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1.
Donald C. Norquist 《Solar physics》2011,269(1):111-127
Designing a statistical solar flare forecasting technique can benefit greatly from knowledge of the flare frequency of occurrence
with respect to sunspot groups. This study analyzed sunspot groups and Hα and X-ray flares reported for the period 1997 – 2007.
Annual catalogs were constructed, listing the days that numbered sunspot groups were observed (designated sunspot group-days,
SSG-Ds) and for each day a record for each associated Hα flare of importance category one or greater and normal or bright
brightness and for each X-ray flare of intensity C 5 or higher. The catalogs were then analyzed to produce frequency distributions
of SSG-Ds by year, sunspot group class, likelihood of producing at least one flare overall and by sunspot group class, and
frequency of occurrence of numbers of flares per day and flare intensity category. Only 3% of SSG-Ds produced a substantial
Hα flare and 7% had a significant X-ray flare. We found that mature, complex sunspot groups were more likely than simple sunspot
groups to produce a flare, but the latter were more prevalent than the former. More than half of the SSG-Ds with flares had
a maximum intensity flare greater than the lowest category (C-class of intensity five and higher). The fact that certain sunspot
group classes had flaring probabilities significantly higher than the combined probabilities of the intensity categories when
all SSG-Ds were considered suggest that it might be best to first predict the flaring probability. For sunspot groups found
likely to flare, a separate diagnosis of maximum flare intensity category appears feasible. 相似文献
2.
In order to investigate the relationship between magnetic-flux emergence, solar flares, and coronal mass ejections (CMEs), we study the periodicity in the time series of these quantities. It has been known that solar flares, sunspot area, and photospheric magnetic flux have a dominant periodicity of about 155 days, which is confined to a part of the phase of the solar cycle. These periodicities occur at different phases of the solar cycle during successive phases. We present a time-series analysis of sunspot area, flare and CME occurrence during Cycle 23 and the rising phase of Cycle 24 from 1996 to 2011. We find that the flux emergence, represented by sunspot area, has multiple periodicities. Flares and CMEs, however, do not occur with the same period as the flux emergence. Using the results of this study, we discuss the possible activity sources producing emerging flux. 相似文献
3.
本文对太阳活动第２１周、２２周（１９７６年—１９９２年间）９７个质子活动区进行统计分析，包括活动区的面积、型别、磁结构、半影纤维等，结果表明：７５％的质子耀斑产生于面积为５００≤Ｓｐ≤３０００单位的黑子群中；耀斑爆发前一天及后一天活动区面积有显著减少；质子活动区含δ复杂磁结构的占７０％；具有半影旋涡形态的质子活动区中，约７７％的耀斑发生在旋涡黑子出现以后。 相似文献
4.
Automatic Short-Term Solar Flare Prediction Using Machine Learning and Sunspot Associations 总被引：2，自引：0，他引：2
In this paper, a machine-learning-based system that could provide automated short-term solar flare prediction is presented.
This system accepts two sets of inputs: McIntosh classification of sunspot groups and solar cycle data. In order to establish
a correlation between solar flares and sunspot groups, the system explores the publicly available solar catalogues from the
National Geophysical Data Center to associate sunspots with their corresponding flares based on their timing and NOAA numbers.
The McIntosh classification for every relevant sunspot is extracted and converted to a numerical format that is suitable for
machine learning algorithms. Using this system we aim to predict whether a certain sunspot class at a certain time is likely
to produce a significant flare within six hours time and if so whether this flare is going to be an X or M flare. Machine
learning algorithms such as Cascade-Correlation Neural Networks (CCNNs), Support Vector Machines (SVMs) and Radial Basis Function
Networks (RBFN) are optimised and then compared to determine the learning algorithm that would provide the best prediction
performance. It is concluded that SVMs provide the best performance for predicting whether a McIntosh classified sunspot group
is going to flare or not but CCNNs are more capable of predicting the class of the flare to erupt. A hybrid system that combines
a SVM and a CCNN is suggested for future use. 相似文献
5.
