Study of the 27-day variations of the galactic cosmic ray intensity and anisotropy

Alania, M. V.; Gil, Agnieszka; Modzelewska, Renata

doi:10.1016/j.asr.2007.06.001

Cited by 22 publications

(40 citation statements)

References 8 publications

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“…1 presents for the first NMs and for all combining NMs by GSM. We confirm our previous finding [6] that near the solar minimum the amplitudes of the 27-day variations of the 2D GCR anisotropy determined using GSM basically do not differ from the amplitudes found by harmonic analysis for an individual NM with cut-off rigidity < 5 GV. Figure 1 shows that this feature is kept for the whole solar cycle and solar magnetic cycle.…”

Section: Long Term Changes Of the 27-day Variation Of The Gcr Anisotropysupporting

confidence: 91%

“…The time lines of the 27-day variation of the 2D GCR anisotropy confirm that the average amplitude in the minimum epoch of solar activity is polarity dependent, as it is expected from the drift theory. The amplitude in the negative polarity epochs is less as we had shown before [6]. The feeble 11-year variation connected with solar cycle and strong 22-year pattern connected with solar magnetic cycle is visible in the 27-day variation of the 2D anisotropy for 1965-2014.…”

Section: Long Term Changes Of the 27-day Variation Of The Gcr Anisotropymentioning

confidence: 49%

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27-day Variation of the Three Dimensional Solar Anisotropy of Galactic Cosmic Ray: 1965-2014.

Modzelewska¹

2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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The temporal evaluation of the 27-day variation of the three dimensional (3D) galactic cosmic ray (GCR) anisotropy has been studied for 1965-2014. 3D anisotropy vector was obtained based on the neutron monitors and Nagoya muon telescopes data. We analyze the 27-day variation of the (1) two dimensional (2D) GCR anisotropy in the ecliptic plane, and (2) north-south anisotropy normal to the ecliptic plane. Studying the time line of the 27-day variation of the 2D GCR anisotropy, we confirm that the average amplitude in the minimum epoch of solar activity is polarity dependent, as it is expected from the drift theory. The amplitude in the negative polarity epochs is less as we had shown before. The feeble 11-year variation connected with solar cycle and strong 22-year pattern connected with solar magnetic cycle is visible in the 27-day variation of the 2D anisotropy for 1965-2014. We show that the 27-day variation of the GG index (being a measure of the north-south asymmetry) varies in accordance to solar cycle with a period of 11-years, being in good agreement with the 27-day variation of the At component of the GCR anisotropy calculated by the IZMIRAN group. Detailed analysis are presented for the solar minimum 2007-2008 of solar cycle no.23 and solar maximum 2013-2015 of solar cycle no 24. In the solar cycle no. 24 GG index, calculated by Nagoya telescopes data, is highly anticorrelated with By component of the interplanetary magnetic field (IMF) and shows a clear recurrent changes related to the Sun's rotation.

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Section: Long Term Changes Of the 27-day Variation Of The Gcr Anisotropysupporting

confidence: 91%

Section: Long Term Changes Of the 27-day Variation Of The Gcr Anisotropymentioning

confidence: 49%

27-day Variation of the Three Dimensional Solar Anisotropy of Galactic Cosmic Ray: 1965-2014.

Modzelewska¹

2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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“…3-D models developed by Kota and Jokipii (1983; show that in the global modulation model of GCR , the large-scale structure is controlled by drift effects in conjunction with diffusion, convection and energy change, but the small-scale structure is caused by diffusive effects in the transient and corotating structures. Alania, Gil and Modzelewska (2008a), Gil, Alania and Modzelewska (2008) demonstrated that for the polarity dependent amplitudes of the 27-day variations of the GCR intensity are responsible, among the equally important drift effects, the heliolongitudinally dependent solar wind velocity with various ranges in the A>0 and A<0 polarity epochs. We showed (Alania, Modzelewska and Wawrzynczak, 2010) that to explain features of the 27-day variation of the GCR intensity by three dimensional (3-D) modelling, there should be taken into account a consistent, divergence-free IMF derived from Maxwell's equations with the heliolongitudinally dependent solar wind velocity reproducing in situ observations.…”

