wolf numbers W and/or values of F_10.7 solar flux) as a control parameter of the ionospheric model have been used. The suggested method was tested using spacecraft radio signals from the radio-navigation system “CIKADA”. The reduced differences of phases (ΔΦ) for frequencies 150 and 400 MHz were measured and the same characteristics were calculated by integration along the ray of radio-wave propagation between the receiver and the satellite. The IRI-95 has been used as a background ionospheric model. The satellite co-ordinates were determined using the orbit parameters recorded in the navigation messages. Minimization of the difference measured and calculated ΔΦ using arbitrary time steps, or during whole time intervals of observation, gives the IISA corresponding the satellite pass. Daily IISA values were obtained by averaging over all communication contacts during a day (20–30 passes). Testing this approach based on the measurements during March/April 1997, 1998, shows that on magnetically quiet days differences between IISA and the primary solar activity indices are about 5%.     

A study of the effect of different solar wind streams on spacecraft functioning

The paper suggests that spacecraft equipment failures in the near-Earth environment may be caused by one of the following types of streams coming to the Earth’s orbit: (a) slow solar wind in the streamer belt or chains; (b) sporadic solar wind; (c) proton flux with an energy of E > 60 MeV. The laws of solar-terrestrial physics derived to date allow sufficiently reliable determination of the sources of these streams on the Sun as well as fairly precise calculation of their parameters and time of arrival at the Earth’s orbit. We have concluded that spacecraft maintenance and extension of their service life require timely and fairly accurate information regarding the onset of an adverse environmental effect on spacecraft. A successful solution to the problem depends mainly on the current state of the art of research and development in solar-terrestrial, ionospheric, and magnetospheric physics.     

Analytical model of the near-Earth magnetopause according to the data of the Prognoz and Interball satellite data

Based on the magnetopause observations near the Earth by the Prognoz/Interball satellites in 1972–2000, the empirical model of this boundary has been proposed, and the magnetopause behavior at different parameters of the oncoming solar wind has been studied. For the first time, it has been detected that the Earth’s magnetopause is compressed by ∼5% in the direction perpendicular to the plane including the vectors of the solar wind velocity and IMF. At the same time, any dependence of the subsolar magnetopause position on the IMF B _z component has not been revealed in the Progrnoz/Interball data. The proposed magnetopause model can be used to model the position and shape of the near-Earth bow shock.     

Source parameters of bohai earthquake, July 18, 1969 and yongshan earthquake, May 11, 1974 determined by synthetic seismograms of teleseismic P waves

The source parameters of the Bohai Sea earthquake, July 18, 1969 and Yongshan, Yunnan earthquake, May 11, 1974 were determined by full — wave theory synthetic seismograms of teleseismic P waves. P+pP+sP wereform were calculated with WKBJ approximation and real integral paths. One — dimensional unilateral, finite propagation source was also considered. By trail — and — error in comparing the theoretical seismograms with the observational ones of WWSSN stations, the source parameters were obtained as follow: for Bohai earthquake, φ=195°, δ=85°, λ=65°,M _o=0.9×10¹⁹Nm,L=59.9km.V _R=3.5km/s, ∧ _R =160°; for Yongshan earthquake, φ=240°, δ=80°, ∧=150°,M _o=1.3×10¹⁸Nm,L=48.8km,V _R=3km/s, ∧ _R =−10°, where φ is strike, δ dip angle, λ slip angle,M _o seismic moment,L rupture length,V _R rupture propagation speed. As III type fractures the faulting propagated along the fault planes, and ∧ _R is the angle from the strike to the propagation direction. Yongshan earthquake showed complexity in its focal process, having four sub—ruptures during the first 60 seconds. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 1–8, 1991.     

M L Determination for Local and Regional Events Using a Sparse Network in Southwestern Germany

A method for the determination of consistent local magnitude M _L values (Richter scale, or M _WA) for earthquakes with epicentral distances ranging from 10 km through 1000 km is demonstrated. The raw data consists of nearly 1300 amplitude readings from a network of six digital seismographs in Baden–Württemberg (Southwestern Germany) during 26 months starting in 1995, later extended by another 1000 amplitude readings until 1999. Relying on most of the basics introduced by C.F. Richter a three-parameter attenuation curve (distance correction, magnitude-distance relation) for Baden–Württemberg and adjacent areas is presented. Station corrections are evaluated and the attenuation curve is calibrated with respect to other agencies for distances greater than 650 km. Reasonable parametrisations are discussed and meaningful error bars are attributed. Finally, a seventh station is incorporated by means of its station correction alone, without needing to update the attenuation curve.     

