Interplanetary Shocks Observed from Multipoints at Venus and 1 au

We present a database of 12 fast forward interplanetary (IP) shocks observed in situ by radially aligned spacecraft (Venus Express, Wind, and/or STEREO) between 2006 and 2014. By analyzing shock magnetic compression ratios at different heliocentric distances, which serve as a common proxy for shock strength, we found that five events displayed a decrease in shock strength from Venus (at ∼0.72 au) to 1 au, five events showed no significant change within measurement uncertainties, and two events showed an increase near 1 au compared to Venus. Events that exhibited increased compression with distance may reflect specific interplanetary conditions that influence shock propagation and evolution. To investigate the causes of shock strengthening, we conducted a detailed case study of the 2011 March 18–21 shock event using a combination of multipoint remote-sensing and in situ observations. The analysis indicated that both the shock and its associated interplanetary coronal mass ejection (ICME) accelerated during their propagation, likely playing a major role in enhancing magnetic compression across the shock and contributing to the increased shock strength near 1 au. These findings highlight the importance of ICME kinematics in driving shock evolution in the inner heliosphere. The multi-spacecraft shock database compiled in this study also provides a valuable foundation for characterizing the radial evolution of IP shocks throughout the inner heliosphere.