ENSO Index Variations and Links with Solar and Volcanic Activity

In this paper, we investigated the Oceanic Niño Index (ONI), for simplicity called in this paper an El Nino Southern Oscillation (ENSO) index in 1950-2023 by applying the wavelet spectral transform and the IBM SPSS correlations analysis. ONI follows the three months’ current measurements of the average temperature of the sea surface in the East-Central tropical part of the Pacific Ocean nearby the international line of the date change over the average sea surface temperature over the past 30 years. The ENSO index is found to have a strong (>87%) correlation with the Global Land-Ocean Temperature (GLOT). The scatter plots of the ENSO-GLOT correlation with the linear and cubic fits have shown that the ENSO index is better fit by the cubic polynomial increasing proportionally to a cubic power of the GLOT variations. The wavelet analysis allowed us to detect the two key periods in the ENSO (ONI) index: 4 - 5 years and 12 years. The smaller period of 4.5 years can be linked to the motion of tectonic plates while the larger period of 12 years is shown to have a noticeable correlation of 25% with frequencies of the underwater (submarine) volcanic eruptions in the areas with ENSO occurrences. Not withholding any local terrestrial factors considered to contribute to the ENSO occurrences, we investigated the possibility of the volcanic eruptions causing ENSO to be also induced by the tidal forces of Jupiter and Sun showing the correlation of the underwater volcanic eruption frequency with the Jupiter-Earth distances to be 12% and with the Sun-Earth distances, induced by the solar inertial motion, in January, when the Earth is turned to the Sun with the southern hemisphere where the ENSO occurs, to become 15%. Hence, the underwater volcanic eruptions induced by tidal forces of Jupiter and Sun can be the essential additional factors imposing this 12 year period of the ENSO (ONI) index variations.

Predicting the 25th solar cycle using deep learning methods based on sunspot area data

It is a significant task to predict the solar activity for space weather and solar physics. All kinds of approaches have been used to forecast solar activities, and they have been applied to many areas such as the solar dynamo of simulation and space mission planning. In this paper, we employ the long-shortterm memory(LSTM) and neural network autoregression(NNAR) deep learning methods to predict the upcoming 25 th solar cycle using the sunspot area(SSA) data during the period of May 1874 to December2020. Our results show that the 25 th solar cycle will be 55% stronger than Solar Cycle 24 with a maximum sunspot area of 3115±401 and the cycle reaching its peak in October 2022 by using the LSTM method. It also shows that deep learning algorithms perform better than the other commonly used methods and have high application value.

Periodicities in Solar Activity, Solar Radiation and Their Links with Terrestrial Environment

Solar magnetic activity is expressed via variations of sunspots and active regions varying on different timescales. The most accepted is an 11-year period supposedly induced by the electromagnetic solar dynamo mechanism. There are also some shorter or longer timescales detected: the biennial cycle (2 - 2.7 years), Gleisberg cycle (80 - 100 years), and Hallstatt’s cycle (2100 - 2300 years). Recently, using Principal Component Analysis (PCA) of the observed solar background magnetic field (SBMF), another period of 330 - 380 years, or Grand Solar Cycle (GSC), was derived from the summary curve of two eigenvectors of SBMF. In this paper, a spectral analysis of the averaged sunspot numbers, solar irradiance, and the summary curve of eigenvectors of SBMF was carried out using Morlet wavelet and Fourier transforms. We detect a 10.7-year cycle from the sunspots and modulus summary curve of eigenvectors as well a 22-year-cycle and the grand solar cycle of 342 - 350-years from the summary curve of eigenvectors. The Gleissberg centennial cycle is only detected on the full set of averaged sunspot numbers for 400 years or by adding a quadruple component to the summary curve of eigenvectors. Another period of 2200 - 2300 years is detected in the Holocene data of solar irradiance measured from the abundance of 14C isotope. This period was also confirmed with the period of about 2000 - 2100 years derived from a baseline of the solar background magnetic field, supposedly, caused by the solar inertial motion (SIM) induced by the gravitation of large planets. The implication of these findings for different deposition of solar radiation into the northern and southern hemispheres of the Earth caused by the combined effects of the solar activity and solar inertial motion on the terrestrial atmosphere is also discussed.

