张衡一号感应磁力仪数据闪电哨声波自动识别

张衡一号卫星感应式磁力仪（Search Coil Magnetometer,SCM）探测到了大量的低频电磁波动数据.本文探索从中自动识别闪电哨声波（Lightning Whistler,LW）的算法,相关结果对进一步研究空间天气闪电事件的时空变化规律具有重要研究意义.首先,以20 s的时间窗提取SCM原始波形数据,再对其做短时傅里叶变换（Short-Time Fourier Transform,STFT）得到时频图;接着,以LW在时频图中呈现明显的L形态特征为依据创建LW时频图像数据集,该数据集包括316个LW时频图,8000个非闪电哨声波的时频图;再对时频图像进行灰度化处理和尺度缩放处理以降低计算维度,同时增强闪电哨声波特征;通过设计模糊卷积核,对图像进行卷积计算以滤除大量阶跃边缘信息的影响;基于LW的形态特征设计L形态卷积核,对图像进行卷积处理以进一步增强图像中的L形态特征.最后,将增强后的L特征图输入支持向量机（Support Vector Machines,SVM）进行分类识别.大量数据处理实验结果表明：本文提出的闪电哨声波自动识别方案有效,其识别效果在精度、召回率、F1值（F1 score）和接受者操作特性曲线面积（Area Under Curve,AUC）指标上均达到94%以上.

     

On the structure of ducts for mid-latitude whistlers and their ionospheric transmission as deduced from the ground-based direction finding

The ground-based direction finding carried out at Ceduna, Australia (L=1.93) has yielded the structure for mid-latitude whistlers and their duct ionospheric transmission mechanism. It is found that the ducts tend to take place (or be formed) at the same latitudes and that such sheet-shaped duct includes some inhomogeneities within it which act as field-aligned ducts.     

Deuteron whistlers in the outer ionosphere

Summary Upgoing and downgoing deuteron whistlers were found on VLF records made by Interkosmos 5, 14 and 19 satellites even at heights below 1000 km. To account for them, a slight admixture ofD ⁺ ions has been introduced into the ionospheric plasma model with the usual content of only three ion speciesH ⁺,He ⁺ andO ⁺. Relations derived for the calculation of characteristic frequencies in a five-component plasma (e,H ⁺,D ⁺,He ⁺,O ⁺) are given as well as the values of characteristic frequencies calculated on this basis. The observed features of upgoing and downgoing deuteron whistlers could be explained by the calculation results, and it is also possible to formulate some conclusions for the purposes of plasma diagnostics.

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mu um, anmau a ma u u, u a a nmua m 5, 14 u 19 a ma ¶rt;a 1000 . u u a ¶rt;a ¶rt; u na ¶rt;au uH ⁺,He ⁺,O ⁺ aa nuD ⁺ u. m mm ua nma ¶rt;a ¶rt; aamumuu amm ¶rt;a ¶rt;u na. uu aamumuu amm nuu um a¶rt;a mu ¶rt;mu um. a m ¶rt; unam aamumuu ¶rt;mu um ¶rt; u¶rt;au naam na.

     

Seismic refraction problem in anisotropic media of the cretaceous plateau in czechoslovakia

Summary Media with a distinct anisotropy make application of the refraction method for seismic exploration rather complicated. Velocity data obtained by seismic shooting, sonic log and laboratory measurements of borehole cores have been studied in the region of the Bohemian Cretaceous and interpretation problems of refraction have been analysed. Experience has shown that in such complicated anisotropic media the reflection method in the CDP modification has proved to be much more suitable.Paper was presented at the workshop meeting Seismic Waves in Laterally Inhomogeneous Media, Liblice 1978.     

On the determination of propagation paths of mid-latitude whistlers for purposes of estimating the magnetospheric electron density

