Modeling and data analysis of a Forbush decrease

Wawrzyńczak, A.; Alania, M. V.

doi:10.1016/j.asr.2009.09.005

Cited by 57 publications

(51 citation statements)

References 33 publications

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“…Mean value of α for the phase of decrease is about -0.72±0.43, for the phase of minimum about -0.91±0.36, and for the phase of recovery about -0.90±0.51 (RMS deviations are indicated). From the obtained distributions, a conclusion follows that no significant difference between α values for different FD phases is observed, in contradiction with results [7].…”

Section: Results Of Studying Of Fd Characteristics In Muon Fluxcontrasting

confidence: 55%

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Study of characteristics of Forbush decreases detected in 2006 – 2011 by means of muon hodoscope URAGAN

Barbashina¹,

Астапов²,

Borog³

et al. 2013

J. Phys.: Conf. Ser.

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Abstract.Results of the study of variations of cosmic ray muon flux at the Earth surface during Forbush decreases (FD) registered in 2006 -2011 by means of muon hodoscope URAGAN both for the integral counting rate and for different angular intervals are presented. Dependences of the amplitude of the decrease of cosmic ray muon intensity on the energy of primary particles in the energy region above 10 GeV during different phases of the FD were obtained. On the basis of the analysis of spatial-angular distribution of muon flux, values of the horizontal projections of the local anisotropy vector were calculated and their dynamics was studied. Energy, angular and temporal characteristics of Forbush decreases determined from cosmic ray muon data are compared with basic parameters characterizing conditions of nearEarth space before and during FD.

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Section: Results Of Studying Of Fd Characteristics In Muon Fluxcontrasting

confidence: 55%

“…A similar study using data of neutron monitors and a muon telescope was carried out earlier [7]. The index of the energy spectrum of decreases was estimated from the URAGAN data with increments of 40-60 minutes.…”

Section: Methods Of Fd Analysis In the Flux Of Muons Registered In Thementioning

confidence: 99%

Study of characteristics of Forbush decreases detected in 2006 – 2011 by means of muon hodoscope URAGAN

Barbashina¹,

Астапов²,

Borog³

et al. 2013

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

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“…This relationship is expected owing to the dependence of the diffusion coefficient K of GCR particles on the rigidity R, K ∝ R α ; here the coefficient α depends on the exponent ν of the PSD of the IMF turbulence according to the quasi-linear theory (QLT) as α = 2 -ν (Jokipii, 1966(Jokipii, , 1971Hasselman and Wibberentz, 1968;Toptygin, 1985). As was shown by Wawrzynczak and Alania (2005a, 2005b, Wawrzynczak (2008, 2012), and Alania, Iskra, andSiluszyk (2008, 2010), the exponent γ is related to α. Namely, γ ≈ 2 -ν in the range of frequency of the IMF turbulence f ≈ ∼ 10 −6 -10 −5 Hz, to which the neutron monitors and muon telescopes respond. The validity of the QLT (Jokipii, 1966(Jokipii, , 1971 for the GCR particles with energy ≥ 1 GeV is confirmed by the weakly nonlinear theory (WNLT; Shalchi et al, 2004), nonlinear parallel diffusion theory (NLPA; Qin, 2007) and by Droge (2003), Shalchi andSchlickeiser (2004), andShalchi (2009).…”

Section: Introductionmentioning

confidence: 97%

“…However, to study the rigidity dependence of Fd based only on the rigidity spectrum taken at one time point is not sufficient to understand its dynamics. The time evolution of the rigidity spectrum of the Fd was studied by Wawrzynczak (2008, 2012) and by Wawrzynczak and Alania (2005a, 2005b. They showed that the rigidity spectrum δD(R)/D(R) ∝ R −γ of the great majority of Fds gradually becomes hard during the decreasing and minimum phases and then gradually becomes soft in the recovery phase.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the exponent γ of the rigidity spectrum is large (γ ≈ 1 − 1.6) at the initial phase, gradually decreases up to the minimum (or near minimum) of GCR intensity (γ ≈ 0.4 -0.6), and then increases during the recovery phase (γ ≈ 1 -1.6). Wawrzynczak and Alania (2005a, 2005b and Wawrzynczak (2008, 2012) have shown that the temporal changes in the exponent γ of the rigidity spectrum of the Fds found by neutron monitors and muon telescopes are related to the changes in the power spectral density (PSD) of the IMF turbulence (PSD ∝ f −ν , here f is the frequency). This relationship is expected owing to the dependence of the diffusion coefficient K of GCR particles on the rigidity R, K ∝ R α ; here the coefficient α depends on the exponent ν of the PSD of the IMF turbulence according to the quasi-linear theory (QLT) as α = 2 -ν (Jokipii, 1966(Jokipii, , 1971Hasselman and Wibberentz, 1968;Toptygin, 1985).…”

