New research has revealed the Sun undergoes a type of seasonal variability with its activity waxing and waning over the course of nearly two years.

The study by a team of researchers led by the National Center for Atmospheric Research (NCAR) explains how 'seasonal' changes could help researchers better understand variations in solar wind activity.

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"What we're looking at here is a massive driver of solar storms," explained study author Scott McIntosh, director of the High Altitude Observatory of the National Center for Atmospheric Research in Boulder, Colorado.

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 11-year solar cycle that is part of a longer cycle lasting about 22 years.

Observations showed the overlapping bands are driven by the rotation of the Sun's deep interior. As the bands move within the Sun's northern and southern hemispheres, activity rises to a peak over a period of about 11 months and then begins to wane.

McIntosh said the quasi-annual variations can be likened to regions on Earth with two seasons, such as a rainy season and a dry season

Using data from NASA satellites plus ground-based observatories, researchers kept track of solar wind flow and violent activity such as solar flares on the solar surface. They determined that these bands travel across the Sun in a 330-day activity cycle.

Researchers can turn to advanced computer simulations and more detailed observations to learn more about the huge influence of the bands on solar activity. McIntosh said this could be assisted by a proposed network of satellites observing the Sun, much as the global networks of satellites around Earth have helped advance terrestrial weather models since the 1960s.

The study appeared in the journal Nature Communications.

TagsSun Has Four Seasons Too Study Says, Sun, four seasons, space exploration, quasi-annual variations, NASA, solar wind flow, solar flares