我国雷暴活动对宇宙线福布希下降的短期响应

本研究了１９７１－１９８０年间５１个大于３％的宇宙线福布希下降对我国１８５个气象站上空雷暴活动的短期影响。结果表明，雷暴活动对福布希下降的短期响应存在明显的空间差异。在一些区域中福布希下降后雷暴活动明显增强，而在另一些区域中明显减弱。在这些明显响应区中，雷暴活动在福布希下降前后的差异显性分别通过了１０＾－２－１０＾－６置信度检验。这些响应区所在的地理位置与雷暴活动对耀斑爆发的响应区相互对应，但     

我国雷暴活动对宇宙线福布希下降的短期响应

本文研究了1971－1980年间51个大于3％的宇宙线福布希下降对我国185个气象站上空雷暴活动的短期影响.结果表明，雷暴活动对福布希下降的短期响应存在明显的空间差异．在一些区域中福布希下降后雷暴活动明显增强，而在另一些区域中明显减弱，在这些明显响应区中，雷暴活动在福布希下降前后的差异显著性分别通过了10-2－10－6置信度检验．这些响应区所在的地理位置与雷暴活动对耀斑爆发的响应区相互对应，但响应性质恰恰相反．这些结果给太阳活动与地球短期天气相关机理研究提出了新的挑战，也为进一步的研究提供了新的事实根据．     

1998年4月15日微波爆发观测

北京天文台１ ．０２ ．０ＧＨｚ 太阳射电频谱仪从１９９４ 年开始观测至１９９８ 年９ 月记录到太阳射电爆发１７１ 个,２ ．６３ ．８ＧＨｚ 太阳射电频谱仪１９９６ 年９ 月投入观测至１９９８ 年９ 月,记录到１４６ 个太阳射电爆发。１９９８ 年４ 月１５ 日太阳射电爆发同时在这两台频谱仪上记录到。这个事件在时间和频率上显示了丰富的幅度和结构的变化。发现了微波Ⅲ型爆发对群,并存在着丰富的快速活动现象。取得了高时间分辨率、高质量的动态谱资料,为研究耀斑各种尺度的时间及空间演化过程提供了丰富的信息。     

论在空间灾害性天气条件下低频太阳射电观测在预警心脑血管事件中的作用

太阳活动是对地球及人类生活影响最直接的天文活动,在航空航天、通信、电力以及人体健康方面影响着人类的生产生活。通过以往的一些研究结果分析非光学(non-optical)范畴的太阳活动例如日冕物质抛射、太阳射电爆发与某些人类疾病呈正相关性,这与低频太阳活动对日地空间的影响有密切联系。采用云南天文台2012年上半年70 MHz~1 500 MHz波段观测数据与昆明医科大学第一附属医院心脑血管病例结合进行相关分析,得到利用低频太阳活动爆发对人体影响预警的时间延迟因子(与等离子体抛射物质到达地球有关)。通过研究证明利用直接太阳低频射电观测数据能够较之于之前国际上利用宇宙线的福布希下降进行的空间天气预警提前2~3 d,有效地提高了预警效果,为下一步基于低频空间异动观测数据现报——健康实时预警系统的建立打下了工作基础。     

AGB星辐射s-过程核合成模型中子辐照量分布的计算方法和特点

考虑到模型参量随脉冲数的变化,推导出13C辐射燃烧的低质量AGB星s-过程核合成模型中子辐照量分布的计算方法,该方法具有普适性和简洁性.利用该方法,计算了3 M☉、太阳金属丰度恒星模型的中子辐照量分布.结果表明,若合理假设13C薄层内中子数密度均匀分布,则辐射核合成模型最终的中子辐照量分布趋近于指数分布.对于初始质量一定、金属丰度一定的恒星模型,平均中子辐照量τ0与每个脉冲的中子辐照量△τ存在确定的关系:τ0=0.434λ(q1,q2…qmmax+1,r1,r2…rmmax+1)△τ,式中mmax是带挖掘的脉冲总数,比例系数λ(q1,q2…qmmax+1,r1,r2…rmmax+1)可通过对最终中子辐照量分布的指数拟合得到.该式从中子辐照量分布角度定量地将经典模型和辐射s-过程核合成模型统一起来,使经典模型能为恒星模型核合成数值计算提供指导和约束.     

