Maximum sunspot number R z (max) in the coming solar cycle No. 22 ? A revised estimate

Sunspots are temporary phenomena on the photosphere of the Sun which appear visibly as dark spots compared to surrounding regions. Sunspot populations usually rise fast but fall more slowly when observed for any particular solar cycle. The sunspot numbers for the current cycle 24 and the previous three cycles have been plotted for duration of first four years for each of them. It appears that the value of peak sunspot number for solar cycle 24 is smaller than the three preceding cycles. When regression analysis is made it exhibits a trend of slow rising phase of the cycle 24 compared to previous three cycles. Our analysis further shows that cycle 24 is approaching to a longer-period but with smaller occurrences of sunspot number.

Download Full-text

Mid-term Periodicities in Solar Radio Emission Corresponding to Sunspot Number During Solar Cycle 23

Solar Physics ◽

10.1007/s11207-021-01793-6 ◽

2021 ◽

Vol 296 (3) ◽

Author(s):

Mahender Aroori ◽

Panditi Vemareddy ◽

Partha Chowdhury ◽

Ganji Yellaiah

Keyword(s):

Solar Cycle ◽

Radio Emission ◽

Sunspot Number ◽

Solar Radio ◽

Solar Radio Emission ◽

Solar Cycle 23

Download Full-text

Seasonal, Diurnal, and Solar-Cycle Variations of Electron Density at Two West Africa Equatorial Ionization Anomaly Stations

International Journal of Geophysics ◽

10.1155/2012/640463 ◽

2012 ◽

Vol 2012 ◽

pp. 1-9 ◽

Cited By ~ 10

Author(s):

Frédéric Ouattara ◽

Doua Allain Gnabahou ◽

Christine Amory Mazaudier

Keyword(s):

Solar Cycle ◽

West Africa ◽

Ultraviolet Radiation ◽

Correlation Coefficient ◽

Sunspot Number ◽

Extreme Ultraviolet ◽

Cycle Phase ◽

Significant Variability ◽

Equatorial Ionization Anomaly ◽

Significant Difference

We analyse the variability of foF2 at two West Africa equatorial ionization anomaly stations (Ouagadougou and Dakar) during three solar cycles (from cycle 20 to cycle 22), that is, from 1966 to 1998 for Ouagadougou and from 1971 to 1997 for Dakar. We examine the effect of the changing levels of solar extreme ultraviolet radiation with sunspot number. The study shows high correlation between foF2 and sunspot number (Rz). The correlation coefficient decreases from cycle 20 to cycle 21 at both stations. From cycle 21 to cycle 22 it decreases at Ouagadougou station and increases at Dakar station. The best correlation coefficient, 0.990, is obtained for Dakar station during solar cycle 22. The seasonal variation displays equinoctial peaks that are asymmetric between March and September. The percentage deviations of monthly average data from one solar cycle to another display variability with respect to solar cycle phase and show solar ultraviolet radiation variability with solar cycle phase. The diurnal variation shows a noon bite out with a predominant late-afternoon peak except during the maximum phase of the solar cycle. The diurnal Ouagadougou station foF2 data do not show a significant difference between the increasing and decreasing cycle phases, while Dakar station data do show it, particularly for cycle 21. The percentage deviations of diurnal variations from solar-minimum conditions show more ionosphere during solar cycle 21 at both stations for all three of the other phases of the solar cycle. There is no significant variability of ionosphere during increasing and decreasing solar cycle phases at Ouagadougou station, but at Dakar station there is a significant variability of ionosphere during these two solar-cycle phases.

Download Full-text

Solar Wind Helium Abundance Heralds Solar Cycle Onset

10.21203/rs.3.rs-260684/v1 ◽

2021 ◽

Author(s):

Benjamin L Alterman ◽

Justin C Kasper ◽

Robert J Leamon ◽

Scott W McIntosh

Keyword(s):

Solar Wind ◽

Solar Cycle ◽

Sunspot Number ◽

Cycle Length ◽

Phase Lag ◽

Helium Abundance ◽

Solar Cycles ◽

Wind Speeds ◽

Solar Wind Acceleration ◽

Solar Cycle Length

Abstract We study the solar wind helium-to-hydrogen abundance's ( A He ) relationship to solar cycle onset. Using OMNI/Lo data, we show that A He increases prior to sunspot number (SSN) minima. We also identify a rapid depletion and recovery in A He that occurs directly prior to cycle onset. This A He Shutoff happens at approximately the same time across solar wind speeds ( v sw ) and the time between successive A He shutoffs is typically on the order of the corresponding solar cycle length. In contrast to A He 's v sw -dependent phase lag with respect to SSN (Alterman and Kasper, 2019), A He Shutoff's concurrence across v sw likely implies it is independent of solar wind acceleration and driven by a mechanism near or below the photosphere. Using Brightpoint (BP) measurements to provide context, we infer that this shutoff is likely related to the overlap of adjacent solar cycles and the equatorial flux cancelation of the older, extended solar cycle during solar minima.

Download Full-text

ESTABLISHING SOLAR ACTIVITY TREND FOR SOLAR CYCLES 21 – 24

PHYSICS OF AURORAL PHENOMENA ◽

10.51981/2588-0039.2021.44.023 ◽

2021 ◽

Vol 44 ◽

pp. 100-106

Author(s):

A.K. Singh ◽

◽

A. Bhargawa ◽

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Sunspot Number ◽

Cosmic Ray ◽

Occurrence Rate ◽

The Sun ◽

Solar Cycles ◽

Lyman Alpha ◽

Rate Versus ◽

Alpha Index

Solar-terrestrial environment is manifested primarily by the physical conditions of solar interior, solar atmosphere and eruptive solar plasma. Each parameter gives unique information about the Sun and its activity according to its defined characteristics. Hence the variability of solar parameters is of interest from the point of view of plasma dynamics on the Sun and in the interplanetary space as well as for the solar-terrestrial physics. In this study, we have analysed various solar transients and parameters to establish the recent trends of solar activity during solar cycles 21, 22, 23 and 24. The correlation coefficients of linear regression of F10.7 cm index, Lyman alpha index, Mg II index, cosmic ray intensity, number of M & X class flares and coronal mass ejections (CMEs) occurrence rate versus sunspot number was examined for last four solar cycles. A running cross-correlation method has been used to study the momentary relationship among the above mentioned solar activity parameters. Solar cycle 21 witnessed the highest value of correlation for F10.7 cm index, Lyman alpha index and number of M-class and X-class flares versus sunspot number among all the considered solar cycles which were 0.979, 0.935 and 0.964 respectively. Solar cycle 22 recorded the highest correlation in case of Mg II index, Ap index and CMEs occurrence rate versus sunspot number among all the considered solar cycles (0.964, 0.384 and 0.972 respectively). Solar cycle 23 and 24 did not witness any highest correlation compared to solar cycle 21 and 22. Further the record values (highest value compared to other solar three cycles) of each solar activity parameters for each of the four solar cycles have been studied. Here solar cycle 24 has no record text at all, this simply indicating that this cycle was a weakest cycle compared to the three previous ones. We have concluded that in every domain solar 24 was weaker to its three predecessors.

Download Full-text