22nd Solar Cycle Research Articles

Solar coronal rotation according to soft X-ray solar radiation during the 22nd, 23rd, and 24th solar cycles

Using the developed method of combining numerous scattered time series of the same type of measurements into a single weighted average series, according to the data of the GOES series satellites, a single series of daily data was synthesized during the 22nd, 23rd and 24th solar cycles (1986 – 2019 years). The flare and background components were distinguished from this data series, which were investigated by means the method of constructing a composite spectral periodogram for the presence of quasiperiodic oscillations at various solar cycles. Some of these found quasiperiods may be explained by both synodic and sidereal rotation of the Sun, while others coincide with the average lifetime of the solar atmosphere active formations such as the sunspot groups and the facular plages. Special attention was paid to the study of the change over time the revealed quasiperiodic values over the course of solar cycles by calculating the sample normalized spectral density of the analyzed data in a sliding time window with a value of up to two years. Based on the revealed quasiperiodic value changes presented on the dynamic diagrams, it can be concluded that the differential rotation of the solar corona is unstable and manifests itself only at certain stages of the development and existence of solar activity cycles.

Comparative Analysis of Fractal Properties of Solar Faculae

Present study is aimed at investigating the solar faculae area from 1990 to 2007 which partially covered the 22nd and 23rd solar cycle. Rescaled Range Analysis (RRA) and Detrended Fluctuation Analysis (DFA) have been adopted to evaluate the behaviour of nonlinear dynamics of solar faculae area. Results show that the value of Hurst exponent for solar faculae area from RRA and DFA is negatively correlated. It means it is non-persistent and long-range correlated. Obtained result is inaccurate so the only solution is to transform the data into stationary data by taking differencing. RRA is applied on residuals and RRA to evaluate the fractal property of the time series. Solar faculae area investigated in this study is fractal in nature and predictable ass well. Moreover, the time series of solar faculae area is non-linear as established by the Brock – Dechert – Scheinkman (BDS) test results.

The Responses of Ionospheric Conductivities on the Mid-Latitudes to Changes in the BZ Component of Interplanetary Magnetic Field

In this study, we investigate the response of the ionospheric conductivities on the middle latitudes to the southward and northward turnings of the BZ component of the interplanetary magnetic field (IMF). For this purpose, parallel conductivity (σ0), Pedersen conductivity (σ1), Hall conductivity (σ2) data calculated for Rome (41.8° N, 12.5° E); Juliusruh (54.6° N, 13.4° E); Uppsala (59.8° N, 17.6° E); Lycksele (64.7° N, 18.8° E) during the 22nd solar cycle are examined. The superposed epoch analysis method is used to investigate the response of the conductivities to the southward and northward turnings of the BZ component. From the analysis results it is observed that the turnings in the BZ component of the IMF have significant effect on all conductivities. At the event moment (zero time), the southward turnings of the BZ component increases all conductivities while the northward turnings of the BZ component decreases all conductivities. The effect on the conductivities of the changes in the BZ component occurs before about 18 h from the event moment, and this effect disappears after about 24 h from the event moment. Furthermore, all of ionospheric conductivities shows or does less reaction to changes in the BZ component as latitude increase.

Correlation between sunspots and interplanetary shocks measured by ACE during 1998–2014 and some estimations for the 22nd solar cycle and the years between 2015 and 2018 with artificial neural network using the Cavus 2013 model

The Advanced Composition Explorer (ACE) spacecraft has measured 235 solar-based interplanetary (IP) shock waves between the years of 1998–2014. These were composed of 203 fast forward (FF), 6 slow forward (SF), 21 fast reverse (FR) and 5 slow reverse (SR) type shocks. These data can be obtained from the Interplanetary Shock Database of Harvard-Smithsonian Centre for Astrophysics. The Solar Section of American Association of Variable Star Observers (AAVSO) is an organization that counts the number of the sunspots. The effects of interplanetary shock waves on some physical parameters can be computed using a hydrodynamical model. There should be some correlations between these effects and the sunspot variations. The major objective of this paper is twofold. The first one is to search these correlations with sunspots given in the database of AAVSO. As expected, high correlations between physical parameters and sunspots have been obtained and these are presented in tables below. The second objective is to make an estimation of these parameters for the 22nd solar cycle and the years between 2015 and 2018 using an artificial neural network. Predictions have been made for these years where no shock data is present using artificial intelligence. The correlations were observed to increase further when these prediction results were included.