G.S. Suryanarayana 《New Astronomy》2010,15(3):313-317
Solar activity, such as flares and CMEs, affect the interplanetary medium, and Earth’s atmosphere. Therefore, to understand the Space Weather, we need to understand the mechanisms of solar activity. Towards this end, we use 1135 events of solar Hα flares and the positional data of sunspots from the archive of Solar Geophysical Data (SGD) for the period January–April, 2000 and compute the abnormal rotation rates that lead to high flare productivity. We report that the occurrence of 5 or more flares in a day in association with a given sunspot group can be defined as high flare productivity and the sunspots that have an abnormal rotation rates of ～4–10 deg day?1 trigger high flare productivity. Further, in order to compare the flare productivity expressed as the strength of the flux emitted, especially the soft X-ray (SXR) flares in the frequency range of 1–8 Å, we compute the flare index of SXR flares and find that 8 out of 28 active regions used in this study satisfy the requirement for being flare productive. This enables us to conclude that the high rotation rates of sunspots are an important mechanism to understand the flare productivity, especially numerical flare productivity that includes flares of all class. 相似文献
6.
Solar neutrino in relation to solar activity 总被引：2，自引：0，他引：2
D. Basu 《Solar physics》1992,142(1):205-208
Here we have carried out a power-spectrum analysis of solar nuclear gamma-ray (NGR) flares observed by SMM and HINOTORI satellites. The solar NGR flares show a periodicity of 152 days, confirming the existence of a 152–158 days periodicity in the occurrence of solar activity phenomena and also indicating that the NGR flares are a separate class of solar flares. The power-spectrum analysis of the daily sunspot areas on the Sun for the period 1980–1982 shows a peak around 159 days while sunspot number data do not show any periodicity (Verma and Joshi, 1987). Therefore, only sunspot area data should be treated as an indicator of solar activity and not the daily sunspot number data. 相似文献
7.
We reported recently some rapid changes of sunspot structure in white-light(WL) associated with major flares.We extend the study to smaller events and present here results of a statistical study of this phenomenon.In total,we investigate 403 events from 1998 May 9 to 2004 July 17,including 40 X-class,174 M-class,and 189 C-class flares.By monitoring the structure of the flaring active regions using the WL observations from the Transition Region and Coronal Explorer(TRACE),we find that segments in the outer sunspot structure decayed rapidly right after many flares;and that,on the other hand,the central part of sunspots near the flare-associated magnetic neutral line became darkened.These rapid and permanent changes are evidenced in the time profiles of WL mean intensity and are not likely resulted from the flare emissions.Our study further shows that the outer sunspot structure decay as well as the central structure darkening are more likely to be detected in larger solar flares.For X-class flares,over 40% events show distinct sunspot structure change.For M-and C-class flares,this percentage drops to 17% and 10%,respectively.The results of this statistical study support our previously proposed reconnection picture,i.e.,the flare-related magnetic fields evolve from a highly inclined to a more vertical configuration. 相似文献
8.
It is known that ??-type sunspot groups have a high flare productivity and produce strong flares. In particular, ?|?? type sunspots are the most active type of all. A ?|?? active region NOAA?9957 with frequent flux cancellations but without any marked flare activity during its decay phase was studied in this work. Using SOHO/MDI Dopplergrams and magnetograms, we detected continuous prominent downflow motions of 1500??C?1700?m?s?1 for several hours on the magnetic neutral line in this region. In the downflow region, penumbral structures were observed to decay. We will interpret and discuss the phenomenon as a case of submergence of the magnetic flux. 相似文献
9.
