Study of Multiple Coronal Mass Ejections at Solar Minimum Conditions

Solar activity alternates between active and quiet phases with an average period of 11?years, and this is known as the Schwabe cycle. Additionally, solar activity occasionally falls into a prolonged quiet phase (grand solar minimum), as represented by the Maunder Minimum in the 17th century, when sunspots were almost absent for 70?years and the length of the Schwabe cycle increased to 14?years. To examine the consistency of the cycle length characteristics during the grand solar minima, the carbon-14 contents in single-year tree rings were measured using an accelerator mass spectrometer as an index of the solar variability during the grand solar minimum of the 4th century BC. The signal of the Schwabe cycle was detected with a statistical confidence level of higher than 95?% by wavelet analysis. This is the oldest evidence for the Schwabe cycle at the present time, and the cycle length is considered to have increased to approximately 16?years during the grand solar minimum of the 4th century BC. This result confirms the association between the increase of the Schwabe cycle length and the weakening of solar activity, and indicates the possible prolonged absence of sunspots in the 4th century BC as during the Maunder Minimum. Theoretical implications from solar dynamo theory are discussed in order to identify the trigger of prolonged sunspot absence. A possible association between the long-term solar variation around the 4th century BC and terrestrial cooling in this period is also discussed.     

Temporal offsets among solar activity indicators

Temporal offsets between the time series of solar activity indicators provide important clues regarding the physical processes responsible for the cyclic variability in the solar atmosphere. Hysteresis patterns generated between any two indicators were popularly used to study their morphological features and further to understand their inter relationships. We use time series of different solar indicators to understand the possible cause-and-effect criteria between their respective source regions. Sensitivity of the upper atmosphere to the activity underneath might play an important role in introducing different evolutionary patterns in the profiles of solar indicators and in turn cause temporal offsets between them. Limitations in the observations may also cause relative shifts in the time series.     

太阳与地磁活动的1.3–1.7 yr振荡关系分析

太阳和地磁活动中的1.3–1.7 yr周期研究对于理解日地空间耦合系统中可能发生的物理过程十分重要.黑子是太阳光球层上最突出的磁场结构, Ap指数则是表征全球地磁活动水平的重要指标.使用同步压缩小波变换得到太阳黑子数和地磁Ap指数的1.3–1.7yr周期,并用互相关方法分析研究它们之间的相位关系.结果如下:(1)太阳黑子数和地磁Ap指数的1.3–1.7 yr周期呈现间歇性的演化特征,且随着时间的变化而不断变化;(2)地磁Ap指数在奇数活动周比相邻的偶数活动周的周期分量更高,表现出上下波动的变化特性;(3)地磁Ap指数和太阳黑子数的相位关系不是一成不变的,在大多数情况下地磁Ap指数滞后太阳黑子数,仅在第18和第22活动周黑子数在相位上滞后.     

Analysis of the 1.3–1.7 yr Oscillation Relationship between Solar and Geomagnetic Activities

The study on the 1.3–1.7 yr period of the solar and geomagnetic activities is very important for understanding the possible physical processes in the solar-terrestrial coupling system. The sunspot is the most prominent magnetic field structure in the solar photosphere, and the Ap index is an important indicator for the global geomagnetic activity level. The 1.3–1.7 yr period for the sunspot number and the geomagnetic Ap index is obtained by the synchro-squeezing wavelet transform, and the phase relationship between them is studied by the cross-correlation analysis. The main results are as follows: (1) The 1.3–1.7 yr period of the geomagnetic Ap index and sunspot number exhibits an intermittent evolutionary characteristics, and changes continuously with the time; (2) the geomagnetic Ap index has a higher periodic component in the odd solar cycles than the neighboring even solar cycles, which is characterized by fluctuations; (3) the phase relationship between the geomagnetic Ap index and the sunspot number is not always invariant, in most cases the geomagnetic Ap index lags behind the sunspot number, except in the 18th and 22th solar cycles.     