Zusammenfassung Mit dem Ziel das Profil der magnetosph?rischen Elektronendichte auf Grund einj?hriger Beobachtungsreihe der Station Panská Ves zu bestimmen, wurden M?glichkeiten von Ermittlung des tats?chlichen Ausbreitungsweges von Whistlern untersucht, die in den mittleren Breiten w?hrend des Minimums der Sonnenaktivit?t beobachtet wurden. Da die beobachteten Whistler keine “nose frequency” aufweisen, gründete sich die Bestimmung des Ausbreitungsweges auf Messungen der Dispersion auf 10 und 4 kHz, ?hnlich wie bei der Extrapolationsmethode der “nose frequency” [4]. Die gewonnenen Resultate zeigen, dass es m?glich ist, die Ausbreitungswege einer grossen Anzahl von Ein-Sprung-Whistler mit genügender Genauigkeit zu bestimmen. Alle auf diese Weise ermittelten Ausbreitungswege fallen in den BreitenbereichФ ₀=38°−56°, was der bekannten Tatsache entspricht, dass man verwendbare Whistler-Komponenten bis zu einer Entfernung von 1000 km vom Endpunkt ihres Ausbreitungsweges beobachten kann. Die analysierten Whistler entsprechen den unter Voraussetzung einer konstanten Elektronendichte in der H?he der Basis der Magnetosph?re (700 km) berechneten theoretischen Modellen. Unter diesen Bedingungen zeigte es sich als m?glich, alle analysierten Whistler zur Bestimmung des Profils der magnetosph?rischen Elektronendichte zu gebrauchen. Trotz aller Vereinfachungen, die bei der Konstruierung von Modellen angewendet wurden, ist es also m?glich, vernünftige Werte der Elektronendichte für den Breitenbereich L=1,5–3 unter Anwendung von Whistler-Beobachtungen aus einer einzigen Station in mittleren Breiten zu gewinnen.

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Address: Bočni II, Praha 4-Spořilov.     

Ion whistlers in mid-latitude trough of light ions

Summary In the set of VLF data from the Interkosmos-14 satellite (launched on 11 December 1975 with apogee height of 1707 km, perigee 345 km and inclination 74°) as received in direct telemetry transmissions at the Observatory Panská Ves (Czechoslovakia), ion cyclotron whistlers were found at unusually high geomagnetic latitudes. These whistlers indicate a marked decrease of proton density in the close vicinity of the satellite with increasing geomagnetic latitude. It appeared, moreover, that proton whistlers at higher geomagnetic latitudes even sensitively reflected the rapid changes of plasma parameters within the region of the mid-latitude trough of light ions.     

On the twilight sky color as observed from the ‘Soyuz-5’ spacecraft

Summary A comparison of the results of visual observations and objective colorimetry of the twilight aureole is made. It is shown that the color picture of the aureole is informative with regard to the composition of the atmosphere.     

Equatorial field-aligned irregularities deduced from the echo-train and hybrid whistlers

Summary Equatorial field-aligned irregularities have been studied by using low-latitude echotrain and hybrid whistlers observed at Sakushima Station (geomag. lat. 24°). The structure is discussed in relation to the propagation mode trapped by field-aligned irregularities. We then find that the field-aligned irregularities responsible for the trapping of low latitude whistlers are of such small dimension as the HF ducts.     

Two types of ELF hiss observed at Varanasi, India

The morphology of ELF hiss events observed at low-latitude ground station Varanasi (L = 1.07, geomagnetic latitude 14°55′N) are reported, which consist of two types: (1) events which propagated in ducted mode along the geomagnetic field line corresponding to observing station Varanasi and (2) events which propagated in ducted mode along higher L-values (L = 4–6), after reaching the lower edge of ionosphere excite the Earth-ionosphere wave guide and propagate towards equator to be received at Varanasi. To understand the generation mechanism of ELF hiss, incoherent Cerenkov radiated power from the low latitude and middle latitude plasmasphere are evaluated. Considering this estimated power as an input for wave amplification through wave-particle interaction, the growth rate and amplification factor is evaluated which is too small to explain the observed wave intensity. It is suggested that some non-linear mechanism is responsible for the generation of ELF hiss.     

Pearl-type micropulsations at mid-latitude; their relation to whistlers,solar and geomagnetic activity as well as ionospheric absorption

The occurrence of pearl-type (Pc 1) micropulsations recorded at the mid-latitude station Nagycenk (Hungary) during a half solar cycle showed a quite regular variation on this long time scale. Around solar activity maximum, the number of days with Pc 1 occurrence was rather low, while it began to increase during medium solar activity rising to a maximum around solar activity minimum. Pc 1 pulsations have been analyzed in relation to further parameters and on a shorter time scale, too. Based on data of 2 years with maximum Pc 1 occurrence (around solar activity minimum in 1985 and 1986), a seasonal variation was also found. Additionally, it was confirmed that pearl-type micropulsations might frequently occur, on and after days, with geomagnetic disturbances. At Nagycenk, the selected geomagnetic disturbances were generally associated with an increased ionospheric absorption of radio waves caused by enhanced ionization due to particle precipitation from the magnetosphere into the lower ionosphere. Whistler observations carried out at Panska Veš (a station in the Czech Republic) showed a significant whistler activity connected with these geomagnetic disturbances, however, no after-effect appeared in whistler activity. One of the main goals of the present study was to find a relationship between Pc 1 pulsations and whistlers. Results revealing an increased whistler activity associated with Pc 1 occurrences confirm our previous findings rather convincingly. The latter ones hinted at the probability that certain magnetospheric configurations, e.g. geomagnetic field line shells and whistler ducts are closely connected, as similar positions of the two structures were found within the magnetosphere when characteristics of Pc 3 pulsations and whistlers were analyzed.     

