电离层TEC对小耀斑的响应

利用国际GPS观测网(IGS)提供的多个台站的观测数据,分析了M级别以下的小、暗太阳耀斑对向阳面电离层TEC的影响．利用传统分析方法的结果表明,从单条视线(LOS)观测数据得到的电离层TEC及其时间变化率曲线来看,由于它们的波动水平和正常情况下的背景电离层变化相当,使此类小耀斑的信息完全淹没在背景噪声中,不能够显示和分辨出耀斑的发生．利用相干求和的数据处理方法,选用向阳面18个GPS台站的观测数据研究了一次C级SF耀斑引起的电离层TEC增加,结果发现,这种方法能有效地消除背景电离层变化噪声,电离层对耀斑的响应非常清楚和明显,这通常只能在X级别的大耀斑中看到．和GOES卫星X射线数据相比,电离层TEC变化的时间特征和耀斑爆发的开始、最大和结束时间均有很好的符合,其最大平均TEC增量在0．1TECU以下,和X级别的大耀斑相比有一个或多个量级上的差别．     

太阳X射线爆发与低电离层突然骚扰

本文分析了1981年1月至5月期间记录的低电离层突然骚扰(SID)和太阳X射线爆发数据发现:1.几乎所有的研究情况,每一个低电离层的突然骚扰都是太阳X射线爆发引起的。且SID与太阳X射线爆发之间有着相同的开始和极值时间;2.能够引起低电离层产生较明显的SID的太阳X射线爆发的峰值流量下限对于0.5～4A频段是约4×10~(-3)w/m~2,对1～8A频段是2×10~(-6)w/m~2;3.相关分析表明,太阳X射线爆发的流量变化量与低频记录的突然相位异常(SPA)的变化量之间有好的相关性。根据这个初步的研究有可能利用低频SPA的监测来较好地检测太阳X射线爆发。     

“雨燕”观测到风车星系

“雨燕”卫星的紫外/光学望远镜(UVOT)第一次拍摄到风车星系,一个业余天文学家喜爱的几乎完美的正向旋涡星系的照片。此外,UVOT还观测到这个星系的一次γ射线暴。“雨燕”是美国宇航局发射的旨在研究γ射线暴的一颗卫星。这些随机和闪电式的爆发很可能是黑洞诞生的迹象。“雨燕”上的另外两台仪器——爆发警报望远镜(BAT)和X射线望远镜(XRT)在过去几周一直开启着,抢先拍下了γ射线暴。     

太阳耀斑引起的突发电离层骚扰(英文)

太阳活动第22周峰年期内,我国组织了日地系统整体行为的联合观测研究,中科院武汉物理研究所开展了多项电离层观测,见表1,监测太阳活动在电离层中不同高度上的效应。垂测记录的形式为频高图;长波观测中为Loran—c信号的相位和振幅变化。由武昌、天门和安陆三个站组成的台阵,记录了BPM时号的三维多普勒频谱结构,还同时记录了电子总含量(TEC)的变化。 本文讨论SID,主要观测结果列在表2。表2按确认的SFD事件排列。这种记录虽是全天候的从未中断过,但由于短波传播条件的各种特殊变化,不能认为已收入了全部SFD事件。长波观测有少数缺记情况,TEC记录虽未中断,但它的灵敏度低,只能检测大耀斑。表中的耀斑事件也不全,可能漏掉了一些对电离层效应很灵敏的急剧变化的短暂事件。从表2中得出下列主要结论:(1)SFD是一种很好的光耀斑指示器;(2)SPA是X射线耀斑的指示器;(3)出现特强的SFD和SPA,并出现可检测的SITEC常暗示着1—3天内,将出现电离层暴或大尺度TID。由于记录是连续实时显示的,这种观测在日地空间环境监测、预报和研究中是很有用的。     

基于同波束VLBI的双差分电离层电子总量抖动与角距离关系模型

深空探测器信号穿过地球电离层时会产生信号时延和相位抖动,从而对VLBI(Very Long Baseline Interferometry)测量精度产生很大影响.利用日本SELENE 2颗小卫星Rstar和Vstar的4测站6基线长达1 yr的同波束VLBI观测数据,首次解算出了双差分电离层电子总量抖动的均方根和角距离的关系模型.6条基线的双差分电离层电子总量抖动的均方根r(单位为TECU)和角距离θ(?)的关系模型为:r=0.773θ+0.562,由基线反演出的4个测站的关系模型为:r=0.554θ+0.399.研究成果对差分相时延的解算和行星电离层掩星观测研究均有重要参考意义.     

