Solar Activity Indices Research Articles

Trends in Parameters of the F2 Layer and the 24th Solar-Activity Cycle

Trends in foF2 are analyzed according to the data of Juliusruh and Boulder ionospheric stations to 2018. It is shown that the use of the traditional solar-activity index, F10.7, leads to an unexplainable foF2 trend if the data for the 24th solar-activity cycle are included in the analysis. It is suggested that the F10.7 index does not correctly describe the solar ultraviolet-radiation variation in that cycle. Correction of that index with the Rz (sunspot number) and Ly-α (intensity of the Lyman-alpha line in the solar spectrum) indices is performed. It is shown that reasonable values of the foF2 trends are then obtained. A similar analysis for hmF2 trends leads to the same results.

Heliospheric Modulation of GCR at Mid and High Latitudes

The variations of Galactic Cosmic Ray (GCR) as compared with the behaviour of various solar activity indices, heliospheric parameters and the geomagnetic index Ap during 1999-2015, which covers part of cycles 23 and cycle 24 have been studied. Two sets of data were considered, consisting respectively of all days of the month and the five quietest days. Neutron Monitor Stations of Moscow and Rome (mid latitude stations) and Inuvik and Oulu (High latitude stations) were employed. Cosmic Ray (CR) wave characteristics were obtained by the harmonics method. The mean, diurnal amplitude of the first, second, and third harmonics were calculated and profiled. Furthermore, correlation analysis was carried out to determine the association between parameters. Results showed that the total magnetic field BT and the sunspot number (SSN) showed the strongest association with CR in both quiet conditions and all day conditions considered. The higher harmonics showed a slightly stronger association with CR than lower harmonics. A time-lag of about 12-15 months was observed for SSN suggesting a potential for predicting CR flux, while the total magnetic field had a zero lag for all the heliospheric parameters considered.

Chaos and Periodicities in Solar Flare Index from Kandilli Observatory during 1976–2014

The Solar Flare Index is regarded as one of the most important solar indices in the field of solarterrestrial research. It has the maximum effect on Earth of all other solar activity indices and is being considered for describing the short-lived dynamo action inside the Sun. This paper attempts to study the short as well as long-term temporal fluctuations in the chromosphere region of the Sun using the Solar Flare Index. The daily Solar Flare Index for Northern, Southern Hemisphere and Total Disk are considered for a period from January 1976 to December 2014 (total 14 245 days) for chaotic as well as periodic analysis. The 0–1 test has been employed to investigate the chaotic behavior associated with the Solar Flare Index. This test revealed that the time series data is non-linear and multi-periodic in nature with deterministic chaotic features. For periodic analysis, the Raleigh Power Spectrum algorithm has been used for identifying the predominant periods within the data along with their confidence score. The well-known fundamental period of 27 days and 11 years along with their harmonics are well affirmed in our investigation with a period of 28 days and 10.77 years. The presence of 14 days and 7 days periods in this investigation states the short-lived action inside the Sun. Our investigation also demonstrates the presence of other mid-range periods including the famous Rieger type period which are very much confirming the results obtained by other authors using various solar activity indicators.

Predictive ARIMA Model for coronal index solar cyclic data

Many solar activities, e.g. sunspots, Mg II indices, coronal index of solar activity, etc., are produced by solar magnetic fields that affect both, the solar atmosphere and heliosphere, including the terrestrial environment. The atmosphere of the sun is recognized by photosphere, as a visible solar disk and layers above it: chromosphere, transition zone and corona. The nature of solar activity can be, in the emission solar corona, recognized by the coronal index of solar activity (CI). Its dataset in the period 1944–2009 will be used to test the ARIMA model. Based on the minimum AIC and BIC values, ARIMA(1,0,1) model is selected for each CI cycle and total dataset. The quality of the selected model is endorsed by (RMSE, MAPE, & FPE). The behaviour of the observed (original) CI cycle with predictive CI cycle shows a strong correlation, of more than 0.8 between actual and predictive CI cycles, which is a predictive power of ARIMA(1,0,1) model. Further model persistency estimated by Hurst exponent (smoothness) with the help of fractal dimension (complexity). All predictive CI cycles show persistence and positively correlated, the total dataset equation is given as X(t) – 0.977(t-1) = Z(t) - 0.546(t-1). • The purpose of the paper to understand the search of model for coronal index solar data. • By using of model predict the CI cycles. • Check the appropriateness of predicted cycle with original cycle by selected model. • After all persistency of the original and predictive data obtained by Hurst & fractal dimension.

