The mystery of the solar minimum deepens as astronomers find it has remained ‘surprisingly constant’ for more than 60 years

As the sun moves through its 11-year cycle, it experiences active and quiet periods known as the solar maximum and solar minimum.

While solar maximum can present itself in a host of different ways, a new study has found that microwaves emitted during the solar minimum have largely remained the same for more than half a century, according to Daily Mail.

The discovery is surprising, the researchers say, and could help to provide a clearer understanding of the processes that give rise to sunspots and other solar activity.

Astronomers have been continuously monitoring solar microwaves across four-frequencies since 1957.

 In a new study, researchers analyzed the solar microwave data collected during the telescopes’ six decade observation, revealing that the microwave intensities and spectra for solar minimum were the same every time in the last five cycles.

The solar maximums, however, varied in both intensity and spectrum from cycle to cycle.

‘Other than sunspot observations, uniform long-term observations are rare in solar astronomy,’ says lead researcher Masumi Shimojo.

‘It is very meaningful to discover a trend extending beyond a single solar cycle. This is an important step in understanding the creation and amplification of solar magnetic fields, which generate sunspots and other solar activity.’

NASA recently revealed that the sun is heading toward solar minimum. 

In this time, certain types of activity, such as sunspots and solar flares will drop – but, it’s also expected to bring the development of long-lived phenomena including coronal holes.

Solar minimum could also enhance the effects of space weather, potentially disrupting communications and navigation systems, and even causing space junk to ‘hang around.

The sun follows roughly an 11-year cycle. While sunspots were relatively high back in 2014, they’re now heading toward a low point expected in 2019-2020.

‘This is called solar minimum,’ said Dean Pesnell. ‘And it’s a regular part of the sunspot cycle.’

The change, however, doesn’t mean that activity ceases altogether, the expert explains.

Instead, different types of events tend to take hold.

For instance, ‘during solar minimum we can see the development of long-lived coronal holes,’ Pesnell says.

‘We see these holes throughout the solar cycle, but during solar minimum, they can last for a long time – six months or more.’

These are areas in the sun’s atmosphere where the magnetic field opens up, sending streams of solar particles into space.

When the resulting solar wind hits Earth’s magnetic field, it can cause space weather events including geomagnetic storms, auroras, and disruptions to communications and even satellites.

It can even effect the space debris floating around Earth.

The drag experienced as objects circle Earth helps to keep low-Earth orbit clean, the space agency explains.

This is the result of heating by ultraviolet radiation from the sun.

When solar minimum occurs, the upper atmosphere cools down, reducing the drag.

 ‘During solar minimum, the sun’s magnetic field weakens and provides less shielding from these cosmic rays,’ Pesnell says.

‘This can pose an increased threat to astronauts travelling through space.’

N.H.Kh