Influence of solar activity on the state of the wheat market in medieval England

The database of professor Rogers (1887), which includes wheat prices in England in the Middle Ages, was used to search for a possible influence of solar activity on the wheat market. Our approach was based on the following: (1) Existence of the correlation between cosmic ray flux entering the terrestrial atmosphere and cloudiness of the atmosphere. (2) Cosmic ray intensity in the solar system changes with solar activity, (3) Wheat production depends on weather conditions as a nonlinear function with threshold transitions. (4) A wheat market with a limited supply (as it was in medieval England) has a highly nonlinear sensitivity to variations in wheat production with boundary states, where small changes in wheat supply could lead to bursts of prices or to prices falling. We present a conceptual model of possible modes for sensitivity of wheat prices to weather conditions, caused by solar cycle variations, and compare expected price fluctuations with price variations recorded in medieval England. We compared statistical properties of the intervals between wheat price bursts during the years 1249-1703 with statistical properties of the intervals between the minima of solar cycles during the years 1700-2000. We show that statistical properties of these two samples are similar, both for characteristics of the distributions and for histograms of the distributions. We analyze a direct link between wheat prices and solar activity in the 17^th century, for which wheat prices and solar activity data (derived from ¹⁰Be isotope) are available. We show that for all 10 time moments of the solar activity minima the observed prices were higher than prices for the corresponding time moments of maximal solar activity (100% sign correlation, on a significance level < 0.2%). We consider these results a direct evidence of the causal connection between wheat prices bursts and solar activity.     

Influence of solar activity on the state of the wheat market in medieval England

The database of professor Rogers (1887), which includes wheat prices in England in the Middle Ages, was used to search for a possible influence of solar activity on the wheat market. Our approach was based on the following: (1) Existence of the correlation between cosmic ray flux entering the terrestrial atmosphere and cloudiness of the atmosphere. (2) Cosmic ray intensity in the solar system changes with solar activity, (3) Wheat production depends on weather conditions as a nonlinear function with threshold transitions. (4) A wheat market with a limited supply (as it was in medieval England) has a highly nonlinear sensitivity to variations in wheat production with boundary states, where small changes in wheat supply could lead to bursts of prices or to prices falling. We present a conceptual model of possible modes for sensitivity of wheat prices to weather conditions, caused by solar cycle variations, and compare expected price fluctuations with price variations recorded in medieval England. We compared statistical properties of the intervals between wheat price bursts during the years 1249-1703 with statistical properties of the intervals between the minima of solar cycles during the years 1700-2000. We show that statistical properties of these two samples are similar, both for characteristics of the distributions and for histograms of the distributions. We analyze a direct link between wheat prices and solar activity in the 17^th century, for which wheat prices and solar activity data (derived from ¹⁰Be isotope) are available. We show that for all 10 time moments of the solar activity minima the observed prices were higher than prices for the corresponding time moments of maximal solar activity (100% sign correlation, on a significance level < 0.2%). We consider these results a direct evidence of the causal connection between wheat prices bursts and solar activity.     

Possible Influence of the 11-year Solar Cycle on Precipitation in Huashan Mountain of China over the Last 300 Years

Taking into account reconstructed precipitation time series in Huashan mountain area of China on the one hand and sunspot numbers observations on the other hand, the authors used here continuous wavelet transform and cross wavelet transform to investigate possible connection between the two sets of indicators. The analysis was performed over the last 300 years: it is found that solar activity influences precipitation in that geographical area of China to some extent, with an excess of 5% statistical significance level red noise over the 11-year solar activity cycle.     

Balloon observations of solar ultraviolet irradiance at solar minimum

Balloon observations of solar irradiance between 200 and 240 nm have been performed in 1976 and 1977 corresponding to minimum conditions of solar activity. Ultraviolet spectra have been recorded for different zenith angles at an altitude of 41 km by means of a spectrometer with a spectral bandpass of 0.4 nm. Solar irradiances at 1 a.u. confirm previous values obtained by balloon. They are compared with other measurements and discussed in term of possible long-term variability.     

Circulation changes in the free atmosphere during proton events associated with type IV radio bursts

New evidence of statistically significant circulation changes in the lower stratosphere and in the middle and upper troposphere following Type IV Proton and Ground Level Events confirms some earlier findings of a relationship between solar activity and weather. The maximum 24-hr circulation changes appear to occur in the North Pacific-Alaskan area. A comparison between the effects that followed the flare sample used in this study with earlier results reported for less intense solar particle emission flare samples, implies that if these particles are responsible for triggering the atmospheric circulation in times of enhanced solar activity, their atmospheric effect is enhanced as we move to the more energetic solar proton events. The physical explanation of the results may possibly be found in numerical-experimental models. Some possible causes of the results are discussed.     

