The variations with a period of two solar cycles in the cosmic ray diurnal anisotropy for the nucleonic component

1993 ◽  
pp. 439-445
Author(s):  
S. P. Duggal ◽  
S. E. Forbush ◽  
M. A. Pomerantz
Keyword(s):  
Cosmic Ray ◽  
Solar Cycles ◽  
Diurnal Anisotropy ◽  
Nucleonic Component

scholarly journals Latitudinal and longitudinal dependence of the cosmic ray diurnal anisotropy during 2001–2014

2016 ◽  
Vol 34 (11) ◽  
pp. 1053-1068 ◽  
Author(s):  
Anastasia Tezari ◽  
Helen Mavromichalaki ◽  
Dimitrios Katsinis ◽  
Anastasios Kanellakopoulos ◽  
Sofia Kolovi ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Neutron Monitor ◽  
Cosmic Ray ◽  
Longitudinal Distribution ◽  
Solar Cycles ◽  
Field Polarity ◽  
Monthly Basis ◽  
Cosmic Ray Intensity ◽  
Asymptotic Cones ◽  
Diurnal Anisotropy

Abstract. The diurnal anisotropy of cosmic ray intensity for the time period 2001 to 2014 is studied, covering the maximum and the descending phase of solar cycle 23, the minimum between solar cycles 23 and 24, and the ascending phase and maximum of solar cycle 24. Cosmic ray intensity data from 11 neutron monitor stations located at different places around the Northern Hemisphere obtained from the high-resolution Neutron Monitor Database (NMDB) were used. Special software was developed for the calculations of the amplitude and the phase of the diurnal anisotropy vectors on annual and monthly basis using Fourier analysis and for the creation of the harmonic dial diagrams. The geomagnetic bending for each station was taken into account in our calculations determined from the asymptotic cones of each station via the Tsyganenko96 (Tsyganenko and Stern, 1996) magnetospheric model. From our analysis, it was resulted that there is a different behavior of the diurnal anisotropy vectors during the different phases of the solar cycles depending on the solar magnetic field polarity. The latitudinal and longitudinal distribution of the cosmic ray diurnal anisotropy was also examined by grouping the stations according to their geographic coordinates, and it was shown that diurnal variation is modulated not only by the latitude but also by the longitude of the stations. The diurnal anisotropy during strong events of solar and/or cosmic ray activity is discussed.

A clock for the Sun's magnetic Hale cycle and 27 day recurrences in the aa geomagnetic index

2021 ◽  
Author(s):  
Sandra Chapman ◽  
Scott McIntosh ◽  
Robert Leamon ◽  
Nicholas Watkins
Keyword(s):  
High Speed ◽  
Cosmic Ray ◽  
Magnetic Polarity ◽  
Cycle Phase ◽  
High Time Resolution ◽  
Solar Cycles ◽  
Odd Cycle ◽  
The Hilbert Transform ◽  
Slow Timescale ◽  
Aa Index

<p>We construct a new solar cycle phase clock which maps each of the last 18 solar cycles onto a single normalized epoch for the approximately 22 year Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSN) since 1818. We use the clock to study solar and geomagnetic climatology as seen in datasets available over multiple solar cycles. The occurrence of solar maxima on the clock shows almost no Hale cycle dependence, confirming that the clock is synchronized with polarity reversals.  The odd cycle minima lead the even cycle minima by ~ 1.1 normalized years, whereas the odd cycle terminators (when sunspot bands from opposite hemispheres have moved to the equator and coincide, thus terminating the cycle, McIntosh(2019)) lag the even cycle terminators  by ~ 2.3 normalized years.  The average interval between each minimum and terminator  is thus relatively extended for odd cycles and shortened for even ones. We re-engineer the R27 index that was orignally proposed by Sargent(1985) to parameterize 27 day recurrences in the aa index. We perform an epoch analysis of autocovariance in the aa index using the Hale cycle clock to obtain a high time resolution parameter for 27 day recurrence, <acv(27)>. This reveals that the transition to recurrence, that is, to an ordered solar wind dominated by high speed streams, is fast, occurring within 2-3 solar rotations or less. It resolves an extended late declining phase which is approximately twice as long on even Schwabe cycles as odd ones. We find that Galactic Cosmic Ray flux rises in step with <acv(27)> but then stays high. Our analysis also identifies a slow timescale trend in SSN that simply tracks the Gleissberg cycle. We find that this trend is in phase with the slow timescale trend in the modulus of sunspot latitudes, and in antiphase with that of the R27 index.</p>

ESTABLISHING SOLAR ACTIVITY TREND FOR SOLAR CYCLES 21 – 24

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.

Cosmic Ray Modulation with the Maximum CME Speed Index During Solar Cycles 23 and 24

Solar Physics ◽  
2019 ◽  
Vol 294 (7) ◽  
Author(s):  
Volkan Sarp ◽  
Ali Kilcik ◽  
Vasyl Yurchyshyn ◽  
Atila Ozguc ◽  
Jean-Pierre Rozelot
Keyword(s):  
Cosmic Ray ◽  
Solar Cycles ◽  
Cosmic Ray Modulation
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