Sunspot Number Research Articles

Coronal mass ejection and solar activity for cycle 23 and 24; a comparative analysis of observational parameters

We analyzed sunspot tracers [sunspot number (SSN) and sunspot area (SSA)] and Coronal Mass Ejection (CME) observed parameters for cycle 23 and 24, comparing sunspot tracers time series with time series for CME parameters [Initial speed and Acceleration] for All and segregated CMEs for possible similarities in their variation pattern. A comparison of CME time series with solar activity (especially SSAT and SSN which seem to reflect the true general activity cycle) shows that fast CMEs follow the solar activity cycle but slow CMEs don’t. Also, CMEs with positive and negative acceleration follow the solar cycle but lags behind b 3monhs for cycle 24. However, the CME acceleration does not follow the solar cycle. CME distribution show that Slow CMEs increases in initial speed from one cycle to the other with a corresponding decrease in acceleration for CMEs with fast speeds. There is an almost insignificant increase in acceleration for CMEs with positive and negative acceleration. These charges are perhaps due to effect of solar wind.

An Early Assessment of the Forecast by the Solar Cycle 25 Prediction Panel

The effects of solar activity on technology have increased the interest in solar forecasting both in the scientific community and in society. With two and a half years of data available, we are approximately halfway to the maximum of Solar Cycle 25. Several research groups around the world published their predictions for this cycle. In this work, we assess the forecast made by the Solar Cycle 25 Prediction Panel. Analyzing the sunspot number data available, we conclude that Solar Cycle 25 is one of the weakest cycles since mid-18th century and, however, it is stronger than the initial forecast of the highest range predicted by the Solar Cycle 25 Prediction Panel for the two first years and a half of its ascending phase.

The quiet chromosphere: Phase relation with the solar cycle

The solar chromosphere was daily observed in the Ca II K line from 1915 August 10 to 1985 July 7, and correspondingly, 938 synoptic maps are measured. The valuable database is utilized to explore phase relationship of long-term evolution of the quiet chromosphere and sunspot numbers. Temporal change of the quiet chromosphere is found to be in anti-phase with the solar cycle on the whole, as the small-scale magnetic elements whose flux is in a span of (2.9-32.0)×1018(Mx) do. The abnormal heating of the quiet chromosphere is accordingly suggested to be related mainly to the magnetic elements, and they may likely function in reducing chromosphere material loss.

Solar and geomagnetic activity reduces pulmonary function and enhances particulate pollution effects

BackgroundIncreased solar and geomagnetic activity (SGA) may alter sympathetic nervous system activity, reduce antioxidant activity, and modulate physiochemical processes that contribute to atmospheric aerosols, all which may reduce pulmonary function. ObjectivesInvestigate associations between forced expiratory volume at 1 s (FEV1) and forced vital capacity (FVC) with SGA, and assess whether SGA enhances adverse effects of particulate pollution, black carbon (BC) and particulate matter ≤2.5 μm in diameter (PM2.5). Methods: We conducted a repeated measures analysis in 726 Normative Aging Study participants (Boston, Massachusetts, USA) between 2000 and 2017, using interplanetary magnetic field (IMF), planetary K index (Kp), and sunspot number (SSN) as SGA measures. Linear mixed effects models were used to assess exposure moving averages up to 28 days for both SGA and pollution. ResultsIncreases in IMF, Kp Index and SSN from the day of the pulmonary function test averaged through day 28 of were associated with a significant decrement in FEV1 and FVC, after adjusting for potential confounders. There were greater effects for longer moving averages and enhanced effects of PM2.5 and BC on FEV1 and FVC with increased SGA. For example, for each inter-quartile increase (4.55 μg/m3) in average PM2.5 28 days before testing, low IMF (10th percentile: 3.2 nT) was associated with a −21.4 ml (95 % CI: −60.8, 18.1) and −7.1 ml (95 % CI: −37.7, 23·4) decrease in FVC and FEV1, respectively; high IMF (90th percentile: 9.0 nT) was associated with a −120.7 ml (95 % CI:-166.5, −74.9) and −78.6 ml (95 % CI: −114.3, −42·8) decrease in FVC and FEV1, respectively. DiscussionIncreased periods of solar and geomagnetic activity may directly contribute to impaired pulmonary function and also enhance effects of PM2.5 and BC. Since exposure to solar activity is ubiquitous, stricter measures in reducing air pollution exposures are warranted, particularly in elderly populations.

