Using a computer model, researchers have gained new insights into how solar activity affects the orbits of low Earth orbit satellites1. They found that energetic photons and radiation from solar activity heat the upper atmosphere, increasing its density and creating atmospheric drag.

This drag slows low Earth orbit satellites, causing them to lose altitude. These insights could be useful for developing strategies to counter the effects of solar activity on the orbits of such satellites.

The Sun flares up every 11 years, intensifying phenomena such as solar wind streams and coronal mass ejections. To probe how heightened solar activity affects the orbits of low-orbit satellites, the researchers modeled two hypothetical satellites launched into low orbits at an altitude of 450 kilometres. They then computed how solar activity during the periods 2000–2002, 2004–2006 and 2012–2014 would impact their orbits.

The scientists found that solar flares and storms heated and expanded the atmosphere and that these effects could extend to the satellites’ orbits. The density of atmospheric gases increases, slowing the satellites and causing them to lose altitude by a few kilometres per day. “This means that satellites launched during periods of heightened solar activities will stay in orbit for a shorter time,” says Sandip Chakrabarti, one of the researchers.

The authors of this work are from: S. N. Bose National Centre for Basic Sciences, and Indian Centre for Space Physics, Kolkata, India and George Mason University, Fairfax, USA.