In this blog we explain all the data you need to predict aurora.
If you want to travel to the far north to observe and photograph the aurora borealis, you need to learn how to predict it. In this blog you will learn all about solar storms, when they arrive on Earth, whether there are aurora borealis and, of course, whether the weather will cooperate.Â
Nuclear fusion takes place on the sun. The simplest atom in the universe, hydrogen, is fused into helium. Enormous energies are released in the process. Due to the high temperatures on the sun, hydrogen is found there almost only as an ion: A positively charged proton, it has given up its electron. The thermal processes and particle flows on the sun create extremely strong magnetic fields. These fields accelerate the ions and electrons towards the earth, creating a constant stream of particles, the solar wind. The sun loses 1,000,000t of mass per second.
Sometimes, extremely strong solar flares occur on the sun. During these eruptions, particularly fast particles are hurled into space in concentrated form. If such a solar flare is earth-directed, it can be used to predict auroral activity. If the charged particles hit the Earth’s magnetic field, aurora borealis can occur. Solar flares originate from sunspots. Sunspots are colder areas in the outer shell of the sun, they can be easily observed.
If there has been a solar flare and you can see a noticeable increase in the X-ray flux, then in order to predict the aurora you must of course also see whether the particle ejection can reach the Earth. Since the Sun is a sphere and the Earth revolves around it, the particle stream may simply pass us by.
This is where the sunspots help. The SOHO/SDO satellites observe the sun. They are located geostationary in front of and behind the Earth and therefore observe the Sun from our perspective. If you can see on the satellite image that a group of sunspots can be seen quite centrally on the solar disk, then the solar storm can hit the Earth.
When an eruption occurs on the sun, electrical charges are accelerated extremely strongly. This produces X-ray radiation. This X-ray radiation travels to Earth at the speed of light and therefore reaches us within 8 minutes. The charged particles of the solar storm, on the other hand, take 48h-72h to reach the Earth.
Therefore, the first indicator to predict aurora is the X-ray flux, the amount of X-rays emitted by the Sun. As in the following, all graphs and data are taken from www.polarlicht-vorhersage.de. The site is in German, but the graphics can be understood non-verbally. It is the most compact website to view all the necessary data.
The X-ray flux is always in the range of an intensity of “B”. If there is a solar flare, the graph jumps upwards. Strong eruptions reach “M” or “X” on the logarithmic scale. If you detect an eruption with this intensity, then there could be auroras and you can focus on the other values to predict auroras.
The two LASCO satellites are also in a geostationary position. With the help of these, you can determine whether the solar storm could reach the Earth. Shortly after you notice a rise on the X-ray flux, you can see on the LASCO film whether the ejection looks symmetrical or, for example, only goes in one direction.
If the solar storm is heading towards Earth, the eruption must look symmetrical from our perspective. To predict the aurora you have to estimate this. If, on the other hand, the LASCO film shows that the eruption only goes in one direction, the solar storm will probably miss the Earth.
According to this, NASA operates several satellites to predict the aurora borealis. Rather, the aurora is only a visual by-product of a solar storm. During a strong solar storm, communication with satellites is disrupted and failures can occur. Therefore, there is a legitimate interest in predicting the solar wind.
The aurora borealis is just a nice side effect. From all the solar observation data, NASA calculates a solar wind forecast. This is updated every 24 hours. So you have to be patient until NASA can include an eruption in the forecast. The forecast is easy to understand. The Earth is the yellow dot. The animation shows the particle density that can be expected over time. W
hen you see a correspondingly high density there, you can read off the date and know the approximate time period. You can also see that there is actually always a solar wind, which emerges from the Sun in several spiral arms. Whenever the Earth is hit by the solar wind, there is an increased probability of aurora borealis. However, this can only be observed in the far north.
Despite all the satellites NASA operates, predicting the solar wind and solar flares is extremely complicated. The sun is 150 million kilometres away from the earth and there is a complex interplanetary magnetic field. The charged particles are subject to this field. So a lot can happen on the way to Earth that we simply can’t measure. If you want to observe the aurora, you have to be patient and wait for the particle wind.
The connection is quite simple: the particles of the solar wind collide with the particles in the Earth’s atmosphere and thus stimulate them to glow. The more particles from the sun hit the Earth, the more light is produced in the Earth’s atmosphere and the more intense the aurora. The particle density is recorded by the DSCVOR satellite. As long as the DSCVOR satellite does not indicate a high particle density, an intense aurora is unlikely. A high particle density is highlighted in colour.
The faster a particle is, the greater its kinetic energy. The kinetic energy is released in quants (=portions) during the collisions with the particles of the Earth’s atmosphere. The greater the kinetic energy, the more particles can be excited and the deeper the solar wind can penetrate the atmosphere, producing different colours. The particle velocity is also highlighted in colour.
The two previous values indicate whether there is still potential for aurora during the night. As already mentioned, the interaction of the earth’s magnetic field together with the sun’s magnetic field is extremely complicated. It can happen that there are many particles in the earth’s magnetic field, but these are never directed towards the poles – the aurora remains absent. Only when the Bz value of the Earth’s magnetic field becomes negative can aurora be expected. This is also marked in colour.
The last instance is the magnetometer. These are only useful if you do not have a clear view of the night sky and you are waiting for a gap in the clouds. Because if you have a clear view of the sky, then you can see the aurora. The magnetometers cannot predict the aurora, they can only measure the current effect of the solar wind on the Earth’s magnetic field. This correlates with the intensity of the aurora.
When electricity flows, it creates a magnetic field. Correspondingly, a large number of charged particles in the Earth’s atmosphere moving at high speed generate their own magnetic field. This counteracts the Earth’s magnetic field. The earth’s magnetic field is actually constant. If a large number of charged particles hit the magnetic field, the measured value of the magnetic field strength at the magnetometers changes within a short time and strong fluctuations occur. These can be seen on the diagram of the magnetometers.
The diagram also shows how far south the aurora can be observed. The further south it extends, the further south magnetometers are affected. You can use it to predict aurora and even determine its extent! Magnetometers are the most important tool for observing the aurora.
All the readings and data you can use to predict aurora won’t help you if it’s cloudy at night. That’s why VIEWFINDR offers a special weather forecast that shows you if you can expect gaps in the clouds and a clear night sky. If you see auroral activity on the magnetometers but don’t have a clear view of the sky, you can use our weather forecast to see if a gap in the clouds will clear the sky. To do this, simply use the “Starry sky” parameter in VIEWFINDR.
