Size Distrtibutions of the >10 MeV Solar Proton Events

As has been recognized recently, data on size (frequency) distributions for different sets of solar flare parameters are very helpful in modeling flare and acceleration processes. Relying upon a new arising paradigm of particle acceleration at different sources at/near the Sun (flares, shock waves, etc.), in this paper, we analyze long-term data (1955–1996) from several Catalogues of Solar Proton Events (SPEs). Above 1 p.f.u. (proton cm^–2 s^–1 sr^–1) of the >10 MeV protons, we have separated in all 320 events associated with identified sources (flares). Then, within this database of flare-related events, a second group (a subgroup) has been formed of the 159 events, additionally having a certain or probable sudden storm commencement (SSC) association (SSC-related events). The basic result is that the power-law slope of size distribution for the 320 flare-related events at integral energy intensities is about 1.37 ± 0.05 over the entire range of the proton intensities, from 1.0 to 10⁵ p.f.u. This slope is in general agreement with earlier analyses of integral energy distributions, but steeper than that for differential energy distributions. A second result is that the SSC-associated events have a double power-law distribution with two different exponents, near 1.00 ± 0.04 and 1.53 ± 0.03 below and above 10³ p.f.u., respectively. The longitude distributions of the proper sources for these two groups display different behaviour suggesting different origins of the two particle populations. A certain difference was also found to exist in the slopes of integral size distributions at >10 MeV and >500 MeV. This may point to a dependence of slope on the proton energy under consideration.     

Shannon Entropy-Based Prediction of Solar Cycle 25

A new model is proposed to forecast the peak sunspot activity of the upcoming solar cycle (SC) using Shannon entropy estimates related to the declining phase of the preceding SC. Daily and monthly smoothed international sunspot numbers are used in the present study. The Shannon entropy is the measure of inherent randomness in the SC and is found to vary with the phase of an SC as it progresses. In this model each SC with length \(T_{\mathrm{cy}}\) is divided into five equal parts of duration \(T_{\mathrm{cy}}/5\). Each part is considered as one phase, and they are sequentially termed P1, P2, P3, P4, and P5. The Shannon entropy estimates for each of these five phases are obtained for the \(n\)th SC starting from \(n=10\,\mbox{--}\,23\). We find that the Shannon entropy during the ending phase (P5) of the \(n\)th SC can be efficiently used to predict the peak smoothed sunspot number of the \((n+1)\)th SC, i.e. \(S_{\mathrm{max}}^{n+1}\). The prediction equation derived in this study has a good correlation coefficient of 0.94. A noticeable decrease in entropy from 4.66 to 3.89 is encountered during P5 of SCs 22 to 23. The entropy value for P5 of the present SC 24 is not available as it has not yet ceased. However, if we assume that the fall in entropy continues for SC 24 at the same rate as that for SC 23, then we predict the peak smoothed sunspot number of 63±11.3 for SC 25. It is suggested that the upcoming SC 25 will be significantly weaker and comparable to the solar activity observed during the Dalton minimum in the past.     

An Early Prediction of the Amplitude of Solar Cycle 25

A “Solar Dynamo” (SODA) Index prediction of the amplitude of Solar Cycle 25 is described. The SODA Index combines values of the solar polar magnetic field and the solar spectral irradiance at 10.7 cm to create a precursor of future solar activity. The result is an envelope of solar activity that minimizes the 11-year period of the sunspot cycle. We show that the variation in time of the SODA Index is similar to several wavelet transforms of the solar spectral irradiance at 10.7 cm. Polar field predictions for Solar Cycles 21?–?24 are used to show the success of the polar field precursor in previous sunspot cycles. Using the present value of the SODA index, we estimate that the next cycle’s smoothed peak activity will be about \(140 \pm30\) solar flux units for the 10.7 cm radio flux and a Version 2 sunspot number of \(135 \pm25\). This suggests that Solar Cycle 25 will be comparable to Solar Cycle 24. The estimated peak is expected to occur near \(2025.2 \pm1.5\) year. Because the current approach uses data prior to solar minimum, these estimates may improve as the upcoming solar minimum draws closer.     

Solar flare line emission between 6 Å and 25 Å

A list of emission lines in the spectra of solar flares between 6 Å and 25 Å has been compiled using data obtained with a KAP crystal spectrometer on the OSO-5 satellite. The emission lines have been classified according to their sensitivity to flare activity. This classification provides a method for discriminating between iron in high stages of ionization (Fe xx-Fe xxv) and lower stages (Fe xvii- Fe xix), the lines of which are both present in the same spectral region during flares. Identifications consistent with these classifications are proposed. Anomalous intensities in the spectra of Fe xvii and Fe xx are pointed out, and implications of the observations for models of the X-ray emitting regions are discussed.     

