Towards an accurate real-time locator of infrasonic sources

Infrasonic signals propagate from an atmospheric source via media with stochastic and fast space-varying conditions. Hence, their travel time, the amplitude at sensor recordings and even manifestation in the so-called “shadow zones” are random. Therefore, the traditional least-squares technique for locating infrasonic sources is often not effective, and the problem for the best solution must be formulated in probabilistic terms. Recently, a series of papers has been published about Bayesian Infrasonic Source Localization (BISL) method based on the computation of the posterior probability density function (PPDF) of the source location, as a convolution of a priori probability distribution function (APDF) of the propagation model parameters with likelihood function (LF) of observations. The present study is devoted to the further development of BISL for higher accuracy and stability of the source location results and decreasing of computational load. We critically analyse previous algorithms and propose several new ones. First of all, we describe the general PPDF formulation and demonstrate that this relatively slow algorithm might be among the most accurate algorithms, provided the adequate APDF and LF are used. Then, we suggest using summation instead of integration in a general PPDF calculation for increased robustness, but this leads us to the 3D space-time optimization problem. Two different forms of APDF approximation are considered and applied for the PPDF calculation in our study. One of them is previously suggested, but not yet properly used is the so-called “celerity-range histograms” (CRHs). Another is the outcome from previous findings of linear mean travel time for the four first infrasonic phases in the overlapping consecutive distance ranges. This stochastic model is extended here to the regional distance of 1000 km, and the APDF introduced is the probabilistic form of the junction between this travel time model and range-dependent probability distributions of the phase arrival time picks. To illustrate the improvements in both computation time and location accuracy achieved, we compare location results for the new algorithms, previously published BISL-type algorithms and the least-squares location technique. This comparison is provided via a case study of different typical spatial data distributions and statistical experiment using the database of 36 ground-truth explosions from the Utah Test and Training Range (UTTR) recorded during the US summer season at USArray transportable seismic stations when they were near the site between 2006 and 2008.     

Observations of the solar radio emission with the Callisto spectrometer

In the framework of the program for setting the Callisto spectrometer network into operation, the spectral measurements were carried out at the sites of spectrometer locations in India and Russia in winter 2006. The results achieved at Badary, the site where the Siberian Solar Radio Telescope (SSRT) is located, are presented. The measurements were performed using a broadband log-periodic antenna connected to the Callisto spectrometer developed at the Institute of Astronomy (Zurich). The results of these measurements should explain whether spectral studies at frequencies below 1 GHz can be performed using such antennas or new antennas should be developed. The presented results are compared with the similar results obtained in Switzerland in the frequency intervals of interest for radio astronomy. Concerning electromagnetic noise, Badary is a better site for observing the Sun in the 50–800 MHz frequency range as compared to observatories in Switzerland.     

Physical characteristics of the radio emission of solar coronal holes

This paper presents a brief overview of works dedicated to the studies of solar coronal holes (CH). Special attention is paid to CH studies at millimeter and centimeter wavelengths. The observational data in the millimeter range, combined with satellite observations in the ultraviolet and soft X-ray range, as well as solar eclipse observations of March 29, 2006, at centimeter wavelengths with RATAN-600, provide new results for understanding the physical nature of coronal holes on the Sun.     

Spectral characteristics of large-scale radio emission areas in coronal holes

The spectra of the coronal hole radio emission in solar cycles 23 and 24 have been studied based on RATAN-600 data in the 4–16.5 GHz range at frequencies of 5.7 and 17 GHz and 327 MHz. It has been found that bright features of coronal hole microwave emission at 17 GHz and dark features at 5.7 GHz can exist in coronal holes when the spectral index is 1.25–1.5 in the 6.5–16.5 GHz range; the radio spectrum in this range is flat when coronal holes are indiscernible against the background of a quiet Sun. The possible vertical scale of the solar atmosphere over coronal holes is discussed.     