Statistical analysis of total column ozone during three recent solar cycles over India

Total column ozone (TCO) distribution and its variation over the Indian region at different stations for the period of about 30 years from 1986 to 2015 are studied. TCO data is taken from the merged ozone data set (MOD) overpass data for 15 different stations over India. The average correlation between TCO and solar proxies such as sunspot number and F10.7 cm solar flux is more than 0.5. We further divided the time series of TCO according to solar cycle as 22nd solar cycle (September 1986 to July 1996), 23rd solar cycle (August 1996 to November 2008) and 24th solar cycle (December 2008 to December 2015) (on going cycle) for a period of 1986–2015. Herein, for the long term trend analysis of TCO, we have removed the seasonal effect by the deseasonalization process, the effects of solar activities, stratospheric waves (quasi-biennial-oscillation-QBO and El Niño–Southern Oscillation-ENSO) by the multifunction linear regression method (MLR). We have compared both the linear trends in TCO which are calculated by the simple linear regression (SLR) and deseasonalised multifunction linear regression (DMLR) analysis. It is found that the direction of the trend in 22nd and the 23rd solar cycle is similar while, it is opposite in the 24th solar cycle. We observed a more negative trend in the 22nd solar cycle and less negative trend in the 23rd solar cycle while the trend is positive in the 24th solar cycle. The results indicate that after the DMLR process, the trend values are decreased by a large factor. Therefore, it is found that the role of natural variability is more than that of the ozone depleting substances (ODS) on long term variability in TCO over India. This statistical analysis provides better analysis of trend variation in TCO series over India. The main objective of this work is to analyze the variations in trend in the TCO with respect to the recent three solar cycles.

Hysteresis of indices of solar and ionospheric activity during 11-year cycles

The effects of hysteresis, which is a manifestation of ambiguous relationships between different solar activity indices during the rising and declining phases of solar cycles, are analyzed. The paper addresses the indices characterizing radiation from the solar photosphere, chromosphere, and corona, and the ionospheric indices. The 21st, 22nd, and 23rd solar cycles, which significantly differ from each other in amplitude, exhibit different extents of hysteresis.

The effect of the stratospheric QBO on the neutral density of the D region

<p>A multiple regression model, which defines relationship between two variables, is used to perform a statistical analysis of the relationship between the stratospheric QBO and the neutral density of the D region (N<sub>n</sub>D) at altitudes of 75 km and 90 km for Singapore station. While performing the analysis, the solar maxima and solar minima epochs of the sun for 21st, 22nd and 23rd solar cycles (SCs) are taken into account. Before applying the model for the statistical analysis of the relationship, the stationary of the variables is investigated by using the unit root test. The relationship between the variables is also investigated by using the co-integration test. The relationship between N<sub>n</sub>D measured at 75 km altitude and QBO obtained at altitude of 10 hPa is observed that it is positive for solar maximum epoch at 21st and 23rd SCs and for solar minimum epoch at 21st SC and is negative at the other epochs. The relationship between N<sub>n</sub>D measured at 90 km altitude and QBO is observed to be negative at both the solar maxima expect for solar maximum of 23rd SC and the solar minima epochs. The relationship between variables is positive for both phases (east and west) of QBO. Thus, QBO leads to a statistical change in the N<sub>n</sub>D. It may also give rise to changes on the ion chemistry of the D region.</p>

A cellular automata-based model of Earth's magnetosphere in relation withDstindex

The disturbance storm time (Dst) index, a measure of the strength of a geomagnetic storm, is difficult to predict by some conventional methods due to its abstract structural complexity and stochastic nature though a timely geomagnetic storm warning could save society from huge economic losses and hours of related hazards. Self-organized criticality and the concept of many-body interactive nonlinear system can be considered an explanation for the fundamental mechanism of the nonstationary geomagnetic disturbances controlled by the perturbed interplanetary conditions. The present paper approaches this natural phenomena by a sandpile-like cellular automata-based model of magnetosphere, taking the real-time solar wind and both the direction and magnitude of the BZ component of the real-time interplanetary magnetic field as the system-controlling input parameters. Moreover, three new parameters had been introduced in the model which modify the functional relationships between the variables and regulate the dynamical behavior of the model to closely approximate the actual geomagnetic fluctuations. The statistical similarities between the dynamics of the model and that of the actual Dst index series during the entire 22nd solar cycle signifies the acceptability of the model.