Time series of daily numbers of solar Hα flares from 1955 to 1997 are studied by means of wavelet power spectra with regard
to predominant periods in the range of ∼ 24 days (synodic). A 24-day period was first reported by Bai (1987) for the occurrence
rate of hard X-ray flares during 1980–1985. Considering the northern and southern hemisphere separately, we find that the
24-day period is not an isolated phenomenon but occurs in each of the four solar cycles investigated (No. 19–22). The 24-day
period can be established also in the occurrence rate of subflares but occurs more prominently in major flares (importance
classes ≥ 1). A comparative analysis of magnetically classified active regions subdivided into magnetically complex (i.e.,
including a γ and/or δ configuration) and non-complex (α, β) reveals a significant relation between the appearance of the
24-day period in Hα flares and magnetically complex sunspot groups, whereas it cannot be established for non-complex groups.
It is suggested that the 24-day period in solar flare occurrence is related to a periodic emergence of new magnetic flux rather
than to the surface rotation of sunspots. 相似文献
10.
We examine daily records of sunspot group areas (measured in millionths of a solar hemisphere or μHem) for the last 130 years
to determine the rate of decay of sunspot group areas. We exclude observations of groups when they are more than 60° in longitude
from the central meridian and only include data when at least three days of observations are available following the date
of maximum area for a group’s disk passage. This leaves data for over 18 000 measurements of sunspot group decay. We find
that the decay rate increases linearly from 28 μHem day−1 to about 140 μHem day−1 for groups with areas increasing from 35 μHem to 1000 μHem. The decay rate tends to level off for groups with areas larger
than 1000 μHem. This behavior is very similar to the increase in the number of sunspots per group as the area of the group
increases. Calculating the decay rate per individual sunspot gives a decay rate of about 3.65 μHem day−1 with little dependence upon the area of the group. This suggests that sunspots decay by a Fickian diffusion process with
a diffusion coefficient of about 10 km2 s−1. Although the 18 000 decay rate measurements are lognormally distributed, this can be attributed to the lognormal distribution
of sunspot group areas and the linear relationship between area and decay rate for the vast majority of groups. We find weak
evidence for variations in decay rates from one solar cycle to another and for different phases of each sunspot cycle. However,
the strongest evidence for variations is with latitude and the variations with cycle and phase of each cycle can be attributed
to this variation. High latitude spots tend to decay faster than low latitude spots. 相似文献
11.
The extremely low sunspot activity during the period of the Maunder minimum 1645–1715 was confirmed by group sunspot numbers, a new sunspot index constructed by Hoyt and Schatten (1998a,b). Neither sunspots nor auroral data time behavior indicate the presence of 11-year solar cycles as stated by Eddy (1976). The evidence for solar cycles was found in the butterfly diagram, constructed from observations made at Observatoire de Paris. After Clivier, Boriakoff, and Bounar (1998) the solar cycles were reflected also in geomagnetic activity. Results are supported by the variation of cosmogenic isotopes 10Be and 14C. The majority of the observed 14 naked-eye sunspots occurred on days when telescopic observations were not available. A part of them appeared in the years when no spot was allegedly observed. Two-ribbon flares appear in plages with only very small or no sunspots. Some of these flares are geoactive. Most aurorae (90%), which were observed during the Maunder minimum, appeared in years when no spot was observed. Auroral events as a consequence of proton flares indicate that regions with enhanced magnetic field can occur on the Sun when these regions do not produce any sunspots. 相似文献
12.
Markus J. Aschwanden 《Solar physics》2011,274(1-2):99-117
We analyze the occurrence-frequency distributions of peak fluxes [P], total fluxes [E], and durations [T] of solar flares over the last three solar cycles (during 1980??C?2010) from SMM/HXRBS, CGRO/BATSE, and RHESSI hard X-ray data. From the synthesized data we find powerlaw slopes with mean values of ?? P =1.73±0.07 for the peak flux, ?? E =1.62±0.12 for the total flux, and ?? T =1.99±0.35 for flare durations. We find a tendency of an anti-correlation of the powerlaw slope of peak fluxes with the flare rate or sunspot number as a function of the solar cycle. The occurrence powerlaw slope is always steeper by ??????0.1 during a solar-cycle minimum compared with the previous solar-cycle maximum, but the relative amplitude varies for each cycle or instrument. Since each solar cycle has been observed with a different instrument, part of the variation could be attributed to instrumental characteristics and different event selection criteria used in generating the event catalogs. The relatively flatter powerlaw slopes during solar maxima could indicate more energetic flares with harder electron-energy spectra, probably due to a higher magnetic complexity of the solar corona. This would imply a non-stationarity (or solar-cycle dependence) of the coronal state of self-organized criticality. 相似文献
13.
