scholarly journals Cosmic ray recovery and solar minimum phase of solar cycle 22: An interim report

1998 ◽  
Vol 103 (A1) ◽  
pp. 373-379 ◽  
Author(s):  
Frank B. McDonald ◽  
Nand Lal ◽  
Robert E. McGuire
Keyword(s):  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Minimum Phase ◽  
Interim Report

Implications of the cosmic-ray radial intensity gradients observed during minimum solar modulation

1968 ◽  
Vol 46 (10) ◽  
pp. S946-S949 ◽  
Author(s):  
J. J. O'Gallagher
Keyword(s):  
Diffusion Coefficient ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Solar Modulation ◽  
Space Probe ◽  
Magnetic Rigidity ◽  
A Value ◽  
Particle Parameters ◽  
Gradient Measurements

We have already reported the cosmic-ray radial intensity gradients for both protons and helium nuclei measured over two decades in Rβ (magnetic rigidity R times velocity β) on the Mariner IV space probe in 1965 which showed that the modulating function is separable into the product of a function of particle parameters and a function of the time t and the heliocentric radius r for the observations (O'Gallagher and Simpson 1967). The modulating function can be written as exp (−η(r, t)/ƒ(R, β)) where η(r, t) is the modulating parameter and ƒ(R, β) = Rβ for [Formula: see text] and ƒ(R, β) [Formula: see text] β for [Formula: see text]. The magnitude of the observed gradient corresponds to a change Δη = −0.2 ± 0.05 GV for Δr = 0.4 AU and at 1 GV yields a value for the diffusion coefficient in Parker's model of 3.2 × 1021 cm/s. If the value of η in 1965 is small [Formula: see text], the observed value of Δη/Δr implies that the greatest part of the modulation takes place within 5 AU at solar minimum. The value of Δη; derived from these gradient measurements is compared with estimates of the change in η required to produce the observed time–intensity variations during the solar cycle.

scholarly journals Features of the Galactic Cosmic Ray Anisotropy in Solar Cycle 24 and Solar Minima 23/24 and 24/25

Solar Physics ◽  
2019 ◽  
Vol 294 (10) ◽  
Author(s):  
R. Modzelewska ◽  
K. Iskra ◽  
W. Wozniak ◽  
M. Siluszyk ◽  
M. V. Alania
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Radial Component ◽  
Galactic Cosmic Rays ◽  
Positive Polarity ◽  
Heliospheric Magnetic Field ◽  
Solar Cycle 24 ◽  
Cycle 24

Abstract We study the role of the drift effect in the temporal changes of the anisotropy of galactic cosmic rays (GCRs) and the influence of the sector structure of the heliospheric magnetic field on it. We analyze the GCR anisotropy in Solar Cycle 24 and solar minimum 23/24 with negative polarity ($qA<0$qA<0) for the period of 2007 – 2009 and near minimum 24/25 with positive polarity ($qA>0$qA>0) in 2017 – 2018 using data of the global network of Neutron Monitors. We use the harmonic analysis method to calculate the radial and tangential components of the anisotropy of GCRs for different sectors (‘+’ corresponds to the positive and ‘−’ to the negative directions) of the heliospheric magnetic field. We compare the analysis of GCR anisotropy using different evaluations of the mean GCRs rigidity related to Neutron Monitor observations. Then the radial and tangential components are used for characterizing the GCR modulation in the heliosphere. We show that in the solar minimum 23/24 in 2007 – 2009 when $qA<0$qA<0, the drift effect is not visibly evident in the changes of the radial component, i.e. the drift effect is found to produce $\approx 4$≈4% change in the radial component of the GCR anisotropy for 2007 – 2009. Hence the diffusion dominated model of GCR transport is more acceptable in 2007 – 2009. In turn, near the solar minimum 24/25 in 2017 – 2018 when $qA>0$qA>0, the drift effect is evidently visible and produces ≈40% change in the radial component of the GCR anisotropy for 2017 – 2018. So in the period of 2017 – 2018 a diffusion model with noticeably manifested drift is acceptable. The results of this work are in good agreement with the drift theory of GCR modulation, according to which, during negative (positive) polarity cycles, a drift stream of GCRs is directed toward (away from) the Sun, thus giving rise to a 22-year cycle variation of the radial GCR anisotropy.

scholarly journals One-Day-Shock, Two-Days-Shock and Three-Days-Shocks foF2 Diurnal Variation with Solar Cycle Phases at Ouagadougou Station from 1966 to 1998. Comparison with IRI 2012 Predictions