Crustal structure and accurate hypocenter determination along the Longmenshan fault zone

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Interplanetary scintillations of strong radio sources in the descending phase near the cycle 23 minimum

Observations of interplanetary scintillations of the 3C 298 and 3C 48 radio sources during low solar activity, performed with a BSA FIAN radio telescope at a frequency of 111 MHz, are presented. The radial dependences of the scintillation indices, where the effect of a low-latitude heliospheric current sheet is observed, have been obtained. Based on the scintillation temporal spectra, the solar wind velocity values have been obtained, and it has been indicated that these values are in good agreement with those found using the spaced measurements method.     

Development of solar flares and features of the fine structure of solar radio emission

The reason for the occurrence of different elements of the fine structure of solar radio bursts in the decimeter and centimeter wavelength ranges has been determined based on all available data from terrestrial and satellite observations. In some phenomena, fast pulsations, a zebra structre, fiber bursts, and spikes have been observed almost simultaneously. Two phenomena have been selected to show that the pulsations of radio emission are caused by particles accelerated in the magnetic reconnection region and that the zebra structure is excited in a source, such as a magnetic trap for fast particles. The complex combination of unusual fiber bursts, zebra structure, and spikes in the phenomenon on December 1, 2004, is associated with a single source, a magnetic island formed after a coronal mass ejection.     

利用运动学轨道提高GRACE时变重力场解算

基于变分方程法,本文利用GARCE高精度K波段星间测速数据KBRR,结合德国格拉茨大学发布的运动学轨道和GFZ发布的简动力学轨道作为两种伪观测值,分别解算了2005-2010年60阶全球时变重力场模型Hust-IGG01与Hust-IGG02.通过与GRACE官方机构发布的模型和其他国际主流权威模型进行对比,发现基于运动学轨道结合KBRR解算的模型Hust-IGG01优于基于简动力学轨道结合KBRR解算的模型Hust-IGG02：在重力场系数C₂₀时间序列的统计数据上,Hust-IGG01比Hust-IGG02更接近SLR结果,在如C₆₀、C₇₀、C₈₀以及C₉₀等重力场低阶项上的数学统计均更接近CSR RL05;Hust-IGG01的重力场系数误差分布和GFZ RL05在同一水平,而Hust-IGG02的误差估计过于乐观;Hust-IGG02在主要质量变化区域上存在5%~10%信号低估,而Hust-IGG01能完全达到国际主流机构利用GPS观测数据的解算水平,Hust-IGG01与官方机构CSR、JPL和GFZ最新模型在格陵兰岛的冰川消融年际趋势分别是-125.4、-125.4、-127.3、-124.3 Gt·a^-1,在亚马逊流域的平均等效水高周年振幅分别是17.56、17.40、17.46、17.22 cm,在撒哈拉沙漠的平均等效水高均方差分别是0.87、0.77、1.10、0.87 cm;另外在Hust-IGG01的实际应用上,本文分析了全球32个主要流域质量变化的年际趋势、周年振幅和半周年振幅三种信号模式,统计结果显示Hust-IGG01与CSR RL05结果基本吻合.

     

On the theory of radio frequency emission from macroscopic hypervelocity impacts and rock fracturing

We suggest that the non-Maxwellian plasma produced during the catastrophic collapse of a rock (following, e.g., the impulsive momentum transfer in a collision between a hypervelocity projectile and a target rock, or the sudden failure of a rock specimen under stress) may satisfy the conditions for the onset of an ion-acoustic instability. If these fairly loose conditions are satisfied, the plasma may be the source of the electromagnetic RF radiation which has been detected in several laboratory experiments. The relevance of these results to the RF emissions which are know to accompany some earthquakes is discussed.     

Response of mesospheric ozone to the heating of the lower ionosphere by high-power HF radio emission

We detected a decrease in the intensity of microwave radiation at the atmospheric ozone line at a frequency of 110836.04 MHz during ionospheric modification by high-power HF radiowaves radiated by the Sura Ionospheric Heating Facility. The obtained experimental data allowed us to hypothesize that this effect was caused by the fact that mesospheric ozone was affected by internal gravity waves generated in the E region of the ionosphere during its high-power HF radiowave heating.     

