Measure Of Solar Activity Research Articles

Comparison of different predictive models and their effectiveness in sunspot number prediction

Human activities and health are significantly influenced by solar activity. The sunspot number is one of the most commonly used measures of solar activity. The solar cycle’s quasi-periodic nature makes it an excellent choice for time series forecasting. Four models include three singular models, consisting of Long Short-Term Memory (LSTM), AutoRegressive Integrated Moving Average (ARIMA), and Seasonal AutoRegressive Integrated Moving Average (SARIMA), as well as a hybrid model were implemented to forecast maximum sunspot number of cycles 25 and 26. The hyperparameters of the singular models were optimized using Bayesian optimization. The LSTM-ARIMA hybrid model was able to achieve the best performance. The outstanding results of the LSTM-ARIMA model shows the potential of hybrid methods in improving the overall performance. Moreover, the LSTM model was able to outperform the ARIMA model, which demonstrates the ability of LSTM networks in learning from time-series data. The final model forecasts a peak sunspot number of 137.04 for Solar Cycle 25 in September 2024 and 164.3 for Solar Cycle 26 in December 2034, which is comparable to the National Aeronautics and Space Administration’s (NASA) prediction of 134.4 in October 2024 and 161.2 in December 2034.

Taxonomic diversity and structure of phytoplankton in different-type lakes of Kulunda basin (Altai krai)

In the phytoplankton of different-type lakes of Kulunda basin 87 species and 1 variety of algae from 6 systematic divisions were identified: Cyanobacteria, Bacillariophyta, Cryptophyta, Euglenophyta, Chlorophyta and Ochrophyta. The most diverse in the number of families, genera and species is the Cyanobacteria (35 species, or 40.2 % of the total number of species), as well as Chlorophyta (26, or 29.9 %), Bacillariophyta (17, or 19.5 %). Most of the taxa ranked above the family belong to Bacillariophyta (2 classes, 3 subclasses, 9 orders) and Chlorophyta (3 classes, 8 orders). The two divisions are not numerous, they have only 2 (Cryptophyta) and 3 (Ochrophyta) species. The largest family is Oscillatori-aceae with 4 genera and 13 species. The leading genera include 5 genera, and 3 of them are from Cyanobacteria, 1 genus each belong to Chlorophyta (Ulothrix) and Bacillariophyta (Nitzschia). According to the results of the study, the dependence of the number of species in phytoplankton on the average mineralization and Wolf Number (the measure of solar activity) for salt lakes in Kulunda basin was revealed.

The Effect of Solar Activity on Stratospheric Temperature Over Iraq for Period 1948-2014

Stratospheric temperature changes are very important for climate systems through atmospheric circulation and stratosphere-troposphere coupling. The relationship between solar modulation potential SMP as a measure of solar activity and variation of temperature in upper, middle and lower stratosphere over Iraq for the period 1948-2014 (for about five solar cycles) has been presented in this study. For upper, middle and lower stratosphere we found that stratospheric temperatures decreased, this descending trend is offset by obviously descending trend in solar activity for the same period. The correlation coefficients between annual solar modulation potential SMP and stratospheric temperature have been examined at pressure levels (10,20,30,50,70 mb) that represent the upper, middle and lower stratosphere over 67 years (1948 to 2014). All levels have positive correlation. The correlation coefficient (R) in upper stratosphere at level 10 mb has been 0.4, in middle stratosphere at level (20, 30 mb) the correlation coefficient (R) has been 5.3 and 0.6 respectively. For lower stratosphere at level (50, 70 mb) R has been 0.57 and 0.68 respectively.

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.

