Surging Temperatures in Earth’s Thermosphere Raise Concerns for Satellites

Earth’s thermosphere, the second-highest layer of the atmosphere, recently experienced a near 20-year temperature peak due to the energy absorbed from geomagnetic storms that occurred this year. This temperature increase is expected to continue in the coming years as solar activity intensifies, which could have implications for Earth-orbiting satellites, according to experts.

The thermosphere extends from around 53 miles (85 kilometers) above the ground to approximately 372 miles (600 km) above the ground, with outer space beginning beyond the exosphere, as explained by NASA. For over two decades, NASA has been measuring the temperature of the thermosphere using infrared radiation emitted by carbon dioxide and nitric oxide molecules. Data collected by NASA’s Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite is converted into the Thermosphere Climate Index (TCI), measured in terawatts (TW).

The TCI value reached its peak on March 10, measuring 0.24 TW, the highest since December 28, 2003, according to Martin Mlynczak, a leading researcher on the TIMED mission at NASA’s Langley Research Center. This temperature spike was caused by three geomagnetic storms in January and February, which are major disturbances to Earth’s magnetic field triggered by coronal mass ejections (CMEs) and solar wind emitted by the sun. These storms deposit energy in the thermosphere, resulting in increased heating and infrared emission from nitric oxide and carbon dioxide. Normally, infrared emissions cool the thermosphere after a storm, but consecutive storms can maintain high temperatures.

Since the spike in March, at least two more geomagnetic storms have occurred, including the most powerful solar storm in over six years on March 24. The TCI values following these storms have remained high but have not surpassed the March peak.

Geomagnetic storms become more frequent and intense during solar maximum, a phase in the roughly 11-year solar cycle when the sun is most active and covered in dark sunspots and plasma loops that release CMEs and solar wind. Consequently, Earth’s thermosphere also follows an approximately 11-year cycle. Government scientists from NASA and NOAA predict that the next solar maximum will occur in 2025, indicating that the warming trend in the thermosphere will likely continue in the coming years.

The changes in the thermosphere pose challenges for satellites in low-Earth orbit positioned around its upper boundary. As the thermosphere expands due to warming, increased aerodynamic drag affects all satellites and space debris. This increased drag can pull satellites closer to Earth, potentially causing collisions or complete orbital failure, as observed with SpaceX Starlink satellites after a surprise geomagnetic storm in February 2022.

Satellite operators can mitigate these issues by adjusting the spacecraft’s orbit when necessary. However, the unpredictability of space weather makes it challenging to determine the timing of these maneuvers until it may be too late.

There is also a possibility that solar maximum could arrive sooner than predicted. A recent study published in the journal Frontiers in Astronomy and Space Sciences suggests that the solar activity peak could occur as early as late 2023 and be more powerful than initially anticipated. If this scenario unfolds, the risk of satellite disasters would further increase.

However, over longer timescales, temperatures in the thermosphere are declining due to excess CO2 caused by climate change, which increases infrared emissions into space, according to a study published in the journal Earth Atmospheric and Planetary Sciences on May 8.

The impact of these temperature changes in the thermosphere on Earth’s satellites and space activities remains an ongoing concern.

How do temperature spikes in the thermosphere caused by solar activity impact Earth-orbiting satellites and their functionality?

Which is a period of high solar activity that occurs every 11 years. Currently, we are approaching the next solar maximum, expected to peak in 2025. As solar activity intensifies, scientists predict that geomagnetic storms will become more common and potentially more powerful. This means that the thermosphere will continue to experience temperature increases in the coming years.

The implications of these temperature spikes in the thermosphere are significant, particularly for Earth-orbiting satellites. The higher temperatures can cause increased drag on satellites, which can affect their orbits and lifespans. They can also lead to changes in the Earth’s ionosphere, affecting radio communication and navigation systems.

Monitoring the thermosphere’s temperature is crucial for understanding and predicting the behavior of our atmosphere. NASA’s TIMED satellite has been instrumental in collecting data on the thermosphere’s temperature for over two decades. The Thermosphere Climate Index (TCI) derived from this data provides valuable insights into the overall health and dynamics of the thermosphere.

As we continue to study and observe the thermosphere, it is important to recognize the potential impacts of solar activity on Earth’s atmosphere and technological infrastructure. This knowledge can help us prepare and mitigate any adverse effects on satellite operations and other systems reliant on the thermosphere’s stability.