Quantitative understanding of Forbush decrease drivers based on shock-only and CME-only models using global signature of February 14, 1978 event

Journal Article · Wed Oct 01 04:00:00 EDT 2014 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2014/10/074· OSTI ID:22375782

Raghav, Anil; Lotekar, Ajay ^[1]; Bhaskar, Ankush; Vichare, Geeta; Yadav, Virendra ^[2]

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1. University Department of Physics, University of Mumbai, Vidyanagari, Santacruz (E), Mumbai-400098 (India)
2. Indian Institute of Geomagnetism, Plot 5, Sector 18, New Panvel, Navi Mumbai-410218 (India)

We have studied the Forbush decrease (FD) event that occurred on February 14, 1978 using 43 neutron monitor observatories to understand the global signature of FD. We have studied rigidity dependence of shock amplitude and total FD amplitude. We have found almost the same power law index for both shock phase amplitude and total FD amplitude. Local time variation of shock phase amplitude and maximum depression time of FD have been investigated which indicate possible effect of shock/CME orientation. We have analyzed rigidity dependence of time constants of two phase recovery. Time constants of slow component of recovery phase show rigidity dependence and imply possible effect of diffusion. Solar wind speed was observed to be well correlated with slow component of FD recovery phase. This indicates solar wind speed as possible driver of recovery phase. To investigate the contribution of interplanetary drivers, shock and CME in FD, we have used shock-only and CME-only models. We have applied these models separately to shock phase and main phase amplitudes respectively. This confirms presently accepted physical scenario that the first step of FD is due to propagating shock barrier and second step is due to flux rope of CME/magnetic cloud.

• OSTI ID: 22375782
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 10 Vol. 2014; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTRONOMY AND ASTROPHYSICS
AMPLITUDES
FORBUSH DECREASE
MATERIALS RECOVERY
NEUTRON MONITORS
SOLAR WIND
TRITIUM RECOVERY
VARIATIONS
VELOCITY