Dependence of the Sunspot-Group Size on the Level of Solar Activity and its Influence on the Calibration of Solar Observers

We study the distribution of the sunspot-group size (area) and its dependence on the level of solar activity. We show that the fraction of small groups is not constant but decreases with the level of solar activity so that high solar activity is mainly defined by large groups. We analyze the possible influence of solar activity on the ability of a realistic observer to see and report the daily number of sunspot groups. It is shown that the relation between the number of sunspot groups as seen by different observers with different observational acuity thresholds is strongly nonlinear and cannot be approximated by the traditionally used linear scaling (\(k\)-factors). The observational acuity threshold [\(A_{\mathrm{th}}\)] is considered to quantify the quality of each observer, instead of the traditional relative \(k\)-factor. A nonlinear \(c\)-factor based on \(A_{\mathrm{th}}\) is proposed, which can be used to correct each observer to the reference conditions. The method is tested on a pair of principal solar observers, Wolf and Wolfer, and it is shown that the traditional linear correction, with the constant \(k\)-factor of 1.66 to scale Wolf to Wolfer, leads to an overestimate of solar activity around solar maxima.     

The sodium tail of the Moon

During the few days centered about new Moon, the lunar surface is optically hidden from Earth-based observers. However, the Moon still offers an observable: an extended sodium tail. The lunar sodium tail is the escaping “hot” component of a coma-like exosphere of sodium generated by photon-stimulated desorption, solar wind sputtering and meteoroid impact. Neutral sodium atoms escaping lunar gravity experience solar radiation pressure that drives them into the anti-solar direction forming a comet-like tail. During new Moon time, the geometry of the Sun, Moon and Earth is such that the anti-sunward sodium flux is perturbed by the terrestrial gravitational field resulting in its focusing into a dense core that extends beyond the Earth. An all-sky camera situated at the El Leoncito Observatory (CASLEO) in Argentina has been successfully imaging this tail through a sodium filter at each lunation since April 2006. This paper reports on the results of the brightness of the lunar sodium tail spanning 31 lunations between April 2006 and September 2008. Brightness variability trends are compared with both sporadic and shower meteor activity, solar wind proton energy flux and solar near ultra violet (NUV) patterns for possible correlations. Results suggest minimal variability in the brightness of the observed lunar sodium tail, generally uncorrelated with any single source, yet consistent with a multi-year period of minimal solar activity and non-intense meteoric fluxes.     

Decametre-wave radiation from jupiter and solar activity

The problem of a possible short term correlation between Jupiter's decametre-wave radio emission and solar activity is re-examined and the complicating factors are discussed. Developing the approach of Sastry, Jupiter events are used as epochs and the Chree analysis method is applied to data taken from 1961 to 1968. The data are separated into two parts, before and after each opposition, and this is shown to provide an additional test for correlation. The results are found to be consistent with the idea that at least some of the Jupiter radiation may be stimulated by solar particles having radial velocities in the range 350–700 km/sec. travelling outward as far as the orbit of Jupiter.     

The delay between solar activity and density changes in the upper atmosphere

Since 1958 it is known that there exists a response time of the upper atmosphere to changes in solar activity. This response time is best described as the lag between the 27-day variation of solar decimeter flux and the observed density changes of the upper atmosphere. Roemer obtained as a mean observational value for this lag 1.0 ± 0.12 days. Volland's simplified version of the Harris-Priester model of the upper atmosphere is used to calculate the delay which can be expected from theory. Only the effect of solar EUV radiation is taken into account. A possible influence of the corpuscular component of the solar radiation is not included in our estimate.

The calculations are carried out for the Harris-Priester model with solar activity index and a variation of . The resulting delay is 0.6 days. The calculated amplitude of the variations of the diurnal average temperatures during the solar 27-days cycle is in very good agreement with Jacchia's empirical formula.     

Recent Progress of Hemispheric Coupling of Solar Activity Cycle

The hemispheric coupling phenomenon of solar activity cycle was discovered as early as the mid-20th century, and it is one of the most common topic in the long-term spatio-temporal evolution of the Sun, while the observational features and physical mechanism of hemispheric coupling have not been completely understood. The theoretical model of solar magnetohydrodynamics driven by this phenomenon is helpful in studying the basic information of the spatio-temporal evolution of solar activity cycle, and is also of great value to the short- and medium-term forecast of solar activity as well as the space weather. Here, we first give the discovery and observational history of the hemispheric coupling of solar activity. And then, the basic observational features of hemispheric coupling at different spatio-temporal scales and their possible mechanism are summarized. Finally, we give a discussion about the important unresolved issues and development trends in this important field.     