AGB星s-过程核合成相关问题的研究进展

综述了近年来AGB星核合成理论的研究情况,述及AGB星的结构与s-过程核合成有关的中子辐照量分布、人们比较关注的铅星与非铅星、后AGB星元素丰度分布及与AGB星核合成有关的s r星。     

贫金属星中子俘获元素丰度

贫金属星的中子俘获元素丰度与恒星的形成和演化密切相关,它为研究星系形成早期的历史背景和化学演化提供了重要信息。贫金属星中子俘获元素丰度的研究已成为近年来核天体物理研究的前沿和热点。介绍了恒星内部重元素的核合图像,ｓ过程和ｒ过程核合成的概念及其核合成场所。着重介绍了近年来有关贫金属星中子俘获元素丰度的观测结果,综述了近年来贫金属星子俘获元素分布的理论研究进展情况和中子俘获元素的星系化学演化的研究进展     

激变变星Ⅴ1159 Ori 和BZ UMa 的测光研究

Ⅴ1159 Ori 是SU UMa 型中 ER UMa 亚型激变变星,BZ UMa 介于 U Gem 型和 WZ Sge 型之间,但又具有 SU UMa 的周期特征,存在争议.在2008年2月24日和 25日,用云南天文台 1 米 RCC(Ritchey-Chretien-Coude)望远镜对两者的测光观测显示: Ⅴ1159 Ori 在正常爆发的下降阶段存在 superhump,这为 superhump 现象普遍存在于 ER UMa 型星中提供了观测证据;BZ UMa 观测时处于爆发极大,并未观测到确凿的 superhump 周期,而 AAVSO(American Association of Variable Star Observers)近年的 BZ UMa 观测亦从未发现明确的 superhump;两者均表明 BZ UMa 可能并非 SU UMa 型星.基于星等变化幅度考虑,BZ UMa 较 WZ Sge 更为接近.     

贫金属星中子俘获元素的丰度分布

在提出的贫金属星中子俘获元素丰度的计算模型基础上研究1999年新发表的21颗贫金属星的中子俘获元素丰度分布。结果表明，对较重的中子俘获元素理论预测曲线与观测值符合得很好，而对较轻的中子俘获元素二者有所偏离。这表明在贫金属环境下，对较重的中子俘获元素各核合成过程产生的丰度分布与太阳系中相应过程的丰度分布相似，但贡献比例与太阳系不同；而对较轻的中子俘获元素丰度分布与太阳系的丰度分布有所偏离；这也说明较轻的和较重的中子俘获元素的核合成场所不同，即具有不同的核合成机制。同时还特别讨论了丰度观测误差对表征各核合成过程的分量系数的影响。     

弱发射线T Tauri型星的高色散光谱观测

应用国家天文台兴隆观测基地2.16 m望远镜及其高色散光谱仪,对6颗弱发射线T Tauri型星(Weak-line T Tauri Stars,简称WTTS)进行了高色散光谱观测,计算了这些弱发射线T Tauri型星的锂元素丰度,讨论了这些弱发射线TTauri型星锂丰度和恒星自转周期、光变幅度的关系,研究发现:自转较快的弱发射线T Tauri型星锂丰度小于自转较慢的弱发射线T Tauri型星锂丰度;但是这些弱发射线TTauri型星,其锂丰度与恒星在V波段的光变幅度并没有明显的相关性.     

Impacts on Cosmic-Ray Intensity Observed During Geomagnetic Disturbances

Geomagnetic disturbances are the results of interplanetary causes such as high-speed streamers (HSSs), interplanetary coronal mass ejections (ICMEs), corotating interaction regions (CIRs), and magnetic clouds. During different forms of geomagnetic disturbances, we observed changes in the count rate at neutron monitors that are kept at various locations. We studied the count rates measured by neutron monitors at four stations at various latitudes during different categories of geomagnetic events and compared them. We analysed five events: a geomagnetically quiet event, a non-storm high-intensity long-duration continuous AE activity (HILDCAA) event, a storm-preceded HILDCAA event, a geomagnetic substorm event, and a geomagnetic moderate storm event. We based our analysis on geomagnetic indices, solar wind parameters, and interplanetary magnetic field (IMF) parameters. We found that the strength of the modulation was least during the quiet event and highest during the storm-preceded HILDCAA. By analysing the cause of these geomagnetic disturbances, we related each decrease in the neutron monitor data with the corresponding solar cause. For the ICME-driven storm, we observed a decrease in neutron monitor data ranging from 6% to 12% in all stations. On the other hand, we observed a decrease ranging from 2% to 5% for the HSS-driven storm. For the non-storm HILDCAA, we observed a decrease in neutron monitor data of about 1% to 1.5%. For the quiet event, the neutron monitor data fluctuated such that there was no overall decrease in all stations.     