Earth's Albedo 1998–2017 as Measured From Earthshine

AbstractThe reflectance of the Earth is a fundamental climate parameter that we measured from Big Bear Solar Observatory between 1998 and 2017 by observing the earthshine using modern photometric techniques to precisely determine daily, monthly, seasonal, yearly and decadal changes in terrestrial albedo from earthshine. We find the inter‐annual fluctuations in albedo to be global, while the large variations in albedo within individual nights and seasonal wanderings tend to average out over each year. We measure a gradual, but climatologically significant 0.5 decline in the global albedo over the two decades of data. We found no correlation between the changes in the terrestrial albedo and measures of solar activity. The inter‐annual pattern of earthshine fluctuations are in good agreement with those measured by CERES (data began in 2001) even though the satellite observations are sensitive to retroflected light while earthshine is sensitive to wide‐angle reflectivity. The CERES decline is about twice that of earthshine.

Variability of the African equatorial ionization anomaly (EIA) crests during the year 2013

This paper discusses the variability of the position and magnitude of the crests of African Equatorial Ionization Anomaly during noon and post sunset periods. Total electron content data covered the year 2013, and were obtained from a chain of global positioning system receivers in both hemispheres around 37°E longitude. Local magnetometer data were used to infer the direction and magnitude of the E × B drift, while the solar extreme ultraviolet proxy index was used as a measure of solar activity. It was found that the time of formation of both crests varied from 1400 to 1700 local time. Additionally, the position of the crests was found to be asymmetric with respect to the magnetic equator. During the noon period, the position of the northern and southern crests varied from 4.91° to 7.36° and −9.17° to −12.62°, respectively. During the post-sunset period, it varied from 8° to 11.7° and −9° to −16°, respectively. Seasonally, with reference to the magnetic equator, both crests moved poleward during equinoxes and collapsed towards the equator during winter and summer. Equinoxes recorded the greatest crest magnitude followed by winter then summer over both hemispheres during the noon period. However, this trend persisted over the northern crest only during the post-sunset period. Overall, during the noon period, we recorded correlation coefficients of 0.67 and 0.68 between crest magnitudes and ΔH, a proxy for equatorial electrojet current, and 0.88 and 0.81 between crest positions and ΔH, for the northern and southern crests, respectively. During the Halloween day storm of 30 October 2013, a westward electric field inhibited the development of the post-sunset crests.

Flood sensitivity of the Bavarian Alpine Foreland since the late Middle Ages in the context of internal and external climate forcing factors

Abstract. This paper describes the flood sensitivity of the Bavarian part of the Alpine Foreland of Germany and addresses different questions concerning climate variability and flood frequencies, from the 14th century until today. The focal point of the paper is the flood frequency of the superordinate spatial unit of the Bavarian Foreland. Based on written historical sources, the flood history of the Alpine Foreland of Germany can be reconstructed back to the 14th century. One major result is the occurrence of "flood-rich" and "flood-poor" episodes in almost cyclical sequences. Flood-rich periods, before the 16th century based on limited available data, were recorded in the periods 1300–1335, 1370–1450, 1470–1525, 1555–1590, 1615–1665, 1730–1780, 1820–1870, and 1910–1955 as well as in a ninth period beginning in 1980. The flood-rich periods are characterized by longer flood duration. Most of the flood-rich and flood-poor periods (in particular the beginning and the end of them) can be connected to changes in natural climate variability. These include changing sunspot numbers (as a measure of solar activity), so-called Little Ice Age type events (LIATEs) as well as changes in the North Atlantic Oscillation (NAO). Climate signals from external forcing factors, which could be used to explain the changing flood frequencies in the Bavarian Alpine Foreland, end in 1930. Relationships within the climate system such as the correlation of flood frequencies with the NAO have changed during the transition from the post Little Ice Age period to the Modern Climate Optimum around 1930. Natural climate variability might have been overlaid by anthropogenic climate change.