Solar flares and the cosmic ray intensity

The relationship between the cosmic ray intensity and solar activity during solar cycle 20 is discussed. A model is developed whereby it is possible to simulate the observed cosmic ray intensity from the observed number of solar flares of importance 1. This model leads to a radius for the modulation region of 60–70 AU. It is suggested that high speed solar streams also made a small contribution to the modulation of cosmic rays during solar cycle 20.     

The response of ozone to solar activity variations: A review

Observational evidence and theoretical predictions of the response of ozone to solar variations are reviewed. Short-term solar proton effects, possible effects of galactic cosmic rays modulated by the Sun, and the effects of 27-day solar rotation and 11-year solar cycle variations are discussed. Solar proton effects on HO _x chemistry in the mesosphere and NO _x chemistry in the stratosphere with resulting catalytic destruction of O₃ help validate present day photochemical models. If there is an 11-year solar cycle variation in global ozone, the large dynamical effects at individual locations and the lack of good global coverage of ground based and in situ measurements can disguise it. Recently, with the global coverage of satellites, it has become possible to accurately determine global mean ozone. It has been found that variations in global mean ozone filtered for seasonal variations are highly correlated with variations of the 10.7 cm solar activity index and that global mean ozone responds rapidly to solar activity index variations. Photochemical models indicate that the observed 3% variations in global mean ozone over the solar cycle can be accounted for by solar UV variations which are not inconsistent with recent solar measurements.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

On the possibility of deducing interplanetary and solar parameters from geomagnetic records

While at present we are able to deduce from ground records only qualitative properties of the solar wind, in the future quantitative deductions may be possible, in a statistical sense, from an examination of polar cap magnetograms together with records of geomagnetic activity. The qualitative inferences that are possible now indicate several important features of the behavior of the solar wind over the last 100 years. First, there appear to be significant long term changes in either the solar wind velocity, the magnetic field strength, the variability of the field or some combination of all three. Second, a heliographic latitude dependence of these parameters exists, whose amplitude depends on sunspot number. Third, with the exception of the most recent solar cycle, there is little north-south asymmetry in these solar parameters. Finally, there is a double sunspot cycle modulation of geomagnetic activity, the most likely cause of which is a modulation of the interplanetary magnetic polarity with latitude, and which in turn implies the presence of a solar polar magnetic dipole. The amplitude of this modulation has undergone significant changes since 1868, being large then and at the present, but effectively disappearing from 1908 to 1948.     

On the homestake neutrino data

³⁷ Ar production rates from the Homestake experiment suggest a possible anticorrelation between solar neutrino flux and solar activity. In this paper we present results from linear correlation analyses between Homestake data and several solar activity parameters in the period 1970–1990. Our results support the hypothesis that Homestake neutrino fluxes exhibit a (positive or negative) correlation with those parameters, but they also suggest that the heliomagnetic field in the subphotosphere could be responsible for the observed flux modulation.     

地球自转变化中的太阳物理效应

对太阳活动和太阳风影响地球自转的研究现状作了评述。首先了地球自转变化的表示和测定方法，引起地球自转变化的各种扰动源以及自转长期变化中的潮汐效应和非潮汐效应。然后对地球自转变化中的太阳活动周期调制，太阳耀斑可能引起地球自转突然减速以及太阳风能否影响地球自转等问题的国内外研究现状和结果、分析作了谰论性阐述，最后作了简要总结。     

高能粒子流对地震活动的可能调制

把地球作为一个开放系统，本文分析了不同地域范围的地震活动和太阳活动的关系，发现不同地域的地震活动也存在着一个大约１１年的周期，这个周期可能与太阳活动的１１年左右周期有关，但地震周期的峰值对应于太阳活动的下降段。它们的关系是负相关关系。本文进一步着重分析了地震活动与高速太阳风粒子流和宇宙线高能粒子流的关系，发现它们之间存在着一个信度水平很高的正相关。这样，我们可以推测太阳活动可能是通过调制到达地球的高能粒子流进而调制地震活动的。