The average distance from the Sun to the Earth is 150 million kilometers. A coronal mass ejection (CME) can vary in speed. The typical speed is 424 km/s, but they can range from 200 km/s to 1000 km/s. Using the numbers above we can compute the minimum travel time, the maximum and the average. The average time it takes for a CME to reach earth is 98 hrs. For the faster CMEs it would take 42 hours and for the slower moving ones it would take 208 hours.

Hi, You have just asked one of the most important questions for the Space Weather effects of the solar flares and CMEs (coronal mass ejections). Some solar flares are eruptive and some are not. When a flare is eruptive, a CME will be sent out to leave the Sun. At this point of time, it is still difficult to calculate when a CME will reach the Earth when an eruption occurs. So we take images of CMEs and measure the speeds of CMEs, which provide a good idea of how quickly they will reach the Earth. But there will still be complications on the way to Earth from Sun, CMEs can be accelerated or decelerated by the solar wind. Scientists are getting better and better at predicting the arrival time of CMEs. Yan