Investigating a solar influence on cloud cover using the North American Regional Reanalysis data

The controversial connection between cosmic rays, solar activity, and cloud cover is investigated using a climatological reconstructed reanalysis product: the North American Regional Reanalysis which provides high-resolution, low, mid-level, high, and total cloud cover data over a Lambert conformal conic projection permitting land/ocean discrimination. Pearson’s product-moment regional correlations were obtained between monthly cloud cover data and solar variability indicators, cosmic ray neutron monitors, several climatological indices, including the Atlantic Multidecadal Oscillation (AMO), and between cloud layers. Regions of the mid-latitude oceans exhibited a positive correlation with cosmic ray flux. Additionally, this maritime low cloud cover exhibits the only failed correlation significance with other altitudes. The cross correlation reveals that cloud cover is positively correlated everywhere but for ocean low cloud cover, supporting the unique response of the marine layer. The results of this investigation suggest that with the assumption that solar forcing does impact cloud cover, measurements of solar activity exhibits a slightly higher correlation than GCRs. The only instance where GCRs exhibit a positive regional correlation with cloud cover is for maritime low clouds. The AMO exerts the greatest control of cloud cover in the NARR domain.

Is Intracranial Aneurysm Rupture Related to Solar Activity?

Objective: A number of intrinsic and extrinsic risk factors for the rupture of intracranial aneurysms have been identified. Still, the cause precipitating aneurysm rupture remains unknown in many cases. In addition, it has been observed that aneurysm ruptures are clustered in time but the trigger mechanism remains obscure. As solar activity has been associated with cardiovascular mortality and morbidity we decided to study ist association to aneurysm rupture in the Swiss population. Method: Patient data was extracted from the Swiss SOS database, at time of analysis covering 918 patients with angiography-proven aSAH treated at seven Swiss neurovascular centers between 01/01/2009 – 12/31/2011. The number of aneurysm rupture per day, week, month (Daily/Weekly/Monthly Rupture Frequency = RF) was measured and correlated to the absolute amount and the change in various parameters of interest representing continuous measurements of solar activity (radioflux (F10.7 index), solar proton flux, solar flare occurrence, planetary K-index/planetary A-index) using Poisson regression analysis. Results: Of a consecutive series of 918 cases of SAH, precise determination of the date of symptom onset was possible in 816 (88.9%). During the period of interest there were 517 days without recorded aneurysm rupture. There were 398, 139, 27 and 12 days with 1, 2, 3, and 4 ruptures per day. Five or 6 ruptures were only noted on a single day each. Poisson regression analysis demonstrated a significant correlation of F10.7 index and aneurysm rupture (incidence rate ratio (IRR) = 1.006303; standard error (SE) 0.0013201; 95% confidence interval (CI) 1.003719 – 1.008894; p<0.001), according to which every 1-unit increase of the F10.7 index increased the count for an aneurysm to rupture by 0.63%. As the F10.7 index is known to correlate well with the Space Environment Services Center (SESC) sunspot number, we performed additional analyses on SESC sunspot number and sunspot area. Here, a likewise statistically significant relationship of both the SESC sunspot number (IRR 1.003413; SE 0.0007913; 95%CI 1.001864 – 1.004965; p<0.001) and the sunspot area (IRR 1.000419; SE 0.0000866; 95%CI 1.000249 – 1.000589; p<0.001) emerged. All other variables analyzed showed no correlation with RF. Conclusions: Using valid methods, we found higher radioflux, sunspot number and sunspot area to be associated with an increased count of aneurysm rupture. Since we were using rupture frequencies rather than incidences and because we cannot explain the physiological basis of this statistical association, the clinical meaningfulness of this statistical association must be interpreted carefully. Future studies are warranted to rule out a type-1 error.

Cycle 23 Variation in Solar Flare Productivity

The NOAA listings of solar flares in cycles 21-24, including the GOES soft X-ray magnitudes, enable a simple determination of the number of flares each flaring active region produces over its lifetime. We have studied this measure of flare productivity over the interval 1975-2012. The annual averages of flare productivity remained approximately constant during cycles 21 and 22, at about two reported M or X flares per region, but then increased significantly in the declining phase of cycle 23 (the years 2004-2005). We have confirmed this by using the independent RHESSI flare catalog to check the NOAA events listings where possible. We note that this measure of solar activity does not correlate with the solar cycle. The anomalous peak in flare productivity immediately preceded the long solar minimum between cycles 23 and 24.

