Evidence for a Strong Correlation of Solar Proton Events with Solar Radio Bursts

A statistical analysis is made on the correlation between solar proton events with energies >10Mev and solar radio bursts during the four-year period from 1997 November to 2000 November. We examine 28 solar proton events and their corresponding solar radio bursts at 15400, 8800, 4995, 2695, 1415, 606, 410 and 245 MHz. The statistical result shows that there is a close association between solar proton events and ≥3 solar radio bursts occurring at several frequencies, one or two days before. In particular, it is noteworthy that proton events occurring     

Observation of Small-amplitude Electromagnetic Cyclotron Waves in the Solar Wind

Our previous studies on low-frequency electromagnetic cyclotron waves(ECWs) with amplitudes larger than 0.1nT in the solar wind revealed that the left-handed(LH) polarized ECWs are the dominant waves,and these waves preferentially occur in plasma conditions of high proton speed(V_p),high proton temperature(T_p),low proton density(N_p).In the present study,using magnetic field and plasma data from the Wind mission between 2005 and2015,we perform a survey of small-amp...     

A Correlation between Proton Events and Hα Flares and its Possible Interpretation

1 INTRoDUCTIONIt is well known that solar proton flares are maiuly correlated with strong, bright H. flares,in particular, with two ribbon flares. Ellison et al. (l961) were the first to draw attelltion tothe faCt that all cosndc-ray flares had the typical two-ribbon shape. Then, Svestka and Simon(1976) drew uP the "Catalog of Solar Particle Evellts, 195ty1969", and using this Catalog,Dodson and Hedeman could safely identify the flare sources for 50 proton events. Out of the 50idellti…     

THE 152-DAY PERIODICITY OF THE OCCURRENCE RATE OF SOLAR MICROWAVE BURSTS

It has been found for a long time, with analysing the variation of the relative number of sunspot, that there exist the periodicity of 11 years in solar activity. With the deepening research of the varied solar active phenomena, a series of periodicities with different periods have been also found in solar activity. For example, there is the periodicity of about 80 days for the occurrence, rate of proton flares for solar activity cycles 19 and 20 found by Ai and Fan ci:i at 1974. Recently a periodicity of about 152 days of the occurrence rate of solar flares has been proposed by some authors. a3'5>7:i The existence of this periodicity hsa been proved in the various solar flares. In this paper using the data of solar microwave bursts from January 1986 to December 1988, a Fourier analysis of the occurrence rate of solar microwave bursts has been made. There was no periodicity for the occurrence rate of solar microwave bursts of about 152 days found. This is a new result for solar cycle 22 in the first thr     

Long term variations in solar flare activity

A statistical analysis of the contemporary (1954-1975) solar flare particle events has been made for the parametersF (integrated, proton fluence in cm^-2 in an event with kinetic energy above 10 MeV) andR ₀ (the characteristic rigidity). These data are compared with the long-term averaged values determined from stable- and radio-nuclide measurements of lunar samples. The analysis shows that the ancient solar flare proton spectrum was harder (higher R₀ values) compared to that observed in contemporary flares. A similar analysis can not be made for the mean long-term averaged flux (ˉJ, cm^-2 S^-1), since the contemporary averages suffer from an uncertainty due to the statistics of a single event. However, the average flux estimates for time durations 〈T〉 exceeding 10³ yr, are free from such uncertainties. The long-term averaged ˉJ values obtained over different time scales (10⁴ - 10⁶ yr) suggest a possible periodic variation in solar flare activity, with enhanced flux level during the last 10⁵ yr. The available data rule out the occurrence of giant flares, with proton fluence exceeding 10¹⁵ cm^-2 during the last million years.     

Geoeffectiveness of the coronal mass ejections associated with solar proton events

The intensity-time profiles of solar proton events(SPEs) are grouped into three types in the present study. The Type-I means that the intensity-time profile of an SPE has one peak, which occurs shortly after the associated solar flare and coronal mass ejection(CME). The Type-II means that the SPE profile has two peaks: the first peak occurs shortly after the solar eruption, the second peak occurs at the time when the CME-driven shock reaches the Earth, and the intensity of the second peak is lower than the first one.If the intensity of the second peak is higher than the first one, or the SPE intensity increases continuously until the CME-driven shock reaches the Earth, this kind of intensity-time profile is defined as Type-III. It is found that most CMEs associated with Type-I SPEs have no geoeffectiveness and only a small part of CMEs associated with Type-I SPEs can produce minor(–50 n T ≤ Dst ≤–30 n T) or moderate geomagnetic storms(–100 n T≤ Dst ≤–50 n T), but never an intense geomagnetic storm(–200 n T ≤ Dst -100 n T). However,most of the CMEs associated with Type-II and Type-III SPEs can produce intense or great geomagnetic storms(Dst ≤-200 n T). The solar wind structures responsible for the geomagnetic storms associated with SPEs with different intensity-time profiles have also been investigated and discussed.     

