1996-2002年太阳耀斑的统计分析

分析了1996-2002年南北半球的太阳黑子相对数和南北半球太阳X射线耀斑级别(简称Imp)≥M1．0的太阳X射线耀斑的特征和不对称性．分析结果表明，南北半球的太阳耀斑活动的程度交替上升，在2001年7月以前北半球的太阳耀斑活动强于南半球，2001年7月开始耀斑活动逐渐以南半球为主．本文还逐月分析了1996—2001年南北半球的耀斑指数．2000年7月为第23周太阳指数最大的一个月，与第23周太阳黑子相对数最大月均值吻合．     

Solar flares: an overview.

This is a survey of solar phenomena and physical models that may be useful for improving forecasts of solar flares and proton storms in interplanetary space. Knowledge of the physical processes that accelerate protons has advanced because of gamma-ray and X-ray observations from the Solar Maximum Mission telescopes. Protons are accelerated at the onset of flares, but the duration of any subsequent proton storm at 1 AU depends on the structure of the interplanetary fields. X-ray images of the solar corona show possible fast proton escape paths. Magnetographs and high-resolution visible-band images show the magnetic field structure near the acceleration region and the heating effects of sunward-directed protons. Preflare magnetic field growth and shear may be the most important clues to the physical processes that generate high energy solar particles. Any dramatic improvement in flare forecasts will require high resolution solar telescopes in space. Several possibilities for improvements in the art of flare forecasting are presented, among them: the use of acoustic tomography to probe for subsurface magnetic fields; a satellite-borne solar magnetograph; and an X-ray telescope to monitor the corona for eruptions.     

Sun CubE OnE: A multi-wavelength synoptic solar micro satellite

The Sun cubE onE (SEE) is a 12U CubeSat mission proposed for a phase A/B study to the Italian Space Agency that will investigate Gamma and X-ray fluxes and ultraviolet (UV) solar emission to support studies in Sun-Earth interaction and Space Weather from LEO. More in detail, SEE’s primary goals are to measure the flares emission from soft-X to Gamma ray energy range and to monitor the solar activity in the Fraunhofer Mg II doublet at 280 nm, taking advantage of a full disk imager payload. The Gamma and X-ray fluxes will be studied with unprecedented temporal resolution and with a multi-wavelength approach thanks to the combined use of silicon photodiode and silicon photomultiplier (SiPM) -based detectors. The flare spectrum will be explored from the keV to the MeV range of energies by the same payload, and with a cadence up to 10 kHz and with single-photon detection capabilities to unveil the sources of the solar flares. The energy range covers the same bands used by GOES satellites, which are the standard bands for flare magnitude definition. At the same time SiPM detectors combined with scintillators allow to cover the non-thermal bremsstrahlung emission in the gamma energy range. Given its UV imaging capabilities, SEE will be a key space asset to support detailed studies on solar activity, especially in relation to ultraviolet radiation which strongly interacts with the upper layers of the Earth’s atmosphere, and in relation to space safety, included in the field of human space exploration. The main goal for the UV payload is to study the evolution of the solar UV emission in the Mg II band at two different time scales: yearly variations along the solar cycle and transient variations during flare events. The Mg II index is commonly used as a proxy of the solar activity in the Sun-as-a-star paradigm, in which solar irradiance variations in the UV correlate with the variations in stratospheric ozone concentrations and other physical parameters of the Earth high atmosphere. SEE data will be used together with space and ground-based observatories that provide Solar data (e.g. Solar Orbiter, IRIS, GONG, TSST), high energy particle fluxes (e.g. GOES, MAXI, CSES) and geomagnetic data in a multi-instrument/multi-wavelength/multi-messenger approach.     

