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1.
This article is an update of a study (Tapping and Valdès in Solar Phys. 272, 337, 2011) made in the early part of Cycle 24 using an intercomparison of various solar activity indices (including sunspot number and the 10.7 cm solar radio flux), in which it was concluded that a change in the relationship between photospheric and chromospheric/coronal activity took place just after the maximum of Cycle 23 and continued into Cycle 24. Precursors (short-term variations) were detected in Cycles 21 and 22. Since then the sunspot number index data have been substantially revised. This study is intended to be an update of the earlier study and to assess the impact of the revision of the sunspot number data upon those conclusions. This study compares original and revised sunspot number, total sunspot area, and 10.7 cm solar radio flux. The conclusion is that the transient changes in Cycles 21 and 22, and the more substantial change in Cycle 23, remain evident. Cycle 24 shows indications that the deviation was probably another short-term one. 相似文献
2.
We have examined polar magnetic fields for the last three solar cycles, viz. Cycles 21, 22, and 23 using NSO/Kitt Peak synoptic magnetograms. In addition, we have used SOHO/MDI magnetograms to derive
the polar fields during Cycle 23. Both Kitt Peak and MDI data at high latitudes (78° – 90°) in both solar hemispheres show
a significant drop in the absolute value of polar fields from the late declining phase of the Solar Cycle 22 to the maximum
of the Solar Cycle 23. We find that long-term changes in the absolute value of the polar field, in Cycle 23, are well correlated
with changes in meridional-flow speeds that have been reported recently. We discuss the implication of this in influencing
the extremely prolonged minimum experienced at the start of the current Cycle 24 and in forecasting the behavior of future
solar cycles. 相似文献
3.
Based on the monthly sunspot numbers (SSNs), the solar-flare index (SFI), grouped solar flares (GSFs), the tilt angle of heliospheric current sheet (HCS), and cosmic-ray intensity (CRI) for Solar Cycles 21?–?24, a detailed correlation study has been performed using the cycle-wise average correlation (with and without time lag) method as well as by the “running cross-correlation” method. It is found that the slope of regression lines between SSN and SFI, as well as between SSN and GSF, is continuously decreasing from Solar Cycle 21 to 24. The length of regression lines has significantly decreased during Cycles 23 and 24 in comparison to Cycles 21 and 22. The cross-correlation coefficient (without time lag) between SSN–CRI, SFI–CRI, and GSF–CRI has been found to be almost the same during Cycles 21 and 22, while during Cycles 23 and 24 it is significantly higher between SSN–CRI and HCS–CRI than for SFI–CRI and GSF–CRI. Considering time lags of 1 to 20 months, the maximum correlation coefficient (negative) amongst all of the sets of solar parameters is observed with almost the same time lags during Cycles 21?–?23, whereas exceptional behaviour of the time lag has been observed during Cycle 24, as the correlation coefficient attains its maximum value with two time lags (four and ten months) in the case of the SSN–CRI relationship. A remarkably large time lag (22 months) between HCS and CRI has been observed during the odd-numbered Cycle 21, whereas during another odd cycle, Cycle 23, the lag is small (nine months) in comparison to that for other solar/flare parameters (13?–?15 months). On the other hand, the time lag between SSN–CRI and HCS–CRI has been found to be almost the same during even-numbered Solar Cycles 22 and 24. A similar analysis has been performed between SFI and CRI, and it is found that the correlation coefficient is maximum at zero time lag during the present solar cycle. The GSFs have shown better maximum correlation with CRI as compared to SFI during Cycles 21 to 23, indicating that GSF could also be used as a significant solar parameter to study the cosmic-ray modulation. Furthermore, the running cross-correlation coefficient between SSN–CRI and HCS–CRI, as well as between solar-flare activity parameters (SFI and GSF) and CRI is observed to be strong during the ascending and descending phases of solar cycles. The level of cosmic-ray modulation during the period of investigation shows the appropriateness of different parameters in different cycles, and even during the different phases of a particular solar cycle. We have also studied the galactic cosmic-ray modulation in relation to combined solar and heliospheric parameters using the empirical model suggested by Paouris et al. (Solar Phys.280, 255, 2012). The proposed model for the calculation of the modulated cosmic-ray intensity obtained from the combination of solar and heliospheric parameter gives a very satisfactory value of standard deviation as well as \(R^{2}\) (the coefficient of determination) for Solar Cycles 21?–?24. 相似文献
4.