Terrestrial Temperature, Sea Levels and Ice Area Links with Solar Activity and Solar Orbital Motion

This paper explores the links between terrestrial temperature, sea levels and ice areas in both hemispheres with solar activity indices expressed through averaged sunspot numbers together with the summary curve of eigenvectors of the solar background magnetic field (SBMF) and with changes of Sun-Earth distances caused by solar inertial motion resulting from the gravitation of large planets in the solar system. Using the wavelet analysis of the GLB and HadCRUTS datasets two periods: 21.4 and 36 years in GLB, set and the period of about 19.6 years in the HadCRUTS are discovered. The 21.4-year period is associated with variations in solar activity defined by the summary curve of the largest eigenvectors of the SBMF. A dominant 21.4-year period is also reported in the variations of the sea level, which is linked with the period of 21.4 years detected in the GLB temperature and the summary curve of the SBMF variations. The wavelet analysis of ice and snow areas shows that in the Southern hemisphere, it does not show any links to solar activity periods while in the Northern hemisphere, the ice area reveals a period of 10.7 years equal to a usual solar activity cycle. The TSI in March-August of every year is found to grow with every year following closely the temperature curve, because the Sun moves closer to the Earth orbit owing to gravitation of large planets (solar inertial motion, SIM), while the variations of solar radiation during a whole year have more steady distribution without a sharp TSI increase during the last two centuries. The additional TSI contribution caused by SIM is likely to secure the additional energy input and exchange between the ocean and atmosphere.

The Lyman-alpha Solar Telescope(LST) for the ASO-S mission——Ⅲ. data and potential diagnostics

The Lyman-alpha Solar Telescope(LST)is one of the three payloads onboard the Advanced Space-based Solar Observatory(ASO-S)mission.It aims at imaging the Sun from the disk center up to 2.5 R⊙targeting solar eruptions,particularly coronal mass ejections(CMEs),solar flares,prominences/filaments and related phenomena,as well as the fast and slow solar wind.The most prominent speciality of LST is the simultaneous observation of the solar atmosphere in both Lyαand white light(WL)with high temporospatial resolution both on the solar disk and the inner corona.New observations in the Lyαline together with traditional WL observations will provide us with many new insights into solar eruptions and solar wind.LST consists of a Solar Corona Imager(SCI)with a field of view(FOV)of 1.1–2.5 R⊙,a Solar Disk Imager(SDI)and a full-disk White-light Solar Telescope(WST)with an identical FOV up to 1.2 R⊙.SCI has a dual waveband in Lyα(121.6±10 nm)and in WL(700±40 nm),while SDI works in the Lyαwaveband of 121.6±7.5 nm and WST works in the violet narrow-band continuum of 360±2.0 nm.To produce high quality science data,careful ground and in-flight calibrations are required.We present our methods for different calibrations including dark field correction,flat field correction,radiometry,instrumental polarization and optical geometry.Based on the data calibration,definitions of the data levels and processing procedures for the defined levels from raw data are described.Plasma physical diagnostics offer key ingredients to understand ejecta and plasma flows in the inner corona,as well as different features on the solar disk including flares,filaments,etc.Therefore,we are making efforts to develop various tools to detect the different features observed by LST,and then to derive their physical parameters,for example,the electron density and temperature of CMEs,the outflow velocity of the solar wind,and the hydrogen density and mass flows of prominences.Coordinated observations and data analyses with the coronagraphs onboard Solar Orbiter,PROBA-3,and Aditya are also briefly discussed.

Solar cycle prediction using a long short-term memory deep learning model

In this paper,we propose a long short-term memory(LSTM)deep learning model to deal with the smoothed monthly sunspot number(SSN),aiming to address the problem whereby the prediction results of the existing sunspot prediction methods are not uniform and have large deviations.Our method optimizes the number of hidden nodes and batch sizes of the LSTM network structures to 19 and 20,respectively.The best length of time series and the value of the timesteps were then determined for the network training,and one-step and multi-step predictions for Cycle 22 to Cycle 24 were made using the well-established network.The results showed that the maximum root-mean-square error(RMSE)of the one-step prediction model was6.12 and the minimum was only 2.45.The maximum amplitude prediction error of the multi-step prediction was 17.2%and the minimum was only 3.0%.Finally,the next solar cycles(Cycle 25)peak amplitude was predicted to occur around 2023,with a peak value of about 114.3.The accuracy of this prediction method is better than that of the other commonly used methods,and the method has high applicability.

