The Presence of Turbulent and Ordered Local Structure within the ICME Shock-sheath and Its Contribution to Forbush Decrease

作者：Shaikh Zubair; Raghav Anil^*; Bhaskar Ankush

来源：Astrophysical Journal, 2017, 844(2): 121.

DOI：10.3847/1538-4357/aa729f

• Sun: coronal mass ejection (CME)
• cosmic rays
• magnetic fields
• solar wind
• ISM: structure
• turbulence

The transient interplanetary disturbances evoke short-time cosmic-ray. flux decrease, which is known as Forbush decrease. The traditional model and understanding of Forbush decrease suggest that the sub-structure of an interplanetary counterpart of coronal mass ejection (ICME) independently contributes to cosmic-ray flux decrease. These sub-structures, shock-sheath, and magnetic cloud (MC) manifest as classical two-step Forbush decrease. The recent work by Raghav et al. has shown multi-step decreases and recoveries within the. shock-sheath. However, this cannot be explained by the. ideal shock-sheath barrier model. Furthermore, they suggested that local structures within the ICME's sub-structure (MC and shock-sheath) could explain this deviation of the. FD profile from the classical FD. Therefore, the present study attempts to investigate the cause of multi-step cosmic-ray flux decrease and respective recovery within the. shock-sheath in detail. A. 3D-hodogram method is utilized to obtain. more details regarding. the local structures within the shock-sheath. This method unambiguously suggests the formation of small-scale local structures within the ICME (shock-sheath and even in MC). Moreover, the method could differentiate the turbulent and ordered interplanetary magnetic field (IMF) regions within the sub-structures of ICME. The study explicitly suggests that the turbulent and ordered IMF regions within the shock-sheath do influence cosmic-ray variations differently.

• 出版日期2017-8-1