Investigation of the transient cosmic ray decreases observed by voyagers in 2007: A numerical approach

In 2006 and 2007, Voyager 1 and 2 recorded a series of cosmic ray transient decrease events. It is believed that these transient decrease events are caused by the Local Merged Interaction Region (LMIR). Incorporating a LMIR model with our cosmic ray transport code, we investigate the causes for these cosmic ray transient decrease events. The simulation shows that the interaction between LMIR and termination shock (TS) affect the cosmic ray transport in the heliosheath, even if the observed location is beyond latitude extent of the LMIR. To further understand these transient decrease events observed by voyagers, we simulate a scenario of two LMIRs propagating into the heliosheath. One of the LMIRs arrived at Voyager 2 at 2007.43 and the other at 2007.55. They went further to interact with the TS at 2007.56 and 2007.76 separately, causing the cosmic ray intensity decreases observed by Voyager 1 which was about 10 AU beyond the TS.