Multiwave Siberian Radioheliograph

The article discusses characteristics, fundamental and applied tasks of the Siberian Radioheliograph that is developed at the ISTP SB RAS Radio Astrophysical Observatory and spectropolarimetric complex that measures the total flux of solar radio emission. The multi-wave mapping of the Sun in the microwave range is a powerful and relatively inexpensive, in comparison with space technologies, means of observing solar activity processes and diagnosing plasma parameters. All-weather monitoring of electromagnetic solar emission (in the range from meter to millimeter waves, including measurements of the solar activity index at 2.8 GHz), and at the location of other diverse diagnostic facilities of the Heliogeophysical Complex, is of particular value. Radioheliograph data is necessary to develop and implement methods of short-term forecast of solar flares, measurements of kinematics and characteristics of coronal mass ejection plasma, forecast of characteristics of fast solar wind streams.

Многоволновый Сибирский радиогелиограф

The article discusses characteristics, fundamental and applied tasks of the Siberian Radioheliograph that is developed at the ISTP SB RAS Radio Astrophysical Observatory and spectropolarimetric complex that measures the total flux of solar radio emission. The multi-wave mapping of the Sun in the microwave range is a powerful and relatively inexpensive, in comparison with space technologies, means of observing solar activity processes and diagnosing plasma parameters. All-weather monitoring of electromagnetic solar emission (in the range from meter to millimeter waves, including measurements of the solar activity index at 2.8 GHz), and at the location of other diverse diagnostic facilities of the Heliogeophysical Complex, is of particular value. Radioheliograph data is necessary to develop and implement methods of short-term forecast of solar flares, measurements of kinematics and characteristics of coronal mass ejection plasma, forecast of characteristics of fast solar wind streams.

The combined influences for solar-geomagnetic activities and the atmospheric circulation NAO on global surface temperatures

This work aims to investigate the effect of solar-geomagnetic activities on atmospheric circulation and to examine their influences on global surface temperature (GST). Used data are the sunspot number (Rz) as a solar activity index, geomagnetic activity index (aa), the North Atlantic Oscillation index (NAO), and GST. We have performed an extensive analysis by using the wavelet power spectra (WPS) and global wavelet spectra (GWS). Results from WPS showed that both NAO and GST exhibited periodicities of ~ 22 years and 11 years, indicating the imprint of solar activity on both parameters. Additionally, the WPS of NAO exhibited three dominant modes; firstly, periodicity of 2 to 4 years appeared in the time intervals: (1954–1967), (1987–1997), and (2007–2015), possibly related to El-Nino Southern Oscillation. Secondly, sporadic oscillation of 1 to 2.5 years observed during the whole period, which corresponding to quasi-biennial oscillation. Finally, oscillatory modes with high power on the band 7 to 8.5 years are observed on NAO spectrum: 7.6 years for the period (1872–1892) and 8.3 years for 1996–2005. This oscillatory mode with enhanced power in the 8.3 years has been detected significantly on the GWS of GST, indicating the influence of climatic pattern on GST. Our results showed that the solar-geomagnetic activities influence partially and indirectly on GST through atmospheric circulation pattern.

Equatorial aurora: the aurora-like airglow in the negative magnetic anomaly.

The most fantastic optical phenomena in the Earth's upper atmosphere are the auroras. They are highly informative indicators of solar activity, geomagnetic activity, upper atmospheric structures and dynamics, and magnetospheric energetic particles. An area where the geomagnetic field differs significantly from the expected symmetric dipole, such as at the South Atlantic Anomaly, where the magnetic field intensity is low, gives rise to stronger precipitation of energetic particles into the upper atmosphere. Impact excitation and the subsequent airglow emissions exhibit aurora-like dynamic signatures. Nomenclatures of nonpolar aurora or equatorial auroras are similar to those used with the polar auroras owing to their similar excitation mechanisms. This paper provides an overview of the knowledge and the challenges concerning auroral activity at the South Atlantic Anomaly, or more generally, at the negative magnetic anomaly. We emphasize systematic investigation of the equatorial auroras to reveal the temporal and spatial evolution of the magnetic anomaly and the behaviour of energetic particles in near-Earth space.