Possible solar neutron events recorded by the ground-based neutron monitor

Possible solar neutron emission associated with five SMM gamma-ray events on 7 June 1980, 21 June 1980, 6 November 1980, 26 November 1982 and 25 April 1984 was found from analysis of 10-minute records of the ground-based neutron monitor at Tokyo. Of these the two events on 21 June 1980 and 25 April 1984 have been already known as neutron events. The time histories of the neutron monitor count rate are compared with those of the gamma-ray count rate and the possibility of energetic neutron emission at the flare site is discussed.     

Types of interplanetary shocks and forbush decreases

Two types of interplanetary shocks have been identified and classified into two groups, those associated with a helium-enhancement and those not associated with any helium-enhancement. The cosmic-ray intensity decreases at Calgary neutron monitor are studied with respect to the arrival time of the two groups of shocks. The observations show that large Forbush decreases are caused by shocks associated with the helium-enhancement; and those not associated with He shocks show comparatively a small decrease in cosmic-ray intensity.     

Ground-level energetic solar particle event on 24 May 1990: Possibility of direct solar neutron detection

The first increase in neutron monitor count rate during the ground-level event on 24 May 1990 was interpreted by Shea et al. (1991) as a consequence of an arrival of flare neutrons. Debrunner et al. (1991) rejected the neutron hypothesis and proposed that the first neutron monitor increase was due to the arrival of primary protons. We have show that neutron monitor data do not contradict the hypothesis of a neutron origin of the first increase of ground-level event on 24 May 1990.     

Spacecraft measurement of Forbush decreases in the cosmic radiation

The Forbush decrease in the cosmic radiation has been measured by a charged-particle monitor (E _p )> 50 MeV) on board the OGO-6 satellite. For the events of June 7–10, September 27–30, and November 21–December 6, 1969, the Forbush decrease totalled 4.6, 6, and 6% in amplitude, respectively, for the Mt. Washington neutron monitor (P _c = 1.24 GV), and 5.2, 13, and 16%, respectively, for the OGO-6 charged-particle monitor in the polar region (P _c < 0.3 GB). The depression in the OGO-6 charged-particle monitor was larger at higher geomagnetic latitudes than at lower latitudes. However, for the events of June 7–10 and November 21–December 6, 1969, the Forbush decrease totalled 20 and 15% in amplitude respectively for the Pioneer 8 cosmic-ray telescope (P _c > 0.4 GV), which was at the respective distances of 1.08 AU and 1 AU from the Sun. These results indicate that the Forbush decrease has greater effects on lower-energy charged particles, the magnitude of the effect also depending on the location of the detector with respect to the modulating region.The spacecraft data near Earth also showed that, for vertical cut-off rigidities P _c 1.8 GV, the total percentage decrease in the amplitudes of the Forbush decreases can be represented by –mP _c + k, where m and k are each constant for the particular Forbush decrease but which increase with increasing Mt. Washington neutron monitor monthly average rates, an indication of a flattening of the rigidity dependence of Forbush decreases towards maximum solar modulation.     

Solar Proton Rigidity Spectra From 1 to 10 gv of Selected Flare Events Since 1960

We have deduced the power-law rigidity spectra, J(P)=AP ^–, and the spectral evolution of the solar flare events that occurred in the present solar activity cycle on 6 November 1997, 14 July 2000, and 15 and 18 April 2001. The implications of these results for the acceleration of high-energy protons are discussed. The analysis is based on the ratios of the Mt. Washington to the Durham neutron monitor count-rate increases during the solar flare events. These two neutron monitors are located at different elevations (828 and 1030 g cm^–2, respectively) but at approximately the same geographical latitude and longitude. The proton spectra from 1 to 10 GV determined from the ratios of the count rate increases of the two neutron monitors are found to agree with those deduced from the global neutron monitor network or selected neutron monitors in 10 solar flare events from 1960 to 1990 for which comparative results are available. Thus the ratio method is quick, easy and reliable for deducing the spectral shape of solar flare protons at neutron monitor rigidities and for obtaining the spectral evolution as a function of time.     