A stochastic prediction model for the sunspot cycle is proposed. The prediction model is based on a modified binary mixture
of Laplace distribution functions and a moving-average model over the estimated model parameters. A six-parameter modified
binary mixture of Laplace distribution functions is used for the modeling of the shape of a generic sunspot cycle. The model
parameters are estimated for 23 sunspot cycles independently, and the primary prediction-model parameters are derived from
these estimated model parameters using a moving-average stochastic model. A correction factor (hump factor) is introduced
to make an initial prediction. The hump factor is computed for a given sunspot cycle as the ratio of the model estimated after
the completion of a sunspot cycle (post-facto model) and the prediction of the moving-average model. The hump factors can be applied one at a time over the moving-average
prediction model to get a final prediction of a sunspot cycle. The present model is used to predict the characteristics of
Sunspot Cycle 24. The methodology is validated using the previous Sunspot Cycles 21, 22, and 23, which shows the adequacy
and the applicability of the prediction model. The statistics of the variations of sunspot numbers at high solar activity
are used to provide the lower and upper bound for the predictions using the present model. 相似文献
5.
A. Kilcik V. Yurchyshyn B. Donmez V. N. Obridko A. Ozguc J. P. Rozelot 《Solar physics》2018,293(4):63
We analyzed temporal and periodic variations of sunspot counts (SSCs) in flaring (C-, M-, or X-class flares), and non-flaring active regions (ARs) for nearly three solar cycles (1986 through 2016). Our main findings are as follows: i) temporal variations of monthly means of the daily total SSCs in flaring and non-flaring ARs behave differently during a solar cycle and the behavior varies from one cycle to another; during Solar Cycle 23 temporal SSC profiles of non-flaring ARs are wider than those of flaring ARs, while they are almost the same during Solar Cycle 22 and the current Cycle 24. The SSC profiles show a multi-peak structure and the second peak of flaring ARs dominates the current Cycle 24, while the difference between peaks is less pronounced during Solar Cycles 22 and 23. The first and second SSC peaks of non-flaring ARs have comparable magnitude in the current solar cycle, while the first peak is nearly absent in the case of the flaring ARs of the same cycle. ii) Periodic variations observed in the SSCs profiles of flaring and non-flaring ARs derived from the multi-taper method (MTM) spectrum and wavelet scalograms are quite different as well, and they vary from one solar cycle to another. The largest detected period in flaring ARs is \(113\pm 1.6~\mbox{days}\) while we detected much longer periodicities (\(327\pm 13\), \(312 \pm 11\), and \(256\pm 8~\mbox{days}\)) in the non-flaring AR profiles. No meaningful periodicities were detected in the MTM spectrum of flaring ARs exceeding \(55\pm 0.7~\mbox{days}\) during Solar Cycles 22 and 24, while a \(113\pm 1.3~\mbox{days}\) period was detected in flaring ARs of Solar Cycle 23. For the non-flaring ARs the largest detected period was only \(31\pm 0.2~\mbox{days}\) for Cycle 22 and \(72\pm 1.3~\mbox{days}\) for the current Cycle 24, while the largest measured period was \(327\pm 13~\mbox{days}\) during Solar Cycle 23. 相似文献
6.
The properties of the heliospheric magnetic field and the solar wind were substantially different in the unusual solar minimum between Cycles 23 and 24: the magnetic-field strength was substantially reduced, as were the flow properties of the solar wind, such as the mass flux. Explanations for these changes are offered that do not require any substantial reconsideration of the general understandings of the behavior of the heliospheric magnetic field and the solar wind that were developed in the minimum of Cycle 22?–?23. Solar-wind composition data are used to demonstrate that there are two distinct regions of solar wind: solar wind likely to originate from the stalk of the streamer belt (the highly elongated loops that underlie the heliospheric current sheet), and solar wind from outside this region. The region outside the streamer-stalk region is noticeably larger in the minimum of Cycle 23?–?24; however, the increased area can account for the reduction in the heliospheric magnetic-field strength in this minimum. Thus, the total magnetic flux contained in this region is the same in the two minima. Various correlations among the solar-wind mass flux and coronal electron temperature inferred from solar-wind charge states were developed for the Cycle 22?–?23 solar minimum. The data for the minimum of Cycle 23?–?24 suggest that the correlations still hold, and thus the basic acceleration mechanism is unchanged in this minimum. 相似文献
7.