1989年4月9日的3级大耀斑

本文对1989年4月9日发生在小黑子活动区的3B级大耀斑作了形态分析,得到如下结果。1.耀斑具有双带结构,活动暗条被耀斑的双带包围在中间。2.和耀斑有关的S形活动暗条在耀斑爆发前后有明显变化,最终全部消失。3.耀斑的X—射线事件引起电离层2级和1级扰动(SID)各一次。4.离带观测表明存在着物质的下降运动。5.黑子半影具有旋涡结构。     

GRB 170817A的洛伦兹因子和观测角

伴随着引力波事件GW170817的短暴GRB (Gamma-Ray Burst) 170817A首次提供了双中子星并合与短暴相联系的直接证据.但是短暴GRB 170817A具有非常弱的光度,意味着观测的视线方向可能偏离喷流轴方向.根据短暴静止系的峰值能量E_(p,i)和各向同性光度L_(iso)。之间的关系以及洛伦兹因子Γ和L_(iso)。之间的关系估算了短暴GRB 170817A以及长短暴GRB 060614观测角与喷流边缘的夹角θ'_(obs)和洛伦兹因子Γ,结果表明GRB 170817A的Γ=45±27,θ'_(obs)=2.2±0.5°,而GRB 060614的Γ=214±93,θ'_(obs)=0.5±0.1°.这个结果相当于GRB 170817A的正轴各向同性光度L_(iso,on)=(2.1±0.7)×10~(49) erg·s~(-1),比典型的短暴少2-3个数量级.GRB 060614的L_(iso,on)=(5.12±1.91)×10~(51) erg·s~(-1)与典型短暴相当.这意味着GRB 060614可能属于短暴类型,而GRB 170817A可能本质上就是一个弱暴.     

发现和伽玛射线暴成协的超新星

伽玛射线暴是天空中某个方向上短时间在伽玛射线波段的猛烈爆发。今年3月29日世界时11时37分15秒,HETE-2卫星(高能暂现源探测器)在狮子座方向探测到了一个持续了25秒以上的伽玛射线暴GRB030329,并在很短的时间把其位置坐标传回了地面。地面上许多     

基于γ暴等观测限制宇宙学参数与暗能量模型

利用Union2 557个Ia型超新星数据限制宇宙学参数qo、jo和so,在红移z≤1.4范围内校准5个γ暴(gamma-ray burst,GRB)光度关系.假设γ暴光度关系不随红移演化,得到66个高红移γ暴的距离模数.最后综合利用宇宙微波背景(Cosmic Microwave Background,CMB)辐射观测数据、重子声波震荡(Baryon AcousticOscillations,BAO)观测数据与116个具有红移的γ暴数据限制几个常见的暗能量模型.根据贝叶斯判据(Bayesian Information Criterion,BIC),发现ACDM模型是最好的模型;根据Akaike判据(Akaike Information Criterion,AIC),发现JBP模型是最好的模型.     