Temporal variations in the large-scale magnetic field of the solar atmosphere at heights from the photosphere to the source surface

Calculations of the magnetic field in the potential approximation (using Bd technology (Rudenko, 2001)) were used to study the time variations of several parameters of the large-scale magnetic field in the solar atmosphere during the last four cycles. Synoptic maps (SMs) for the radial component Br of the calculated magnetic field were plotted at 10 heights between the solar surface (R = R⊙) and the source (R = 2.5R⊙). On these SMs, we marked the 10-degree latitudinal areas. The following (averaged within the zone) characteristics of the magnetic field were determined corresponding to these zones: Sp, Sm; S+fields, where Sp is the positive value of Br, Sm is the averaged modulus of the negative Br; S+fields is the percentage of latitudinal zones with positive Br. The analysis of temporal variations in the magnitude of S points to different origins of the large-scale magnetic field in the near-equatorial and polar regions of the solar atmosphere. The analysis of temporal variations of S+fields showed that there were almost no periods with a mixed polarity at R = 2.5R⊙ during the 21st and 22nd solar cycles and in an ascending phase of the 23rd cycle. However, beginning from the maximum of the 23rd cycle, a mixed polarity in the equatorial region was observed until the end of the long minimum of activity. We hypothesized that this could be a precursor for a long minimum between the 23rd and 24th solar cycles. It was shown that during the maximum phase of the 24th solar cycle the magnetic field at R = R⊙ is much less than that during the maximum phase of the 23rd cycle, and in the region from 55° to 75°, this difference reaches an order of magnitude.

The dependence of flares on the magnetic classification of the source regions in solar cycles 22-23

Using 28 years of solar X-ray flares and sunspot-group records supplied by the National Geophysical Data Center, we carried a statistical study on the dependence of flares on the magnetic classification of the sunspot groups, and investigated the relationship with the phase in the 22nd and 23rd solar cycles. We found that (1) there are 83.34 per cent X-class flares, 62.35 per cent M-class flares, 43.18 per cent C-class flares, and 25.47 per cent B-class flares occurred in βγδ sunspot groups. (2) The occurrence of X-class flares in different sunspot groups shows clear periodic characteristics in phase with the solar cycle: near the two solar maximums, X-class flares occurred in various sunspot groups, but still most X-flares occurred in the βγδ sunspot groups. For the other phases, all X-class flare occurred in βγδ sunspot groups except 1998. The occurrence of M-class flares in different sunspot groups shows some periodic features in phase with the solar cycle. The occurrence of C-class and B-class flares in different sunspot groups shows weak periodic features with the phase of the solar cycle.

Rigidity spectrum of cosmic ray variations over periods of large Forbush decreases during the 22nd and 23rd solar cycles

This work presents our findings on the rigidity spectrum of cosmic ray (CR) variations during certain Forbush decreases recorded by the global neutron monitor network in 1991–2005. In most of the events we consider, the rigidity spectrum of primary CR variations is not described by a power function of rigidity in the energy range at which the neutron monitors are most sensitive.

Cyclic evolution of the global magnetic field observed during the 21st and 22nd solar cycles

The global component of the large-scale magnetic field is identified using two methods applied to Stanford Observatory data on the photospheric magnetic field obtained in 1976–2000. Two significantly different phases are observed in the evolution of the global magnetic field detected during the 11-year cycle. Phase I includes the cycle growth and maximum, while Phase II includes the cycle decay and minimum. During Phases I and II of the 11-year cycle, two different processes dominate both the magnetic-field generation and the solar activity as a whole. At lower latitudes, Phase I demonstrates a longitudinal splitting of the magnetic field, which takes the form of stripes of opposite polarities located parallel to the equator. The long dimensions of these stripes are grouped near 90° and 180°. The global magnetic field rotates as a rigid body with a period that is appreciably shorter than the Carrington-rotation period and reaches about 27.225 days. During reversals of the polarity of the global magnetic field, the field displays opposite signs in antipodal longitude intervals with lengths of about 135°. Thus, the equatorial dipolar field is clearly manifest during Phase I. Transitional longitude intervals with widths of 45° located between 135° intervals correspond to the positions of active longitudes of sunspots, indicating a close relationship between the global and local magnetic fields.

A statistical study on photospheric active-region magnetic nonpotentiality and associated flares during solar cycles 22 – 23

AbstractUsing photospheric data obtained by vector magnetograph in Huairou Solar Observing Station of China, we have statistically studied the strength evolution of several magnetic nonpotentiality measures, along with a quantified parameter characterizing the active-region magnetic complexity – effective distance, and their relationship with associated flares during the latest 22nd and 23rd solar cycles. And the flare-prediction performance of these magnetic nonpotentiality and complexity parameters is verified by a machine learning technique.