Properties and relationship between solar eruptive flares and Coronal Mass Ejections during rising phase of Solar Cycles 23 and 24

Statistical relationship between major flares and the associated CMEs during rising phases of Solar Cycles 23 and 24 are studied. Totally more than 6000 and 10,000 CMEs were observed by SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle Spectrometric Coronagraph) during 23rd [May 1996–June 2002] and 24th [December 2008–December 2014] solar cycles, respectively. In particular, we studied the relationship between properties of flares and CMEs using the limb events (longitude 70–85°) to avoid projection effects of CMEs and partial occultation of flares that occurred near 90°. After selecting a sample of limb flares, we used certain spatial and temporal constraints to find the flare-CME pairs. Using these constraints, we compiled 129 events in Solar Cycle 23 and 92 events in Solar Cycle 24. We compared the flare-CME relationship in the two solar cycles and no significant differences are found between the two cycles. We only found out that the CME mean width was slightly larger and the CME mean acceleration was slightly higher in cycle 24, and that there was somewhat a better relation between flare flux and CME deceleration in cycle 24 than in cycle 23.     

Detection of solar neutrons on a long duration balloon flight

The observation of large solar flares on high altitude balloons requires long duration balloon flights because large flares are infrequent and cannot be predicted with enough reliability and lead time to allow a conventional balloon to be launched and reach altitude before the flare occurs. With the many weeks at float altitude expected for a long duration flight, the probability of “catching” a large flare during solar maximum becomes reasonably high and the study of phenomena which heretofore have required a satellite become accessible to a balloon platform. One example of this type of experiment is the observation of neutrons produced by the interaction of flare accelerated nucleons with the solar atmosphere. Because the neutrons are produced immediately by the flare accelerated particles and are unaffected by their transmission through the upper solar atmosphere and the intervening magnetic fields, their observation at 1 A.U. will provide direct information on the flare acceleration process. Specifically, a measurement of the neutron energy and time spectra will yield the energy spectrum of the charged nucleons in the interval 50 to 500 MeV/amu, the charged particle anisotropy, the height of the acceleration region for limb flares, and information on the two-stage acceleration process. Because the γ-ray spectrum is also sensitive to these factors, a combined neutron and γ-ray measurement will provide a much more stringent test of flare models than either done separately. CWRU and the University of Melbourne have designed the EOSCOR (Extended Observation of Solar and Cosmic Radiation) detector to have the necessary sensitivity to detect neutrons from a flare 0.1 the size of the 4 Aug. 1972 event and to be compatible with the constraints of the long duration balloon system. The detector has been test flown on short duration balloon flights and calibrated at E_n = 38, 58, and 118 MeV. It is planned to launch it on a long duration balloon flight from Australia in December 1982 when simultaneous γ-ray observations will be possible with the SMM and/or HINTORI satellites.     

基于长短期记忆神经网络的太阳耀斑短期预报

提出了一个基于长短期记忆神经网络的耀斑预报模型,利用过去24 h太阳活动区的磁场变化时序构建样本,通过长短期记忆神经网络对磁场特征时序演化进行分析,预报未来48 h内是否发生≥M级别耀斑事件。使用的数据集为2010年5月到2017年5月所有活动区样本,选取了SDO/HMI SHARP的10个磁场特征参量。在建模过程中通过XGBoost方法选取权重、增益率和覆盖率均较高的6个特征参量作为输入参数。通过测试对比,模型的虚报率和准确率与传统机器学习模型相近,报准率和临界成功指数分别为0.7483和0.7402,优于传统机器学习模型。模型总体效果优于传统机器学习模型。      

Relationship of solar flare accelerated particles to solar energetic particles (SEPs) observed in the interplanetary medium

Observations of hard X-ray (HXR)/γ-ray continuum and γ-ray lines produced by energetic electrons and ions, respectively, colliding with the solar atmosphere, have shown that large solar flares can accelerate ions up to many GeV and electrons up to hundreds of MeV. Solar energetic particles (SEPs) are observed by spacecraft near 1 AU and by ground-based instrumentation to extend up to similar energies as in large SEP events, but it appears that a different acceleration process, one associated with fast coronal mass ejections is responsible. Much weaker SEP events are observed that are generally rich in electrons, ³He, and heavy elements. The energetic particles in these events appear to be similar to those accelerated in flares. The Ramaty high energy solar spectroscopic imager (RHESSI) mission provides high-resolution spectroscopy and imaging of flare HXRs and γ-rays. Such observations can provide information on the location, energy spectra, and composition of the flare accelerated energetic particles at the Sun. Here, preliminary comparisons of the RHESSI observations with observations of both energetic electron and ion near 1 AU are reviewed, and the implications for the particle acceleration and escape processes are discussed.     