Variations of IMF Cone Angle and IMF Clock Angle to Solar Cycles and Geomagnetic Storms

Interplanetary magnetic field (IMF) carried by solar wind and rooted at solar corona. Variations of IMF depend on solar surface activities, e.g. sunspots. Moreover, solar magnetic storms are connected by the IMF. IMF parameters, sunspot number, and geomagnetic index for more than 55 years were downloaded from OMNIWeb, which the data were obtained from several spacecraft in geostasionary and L1 Lagrange orbits. Solar cycles are measured in terms of variations in the number of sunspots and their surface areas. Both magnetic events of IMF and sunspots indicate the relation between solar cycles and IMF orientation which is clock angle and cone angle. IMF also interacts with the Earth’s magnetosphere, and it can cause geomagnetic storms. Cone angle and clock angle are derived from IMF components on X-axis, Y-axis, and Z-axis. Their frequency distribution charts on each solar cycle of 20 to 24 and their maxima phase and minima phase are the key points for the analysis. The plot of clock angle to Dst index as a geomagnetic index for each solar cycle was also derived. Based on the analysis, solar cycles are indicated to give an impact on the magnitude of each IMF component. It makes the peak of the charts shifted from the minima phase to the maxima phase. Other than that, the reconnection in magnetopause mostly occurs when the clock angle is between 1400–2520 or when the clock angle directions are southward. But the 23rd solar cycle shows the northward clock angle can also cause extreme geomagnetic storms.

Factors That Determine the Power-law Index of an Energy Distribution of Solar Flares

The power-law index of an occurrence frequency distribution of flares as a function of energy is one of the most important indicators to evaluate the contribution of small-scale flares to coronal heating. For a few decades, many studies tried to derive the power-law index using various instruments and methods. However, these results are various and the cause of this uncertainty is unknown due to the variety of observation conditions. Therefore, we investigated the dependence of the index on the solar activity, coronal features, released energy range, and active region properties such as magnetic flux, twist, and size. Our findings are (1) annual power-law index derived from time series of total solar irradiance (Sun-as-a-star observation analysis) has a negative correlation with sunspot number; (2) power-law index in active region is smaller than that of the quiet Sun and coronal holes; (3) power-law index is almost constant in the energy range of 1025 ≲ E ≲ 1030 erg; and (4) active regions that have more magnetic free energy density, unsigned magnetic flux, and shear angle tend to have smaller power-law indices. Based on the results and energy-scaling law of Petschek-type reconnection, we suggest that the power-law index of sunspot-scale events is smaller than that of granule-scale events. Moreover, we indicated that sunspot-scale events follow CSHKP flare model whereas granule-scale events follow Parker’s nanoflare model.

Solar activity facilitates daily forecasts of large earthquakes.

Despite the extensive literature related to earthquakes, an effective method to forecast and avoid occasional seismic hazards that cause substantial damage is lacking. The Sun has recently been identified as a potential precursor to earthquakes, although no causal relationship between its activity and the Earth's seismicity has been established. This study was aimed at investigating whether such a relationship exists and whether it can be used to improve earthquake forecasting. The edit distances between earthquake point processes were combined with delay-coordinate distances for sunspot numbers. The comparison of these two indicated the existence of unidirectional causal coupling from solar activity to seismicity on Earth, and a radial basis function regressor showed accuracy improvements in the largest magnitude prediction of next days by 2.6%-17.9% in the odds ratio when sunspot distances were included.

The Solar Wind Parker Spiral Angle Distributions and Variations at 1 au

Using the data from the Advanced Composition Explorer (ACE) and Wind spacecraft, we statistically studied the Parker spiral angle (PSA) of the solar wind magnetic field from 1998 to 2019 at 1 au. The PSA occurrences over both a Carrington rotation (CR) and a year can be well fitted by a Gaussian distribution. However, large-scale magnetic structures, such as interplanetary coronal mass ejections (ICMEs), can significantly deviate the PSA distribution of a CR from the Gaussian distribution. The PSA distributions of each CR and each year are affected by the solar activity: They are more concentrated at a relatively higher average PSA at solar maximum. There is also a weak anticorrelation between the yearly solar wind speed (v sw) and the average PSA. MESSENGER, Venus Express, and ACE observations at different heliocentric distances within 1 au show that the dominating polarities of the heliospheric magnetic field change greatly from year to year even when the solar activity is on the same level. Our results suggest that the PSA distribution in addition to the sunspot number can provide some new information on the magnetic field variation of the Sun.