W. Dean Pesnell 《Solar physics》2014,289(6):2317-2331
We describe using Ap and F10.7 as a geomagnetic-precursor pair to predict the amplitude of Solar Cycle 24. The precursor is created by using F10.7 to remove the direct solar-activity component of Ap. Four peaks are seen in the precursor function during the decline of Solar Cycle 23. A recurrence index that is generated by a local correlation of Ap is then used to determine which peak is the correct precursor. The earliest peak is the most prominent but coincides with high levels of non-recurrent solar activity associated with the intense solar activity of October and November 2003. The second and third peaks coincide with some recurrent activity on the Sun and show that a weak cycle precursor closely following a period of strong solar activity may be difficult to resolve. A fourth peak, which appears in early 2008 and has recurrent activity similar to precursors of earlier solar cycles, appears to be the “true” precursor peak for Solar Cycle 24 and predicts the smallest amplitude for Solar Cycle 24. To determine the timing of peak activity it is noted that the average time between the precursor peak and the following maximum is ≈?6.4 years. Hence, Solar Cycle 24 would peak during 2014. Several effects contribute to the smaller prediction when compared with other geomagnetic-precursor predictions. During Solar Cycle 23 the correlation between sunspot number and F10.7 shows that F10.7 is higher than the equivalent sunspot number over most of the cycle, implying that the sunspot number underestimates the solar-activity component described by F10.7. During 2003 the correlation between aa and Ap shows that aa is 10 % higher than the value predicted from Ap, leading to an overestimate of the aa precursor for that year. However, the most important difference is the lack of recurrent activity in the first three peaks and the presence of significant recurrent activity in the fourth. While the prediction is for an amplitude of Solar Cycle 24 of 65±20 in smoothed sunspot number, a below-average amplitude for Solar Cycle 24, with maximum at 2014.5±0.5, we conclude that Solar Cycle 24 will be no stronger than average and could be much weaker than average. 相似文献
8.
We investigate the presence and temporal evolution of short- and intermediate-term periodicities in the daily data of sunspot
numbers and coronal index for the time span from May 1996 to December 2008, which covers the entire Solar Cycle 23. The daily
sunspot number data have been analyzed for the full disk, and for northern and southern hemispheres of the Sun. Using the
wavelet power spectrum technique, we find a number of quasi-periodic oscillations in all the data sets. We also find a prominent
period of 22 to 35 days in the high-frequency range, and detect the Rieger period of 150 to 160 days in both data sets during
different phases of Cycle 23. We also detect ∼1.3 year oscillation in both sunspot and coronal index time series. In addition,
we find a number of other short and mid-term periods. We discuss possible explanations of the observed periodicities in the
light of previous results and existing numerical models. 相似文献
9.
We investigate solar activity by focusing on double maxima in solar cycles and try to estimate the shape of the current solar cycle (Cycle 24) during its maximum. We analyzed data for Solar Cycle 24 by using Learmonth Solar Observatory sunspot-group data collected since 2008. All sunspot groups (SGs) recorded during this time interval were separated into two groups: The first group includes small SGs [A, B, C, and H classes according to the Zurich classification], the second group consists of large SGs [D, E, and F]. We then calculated how many small and large sunspot groups occurred, their sunspot numbers [SSN], and the Zurich numbers [Rz] from their daily mean numbers as observed on the solar disk during a given month. We found that the temporal variations for these three different separations behave similarly. We also analyzed the general shape of solar cycles from Cycle 1 to 23 by using monthly International Sunspot Number [ISSN] data and found that the durations of maxima were about 2.9 years. Finally, we used the ascending time and SSN relationship and found that the maximum of Solar Cycle 24 is expected to occur later than 2011. Thus, we conclude that i) one possible reason for a double maximum in solar cycles is the different behavior of large and small sunspot groups, and ii) a double maximum is expected for Solar Cycle 24. 相似文献
10.
For the rising branch of Cycle 22, 1987 January—1989 November, we plot the daily total flux S at each of the five wavelengths 2.0, 3.4, 6.0, 10.7 and 21.2 cm against the apparent sunspot area of the dominant sunspot Ay and find that, for several large active areas, the locus is located below the average regression line, and the increase in the radio flux is insignificant compared to the increase in the sunspot area. 相似文献
11.
S. Watari 《Solar physics》2018,293(2):23
The activity of Solar Cycle 24 has been extraordinarily low. The yearly averaged solar-wind speed is also lower in Cycle 24 than in Cycles 22 and 23. The yearly averaged speed in the rising phase of Cycle 21 is as low as that of Cycle 24, although the solar activity of Cycle 21 is higher than that of Cycle 24. The relationship between the solar-wind temperature and its speed is preserved under the solar-wind conditions of Cycle 24. Previous studies have shown that only a few percent of intense geomagnetic storms (minimum \(\mathrm{Dst} < -100\) nT) were caused by high-speed solar-wind flows from coronal holes. We identify two geomagnetic storms associated with coronal holes within the 19 intense geomagnetic storms that took place in Cycle 24. 相似文献
12.