Evolution of Solar and Geomagnetic Activity Indices, and Their Relationship: 1960 – 2001

We employ annually averaged solar and geomagnetic activity indices for the period 1960 – 2001 to analyze the relationship between different measures of solar activity as well as the relationship between solar activity and various aspects of geomagnetic activity. In particular, to quantify the solar activity we use the sunspot number Rs, group sunspot number Rg, cumulative sunspot area Cum, solar radio flux F10.7, and interplanetary magnetic field strength IMF. For the geomagnetic activity we employ global indices Ap, Dst and Dcx, as well as the regional geomagnetic index RES, specifically estimated for the European region. In the paper we present the relative evolution of these indices and quantify the correlations between them. Variations have been found in: i) time lag between the solar and geomagnetic indices; ii) relative amplitude of the geomagnetic and solar activity peaks; iii) dual-peak distribution in some of solar and geomagnetic indices. The behavior of geomagnetic indices is correlated the best with IMF variations. Interestingly, among geomagnetic indices, RES shows the highest degree of correlation with solar indices.

A survey of gradual solar energetic particle events

[1] We develop a database of 110 gradual solar energetic particle (SEP) events, over the period 1967–2006, providing estimates of event onset, duration, fluence, and peak flux for protons of energy E > 60 MeV. The database is established mainly from the energetic proton flux data distributed in the OMNI 2 data set; however, we also utilize the McMurdo neutron monitor and the energetic proton flux from GOES missions. To aid the development of the gradual SEP database, we establish a method with which the homogeneity of the energetic proton flux record is improved. A comparison between other SEP databases and the database developed here is presented which discusses the different algorithms used to define an event. Furthermore, we investigate the variation of gradual SEP occurrence and fluence with solar cycle phase, sunspot number (SSN), and interplanetary magnetic field intensity (Bmag) over solar cycles 20–23. We find that the occurrence and fluence of SEP events vary with the solar cycle phase. Correspondingly, we find a positive correlation between SEP occurrence and solar activity as determined by SSN and Bmag, while the mean fluence in individual events decreases with the same measures of solar activity. Therefore, although the number of events decreases when solar activity is low, the events that do occur at such times have higher fluence. Thus, large events such as the “Carrington flare” may be more likely at lower levels of solar activity. These results are discussed in the context of other similar investigations.

Enhanced signature of solar variability in Eurasian winter climate

We demonstrate that open solar flux (Fs, derivable from geomagnetic data) exhibits stronger correlations with atmospheric circulation variations than conventionally‐used measures of solar activity. The circulation anomalies are particularly enhanced over the North Atlantic/Eurasian sector, where there are large changes in the occurrence of blocking and the winter mean surface temperature differs by several degrees between high‐ and low‐solar terciles. The relationship is stronger and simpler for Fs, being more linear between high‐ and low‐solar winters. While the circulation anomalies strongly resemble the North Atlantic Oscillation they also extend deeper into Eurasia, especially in high‐solar conditions. This distinct signature may be useful for the detection and attribution of observed changes and also the identification of dynamical mechanisms.

The Sun's X‐ray Emission During the Recent Solar Minimum

The Sun recently underwent a period of a remarkable lack of major activity such as large flares and sunspots, without equal since the advent of the space age a half century ago. A widely used measure of solar activity is the amount of solar soft X‐ray emission, but until recently this has been below the threshold of the X‐ray‐monitoring Geostationary Operational Environmental Satellites (GOES). There is thus an urgent need for more sensitive instrumentation to record solar X‐ray emission in this range.Anticipating this need, a highly sensitive spectrophotometer called Solar Photometer in X‐rays (SphinX) was included in the solar telescope/spectrometer TESIS instrument package on the third spacecraft in Russia's Complex Orbital Observations Near‐Earth of Activity of the Sun (CORONAS‐PHOTON) program, launched 30 January 2009 into a near‐polar orbit. SphinX measures X‐rays in a band similar to the GOES longer‐wavelength channel.