Using genetic techniques to investigate the sources of the invasive alga Caulerpa taxifolia in three new locations in Australia

The invasive green alga Caulerpa taxifolia has gained a high profile due to 'outbreaks' in the Mediterranean and California. During the year 2000 three new discrete locations colonised by abundant C. taxifolia were discovered in New South Wales (NSW), Australia. Sequencing of the internal transcribed spacer (ITS) region of the ribosomal DNA was used to explore the source(s) of these new records, which is an important prerequisite for subsequent environmental management responses. Our results indicate that the NSW C. taxifolia originated from several sources and, hence, through different invasion events. For two of the new records (Port Hacking, Careel Bay) it can be excluded that they are derived from the so-called "aquarium strain" of C. taxifolia, closely related to the invasive Mediterranean populations. Port Hacking is likely to have originated from tropical native populations. However, samples from Lake Conjola cannot be sufficiently distinguished with the applied technique from native C. taxifolia in Moreton Bay and the Mediterranean/"aquarium strain".     

标定水氡观测仪器应注意的问题--如何将仪器K值标定得更准确

论述了水氡观测仪器在标定中应注意的问题,提出了在标定过程中,固体氡放射源与待标仪器的连接方式及吸源时间以多长为最佳的问题。报告建议为减少标准源的外在损失,提高K值的标定精度,在标定仪器时尽可能地采用图6的连接方式和严控或适当缩短吸源的时间。     

Contributions to the spectral theory of seismic sources and determination of the parameters of earthquake foci

A spectral theory of seismic sources is developed which treats earthquake foci as band-pass filters. This concept is applied to focal mechanisms of the type double-couple with moment, and the obtained spectral function of the source is compared with those obtained by other authors. Finally some formulae for the determination of geometric and dynamic source parameters from the bandpass parameters are presented.     

Effective radius of heating of the lower ionosphere by intense shortwave radiation

The results of a theoretical analysis of the radial distribution of electron temperature T _e in the area of heating of the lower ionosphere by intense shortwave radiation are presented. It was established that effective radius r _eff of heating at a certain height may differ significantly from the characteristic radius of illumination of the ionosphere (a) by radiation at this height. At the boundary of the heating area (r = r _eff ), the characteristic radial scale of T _e changes is less than the corresponding scale of changes in the squared amplitude of the radiation electric field, and it is almost independent of the amplitude value; i.e., the formation of a relatively strong T _e gradient at such a boundary is a common feature of heating of the lower ionosphere by intense shortwave radiation.     

GRACE卫星关键载荷实测数据的有效处理和地球重力场的精确解算

首先对美国喷气推进实验室（JPL）公布的2007-06-01～2007-12-31时间段内的GRACE Level 1B卫星GPS轨道位置和速度、K波段系统星间速度、加速度计非保守力以及恒星敏感器姿态实测数据对应进行了轨道拼接、粗差探测、线性内插、重新标定、坐标转换、误差分析等有效处理;其次,基于改进的能量守恒法恢复了120阶GRACE地球重力场,在120阶处累计大地水准面精度为25.313 cm;最后,检验了本文地球重力场模型IGG-GRACE的可靠性,同时分析了IGG-GRACE解算精度在低频部分略优于德国波兹坦地学研究中心（GFZ）公布的EIGEN-GRACE02S地球重力场模型,而在中高频部分略低的原因.     