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
13.
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. 相似文献
14.
S. R. Walton G. A. Chapman A. M. Cookson J.J. Dobias D. G. Preminger 《Solar physics》1998,179(1):31-42
Daily, photometric, full-disk digital solar images have been taken at the San Fernando Observatory (SFO) at two resolutions and in several wavelengths for more than eleven years. We describe the standard data processing techniques used for these images, including: calibration, limb fitting, geometric correction, and production of a solar contrast map by limb-darkening removal. The resulting contrast maps have a photometric accuracy which is often a few tenths of a percent. We show that the geometric accuracy of our images, as measured by the reproducibility of disk and sunspot areas, is very high as well. The techniques described in this paper should be applicable to any instrument producing full-disk photometric images. 相似文献
15.
Solar empirical models based on regression of two variability indices for radiation from the photosphere and chromosphere
fit total solar irradiance (TSI) observations with accuracy comparable to the precision reported for the observations themselves.
However, the physical meaning of the fitting coefficients and their stability during different phases of the solar cycle has
not been examined in detail. We test the stability of the coefficients in regression models of the VIRGO TSI observations
over the nine years from the minimum of Cycle 23 in 1996 through the maximum to 2005. We also show how the coefficients converge
to the ‘`best fit’' using a search in the coefficient space. Analysis of TSI variability in different phases of this cycle
shows little change in regression models as long as the time periods used in the regression are long enough to show the slow
solar cycle variation in TSI. We extend our analysis to TSI observations from ERB, ACRIM2, ACRIM3, DIARAD, and TIM. The regression
models from these time series show large systematic differences in fitting coefficients for the plage and sunspot indices
that we used. These differences are significantly larger than the estimated uncertainties in the coefficients and point to
the difficulty of combining observations from different instruments to create an accurate composite TSI record over several
solar cycles. Our results clearly demonstrate the improvement in precision of TSI measurements from the Nimbus 7 ERB in Cycle
22 to the latest SORCE TIM data in Cycle 23. 相似文献
16.
R. A. Harrison J. A. Davies D. Barnes J. P. Byrne C. H. Perry V. Bothmer J. P. Eastwood P. T. Gallagher E. K. J. Kilpua C. Möstl L. Rodriguez A. P. Rouillard D. Odstrčil 《Solar physics》2018,293(5):77
We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA’s twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS project. Here, we focus on the observational characteristics of CMEs imaged in the heliosphere by the inner (HI-1) cameras, while following papers will present analyses of CME propagation through the entire HI fields of view. More specifically, in this paper we present distributions of the basic observational parameters – namely occurrence frequency, central position angle (PA) and PA span – derived from nearly 2000 detections of CMEs in the heliosphere by HI-1 on STEREO-A or STEREO-B from the minimum between Solar Cycles 23 and 24 to the maximum of Cycle 24; STEREO-A analysis includes a further 158 CME detections from the descending phase of Cycle 24, by which time communication with STEREO-B had been lost. We compare heliospheric CME characteristics with properties of CMEs observed at coronal altitudes, and with sunspot number. As expected, heliospheric CME rates correlate with sunspot number, and are not inconsistent with coronal rates once instrumental factors/differences in cataloguing philosophy are considered. As well as being more abundant, heliospheric CMEs, like their coronal counterparts, tend to be wider during solar maximum. Our results confirm previous coronagraph analyses suggesting that CME launch sites do not simply migrate to higher latitudes with increasing solar activity. At solar minimum, CMEs tend to be launched from equatorial latitudes, while at maximum, CMEs appear to be launched over a much wider latitude range; this has implications for understanding the CME/solar source association. Our analysis provides some supporting evidence for the systematic dragging of CMEs to lower latitude as they propagate outwards. 相似文献
17.
