scholarly journals Comparison of Geomagnetic Indices During Even and Odd Solar Cycles SC17 – SC24: Signatures of Gnevyshev Gap in Geomagnetic Activity

Solar Physics ◽  
2021 ◽  
Vol 296 (1) ◽  
Author(s):  
Jouni Takalo
Keyword(s):  
Time Series ◽  
Geomagnetic Activity ◽  
Sunspot Group ◽  
Solar Cycles ◽  
Geomagnetic Disturbances ◽  
Similar Length ◽  
Dst Index ◽  
Small Decline ◽  
Ap Index ◽  
Odd Cycles

AbstractWe show that the time series of sunspot group areas has a gap, the so-called Gnevyshev gap (GG), between ascending and descending phases of the cycle and especially so for the even-numbered cycles. For the odd cycles this gap is less obvious, and is only a small decline after the maximum of the cycle. We resample the cycles to have the same length of 3945 days (about 10.8 years), and show that the decline is between 1445 – 1567 days after the start of the cycle for the even cycles, and extending sometimes until 1725 days from the start of the cycle. For the odd cycles the gap is a little earlier, 1332 – 1445 days after the start of the cycles with no extension. We analyze geomagnetic disturbances for Solar Cycles 17 – 24 using the Dst-index, the related Dxt- and Dcx-indices, and the Ap-index. In all of these time series there is a decline at the time, or somewhat after, the GG in the solar indices, and it is at its deepest between 1567 – 1725 days for the even cycles and between 1445 – 1567 days for the odd cycles. The averages of these indices for even cycles in the interval 1445 – 1725 are 46%, 46%, 18%, and 29% smaller compared to surrounding intervals of similar length for Dst, Dxt, Dcx, and Ap, respectively. For odd cycles the averages of the Dst- and Dxt-indices between 1322 – 1567 days are 31% and 12% smaller than the surrounding intervals, but not smaller for the Dcx-index and only 4% smaller for the Ap-index. The declines are significant at the 99% level for both even and odd cycles of the Dst-index and for the Dxt-, Dcx- and Ap-indices for even cycles. For odd cycles of the Dxt-index the significance is 95%, but the decline is insignificant for odd cycles of the Dcx- and Ap-indices.

scholarly journals Systemic lupus Erythematosus and geomagnetic disturbances: a time series analysis

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
George Stojan ◽  
Flavia Giammarino ◽  
Michelle Petri
Keyword(s):  
Time Series ◽  
Disease Activity ◽  
Sunspot Number ◽  
Geomagnetic Activity ◽  
High Energy ◽  
Bonferroni Correction ◽  
Geomagnetic Disturbances ◽  
Short Term ◽  
Ap Index

Abstract Background To examine the influence of solar cycle and geomagnetic effects on SLE disease activity. Methods The data used for the analysis consisted of 327 observations of 27-day Physician Global Assessment (PGA) averages from January 1996 to February 2020. The considered geomagnetic indices were the AP index (a daily average level for geomagnetic activity), sunspot number index R (measure of the area of solar surface covered by spots), the F10.7 index (measure of the noise level generated by the sun at a wavelength of 10.7 cm at the earth’s orbit), the AU index (upper auroral electrojet index), and high energy (> 60 Mev) proton flux events. Geomagnetic data were obtained from the Goddard Space Flight Center Space Physics Data Facility. A time series decomposition of the PGA averages was performed as the first step. The linear relationships between the PGA and the geomagnetic indices were examined using parametric statistical methods such as Pearson correlation and linear regression, while the nonlinear relationships were examined using nonparametric statistical methods such as Spearman’s rho and Kernel regression. Results After time series deconstruction of PGA averages, the seasonality explained a significant fraction of the variance of the time series (R2 = 38.7%) with one cycle completed every 16 years. The analysis of the short-term (27-day) relationships indicated that increases in geomagnetic activity Ap index (p < 0.1) and high energy proton fluxes (> 60 Mev) (p < 0.05) were associated with decreases in SLE disease activity, while increases in the sunspot number index R anticipated decreases in the SLE disease activity expressed as PGA (p < 0.05). The short-term correlations became statistically insignificant after adjusting for multiple comparisons using Bonferroni correction. The analysis of the long-term (297 day) relationships indicated stronger negative association between changes in the PGA and changes in the sunspot number index R (p < 0.01), AP index (p < 0.01), and the F10.7 index (p < 0.01). The long-term correlations remained statistically significant after adjusting for multiple comparisons using Bonferroni correction. Conclusion The seasonality of the PGA averages (one cycle every 16 years) explains a significant fraction of the variance of the time series. Geomagnetic disturbances, including the level of geomagnetic activity, sunspot numbers, and high proton flux events may influence SLE disease activity. Studies of other geographic locales are needed to validate these findings.