太阳X射线爆发对长波定时与校频的影响

太阳X射线爆发引起电离层D区的突然扰动(SID),直接影响低频天波信号的传播。本文给出了由SID所引起的低频灭波信号幅度与相位突然异常的部分观测结果,分析了对利用天波甚至可能对利用地波定时、校频产生的影响,并提出了减小这种影响的方法。     

Response of the Total Electron Content of Terrestrial Ionosphere to GRB041227

At 21:30 UT on 2004 December 27 an extremely strong gamma-ray burst swept across the earth and caused the part of the terrestrial upper atmosphere exposed to it to produce extra ionization. Sudden ionospheric disturbance (SID) events were simultaneously observed at many of the very low frequency (VLF) electric wave observing stations. Analyses of the X-ray data of the GOES satellite as well as the solar wind and interplanetary data of the ACE satellite with the relevant theories show that the observed SID event observed was indeed caused by GRB041227. We calculated the response of the total electron content (TEC) of the terrestrial ionosphere to this γ-ray burst using the observed data provided by the international GPS service network (IGS) and the data processing method of coherent summation. The result indicates that the GRB041227 produced by the SGR1806-20 had an evident effect on the terrestrial ionosphere: in the course of the burst the average ionospheric TEC increased, to a maximum size of about 0.04 TECU (1 TECU = 10¹⁶ el/m²), equivalent to a solar flare with importance of C or lower. The calculated result demonstrates once again that a remote celestial body can also affect the terrestrial space environment to some extent.     

Giant flare in SGR 1806-20 and its Compton reflection from the Moon

We analyze the data obtained when the Konus-Wind gamma-ray spectrometer detected a giant flare in SGR 1806-20 on December 27, 2004. The flare is similar in appearance to the two known flares in SGR 0526-66 and SGR 1900+14 while exceeding them significantly in intensity. The enormous X-ray and gamma-ray flux in the narrow initial pulse of the flare leads to almost instantaneous deep saturation of the gamma-ray detectors, ruling out the possibility of directly measuring the intensity, time profile, and energy spectrum of the initial pulse. In this situation, the detection of an attenuated signal of inverse Compton scattering of the initial pulse emission by the Moon with the Helicon gamma-ray spectrometer onboard the Coronas-F satellite was an extremely favorable circumstance. Analysis of this signal has yielded the most reliable temporal, energy, and spectral characteristics of the pulse. The temporal and spectral characteristics of the pulsating flare tail have been determined from Konus-Wind data. Its soft spectra have been found to contain also a hard power-law component extending to 10 MeV. A weak afterglow of SGR 1806-20 decaying over several hours is traceable up to 1 MeV. We also consider the overall picture of activity of SGR 1806-20 in the emission of recurrent bursts before and after the giant flare.     

High frequency oscillations during magnetar flares

The recent discovery of high frequency oscillations during giant flares from the Soft Gamma Repeaters SGR 1806-20 and SGR 1900+14 may be the first direct detection of vibrations in a neutron star crust. If this interpretation is correct it offers a novel means of testing the neutron star equation of state, crustal breaking strain, and magnetic field configuration. We review the observational data on the magnetar oscillations, including new timing analysis of the SGR 1806-20 giant flare using data from the Ramaty High Energy Solar Spectroscopic Imager and the Rossi X-ray Timing Explorer. We discuss the implications for the study of neutron star structure and crust thickness, and outline areas for future investigation.      

The radio nebula produced by the 27 December 2004 giant flare from SGR 1806-20

On 27 December 2004, just the third giant flare was observed from a magnetar, in this case SGR 1806-20. This giant flare was the most energetic of the three, and analysis of a Very Large Array observation of SGR 1806-20 after the giant flare revealed the existence of a new, bright, transient radio source at its position. Follow-up radio observations of this source determined that initially, this source underwent a mildly relativistic one-sided expansion which ceased at the same time as a temporary rebrightening of the radio source. These observational results imply that the radio emission is powered by ∼10²⁴ g of baryonic material which was ejected off the surface on the neutron star during the giant flare.      

