On the 27-day variations of the galactic cosmic ray anisotropy and intensity for different periods of solar magnetic cycle

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

doi:10.1016/j.asr.2005.03.018

Cited by 27 publications

(28 citation statements)

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“…short or long period variations). Vernova et al (2003), Alania et al (2005), and Gil et al (2005) demonstrated that the amplitudes of the 27-day variation of the GCR intensity do not depend on the tilt angle (TA) of the HCS. Therefore, we can consider the HCS as a plane with TA = 0, i.e., the heliosphere is divided into two symmetric parts (hemispheres) by the HCS coinciding with the Sun's equatorial plane.…”

Section: Model Of the 27-day Variation Of The Gcr Intensity; Results mentioning

confidence: 99%

Theoretical and Experimental Studies of the Rigidity Spectrum of the 27-Day Variation of the Galactic Cosmic Ray Intensity in Different Epochs of Solar Activity

Gil

Alania

2012

Sol Phys

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We consider the recent, very exceptional, 11-year cycle (2003 -2009) of solar activity and confirm that the relative amplitude in rigidity spectrum, δD(R)/D(R), which can be approximated by a power law in rigidity R, of the first three harmonics of the 27-day variation of the galactic cosmic ray (GCR) intensity is hard in the maximum and soft in the minimum epochs of solar activity, as was found by neutron monitor data for the period of 1965 -2002. This property is seen not only in separate minimum and maximum epochs but in individual intervals of a solar Carrington rotation as well: There exist many individual intervals of solar rotation when the expected rigidity spectrum of the 27-day variation of the GCR intensity indeed is hard in the maximum epoch of solar activity and is soft in the minimum epoch. We then construct a three-dimensional model of the 27-day variation of the GCR intensity based on Parker's transport equation, by implementing in situ measurements of the changes in heliographic longitude of the solar wind velocity and interplanetary magnetic field for different epochs of solar activity.Keywords 27-days variation of the galactic cosmic rays intensity · Epochs of solar activity · Rigidity spectrum

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Section: Model Of the 27-day Variation Of The Gcr Intensity; Results mentioning

confidence: 99%

Theoretical and Experimental Studies of the Rigidity Spectrum of the 27-Day Variation of the Galactic Cosmic Ray Intensity in Different Epochs of Solar Activity

Gil

Alania

2012

Sol Phys

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“…where H is the Heaviside step function changing the sign of the global magnetic field in each hemisphere, Subsequent papers (Alania et al, 2001b;Alania et al, 2005;Gil et al, 2005) show the results that the amplitudes of the 27-day variations of the GCR intensity and anisotropy do not depend on the tilt angles of the HNS during the 11-year cycle of solar activity. It is acceptable to use the planar HNS in modeling of the 27-day variation of the GCR intensity.…”

Section: Model Of the 27-day Variation Of The Gcr Intensity And Its Nmentioning

confidence: 99%

“…Previously, Alania et al, (2001aAlania et al, ( , 2001b; Gil and Alania (2001); Vernova et al, (2003); Iskra et al, (2004) demonstrated that the amplitudes of the 27-day variation of the GCR intensity obtained from neutron monitors are greater in the minimum epochs of solar activity for A>0 than for A<0. Recently, we demonstrated Modzelewska 2008a, 2008b;Gil et al, 2005) that also the amplitudes of the 27-day variation of the GCR anisotropy at solar minimum are greater when A>0 than when A<0. Many of the papers (Gil and Alania, 2001;Burger and Hitge, 2004;Alania et al, 2005;Gil et al, 2005;Modzelewska 2008a, 2008b;Burger et al, 2008) aimed to explain a dependence of the 27-day variation of the cosmic ray intensity on the A>0 and A<0 polarity epochs in terms of drift effect for the same heliolongitudinal changes of the solar wind velocity in different polarity epochs.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we demonstrated Modzelewska 2008a, 2008b;Gil et al, 2005) that also the amplitudes of the 27-day variation of the GCR anisotropy at solar minimum are greater when A>0 than when A<0. Many of the papers (Gil and Alania, 2001;Burger and Hitge, 2004;Alania et al, 2005;Gil et al, 2005;Modzelewska 2008a, 2008b;Burger et al, 2008) aimed to explain a dependence of the 27-day variation of the cosmic ray intensity on the A>0 and A<0 polarity epochs in terms of drift effect for the same heliolongitudinal changes of the solar wind velocity in different polarity epochs. At the same time, the role of different ranges of the heliolongitudinal changes of the solar wind velocity in the A>0 and A<0 epochs was not considered.…”

Section: Introductionmentioning

confidence: 99%

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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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“…The structure is more complex during the long time period. Transport models (Gil et al, 2005) and measurements analyzed in paper (Richardson, 2004) suggest the dependence on solar magnetic field polarity. Vivek Gupta and Badruddin, (2009) found that the average behavior of GCR-oscillations during Carrington rotation is different in A > 0 from that in A < 0 epoch.…”

Section: Periodic and Quasi-periodic Variationsmentioning

confidence: 99%

Variability of Low Energy Cosmic Rays Near Earth

Kudela¹

2012

Exploring the Solar Wind

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On the 27-day variations of the galactic cosmic ray anisotropy and intensity for different periods of solar magnetic cycle

Cited by 27 publications

References 5 publications

Theoretical and Experimental Studies of the Rigidity Spectrum of the 27-Day Variation of the Galactic Cosmic Ray Intensity in Different Epochs of Solar Activity

Theoretical and Experimental Studies of the Rigidity Spectrum of the 27-Day Variation of the Galactic Cosmic Ray Intensity in Different Epochs of Solar Activity

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

Variability of Low Energy Cosmic Rays Near Earth

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