Quiet-time $0.04\,\mbox{--}\,2\mbox{ MeV}/\mbox{nucleon}$ Ions at 1 AU in Solar Cycles 23 and 24

The fluxes of ³He, ⁴He, C, O, and Fe ions at low energies (about \(0.04\,\mbox{--} \,2~\mbox{MeV}/\mbox{nucleon}\)) are studied during quiet periods in Solar Cycles (SC) 23 and 24 using data from the ULEIS/ACE instrument. In selecting quiet periods (the definition is given in Section 2.1), additional data from EPHIN/SOHO and EPAM/ACE were also used. The analysis of the ion energy spectra and their relative abundances shows that their behavior is governed by their first-ionization potential. Substantial differences in the ion energy spectra in two consecutive solar cycles are observed during the quiet periods selected. Quiet-time fluxes are divided into three distinct types according to the \({\sim}\,80\,\mbox{--}\,320~\mbox{keV}/\mbox{nucleon}\) Fe/O ratio. Our results confirm the earlier observation that these types of suprathermal particles have different origins, that is, they represent different seed populations that are accelerated by different processes. Except for the solar activity minimum, the Fe/O ratio during quiet-time periods correspond either to the abundances of ions in particle fluxes accelerated in impulsive solar flares or to the mean abundances of elements in the solar corona. At the activity minimum, this ratio takes on values that are characteristic for the solar wind. These results indicate that the background fluxes of low-energy particles in the ascending, maximum, and decay phases of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal energies and ions accelerated in small impulsive solar flares rich in Fe, while the contribution of remnants from earlier SEP events cannot be excluded. The comparison of suprathermal ion abundances during the first five years of SC 23 and SC 24 suggests that the quiet-time and non-quiet fluxes of Fe and ³He were lower in SC 24.     

新疆天文台25m南山射电望远镜日照温度场研究

中国科学院新疆天文台25 m南山射电望远镜(25 m NSRT)受日照导致天线结构温度不均匀,其指向精度和效率均有一定程度的损失.为研究25 m NSRT日照下的热力学特性,构建了晴空下射电望远镜热环境参数和热力学有限元模型,考虑了射电望远镜背架、面板等结构件对光线的反射和遮挡作用,通过比较25 m NSRT典型观测工况下各构件的平均温度、均方根温差、单位温差特征距离等特性参数,发现各部件热容量的差异是天线部件间存在大尺度温差现象的主要原因;分析了各类俯仰角和太阳照射角下天线背架结构的温度分布特征,表明日照区域的背架结构温度呈近似线性分布,平均梯度可达0.25℃·m^-1.     

Flattening Index of the Solar Corona and the Solar Cycle

The photometrical flattening index of the solar corona a+b is defined according to Ludendorff. In this paper we have investigated how the flattening index varies with respect to the phase of solar activity and the sunspot number. We have compiled 170 values of the flattening index using the data on 60 total solar eclipses from 1851 to 2010. We have found that the flattening index takes values from 0 to 0.4, and is anticorrelated with solar activity. The value of the flattening index at the beginning of solar cycle 24 was used as a precursor to forecast the amplitude of the cycle. It was found that the amplitude of solar cycle 24 will be about 95 in terms of the smoothed monthly sunspot numbers.     

Temperature of Solar Prominences Obtained with the Fast Imaging Solar Spectrograph on the 1.6 m New Solar Telescope at the Big Bear Solar Observatory

We observed solar prominences with the Fast Imaging Solar Spectrograph (FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August 2011. To determine the temperature of the prominence material, we applied a nonlinear least-squares fitting of the radiative transfer model. From the Doppler broadening of the Hα and Ca ii lines, we determined the temperature and nonthermal velocity separately. The ranges of temperature and nonthermal velocity were 4000?–?20?000 K and 4?–?11 km?s^?1. We also found that the temperature varied much from point to point within one prominence.     

Element Abundances in Solar Energetic Particles and the Solar Corona

This is a study of abundances of the elements He, C, N, O, Ne, Mg, Si, S, Ar, Ca, and Fe in solar energetic particles (SEPs) in the 2?–?15 MeV?amu^?1 region measured on the Wind spacecraft during 54 large SEP events occurring between November 1994 and June 2012. The origin of most of the temporal and spatial variations in abundances of the heavier elements lies in rigidity-dependent scattering during transport of the particles away from the site of acceleration at shock waves driven out from the Sun by coronal mass ejections (CMEs). Variation in the abundance of Fe is correlated with the Fe spectral index, as expected from scattering theory but not previously noted. Clustering of Fe abundances during the “reservoir” period, late in SEP events, is also newly reported. Transport-induced enhancements in one region are balanced by depletions in another, thus, averaging over these variations produces SEP abundances that are energy independent, confirms previous SEP abundances in this energy region, and provides a credible measure of element abundances in the solar corona. These SEP-determined coronal abundances differ from those in the solar photosphere by a well-known function that depends upon the first ionization potential (FIP) or ionization time of the element.     