Solar and interplanetary disturbances causing moderate geomagnetic storms

The effect of solar and interplanetary disturbances on geomagnetospheric conditions leading to 121 moderate geomagnetic storms (MGS) have been investigated using the neutron monitor, solar geophysical and interplanetary data during the period 1978–99. Further, the duration of recovery phase has been observed to be greater than the duration of main phase in most of the cases of MGS. It has further been noted that Ap-index increases on sudden storm commencement (SSC) day than its previous day value and acquires maximum value on the day of maximum solar activity. Generally, the decrease in cosmic ray (CR) intensity and Dst begins few hours earlier than the occurrence of MGS at Earth. Furthermore, negative Bz pointing southward plays a key causal role in the occurrence of MGS and the magnitude and the duration of Bz and Bav also play a significant role in the development of MGS. The solar features Hα, X-ray solar flares and active prominences and disappearing filaments (APDFs) which have occurred within lower helio-latitudinal/helio-longitudinal zones produce larger number of MGS. Solar flares seem to be the major cause for producing MGS.     

Temporal Changes in the Rigidity Spectrum of Forbush Decreases Based on Neutron Monitor Data

The Forbush decrease (Fd) of the Galactic cosmic ray (GCR) intensity and disturbances in the Earth’s magnetic field generally take place simultaneously and are caused by the same phenomenon, namely a coronal mass ejection (CME) or a shock wave created after violent processes in the solar atmosphere. The magnetic cut-off rigidity of the Earth’s magnetic field changes because of the disturbances, leading to additional changes in the GCR intensity observed by neutron monitors and muon telescopes. Therefore, one may expect distortion in the temporal changes in the power-law exponent of the rigidity spectrum calculated from neutron monitor data without correcting for the changes in the cut-off rigidity of the Earth’s magnetic field. We compare temporal changes in the rigidity spectrum of Fds calculated from neutron monitor data corrected and uncorrected for the geomagnetic disturbances. We show some differences in the power-law exponent of the rigidity spectrum of Fds, particularly during large disturbances of the cut-off rigidity of the Earth’s magnetic field. However, the general features of the temporal changes in the rigidity spectrum of Fds remain valid as they were found in our previous study. Namely, at the initial phase of the Fd, the rigidity spectrum is relatively soft and it gradually becomes hard up to the time of the minimum level of the GCR intensity. Then during the recovery phase of the Fd, the rigidity spectrum gradually becomes soft. This confirms that the structural changes of the interplanetary magnetic field turbulence in the range of frequencies of 10^?6?–?10^?5 Hz are generally responsible for the time variations in the rigidity spectrum we found during the Fds.     

Cosmic ray modulation studies with Lead-Free Gulmarg Neutron Monitor

A lead-free neutron monitor operating at High Altitude Research Laboratory (HARL), Gulmarg optimized for detecting 2.45 MeV neutron bursts produced during the atmospheric lightning discharges is also concurrently used for studying background neutron component present in the atmosphere. These background neutrons are produced due to the interaction of primary cosmic rays with the atmospheric constituents. In order to study and extract the information about the yield of the neutron production during transient atmospheric lightning discharges, the system is continuously operated to monitor and record the cosmic ray produced background secondary neutrons in the atmosphere. The data analysis of the background neutrons recorded by Lead-Free Gulmarg Neutron Monitor (LFGNM) has convincingly established that the modulation effects due to solar activity phenomena compare very well with those monitored by the worldwide IGY or NM64 type neutron monitors which have optimum energy response relatively towards the higher energy regime of the cosmic rays. The data has revealed various types of modulation phenomena like diurnal variation, Forbush decrease etc. during its entire operational period. However, a new kind of a periodic/seasonal variation pattern is also revealed in the data from September 2007 to September 2012, which is seen to be significantly consistent with the data recorded by Emilio Segre observatory, Israel (ESOI) Neutron Monitor. Interestingly, both these neutron monitors have comparable latitude and altitude. However, the same type of consistency is not observed in the data recorded by the other conventional neutron monitors operating across the globe.     

Artificial Neural Network Approach of Cosmic Ray Primary Data Processing

One of the most critical points in the detection of cosmic rays by neutron monitors is the correction of the raw data. The data that a detector measures may be distorted by a variety of reasons and the subtraction of these distortions is a prerequisite for processing them further. The final aim of these corrections is to keep only the fluctuations related to the real cosmic-ray intensity. To achieve this, we analyze data from identical neutron monitor detectors which provide a configuration with the ability to exclude the distortions by comparing the counting rate of each detector. Based on this method, a number of effective algorithms have been developed: Median Editor, Median Editor Plus, and Super Editor are some of the algorithms that are being used in the neutron monitor data processing with satisfactory results. In this work, a new approach for the correction of the neutron monitor primary data with a completely different method, based on the use of artificial neural networks, is proposed. A comparison of this method with the algorithms mentioned previously is also presented.