Trends in hmF2 and the 24th solar activity cycle

The measurements of the F2-layer height, hmF2, at Juliusruh station during 1958–2018 are analyzed by the method developed by the authors earlier and used to determine long-term trends in parameters of the F2 layer. It is found that, in the same way as for the behavior of the critical frequency described by the authors in the previous publication, peculiarities in the hmF2 behavior are observed after 2002–2003. If the solar activity index F10.7 is used, an increase in the ΔhmF2 value is observed and provides a positive trend in hmF2 that contradicts to the available ideas on the continuing process of cooling and contraction of the upper atmosphere. If the F10.7 index corrected by other SA indices (the sunspot number Rz or the Lyman-alpha line intensity) is used, as it has been done for the foF2 trends in the previous publications by the authors, the picture of changes in the hmF2 trends is obtained similarly to the changes in the foF2 trends. A well pronounced negative trend in hmF2 is observed to 2002–2003, and then it is substituted by a chaotic change in ΔhmF2 during the “vague” period, whereas during the last analyzed years it becomes negative again. Analysis of the slope s of the foF2(hmF2) dependence shows that there is a systematic decrease in s with time. That confirms the conclusion of the authors on a decrease in the oxygen amount in the thermosphere.

Analysis of ionospheric TEC anomalies for global earthquakes during 2000-2019 with respect to earthquake magnitude (Mw≥6.0)

In this work, a relationship between ionospheric TEC anomalies and different earthquake magnitude groups before the main shocks was investigated. For this purpose, 2942 global earthquakes with Mw≥6 from 2000 to 2019 and possible ionospheric TEC anomalies that occurred before earthquakes were examined by considering 13 different index values of space weather conditions (geomagnetic storm indices and solar activity indices). Anomalies of ionospheric TEC changes were defined for 15-days before and 4-days after the earthquakes by using 15-days moving median method with the length of 15 days. Earthquakes were first grouped according to their magnitudes, and then negative and positive TEC anomalies in quiet days before the earthquakes were detected. These anomalies were observed as ∼5–13, ∼5-10, ∼5-15, ∼3-13, ∼7-15, ∼1 and ∼5-8 days ago for the earthquakes of 6.0 ≤ Mw<6.5, 6.5 ≤ Mw<7.0, 7.0 ≤ Mw<7.5, 7.5 ≤ Mw<8.0, 8.0 ≤ Mw<8.5, 8.5 ≤ Mw<9.0, and 9.0 ≤ Mw<9.5, respectively. Mean of changes in TEC anomalies of these groups is 44.2 % TECU and we detected that the number of positive anomalies in each group is larger than the number of negative anomalies. Consequently, these analyses clearly show that the day-to-day changes in TEC anomalies may supply significant precursors prior to the global earthquakes (M ≥ 6) in the short-term earthquake prediction for main shocks.

Estimation of Solar Activity Impact on the Outgoing Infrared-Radiation Flux

A parameterization of the mechanism of solar activity impact on the Earth’s troposphere developed by the authors is proposed for a model of outgoing longwave radiation, based on the integral transmission function. The PC-index of geomagnetic activity, which was developed to monitor the polar cap magnetic activity and reflects the affect of the interplanetary electric field on the magnetosphere, was used as the indicator of solar activity. Based on data from NCEP/NCAR reanalysis, we calculated. The integrated transmission function and outgoing longwave flux for periods of increased and decreased solar activity. Correlation analysis of the calculated radiation characteristics with temperature in the 925- to 700-hPa layer showed that the inclusion of solar activity leads to higher correlation between the radiation characteristics and temperature. Comparison of the calculation results with temperature changes confirmed that the proposed parameterization can be used to include impacts of solar activity in numerical models with the integral transmission function to calculate outgoing longwave radiation.

Periodic variation and phase analysis of grouped solar flare with sunspot activity

Studies on the periodic variation and the phase relationship between different solar activity indicators are useful for understanding the long-term evolution of solar activity cycles. Here we report the statistical analysis of grouped solar flare (GSF) and sunspot number (SN) during the time interval from January 1965 to March 2009. We find that, (1) the significant periodicities of both GSF and SN are related to the differential rotation periodicity, the quasi-biennial oscillation (QBO), and the eleven-year Schwabe cycle (ESC), but the specific values are not absolutely identical; (2) the ESC signal of GSF lags behind that of SN with an average of 7.8 months during the considered time interval, which implies that the systematic phase delays between GSF and SN originate from the inter-solar-cycle signal. Our results may provide evidence about the storage of magnetic energy in the corona.

