Cataloging Stream Interaction Regions at MAVEN: A Cross-comparative Study with STEREO-A

Abstract

Stream interaction regions (SIRs) are long-lasting solar wind structures that result from stable fast solar wind interacting with preceding slow solar wind. These structures have been examined in depth throughout the heliosphere, particularly at 1 au; however, due to sparse observations, SIRs have not been characterized thoroughly at 1.5 au. Thanks to the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we have a chance to fill this observational gap. We implement in situ solar wind data collected by MAVEN to identify SIRs between 2014 November and 2023 September. We observe 185 SIRs with average durations of 2.2 days that occur primarily during periods of low solar activity. We detect 19 forward shocks, seven reverse shocks, and one shock pair within these 185 SIRs. We predict a total SIR-associated shock detection rate of ∼56% at 1.5 au and compare this rate to previous findings spanning 0.1–5 au. We examine Solar Terrestrial Relations Observatory (STEREO) A data at 1 au to cross-compare with our results at 1.5 au. We determine the magnetic compression ratios (H) associated with SIRs at MAVEN and STEREO-A and find that H is ∼18% higher at 1.5 au than 1 au. We find that for a given SIR observed at both 1 and 1.5 au, H is ∼32% higher at 1.5 au. We also do not see a stark difference in the change in H for SIRs observed at both STEREO-A and MAVEN with respect to the angular separation of the spacecraft.