Published: Saturday, June 8, 2024
Credit: Pixabay/CC0 public domain
Recently, more people than usual were able to observe the northern and south lights with their naked eyes. The unusual event was caused by a strong solar storm that affected the Earth’s magnetic fields.
This is the peak of an 11-year cycle. We can expect to see more intense particle explosions. These are the conditions that ultimately lead to the beautiful auroras, and the geomagnetic events which can cause damage to infrastructure, such as power grids, satellites, and orbiting satellites.
What is causing these phenomena? Northern and Southern Lights usually occur at very high or very low latitudes. The solar magnetic field guides high-energy particles to the Earth. In a process called reconnection, they are transferred to the Earth’s magnetism.
The hot, fast particles sprint down the Earth’s magnetic fields, in the direction of force, until they reach a neutral atmospheric particle, such as oxygen, hydrogen, or nitrogen. This is when some of the energy is lost, and this heats up local environments.
The particles in the atmosphere don’t enjoy being energetic so they release a small amount of energy into the visible range. You will notice that depending on the element, different wavelengths and colors are emitted within the visible range of the electromagnetic spectrum. It is this source that produces the auroras we see in high latitudes, and during solar events at lower latitudes as well.
Blues, purples, and greens in auroras come from nitrogen. Greens and reds come from oxygen. The Earth’s magnetic fields are similar to bar magnets, so the area that receives the particles is located at high and low latitudes. (Arctic Circle or Antarctica, in general).
What happened that allowed us to see auroras much farther south in the Northern Hemisphere?
At school, you may have sprinkled iron filings onto a piece of paper and placed it on top a magnet. You could then see how the filings aligned with the magnetic field. Repeat the experiment several times to see the same shape.
The Earth’s magnet field is constant, but it can also be compressed or released depending on the strength of the sun. Imagine two balloons that are half-inflated pressed together.
When you add more gas to a balloon and inflate it, the pressure increases, pushing the smaller balloon out. The smaller balloon will relax and push back as you release the extra gas.
The closer the magnetic field lines to the equator are, the more auroras we can see.
Storms of exceptional severity
A moving magnetic field is also a source of potential problems: it can create a current on anything that conducts electrical power.
The largest currents in modern infrastructure are generated by power lines, underground pipelines, and train tracks. This movement can be tracked by measuring the difference between “normal” and how disturbed the magnetic fields is. Researchers use the disturbed storm index as a measure.
According to this measurement, the geomagnetic thunderstorms of 10 and 11 May were extremely strong. A strong storm can induce electrical currents. The power lines are the most vulnerable, but they have been protected by protections that were built into the power stations. Since the 1989 geomagnetic event that melted a transformer in Quebec, Canada and caused hours of power loss, these issues have been in the spotlight.
Metallic pipelines are more at risk, as they corrode when a current is run through them. It is not an immediate effect but a gradual build-up of eroding materials. It can have a strong impact on infrastructure, but it is difficult to detect.
Currents are a major problem on Earth, but they can be even more problematic in space. Satellites are limited in their grounding and a surge of electricity can damage instruments and communications. A zombie satellite is what is called when a satellite loses communications. It is usually lost completely, causing a high investment loss.
Changes in Earth’s magnetic fields can also impact the light that passes through. This change is not visible, but it can affect the accuracy of GPS-style location systems, since a reading’s location depends on how long it takes between your device to reach a satellite. This is because the increase in electron density, or the number of particles that are in the path of the signal, causes the wave to bend and take longer to reach your device.
These changes can also impact the bandwidth speed for satellite internet, and the radiation belts of the planet. This is a torus made up of charged particles with high energy, mainly electrons. It’s located 13,000km from the surface. Geomagnetic storms can propel these particles to the lower atmosphere. The particles can affect the ozone levels and interfere with aircraft’s high-frequency (HF) radio.
Auroras don’t just occur on Earth. They can be found on many other planets, and they tell us much about the magnetic field that exists in those celestial bodies. The “planeterella” is an instrument that was first created by Norwegian scientist Kristian Brkeland in the early 1900s.
In a vacuum chamber, a magnetic sphere (representing Earth), is placed and the solar winds are simulated by firing atoms at the sphere. In the UK, we have two of these instruments within universities. Here at Nottingham Trent University, I helped a student to build a budget-friendly version for a Masters Project.
You can see how auroras are affected by changing the strength of the magnetic field and the distance between the objects. As you might expect from an atmosphere with 72% nitrogen, the emission is predominantly purple. Around the top of the aurora, a strong emission ring is visible. This ring changes latitudes depending on the strength of the magnetic field.
Auroras are an amazing natural phenomenon. Even better, with each strong geomagnetic event we improve our ability to protect ourselves from the damage that could be caused by future events.
This article was republished by The Conversation, under a Creative Commons License. The original article can be read.