Dynamics of the plasmasphere in the dusk sector as observed in the outer ionosphere

Summary Direct measurements of the thermal plasma parameters in the topside ionosphere reveal variations of the plasmasphere boundary in the dusk sector. The ACTIVE satellite's near-polar orbits at altitudes of 500 – 1800 km around winter solstice 1989 were used to study the bulge region of the plasmasphere during intervals with different levels of geomagnetic agitation. The narrow, sharply defined trough in electron concentration corresponding to the plasmapause under quiet conditions situated at L = 6 – 7 moved to lower L-values with increasing geomagnetic activity. This narrow trough can be found in all main ion constituents. During periods of moderate geomagnetic activity, following the onset of a weak magnetic storm, a portion of the plasmaspheric bulge region was separated from the main plasmaspheric body. This can be seen in the outer ionosphere as an inner narrow trough at lower L-value. Troughs in light ions need no longer coincide with this in electron concentration. He⁺ is the most sensitive constituent reflecting the dusk sector plasmaspheric situation at this altitude.Dedicated to the Memory of Professor Karel P     

基于电磁卫星的闪电哨声波智能检测算法的研究进展

闪电哨声波作为探索空间物理环境的重要媒介,淹没在海量的电磁卫星数据中.近年来随着计算机视觉和深度学习等人工智能技术的发展,从电磁卫星的存档数据中自动检测闪电哨声波的算法取得了一定的效果.本文对近年来闪电哨声波智能检测算法的文献进行了整理和总结.首先,阐述闪电哨声波在电磁卫星数据中呈现的时频特征和类型;然后,介绍了闪电哨声波智能检测算法的流程并从闪电哨声波的特征提取、分类和定位三个方面对主要的智能检测算法进行归纳、总结和评述;其次,简述了闪电哨声波智能检测模型的评价指标;接着,在张衡一号（ZH-1）卫星的磁场数据上对三种典型的闪电哨声波智能检测算法进行复现,并对三种算法的优缺点进行了较深入的分析;最后,对基于电磁卫星的闪电哨声波智能检测的研究领域进行总结和展望.

     

On the occurrence and characteristics of intense low-altitude electric fields observed by Freja

High-resolution measurements by the double probe electric field instrument on the Freja satellite are presented. The observations show that extremely intense (up to 1 V m⁻¹) and fine-structured (<1 km) electric fields exist at auroral latitudes within the altitude regime explored by Freja (up to 1700 km). The intense field events typically occur within the early morning sector of the auroral oval (01-07 MLT) during times of geomagnetic activity. In contrast to the observations within the auroral acceleration region characterized by intense converging electric fields associated with electron precipitation, upward ion beams and upward field-aligned currents, the intense electric fields observed by Freja are often found to be diverging and located within regions of downward field-aligned currents outside the electron aurora. Moreover, the intense fields are observed in conjunction with precipitating and transversely energized ions of energies 0.5-1 keV and may play an important role in the ion heating. The observations suggest that the intense electric field events are associated with small-scale low-conductivity ionospheric regions void of auroral emissions such as east-west aligned dark filaments or vortex streets of black auroral curls located between or adjacent to auroral arcs within the morningside diffuse auroral region. We suggest that these intense fields also exist at ionospheric altitudes although no such observations have yet been made. This is possible since the height-integrated conductivity associated with the dark filaments may be as low as 0.1 S or less. In addition, Freja electric field data collected outside the auroral region are discussed with particular emphasis on subauroral electric fields which are observed within the 19–01 MLT sector between the equatorward edge of the auroral oval and the inner edge of the ring current.     

On some types of gravity anomalies

Summary The gravity anomaly is a matter of convention. So far, only mixed gravity anomalies have been used. However, if in the future we shall have a sufficiently accurate geoid map covering the entire Earth's surface, it might be convenient to apply another type of gravity anomaly, as suggested Pellinen[1]. The object of this paper is to analyse this question with respect to the solution of the problems of physical geodesy.     