The long-term simulation of surface SO2 and evaluation of contributions from the different emission sources to Beijing city

With a high-resolution SO2 emission inventory categorized by industries and seasons for Beijing city and gridded meteorological data fields from NCEP, the pollution dispersion model, HYSPLIT4 (Hybrid Single Particulate Lagrangian Integrated Trajectory, version 4), is used to determine the day-to-day variation of surface SO2 in Beijing for 2000 and 2001. Furthermore,the contributions of different emission sources in and around Beijing to the surface SO2 are studied. As shown in comparison with observations, the model does well in simulating the daily variation and seasonal distribution. The model computation of the annual source contributions to Beijing surface SO2 indicates that local emissions from the city give the largest contribution and the sources from the surrounding regions contribute only about 20%. During SO2 polluted or unpolluted days, the contribution from the latter can exceed 30%, and depending upon weather conditions, the contribution may exceed 40%. If the emissions from the surrounding sources during the winter heating season are assumed to be doubled in intensity, their contribution to surface SO2 in Beijing increased from 21% to 35% and 25% to 40% in 2000 and 2001, respectively. Evaluation of 7 types of emission sources identified for Beijing for their relative contribution to the concentration of surface SO2 has shown that area emissions by industrial production and furnaces, though discharging relatively small amounts (less than 1/3 of the total), have the largest contribution to the urban surface SO2, which is the key to the mitigation of the pollutant in the city.     

Dynamics of large-scale ionospheric inhomogeneities caused by a powerful radio emission of the Sura facility from the data collected onto ground-based GNSS network

The measurements of variations in the total electron content of the Earth’s ionosphere along the GPS satellite signal propagation path are described. The signal parameters were measured at a network of receivers at three distant sites: Sura (Vasilsursk), Zelenodolsk, and Kazan. They are arranged along the geomagnetic latitude of the Sura Facility under short-wave radio irradiation of the ionosphere. One feature of the experiment is the crossing of a disturbed region by the radio path between a GPS satellite and Vasilsursk. This resulted from the angular sizes of the Sura array pattern; the radio paths between a GPS satellite and Zelenodolsk and a GPS satellite and Kazan did not cross. Variations in the total electron content of up to 0.15?0.3 TECU were revealed at all three sites during four experimental campaigns (March 2010, March 2013, May 2013, and November 2013). The lateral scale of an ionospheric disturbance stimulated by a high-power radio wave and the velocity of its west-to-east propagation along the geomagnetic latitude were 30–60 km and 270–350 m/s, respectively. A decrease in the total electron content (down to 0.55 TECU) was recorded along the Kazan–Zelenodolsk–Vasilsurks line, which is connected with the solar terminator transit; the lateral scale of the related ionospheric inhomogeneities was ~65–80 km.     

The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation

The effects of cloud shadowing, channelling, cloud side illumination and droplet concentration are investigated with regard to the reflection of shortwave solar radiation. Using simple geometric clouds, coupled with a Monte Carlo model the transmission properties of idealized cloud layers are found. The clouds are illuminated with direct solar radiation from above. The main conclusion reached is that the distribution of the cloud has a very large influence on the reflectivity of a cloud layer. In particular, if the cloud contains vertical gaps through the cloud layer in which the liquid water content is zero, then, smaller more numerous gaps are more influential on the radiation than fewer, larger gaps with equal cloud fraction. At very low solar zenith angles channelling of the radiation reduces the reflection expected on the basis of the percentage cloud cover. At high solar zenith angles the illumination of the cloud edges significantly increases the reflection despite the shadowing of one cloud by another when the width of the gaps is small. The impact of droplet concentration upon the reflection of cloud layers is also investigated. It is found that at low solar zenith angles where channelling is important, the lower concentrations increase the transmission. Conversely, when cloud edge illumination is dominant the cloud distribution is found to be more important for the higher concentrations.     

A hypothesis on the locations of lunar gas venting

Both lunar transient phenomena and ²²²Rn/²¹⁰Po anomalies observed by Apollo-15 and -16 orbital alpha spectrometers display preferences for certain kinds of locations: rims of circular maria and craters with central peaks and/or dark floors. If these classes of observations are due to lunar gas venting, why are these types of locations preferred? The hypothesis offered is that these are locations at which cracks or channels exist extending deep enough into the moon to tap lunar volatile reservoirs. Possible channels include circumferential cracks around circular maria, old lava tubes for dark-floor and volcanic central peak craters, and shattered subsurface rock structure for impact central peak craters.