Variations in solar and geomagnetic activity with periods near to 1.3 year

2009 ◽  
Vol 1 (2) ◽  
Author(s):  
Jaroslav Střeštïk
Keyword(s):  
Geomagnetic Activity ◽  
Time Series Data ◽  
Interplanetary Space ◽  
Short Interval ◽  
Biological Data ◽  
Series Data ◽  
Solar Cycles ◽  
Lower Amplitude ◽  
Periodic Signals ◽  
Odd Cycles

AbstractIt is known that solar wind velocity fluctuates regularly with a period of about 1.3 years. This periodicity (and other signals with periods near to 1.1 and 0.9 years) has also been observed in biological data. The variation is a temporary feature, mostly being observed in the early 1990s. Here, the occurrence of these periodic signals in solar and geomagnetic activity between 1932 and 2005 has been investigated. The signal with 1.3 year period is present in geomagnetic activity only in a short interval after 1990 and to a lesser extent around 1942. At other times the signal is very weak or not present at all. Other periods are much lower amplitude and appear only sporadically throughout the time investigated. A connection between these periods and solar cycles (e.g. different even or odd cycles) has not been proven. It is possible that there is a long-term periodicity in the occurrence of the 1.3 year period but the time series data available is insufficient to confirm this. There are no such periodicities in solar activity. In order to gain a greater understanding of these periodic signals, we should search for their origin in interplanetary space.

scholarly journals The Main Component Analysis of the Longitudinal Distribution of Solar Activity

1991 ◽  
Vol 130 ◽  
pp. 275-276
Author(s):  
Ladislav Hejna ◽  
Hubertus Wöhl
Keyword(s):  
Time Series ◽  
Solar Activity ◽  
Sunspot Group ◽  
Component Analysis ◽  
Longitudinal Distribution ◽  
Sunspot Activity ◽  
Significant Feature ◽  
Solar Cycles ◽  
Main Component Analysis ◽  
Main Component

Abstract In this contribution, preliminary results of the main component analysis of Bartels diagram of time series of daily values of sunspot group numbers for solar cycles 18, 19 and 20 are presented. The results obtained suggest that the most significant feature in the longitudinal distribution of sunspot activity is the existence of preferred solar hemispheres alternating with a mean period of 2.5 Bartels rotations.

scholarly journals Comparison of the shape and temporal evolution of even and odd solar cycles

2020 ◽  
Vol 636 ◽  
pp. A11
Author(s):  
Jouni Takalo ◽  
Kalevi Mursula
Keyword(s):  
Sunspot Group ◽  
Temporal Evolution ◽  
Sunspot Area ◽  
Distribution Analysis ◽  
Solar Cycles ◽  
Sunspot Numbers ◽  
Group Data ◽  
Odd Cycles ◽  
Skewness And Kurtosis ◽  
Sunspot Groups

Aims. We study the difference in the shape of solar cycles for even and odd cycles using the Wolf sunspot numbers and group sunspot numbers of solar cycles 1−23. We furthermore analyse the data of sunspot area sizes for even and odd cycles SC12−SC23 and sunspot group data for even and odd cycles SC8−SC23 to compare the temporal evolution of even and odd cycles. Methods. We applied the principal component analysis (PCA) to sunspot cycle data and studied the first two components, which describe the average cycle shape and cycle asymmetry. We used a distribution analysis to analyse the temporal evolution of the even and odd cycles and determined the skewness and kurtosis for even and odd cycles of sunspot group data. Results. The PCA confirms the existence of the Gnevyshev gap (GG) for solar cycles at about 40% from the start of the cycle. The temporal evolution of sunspot area data for even cycles shows that the GG exists at least at the 95% confidence level for all sizes of sunspots. On the other hand, the GG is shorter and statistically insignificant for the odd cycles of aerial sunspot data. Furthermore, the analysis of sunspot area sizes for even and odd cycles of SC12−SC23 shows that the greatest difference is at 4.2−4.6 years, where even cycles have a far smaller total area than odd cycles. The average area of the individual sunspots of even cycles is also smaller in this interval. The statistical analysis of the temporal evolution shows that northern sunspot groups maximise earlier than southern groups for even cycles, but are concurrent for odd cycles. Furthermore, the temporal distributions of odd cycles are slightly more leptokurtic than distributions of even cycles. The skewnesses are 0.37 and 0.49 and the kurtoses 2.79 and 2.94 for even and odd cycles, respectively. The correlation coefficient between skewness and kurtosis for even cycles is 0.69, and for odd cycles, it is 0.90. Conclusions. The separate PCAs for even and odd sunspot cycles show that odd cycles are more inhomogeneous than even cycles, especially in GSN data. Even cycles, however, have two anomalous cycles: SC4 and SC6. The variation in the shape of the early sunspot cycles suggests that there are too few and/or inaccurate measurements before SC8. According to the analysis of the sunspot area size data, the GG is more distinct in even than odd cycles. This may be partly due to sunspot groups maximizing earlier in the northern than in the southern hemisphere for even cycles. We also present another Waldmeier-type rule, that is, we find a correlation between skewness and kurtosis of the sunspot group cycles.