The relationship between sunspot area and other observable solar parameters, such as spectral solar irradiance or total magnetic
flux, is frequently sought by examining scatterplots of daily data, which generally show a non-linear distribution of points.
We show that the scatterplots are consistent with our published result that these observable solar parameters are related
to sunspot area by a transformation that is both linear and time invariant, namely by convolution with a finite impulse response
function. Most solar parameters are affected by extended active regions, not just by sunspots. The fact that a complex active
region evolves much more slowly than its associated sunspots provides a simple physical explanation of the observed non-linearities
in scatterplots. 相似文献
14.
In this work we study the mid-term periodicities (MTPs), between 1 and 2 years, of the sunspot groups and the flare index (FI), by separating the data into hemispheres and spectral bands (SBs) according to the most significant periodicities presented by these phenomena. We found that the MTP of sunspot groups has a diminished power during the Modern Minimum and an increased power during the Modern Maximum, with the exception of cycle 20. For flares, the MTP has a diminished power during the low activity cycle 20, and an increased power during cycles 21 and 22. Therefore, for both sunspot groups and FI, cycle 20 shows a very diminished power followed by the active and higher-power cycles 21 and 22; cycle 23 shows a weaker power than cycles 21 and 22. It is uncertain whether MTP can be a precursor of a long-term minimum of solar activity or not, as has been previously suggested. Also, there is no one-to-one correlation between the cycle intensity and the importance of MTP. Concerning the quasi-biennial periodicities and the theory of two kinds of dynamos, we notice the tendency that higher-power cycles mean weaker coupling in the model. Concerning the hemispheric north-south asymmetry, for sunspot groups the southern hemisphere dominates in most of the SBs, while for FI the northern hemisphere dominates for all the SBs. Additionally, the time lag found between the two hemispheres indicates that the degrees of coupling in the photosphere for sunspot groups and in the corona for flares are between moderate and strong. Finally, the modulation shown by the MTP time series suggests that these periodicities are the product of chaotic quasi-periodic processes and not of stochastic processes. 相似文献
15.
We show that daily sunspot areas can be used in a simple, single parameter model to reconstruct daily variations in several
other solar parameters, including solar spectral irradiance and total magnetic flux. The model assumes that changes in any
given parameter can be treated mathematically as the response of the system to the emergence of a sunspot. Using cotemporal
observational data, we compute the finite impulse response (FIR) function that describes that response in detail, and show
that the response function has been approximately stationary over the time period for which data exist. For each parameter,
the impulse response function describes the physical evolution of that part of a solar active region that is the source of
the measured variability. We show that the impulse response functions are relatively narrow functions, no more than 3 years
wide overall. Each exhibits a pre-active, active, and post-active region component; the active region component dominates
the variability of most of the parameters studied. 相似文献
16.
We derive an occurrence frequency for white-light flares (WLF) of 15.5 ± 4.5 yr?1 during a 2.6 year period following the maximum of solar cycle 21. This compares with a frequency 5–6 yr?1 derived by McIntosh and Donnelly (1972) during solar cycle 20. We find that the higher frequency of the more recently observed WLFs is due to the availability of patrol data at shorter wavelengths (λ ? 4000 Å), where the contrast of the flare emission is increased; the improved contrast has allowed less energetic (and hence more frequently occurring) events to be classified as WLFs. We find that sufficient conditions for the occurrence of a WLF are: active region magnetic class = delta; sunspot penumbra class = K, with spot group area ≥ 500 millionths of the solar hemisphere; 1–8 Å X-ray burst class ≥ X2. 相似文献
17.