Properties of wave velocity for two types of granitoids at high pressure and temperature and their geological meaning

The wave velocity for two types of granitoids was measured using the analytic method of full-wave vibration at high pressure and high temperature. The laws of velocity changes for them differ with the pressure boost and temperature rise, and the velocity change of S-type is more violent than that of I-type. The “softening point” of compressional wave velocity (V μ) is also revealed during the measurement for two types of granitoids imitating the pressure and temperature at a certain depth. But the depth of “softening”, V_p after “softening” and the percentage of V_p’s drop around the “sofrening point” for two types of granitoids are obviously different. The depth of “softening” is 15 km approximately and V_p after “softening” is 5.62 km/s for S-type granitoid. But for I-type granitoid the depth of “softening” is 26 km approximately and V_p after “softening” is 6. 08 km/s. Through careful analysis of rock slices after the experiment, it was found that the “softening” of elastic-wave velocity is caused by the partial melting of granite. Combined with the results of geophysical prospecting, these results suggest that the low-velocity layers developing in the interior of Earth crust are related to thc partial melting of different types of granitoids. The formation of the low-velocity layer in the upper-middle Earth crust is closely related to the development of S-type granitoid, but that in the lower Earth crust is closely related to the development of I-type granitoid.     

Quasi-biennial variations of the total solar flux: Their manifestation in variations of the stratospheric wind and the Earth’s rotation velocity

A detailed representation of variations of the total solar flux I has been obtained by analyzing the regular measurements of this flux by the Nimbus-7 and other spacecrafts. In particular, quasi-biennial variations (QBVs) of the monthly average value 〈I〉 and standard deviation sI within a month interval have been revealed. It is remarkable that the QBVs of sI almost coincide in shape with the QBVs of many solar activity and ionospheric indices, and the QBVs of 〈I〉 are almost in antiphase with the variations of sI. The manifestation of the QBVs of 〈I〉 in some processes on the Earth has been already revealed. A relation between the QBVs of 〈I〉 for solar radiation (according to the Nimbus-7 and ACRIM-2 data) and the QBVs of the zonal stratospheric wind near the equator, as well as the QBVs of the Earth’s rotation velocity, has been found. Many of the considered QBV-processes on the Earth are seemingly attributed to the variations of the total solar flux.     

Manifestations of the ray structure of the coronal streamer belt in the form of sharp peaks of the solar wind plasma density in the Earth’s orbit

White corona images are analyzed based on the calibrated data of the LASCO-C2/SOHO instrument (processing level 1) and the solar wind (SW) parameters with hourly and minute resolutions on the Wind spacecraft. The quasistationary events, excluding coronal mass ejections and their manifestations in SW are studied. It has been indicated that the angular dimensions and relative variations in the density of the streamer belt segments remain almost unchanged over the entire distance from the Sun to the Earth’s orbit. In the Earth’s orbit, the ray structure of the belt streamer manifests itself as sharp (with steep fronts lasting several minutes and less) peaks (of several hours in duration) of the solar wind plasma density with maximal values N _max > 10 cm^?3.     

Spatial correlation of shear-wave velocity in the San Francisco Bay Area sediments

Ground motions recorded within sedimentary basins are variable over short distances. One important cause of the variability is that local soil properties are variable at all scales. Regional hazard maps developed for predicting site effects are generally derived from maps of surficial geology; however, recent studies have shown that mapped geologic units do not correlate well with the average shear-wave velocity of the upper 30 m, V_s(30). We model the horizontal variability of near-surface soil shear-wave velocity in the San Francisco Bay Area to estimate values in unsampled locations in order to account for site effects in a continuous manner. Previous geostatistical studies of soil properties have shown horizontal correlations at the scale of meters to tens of meters while the vertical correlations are on the order of centimeters. In this paper we analyze shear-wave velocity data over regional distances and find that surface shear-wave velocity is correlated at horizontal distances up to 4 km based on data from seismic cone penetration tests and the spectral analysis of surface waves. We propose a method to map site effects by using geostatistical methods based on the shear-wave velocity correlation structure within a sedimentary basin. If used in conjunction with densely spaced shear-wave velocity profiles in regions of high seismic risk, geostatistical methods can produce reliable continuous maps of site effects.     