scholarly journals On the multi-scale nature of large geomagnetic storms: an empirical mode decomposition analysis

2012 ◽  
Vol 19 (6) ◽  
pp. 667-673 ◽  
Author(s):  
P. De Michelis ◽  
G. Consolini ◽  
R. Tozzi
Keyword(s):  
Time Series ◽  
Empirical Mode Decomposition ◽  
Geomagnetic Activity ◽  
Geomagnetic Storms ◽  
Decomposition Analysis ◽  
Activity Level ◽  
Activity Levels ◽  
Geomagnetic Disturbances ◽  
Multi Scale ◽  
Mode Decomposition

Abstract. Complexity and multi-scale are very common properties of several geomagnetic time series. On the other hand, it is amply demonstrated that scaling properties of geomagnetic time series show significant changes depending on the geomagnetic activity level. Here, we study the multi-scale features of some large geomagnetic storms by applying the empirical mode decomposition technique. This method, which is alternative to traditional data analysis and is designed specifically for analyzing nonlinear and nonstationary data, is applied to long time series of Sym-H index relative to periods including large geomagnetic disturbances. The spectral and scaling features of the intrinsic mode functions (IMFs) into which Sym-H time series can be decomposed, as well as those of the Sym-H time series itself, are studied considering different geomagnetic activity levels. The results suggest an increase of dynamical complexity and multi-scale properties for intermediate geomagnetic activity levels.

scholarly journals Influence of geomagnetic activity on mesopause temperature over Yakutia

2018 ◽  
Vol 18 (5) ◽  
pp. 3363-3367 ◽  
Author(s):  
Galina Gavrilyeva ◽  
Petr Ammosov
Keyword(s):  
Geomagnetic Activity ◽  
Rotational Temperature ◽  
Activity Level ◽  
Solar Radio Emission ◽  
Neutral Atmosphere ◽  
Solar Cycles ◽  
Temporal Shift ◽  
Cross Correlation Analysis ◽  
Ap Index ◽  
Mesopause Temperature

Abstract. The long-term temperature changes of the mesopause region at the hydroxyl molecule OH (6-2) nighttime height and its connection with the geomagnetic activity during the 23rd and beginning of the 24th solar cycles are presented. Measurements were conducted with an infrared digital spectrograph at the Maimaga station (63∘ N, 129.5∘ E). The hydroxyl rotational temperature (TOH) is assumed to be equal to the neutral atmosphere temperature at the altitude of ∼ 87 km. The average temperatures obtained for the period 1999 to 2015 are considered. The season of observations starts at the beginning of August and lasts until the middle of May. The maximum of the seasonally averaged temperatures is delayed by 2 years relative to the maximum of the solar radio emission flux (wavelength of 10.7 cm), and correlates with a change in geomagnetic activity (Ap index). Temperature grouping in accordance with the geomagnetic activity level showed that in years with high activity (Ap > 8), the mesopause temperature from October to February is about 10 K higher than in years with low activity (Ap < = 8). Cross-correlation analysis showed no temporal shift between geomagnetic activity and temperature. The correlation coefficient is equal to 0.51 at the 95 % level.

scholarly journals Influence of geomagnetic activity on mesopause temperature over Yakutia

2017 ◽  
Author(s):  
Galina Gavrilyeva ◽  
Petr Ammosov
Keyword(s):  
Geomagnetic Activity ◽  
Rotational Temperature ◽  
Activity Level ◽  
Neutral Atmosphere ◽  
Solar Cycles ◽  
Temperature Changes ◽  
Atmosphere Temperature ◽  
Ap Index ◽  
Mesopause Temperature