Section: Introductionmentioning

confidence: 99%

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Temporal Changes in the Rigidity Spectrum of Forbush Decreases Based on Neutron Monitor Data

et al. 2013

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The Forbush decrease (Fd) of the Galactic cosmic ray (GCR) intensity and disturbances in the Earth's magnetic field generally take place simultaneously and are caused by the same phenomenon, namely a coronal mass ejection (CME) or a shock wave created after violent processes in the solar atmosphere. The magnetic cut-off rigidity of the Earth's magnetic field changes because of the disturbances, leading to additional changes in the GCR intensity observed by neutron monitors and muon telescopes. Therefore, one may expect distortion in the temporal changes in the power-law exponent of the rigidity spectrum calculated from neutron monitor data without correcting for the changes in the cut-off rigidity of the Earth's magnetic field. We compare temporal changes in the rigidity spectrum of Fds calculated from neutron monitor data corrected and uncorrected for the geomagnetic disturbances. We show some differences in the power-law exponent of the rigidity spectrum of Fds, particularly during large disturbances of the cut-off rigidity of the Earth's magnetic field. However, the general features of the temporal changes in the rigidity spectrum of Fds remain valid as they were found in our previous study. Namely, at the initial phase of the Fd, the rigidity spectrum is relatively soft and it gradually becomes hard up to the time of the minimum level of the GCR intensity. Then during the recovery phase of the Fd, the rigidity spectrum gradually becomes soft. This confirms that the structural changes of the interplan- etary magnetic field turbulence in the range of frequencies of 10 −6 -10 −5 Hz are generally responsible for the time variations in the rigidity spectrum we found during the Fds.

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Peculiarities of cosmic ray modulation in the solar minimum 23/24

2014

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We study changes of the galactic cosmic ray (GCR) intensity for the ending period of the solar cycle 23 and the beginning of the solar cycle 24 using neutron monitors experimental data. We show that an increase of the GCR intensity in 2009 is generally related with decrease of the solar wind velocity U, the strength B of the interplanetary magnetic field (IMF), and the drift in negative (A < 0) polarity epoch. We present that temporal changes of rigidity dependence of the GCR intensity variation, before reaching maximum level in 2009 and after it, do not noticeably differ from each other. The rigidity spectrum of the GCR intensity variations calculated based on neutron monitors data (for rigidities > 10 GV) is hard in the minimum and near-minimum epoch. We do not recognize any nonordinary changes in the physical mechanism of modulation of the GCR intensity in the rigidity range of GCR particles to which neutron monitors respond. We compose 2-D nonstationary model of transport equation to describe variations of the GCR intensity for 1996-2012 including the A > 0 (1996-2001) and the A < 0 (2002-2012) periods; diffusion coefficient of cosmic rays for rigidity 10-15 GV is increased by~30% in 2009 (A < 0) comparing with 1996 (A > 0). We believe that the proposed model is relatively realistic, and obtained results are satisfactorily compatible with neutron monitors data.

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Modeling and data analysis of a Forbush decrease

Cited by 57 publications

References 33 publications

Study of characteristics of Forbush decreases detected in 2006 – 2011 by means of muon hodoscope URAGAN

Study of characteristics of Forbush decreases detected in 2006 – 2011 by means of muon hodoscope URAGAN

Temporal Changes in the Rigidity Spectrum of Forbush Decreases Based on Neutron Monitor Data

Peculiarities of cosmic ray modulation in the solar minimum 23/24

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