A New Setup for Ground‐based Measurements of Solar Activity at 10 μm

ABSTRACTSolar activity measurements in the far‐ to mid‐IR range are receiving renewed interest as part of an effort to complement recent results obtained at submillimeter wavelengths. A new setup has been developed to measure solar activity in the infrared spectral region centered at 10 μm (30 THz) by means of a camera with focal plane array of uncooled microbolometers. An optical arrangement of concave‐convex‐concave mirrors magnifies and focuses the full‐disk solar image to fit into the field of view of the camera. Techniques were developed to characterize the camera and calibrate the measurements in brightness temperature and flux units. Test observations were made at the Bernard Lyot Solar Observatory, Campinas, Brazil, and were continued at El Leoncito Astronomical Complex, San Juan, Argentina. The sky was found to be almost transparent at 10 μm at both sites. The first measurements of the solar disk have confirmed the presence of quiescent bright ring, or “plagelike,” regions around sunspots, and “disappearances” of sunspots coincident with small soft X‐ray bursts. Small mid‐IR flares were found, consisting of multiple rapid brightenings (tens of seconds to several minutes) at different locations in the solar active regions, corresponding to soft X‐ray bursts reported by GOES satellites. At a wavelength of 10 μm, the sizes of some flare sources were found to be smaller than the diffraction‐limited photometric beam of 25″ set by the 10.5 cm diameter objective lens. The intensities of such small mid‐IR flares were high, of the order of (8–14) × 10−19 W m−2 Hz−1 (or [8–14] × 104 solar flux units).

Flare index variability in the ascending branch of solar cycle 23

A brief description and the results of the determination of the flare index as a measure of solar activity on the ascending branch of cycle 23 up to 31 December 2000 are presented. The patterns of similar activity indices that arise under different physical conditions during the rising activity phase are compared with the flare index. All studied solar indices rise more slowly in the current cycle than the last one, except the total solar irradiance. The intermediate‐term periodicities in the daily flare index data were studied using the Fourier transform, and it was found that the 35‐, 62‐, 116‐, 198‐, and 276‐day periodicities are in operation during the ascending branch of cycle 23. Contrary to the previous three cycles, 155‐, 73‐, or 51‐day periodicities were not detected by the Fourier transform in this branch of the cycle. The wavelet transform results show that the occurrence of flare index power is highly intermittent in time, and the most pronounced power peaks were found to be present at 35 days (the temporal locations at 1998.3, 1999.9, and 2000.5 years), 116 days (the temporal interval 1999.7–2000.4 years) and 276 days period (interval roughly from 1999.5 until the end of the flare index data). Comparison of the Fourier and wavelet transform results has clarified the importance of different periodicities, whether they are (62, 198 days) or are not (35, 116, 276 days) the harmonics of the basic ones, as well as the temporal location of their occurrence.

A new pattern for the north–south asymmetry of sunspots

We study the solar cycle evolution during the last 8 solar cycles using a vectorial sunspot area called the LA (longitudinal asymmetry) parameter. This is a useful measure of solar activity in which the stochastic, longitudinally evenly distributed sunspot activity is reduced and which therefore emphasizes the more systematic, longitudinally asymmetric sunspot activity. Interesting differences are found between the LA parameter and the more conventional sunspot activity indices like the (scalar) sunspot area and the sunspot number. E.g., cycle 19 is not the highest cycle according to LA. We have calculated the separate LA parameters for the northern and southern hemisphere and found a systematic dipolar-type oscillation in the dominating hemisphere during high solar activity times which is reproduced from cycle to cycle. We have analyzed this oscillation during cycles 16–22 by a superposed epoch method using the date of magnetic reversal in the southern hemisphere as the zero epoch time. According to our analysis, the oscillation starts by an excess of the northern LA value in the ascending phase of the solar cycle which lasts for about 2.3 years. Soon after the maximum northern dominance, the southern hemisphere starts dominating, reaching its minimum some 1.2–1.7 years later. The period of southern dominance lasts for about 1.6 years and ends, on an average, slightly before the end of magnetic reversal.

