New research suggests the Sun undergoes seasonal changes over a quasi-annual period.
The Sun's activity was found to wax and wane over a period of two years, the National Center for Atmospheric Research (NCAR) reported. These changed are believed to be triggered by magnetic bands in the solar atmosphere, which also influence the 11-year solar cycle that is part of a longer 22-year one.
"What we're looking at here is a massive driver of solar storms," said Scott McIntosh, lead author of the new study and director of NCAR's High Altitude Observatory. "By better understanding how these activity bands form in the Sun and cause seasonal instabilities, there's the potential to greatly improve forecasts of space weather events."
The overlapping bands are created by the rotation of the Sun's interior. As these bands move within the Sun's northern and southern hemispheres, solar activity rises over a period of around 11 months before falling again.
The researchers made their findings by looking at NASA satellites and ground-based observatories that analyze the Sun's structure and events such as solar flares and coronal mass ejections (CMEs). The data showed the magnetic fuel rises from the solar interior through an atmospheric transition zone known as the tachocline, and is linked to variations in flares and CMEs.
"Much like Earth's jet stream, whose warps and waves have had severe impact on our regional weather patterns in the past couple of winters, the bands on the Sun have very slow-moving waves that can expand and warp it too," said co-author Robert Leamon, a scientist at Montana State University. "Sometimes this results in magnetic fields leaking from one band to the other. In other cases, the warp drags magnetic fields from deep in the solar interior, near the tachocline, and pushes them toward the surface."
The rises in magnetic fuel are believed to destabilize the corona, which leads to catastrophic solar storms.
"These surges or 'whomps' as we have dubbed them, are responsible for over 95 percent of the large flares and CMEs-the ones that are really devastating," McIntosh said.
The findings were published in a recent edition of the journal Nature Communications.
