On Dimensionality Reduction for Indexing and Retrieval of Large-Scale Solar Image Data

This work investigates the applicability of several dimensionality reduction techniques for large-scale solar data analysis. Using a solar benchmark dataset that contains images of multiple types of phenomena, we investigate linear and nonlinear dimensionality reduction methods in order to reduce our storage and processing costs and maintain a good representation of our data in a new vector space. We present a comparative analysis of several dimensionality reduction methods and different numbers of target dimensions by utilizing different classifiers in order to determine the degree of data dimensionality reduction that can be achieved with these methods, and to discover the method that is the most effective for solar images. After determining the optimal number of dimensions, we then present preliminary results on indexing and retrieval of the dimensionally reduced data.     

Estimation Of Seeing Quality Using Low-Resolution Solar Image Data

Modulation transfer functions (MTFs), generated as a by-product of the analysis of low-resolution solar images taken for the Global Oscillation Network Group, were used to estimate the quality of seeing at its six sites. These MTFs, after approximate correction for the effects of the instrumental point spread function, were fitted with physically-motived functional forms representing the effects of seeing and scattering. It was found that the estimates of seeing quality were relatively robust to the effects of scattering, but were severely biased by effects caused by changes in instrumental focus. Relative trends in seeing quality are preserved on time scales shorter than a few months and it is found that local topography dominates the observed trends in daytime seeing quality.     

Analysis of the Properties of Super Solar Proton Events and Associated Phenomena

The solar flares, the speeds of shocks propagated in the solar-terrestrial space and driven by coronal mass ejections (CMEs), the heliographic longitudes and Carrington longitudes of source regions, and the geomagnetic storms, which are accompanied by the super solar proton events with a peak ?ux equal to or exceeding 10 000 pfu, have been studied by using the data of ground-based and space observations. The results show that the heliographic longitudes of source regions of super solar proton events distributed in the range from E30? to W75°. The Carrington longitudes of source regions of super solar proton events distributed in the two longitudinal belts, 130°∼220° and 260°∼320°, respectively. All super solar proton events were accompanied by major solar flares and fast CMEs. The averaged speeds of shocks propagated from the sun to the Earth were greater than 1 200 km/s. Eight super solar proton events were followed by major geomagnetic storms (Dst≤−100 nT), except that one super solar proton event was followed by a geomagnetic storm with the geomagnetic activity index Dst=−96 nT, a little smaller than that of major geomagnetic storms.     

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

Solar eruptions are the most spectacular events in our solar system and are associated with many different signatures of energy release including solar flares, coronal mass ejections, global waves, radio emission and accelerated particles. Here, we apply the Coronal Pulse Identification and Tracking Algorithm (CorPITA) to the high-cadence synoptic data provided by the Solar Dynamics Observatory (SDO) to identify and track global waves observed by SDO. 164 of the 362 solar flare events studied (45%) were found to have associated global waves with no waves found for the remaining 198 (55%). A clear linear relationship was found between the median initial velocity and the acceleration of the waves, with faster waves exhibiting a stronger deceleration (consistent with previous results). No clear relationship was found between global waves and type II radio bursts, electrons or protons detected in situ near Earth. While no relationship was found between the wave properties and the associated flare size (with waves produced by flares from B to X-class), more than a quarter of the active regions studied were found to produce more than one wave event. These results suggest that the presence of a global wave in a solar eruption is most likely determined by the structure and connectivity of the erupting active region and the surrounding quiet solar corona rather than by the amount of free energy available within the active region.     

An Analysis of Polar Coronal Hole Evolution: Relations to Other Solar Phenomena and Heliospheric Consequences

We use observations of the green corona low-brightness regions to construct a time series of a polar coronal hole area from 1939 to 1996, covering 5 solar cycles. We then perform a power-spectral analysis of the monthly data time series. Several persistent significant periodicities appear in the spectra, which are related with those found in solar magnetic flux emergence, geomagnetic storm sudden commencements and cosmic-ray flux at Earth. Of particular importance are the peak at around 1.6–1.8 yr recently found in cosmic-ray intensity fluctuations, and the peak at around 1 yr, also identified in coronal hole magnetic flux variations. Additional interesting features are the peaks close to 5 yr, 3 yr and the possible peak at around 30 yr, that were also found in other solar and interplanetary phenomena. Our results stress the physical connection between the solar magnetic flux emergence and the interplanetary medium dynamics, in particular the importance of coronal hole evolution in the structuring of the heliosphere.     