2019 ◽  
Vol 12 (1) ◽  
pp. 38
Author(s):  
Abdoul-kader SEGDA ◽  
Doua Allain GNABAHOU ◽  
Frédéric OUATTARA
Keyword(s):  
Solar Cycle ◽  
Time Variation ◽  
Solar Minimum ◽  
The Other ◽  
Cycle Phase ◽  
Minimum Phase ◽  
Solar Cycles ◽  
Night Time ◽  
Maximum Phase ◽  
Phase Dependence

The present work concerns foF2 time variation at Ouagadougou station for three solar cycles (from cycle 20 to cycle 22). We not only investigate solar cycle phase dependence under shock activity that is divided into one-shock-activity, two-shock-activity and three-shock-activity but also compare the IRI 2012 model values with the data carried out at Ouagadougou station. This study reveals that there is no one-day-shock during solar minimum phase. For the other solar cycle phases IRI 2012 reproduces the ionosphere electrodynamics at daytime except during the increasing phase. During night time the model is not suitable. The best subroutine under one-day-shock activity is URSI for increasing and decreasing phases. During the maximum phase it is CCIR. For two-days-shock activity IRI 2012 reproduces the ionosphere electrodynamics during the minimum and the increasing phases. The best subroutine is CCIR during the minimum phase and URSI for the other solar cycle phases. For three-days-shock activity IRI 2012 is not suitable. The best model is URSI for all solar cycle phases.

scholarly journals Measurements of the time-dependent cosmic-ray Sun shadow with seven years of IceCube data: Comparison with the Solar cycle and magnetic field models

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
M. G. Aartsen ◽  
R. Abbasi ◽  
M. Ackermann ◽  
J. Adams ◽  
J. A. Aguilar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Time Dependent ◽  
Data Comparison

Solar-cycle phenomena in cosmic-ray intensity: Differences between even and odd cycles

1988 ◽  
Vol 42 (3) ◽  
pp. 233-244 ◽  
Author(s):  
H. Mavromichalaki ◽  
E. Marmatsouri ◽  
A. Vassilaki
Keyword(s):  
Solar Cycle ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Odd Cycles

scholarly journals Measurement of Low-Energy Cosmic-Ray Antiprotons at Solar Minimum

1998 ◽  
Vol 81 (19) ◽  
pp. 4052-4055 ◽  
Author(s):  
H. Matsunaga ◽  
S. Orito ◽  
H. Matsumoto ◽  
K. Yoshimura ◽  
A. Moiseev ◽  
...  
Keyword(s):  
Solar Minimum ◽  
Cosmic Ray ◽  
Low Energy

scholarly journals Successive measurements of cosmic-ray antiproton spectrum in a positive phase of the solar cycle

2001 ◽  
Vol 16 (2) ◽  
pp. 121-128 ◽  
Author(s):  
T. Maeno ◽  
S. Orito ◽  
H. Matsunaga ◽  
K. Abe ◽  
K. Anraku ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Cosmic Ray ◽  
Positive Phase

scholarly journals Extremely low geomagnetic activity during the recent deep solar cycle minimum

2011 ◽  
Vol 7 (S286) ◽  
pp. 200-209 ◽  
Author(s):  
E. Echer ◽  
B. T. Tsurutani ◽  
W. D. Gonzalez
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Solar Wind Speed ◽  
Sunspot Cycle ◽  
Cycle Minimum ◽  
Current Minimum ◽  
Solar Wind Parameters ◽  
Xix Century

AbstractThe recent solar minimum (2008-2009) was extreme in several aspects: the sunspot number, Rz, interplanetary magnetic field (IMF) magnitude Bo and solar wind speed Vsw were the lowest during the space era. Furthermore, the variance of the IMF southward Bz component was low. As a consequence of these exceedingly low solar wind parameters, there was a minimum in the energy transfer from solar wind to the magnetosphere, and the geomagnetic activity ap index reached extremely low levels. The minimum in geomagnetic activity was delayed in relation to sunspot cycle minimum. We compare the solar wind and geomagnetic activity observed in this recent minimum with previous solar cycle values during the space era (1964-2010). Moreover, the geomagnetic activity conditions during the current minimum are compared with long term variability during the period of available geomagnetic observations. The extremely low geomagnetic activity observed in this solar minimum was previously recorded only at the end of XIX century and at the beginning of the XX century, and this might be related to the Gleissberg (80-100 years) solar cycle.

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.

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