A Prediction of Solar Activity Indicator F10.7 using LSTM Network

A Prediction of Solar Activity Indicator F10.7 using LSTM Network

STUDY OF THE RELATIONSHIP BETWEEN HELIOGEOPHYSICAL FACTORS AND THE COURSE OF CERTAIN PHYSIOLOGICAL PROCESSES IN INDIVIDUALS WITH DIFFERENT PSYCHOSOMATIC STATUS AS A COMPONENT OF PSYCHOLOGICAL SUPPORT

Тhe purpose of the study: to establish a correlation between the average annual values of the minute volume of blood flow in hypertensive men with different temperaments and high anxiety and solar activity. There were 848 patients with arterial hypertension and 422 healthy individuals. All of them were determined by temperament and anxiety, and the minute volume of blood flow. To compare the calculated method for determining the minute volume of blood flow with the hardware method, the authors measured the minute volume of blood flow in patients using tetrapolar rheography on a 6-NEG device connected with a computer and compared it with the value of the minute volume of blood flow determined by calculation. Data on the dynamics of solar activity in wolf numbers and radio emission at a wavelength of 10.5 cm were obtained from the West-Siberian Department for Hydrometeorology and Environmental Monitoring. During the period of increased solar activity, the body was affected by a complex of factors, including socio-economic factors, together with ionizing radiation of the environment; contribute to a decrease in the coefficient of oxygen utilization by tissues, which caused the development of an adaptive reaction, part of which was an increase in the minute volume of blood flow. A significant correlation was established between solar activity indicators, meteorological factors, and minute blood flow volume, which indicates the possibility of a combined effect of the studied factors on increasing the functional activity of the cardiovascular system.

The 10.7‐cm radio flux multistep forecasting based on empirical mode decomposition and back propagation neural network

The 10.7‐cm solar radio flux (F10.7) is among the most widely used indices of solar activity, whose prediction plays a vital role in the field of meteorology and aerospace. In this paper, a novel approach for a specific amalgamation of back propagation neural network (BPNN) and empirical mode decomposition (EMD) is proposed, which is called EMD‐BP, aimed at forecasting the daily F10.7 values 1–27 days ahead. The daily F10.7 values, which are highly nonlinear and unstable time series, are transformed into a series of subsignals with different frequency components by EMD and trained by the BPNN. For estimating the performance of the description EMD‐BP, the support vector regression (SVR), Long Short‐Term Memory neural network and BPNN as the reference models are analyzed in different conditions. The results indicate that the proposed model improves the F10.7 forecasting within 27 days, compared with the common machine learning algorithms and transport model. Furthermore, a tremendous decline of forecast error is determined in high‐level solar activity, in contrast with SVR and BPNN. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

On the Radiative Relaxation Time for the Hydrogen–Helium Atmosphere Estimated from Changes in the Activity Factor of Jupiter’s Hemispheres

The subsolar point on Jupiter’s magnetosphere changes its position by an angle of approximately 26° over the orbital period of Jupiter, which induces seasonal variations in physical and optical characteristics of the planetary atmosphere. At the time close to the summer solstice for the northern hemisphere, Jupiter is in perihelion. Consequently, due to the significant orbital eccentricity, the energy influx into the atmosphere in the northern hemisphere is 21% larger than that in the southern one. This leads to the asymmetry in the meridional distribution of the reflectance of visible clouds. Analysis of the results of photometric observations of Jupiter for 1960–2019 showed that the ratio AJ = BN/BS adequately describes the activity of atmospheric processes on Jupiter, which shows periodic increases in brightness at tropical and temperate latitudes in the southern and northern regions by turn during one orbital period of Jupiter. The response of the atmosphere to changes in the irradiation by the Sun does not occur instantaneously but with some delay. The results of observations of Jupiter in the visible range in 1960–1995 and 2012–2019 show a synchronous delay of 3.4 year (τR ≈ 1.07 × 108 s) in response to the 21% change in the irradiation of different hemispheres when the planet is orbiting the Sun. In 1995–2012, the discrepancy caused by the orbital motion of the planet was observed between the behavior of AJ, the solar activity index Sn, and Jupiter’s regime of exposure to the Sun. Variations associated with the influence of solar activity are mainly induced by significant changes in the ultraviolet radiation of the Sun. These changes first affect the energetics of the upper atmosphere of Jupiter, after which they are indirectly transmitted into the troposphere, sometimes reducing the value of the relaxation constant τR to ~2.5 years. Since 2012, the behavior of the time dependence of AJ, the index of solar activity, and the irradiation regime of Jupiter due to its orbital motion have become consistent again. The periodicity in changes of the photometric characteristics of the northern and southern hemispheres of Jupiter were also restored.

