故事-太阳上也有季节变化

The Sun undergoes a type of seasonal^{1 variability with its activity waxing and waning2 over the course of nearly two years, according to a new study by a team of researchers led by the National Center for Atmospheric3 Research . This behavior affects the peaks and valleys in the approximately 11-year solar cycle, sometimes amplifying4 and sometimes weakening the solar storms that can buffet5 Earths atmosphere. The quasi-annual variations appear to be driven by changes in the bands of strong magnetic fields in each solar hemisphere. These bands also help shape the approximately 11-year solar cycle that is part of a longer cycle that lasts about 22 years.}

What were looking at here is a massive driver of solar storms, said Scott McIntosh, lead author of the new study and director of NCARs High Altitude Observatory^{6. By better understanding how these activity bands form in the Sun and cause seasonal instabilities, theres the potential to greatly improve forecasts of space weather events.}

The overlapping^{7 bands are fueled by the rotation8 of the Suns deep interior, according to observations by the research team. As the bands move within the Suns northern and southern hemispheres, activity rises to a peak over a period of about 11 months and then begins to wane9.}

The quasi-annual variations can be likened to regions on Earth that have two seasons, such as a rainy season and a dry season, McIntosh said.

The study, published this week in Nature Communications, can help lead to better predictions of massive geomagnetic storms in Earths outer atmosphere that sometimes disrupt satellite operations, communications, power grids^{10, and other technologies.}

The research was funded by NASA and the National Science Foundation, which is NCARs sponsor.