Section: Introductionmentioning

confidence: 99%

On the Relationship of the 27-day Variations of the Solar Wind Velocity and Galactic Cosmic Ray Intensity in Minimum Epoch of Solar Activity

2011

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We study the relationship of the 27-day variation of the galactic cosmic ray intensity with similar changes of the solar wind velocity and the interplanetary magnetic field based on the experimental data for the Bartels rotation period # 2379 of 23 November 2007 -19 December 2007. We develop a three dimensional (3-D) model of the 27-day variation of galactic cosmic ray intensity based on the heliolongitudinally dependent solar wind velocity. A consistent, divergence-free interplanetary magnetic field is derived by solving Maxwell's equations with a heliolongitudinally dependent 27-day variation of the solar wind velocity reproducing in situ observations. We consider two types of 3-D models of the 27-day variation of galactic cosmic ray intensity -(1) with a plane heliospheric neutral sheet, and (2)-with the sector structure of the interplanetary magnetic field. The theoretical calculation shows that the sector structure does not influence significantly on the 27-day variation of galactic cosmic ray intensity as it was shown before based on the experimental data. Also a good agreement is found between the time profiles of the theoretically expected and experimentally obtained first harmonic waves of the 27-day variation of the galactic cosmic ray intensity (correlation coefficient equals 0.98 ± 0.02). The expected 27-day variation of the galactic cosmic ray intensity is inversely correlated with the modulation parameter ζ (correlation coefficient equals -0.91 ± 0.05) which is proportional to the product of the solar wind velocity V and the strength of the interplanetary magnetic field B (ζ~ VB). The high anticorrelation between these quantities indicates that the predictable 27-day variation of the galactic cosmic ray intensity mainly is caused by this basic modulation effect.

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“…It partially is connected with the complexity of the reliable revealing of the 27-day variation of the GCR anisotropy by means of small amplitudes of the diurnal variations of GCR (< 0.3%, measured by NMs), and with a large dispersion of the amplitudes of diurnal variation comparable with the accuracy of hourly data of NMs. In papers Alania et al, [7], [18] studied the 27-day variation of the 2D GCR anisotropy in the ecliptic plane. They demonstrated that the average amplitude in the minimum epoch of solar activity is polarity dependent, as it is expected from the drift theory.…”

Section: -Day Wave In Gcr Anisotropy Near the Solar Minimum 23/24: mentioning

confidence: 99%

Three dimensional solar anisotropy of galactic cosmic rays near the recent solar minimum 23/24

Modzelewska

Alania

2015

J. Phys.: Conf. Ser.

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Three dimensional (3D) galactic cosmic ray (GCR) anisotropy has been studied for 2006-2012. The GCR anisotropy, both in the ecliptic plane and in polar direction, were obtained based on the neutron monitors (NMs) and Nagoya muon telescopes (MT) data. We analyze two dimensional (2D) GCR anisotropy in the ecliptic plane and north-south anisotropy normal to the ecliptic plane. We reveal quasi-periodicities -the annual and 27-days waves in the GCR anisotropy in 2006-2012. We investigate the relationship of the 27-day variation of the GCR anisotropy in the ecliptic plane and in the polar direction with the parameters of solar activity and solar wind.

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Study of the 27-day variations of the galactic cosmic ray intensity and anisotropy

Cited by 22 publications

References 8 publications

27-day Variation of the Three Dimensional Solar Anisotropy of Galactic Cosmic Ray: 1965-2014.

27-day Variation of the Three Dimensional Solar Anisotropy of Galactic Cosmic Ray: 1965-2014.

On the Relationship of the 27-day Variations of the Solar Wind Velocity and Galactic Cosmic Ray Intensity in Minimum Epoch of Solar Activity

Three dimensional solar anisotropy of galactic cosmic rays near the recent solar minimum 23/24

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