A Comparative Study of non-deep Learning, Deep Learning, and Ensemble Learning Methods for Sunspot Number Prediction

ABSTRACT Solar activity has significant impacts on human activities and health. One most commonly used measure of solar activity is the sunspot number. This paper compares three important non-deep learning models, four popular deep learning models, and their five ensemble models in forecasting sunspot numbers. In particular, we propose an ensemble model called XGBoost-DL, which uses XGBoost as a two-level nonlinear ensemble method to combine the deep learning models. Our XGBoost-DL achieves the best forecasting performance (RMSE and MAE ) in the comparison, outperforming the best non-deep learning model SARIMA (RMSE and MAE ), the best deep learning model Informer (RMSE and MAE ) and the NASA’s forecast (RMSE and MAE ). Our XGBoost-DL forecasts a peak sunspot number of 133.47 in May 2025 for Solar Cycle 25 and 164.62 in November 2035 for Solar Cycle 26, similar to but later than the NASA’s at 137.7 in October 2024 and 161.2 in December 2034. An open-source Python package of our XGBoost-DL for the sunspot number prediction is available at https://github.com/yd1008/ts_ensemble_sunspot.

Efficacy and ethics of intensive predator management to save endangered caribou

AbstractLethal population control has a history of application to wildlife management and conservation. There is debate about the efficacy of the practice, but more controversial is the ethical justification and methods of killing one species in favor of another. This is the situation facing the conservation of woodland caribou (Rangifer tarandus caribou) in Canada. Across multiple jurisdictions, large numbers of wolves (Canis lupus), and to a lesser extent bears (Ursus americanus) and coyotes (C. latrans), are killed through trapping, poisoning or aerial shooting to halt or reverse continued declines of woodland caribou. While there is evidence to support the effectiveness of predator management as a stop‐gap solution, questions remain about the extent to which this activity can make a meaningful contribution to long‐term recovery. Also, there are myriad ethical objections to the lethal removal of predators, even if that activity is in the name of conservation. Debates about predator management, just one of numerous invasive actions for maintaining caribou, are made even more complex by the conflation of ethics and efficacy. Ultimately, long‐term solutions for the recovery of caribou require governments to stop delaying difficult decisions that address the real causes of population decline, habitat change.

A Study on Low Frequency Electromagnetic Cyclotron Waves in the Solar Wind

According to Wind observations between 2005 and 2015, this paper investigates the dependences of the occurrence of low frequency electromagnetic cyclotron waves (ECWs) on the plasma parameters, the solar cycle, and the orientations of alpha-proton drift velocity ( V d ) and the ambient magnetic field ( B ). The occurrence rates of ECWs with respect to six plasma parameters are calculated. Results show that the preferential conditions for generation of left-handed (LH) ECWs are higher proton temperature (T p ), higher proton velocity (V p ), lower proton density (N p ), stronger proton temperature anisotropy (T ⊥/T ∥), higher normalized alpha-proton drift velocity (V d /V A), and higher normalized alpha particle density (N α /N p ), where T ⊥ and T ∥ refer to proton temperatures perpendicular and parallel to B , and V A is the local Alfvén velocity. For right-handed (RH) ECWs, however, the dependences on these plasma parameters are not obvious. On the other hand, it is found that the occurrence rate of LH ECWs increases as the sunspot number decreases, and decreases as the sunspot number increases. Further investigation shows that the increased occurrence rate of LH ECWs is accompanied by an increase in the medians of V p , V d /V A, and N α /N p . For RH ECWs, the occurrence rate appears to be nearly unrelated to the sunspot number, suggesting a negligible correlation with the solar cycle. In addition, a modified angle is introduced to include the factors of orientation of B (anti-sunward or sunward) and angle between V d and B , simultaneously. It is found that the occurrence of LH ECWs has the strong preferential condition that V d is anti-sunward, while a different situation arises for RH ECWs. These results are discussed in the context of the temperature-anisotropy-driven instabilities with the effect of alpha particles.

