Anomalous Forbush Effects from Remote by Longitude Solar Sources

E. Eroshenko¹, A. Belov¹, H. Mavromichalaki², V. Oleneva¹, A. Papaioannou², V. Yanke¹

¹Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS (IZMIRAN), 142190, Troitsk, Moscow region, Russia
²Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimiopolis, Zografos GR-15783, Athens, Greece

By the data from neutron monitor network and relevant data from satellite observations a set of Forbush effects occurred on the background of relatively quiet interplanetary and geomagnetic conditions (IMF< 15 nT, Kp< 5+) and associated with the far western and eastern events on the Sun has been studied. These Forbush effects can be referred to a special sub-class of events, and incorporated by the common conditions: absence of a significant disturbance in the Earth vicinity; absence of the strong geomagnetic storm; absence of the fast decrease of cosmic ray intensity during the main phase of Forbush effect. The general features and separate properties in behavior of the cosmic ray density and anisotropy for this subclass are investigated. Despite of similar background and similarly remote sources Forbush effects from eastern and western sources reveal significant difference in their profiles and in variations of cosmic ray density and anisotropy. The events of both these groups (from eastern and western sources) show unusually weak decrement of a decrease of cosmic ray intensity during the main phase of Forbush effect.