Pioneer Venus Orbiter observations of a solar wind quasi‐invariant

The recently suggested solar wind quasi‐invariant [QI≡( B²/8π)/(ρυ²/2)] is a combination of magnetic field strength B, plasma density ρ and solar wind speed υ. Measured in the solar wind near the Earth, the median value of QI was shown to be a reliable index of solar activity for the 28 year period holding a linear relation with sunspot numbers (SSN) with a high correlation coefficient (cc) of 0.98 [Osherovich, Fainberg and Stone, 1999]. Here, using hourly data from the Pioneer Venus Orbiter for the period from 1978–1988, we demonstrate that QI near Venus also closely follow SSN with a correlation coefficient of 0.94 for the yearly mean values. We found that the calibration coefficient between QIVenus and QIEarth is slightly larger than unity, namely, QIVenus=a* · QIEarth where a*=1.134±0.001. We suggest that, for any point in the heliosphere, QI can be viewed as a useful measure of solar activity.

FLARE INDEX DURING THE RISING PHASE OF SOLAR CYCLE 23

A brief description and results of the flare index (FI) as a measure of solar activity for cycle 23 are given. The calculation of the daily flare index was determined using the final solar flare tables from the National Geophysical Data Center A. The final data of FI are presented in graphical form over the rising activity phase of solar cycle 23. Daily calculated values are available for general use in Kandilli observatory's and NGDC's anonymous ftp servers. The pattern of similar activity indices that arise under different physical conditions during the rising activity phase are compared with the flare index. The north-south asymmetry in the daily flare index data was studied.

The NOAA Mg II core‐to‐wing solar index: Construction of a 20‐year time series of chromospheric variability from multiple satellites

The Mg II core‐to‐wing ratio is a measure of the amplitude of the chromospheric Mg II ion emission at 280 nm. It has been shown to have strong correlation with solar UV (150 – 400 nm) irradiance and other measures of solar activity and is relatively insensitive to errors introduced by variations in instrument sensitivity. For these reasons, the Mg II core‐to‐wing ratio has been used as a proxy for solar activity. Observations of the Mg II ratio started with the Solar Backscattered Ultraviolet spectrograph (SBUV) instrument on the Nimbus 7 spacecraft in November 1978. Since then, SBUV and SBUV2 instruments have flown regularly on the NOAA series of polar orbiting spacecraft, providing a nearly continuous set of daily solar observations. Measurements of the solar UV irradiance made from NOAA satellites ended in February 1998 when the NOAA9 satellite failed. Because it had been operating for nearly 12 years (at least 7 years beyond its expected lifetime), the NOAA 9 SBUV2 showed significant degradation near the end of its life. The most recent data required significantly more attention to extract the Mg II core‐to‐wing ratio. There have also been data gaps that require the augmentation of data from other sources. In particular, data from the UARS Solar Stellar Irradiance Comparison Experiment (SOLSTICE) instrument was used to bridge a 5 month gap in 1995. In this report we combine data from four different instruments to create the longest and most complete record of the Mg II core‐to‐wing ratio to date. We describe a modified analysis procedure that has allowed us to extend the Mg II index up to the beginning of 1998. Finally, we compare the time series of the Mg II ratio to similar measurements from the Solar Ultraviolet Spectral Irrandiance Monitor (SUSIM) instrument to determine the quality of the NOAA Mg II core‐to‐wing data set.