Repercussions of solar high energy protons on ozone layer during super storms

We are very aware of the importance of the ozone layer, without which life on the Earth would not have evolved in the way it has. Solar storms carry energetic protons into the Earth's upper atmosphere,where they boost production of nitrogen oxides which are known as ozone killers and which ultimately increase ultraviolet(UV) radiations. In the present study, we estimate the effects of solar energetic protons during super storms(Dst index <-300 nT) over the total ozone column for the last 32 yr. We select a total of seven super storm events that occurred during solar cycles 22–24(for the last 32 yr) having Dst index <-300 nT. To that end, we apply superposed epoch analysis(SEA) to verify the impact of storm events on the quantitative variation of total ozone column and on UV radiations during super storm events.After completing the empirical analysis, we conclude that the ozone column gets depleted significantly(22±6.8%) as proton density increases during super storm events and this decrement in the ozone level is further responsible for a substantial increase(26±11.2%) in peak UV radiation intensities.

Energy and spectral analysis of confined solar flares from radio and X-ray observations

The energy and spectral shape of radio bursts may help us understand the generation mechanism of solar eruptions,including solar flares,coronal mass ejections,eruptive filaments,and various scales of jets.The different kinds of flares may have different characteristics of energy and spectral distribution.In this work,we selected 10 mostly confined flare events during October 2014 to investigate their overall spectral behaviour and the energy emitted in microwaves by using radio observations from microwaves to interplanetary radio waves,and X-ray observations of GOES,RHESSI,and Fermi/GBM.We found that:all the confined flare events were associated with a microwave continuum burst extending to frequencies of9.4~15.4 GHz,and the peak frequencies of all confined flare events are higher than 4.995 GHz and lower than or equal to 17 GHz.The median value is around 9 GHz.The microwave burst energy(or nuence)and the peak frequency are found to provide useful criteria to estimate the power of solar flares.The observations imply that the magnetic field in confined flares tends to be stronger than that in 412 flares studied by Nita et al.(2004).All 10 events studied did not produce detectable hard X-rays with energies above~300 keV indicating the lack of efficient acceleration of electrons to high energies in the confined flares.

太阳风离子尺度湍流与太阳风加热

太阳风源自太阳大气,在行星际空间传播过程中被持续加热,然而究竟是何种能量加热了太阳风至今未研究清楚.太阳风普遍处于湍动状态,其湍动能量被认为是加热太阳风的重要能源.然而,太阳风湍流通过何种载体、基于何种微观物理机制加热了太阳风尚不明确,这是相关研究的关键问题.将回顾人类对太阳风加热问题的研究历史,着重介绍近年来我国学者在太阳风离子尺度湍流与加热方面取得的研究进展,展望未来在太阳风加热研究中有待解决的科学问题和可能的研究方向.

太阳风中电磁离子回旋波的观测与理论研究进展

太阳风中的电磁离子回旋(Electromagnetic Ion Cyclotron,EMIC)波自报道以来,受到了广泛的关注和研究.由于波的频率接近质子的回旋频率,EMIC波可以通过回旋共振波粒相互作用将波能传递给离子,并在太阳风粒子加热和加速等能化现象中发挥重要作用.总结了太阳风中EMIC波的观测和理论研究进展,包括EMIC波在磁云内外、磁云和行星际日冕物质抛射鞘区中的观测研究得到的一系列结果以及基于观测进行波的激发机制所取得的研究进展,并展望未来研究太阳风中EMIC波的突破方向.

微波Ⅲ型爆发的统计分析

本文统计分析了国家天文台5.2～7.6GHz频段高时间分辨率频谱仪23周太阳活动峰年期间(1999.8～2002.1)观测到的87个Ⅲ型爆发,对这些事件的频率漂移、半功率持续时间、带宽和偏振及相关事件作了详细分析。认为这些Ⅲ型爆发可能是由非热电子束引起的谐波等离子体辐射和电子回旋脉泽辐射而产生。

第二太阳光谱

在太阳大气中，共振散射可引起辐射的线偏振．用偏振度测量精度达10－5的仪器，已经探测出完整的偏振辐射谱，这称为第二太阳光谱．它具有大量的、与通常太阳光谱截然不同的特征和结构．已有的研究发现它们与量子力学干涉、同位素效应、分子散射等物理过程有关．利用第二太阳光谱，可以进一步开展太阳物理的多项研究．

