Like tropical countries having two seasons, that is rainy and dry season, the sun has been experiencing a two-year seasonal variability that intensifies and recedes, caused by solar magnetic activity band interaction and instabilities.
According to the study of researchers at the National Center for Atmospheric Research (NCAR), the cycle is superimposed on the enigmatic and more familiar 11-year sunspot cycle affecting its peaks and valleys.
The overlapping activity bands are powered by the revolving of the deep interior drives of the sun. As the magnetic bands shift inside the sun's southern and northern hemispheres, activity goes up to a peak of approximately 11 months and afterwards it starts to wane.
"What we're looking at here is a massive driver of solar storms. 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," Scott McIntosh, NCAR's High Altitude Observatory director and lead author of the study, said.
McIntosh, together with his affiliates, noticed the warped, ring-shaped solar magnetic bands by picture on ground-based observatories and a group of National Aeronautics and Space Administration (NASA) satellites that collect information on solar flares' nature, coronal mass ejection (CME) and the structure of the sun.
"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," added co-author Robert Leamon from Montana State University.
Leamon also explained that sometimes these bands result in leaks to other bands in terms of magnetic fields and, in other instances, the warp pulls the magnetic fields starting from the bottom of the area of solar interior, close to the tachocline then finally pushes them just before the surface.
In line with this discovery, the authors concluded that migrating magnetic bands produces quasi-annual variations that are as powerful as the more known 11-year equivalent cycle. These variations are happening independently in both the sun's southern and northern hemispheres.
McIntosh believes that by understanding solar activity patterns, it will be easy to know whether the sun's hemispheres will be in stormy or quiet phases.
Published in Nature Communications, McIntosh concluded that this research can lead to new developments in the forecasting of geomagnetic storms in the Earth's outer atmosphere, which has direct effects on our communications, satellite, power grid and other technologies.
Photo: NASA Goddard Space Flight Center | Flickr
