The Sun Has Seasons Too, Say Experts

Seasons on Earth are determined by how and when our big blue world is tilted towards the Sun. The Sun then, as it is at the center of this process, could not possibly have seasons of its own. Now new research has revealed that this is not necessarily true, for the star actually undergoes predictable swings between times of relative calm and times of intense solar activity.

That's at least according to a study recently published in the journal Nature Communications, which details how these apparently 'seasonal' changes could help researchers better understand and even predict variations in solar wind activity.

"What we're looking at here is a massive driver of solar storms," study author Scott McIntosh, director of the High Altitude Observatory of the National Center for Atmospheric Research in Boulder, Colorado, explained in a statement. "By better understanding how these activity bands form in the sun and cause these seasonal instabilities, we can greatly improve forecasts of space weather."

What McIntosh is talking about are bands of strong magnetic fields that make their way across each of the Sun's hemispheres on a regular basis. He and his colleagues specifically were investigating what creates these bands and how they influence solar cycles.

Using data from a host of NASA satellites and ground-based observatories, the researchers were able to keep track of solar wind flow and violent activity on the solar surface (CMEs, flares, etc.) They quickly determined that these bands predictably march across the Sun in a 330-day activity cycle - one that has been noticed before, but was often overlooked as astronomers sought to investigate the Sun's seemingly more important 11-year solar cycles.

"People have not paid much attention to this nearly-annual cycle, but it's such a driver of space weather that we really do need to focus on it," said McIntosh. (Scroll to read on...)

He punctualizes this point by bringing attention to the Gnevyshev Gap - the lag between peak sunspot sightings in a year and a predictable wave of solar flares that follows. The phenomenon was first noticed in the 1960s by Soviet scientists, but the cause was never certain.

McIntosh and his colleagues now say that the gap is dependent on these seasonal bands.

"The activity bands on the sun have very slow-moving waves that can expand and warp," explained co-author Robert Leamon, of Montana State University. "Sometimes this results in magnetic field leaking from one band to the other. In other cases, the warp drags magnetic field from deep in the solar interior and pushes it toward the surface."

This pushing and pulling on the Sun's surface could be what initially causes dark spots on the Sun, and as things destabilize, a time of violent solar activity ensues. And as the bands themselves see "quasi annual" variation in their strength, giving rise to the semblance of "stormy seasons" on the Sun.

Now, "if we can combine these pieces of observational information with modeling efforts," McIntosh added, "[our] space weather forecast skill can go through the roof."

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