Fast Imaging Solar Spectrograph of the 1.6 Meter New Solar Telescope at Big Bear Solar Observatory

For high resolution spectral observations of the Sun – particularly its chromosphere, we have developed a dual-band echelle spectrograph named Fast Imaging Solar Spectrograph (FISS), and installed it in a vertical optical table in the Coudé Lab of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. This instrument can cover any part of the visible and near-infrared spectrum, but it usually records the Hα band and the Ca ii 8542 Å band simultaneously using two CCD cameras, producing data well suited for the study of the structure and dynamics of the chromosphere and filaments/prominences. The instrument does imaging of high quality using a fast scan of the slit across the field of view with the aid of adaptive optics. We describe its design, specifics, and performance as well as data processing     

Global Forces in Eruptive Solar Flares: The Lorentz Force Acting on the Solar Atmosphere and the Solar Interior

We compute the change in the Lorentz force integrated over the outer solar atmosphere implied by observed changes in vector magnetograms that occur during large, eruptive solar flares. This force perturbation should be balanced by an equal and opposite force perturbation acting on the solar photosphere and solar interior. The resulting expression for the estimated force change in the solar interior generalizes the earlier expression presented by Hudson, Fisher, and Welsch (Astron. Soc. Pac. CS-383, 221, 2008), providing horizontal as well as vertical force components, and provides a more accurate result for the vertical component of the perturbed force. We show that magnetic eruptions should result in the magnetic field at the photosphere becoming more horizontal, and hence should result in a downward (toward the solar interior) force change acting on the photosphere and solar interior, as recently argued from an analysis of magnetogram data by Wang and Liu (Astrophys. J. Lett. 716, L195, 2010). We suggest the existence of an observational relationship between the force change computed from changes in the vector magnetograms, the outward momentum carried by the ejecta from the flare, and the properties of the helioseismic disturbance driven by the downward force change. We use the impulse driven by the Lorentz-force change in the outer solar atmosphere to derive an upper limit to the mass of erupting plasma that can escape from the Sun. Finally, we compare the expected Lorentz-force change at the photosphere with simple estimates from flare-driven gasdynamic disturbances and from an estimate of the perturbed pressure from radiative backwarming of the photosphere in flaring conditions.     

Intermittency of the Solar Magnetic Field and Solar Magnetic Activity Cycle

Small-scale solar magnetic fields demonstrate features of fractal intermittent behavior, which requires quantification. For this purpose we investigate how the observational estimate of the solar magnetic flux density \(B\) depends on resolution \(D\) in order to obtain the scaling \(\ln B_{D} = - k \ln D +a\) in a reasonably wide range. The quantity \(k\) demonstrates cyclic variations typical of a solar activity cycle. In addition, \(k\) depends on the magnetic flux density, i.e. the ratio of the magnetic flux to the area over which the flux is calculated, at a given instant. The quantity \(a\) demonstrates some cyclic variation, but it is much weaker than in the case of \(k\). The scaling obtained generalizes previous scalings found for the particular cycle phases. The scaling is typical of fractal structures. In our opinion, the results obtained trace small-scale action in the solar convective zone and its coexistence with the conventional large-scale solar dynamo based on differential rotation and mirror-asymmetric convection.     

太阳活动与太阳自转速率变化关系的分析

研究发现,太阳自转速率的变化与太阳活动之间存在一定的联系,但是不同学者的研究结论存在着矛盾:有的认为两者为正相关,而有的却认为是负相关.究竟两者之间是什么关系,需要做进一步深入的分析.利用EEMD (Ensemble Empirical Mode Decomposition)等方法对太阳自转速率和太阳黑子数据序列进行相关关系以及相位关系的计算和分析,以探讨太阳自转速率变化与太阳活动之间的关系.研究发现:两者的长期趋势项分量呈显著负相关;在11 yr左右周期分量上,观测到的太阳自转速率滞后太阳黑子的变化约2 yr时,呈显著负相关关系,超前3 yr时呈现次显著的正相关;对太阳活动第12–23周各周内部太阳黑子与太阳自转速率的相关分析表明,两者的关系比较复杂,但负相关关系更为显著.这为进一步理解太阳活动变化与太阳自转速率变化之间的成因联系提供了新的依据.     