Sunspot numbers and proton events in solar cycles 19 to 24

In this study we compare the mean annual sunspot numbers for the six most recent solar cycles (19 to 24) with the number of solar energetic proton events occurring in those years. Though most of the individual cycles exhibit quite strong correlations, when they are combined into a generic solar cycle the result is very significant (ρ = 0.98). For cycles 21 to 24 (when spacecraft observations have been regularly available), we also investigate the variation in the source location of the solar energetic proton events in relation to four peak flux thresholds in orders of magnitude from ≥10 to ≥10,000 pfu. For helio-latitudes within ±40° (the range within which active regions usually occur) there is negligible variation in the helio-longitude of the source regardless of the peak flux threshold. However, the effect on the helio-longitude of varying the peak flux threshold is very significant: the higher the threshold the closer is the median source longitude to 0°, the variation being almost uniform from ≥10 pfu (32°W) to ≥10,000 pfu (2°W). Finally, of the 10 events in cycles 19 to 24 with peak flux ≥10,000 pfu, all occurred between years 4 and 8 after solar minimum, all were the result of M- or X-class flares with associated halo CMEs and shock fronts, and the three most intense events (≥40,000 pfu) were all related to X-class flares which occurred in the longitude range 10–28°E. These results support and extend previous work by the cited authors, and have implications for solar-terrestrial relations and the effects of space weather within geospace.

Hemispheric asymmetry of long-term sunspot activity: sunspot relative numbers for 1939–2019

ABSTRACT Hemispheric asymmetry of solar magnetic structures is an important feature of solar cycles, and it involves dynamical processes in the interior of the Sun. For the first time, the data of the monthly sunspot relative numbers derived from the National Astronomical Observatory of Japan (NAOJ) is used to perform a long-term study (1939 March–2019 November) of the north–south asymmetry. The results show the following: (1) the sunspot relative numbers derived from NAOJ/Mitaka observatory are highly correlated with the international sunspot numbers obtained from the World Data Center Sunspot Index and Long-term Solar Observations, which justifies the use of Mitaka sunspot time series for hemispheric variation; (2) the change in the signs of the slopes of the regression lines fitted to the absolute asymmetry index suggest a kind of periodic variation in the hemispheric asymmetry, but the time interval of the current data base is not long enough to derive 8 or 12 cycles periodicity; and (3) for mid-term periods, there are enhanced powers for the period ranges around 3.7 yr, around 9 yr, between 30 and 50 yr. Our analysis results implicate a possible mechanism responsible for the generation and variation of the hemispheric coupling in the Sun.

The Solar Cycle Temporal Variation of the Solar Wind Charge Exchange X-Ray Lines

Solar wind charge exchange (SWCX) is the primary contamination of soft X-ray emission lines from the Milky Way (MW) hot gas. We report a solar cycle (≈10 yr) temporal variation of observed O vii and O viii emission line measurements in the XMM-Newton archive, which is tightly correlated with the solar cycle traced by the sunspot number (SSN). This temporal variation is expected to be associated with the heliospheric SWCX. Another observed correlation is that higher solar wind (SW) fluxes lead to higher O vii or O viii fluxes, which is due to the magnetospheric SWCX. We construct an empirical model to reproduce the observed correlation between the line measurements and the solar activity (i.e., the SW flux and the SSN). With this model we discovered a lag of yr between the O vii flux and the SSN. This time lag is a combination of the SW transit time within the heliosphere, the lag of the neutral gas distribution responding to solar activity, and the intrinsic lag between the SSN and the launch of a high-energy SW (i.e., O7+ and O8+). MW O vii and O viii fluxes have mean values of 5.4 L.U. and 1.7 L.U., which are reduced by 50% and 30%, compared to studies where the SWCX contamination is not removed. This correction also changes the determination of the density distribution and the temperature profile of the MW hot gas.