FIARE ACTIVITY AND EVOLUTION WITHIN AR5629

The middle ten days of August,1989 was one of the peak times of solar activity.During the period the solar indices such as 10cm radio flux,relative sunspot number,spot area,X—ray flux,proton fluence and electron fluence had a evidently rising.Espec-ially,the X—ray background flux went so far as to C7.9 on Aug.16.The main reason for     

Dependence of E ≥ 100 MeV protons on the associated flares and CMEs

To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray(SXR) emission, and coronal mass ejection(CME) linear speed in the three longitudinal areas W0–W39, W40–W70 and W71–W90 have been calculated respectively. Classical correlation analysis shows that the correlation coefficients between CME speeds and I100 in the three longitudinal areas are0.28±0.21, 0.35±0.21 and 0.04±0.30 respectively. The classical correlation coefficients between I100 and SXR peak flux in the three longitudinal areas are 0.48±0.17, 0.72±0.13 and 0.02±0.30 respectively, while the correlation coefficients between I100 and SXR fluence in the three longitudinal areas are 0.25±0.21, 0.84±0.07 and 0.10±0.30 respectively. Partial correlation analysis shows that for solar proton events with source location in the well connected region(W40–W70), only SXR fluence can significantly affect the peak intensity of E ≥ 100 MeV protons, but SXR peak flux has little influence on the peak intensities of E ≥ 100 MeV protons; moreover, CME speed has no influence on the peak intensities of E ≥ 100 MeV protons. We conclude that these findings provide statistical evidence that E ≥ 100 MeV protons may be mainly accelerated by concurrent flares.     

The north-south asymmetry of solar filaments separately at low and high latitudes in solar cycle 23

We present the results of a study on the north-south asymmetry of solar filaments at low(50°) and high(60°) latitudes using daily filament numbers from January 1998 to November 2008(solar cycle 23). It is found that the northern hemisphere is dominant at low latitudes for cycle 23. However, a similar asymmetry does not occur for solar filaments at high latitudes. The present study indicates that the hemispheric asymmetry of solar filaments at high latitudes in a cycle appears to have little connection with that at low latitudes. Our results support that the observed magnetic fields at high latitudes include two components: one comes from the emergence of the magnetic fields from the solar interior and the other comes from the drift of the magnetic activity at low latitudes.     

EFFECTS OF SOLAR UV RADIATION ON THE MINOR CONSTITUENTS IN THE MIDDLE ATMOSPHERE(Abstract)

Although solar UV radiation contains only about 1％ of the total irradiance,it hasa large variation with solar activity.The measurements in the 21th solar cycle show thatthe variation in 200um region is about 6％ during a solar flare and it can reach 40％ inLyman line,even it can increase by 150％ over 11-year solar cycle.Due to the fact that     

A study of short-period variation in solar activity

We introduce two methods to detect short-period variation in solar activity.These are called amplitude of low frequency fluctuation(ALFF) and fractional amplitude of low frequency fluctuation(FALFF). We find a positive correlation between short-period variation and 11-year variation of solar activity using these two methods.Through ALFF,we find that solar activity over a short period becomes intensive when the 11-year solar activity is intensive. The ALFF value of the short period activity varies with the peak in sunspot number as a quadratic function. Through FALFF we find that the ratio of short-period spectral intensity to intensity over the whole period of solar activity will increase when the 11-year period of solar activity is intensive.The short-period FALFF value varies with the peak in sunspot number according to a cubic function. Using ALFF,we obtain a yearly series of solar activity that varies over a short period of 1–5 yr from 1860 to 2003,which shows an obvious periodicity of about 22 yr,33 yr,11 yr and a century. These short period variations show good correlations with long term variations in solar activity.     

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.     

