Statistical study of co-rotating interaction region properties with STEREO and ACE observations

Abstract

We analyzed the data on co-rotating interaction regions (CIRs) measured by the Advanced Composition Explorer (ACE) and Solar TErrestrial RElations Observatory (STEREO) from 2007 to 2010. The CIRs were observed by STEREO B (STB), ACE and STEREO A (STA) one after another, and a total of 28 CIRs were identified in this work. Since the same characteristics of CIRs were detected by these three spacecraft at three different locations and times, these data can help us to study the evolutions of CIRs. For a single event, the properties of CIRs observed by the three spacecraft were quite different and could be explained by spatial or temporal variations. For all these 28 CIRs, STA and STB observed similar mean parameters, such as peak magnetic field strength (offset 11%), peak and change in solar wind speed (offset 3% and 10% respectively), peak proton temperature (offset 14%) and peak perpendicular pressure (offset 15%). Surprisingly, STA detected much higher (41%) peak density of protons than STB.