A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares During Solar Cycles 22 – 23

A statistical study is carried out on the photospheric magnetic nonpotentiality in solar active regions and its relationship with associated flares. We select 2173 photospheric vector magnetograms from 1106 active regions observed by the Solar Magnetic Field Telescope at Huairou Solar Observing Station, National Astronomical Observatories of China, in the period of 1988 – 2008, which covers most of the 22nd and 23rd solar cycles. We have computed the mean planar magnetic shear angle (\(\overline{\Delta\phi}\)), mean shear angle of the vector magnetic field (\(\overline{\Delta\psi}\)), mean absolute vertical current density (\(\overline{|J_{z}|}\)), mean absolute current helicity density (\(\overline{|h_{\mathrm{c}}|}\)), absolute twist parameter (|α av|), mean free magnetic energy density (\(\overline{\rho_{\mathrm{free}}}\)), effective distance of the longitudinal magnetic field (d E), and modified effective distance (d Em) of each photospheric vector magnetogram. Parameters \(\overline{|h_{\mathrm{c}}|}\), \(\overline{\rho_{\mathrm{free}}}\), and d Em show higher correlations with the evolution of the solar cycle. The Pearson linear correlation coefficients between these three parameters and the yearly mean sunspot number are all larger than 0.59. Parameters \(\overline {\Delta\phi}\), \(\overline{\Delta\psi}\), \(\overline{|J_{z}|}\), |α av|, and d E show only weak correlations with the solar cycle, though the nonpotentiality and the complexity of active regions are greater in the activity maximum periods than in the minimum periods. All of the eight parameters show positive correlations with the flare productivity of active regions, and the combination of different nonpotentiality parameters may be effective in predicting the flaring probability of active regions.

Activity complexes on the sun during the 23rd solar cycle

Results of the study of activity complexes of (AC) on the Sun that evolved during the 23rd solar cycle (SC) are presented. Based on ananalysis of synoptic charts of sunspot activity, 69 AC cores have been detected in the Northern Hemisphere, and 77 AC cores, in the Southern Hemisphere during the 23rd SC. An AC core catalogue has been composed. We have found an increase in the number of AC cores with lifetime (maximum 14 rotations); their nonuniform longitudinal distribution; and a local drop in the number of AC cores during the 23rd SC maximum (1967th–1979th rotations, October 2000–August 2001). The quasiperiodic character of variations in the total rotation-to-rotation power of AC cores during the cycle has been ascertained; the quasi-has 12–14 rotations. A feature of the 23rd SC is a prolonged period of AC generation in comparison with the 22nd SC. Last AC cores in the Southern Hemisphere were observed until the 144th rotation after the previous minimum according to the Wolf numbers (to the 110th rotation in the 22nd SC). The total number of AC cores in the 23rd SC (146) far exceeds that in the 22nd SC (104). Ninety-four percent of high-power proton flares with an energy higher than 10 MeV and a flux of more than 10/(s sm2 sr) at the Earth’s orbit occurred near the AC cores. The total number of proton flares related to AC cores of the above class increased: 48 in the 22nd SC versus 62 in the 23rd SC. We have also revealed a strong north-south asymmetry in the AC evolution manifesting itself in different indices describing AC on the Sun.

North‐south asymmetry of the location of the heliospheric current sheet revisited

The possible latitudinal offset of the location of the heliospheric current sheet (HCS) is an important question, since it has impact on the understanding of various phenomena including the solar dynamo and the modulation of cosmic rays. In the declining phase of the previous, 22nd solar cycle, in 1993, a southward displacement of the HCS by 10° was proposed to explain the north‐south asymmetry of energetic charged‐particle fluxes measured by Ulysses. Other observations supported the north‐south asymmetry as well, and it is now widely accepted by the scientific community that in 1993, the HCS was displaced 10° southward. However, in reality, the Ulysses magnetic field measurements did not give direct evidence for such a large displacement of the HCS. Here we revisit the question and extend our previous study for the declining phase of solar cycle 23 as well. Careful analysis of the HCS crossings observed by Ulysses during the fast latitude scans shows that a southward displacement of the HCS by 2°–3° is possible and consistent with the data for cycles 22 and 23. The impact of the HCS location on the latitudinal gradients of energetic particle fluxes is discussed.

