Polar ionosphere and geomagnetic response for the flux transfer events: A case study

On April 15th 2003, Cluster crossed the dayside magnetopause boundary and observed a series flux transfer events (FTEs) during the interval from 0630 to 0730 UT. During this period, the interplanetary magnetic field (IMF) showed a negative z component and a positive y component. Simultaneous corresponding transient plasma flows were identified in the near-conjugate polar ionosphere by the CUTLASS Finland HF radar, and the geomagnetic field disturbances were observed by the IMAGE ground-based magnetometers. By combing these data and applying the Cooling model, we show that the transient plasma flows and the geomagnetic field disturbances are closely related to the dayside FTEs.     

DEMETER and DMSP satellite observations of the disturbed H/O ratio caused by Earth’s seismic activity in the Sumatra area during December 2004

In the present paper, plasma probe data taken from DEMETER and DMSP-F15 satellites were used to study the ion density and temperature disturbances in the morning topside ionosphere, caused by seismic activity at low latitudes. French DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) micro-satellite mission had been especially designed to provide global scale observations in the topside ionosphere over seismically active regions. Onboard the DEMETER satellite, the thermal plasma instrument called “Instrument Analyser de Plasma” (IAP) provides ion mass and densities, ion temperature, three component ion drift and ion density irregularities measurements. As a part of “Defense Meteorological Satellite Program”, DMSP-F15 satellite is on orbit operation since 1999. It provides ionospheric plasma diagnostics by means of the “Special Sensor-Ion, Electron and Scintillations” (SSIES-2) instrument. We examined few examples of possible seismic effects in the equatorial ionosphere, probably associated with seismic activity during December month in the area of Sumatra Island, including main shock of giant Sumatra event. It is found that the localized topside ionospheric disturbances appear close to the epicenters of certain earthquakes in the Sumatra region. In two cases, ion H⁺/O⁺ ratio rises more than one hour before the main shock, due to the O⁺ density decrease at the winter side of the geomagnetic equator, with longitudinally closest location to the epicenter of the earthquakes. These anomalous depletions in O⁺ density do exist in all cases of SSIES-2 data. Particularly for Sumatra main event, more than one hour after the main shock, we observe large-scale depletion in O⁺ density northward of the geomagnetic equator at winter side hemisphere. Associated with O⁺ depletion, ion temperature latitudinal profile around the geomagnetic equator shows enhanced asymmetry with minimum at the summer side and maximum in positive Ti deviation from mean value at the winter side. This disturbance lasted for more than three hours, later in time observed at the same place by IAP/DEMETER.     

Impact of geomagnetic storm of September 7–8, 2017 on ionosphere and HF propagation: A multi-instrument study

The present study reveals the features of ionospheric parameters variations during the geomagnetic storm of September 7–8, 2017. In particular, parameters of vertical (foF2, foEs) and oblique ionospheric sounding (MOF, modes), absorption level, Total Electron Content (TEC) and particle fluxes at high altitudes were under analysis. The storm was characterized by two Dst-index mimima and can be considered as a sequence of two storms: first - with Dstmin?=??142?nT at 02 UT on September 8th and second - with Dstmin?=??122?nT and at 15 UT on September 8th. It was found that these two storms had different impacts on the ionosphere and HF propagation at mid- and high-latitudes of Northern Hemisphere. The signals of vertical and oblique ionospheric sounding were present in all ionograms before the first storm. Further, at the maximum of the first storm these signals were totally absorbed. Then, before the second storm and during its maximum the signals were detected again in the ionograms due to the low absorption. GOES satellite data showed the significant burst of electrons and protons only during the first storm and small particle fluxes - during the second storm. This feature was also confirmed with GPS data: TEC increased during the first storm and decreased during the second storm.     

基于恒星的电离层成像仪在轨几何定标

三轴稳定的地球静止轨道卫星在轨运行期间温度会有周期性变化.其上装载的远紫外电离层成像仪与卫星之间的热应力变化造成机械传递,导致仪器指向与装星时的初始位置发生偏差.恒星在惯性坐标系中的位置保持不变,可以将其作为电离层成像仪在轨几何定标的定标源.本文建立了基于恒星的电离层成像仪在轨几何定标模型,通过拍摄所筛选恒星图像,得出仪器在轨指向相对于初始值的偏离程度,从而提高电离层成像仪的成像几何精度.通过模拟试验,验证了运用此技术进行在轨几何定标的可行性.研究结果可为电离层成像仪常态化自动在轨几何定标奠定基础.      