The preliminary interpretation of deep seismic sounding in western Yunnan

The preliminary interpretation of Project western Yunnan 86–87 is presented here. It shows that there obviously exists lateral velocity heterogeneity from south to north in western Yunnan. The depth of Moho increases from 38 km in the southern end of the profile to 58 km in its northern end. The mean crustal velocity is low in the south, and high in the north, about 6.17–6.45 km/s. The consolidated crust is a 3-layer structure respectively, the upper, middle and lower layer. P ₁ ⁰ is a weak interface the upper crust, P ₂ ⁰ and P ₃ ⁰ are the interfaces of middle-upper crust and middle-lower crust respectively. Another weak interface P ₃ ^0′ can be locally traced in the interior of the lower crust. Interface Pg is 0–6 km deep, interface P ₁ ⁰ 9.2–16.5 km deep, and interfaces P ₂ ⁰ and P ₃ ⁰ respectively 17.0–26.5 km, 25.0–38.0 km deep. The velocity of the upper crust gradually increases from the south to the north, and reaches its maxmium between Nangaozhai and Zhiti, where the velocity of basement plane reaches 6.25–6.35 km/s, then it becomes small northward. The velocity of the middle crust varies little, the middle crust is a low velocity layer with the velocity of 6.30 km/s from Jinhe-Erhai fault to the north. The lower crust is a strong gradient layer. There exists respectively a low velocity layer in the upper mantle between Jinggu and Jingyunqiao, and between Wuliangshan and Lancangjiang fault, the velocity of Pn is only 7.70–7.80 km/s, it is also low to the north of Honghe fault, about 7.80 km/s. Interface P_6/0 can be traced on the top of the upper mantle, its depth is 65 km in the southern end of the profile, and 85 km in the northern end. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 427–440, 1993.     

Response of the high-latitude polar ionosphere to changes in the orientation of the Poynting vector near the Earth orbit relative to the geomagnetic moment orientation

The effect of the mutual orientation of the Poynting vector P of the electromagnetic energy density in the solar wind and the vector M of the Earth’s magnetic moment (taking into account its orbital and diurnal motions) on the geomagnetic activity has been examined for the first time using the measurements of the solar wind parameters on the Earth orbit in 1963–2005. The component P _m of the vector P along the vector M is shown to have a pronounced annual variation with the extrema in November and May and a diurnal variation with the extrema at ∼6 and 18 UT. The phases of the variations are shown to be determined only by the geometric parameters and are independent of the sign of the sector structure of the interplanetary magnetic field. The experimental data on the planetary and high-latitude geomagnetic activity, which is a response to changes in the orientation of P relative to M, are presented. The power of the sources of the electromagnetic energy of the solar wind during strong geomagnetic disturbances is also estimated.     

The synodic periods of planets in the solar system and synchronization of the timing of large earthquakes

We report the results from a search for statistically significant (at a significance level of <0.05) periodicities that synchronize the occurrence of large shallow (h ≤ 100 km) earthquakes in the eight world regions with the highest level of seismicity. The periodicities in question include the synodic periods of planets of the solar system (Mercury, Venus, Mars, and Jupiter), as well as the precession period of the lunar orbit. In five of the eight regions we have found statistically significant results for the period T ≈ 780 days, corresponding to the synodic period of Mars. The lunar cycle and the period of Mercury were significant in two regions. These results cannot be accounted for by invoking the disturbing influence of gravitational and tidal forces due to planets other than the Earth. The significant periodicities were used to develop a forecast (for the period 2004–2009) of the most probable time intervals for the occurrence of large earthquakes in four regions: Kamchatka, the South Kurils, northeastern Japan, and the Nankai trough.     

2001年4月2日太阳耀斑及其太阳质子事件的观测结果研究

2001年4月2日, 太阳爆发了一个近年来X射线通量最大的一次耀斑并伴有质子事件, 利用“资源一号”卫星星内粒子探测器和神舟二号飞船X射线探测器的观测资料, 对这一事件的高能粒子响应进行了特例研究. “资源一号”卫星运行于太阳同步轨道, 高度约800km, 和宁静时期的统计结果对比, 这次耀斑后, 星内粒子探测器在地球极盖区（地球开磁场区）观测到耀斑粒子的出现, 这是宁静时期没有的; 神舟二号飞船轨道高度400km, 倾角为42°, X射线探测器在42°中高纬地区也观测到高能电子通量比宁静时明显的增加, 这表明, 太阳耀斑引起的近地空间辐射环境的变化遍及纬度约40°以上的区域, 甚至在40°N附近400 km左右的高度上仍然有响应. 但是, 中高纬度、极光带和极盖区的粒子来源, 加速机制和响应方式却不一定相同, 需要分别讨论. 资料分析和对比还表明, 质子事件的强度并不一定和耀斑的X射线通量成正比, 因此, 近地空间高能粒子对耀斑的响应也不是完全决定于X射线强度.