The meridional circulation of the Sun: Observations, theory and connections with the solar dynamo

The meridional circulation of the Sun, which is observed to be poleward at the surface, should have a return flow at some depth. Since large-scale flows like the differential rotation and the meridional circulation are driven by turbulent stresses in the convection zone, these flows are expected to remain confined within this zone. Current observational(based on helioseismology)and theoretical(based on dynamo theory) evidences point towards an equatorward return flow of the meridional circulation at the bottom of the convection zone. Assuming the mean values of various quantities averaged over turbulence to be axisymmetric,we study the large-scale flows in solar-like stars on the basis of a 2D mean field theory. Turbulent stresses in a rotating star can transport angular momentum, setting up a differential rotation. The meridional circulation arises from a slight imbalance between two terms which try to drive it in opposite directions: a thermal wind term(arising out of the higher efficiency of convective heat transport in the polar regions) and a centrifugal term(arising out of the differential rotation). To make these terms comparable,the poles of the Sun should be slightly hotter than the equator. We discuss the important role played by the meridional circulation in the flux transport dynamo model. The poloidal field generated by the Babcock-Leighton process at the surface is advected poleward, whereas the toroidal field produced at the bottom of the convection zone is advected equatorward. The fluctuations in the meridional circulation(with coherence time of about 30-40 yr) help in explaining many aspects of the irregularities in the solar cycle. Finally, we discuss how the Lorentz force of the dynamo-generated magnetic field can cause periodic variations in the large-scale flows with the solar cycle.

ERRATUM: “Determination of the chromospheric quiet network element area index and its variation between 2008 and 2011” (RAA, Vol. 12, p.201 [2012])

As a result of the authors＇ error, the paper ＂Determination of the chromospheric quiet network element area index and its variation between 2008 and 2011＂ by Singh, J. et al. （RAA, Vol. 12, p.201 [2012]） contains errors in page 206. In the original article, the top right and bottom images were inadvertently interchanged in Figure 5. The correct sequence of images is shown in this erratum. Figure caption and details about the images remain unchanged.

Charge transfer and excitation processes in low energy collisions of He ions with Li atoms

Electron capture between solar wind ions and neutral species has contributed to the understanding of X-ray production from solar system bodies.The charge transfer and excitation processes in solar wind ions of He^(+)(1 s) colliding with Li(1 s^(2)2 s) atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling(QMOCC) method with impact energies of 0.003-2 keV amu-1.Comparisons of cross sections from single-and multi-configurational calculations for a selfconsistent field(SCF and MCSCF) process are carried out.Results show that the dominant reaction channels are He(1 s2 l ^(1,3) L)+Li^(+)(1 s^(2) ^(1) S).Good consistency is found among present total and state-selective charge transfer and excitation cross sections with other theoretical and experimental data in the same energy region.Due to the differences between coupling matrix elements in high-energy states,the charge transfer cross sections calculated from SCF and MCSCF split slightly as E> 0.4 keV amu-1.Weak Stueckelberg oscillations for charge transfer appear in the present work.In addition,the differences of cross sections for electron excitation to Li(ls^(2)2 p) in the singlet/triplet molecular states with He+(1 s) are much smaller than those of charge transfer processes because of the similar energy gaps from Li(ls^(2)2 p) to the ground state in singlet/triplet states in the large R region.

Plasma Heating Induced by Tadpole-like Downflows in the Flaring Solar Corona

As one of the most spectacular energy release events in the solar system,solar flares are generally powered by magnetic reconnection in the solar corona.As a result of the re-arrangement of magnetic field topology after the reconnection process,a series of new looplike magnetic structures are often formed and are known as flare loops.A hot diffuse region,consisting of around 5–10 MK plasma,is also observed above the loops and is called a supra-arcade fan.Often,dark,tadpole-like structures are seen to descend through the bright supra-arcade fans.It remains unclear what role these so-called supra-arcade downflows(SADs)play in heating the flaring coronal plasma.Here we show a unique flare observation,where many SADs collide with the flare loops and strongly heat the loops to a temperature of 10–20 MK.Several of these interactions generate clear signatures of quasi-periodic enhancement in the full-Sun-integrated soft X-ray emission,providing an alternative interpretation for quasi-periodic pulsations that are commonly observed during solar and stellar flares.