旅游者号超轻型飞机的数学模型与计算机绘图

超轻型飞机AD100是我院自行设计的我国第一架鸭式布局旅游机。它由机身、主翼、中翼、前翼、翼尖小翼、起落架以及发动机等部件组成。飞机各个部件的轴测图或各部件组合轴测图以及全机外形图,可在IBM4341计算机上利用双三次B一样条曲面和改进的双主次Coons曲面算法,在TEK618上显示和在TEK4662绘图仪上绘制。本程序可在绘制中随意改变三维空间角度,並能绘制出飞机某部件及其切面图,以便于加工样板和绘制模线。     

F2 layer response to geomagnetic disturbances in Eastern Asia under the low solar activity

In this paper, the peculiarities of ionospheric response to geomagnetic disturbances observed at the decay and minimum of solar activity (SA) in the period 2004–2007 are investigated with respect to different geomagnetic conditions. Data from ionospheric stations and results of total electron content (TEC) measurements made at the network of GPS ground-based receivers located within the latitude–longitude sector (20–70°N, 90–160°Е) are used in this study. Three groups of anomalous ionospheric response to geomagnetic disturbances have been observed during low solar activity. At daytime, the large-scale traveling ionospheric disturbances (LSTIDs) could generally be related to the main phase of magnetic storm. Quasi-two-days wavelike disturbances (WLDs) have been also observed in the main phase independent of the geomagnetic storm intensity. Sharp electron density oscillations of short duration (OSD) occurred in the response to the onset of both main and recovery phases of the magnetic storm in the daytime at middle latitudes. A numerical model for ionosphere–plasmasphere coupling was used to interpret the occurrence of LS TIDs. Results showed that the LSTIDs might be associated with the unexpected lifting of F2 layer to the region with the lower recombination rate by reinforced meridional winds that produces the increase of the electron density in the F2 layer maximum.     

On the application of Exploratory Data Analysis for characterization of space weather data sets

This paper presents an overview of the mathematical foundations for techniques in Exploratory Data Analysis (EDA) for the purpose of investigating the relationships among the numerous variables in large sets of multivariate space weather data. Specifically, we cover techniques in Principal Components Analysis (PCA) and Common Factor Analysis (CFA). These techniques are illustrated using space weather activity indices collected during the year 2002 and the corresponding noon-time hmF2 data from the International Reference Ionosphere (IRI). A CFA is used to categorize the activity indices, and a PCA is used to derive two macro-indices of activity to ascertain the strength of solar and geomagnetic activity. These macro-indices are then used to compare and contrast IRI’s noon-time hmF2 values at six different geographic stations. It was found that the correlation between hmF2 and the macro-indices more accurately represented the variation of this correlation with latitude found in previous studies than if we used an isolated conventional index, such as SSN and AE. We also found that the daily maximum value of the Polar Cap Index was dependent on both solar and geomagnetic activity, but the closely-related cross-Polar Cap Potential was solely associated with elevated levels of geomagnetic activity, which is a unique result compared to previous studies. We argue that the discrepancy can be explained by the difference in experiment designs between the two studies. This paper demonstrates the usefulness of EDA in space weather studies of large multivariate data sets.     

空间站和GNSS共视的差别及精度对比分析

为了对比空间站和导航卫星共视的性能差异,深入分析影响共视性能的主要误差源特征,推进共视技术进一步发展,以对共视时间比对基本原理的分析为基础,从系统设计和关键误差源影响两个方面对比分析空间站和导航卫星共视的差异。理论研究结果表明,不同于导航卫星共视,轨道误差是影响空间站共视精度进一步提升的主要因素;此外,空间站共视还需考虑地球引力时延等精细误差的影响。最后,设计并实施了仿真实验和实测实验,通过实验数据进一步对比两者的性能差异。实验结果表明空间站和导航卫星共视各有利弊,虽然空间站共视的服务区域和连续性逊于导航卫星共视,但可以实现的共视精度至少比导航卫星高一个数量级。     

耐高温树脂基复合材料研究进展及其在航空航天领域的应用

耐高温树脂基复合材料具有低密度、高比强度、高比模量、抗疲劳、耐腐蚀、可设计性强等优点。因其在结构轻量化中的巨大应用潜力,在航空航天领域广受关注。本文重点介绍了双马来酰亚胺、聚酰亚胺和邻苯二甲腈三种耐高温树脂及其复合材料,并对其树脂基体的历史发展脉络、复合材料成型工艺与力学性能的研究现状,以及在航空航天领域的应用进行了综述。最后,通过提炼对比三者在工艺性、力学性能上的特点和工程上的典型应用场景,拟为航空航天领域中的材料选择提供参考。     

全球电离层对2000年4月6-7日磁暴事件的响应

利用分布于全球的电离层台站的测高仪观测数据,对扰动期间,foF2值与其宁静期间参考值进行比较,研究了2000年4月6—7日磁暴期间全球不同区域电离层的响应形态,并通过对比磁扰期间NmF2的变化与由MSISR90经验模式估算的中性大气浓度比(no／nN2)的变化,探讨了本次事件期间的电离层暴扰动机制．结果表明,在磁暴主相和恢复相早期,出现了全球性的电离层F2层负相暴效应．最大负相暴效应出现在磁暴恢复相早期,即电离层暴恢复相开始时间滞后于磁暴恢复相开始时间．在磁暴恢复相后期,一些台站出现正相扰动．研究结果表明,本次事件期间的电离层暴主要是由磁暴活动而诱发的热层暴环流引起的．