CME / magnetic cloud propagation through the solar wind

MHD simulations of CME propagation in the solar wind will be performed. Dynamic adaptive grid refinement techniques will be used. CMEs will be generated as described above and their propagation in numerically obtained solar wind solutions  $^{\hbox{\scriptsize [FOM3-FOM5]}}$ will be studied. The dependence of the time-of-arrival on initial CME speed and ambient solar wind speed, the interaction with sector boundaries and corotating interaction regions, and the evolution of the out-of-the-ecliptic component of the magnetic field during propagation are points of interest ^[10-13]. Contrary to what one might expect, observations show that the transit time for a CME to travel to 1 AU is roughly 80 hours and independent of the CME velocity observed near the Sun. This will be investigated in the simulations.

The formation of shock fronts induced by fast CMEs propagating with super-Alfvénic speeds will be investigated in detail. It will especially be interesting to see whether multiple interacting shock fronts of various MHD shock types can be formed $^{\hbox{\scriptsize [KUL2-KUL5]}}$. The formation of slow shocks induced by sub-Alfvénic CMEs will also be studied ^[7]. It is important to study how shock properties change when the plasma $\beta$ changes during the propagation and when critical points are passed.

This part of the project requires comparison with LASCO observations. In addition, radio observations may be crucial for the identification and study of the CME related MHD shock interactions $^{\hbox{\scriptsize [DASOP5]}}$. In-situ satellite observations of the structure of magnetic clouds at 1 AU will be compared with the resulting structure of CMEs after propagation to 1 AU $^{\hbox{\scriptsize [BIRA4]}, [14]}$. The CME propagation simulations from the Sun outward will be compared with in- and out-of-ecliptic satellite observations (Wind, ULYSSES). Simulations of CME propagation between 1 and 5 AU for particularly favorable satellite configurations, like Wind-ULYSSES radial or longitudinal alignments will be compared with observations^[15].

Solar energetic particle (SEP) events in the interplanetary medium sometimes accompany a CME. The accelerated particles are an important diagnostic of the CME evolution and its interaction with the ambient solar wind. The origin of the solar energetic proton events, observed in the Earth's vicinity, will be checked by tracing back the energetic particles to the Sun using the global inner heliospheric magnetic field obtained from the MHD simulations. The energetic particles arriving at the orbit of SOHO are detected as the ‘snow storm’ of cosmic ray hits on the LASCO and EIT CCD detectors. The current, widely accepted paradigm is that impulsive and gradual SEP events are of different origin: impulsive events being flare associated and gradual events being associated with fast CMEs that drive interplanetary shocks .