Solar Flares: What are they and are they dangerous?

The Sun is a constant presence in everyday life from rising in the morning signifying the beginning of the day, to setting at night representing the time to rest. With the human race ever more dependent on technology it is important to monitor solar activity and the potential harm it can pose to satellites and power grids. In fact space weather, caused by solar activity (ie. solar flares), is one of the top eight possible threats to the United Kingdom among others such as severe weather conditions and cyber attacks.

This is an image of the Sun taken in a certain
wavelength of light by the Solar Dynamics
Observatory showing a flare as the bright
region in the top left hand corner. Image
Credit: NASA Goddard Spaceflight Centre.

But, what is a solar flare?

A solar flare is a sudden brightening in the Sun’s atmosphere confined to a small region. It can be seen across all wavelengths from X-rays to radio waves and is caused when the Sun’s magnetic field changes its topology. The magnetic field of the Sun is very complex and can become twisted and caught. When this happens the magnetic field grows to be stressed, producing a build up of energy and eventually ‘snapping’, changing its structure and relaxing. This build up of magnetic energy is then converted into thermal and kinetic energy producing the flare. Think of an elastic band; if you stretch and twist it over time it too will become stressed and snap. This is similar to the magnetic field of the Sun, however, it is not broken but simply reconnects to another part of the field, ready for the cycle to repeat again. Solar flares generally occur in areas of strong magnetic field which are commonly populated by sun spots. These areas are called active regions and can last from a few days to a few months. Sunspots are created when the magnetic field is stronger in a particular area than its surroundings. This is why the spots appear black as they are cooler than the area around them. However, cooler in this sense means around 3000°C as the Sun has a surface temperature of 6000°C! Solar flares result in an increase in radiation and are almost always accompanied by a mass motion of particles known as a Coronal Mass Ejection (CME). Many people make the mistake of thinking the flare is the CME, however, this is not the case.  They are different phenomena and the flare is only the increase in radiation, not the ejection of particles.

The magnetic field of the Sun is very complex
and this image shows the loops and twists as
lines extending out from the surface. Image
Credit: NASA/SDO/AIA.

Here we have a flare from August 2012 accompanied by a large
CME. The flare is the bright area in the left corner which is releasing
radiation across all wavelengths and the CME is the extended
structure underneath, which is a mass movement of fast and highly
energetic particles. Image Credit: NASA/SDO.

One of the largest and most famous flares in history was the Carrington flare. In 1859 Richard Carrington made the first observation of a solar flare while making

One of Richard Carrington’s original drawings of the white light flare he witnessed, this image details the location of the bright patches indicated by A,B,C and D. You can see this region is made up of a cluster of sunspots, known as an active region, and it is these areas where flares typically occur.

drawings of sun spots on the Suns surface. He noticed strong brightenings in the same area as a group of sunspots. We now call this a white light flare as it can be seen by the naked eye. Following Carrington’s observation there were problems with telegraphs, and the aurora borealis was observed much further south than usual, marking the first ever space weather event recorded in history. In fact, since then there have been many solar flare events which have had big consequences on Earth. For example, in 1989 a powerful solar flare set off a major blackout in Canada on March 13th, leaving almost six billion people without electricity for nine hours. The Bastille Day event on the 14th July 2014 was another famous solar flare causing radio blackouts and satellites to short circuit and lastly, in December of 2016 there was a powerful solar flare which caused disruptions to GPS satellites for roughly 10 minutes and damaged scientific instruments on-board NASA satellites. These are only a handful of the most powerful solar flares in history which have had direct effects on Earth, but don’t worry we have natural defences to protect us!

The above examples are some of the worst case scenario events which have happened on Earth as a result of a solar flare. Did you know, the Earth is extremely good at protecting us from all of the harmful particles and radiation which heads towards the planet in space? The Earth’s magnetic field, along with the atmosphere, shield us from the radiation and high energy particles which fly towards us after solar flare events. Without the Earth’s magnetic field our planet would constantly be bombarded by streams of fast moving, high energy, deadly particles. Radiation and cosmic rays (high energy particles which mostly originate from outside of the solar system) are a real concern as exposure to these can damage our DNA and increase the

This diagram represents what the Earth’s magnetic field looks like and how it stretches far out from the planet to protect us from harmful radiation and particles in space. In this scenario the solar wind, a stream of charged particles released from the Sun, is bombarding the Earth with fast moving highly charged particles which are being deflected away by the Earth’s magnetic field. The magnetic field has similar properties to a bar magnet aligned with the Earth’s axis. Image
Credit: NASA.

risks of cancer as well as other illnesses. In addition to this, the satellites which lie inside the magnetic field would also be at a higher risk causing many problems with technology on Earth. The atmosphere also plays an important role shielding us from harmful radiation. For example, Extreme Ultraviolet (or EUV) radiation from the Sun can be incredibly harmful to humans causing damage a lot worse than sun burn to our skin. It is fortunate for us that these rays are stopped in the upper layers of our atmosphere, never reaching the ground.

Despite all of this we are exceedingly lucky to have a star like the Sun at the centre of our solar system. It provides us with light and heat without which there would be no life on Earth and we wouldn’t exist. The Sun has great impacts on the Earth making it vital to understand the processes occurring in the star and how they affect our planet. Studying the Sun also provides us with the knowledge to understand other stars in the galaxy and their effects on exoplanets orbiting these stars. Solar flares are an extraordinary, beautiful and exciting phenomenon which provide a great insight into the wonders of the solar system and beyond. So remember, the next time your GPS doesn’t work or the power goes off in your house it could potentially be a solar flare causing it out in space!

By
Lauren Doyle
PhD Student, Armagh Observatory and Planetarium