Cosmic ray modulation in high and middle latitudes during solar cycles 22 and 23

Okpala, Kingsley Chukwudi; Okeke, F. N.; Ugwuoke, Anselem Ikechukwu

doi:10.1139/cjp-2014-0290

Cited by 3 publications

(5 citation statements)

References 15 publications

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“…They suggested that the modulation of galactic cosmic rays should have a significant component controlled by the state of the interplanetary magnetic fields as they are transported out from the sun and hence there should be a solar cycle effect on the drift of the cosmic rays in the heliosphere. This was corroborated recently by many other studies (Chillingarian and Mailyan, 2009;Okpala et al, 2015;Kudela and Sabbah, 2016). Recently, Thomas et al (2017) studied the diurnal variation of cosmic rays using decadal data.…”

Section: Solar Modulation Of Cosmic Rayssupporting

confidence: 60%

Variability of quiet-time diurnal amplitude and phase of cosmic ray count rates in the mid- and high latitudes

Ugochukwu¹,

Kingsley²,

James³

et al. 2017

Int. J. Phys. Sci.

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Studies have been done on the variability of cosmic rays flux during solar quiet days at mid and high latitudes. By using the 5 quietest days for each month, the monthly mean diurnal variation of cosmic ray anisotropy have been derived for the period 1981 to 2007, which covers part of cycles 21, 22 and 23. These quiet days are days during which the sun is relatively magnetically quiet, leading to less anisotropic behaviour in the diurnal flux of cosmic rays measured on the earth surface. Four stations (Rome, Oulu, Inuvik and Thule) were used in this study to understand the important features of the high latitude and mid-latitude diurnal wave, and how solar and geomagnetic activity may be influencing the wave characteristics. Cosmic ray wave characteristics were obtained by discrete Fourier transform (DFT). The mean, diurnal amplitude, phase and dispersion for each month's diurnal wave were calculated and profiled. There was clear indication that the terrestrial effect on the variability of the monthly mean of Cosmic ray count rates was more associated with geomagnetic activity rather than rigidity of the cosmic rays. Correlation of the time series of these wave characteristics (that is, amplitude and phase) with solar and geomagnetic activity index showed better association with solar activity.

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Section: Solar Modulation Of Cosmic Rayssupporting

confidence: 60%

Variability of quiet-time diurnal amplitude and phase of cosmic ray count rates in the mid- and high latitudes

Ugochukwu¹,

Kingsley²,

James³

et al. 2017

Int. J. Phys. Sci.

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“…In addition, the large difference during the rising phase of cycle 24 and near its peak is a reflection of the dependence of the flux on the geomagnetic disturbance which may also be related to the solar activity. Solar activity correlates well with geomagnetic activity since they are intricately connected (Okpala et al 2014), hence observation here is an indication of the indirect effect of solar activity on the CR flux especially on the observed association between Ap index and CR flux (see Table 3) [13].…”

Section: Heliospheric Modulation Of Gcr (During Quiet Days)supporting

confidence: 54%

“…Among such researchers include [3][4][5][6][7][8][9][10]. The simple harmonic analysis of the diurnal variation of CR has been applied by authors such as [11,12,9,6,10] and their linear association with different drivers investigated by a few works [13].…”

Section: Introductionmentioning

confidence: 99%

“…These modulations vary with varying solar activities, however, during shorter time scales, CR are modulated in the heliosphere primarily by the globally merged interaction region with intense magnetic fields. Okpala et al established that the interplanetary magnetic field was the most dominant modulating parameter especially during quiet conditions, and the solar wind dynamic pressure was more effective during the disturbed conditions [13]. The solar modulation of CR intensity has been extensively investigated in the past by using the data of ground based detectors in association with various solar, interplanetary and geomagnetic parameters [17,18].…”

Section: Introductionmentioning

confidence: 99%

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Heliospheric Modulation of GCR at Mid and High Latitudes

Okpala¹,

Kalu²,

Achu³

2020

PSIJ

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The variations of Galactic Cosmic Ray (GCR) as compared with the behaviour of various solar activity indices, heliospheric parameters and the geomagnetic index Ap during 1999-2015, which covers part of cycles 23 and cycle 24 have been studied. Two sets of data were considered, consisting respectively of all days of the month and the five quietest days. Neutron Monitor Stations of Moscow and Rome (mid latitude stations) and Inuvik and Oulu (High latitude stations) were employed. Cosmic Ray (CR) wave characteristics were obtained by the harmonics method. The mean, diurnal amplitude of the first, second, and third harmonics were calculated and profiled. Furthermore, correlation analysis was carried out to determine the association between parameters. Results showed that the total magnetic field BT and the sunspot number (SSN) showed the strongest association with CR in both quiet conditions and all day conditions considered. The higher harmonics showed a slightly stronger association with CR than lower harmonics. A time-lag of about 12-15 months was observed for SSN suggesting a potential for predicting CR flux, while the total magnetic field had a zero lag for all the heliospheric parameters considered.

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“…Mishra and Mishra (2007) showed that sunspot numbers and coronal index showed better correlation with cosmic ray intensity during negative polarity than positive polarity of the solar magnetic cycle. Okpala et al (2015), analyzed the effect of some solar wind components on the count rates under different interplanetary magnetic field (IMF) disturbance levels and observed different roles for dynamic pressure and B z component of IMF.…”

Section: Introductionmentioning

confidence: 99%

On the slow-time geomagnetic field modulation of cosmic rays

Friday¹,

Chukwudi²

2019

Int. J. Phys. Sci.

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In this work, monthly means of cosmic ray count rates from two mid latitude (Hermanus and Rome), and two higher latitude (Inuvik and Oulu) neutron monitors (NM) were employed and their variability was compared with geomagnetic stations that are in close proximity to the NMs. The data spans 1966 to 2008 and covers four solar cycles. The difference (CRdiff) between the mean count rate of all days and the mean of the five quietest days for each month was compared with the Dst-related disturbance (Hdiff) derived from the nearby geomagnetic stations. Zeroth-and First-correlation between the cosmic ray parameters and geomagnetic parameters was performed to ascertain statistical association and test for spurious association. The present results show that solar activity is generally strongly correlated (>0.75) with mean strength of GCR count rate and geomagnetic field during individual solar cycles. The correlation between mean strength of cosmic ray intensity and geomagnetic field strength is spurious and is basically moderated by the solar activity. The signature of convection driven disturbances at high latitude geomagnetic stations was evident during the declining phase of the solar cycles close to the solar minimums. The absence of this feature in the slow-time varying cosmic ray count rates in all stations and in the mid latitude geomagnetic stations suggests that the local geomagnetic disturbance do not play a significant role in modulating the cosmic ray flux.

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Cosmic ray modulation in high and middle latitudes during solar cycles 22 and 23

Cited by 3 publications

References 15 publications

Variability of quiet-time diurnal amplitude and phase of cosmic ray count rates in the mid- and high latitudes

Variability of quiet-time diurnal amplitude and phase of cosmic ray count rates in the mid- and high latitudes

Heliospheric Modulation of GCR at Mid and High Latitudes

On the slow-time geomagnetic field modulation of cosmic rays

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