Application of diffusion — Convection model to diurnal anisotropy data

Mavromichalaki, H.

doi:10.1007/bf00056331

Cited by 17 publications

(11 citation statements)

References 21 publications

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“…At higher frequencies the diurnal variation (T = 1 day) is dominant and is caused by corotation of cosmic-ray particles in the interplanetary magnetic field (Axford, 1965;Mavromichalaki, 1989). Within these two extreme frequency ranges a wide range of frequencies of cosmic-ray intensity variations exists, although a clear, stable and selective periodicity has not been established so far.…”

Section: Introductionmentioning

confidence: 99%

“…It is interesting to note that the established 1.7-year variation of cosmic-rays has also appeared at the top of flareproducing regions for the period 1972-1989(McIntosh, 1992, as well as in the long duration event (LDE)-type of flares which precede the formation of coronal holes during the 20th and 21st cycles (Antalovà, 1994;Mavromichalaki et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Low- and high-frequency spectral behavior of cosmic-ray intensity for the period 1953–1996

et al. 2003

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Abstract.A study of the cosmic-ray intensity power spectrum using the Climax Neutron Monitor data in the frequency range from 10 −9 Hz to 10 −7 Hz (which corresponds to periodicities from 11 years to a few months) during the period 1953-1996, was carried out by means of the successive approximations method of analysis and was compared against the power spectrum and the maximum entropy methods. The contributions of the time evolution of several peaks to the global one were obtained. Except for the well-known 11-year and the 1-year variations, peaks at 7.7, 5.5, 2 and 1.7 years are found. Several peaks with periods less than 10 months have appeared in our analysis, while the occurrence of 5.1 months is obtained in all the examined solar cycles with a strong signature in cycle 21. Transitions of these quasiperiodicities are seen in power spectra plots. Some of them can be attributed to the modulation of the cosmic ray intensity by solar activity. Others are sporadic and have been previously attributed to the interplanetary magnetic field. The results obtained support once again the argument regarding the difference in the solar activity between odd and even solar cycles.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low- and high-frequency spectral behavior of cosmic-ray intensity for the period 1953–1996

et al. 2003

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“…That mechanism relates the solar diurnal anisotropy of cosmic rays to the dynamics of the solar wind and interplanetary magnetic field. The fieldaligned directions of the diffusive vector, independent of the interplanetary magnetic field polarity, have been confirmed [6]. In general, the solar diurnal anisotropy is caused by the modulation of the galactic cosmic rays in the heliosphere [7], [8].…”

Section: Introductionmentioning

confidence: 63%

Diurnal Variation of Cosmic Ray Intensity at Different Group of Geomagnetic Index (Ap)

Dubey¹,

Chudhary²,

Singh³

et al. 2017

IJASS

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Abstract:The solar modulation of Galactic Cosmic Rays (GCR) is revealed in the record of neutron monitors in terms of daily variation. Day-to-day and long term basis daily variations have been investigated for the recent period from 1965 to 2015 along with geomagnetic disruption index Ap on twelve-monthly average basis. Here Ap index has been used as a placeholder for the solar bring on interplanetary disturbances. It is create that, in general on an annual average basis, both the diurnal amplitude as well as the diurnal phase is considerably lower in the years of low Ap values, through the period 1965 to 2015. Such as a result was also informed for the earlier periods. However, anomalous and determined results for the diurnal variations have been received when the daily values of Ap are diffused in five groups with the first group demonstrating low Ap condition (i.e. quite periods) and the last group naturally representing the disturbed conditions.

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“…10), a FD took place in 11 May 2005 and was recorded with a reversal of the diurnal vectors and a shift to later hours, resulting in strong fluctuations and loops, likely due to the convective-diffusive mechanism (Mavromichalaki, 1989;Tezari and Mavromichalaki, 2016). This behavior is similar for all studied NMs.…”

Section: Diurnal Anisotropy During Strong Cosmic Ray Eventsmentioning

confidence: 69%

“…The calculated diurnal vectors of the cosmic ray intensity according to Eqs. (1), (2), (3), and (4) for the selected stations are presented on a harmonic dial on a yearly and monthly basis (Mavromichalaki, 1989;Tezari and Mavromichalaki, 2016;Mavromichalaki et al, 2016) using simple vector calculus and the newly developed DIAS software. The length of the vector represents the diurnal amplitude, while the vector's direction is equivalent to the time of maximum.…”

Section: Discussionmentioning

confidence: 99%

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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Application of diffusion — Convection model to diurnal anisotropy data

Cited by 17 publications

References 21 publications

Low- and high-frequency spectral behavior of cosmic-ray intensity for the period 1953–1996

Low- and high-frequency spectral behavior of cosmic-ray intensity for the period 1953–1996

Diurnal Variation of Cosmic Ray Intensity at Different Group of Geomagnetic Index (Ap)

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

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