一个新型分米波太阳微耀斑现象的观测分析

本文介绍一组短分米波（1．42GHz）太阳微耀斑的射电和光学辐射特征，它们包含53个叠加在连续辐射背景上的射电快速精细结构（FFS），即准周期快速脉冲链（称微耀斑），它们的形态相似，强度大约在150－200sfu范围内，其寿命（半功率宽）大多为15－50ms，有18个分离的双峰结构，该事件产生的7646活动区中出现两处新浮现的几个小黑子，呈现复杂极性，可能存在多重交叉小磁流环多次重联的复杂状况．本文定性地讨论了其产生机制，支持电流环爆炸性聚合模型的理论。     

1D Solar Image Synthesis: A Multifrequency Analysis

The radio emission from the solar corona is related to the configuration of the inner atmosphere. By studying the Sun at multiple frequencies, different layers of plasma in solar atmosphere are probed. We use the Mauritius Radio Telescope. The quiet Sun period, difference maps using synthesized 1D maps reveal a certain regular feature, the origin of which is not thoroughly understood and which is attributed to the solar differential rotation. For the active Sun period, the coronal emission is linked to the magnetic field configuration originating from the inner atmosphere. As expected, a strong correlation exists between the MRT 151 MHz and Nancay 164 MHz radio emission. This revised version was published online in July 2006 with corrections to the Cover Date.     

伴随米波Ⅲ型爆发的快速脉动现象的观测分析

统计分析了太阳22周峰年期间云南天文台声光频谱仪在230—300MHz频率范围，记录到的Ⅲ型爆发和毫秒级快速脉动共存事件。发现有两种不同的脉动现象：(1)普通型脉动；(2)包迹型脉动，并在此基础上对Ⅲ型一脉动共存事件与之对应的光学活动及相关事件，脉动的形态、周期、带宽等观测特征作了分析和讨论。     

Principal Components and Independent Component Analysis of Solar and Space Data

Principal components analysis (PCA) and independent component analysis (ICA) are used to identify global patterns in solar and space data. PCA seeks orthogonal modes of the two-point correlation matrix constructed from a data set. It permits the identification of structures that remain coherent and correlated or that recur throughout a time series. ICA seeks for maximally independent modes and takes into account all order correlations of the data. We apply PCA to the interplanetary magnetic field polarity near 1 AU and to the 3.25R _⊙ source-surface fields in the solar corona. The rotations of the two-sector structures of these systems vary together to high accuracy during the active interval of solar cycle 23. We then use PCA and ICA to hunt for preferred longitudes in northern hemisphere Carrington maps of magnetic fields.     

Analysis and Packaging of Radiochemical Solar Neutrino Data: A Bayesian Approach

According to current practice, the results of each run of a radiochemical solar neutrino experiment comprise an estimate of the flux and upper and lower error estimates. These estimates are derived by a maximum-likelihood procedure from the times of decay events in the analysis chamber. This procedure has the following shortcomings: (a) published results sometimes include negative flux estimates; (b) even if the flux estimate is non-negative, the probability distribution function implied by the flux and error estimates will extend into negative territory; and (c) the overall flux estimate derived from the results of a sequence of runs may differ substantially from an estimate made by a “global” analysis of all of the timing data taken together. These defects indicate that the usual “packaging” of data in radiochemical solar neutrino experiments provides an inadequate summary of the data, which implies a loss of information. This article reviews this problem from a Bayesian perspective, and we suggest an alternative scheme for the packaging of radiochemical solar neutrino data, which we believe is free from these shortcomings.     

Chromospheric Height and Density Measurements in a Solar Flare Observed with RHESSI – II. Data Analysis

We present an analysis of hard X-ray imaging observations from one of the first solar flares observed with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) spacecraft, launched on 5 February 2002. The data were obtained from the 22 February 2002, 11:06 UT flare, which occurred close to the northwest limb. Thanks to the high energy resolution of the germanium-cooled hard X-ray detectors on RHESSI we can measure the flare source positions with a high accuracy as a function of energy. Using a forward-fitting algorithm for image reconstruction, we find a systematic decrease in the altitudes of the source centroids z(ε) as a function of increasing hard X-ray energy ε, as expected in the thick-target bremsstrahlung model of Brown. The altitude of hard X-ray emission as a function of photon energy ε can be characterized by a power-law function in the ε=15–50 keV energy range, viz., z(ε)≈2.3(ε/20 keV)^−1.3 Mm. Based on a purely collisional 1-D thick-target model, this height dependence can be inverted into a chromospheric density model n(z), as derived in Paper I, which follows the power-law function n _e(z)=1.25×10¹³(z/1 Mm)^−2.5 cm⁻³. This density is comparable with models based on optical/UV spectrometry in the chromospheric height range of h≲1000 km, suggesting that the collisional thick-target model is a reasonable first approximation to hard X-ray footpoint sources. At h≈1000–2500 km, the hard X-ray based density model, however, is more consistent with the `spicular extended-chromosphere model' inferred from radio sub-mm observations, than with standard models based on hydrostatic equilibrium. At coronal heights, h≈2.5–12.4 Mm, the average flare loop density inferred from RHESSI is comparable with values from hydrodynamic simulations of flare chromospheric evaporation, soft X-ray, and radio-based measurements, but below the upper limits set by filling-factor insensitive iron line pairs.     