Test alert service against very large SEP Events

The Aragats Solar Environment Center provides real time monitoring of different components of secondary cosmic ray fluxes. We plan to use this information to establish an early warning alert system against extreme, very large solar particle events with hard spectra, dangerous for satellite electronics and for the crew of the Space Station. Neutron monitors operating at altitude 2000 and 3200 m are continuously gathering data to detect possible abrupt variations of the particle count rates. Additional high precision detectors measuring muon and electron fluxes, along with directional information are under construction on Mt. Aragats. Registered ground level enhancements, in neutron and muon fluxes along with correlations between different species of secondary cosmic rays are analyzed to reveal possible correlations with expected times of arrival of dangerous solar energetic particles.     

Initial results from the repaired solar maximum mission and future prospects

Goals of the recently repaired Solar Maximum Mission Observatory are outlined, including continued emphasis on diagnosing impulsive phase of flares, studies of prominence and coronal plasmas, solar cycle variations of flares, the corona and solar irradiance, and comets. Some preliminary observations taken after the repair are shown, particularly of the X13 flare of April 1984.     

Results of solar observations by the CORONAS-F payload

The CORONAS-F mission experiments and results have been reviewed. The observations with the DIFOS multi-channel photometer in a broad spectral range from 350 to 1500 nm have revealed the dependence of the relative amplitudes of p-modes of the global solar oscillations on the wavelength that agrees perfectly well with the earlier data obtained in a narrower spectral ranges. The SPIRIT EUV observations have enabled the study of various manifestations of solar activity and high-temperature events on the Sun. The data from the X-ray spectrometer RESIK, gamma spectrometer HELICON, flare spectrometer IRIS, amplitude–temporal spectrometer AVS-F, and X-ray spectrometer RPS-1 have been used to analyze the X- and gamma-ray emission from solar flares and for diagnostics of the flaring plasma. The absolute and relative content of various elements (such as potassium, argon, and sulfur) of solar plasma in flares has been determined for the first time with the X-ray spectrometer RESIK. The Solar Cosmic Ray Complex monitored the solar flare effects in the Earth’s environment. The UV emission variations recorded during solar flares in the vicinity of the 120-nm wavelength have been analyzed and the amplitude of relative variations has been determined.     

23rd solar cycle: Solar activity parameters and associated Forbush decreases

We report Forbush decreases (FD) in cosmic ray intensity from January 1996 to December 2008, the whole Solar Cycle 23rd. Statistical analysis is done for only 152 events for which associated solar flare position, flare classes, and Coronal Mass Ejections (CME) speed are given. We applied FD parameters taken from the Forbush Effects and Interplanetary Disturbances databases maintained by the Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation (IZMIRAN), obtained by processing the data of the worldwide neutron monitor network using the global survey method (GSM) (A. Belov et al., 2018). For the said number of events, we examine their effect on interplanetary space and the decrease of the galactic cosmic rays (GCR) near Earth. We found that the 11–20° latitudinal belt shows more FD- associated flare events than the other latitudinal belts, and on this belt, the Southern hemisphere is more active. The results reveal that FDs and solar flares are well correlated. Statistical analysis is carried out for the magnitude of the CR decrease with solar and geomagnetic parameters.     

