• An August 2017 launch of a Falcon 9 rocket created a 900 km wide "hole" in the ionosphere
  • As the rocket left Earth, it let loose a shockwave that pushed away plasma particles that are found in the atmosphere
  • This event lasted only a few hours, but was the largest ever such instance of a rocket causing such a disturbance in the atmosphere
  • The trajectory taken by the Falcon 9 is to blame as it did not arch diagonally, but went straight up, causing a lot of energy to be built up in its wake

A SpaceX launch last August using a Falcon 9 rocket took an unusual trajectory into space which caused a build-up of energy that created a massive shock wave as it left the Earth.

"Hole in the ionosphere" does not mean there was a temporary vacuum or that the SpaceX Falcon 9 ripped a piece of the atmosphere and carried it out into space. It only means that as the rocket sped by, it pushed out particles away from it, causing a dip in plasma levels which later corrected itself.

It lasted about two hours and opened up a crater almost 900 km wide, according to a study published by the American Geophysical Union.

As to why it happened with a Falcon 9 launch and not when the world's most powerful rocket- the Falcon Heavy took off is because of the way the rocket left the atmosphere. A report by Mashable points out that when rockets launch, they do not fly straight up, they take a wide arching trajectory. This prevents the build-up of huge shockwaves. Even if there is a shockwave, it will be a lot smaller and less damaging, notes the report.

The August launch was carrying a Taiwanese Earth observation satellite into orbit about 724 km above the Earth and it was relatively light load, notes the report. SpaceX decided to go straight up and not make a sweeping arch from launch to delivery altitude, this created a build-up of energy around the rocket and when it reached the upper atmosphere, caused an "ionospheric hole".

The ionosphere is a layer of the atmosphere that starts from about 60 km in the air to the outer reaches of the magnetosphere. This region in the sky is weakly ionized by the Sun's UV and cosmic radiation, allowing it to conduct electricity.

According to Charles Lin, a geophysicist at the National Cheng Kung University in Taiwan, who led this study, said this has been the largest such ionospheric disturbance ever recorded from a rocket launch. A similarly shaped hole was recorded from a 2009 volcanic eruption in Russia, he said.

Disruptions in the ionosphere can have real-world consequences, notes the report, especially with regards to GPS satellites that aid navigation. A hole in the ionosphere can cause GPS signals to be off by up to a meter. While this might not be much for the average user, it could have damaging effects on the military and pilots who might be using GPS over the area.

SpaceX is readying its BFR- a rocket that is a lot more powerful than even their current largest launch vehicle to carry people to Mars. 

Falcon 9
A Falcon9 launch by SpaceX- Representational imageSpaceX via Flickr