Once a century: Gigantic bursts of solar radiation much more frequent

Gigantic eruptions on stars like our sun are apparently much more frequent than previously assumed; these superflares may occur about once every hundred years. This has been determined by a research group led by the Max Planck Institute for Solar System Research (MPS). While historical data on the sun has primarily been evaluated for such analyses to date, the team has instead focused on sun-like stars. From their behavior, it can be concluded that the immense radiation outbursts with potentially devastating consequences for our infrastructure are ten to a hundred times more frequent than previously assumed.

Much stronger than the strongest storm in the recent past

According to the research institute, so-called superflares release amounts of energy in the quadrillions of joules within a very short space of time. This corresponds to the amount of trillions of hydrogen bombs. To make this more understandable, the team also writes that during one of the most violent solar storms of the past centuries, the so-called Carrington Event of 1859, only one hundredth of the energy of a superflares was released. In view of our infrastructure, which is now much more susceptible to such events, it is particularly important to be able to accurately estimate their frequency.

The team therefore examined measurement data on 56,450 sun-like stars collected by NASA's Kepler space telescope. Short, very intense brightness peaks would have revealed superflares in these stars. These were found in exactly 2889 out of 2527 of these stars. This leads to the conclusion that a sun-like star suffers about one superflare per century. This was very surprising, says study leader Valeriy Vasilyev. At the same time, he and his team point out that, in their opinion, this is the most precise and sensitive study of the phenomenon to date. In view of the findings, they emphasize the importance of reliable and timely prediction.

Few examples known from solar history

Until now, the frequency of these gigantic eruptions in our sun has been studied using "natural archives" such as tree rings or glacial ice. These contain traces of particles that reach the atmosphere after such an eruption. Several such eruptions have been dated using this method, the most recent result was presented just a few weeks ago. Vasilyev's team now points out that this could only be a small subset. It is not at all clear whether the superflares are always accompanied by such a particle storm. Further research is needed here.

Three years ago, a researcher pointed out that strong solar flares could have dramatic consequences for the world's internet infrastructure and trigger an "internet apocalypse". This danger has been underestimated to date because the most recent strong solar storms occurred decades before the advent of modern technology. The risk is particularly high for submarine cables at high latitudes, especially those between Europe and the USA. In the event of a severe solar storm, this connection could fail for months. At the same time, the study now presented in the journal Science suggests that the potential strength of such eruptions has actually been underestimated.

(mho)