© NASA SDO
Violent: The fourth of the Sun’s massive X-class flares in a fortnight, which peaked on October 29 is pictured. The image by NASA’s Solar Dynamics Observatory shows light in wavelengths of both 304 and 193 Angstroms
More than two dozen solar flares have erupted from the Sun in the past seven days, catapulting radiation towards the Earth that could potentially play havoc with global communications.
The U.S. National Oceanic and Atmospheric Administration issued four radio blackout warnings in the past two days after solar weather suddenly turned turbulent.
Radiation from flares cannot penetrate Earth’s atmosphere to harm life on the ground, but when intense enough it can disturb the atmosphere in the ionosphere, where GPS and radio signals travel.
Since October 23 the Sun has let loose with 24 medium-strength M-class solar flares, and four X-class flares – the most powerful kind.
In fact, with our local star heading towards the peak of its 11-year cycle, a period known as the solar maximum, this shouldn’t be unusual. But lead up to the solar max has been unusually subdued this year.
Humans have tracked the solar cycle continuously since it was discovered in 1843, and it is normal for there to be many flares a day during the sun’s peak activity.
Holly Gilbert, a solar physicist at NASA Goddard Space Flight Center, told the Los Angeles Times: ‘It hadn’t been active in months, so it’s like it finally woke up.
‘For those of us who study the dynamics of the sun, it is exciting because it gives us more events to study.’
Solar flares happen when energy stored in magnetic fields twisted across the surface of the Sun is suddenly released.
‘You get a tangled bunch of magnetic fields, and they get too tangled and too stressed, they end up erupting,’ added Dr Gilbert.
The recent solar flare activity has also been accompanied by several coronal mass ejections (CMEs), say Nasa officials.
There are another kind of solar phenomenon that send billions of tons of particles into space that can reach Earth one to three days later.
Like the radiation from solar flares, these particles cannot travel through the atmosphere to harm humans on Earth; but they can affect electronic systems in satellites and on the ground.
© NASA SDO
Turbulent: Another X-class flare exploding off the right side of the sun, peaking on October 27. This image is in the 131 Angstrom wavelength, which is particularly good for showing solar flares and is often coloured in teal
CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they funnel energy into Earth’s magnetic envelope, the magnetosphere, for an extended period of time.
The CME’s magnetic fields peel back the outermost layers of Earth’s fields changing their very shape, distortions which can can degrade communication signals and cause unexpected surges in power grids.
They also can cause aurora. Storms are rare during solar minimum, but as the sun nears solar maximum, large storms occur several times per year.