利用GPS探测电离层异常中的高斯过程处理方法

平静状态下电离层总电子含量（TEC）随时间的变化通常可以视为平稳随机过程。然而，太阳或地球的突发事件（如太阳耀斑、地磁场的扰动）会引起电离层的扰动，破坏该平稳过程，从而引起其统计参数的变化。依据平稳随机过程——高斯过程的相关性质，利用其自协方差函数和TEC时间系列，构建了独立同标准正态分布的观测样本，并利用X^2假设检验的方法来探测电离层异常现象。此外，还利用了2000年7月14日太阳耀斑期间我国国际IGS跟踪站武汉GPS跟踪站的数据，进行了实例分析。结果表明，该方法可以有效地探测电离层异常现象。     

Lower bound on the magnetic field strength of a magnetar from analysis of SGR giant flares

Based on the magnetar model, we have studied in detail the processes of neutrino cooling of an electron-positron plasma generating an SGR giant flare and the influence of the magnetar magnetic field on these processes. Electron-positron pair annihilation and synchrotron neutrino emission are shown to make a dominant contribution to the neutrino emissivity of such a plasma. We have calculated the neutrino energy losses from a plasma-filled region at the long tail stage of the SGR 0526-66, SGR 1806–20, and SGR 1900+14 giant flares. This plasma can emit the energy observed in an SGR giant flare only in the presence of a strongmagnetic field suppressing its neutrino energy losses. We have obtained a lower bound on the magnetic field strength and showed this value to be higher than the upper limit following from an estimate of the magnetic dipole losses for the magnetars being analyzed in a wide range of magnetar model parameters. Thus, it is problematic to explain the observed energy release at the long tail stage of an SGR giant flare in terms of the magnetarmodel.     

MMIV: de SGR 1806–20 Anno Mirabili

On 27th December 2004 SGR 1806–20, one of the most active Soft γ-ray Repeaters (SGRs), displayed an extremely rare event, also known as giant flare, during which up to 10⁴⁷ ergs were released in the ∼1–1000 keV range in less than 1 s. Before and after the giant flare we carried out IR observations by using adaptive optics (NAOS-CONICA) mounted on VLT which provided images of unprecedented quality (FWHM better than 0.1″). We discovered the likely IR counterpart to SGR 1806–20 based on positional coincidence with the VLA uncertainty region and flux variability of a factor of about 2 correlated with that at higher energies. Moreover, by analysing the Rossi-XTE/PCA data we have discovered rapid Quasi-Periodic Oscillations (QPOs) in the pulsating tail of the 27th December 2004 giant flare of SGR 1806–20. QPOs at ∼92.5 Hz are detected in a 50 s interval starting 170 s after the onset of the giant flare. These QPOs appear to be associated with increased emission by a relatively hard unpulsed component and are seen only over phases of the 7.56 s spin period pulsations away from the main peak. QPOs at ∼18 and ∼30 Hz are also detected ∼200–300 s after the onset of the giant flare. This is the first time that QPOs are unambiguously detected in the flux of a Soft Gamma-ray Repeater, or any other isolated neutron star. We interpret the highest QPOs in terms of the coupling of toroidal seismic modes with Alfvén waves propagating along magnetospheric field lines. The lowest frequency QPO might instead provide indirect evidence on the strength of the internal magnetic field of the neutron star.      

Ionospheric disturbances: Evidence for the contraction of the plasmasphere during severe geomagnetic storms

Continuous measurements of the ionospheric total electron content (TEC) provide a parameter well suited for the study of F-region disturbance effects. In this investigation, five cases of large and rapid drops in TEC observed near the sunset period are interpreted as being due to the contraction of the plasmasphere to L values less than 3. A model calculation is performed for the specific case of 1 November 1968 using simultaneous Alouette I data to define the position and magnitude of the ionospheric trough. The results indicate that the motion of a deep trough across the ray path from a geostationary satellite to an observing station can cause drastic changes in the measured amounts of Faraday rotation and therefore in the derived values of TEC. All of the TEC data sources available for the five events are then examined in an attempt to describe more completely the latitude dependence of the effects. It is suggested that during severe geomagnetic storms, the large and rapid decays in TEC during the 18–21 LT period to values significantly below normal can be used as a criterion to determine the approximate latitudinal extent of the contracted plasmasphere.     

The Characteristics of the X-ray Flares (1-8, GOES) of the Different Classes and Their Variations in Two Cycles of Solar Activity

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