太阳质子事件警报

采用人工神经网络预报方法,利用太阳耀斑的日面位置、X射线辐射的峰值流量及其上升时间、2695MHz和8800MHz微波辐射的半积分流量等5个物理参量,提出了一个新的太阳质子事件警报方案,预报太阳质子事件的发生及其流量和时间．该方案在本文检验中达到93．75％的预报准确率．     

The Neupert effect and new RHESSI measures of thetotal energy in electrons accelerated in solar flares

It is believed that a large fraction of the total energy released in a solar flare goes initially into acceleratedelectrons. These electrons generate the observed hard X-ray bremsstrahlung as they lose most of their energy by coulomb collisions in the lower corona and chromosphere. Results from the Solar Maximum Mission showed that there may be even more energy in accelerated electrons with energies above 25 keV than in the soft X-ray emitting thermal plasma. If this is the case, it is difficult to understand why the Neupert Effect — the empirical result that for many flares the time integral of the hard X-ray emission closely matches the temporal variation of the soft X-ray emission — is not more clearly observed in many flares. From recent studies, it appears that the fraction of the released energy going into accelerated electrons is lower, on average, for smaller flares than for larger flares. Also, from relative timing differences, about 25% of all flares are inconsistent with the Neupert Effect. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is uniquely capable of investigating the Neupert Effec since it covers soft X-rays down to 3 keV (when both attenuators are out of the field of view) and hard X-rays with keV energy resolution, arcsecond-class angular resolution, and sub-second time resolution. When combined with the anticipated observations from the Soft X-ray Imager on the next GOES satellite, these observations will provide us with the ability to track the Neupert Effect in space and time and learn more about the relation between plasma heating and particle acceleration. The early results from RHESSI show that the electron spectrum extends down to as low as 10 keV in many flares, thus increasing the total energy estimates of the accelerated electrons by an order of magnitude or more compared with the SMM values. This combined with the possible effects of filling factors smaller than unity for the soft X-ray plasma suggest that there is significantly more energy in nonthermal electrons than in the soft X-ray emitting plasma in many flares.     

太阳高能粒子事件强度与相关双CME事件关系的两个事例

太阳高能粒子事件常伴随太阳耀斑和日冕物质抛射事件(Coronal Mass Ejections,CME)出现,由于太阳高能粒子事件的关键因素是双CME的相互作用,利用SOHO卫星观测的高能粒子强度、耀斑强度以及CME的相对高度与时间,通过高度与时间拟合得到的速度,分析了2001年4月15日和2005年1月20日的太阳高能粒子事件强度与相关双CME事件的关系,发现这两个太阳高能粒子事件中E ≥ 10MeV质子的强度与双CME事件无关.因此在这两次太阳高能粒子事件早期,E ≥ 10MeV质子的强度只与相关太阳耀斑和CME有关.      

Nitric oxide density enhancements due to solar flares

A differential emission measure technique is used to determine flare spectra using solar observations from the soft X-ray instruments aboard the Thermosphere Ionosphere Mesosphere Energetics Dynamics and Solar Radiation and Climate Experiment satellites. We examine the effect of the solar flare soft X-ray energy input on the nitric oxide (NO) density in the lower thermosphere. The retrieved spectrum of the 28 October 2003 X18 flare is input to a photochemical thermospheric NO model to calculate the predicted flare NO enhancements. Model results are compared to Student Nitric Oxide Explorer Ultraviolet Spectrometer observations of this flare. We present results of this comparison and show that the model and data are in agreement. In addition, the NO density enhancements due to several flares are studied. We present results that show large solar flares can deposit the same amount of 0.1–2 and 0.1–7 nm energy to the thermosphere during a relatively short time as the Sun normally deposits in one day. The NO column density nearly doubles when the daily integrated energy above 5 J m⁻² is doubled.     

第21～24太阳周4类空间天气事件爆发特征统计分析

对第21～24太阳周不同等级的太阳X射线耀斑事件、太阳质子事件、地磁暴事件及高能电子增强事件的爆发频次特征进行统计，结果表明:太阳周耀斑爆发的总数量与该太阳周的黑子数峰值呈正比，耀斑总数、X级耀斑事件数与峰值的相关系数分别为0.974，0.997；太阳质子事件主要发生在峰年前后1～2年，约占总发生次数的80%，峰值通量大于10pfu （1 pfu=1 cm-2·sr-1·s-1）的质子事件中，84%伴有耀斑爆发，并且主要伴随M或X级耀斑，少量伴随C级耀斑，峰值通量大于1000pfu的质子事件中，98%伴随M或X级耀斑，并且以X级耀斑为主；第21，22，23和24太阳周发生地磁暴最频繁的时间分别在1982，1991，2003年和2015年，分别滞后黑子数峰值时间3年、2年、2年和1年；72%的高能电子增强事件发生在太阳周下降期，24%的高能电子增强事件发生在太阳周上升期.      

