Solar magnetic polarity dependency of the cosmic ray diurnal variation

Sabbah, I.

doi:10.1002/jgra.50431

Cited by 15 publications

(12 citation statements)

References 19 publications

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“…The first component is dominant at high-latitude NMs and is controlled by drift effects, while both of them are important for middle-and low-latitude stations. This is consistent with the results of Bieber and Chen (1991), Oh et al (2010), andSabbah (2013) at lower energies, as well as with the recent results at higher cut-off rigidities and even at muon telescopes (Kudela and Sabbah, 2016). Athens shows the largest phase variation, as it has the highest threshold rigidity (Bieber and Chen, 1991).…”

Section: Diurnal Anisotropy During the Solar Cyclesupporting

confidence: 92%

“…Then, the annual average diurnal amplitude increases again during the ascending phase of SC 24. Consequently, the amplitude of the diurnal anisotropy displays a clear 11-year sunspot cycle variation, with minima occurring on or near sunspot minimum and maxima near sunspot maximums (Bieber and Chen, 1991;Tiwari et al, 2005Tiwari et al, , 2012Sabbah, 2013). A small increase in diurnal amplitude is observed during 2005, due to various events, such as coronal mass ejections (CMEs) and magnetic storms.…”

Section: Diurnal Anisotropy During the Solar Cyclementioning

confidence: 99%

“…The diurnal variation is due to complex phenomena, deriving from the convective-diffusive theory, which involves the radial convection of GCR flux by the solar wind and the inward diffusion along the interplanetary magnetic field (IMF) (Parker, 1964;Rao, 1972;Forman and Gleeson, 1975;Sabbah, 2013). An energy-independent anisotropic flow of CR particles in the 18 h co-rotational direction is generated due to the equilibrium between the convection and diffusion mechanisms (Krymsky, 1964;Rao, 1972;Mishra and Mishra, 2008).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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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.

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Section: Diurnal Anisotropy During the Solar Cyclesupporting

confidence: 92%

Section: Diurnal Anisotropy During the Solar Cyclementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…Oh, Yi, and Bieber (2010) found that the higher energy NMs contribute more to the 11 year phase variation of GCR anisotropy due to the diffusion process. Sabbah (2013) reported that the diurnal phase of higher energy NMs shifts towards earliest hours; this is connected with outward convection by SW, which increases the radial component of the daily variation more than the azimuthal component.…”

Section: Introductionmentioning

confidence: 96%

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

Modzelewska

Iskra

Wozniak³

et al. 2019

Sol Phys

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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) for the period of 2007-2009 and near minimum 24/25 with positive polarity (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, the drift effect is not visibly evident in the changes of the radial component, i.e. the drift effect is found to produce ≈ 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, 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.

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“…Singh et al (2011) examining data of neutron monitor stations, situated in different latitudes, found a significant diurnal phase shift to earlier hours in the ascending periods of odd solar cycles (21 and 23) in comparison to the diurnal phase in the ascending periods of even solar cycles (20 and 22). Recently Sabbah (2013) showed that there is dependence of the cosmic ray diurnal variation from the solar magnetic field polarity for all the time period 1953 to 2011. 3.…”

Section: Discussionmentioning

confidence: 99%

Solar cycle and 27-day variations of the diurnal anisotropy of cosmic rays during the solar cycle 23

Mavromichalaki

Papageorgiou

Gerontidou

2016

Astrophys Space Sci

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The diurnal anisotropy of cosmic-ray intensity observed over the period [1997][1998][1999][2000][2001][2002][2003][2004][2005][2006], which coincides with the solar cycle 23, has been analyzed using cosmic ray data from Athens and Oulu neutron monitor stations. In this analysis it was observed that the time of the diurnal variation maximum shifted to earlier hours than the corotation direction from 1997 to 2000, where the polarity state of the magnetic field was positive (qA > 0) and to later hours from 2001 to 2006 where the polarity state was negative (qA < 0).Moreover the 27-day variation of the cosmic-ray diurnal anisotropy in connection with the 27-day variation of the interplanetary magnetic field has been studied. In this study six groups of ten Bartel rotations each one have been analyzed (). It is remarkable that the 27-day variation of cosmic-ray intensity is characterized by the well known sector structure and it is well correlated with the B XY component of the interplanetary magnetic field. These findings during the last solar cycle confirm once again the close relation of the diurnal variation of cosmic ray intensity and the interplanetary magnetic field.

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Solar magnetic polarity dependency of the cosmic ray diurnal variation

Cited by 15 publications

References 19 publications

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

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

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

Solar cycle and 27-day variations of the diurnal anisotropy of cosmic rays during the solar cycle 23

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