Multi-point Shock and Flux Rope Analysis of Multiple Interplanetary Coronal Mass Ejections around 2010 August 1 in the Inner Heliosphere
Liu, Y.; Luhmann, J. G.; Webb, D. F.; Forsyth, R.; Zhang, T. L.; Möstl, C.; Farrugia, C. J.; Kilpua, E. K. J.; Jian, L. K.; Eastwood, J. P.; Harrison, R. A.; Temmer, M.; Odstrcil, D.; Davies, J. A.; Rollett, T.; Nitta, N.; Mulligan, T.; Jensen, E. A.; Lavraud, B.; de Koning, C. A.; Veronig, A. M.; Galvin, A. B.; Anderson, B. J.
United States, Austria, Finland, China, United Kingdom, France
Abstract
We present multi-point in situ observations of a complex sequence of coronal mass ejections (CMEs) which may serve as a benchmark event for numerical and empirical space weather prediction models. On 2010 August 1, instruments on various space missions, Solar Dynamics Observatory/Solar and Heliospheric Observatory/Solar-TErrestrial-RElations-Observatory (SDO/SOHO/STEREO), monitored several CMEs originating within tens of degrees from the solar disk center. We compare their imprints on four widely separated locations, spanning 120° in heliospheric longitude, with radial distances from the Sun ranging from MESSENGER (0.38 AU) to Venus Express (VEX, at 0.72 AU) to Wind, ACE, and ARTEMIS near Earth and STEREO-B close to 1 AU. Calculating shock and flux rope parameters at each location points to a non-spherical shape of the shock, and shows the global configuration of the interplanetary coronal mass ejections (ICMEs), which have interacted, but do not seem to have merged. VEX and STEREO-B observed similar magnetic flux ropes (MFRs), in contrast to structures at Wind. The geomagnetic storm was intense, reaching two minima in the Dst index (≈ - 100 nT), and was caused by the sheath region behind the shock and one of two observed MFRs. MESSENGER received a glancing blow of the ICMEs, and the events missed STEREO-A entirely. The observations demonstrate how sympathetic solar eruptions may immerse at least 1/3 of the heliosphere in the ecliptic with their distinct plasma and magnetic field signatures. We also emphasize the difficulties in linking the local views derived from single-spacecraft observations to a consistent global picture, pointing to possible alterations from the classical picture of ICMEs.