Análise da variabilidade de raios cósmicos galácticos devido a estruturas solares no meio interplanetário

Abstract

Measurements by ground based detectors of Secondary Cosmic Rays Intensity, from primary Galactic Cosmic Rays – GCR, shown several variations series caused by terrestrials and extraterrestrials effects, both of which can be periodic and sporadic. Among the causes of terrestrials and extraterrestrials variations are solar structures in the interplanetary medium and their associated shocks. When interplanetary solar structures hit the Earth, besides of possible geomagnetic storms, isotropic decreases of Cosmic Rays are observed, called Forbush Decreases. The Forbush Decrease is characterized by an intensity decrease of Cosmic Rays behind the shock. Certain kinds of decreases are observed before Forbush Decreases and are said to be anisotropic precursors related with kinetic effects due the interaction of Cosmic rays with the approaching shock. For study isotropic and anisotropic variability of GCRs due to solar structures in the interplanetary medium are utilized data observed by the Multidirectional Muon Detector, MMD, located at Southern Space Observatory SSO/CRS/CCR/INPE – MCT (29.4°S, 53.8°W, 480 m a.s.l.) São Martinho da Serra, Brasil, RS, and by the MMD at Nagoya, Japan. For the identification of solar structures in the interplanetary medium data tables related to structures earlier observed were used, analyzing them with data of plasma and interplanetary magnetic field observed by the spacecraft ACE of NASA. For the inspections of geomagnetic storms the Geomagnetic index Dst (Disturbance Storm Time) were used. The results shown the existence of Forbush Decreases in the isotropy Galactic Cosmic Rays, with energy equal or greater than 50GeV, it also was occasionally observed anisotropic decrease like the Loss Cone Precursor.