I. G. Richardson T. T. von Rosenvinge H. V. Cane E. R. Christian C. M. S. Cohen A. W. Labrador R. A. Leske R. A. Mewaldt M. E. Wiedenbeck E. C. Stone 《Solar physics》2014,289(8):3059-3107
Using observations from the High Energy Telescopes (HETs) on the STEREO A and B spacecraft and similar observations from near-Earth spacecraft, we summarize the properties of more than 200 individual >?25 MeV solar proton events, some detected by multiple spacecraft, that occurred from the beginning of the STEREO mission in October 2006 to December 2013, and provide a catalog of these events and their solar sources and associations. Longitudinal dependencies of the electron and proton peak intensities and delays to onset and peak intensity relative to the solar event have been examined for 25 three-spacecraft particle events. Expressed as Gaussians, peak intensities fall off with longitude with σ=47±14° for 0.7?–?4 MeV electrons, and σ=43±13° for 14?–?24 MeV protons. Several particle events are discussed in more detail, including one on 3 November 2011, in which ～?25 MeV protons filled the inner heliosphere within 90 minutes of the solar event, and another on 7 March 2012, in which we demonstrate that the first of two coronal mass ejections that erupted from an active region within ～?1 hour was associated with particle acceleration. Comparing the current Solar Cycle 24 with the previous cycle, the first >?25 MeV proton event was detected at Earth in the current solar cycle around one year after smoothed sunspot minimum, compared with a delay of only two months in Cycle 23. Otherwise, solar energetic particle event occurrence rates were reasonably similar during the rising phases of Cycles 23 and 24. However, the rate declined in 2013, reflecting the decline in sunspot number since the peak in the northern-hemisphere sunspot number in November 2011. Observations in late 2013 suggest that the rate may be rising again in association with an increase in the southern sunspot number. 相似文献
18.
John K. Lawrence 《Solar physics》1987,110(1):73-79
We examine published sunspot and calcium plage areas for 1620 solar active regions between 1974 and 1985. With these data we study the properties of ensemble-averaged active regions. The average sunspot area per region, the average plage to sunspot area ratio, and the average plage intensity of regions all vary significantly with the sunspot cycle and in correlation with one another. The average plage area per region varies significantly but is uncorrelated with the sunspot cycle and with the other quantities. While the plage and sunspot areas and the plage intensities of individual active regions observed over a two-year period are strongly correlated, the relationship among these quantities appears to change over an 11-yr period. These results suggest the existence of some energetic connection between active region sunspot areas and plage intensities. Further, if energy balance between sunspot luminosity deficits and facular luminosity excesses holds, then standard models relating these quantities to sunspot and plage areas will have to be modified. Overall energy balance can neither be established nor ruled out.Solar Cycle Workshop Paper. 相似文献
19.
Mykola I. Pishkalo 《Solar physics》2014,289(5):1815-1829
Correlations between monthly smoothed sunspot numbers at the solar-cycle maximum [R max] and duration of the ascending phase of the cycle [T rise], on the one hand, and sunspot-number parameters (values, differences and sums) near the cycle minimum, on the other hand, are studied. It is found that sunspot numbers two?–?three years around minimum correlate with R max or T rise better than those exactly at the minimum. The strongest correlation (Pearson’s r=0.93 with P<0.001 and Spearman’s rank correlation coefficient r S=0.95 with P=9×10?12) proved to be between R max and the sum of the increase of activity over 30 months after the cycle minimum and the drop of activity over 30 or 36 months before the minimum. Several predictions of maximal amplitude and duration of the ascending phase for Solar Cycle 24 are given using sunspot-number parameters as precursors. All of the predictions indicate that Solar Cycle 24 is expected to reach a maximal smoothed monthly sunspot number (SSN) of 70?–?100. The prediction based on the best correlation yields the maximal amplitude of 90±12. The maximum of Solar Cycle 24 is expected to be in December 2013?–?January 2014. The rising and declining phases of Solar Cycle 24 are estimated to be about 5.0 and 6.3 years, respectively. The minimum epoch between Solar Cycles 24 and 25 is predicted to be at 2020.3 with minimal SSN of 5.1?–?5.4. We predict also that Solar Cycle 25 will be slightly stronger than Solar Cycle 24; its maximal SSN will be of 105?–?110. 相似文献
20.
Polar coronal holes (PCHs) trace the magnetic variability of the Sun throughout the solar cycle. Their size and evolution have been studied as proxies for the global magnetic field. We present measurements of the PCH areas from 1996 through 2010, derived from an updated perimeter-tracing method and two synoptic-map methods. The perimeter-tracing method detects PCH boundaries along the solar limb, using full-disk images from the SOlar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT). One synoptic-map method uses the line-of-sight magnetic field from the SOHO/Michelson Doppler Imager (MDI) to determine the unipolarity boundaries near the poles. The other method applies thresholding techniques to synoptic maps created from EUV image data from EIT. The results from all three methods suggest that the solar maxima and minima of the two hemispheres are out of phase. The maximum PCH area, averaged over the methods in each hemisphere, is approximately 6 % during both solar minima spanned by the data (between Solar Cycles 22/23 and 23/24). The northern PCH area began a declining trend in 2010, suggesting a downturn toward the maximum of Solar Cycle 24 in that hemisphere, while the southern hole remained large throughout 2010. 相似文献