http://www.google.com/search?q=1859+carrington+event is a good link for additional information on the impact of coronal mass ejections (CME).

The Earth's magnetic field is strong enough to neutralize the effects of most CMEs; however, a CME event on the order of magnitude of the 1859 Carrington event would be catastrophic, not immediately to life on the planet but to the grid, as was the case in 1859; though at the time only rudimentary telegraph lines were operational, not modern electronics and computers powered by a centralized grid. When we lose the grid's transformers, our modern civilization will quickly become a distant memory.