Solar tsunami can trigger the sunspot cycle

Sunspots [image credit: NASA]

Something else for solar theorists to ponder. The researchers say: ‘We have demonstrated here a physical mechanism, the solar tsunami, which gives birth to the new cycle’s sunspots precisely within a few weeks from the cessation of old cycle’s spots.’

According to the model, the next sunspot cycle can be expected to begin in 2020, says The Hindu.

It is believed that the “solar dynamo” — a naturally occurring generator which produces electric and magnetic fields in the sun — is linked to the production of sunspots.

What kick-starts the 11-year sunspot cycle is not known. Now, a group of solar physicists suggests that a “solar tsunami” is at work that triggers the new sunspot cycle, after the old one ends.

The extreme temperature and pressure conditions that prevail some 20,000 km below the sun’s surface cause its material to form a plasma consisting primarily of hydrogen and helium in a highly ionised state. The plasma is confined with huge magnetic fields inside the sun.

Explains Dr. Dipankar Banerjee from the Indian Institute of Astrophysics, Bengaluru, and one of the authors of the paper published in Scientific Reports, “The [sun’s] toroidal magnetic field, from which sunspots get generated, wraps around the sun in the east-west direction.”

Celestial rubber bands

These magnetic fields behave like rubber bands on a polished sphere. They tend to slip towards the poles. Holding these fields in their place requires that there is extra mass (plasma mass) pushing at the bands from higher latitudes.

Thus, a magnetic dam is formed which is storing a big mass of plasma. At the end of a solar cycle, this magnetic dam can break, releasing huge amounts of plasma cascading like a tsunami towards the poles.

These tsunami waves travel at high speeds of about 1,000 km per hour carrying excess plasma to the mid-latitudes. There they give rise to magnetic flux eruptions. These are seen as the bright patches that signal the start of the next cycle of sunspots.

The tsunami waves can traverse the required distance in a few weeks, unlike in earlier models.

Full article here.