Study of the Mass-loss Rate from the Sun

We investigate the temporal evolution of the yearly total mass-loss rate (YTMLR) from the Sun through coronal mass ejections (CMEs) over solar cycles 23 and 24. The mass determination of CMEs can be subject to significant uncertainty. To minimize this problem, we have used extensive statistical analysis. For this purpose, we employed data included in the Coordinated Data Analysis Workshop (CDAW) catalog. We estimated the contributions to mass loss from the Sun from different subsamples of CMEs (selected on the basis of their masses, angular widths, and position angles). The temporal variations of the YTMLR were compared to those of the sunspot number (SSN), X-ray flare flux, and the Disturbance Storm Time (Dst) index. We show that the CME mass included in the CDAW catalog reflects with high accuracy the actual mass-loss rate from the Sun through CMEs. Additionally, it is shown that the CME mass distribution in the log-lin representation reflects the Gaussian distribution very well. This means that the CMEs included in the CDAW catalog form one coherent population of ejections that have been correctly identified. Unlike the CME occurrence rate, it turns out that the YTMLR is a very good indicator of solar activity (e.g., SSN) and space weather (e.g., Dst index) consequences. These results are very important, since the YTMLR, unlike the mass loss through solar wind, significantly depends on solar cycles.

Solar Hαexcess during Solar Cycle 24 from full-disk filtergrams of the Chromospheric Telescope

Context.The chromospheric Hαspectral line is a strong line in the spectrum of the Sun and other stars. In the stellar regime, this spectral line is already used as a powerful tracer of stellar activity. For the Sun, other tracers, such as Ca IIK, are typically used to monitor solar activity. Nonetheless, the Sun is observed constantly in Hαwith globally distributed ground-based full-disk imagers.Aims.The aim of this study is to introduce the imaging Hαexcess and deficit as tracers of solar activity and compare them to other established indicators. Furthermore, we investigate whether the active region coverage fraction or the changing Hαexcess in the active regions dominates temporal variability in solar Hαobservations.Methods.We used observations of full-disk Hαfiltergrams of the Chromospheric Telescope and morphological image processing techniques to extract the imaging Hαexcess and deficit, which were derived from the intensities above or below 10% of the median intensity in the filtergrams, respectively. These thresholds allowed us to filter for bright features (plage regions) and dark absorption features (filaments and sunspots). In addition, the thresholds were used to calculate the mean intensityImeanE/Dfor Hαexcess and deficit regions. We describe the evolution of the Hαexcess and deficit during Solar Cycle 24 and compare it to the mean intensity and other well established tracers: the relative sunspot number, the F10.7 cm radio flux, and the Mg IIindex. In particular, we tried to determine how constant the Hαexcess and number density of Hαexcess regions are between solar maximum and minimum. The number of pixels above or below the intensity thresholds were used to calculate the area coverage fraction of Hαexcess and deficit regions on the Sun, which was compared to the imaging Hαexcess and deficit and the respective mean intensities averaged for the length of one Carrington rotation. In addition, we present the Hαexcess and mean intensity variation of selected active regions during their disk passage in comparison to the number of pixels of Hαexcess regions.Results.The Hαexcess and deficit follow the behavior of the solar activity over the course of the cycle. They both peak around solar maximum, whereby the peak of the Hαdeficit is shortly after the solar maximum. Nonetheless, the correlation of the monthly averages of the Hαexcess and deficit is high with a Spearman correlation ofρ = 0.91. The Hαexcess is closely correlated to the chromospheric Mg IIindex with a correlation of 0.95. The highest correlation of the Hαdeficit is found with the F10.7 cm radio flux, with a correlation of 0.89, due to their peaks after the solar activity maximum. Furthermore, the Hαdeficit reflects the cyclic behavior of polar crown filaments and their disappearance shortly before the solar maximum. We investigated the mean intensity distribution for Hαexcess regions for solar minimum and maximum. The shape of the distributions for solar minimum and maximum is very similar, but with different amplitudes. Furthermore, we found that the area coverage fraction of Hαexcess regions and the Hαexcess are strongly correlated with an overall Spearman correlation of 0.92. The correlation between the Hαexcess and the mean intensity of Hαexcess regions is 0.75. The correlation of the area coverage fraction and the mean intensity of Hαexcess regions is in general relatively low (ρ = 0.45) and only for few active regions is this correlation above 0.7. The weak correlation between the area coverage fraction and mean intensity leaves us pessimistic that the degeneracy between these two quantities can be broken for the modeling of unresolved stellar surfaces.