Investigation of the coronal heating through phase relation of solar activity indexes

Abstract The coronal heating problem is a long-standing perplexing issue. In this study, 13 solar activity indexes are used to investigate their phase relation with the sunspot number (SSN). Only three of them are found to statistically significantly lag the SSN (large-scale magnetic activity) by about one solar rotation period; the three indexes are total solar irradiance (TSI), the modified coronal index, and the solar wind velocity; the former two indexes may represent the long-term variation of energy quantity of the heated photosphere and corona, respectively. The Mount Wilson Sunspot Index (MWSI) and the Magnetic Plage Strength Index (MPSI), which reflect the large- and small-scale magnetic field activities, respectively, are also utilised to investigate their phase relations with the three indexes. The three indexes are found to be much more intimately related to MPSI than to MWSI, and MWSI statistically significantly leads TSI by about one rotation period. The heated corona is found to pulse perfectly in step with the small-scale magnetic activity rather than the large-scale magnetic activity; furthermore, combined with observations, our statistical evidence should thus attribute coronal heating firmly to small-scale magnetic activity phenomena, such as spicules, micro-flares, nano-flares, and others. The photosphere and the corona are synchronously heated, which should seemingly prefer magnetic reconnection heating to wave heating. In the long term, such a coronal heating way is inferred effective. Statistically, it is also small-scale magnetic activity phenomena that produce TSI enhancement. Coronal heating and solar wind acceleration are found to be synchronous, as standard models require.

Solar Activity Indices for Ionospheric Parameters in the 23rd and 24th Cycles

Characteristics of changes in the solar activity indices (the flux of the solar radio emission at a wavelength of 10.7 cm F and the new version of the relative sunspot number Ri) and the ionospheric index of this activity T in the 23rd and 24th solar cycles, which were low by the amplitude of solar and geomagnetic activity, are analyzed. The running mean over 12 months and smoothed (by a 24-month filter) values of these indices are considered in the analysis. It is found that the relation between the T and F indices was on average stable for these cycles and did not differ from the previous solar cycles. The relation between the T and Ri indices changed with time in the 23rd and 24th cycles and was different from the previous cycles. Moreover, a distinct hysteresis effect in the dependence of the smoothed values of T on Ri was observed in the 24th cycle when different values of T corresponded to a fixed value of Ri in the growing and declining phases of the solar cycle. This effect was absent in the dependence of T on F. Thus, it is confirmed that the F index is a more exact indicator of solar activity for the ionosphere than Ri.

Response of IAR frequency scale to solar and geomagnetic activity in solar cycle 24

The ionospheric Alfven resonator (IAR) is an integral element of the entire ionosphere-magnetosphere system. It plays an essential role in energy exchange and interaction between the magnetosphere and ionosphere. The parameters of this resonator reflect the state of the ionosphere. The purpose of this study was to study three types of IAR frequency modulation (daily, seasonal and solar-cyclic) and to identify their relationship with solar and magnetic activity. We used the results of magnetic observations of the IAR emission at the Mondy mid-latitude observatory for the 24th solar activity cycle from 2009 to 2019. The dependence of the difference in the neighboring harmonics frequencies (i.e., the emission frequency scale) on solar activity (the sunspot number) and on the magnetic indices Kp, Dst and AE was studied. The correlation between the frequency scale and the indices of solar and magnetic activity was investigated at different time scales by comparing the variations in daily, monthly, and annual averages. The dependence of the IAR frequency scale on solar activity turns out to be much closer than the same dependence of any of the three magnetic indices. The closest relationship is exhibited between the annual average values of the frequency scale, on the one hand, and the sunspot number and the Dst index, on the other. This result is interpreted as a demonstration of the cumulative effect of solar activity on the state of the ionosphere and, first of all, on the electron concentration in the F2 region of the ionosphere.

Relationship between the Northern Hemisphere Sea Ice Area and Global Temperature by Multifractal Analysis

Changes in Arctic sea ice are an important fingerprint of natural and anthropogenic climate change. In general, fractal properties may be observed in the time series of the dynamics of complex systems. To study the relations among the Northern Hemisphere (NH) sea ice area, solar activity, global temperature, and Pacific Decadal Oscillation (PDO) index, we investigated changes in the fractal behavior of these time series by multifractal analysis and applying the wavelet coherence. The relationship between the solar activity: solar flux, sunspot number (SSN), and ultraviolet B (UV-B), and NH sea ice area was assessed based on changes in fractality. We identified the existing relations among the NH sea ice area, global temperature, and PDO based on changes in fractality and wavelet coherence. In the 2000s when the global warming hiatus occurred, after the order formation of NH sea ice area in the early 2000s, the change in state from multifractal to monofractal of the PDO and global temperature occurred, when fluctuations became large and multifractality became strong. We identified a small change in fractality for NH sea ice area, UV-B, and global temperature and a large change in fractality for solar flux, SSN, and PDO, which had large fluctuation. Our results will contribute to further studies on climate change.