太阳射电频谱观测数据分析系统方案设计

中国太阳射电宽带动态频谱仪(solar Broadband Radio Spectrometer)在太阳物理研究和国际合作交流中发挥了重要作用.为进一步扩大该设备观测数据的国际交流和共享、挖掘数据的深层信息、加快科学产出,有必要开发一套与SSW(Solar Soft Ware)兼容的数据分析系统.该系统具有以下主要特点:(1)按SSW规范设计编写,既可以在SSW环境下运行也可以独立安装使用;(2)新界面设计更易于用户上手,也可以进行复杂深层的数值分析;(3)规范明晰的功能模块和流程设计减少了漏洞和排错时间,定标和特征信息提取等多种亟需功能的完善为科学研究开拓了空间,节省了时间;(4)利用MySQL关系数据库管理系统建设一个安全稳定、易于升级管理的数据库,便于浏览搜索和批量下载.此外,该数据分析系统的开发将为正在研制的中国太阳射电频谱日像仪积累经验和储备技术,并为国内其它台站提供模式和经验.     

一个复杂大爆发的分析

本文分析了2002.7.23国家天文台云南天文台射电频谱仪在625～1500 MHz、2600～3800 MHz和5200～7600 MHz记录到的复杂型大爆发,将此爆发与Hα耀斑、日冕物质抛射(CME)、硬X射线爆发及地球物理参数作了相关分析,得到这个事件的一些显著特征,认为这一事件电子的加速区在日冕的外层,接近625 MHz的地方,并且多次发生磁重联.磁重联以后的衰变相是湍流加速过程.     

Multiwavelength Study of a Solar Eruption from AR NOAA 11112: II. Large-Scale Coronal Wave and Loop Oscillation

We analyze multiwavelength observations of an M2.9/1N flare that occurred in AR NOAA 11112 on 16 October 2010. AIA 211 Å EUV images reveal the presence of a faster coronal wave (decelerating from ≈?1390 to ≈?830 km?s^?1) propagating ahead of a slower wave (decelerating from ≈?416 to ≈?166 km?s^?1) towards the western limb. The dynamic radio spectrum from Sagamore Hill radio telescope shows the presence of a metric type II radio burst, which reveals the presence of a coronal shock wave (speed ≈?800 km?s^?1). The speed of the faster coronal wave, derived from AIA 211 Å images, is found to be comparable to the coronal shock speed. AIA 171 Å high-cadence observations showed that a coronal loop, which was located at a distance of ≈?0.32R _⊙ to the west of the flaring region, started to oscillate by the end of the impulsive phase of the flare. The results indicate that the faster coronal wave may be the first driver of the transversal oscillations of coronal loop. As the slower wave passed through the coronal loop, the oscillations became even stronger. There was a plasmoid eruption observed in EUV and a white-light CME was recorded, having velocity of ≈?340?–?350 km?s^?1. STEREO 195 Å images show an EIT wave, propagating in the same direction as the lower-speed coronal wave observed in AIA, but decelerating from ≈?320 to ≈?254 km?s^?1. These observations reveal the co-existence of both waves (i.e. coronal Moreton and EIT waves), and the type II radio burst seems to be associated with the coronal Moreton wave.     

Wavelet Analysis of the New Solar Neutrino Capture Rate Data for the Homestake Experiment

Wavelet analysis offers an alternative to Fourier based time- series analysis and is particularly useful when spectral features are time dependent. We analyze the solar neutrino capture rate of the radiochemical Homestake chlorine experiment with abbreviated Morlet wavelets, using Foster's (AJ, 111,1709(1996)) rescaled wavelet technique. We emphasize the complementarity of wavelet analysis to Fourier analysis. Wavelet analysis confirms the results of previously undertaken Fourier analysis. The Homestake data seem to contain a harmonic content with periodicities of 4.76 yr, 1.89 yr, 0.85 yr, and 0.51 yr. Wavelet analysis reveals that the 4.76 yr and 1.89 yr periods show an almost constant behavior over the 25 yr Homestake data record, while the 0.85 yr and 0.51 yr periods exhibit a transient phenomenon. The analysis does not show strong evidence for a period of the solar 11 yr cycle. This revised version was published online in July 2006 with corrections to the Cover Date.     