Contribution to the Solar Mean Magnetic Field from Different Solar Regions

Seven-year-long seeing-free observations of solar magnetic fields with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) were used to study the sources of the solar mean magnetic field, SMMF, defined as the net line-of-sight magnetic flux divided over the solar disk area. To evaluate the contribution of different regions to the SMMF, we separated all the pixels of each SDO/HMI magnetogram into three subsets: weak (\(B^{\mathrm{W}}\)), intermediate (\(B^{\mathrm{I}}\)), and strong (\(B^{\mathrm{S}}\)) fields. The \(B^{\mathrm{W}}\) component represents areas with magnetic flux densities below the chosen threshold; the \(B^{\mathrm{I}}\) component is mainly represented by network fields, remains of decayed active regions (ARs), and ephemeral regions. The \(B^{\mathrm{S}}\) component consists of magnetic elements in ARs. To derive the contribution of a subset to the total SMMF, the linear regression coefficients between the corresponding component and the SMMF were calculated. We found that i) when the threshold level of 30 Mx?cm^?2 is applied, the \(B^{\mathrm{I}}\) and \(B^{\mathrm{S}}\) components together contribute from 65% to 95% of the SMMF, while the fraction of the occupied area varies in a range of 2?–?6% of the disk area; ii) as the threshold magnitude is lowered to 6 Mx?cm^?2, the contribution from \(B^{\mathrm{I}}+B^{\mathrm{S}}\) grows to 98%, and the fraction of the occupied area reaches a value of about 40% of the solar disk. In summary, we found that regardless of the threshold level, only a small part of the solar disk area contributes to the SMMF. This means that the photospheric magnetic structure is an intermittent inherently porous medium, resembling a percolation cluster. These findings suggest that the long-standing concept that continuous vast unipolar areas on the solar surface are the source of the SMMF may need to be reconsidered.     

Solar Cycle Predictions based on Solar Activity at Different Solar Latitudes

Many methods of predictions of sunspot maximum number use data before or at the preceding sunspot minimum to correlate with the following sunspot maximum of the same cycle, which occurs a few years later. Kane and Trivedi (Solar Phys. 68, 135, 1980) found that correlations of R _z(max) (the maximum in the 12-month running means of sunspot number R _z) with R _z(min) (the minimum in the 12-month running means of sunspot number R _z) in the solar latitude belt 20° – 40°, particularly in the southern hemisphere, exceeded 0.6 and was still higher (0.86) for the narrower belt > 30° S. Recently, Javaraiah (Mon. Not. Roy. Astron. Soc. 377, L34, 2007) studied the relationship of sunspot areas at different solar latitudes and reported correlations 0.95 – 0.97 between minima and maxima of sunspot areas at low latitudes and sunspot maxima of the next cycle, and predictions could be made with an antecedence of more than 11 years. For the present study, we selected another parameter, namely, SGN, the sunspot group number (irrespective of their areas) and found that SGN(min) during a sunspot minimum year at latitudes > 30° S had a correlation +0.78±0.11 with the sunspot number R _z(max) of the same cycle. Also, the SGN during a sunspot minimum year in the latitude belt (10° – 30° N) had a correlation +0.87±0.07 with the sunspot number R _z(max) of the next cycle. We obtain an appropriate regression equation, from which our prediction for the coming cycle 24 is R _z(max )=129.7±16.3.     

Probing the Fundamental Physics of the Solar Corona with Lunar Solar Occultation Observations

Imaging and spectroscopy of the solar corona, coupled with polarimetry, are the only tools available at present to capture signatures of physical processes responsible for coronal heating and solar wind acceleration within the first few solar radii above the solar limb. With the recent advent of improved detector technology and image processing techniques, broad-band white light and narrow-band multi-wavelength observations of coronal forbidden lines, made during total solar eclipses, have started to yield new views about the thermodynamic and magnetic properties of coronal structures. This paper outlines these unique capabilities, which until present, have been feasible primarily with observations during natural total solar eclipses. This work also draws attention to the exciting possibility of greatly increasing the frequency and duration of solar eclipse observations with Moon orbiting observatories utilizing lunar limb occultation of the solar disk for coronal measurements.     

第22和23太阳周太阳活动预测

本文首先分析指出第22太阳周前半周的太阳活动所具有的特点:(1)有最高的起始极小值;(2)上升速度快;(3)升段时间最短;(4)峰期长,可能有双峰;(5)个别时段活动水平极高.然后对第22周后半周的活动情况做了预计:在后半周将可能观测到大约2800个活动区,28000个耀斑,210个X级X射线爆发和大约80次太阳质子事件.最后,应用本文给出的太阳周参量关系式.预报第23周太阳黑子数月均平滑值的峰值为119,位于2001.6年.