Magnetic Fields and Solar Activities

We discuss the study of solar magnetic fields based on the photospheric vector magnetograms of solar active regions which were obtained at Huairou Solar Observing Station near Beijing in the period of 22nd and 23th solar cycles. The measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic field. After the analysis on the formation process of delta configuration in some super active regions based on the photospheric vector magnetogram observations, some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, proposed to be generated in the subatmosphere, is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and the relationship with magnetic shear in some delta active regions completely. (3) The proposition is that the large-scale delta active regions are formed from contribution by highly sheared non-potential magnetic flux bundles generated in the subatmosphere. We present some results of a study of the magnetic helicity. We also compare these results with other data sets obtained by magnetographs (or Stokes polarimeters) at different observatories, and analyze the basic chirality of the magnetic field in the solar atmosphere.

Statistical Correlation of the Rate of Failures on Geosynchronous Satellites with Fluxes of Energetic Electrons and Protons

A statistical comparison of failures on geosynchronous satellites in the maximum and during the decline of the 22nd solar cycle (1989–1994) with space weather parameters is carried out. A positive correlation of the rate of failures with the flux of relativistic electrons on the geosynchronous orbit and with the proton flux measured before the bow shock front is revealed. The significant positive correlation of the electron flux with the rate of failures is observed during the entire considered interval. The correlation coefficient varies in the solar activity cycle in coordination with the electron flux, and the maxima of the correlation coefficient are observed on the phase of decline of the cycle. A statistically significant positive correlation between the flux of protons with energy of more than 1 MeV and the rate of failures is revealed in the maximum of the solar cycle.

Specific features of the high-speed plasma stream cycles

Abstract The high-speed plasma streams in the solar wind are investigated during the solar cycles nos. 20–22 (1964–1996), separately on the two types of streams according to their solar origin: the HSPS produced by coronal holes (co-rotating) and the flare-generated, in keeping with the classification made in different catalogues. The analysis is performed taking into account the following high-speed stream parameters: the durations (in days), the maximum velocities, the velocity gradients and, the importance of the streams. The time variation of these parameters and the high-speed plasma streams occurrence rate show an 11-year periodicity with some differences between the solar cycles considered. A detailed analysis of the high-speed stream 11-year cycles is made by comparison with the “standard” cycles of the sunspot relative number (Wolf number). The different behaviour of the high-speed stream parameters between even and odd solar cycles could be due to the 22-year solar magnetic cycle. The increased activity of the high-speed plasma streams on the descendant phases of the cycles, regardless of their solar sources, proves the existence of some special local conditions of the solar plasma and the magnetic field on a large scale that allow the ejection of the high energy plasma streams. This fact has led us to the analysis the stream parameters during the different phases of the solar cycles (minimum, ascendant, maximum and, descendant) as well as during the polar magnetic field reversal intervals. The differences between the phases considered are pointed out. The solar cycles 20 and 22 reveal very similar dynamics of the flare-generated and also co-rotating stream parameters during the maximum, descendant and reversal intervals. This fact could be due to their position in a Hale Cycle (the first component of the 22-year solar magnetic cycle). The 21st solar cycle dominance of all co-rotating stream parameters against the 20th and 22nd solar cycle ones, during almost all phases, could be due to the same structure of a Hale Cycle – solar cycle 21 is the second component in a 22-year SC. During the reversal intervals, all high-speed stream parameters have comparable values with the ones of the maximum phases of the cycles even if this interval contains a small part of the descendant branch (solar cycles 20 and 22).

On solar 5.7 GHz subsecond burst source sizes

Due to the narrow bandwidth and the small size of the subsecond microwave pulses, we can use them as probe sources for study of propagation effects in the low corona. More than 160 microwave bursts with subsecond pulses (SSP) have been observed with the Siberian Solar Radio Telescope at 5.7 CHz for the period 2000–2004. Working with a large dataset of homogeneous observational material (spatial resolution from 15″ to 20″, temporal resolution 14 mc), we estimated sizes of SSP and studied relation between SSP sizes and sense of the polarization and their position on the Sun. Our results are in accordance with those obtained during the 22nd solar cycle. The apparent sizes of SSP increase toward the solar limb. The obtained dependence is in agreement with Bastian‘s (Bastian, T.S. Angular scattering of solar radio emission by coronal turbulence. ApJ 426, 774, 1994.) model calculations. The center-to-limb variation of the source size is explained by scattering on plasma turbulence along the ray path in the solar corona. The most events with high polarization occur near the central meridian (±30°). The polarization sense corresponds mainly to the ordinary mode.