Power Spectrum Analysis of Physikalisch-Technische Bundesanstalt Decay-Rate Data: Evidence for Solar Rotational Modulation

Evidence for an anomalous annual periodicity in certain nuclear-decay data has led to speculation on a possible solar influence on nuclear processes. We have recently analyzed data concerning the decay rates of ³⁶Cl and ³²Si, acquired at the Brookhaven National Laboratory (BNL), to search for evidence that might be indicative of a process involving solar rotation. Smoothing of the power spectrum by weighted-running-mean analysis leads to a significant peak at frequency 11.18 year⁻¹, which is lower than the equatorial synodic rotation rates of the convection and radiative zones. This article concerns measurements of the decay rates of ²²⁶Ra acquired at the Physikalisch-Technische Bundesanstalt (PTB) in Germany. We find that a similar (but not identical) analysis yields a significant peak in the PTB dataset at frequency 11.21 year⁻¹, and a peak in the BNL dataset at 11.25 year⁻¹. The change in the BNL result is not significant, since the uncertainties in the BNL and PTB analyses are estimated to be 0.13 year⁻¹ and 0.07 year⁻¹, respectively. Combining the two running means by forming the joint power statistic leads to a highly significant peak at frequency 11.23 year⁻¹. We will briefly comment on the possible implications of these results for solar physics and for particle physics.     

太阳射电分米波U型暴分析

本文介绍了由捷克Ondˇrejov天文台观测到的 1 992年 8月 2 2日 1 2 :36 :2 6— 1 2 :36 :32UT发生的U型暴 ,U型暴的频率范围为 1 .0— 2 .8GHz,在国际上尚属首例 .从分析得到以下几点结论 :(1 )上下臂的频漂率分别为 1 .2 5和 0 .2 2 5GHz/s,其电子束流的速度分别为 0 .38c和 0 .2 6c ,它是由等离子体二次谐波发射造成的 .(2 )上升臂的爆发衰减时间常数大于下降臂的 .(3)频谱极大频率随时间变化呈现出从高频到低频再到高频的变化 .(4)上升臂的频宽大于下降臂的约一倍左右 ,这与上升臂频漂远大于下降臂的有关 .(5 )从频宽得到上、下臂的速度弥散分别为 (Δvv) a=0 .42和 (Δvv) d=0 .47.     

Compton γ射线望远镜的直接解调成像

Ｃｏｍｐｔｏｎγ射线望远镜ＣＯＭＰＴＥＬ／ＣＧＲＯ工作于０．７５－３０ＭｅＶ能区，本文应用直接解调方法分析ＣＧＲＯ＃１观测的ＣＯＭＰＴＥＬ数据，准确定出Ｃｒａｂγ射线源的位置，在１０－３０ＭｅＶ能区，分辨开最大似然法所不能完全分辨的Ｃｒａｂγ射线源和类星体ＰＫＳ０５２８＋１３４，得出优于传统成像方法所得的成像结果．应用直接成像方法处理γ射线脉冲星Ｇｅｍｉｎｇａ分位相数据，发现Ｇｅｍｉｎｇａ在１０－３０ＭｅＶ能区仍存在辐射，辐射集中在Ｇｅｍｉｎｇａ第一个峰的位相区域．结果表明，应用直接解调方法对Ｃｏｍｐｔｏｎ望远镜数据作成像分析是完全可行的     

Determination of Electron Flux Spectra in a Solar Flare with an Augmented Regularization Method: Application to Rhessi Data

Kontar et al. (2004) have shown how to recover mean source electron spectra in solar flares through a physical constraint regularization analysis of the bremsstrahlung photon spectra I() that they produce. They emphasize the use of non-square inversion techniques, and preconditioning combined with physical properties of the spectra to achieve the most meaningful solution to the problem. Higher-order regularization techniques may be used to generate forms with certain desirable properties (e.g., higher-order derivatives). They further note that such analysis may be used to infer properties of the electron energy spectra at energies well above the maximum photon energy observed. In this paper we apply these techniques to data from a solar flare observed by RHESSI on 26 February, 2002. Results using different orders of regularization are presented and compared for various time intervals. Clear evidence is presented for a change in the value of the high-energy cutoff in the mean source electron spectrum with time. We also show how the construction of the injected electron spectrum F₀(E₀) (assuming that Coulomb collisions in a cold target dominate the electron transport) is facilitated by the use of higher-order regularization methods.