Sunstorm: Arthur C. Clarke and Stephen Baxter

Time Odyssey II; the sequel to Time's Eye. 2037. The sun flares. Thousands die. Suddenly, our high-tech civilisation seems terribly vulnerable. We recover. We rebuild. But this is just the precursor. In April 2042 - in just five years - the sun will flare out again. But this time, the sun will hurl out in one day the energy it would normally spend in a year. This time, nothing on Earth will survive. As plans are drawn up to save Mankind, as all Earth's resources are mobilised for one unimaginable engineering effort, one question remains unanswered: why now? https://cosmiccauldronbooks.com.au/p/times-eye-arthur-c-clarke-and-stephen-baxter/