SUN-TO-EARTH ANALYSIS

During the interval 7-11 March 2012 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant Ultra-Low Frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the magnetosphere were observed. These phenomena were ultimately associated to two ultra-fast (> 2000 km s−1) Coronal Mass Ejections (CMEs), linked to two X-class flares launched on early 7 March 2012. Given that both powerful events originated from solar active region NOAA 11429 and their onsets were separated by less than an hour, the analysis of the two events and the determination of solar causes and geospace effects are rather challenging. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions a synergistic Sun-to-Earth study of diverse observational solar, InterPlanetary (IP) and magnetospheric datasets was performed. It was found that only the second CME was Earth-directed. Using a novel method, we estimated its near-Sun magnetic field at 13 R to be in the range [0.01,0.16] G. Steep radial fall-offs of the near-Sun CME magnetic field are required to match the magnetic fields of the corresponding Interplanetary CME (ICME) at 1 AU. Perturbed upstream solar wind conditions, as resulting fro