Multi-wavelength observations of the pre-cursor phase of solar flares

Observational studies of the pre-cursor phase of solar flares have shown that there are many and varied signatures that may or may not indicate the probable onset of a flare. Combining data from Yohkoh, SOHO and TRACE and more recent observations from RHESSI, SOHO and TRACE we, investigate the relationships between the different manifestations of pre-flare behaviour in two solar flares with a view to determining how they are related to the subsequent flare energy release. We find that in one case the preflare activity seems strongly related to the subsequent flare and probably represents a build-up of energy in the active region prior to flare onset. The second case we find to be less clear cut suggesting that significant further work remains to be done in order to determine which pre-flare signatures are most useful in indicating the build-up to flare onset.     

Recent advances in observations and modeling of the solar ultraviolet and X-ray spectral irradiance

There have been significant, recent advances in understanding the solar ultraviolet (UV) and X-ray spectral irradiance from several different satellite missions and from new efforts in modeling the variations of the solar spectral irradiance. The recent satellite missions with solar UV and X-ray spectral irradiance observations include the X-ray Sensor (XRS) aboard the series of NOAA GOES spacecraft, the Upper Atmosphere Research Satellite (UARS), the SOHO Solar EUV Monitor (SEM), the Solar XUV Photometers (SXP) on the Student Nitric Oxide Explorer (SNOE), the Solar EUV Experiment (SEE) aboard the Thermosphere, Ionosphere, Mesosphere, Dynamics, and Energetics (TIMED) satellite, and the Solar Radiation and Climate Experiment (SORCE) satellite. The combination of these measurements is providing new results on the variability of the solar ultraviolet irradiance throughout the ultraviolet range shortward of 200 nm and over a wide range of time scales ranging from years to seconds. The solar UV variations of flares are especially important for space weather applications and upper atmosphere research, and the period of intense solar storms in October–November 2003 has provided a wealth of new information about solar flares. The new efforts in modeling these solar UV spectral irradiance variations range from simple empirical models that use solar proxies to more complicated physics-based models that use emission measure techniques. These new models provide better understanding and insight into why the solar UV irradiance varies, and they can be used at times when solar observations are not available for atmospheric studies.     

太阳耀斑对电离层总电子含量的影响

本文分析了1978—1979年1级以上的太阳耀斑对电离层总电子含量的影响. 给出了不同持续时间、不同亮度、不同季节、发生在日面不同位置上的太阳耀斑对电离层总电子含量的影响.分析结果表明,持续时间大于等于1.5小时的耀斑对电子含量有明显的扰动,耀斑出现后电子含量随之增加,在第4—5天增加到最大值,扰动持续数日;持续时间小于1.5小时的耀斑对电子含量影响甚微;非亮耀斑对电子含量的扰动小于亮耀斑;夏季出现的耀斑对电子含量无明显扰动,只有冬季出现的亮耀斑对电子含量有明显的扰动;太阳耀斑扰动电子含量有明显的日面位置东西不对称性,只有出现在日面东边、特别是E₃区的太阳耀斑对电子含量才有明显的扰动.      

SMY和第21太阳周期间地磁及太阳活动特点的分析

本文比较第17—21太阳周黑子数、地磁A_p指数、各周极大年≥2级耀斑数、磁暴数及第一、二、三大磁暴情况;分析了≥2级耀斑数及磁暴的分布。21周3级耀斑对应磁暴比例低于19、20周,Ⅳ型及米波射电爆发是产生磁暴的重要条件。进一步分析了21周最大磁暴、最大射电爆发引起的磁暴,最严重的电离层短波通讯干扰及有明亮物质抛射的大耀斑、双带大耀斑引起的磁暴等典型例子。最后对SMY期间22个无黑子耀斑作了分析,它们可能引起中小幅度的磁暴。