Abstract. The long-term temperature changes of the mesopause region at the hydroxyl molecule OH (6-2) nighttime height and its connection with the geomagnetic activity during the 23rd and beginning 24th solar cycles are presented. Measurements were conducted with an infrared digital spectrograph at the Maimaga station (63° N, 129.5° E). The hydroxyl rotational temperature (TOH) is assumed to be equal to the neutral atmosphere temperature at altitude of ~ 87 km. The average temperatures obtained for the period 1999 to 2015 are considered. The season of observations starts at the beginning of August and lasts until the middle of May. The maximum of the seasonally averaged temperatures is delayed by 2 years relative to the maximum of flux of radio emission from the Sun with a wavelength of 10.7 cm, and correlates with a change in geomagnetic activity. Ap-index as a measure of geomagnetic activity is taken. Temperature grouping in accordance with the geomagnetic activity level showed that in years with high activity (Ap > 8), the mesopause temperature from October to February is about ∙10 K higher than in years with low activity (Ap 

scholarly journals MID-LATITUDE AURORA IN SOLAR CYCLES 23–24 FROM OBSERVATIONS IN THE SOUTH OF EASTERN SIBERIA

2019 ◽  
Vol 5 (4) ◽  
pp. 66-73
Author(s):  
Aleksandr Mikhalev
Keyword(s):  
Geomagnetic Activity ◽  
Detection Probability ◽  
Geomagnetic Storms ◽  
Spectral Composition ◽  
Eastern Siberia ◽  
Solar Cycles ◽  
The South ◽  
Dst Index ◽  
Close Relationship ◽  
Auroral Emissions

The paper presents observations of mid-latitude aurora (MA) in the south of Eastern Siberia in solar cycles 23–24. Spectral composition and dominant emissions of MA, daily distribution of MA detection probability, dependence on the level of geomagnetic activity, and classification according to types of aurora are discussed. A close relationship is shown between the intensity of dominant emission at 630.0 nm and the Dst index during magnetic storms (MSs). It is pointed out that the most intense MA are recorded during MS main phases. The MA detected on November 20, 2003 can enlarge the list of great aurora. For the severe MSs (Dstmin< –200 nT) of March 24, 1991, April 6, 2000, October 30 and November 20, 2003, March 17, 2015, the observed dynamics of 557.7 and 630.0 nm auroral emissions is presented. Mechanisms of emission excitation during geomagnetic storms and a possible connection with magnetospheric structures are discussed.

scholarly journals MID-LATITUDE AURORA IN SOLAR CYCLES 23–24 FROM OBSERVATIONS IN THE SOUTH OF EASTERN SIBERIA

2019 ◽  
Vol 5 (4) ◽  
pp. 80-89
Author(s):  
Aleksandr Mikhalev
Keyword(s):  
Geomagnetic Activity ◽  
Detection Probability ◽  
Geomagnetic Storms ◽  
Spectral Composition ◽  
Eastern Siberia ◽  
Solar Cycles ◽  
The South ◽  
Dst Index ◽  
Close Relationship ◽  
Auroral Emissions

The paper presents observations of mid-latitude aurora (MA) in the south of Eastern Siberia in solar cycles 23–24. Spectral composition and dominant emissions of MA, daily distribution of MA detection probability, dependence on the level of geomagnetic activity, and classification according to types of aurora are discussed. A close relationship is shown between the intensity of dominant emission at 630.0 nm and the Dst index during magnetic storms (MSs). It is pointed out that the most intense MA are recorded during MS main phases. The MA detected on November 20, 2003 can enlarge the list of great aurora. For the severe MSs (Dstmin< –200 nT) of March 24, 1991, April 6, 2000, October 30 and November 20, 2003, March 17, 2015, the observed dynamics of 557.7 and 630.0 nm auroral emissions is presented. Mechanisms of emission excitation during geomagnetic storms and a possible connection with magnetospheric structures are discussed.

The LDE-Type Flare Occurrence (1969-1993)

1994 ◽  
Vol 144 ◽  
pp. 279-282
Author(s):  
A. Antalová
Keyword(s):  
Time Series ◽  
Fourier Analysis ◽  
Sunspot Cycle ◽  
List Type ◽  
Type Number ◽  
Solar Cycles ◽  
Type Iv ◽  
Long Duration ◽  
Cycle Maximum ◽  
Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

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