A recent solar storm that grazed the Earth on October 20 has baffled astronomers and space weather experts with its unexpected intensity and spectacular aurora display. NASA has shared a composite image that shows the widespread impact of the solar storm across the US and other regions.
What is a solar storm and how does it affect Earth?
A solar storm is a disturbance in the Sun’s atmosphere that can release a large amount of energy and matter into space. Sometimes, these eruptions can be directed towards the Earth and interact with its magnetic field and atmosphere, causing geomagnetic storms and auroras.
Geomagnetic storms are disturbances in the Earth’s magnetic field that can affect power grids, satellites, navigation systems, and radio communications. Auroras are colorful displays of light in the sky that are caused by charged particles from the Sun colliding with air molecules in the upper atmosphere.
How did the October 20 solar storm surprise scientists?
The solar storm that occurred on October 20 was triggered by a pair of coronal mass ejections (CMEs) that left the Sun one after the other in small eruptions. CMEs are large clouds of plasma and magnetic fields that are ejected from the Sun’s surface. They can travel at speeds ranging from 250 to 2,500 kilometers per second.
The CMEs that caused the October 20 solar storm did not make a direct hit on the Earth, but rather sideswiped it, creating a glancing blow. Forecasters had predicted that the storm would be minor, with a G1-class intensity on a scale of G1 to G5, where G5 is the most severe.
However, the impact of the storm was more massive than anyone could have imagined. The storm produced a stunning aurora display that surpassed the intensity seen in G1-class storms. The auroras were visible across the US, Canada, Europe, and even parts of Asia and Australia.
What was the reason behind the enhanced aurora display?
One of the possible reasons behind the enhanced aurora display was the orientation of the magnetic fields carried by the CMEs. The direction of these fields can either enhance or cancel out the effect of the solar storm on the Earth’s magnetic field.
According to some space weather experts, the CMEs that struck the Earth had an east-south-west (ESW) orientation, which is one of only two orientations that can pack a big punch. This orientation allowed the CMEs to connect with the Earth’s magnetic field and open up cracks for more solar particles to enter.
Another possible reason was the timing and spacing of the CMEs. The first CME arrived at around 8:00 UTC on October 20, followed by the second one at around 15:00 UTC. The gap between them may have created a favorable condition for more energy transfer and aurora production.
How did NASA capture the image of the aurora display?
NASA captured the image of the aurora display using its Worldview application, which provides access to satellite imagery from various sources. The image was created by adding six different layers in Worldview and creating a composite that showcases the auroras across the high and mid-latitudes.
The image was shared by NOAA’s Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin-Madison on X. The institute said that they could not download polar-orbiting data via direct broadcast on Saturday due to a power outage, so they used Worldview to create a composite view of the aurora from space.
The image shows a bright green trail of aurora moving across the US, bisecting the nation in two halves. The aurora spread intensifies in the middle and thins out at the coastal regions. Some observers also reported seeing red and orange colors in the aurora, which are rare and indicate higher energy levels.