The Effect of Solar Activity on the Annual Precipitation in the Beijing Area

Using continuous wavelet transform, we examine the relationship between solar activity and the annual precipitation in the Beijing area. The results indicate that the annual precipitation is closely related to the variation of sunspot numbers, and that solar activity probably plays an important role in influencing the precipitation on land.     

A brief report on the statistical study of net electric current in solar active regions with longitudinal fields of opposite polarity

Dynamic processes occurring in solar active regions are dominated by the solar magnetic field. As of now, observations using a solar magnetograph have supplied us with the vector components of a solar photospheric magnetic field. The two transverse components of a photospheric magnetic field allow us to compute the amount of electric current. We found that the electric current in areas with positive (negative) polarity due to the longitudinal magnetic field have both positive and negative signs in an active region, however, the net current is found to be an order-of-magnitude less than the mean absolute magnitude and has a preferred sign. In particular, we have statistically found that there is a systematic net electric current from areas with negative (positive) polarity to areas with positive (negative) polarity in solar active regions in the northern (southern) hemisphere, but during the solar minimum this tendency is reversed over time at some latitudes. The result indicates that there is weak net electric current in areas of solar active regions with opposite polarity, thus providing further details about the hemispheric helicity rule found in a series of previous studies.     

Can Asymmetry of Solar Activity be Extended into Extended Cycle？

With the use of the Royal Greenwich Observatory data set of sunspot groups,an attempt is made to examine the north-south asymmetry of solar activity in the “extended” solar cycles. It is inferred that the asymmetry established for individual solar cycles does not extend to the “extended” cycles.     

Solar Energetic Particle Event of 2005 January 20： Release Times and Possible Sources

Based on cosmic ray data obtained by neutron monitors at the Earth's surface, and data on near-relativistic electrons measured by the WIND satellite, as well as on solar X-ray and radio burst data, the solar energetic particle (SEP) event of 2005 January 20 is studied. The results show that this event is a mixed event where the flare is dominant in the acceleration of the SEPs, the interplanetary shock accelerates mainly solar protons with energies below 130 MeV, while the relativistic protons are only accelerated by the solar flare. The interplanetary shock had an obvious acceleration effect on relativistic electrons with energies greater than 2 MeV. It was found that the solar release time for the relativistic protons was about 06:41 UT, while that for the near-relativistic electrons was about 06:39 UT. The latter turned out to be about 2 min later than the onset time of the interplanetary type III burst.     

Solar flare forecasting based on sequential sunspot data

It is widely believed that the evolution of solar active regions leads to solar flares. However, information about the evolution of solar active regions is not employed in most existing solar flare forecasting models. In the current work, a shortterm solar flare forecasting model is proposed, in which sequential sunspot data, including three days of information about evolution from active regions, are taken as one of the basic predictors. The sunspot area, the McIntosh classification, the magnetic classification and the radio flux are extracted and converted to a numerical format that is suitable for the current forecasting model. Based on these parameters, the sliding-window method is used to form the sequential data by adding three days of information about evolution. Then, multi-layer perceptron and learning vector quantization are employed to predict the flare level within 48 h. Experimental results indicate that the performance of the proposed flare forecasting model works better than previous models.     

A New Method to Determine Epochs of Solar Cycle Extrema

A weighted average method is proposed to determine the epochs of solar cycle extrema and hence the solar cycle lengths. Comparing to the previous methods, this method has the advantage that the extremum epochs are easily and uniquely determined.     

A logistic model for magnetic energy storage in solar active regions

Previous statistical analyses of a large number of SOHO/MDI full disk longitudinal magnetograms provided a result that demonstrated how responses of solar flares to photospheric magnetic properties can be fitted with sigmoid functions. A logistic model reveals that these fitted sigmoid functions might be related to the free energy storage process in solar active regions. Although this suggested model is rather simple, the free energy level of active regions can be estimated and the probability of a solar flare with importance over a threshold can be forecast within a given time window.     

COMPUTER PROCESSING AND IMAGE PROCESSING OF H_α SOLAR FLARES

In the paper, authors introduct computer processing of Ha solar flares data in Urumqi Astronomical Station; Authors use the Series 151 Image Processing System to processing the nagatives of Ha solar flares, change them to pseudo-color pictures. It can make the shape and position of flares clear on the sun disk. Authors think that is benefit to improve the data of Ha solar flares.