We perform a nonlinear study of the short-term correlation properties of the solar activity (daily range) in order to reveal
their long-life variations. We estimate the lifetime of the high-frequency component of a Markov-type signal when the high-frequency
component is modulated by a slowly varying multiplicative factor. This treatment is applied to different series of solar activity:
Wolf Sunspot numbers (WSN), Sunspot Group numbers (SGN), and Royal Greenwich Observatory (RGO) sunspot group series. We obtain
that all the lifetime estimates exhibit similar temporal variations that agree with the variations of the sunspot lifetimes
directly measured from the RGO data and those of the sunspot areas. An increase of lifetimes by a factor 1.4 is observed from
1915 to 1940. At the same time, a stable ratio is observed between the sunspot group’s maximal area and the lifetime, confirming
the Gnevyshev–Waldmeier-type relationship. The analysis identifies also time intervals where the homogeneity of the different
time series may be questioned. 相似文献
18.
The degree of association between geoeffective (SID producing) flares (hereafter called SID flares) and sunspot morphology is examined. It is found that: (1) the frequency of SID flares associated with sunspot groups is linear function of sunspot area and rate of change in area; (2) the SID flare intensity is dependent on the sunspot area and on the magnetic morphology (field geometry); (3) the probability of a sunspot group being magnetically complex (henceforth called complex ratio) is a linear function of spot area, the larger this area the more likely a group is in the βγ or δ magnetic class; (4) the complex ratio exhibits the greatest degree of association to SID flare frequency. We conclude from these results that a higher frequency of D-region ionizing flares (emitting a soft X-ray flux >2 × 10?3 erg cm?2 s?1) is likely to accompany the disk transit of large area, complex spot groups. This combination of morphological factors reflects a shearing of the associated force-free magnetic field, with accumulation of free magnetic energy to power SID flares. Mutual polarity intrusion would be one observational signature of the pre-flare energy storing process. 相似文献
19.
Sunspot records in the seventeenth century provide important information on the solar activity before the Maunder minimum, yielding reliable sunspot indices and the solar butterfly diagram. Galilei’s letters to Cardinal Francesco Barberini and Marcus Welser contain daily solar observations on 3?–?11 May, 2 June?–?8 July, and 19?–?21 August 1612. These historical archives do not provide the time of observation, which results in uncertainty in the sunspot coordinates. To obtain them, we present a method that minimizes the discrepancy between the sunspot latitudes. We provide areas and heliographic coordinates of 82 sunspot groups. In contrast to Sheiner’s butterfly diagram, we found only one sunspot group near the Equator. This provides a higher reliability of Galilei’s drawings. Large sunspot groups are found to emerge at the same longitude in the northern hemisphere from 3 May to 21 August, which indicates an active longitude. 相似文献
20.
Howard A. Garcia 《Solar physics》1990,127(1):185-197
The record of flare incidence from January 1969 to October 1988 indicates that the north-south (N-S) distribution of large flares is periodic and approximately in phase with the 11-year sunspot cycle. These data are based on observations of the whole-disk Sun in continuum soft X-rays which commenced in early 1969 and have proceeded without interruption to the present time. The pattern of occurrence, observed for slightly less than two sunspot cycles, is that large flares concentrate in north heliographic latitudes soon after solar minimum and then migrate gradually southward as the cycle progresses. By the end of the cycle, most large flares occur in the south. The degree of N-S asymmetry apparently is a function of the intensity of the flare; the most intense flares show the largest amount of N-S asymmetry. The data suggest that sunspots and flares may be driven by distinctly different excitation mechanisms arising at different levels in the convection zone. This conjecture is supported by recent work of Bai (1987, 1988), who has discovered that the superactive regions producing the majority of flares rotate at a speed substantially different from the Carrington rate, which is based primarily on the observed motion of sunspots. 相似文献