Application of matched filtering and parameter estimation technique to low latitude whistlers

The Matched Filtering and Parameter Estimation (MFPE) technique developed for the analysis of mid/high latitude whistlers has been extended to analyze whistlers recorded at low latitude ground station Varanasi, India (geomagnetic latitude 14° 55′ N, longitude 153° 59′ E, L=1.07). Some of the whistlers recorded at Varanasi are found to have propagated along higher L-values (L>2). It has been argued that these whistlers after exiting the ionosphere have propagated towards the equator in the Earth-ionosphere waveguide. Trace splitting is observed below the nose frequency and above 2.0 kHz, a result in agreement with mid/high latitude whistlers. The trace splitting structure revealed by MFPE demonstrates the complexities of whistler wave propagation and is quite helpful in deriving information about high resolution features of the duct structure. The banded features observed in the dynamic spectrum are clearly seen in the output of the matched filter. The observed banded features may arise due to interference between the wavelets propagating in the duct/waveguide.     

The Sumatra tsunami of 26 December 2004 as observed in the North Pacific and North Atlantic oceans

The M _w=9.3 megathrust earthquake of December 26, 2004 off the coast of Sumatra in the Indian Ocean generated a catastrophic tsunami that caused widespread damage in coastal areas and left more than 226,000 people dead or missing. The Sumatra tsunami was accurately recorded by a large number of tide gauges throughout the world's oceans. This paper examines the amplitudes, frequencies and wave train structure of tsunami waves recorded by tide gauges located more than 20,000 km from the source area along the Pacific and Atlantic coasts of North America.     

Magnetotail response during a strong substorm as observed by GEOTAIL in the distant tail

Simultaneous energetic particle and magnetic field observations from the GEOTAIL spacecraft in the distant tail (X_GSM -150 Re) have been analysed to study the response of the Earths magnetotail during a strong substorm (AE 680 nT). At geosynchronous altitude, LANL spacecraft recorded three electron injections between 0030 UT and 0130 UT, which correspond to onsets observed on the ground at Kiruna Ground Observatory. The Earths magnetotail responded to this substorm with the ejection of five plasmoids, whose size decreases from one plasmoid to the next. Since the type of magnetic structure detected by a spacecraft residing the lobes, depends on the Z extent of the structure passing underneath the spacecraft, GEOTAIL is first engulfed by a plasmoid structure; six minutes later it detects a boundary layer plasmoid (BLP) and finally at the recovery phase of the substorm GEOTAIL observes three travelling compression regions (TCRs). The time-of-flight (TOF) speed of these magnetic structures was estimated to range between 510 km/s and 620 km/s. The length of these individual plasmoids was calculated to be between 28 Re and 56 Re. The principal axis analysis performed on the magnetic field during the TCR encountered, has confirmed that GEOTAIL observed a 2-D perturbation in the X-Z plane due to the passage of a plasmoid underneath. The first large plasmoid that engulfed GEOTAIL was much more complicated in nature probably due to the external, variable draped field lines associated with high beta plasma sheet and the PSBL flux tubes surrounding the plasmoid. From the analysis of the energetic particle angular distribution, evidence was found that ions were accelerated from the distant X-line at the onset of the burst associated with the first magnetic structure.     

Thermal features at Volcanoes in the cascade range,as observed by aerial infrared surveys

There have been no substantial changes in the thermal patterns at the summit of Mount Rainier in the period September 1964–September 1966, within the detection limits of the infrared instrumentation. Some differences in radiance are attributed to differences in snow cover. The highest apparent temperature is at a snow-free area on the west flank of the summit cone, several hundred feet below the west crater rim. An anomaly at this site was recorded on both infrared surveys, but no prior reports of thermal activity here have been made by ground parties. Other anomalous thermal zones at the summit are on the northern quadrants of both crater rims. A very small, low-temperature fumarole reported on Mount Adams was not detected, nor were any other thermal manifestations recorded. One anomaly consisting of a close-spaced cluster of thermal spots was detected at The Boot on Mount St. Helens and corresponds to a known fumarole area. The only thermal feature seen on Mount Shasta is near the summit at a thermal spring that has been observed by many climbers. Two anomalies were found on the north flank of Lassen Peak. Thermal activity had not been previously reported at either site, though one is in a known solfatarized area. No ground investigation has been made at the other location. Much of the other thermal activity in the Lassen Peak area is in the northeast quadrant of Brokeoff Caldera. Most of these features are well documented in the literature; others not previously described are in fairly accessible areas and doubtless result from springs and fumaroles related to Brokeoff Caldera.