Local-time-dependent pre-IMF-shock decrease and post-shock increase of cosmic rays, produced respectively by their IMF-collimated outward and inward flows across the shock responsible for forbush decrease

Nagashima, K.; Fujimoto, K.; Sakakibara, S.; Morishita, I.; Tatsuoka, R.

doi:10.1016/0032-0633(92)90040-u

Cited by 42 publications

(28 citation statements)

References 23 publications

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“…The criteria for selecting events was the presence at least one SSC. We did not adopt any criteria of minimum Kp index, as done in previous studies [1,5,6].…”

Section: Objective and Methodologiesmentioning

confidence: 99%

“…Nagashima et al [5] suggested the existence of local time dependent precursory decrease of cosmic ray (muon) intensity in front of a shock during the morning (6-12h) and post-shock increase during the evening (18-24h). It was concluded that the precursory decrease is produced by the IMF-collimated outward flow of the low-density cosmic rays from the region behind the shock.…”

Section: Introductionmentioning

confidence: 99%

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Cosmic ray modulation associated to small and moderate geomagnetic storms during minimum solar activity

Braga¹

2011

Proceedings of 4th School on Cosmic Rays and Astrophysics — PoS(CRA School)

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Inhomogeneities in the interplanetary magnetic field produced by interplanetary disturbances associated with coronal mass ejections are transmitted fast to remote locations as a directional anisotropy of high-energy cosmic ray intensity due to the high speed and long parallel mean free path of energetic particles. Cosmic ray intensity increases or decreases before the Forbush decreases have been observed with a single directional channel especially for strong geomagnetic storms associated with strong interplanetary shocks. The aim of this work is to study cosmic ray precursory phenomena of small and moderate geomagnetic storms from June 26th 2008 to December 31st 2008 (from Bartels rotation number 2387 to 2393), most of them not associated with shocks, by analyzing data from the Global Muon Detector Network consisting of four multidirectional muon detectors. By analyzing muon count rates in 60 directional channels, the pitch angle distribution in a 48-hour period before the storm sudden commencement was studied by two different methodologies: one using the hourly count rate (MPA) and the other using the time derivative of the count rate (VPA). Possible precursors are clear in 4 of the 7 events registered in the selected period, generally observed by the MPA. 4th School on Cosmic Rays and Astrophysics

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“…The criteria for selecting events was the presence at least one SSC. We did not adopt any criteria of minimum Kp index, as done in previous studies [1,5,6].…”

Section: Objective and Methodologiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cosmic ray modulation associated to small and moderate geomagnetic storms during minimum solar activity

Braga¹

2011

Proceedings of 4th School on Cosmic Rays and Astrophysics — PoS(CRA School)

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“…Nagashima et al (1992) show that the storm is frequently accompanied by non-diffusion-convection-type phenomena, depending on local time, as precursory decrease of CR at the front of the shock in the morning hours of local time, and a post-shock increase different from the diurnal variation. FDs are analyzed by global spectrographic method using worldwide network of NMs (e.g.…”

Section: Irregular Variationsmentioning

confidence: 96%

“…The characteristics of CMEs in the inner heliosphere are discussed in detail by (Gopalswamy, 2004). One of the first papers suggesting that the solar cycle dependent modulation of GCR can be explained by CMEs and by related IMF inhomegeneities in the heliosphere was that by (Newkirk et al, 1981). Correlation of CR intensity and CME ocurrence at a single NM with high geomagnetic cut-off is reported e.g.…”

Section: Irregular Variationsmentioning

confidence: 99%

Variability of Low Energy Cosmic Rays Near Earth

Kudela¹

2012

Exploring the Solar Wind

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“…A separate line of research has been undertaken by Nagashima and colleagues [5]. They have studied anisotropies (obtained from neutron monitor data) related to particle effects at shocks and in particular decrease and increase caused by density gradient flows across the shock.…”

Section: Introductionmentioning

confidence: 99%

Cosmic ray intensity during the passage of coronal mass ejections

Mishra¹,

Agarwal²

2008

Braz. J. Phys.

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Coronal Mass Ejections are vast structures of plasma and magnetic fields that are expelled from the sun into the heliosphere. This material is detected by remote sensing and in-situ spacecraft observations. The present study deals with the influence of four types of CMEs namely Asymmetric 'Full' Halo CMEs, Partial Halo CMEs, Asymmetric and Complex 'Full' Halo CMEs and 'Full' Halo CMEs on cosmic ray neutron monitor intensity. The data of ground based neutron monitor of Moscow and CME events observed with instruments onboard and Wind spacecraft have been used in the present analysis. The method of superposed epoch (Chree) analysis has been used to the arrival times of these CMEs. It is noteworthy that the frequency of occurrence of Asymmetric 'Full' Halo CMEs is significantly high, whereas frequency of occurrence of Asymmetric and Complex 'Full' Halo CMEs is low compared to other CMEs. Significant enhancement in cosmic ray intensity is observed after 4 days of the onset of asymmetric full halo and 6 days after the onset of full halo CMEs. The fluctuations in cosmic ray intensity are more prior to the onset of both types of the CMEs. However, during Partial Halo CMEs the cosmic ray intensity peaks, 8-9 days prior to the onset of CMEs and depressed 3 days prior to the onset of CMEs, whereas in case of asymmetric and complex full CMEs, the intensity depressed 2 days prior to the onset of CMEs and enhanced 2 days after the onset of CMEs. The deviations in cosmic ray intensity are more pronounced in case for asymmetric and complex full halo CMEs compared to other CMEs.

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Local-time-dependent pre-IMF-shock decrease and post-shock increase of cosmic rays, produced respectively by their IMF-collimated outward and inward flows across the shock responsible for forbush decrease

Cited by 42 publications

References 23 publications

Cosmic ray modulation associated to small and moderate geomagnetic storms during minimum solar activity

Cosmic ray modulation associated to small and moderate geomagnetic storms during minimum solar activity

Variability of Low Energy Cosmic Rays Near Earth

Cosmic ray intensity during the passage of coronal mass ejections

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