Hemispheric Sunspot Number from the Madrid Astronomical Observatory for the Period 1935–1986

Long-term studies on hemispheric asymmetry can help to understand better the solar dynamo. We present the hemispheric sunspot number calculated from daily sunspot observations made at the Madrid Astronomical Observatory for the period 1935–1986 (corresponding approximately to Solar Cycles 17–21). From this data set, we also analyzed the asymmetry index and hemispheric phase shifts. We conclude that the northern hemisphere was predominant in Solar Cycles 17–20, whereas the southern hemisphere was predominant in Solar cycle 21. The strongest asymmetries are found in Solar Cycles 20 (with a relative difference between both hemispheres of 44%) and 19 (39%). A normalization of the Madrid hemispheric sunspot number was also made with respect to the sunspot number (Version 2). Our results agree with previous studies on hemispheric asymmetry around the mid-20th century and their secular trends.

The late Holocene hydroclimate variability in the Northwest Himalaya: Sedimentary clues from the Wular Lake, Kashmir Valley

• Wular Lake levels, redox conditions , and organic matter supply significantly altered over the last ∼4.2 kyr BP. • Hydroclimate varied from early wetter to relatively drier conditions and severe drought before the wet Little Ice Age. • Latitudinal migration of inter-tropical convergence zone drove seasonal precipitation turnover in Kashmir Valley. • A spatially coherent hydroclimate is found in the Northwest Himalaya during the late Holocene . This study focuses on the immensely debated pre-instrumental centennial–millennial scaled forcing of the late Holocene hydroclimate variability in the Northwest Himalaya (NWH). The Wular Lake is ideally situated close to the modern intertropical convergence zone (ITCZ) in the NWH and fed by the Jhelum River draining the vast Kashmir Valley, which receives seasonal precipitations from the Indian Summer Monsoon (ISM) and Western Disturbances (WD). In this study, size segregated lithic fractions (sand, silt, and clay) and elemental concentrations (TOC, TN, Ba, Al, Mn, and Fe) have been measured in the 14 C-AMS dated NWC sediment core collected from this lake. The continuous NWC sedimentary records reveal temporal environmental changes (water level, organic detritus supply, and redox conditions) in this open mega-lake system suggesting prevailed hydroclimate variations in the valley during the late Holocene. The captured hydroclimate variations are a wetter phase (∼4.2–3.4 cal kyr BP) followed by relatively drier conditions and extreme drought before the wet Little Ice Age (LIA). The plausible forcing seems to be the latitudinal ITCZ migration regulated seasonal precipitations from the tropical/subtropical moisture sources. The ISM to WD moisture turnover dominated winter over summer precipitations in the valley during the former warm and wet phase but unequivocally reflected during the cold and wet LIA. Additional hydroclimate control comes from permafrost ice melting episodes of a few centuries duration during high solar activity events (sunspot number ≥50). A comparison with the regional studies further indicates that NWC records capture hydroclimate signatures widespread in the NWH.

Relationship Between the Evolution of Solar Magnetic Field and Flares in Different Active Regions

Two comparative active regions, NOAA AR 11283 and AR 11654 are studied. Both active regions have big sunspot numbers, and large areas. However, AR 11283 erupted two X-class flares, AR 11654 erupted little flares. Through investigating the evolution of magnetic field, the active region with complex magnetic configuration has more possibility to create big flares. NOAA is National Oceanic and Atmospheric Administration

A Sunspot Catalog by Rafael Carrasco at the Madrid Astronomical Observatory for the Period 1931 – 1933

A sunspot catalog was published by the Madrid Astronomical Observatory from sunspot observations made by Rafael Carrasco and his assistants for the period November 1931 – December 1933. We have digitized this catalog and carried out a quality control to detect inconsistencies. We present a machine-readable version of this sunspot catalog together with an erratum list. Moreover, we compared the Madrid sunspot number and area with other reference series. We found that sunspots in the northern hemisphere were predominant during this period, confirming previous studies. We have also analyzed the group morphological typologies registered in the catalog and show a butterfly diagram drawn with this new information. A comparison with the sunspot catalog by the Royal Greenwich Observatory shows that almost all the groups included in the Carrasco’s catalog are also present in the aforementioned catalog.