Project Summary

Our team set out to study one of the least understood regions of Earth’s atmosphere—the mesosphere and lower thermosphere (MLT)—which lies between the air we breathe and outer space. This region is especially important at low latitudes, where complex interactions with the atmosphere influence the space conditions.

To tackle this challenge, we brought together experts in atmospheric dynamics, chemistry, and space physics. We held one virtual kickoff meeting and two in-person workshops, in Switzerland and China, to exchange ideas and build collaborations.

Our main goal was to better understand why the MLT can change so much from one day to the next, and how these changes affect the thermosphere–ionosphere system, which plays a critical role in satellite communication, navigation, and space weather. We asked three big questions:

• How can we measure and describe day-to-day changes in the MLT at low latitudes?
• How do weather systems lower in the atmosphere (from the troposphere and stratosphere) influence these changes?
• How do processes in the MLT, in turn, affect the upper atmosphere and ionosphere, including the development of plasma irregularities that can disrupt communication and navigation signals?

Through this work, our team explored several important events and processes, including:

• An unusual westward wind event around the March equinox.
• How the MLT responds during both strong and weak polar vortex conditions.
• The formation of sporadic E layers, thin layers of ionization linked to atmospheric disturbances.
• The impact of the solar storms (including the 2024 storms) on the MLT and ionosphere.

Our collaborations have already resulted in 18 scientific papers (14 published so far). Highlights include:

• Explaining the origin of the rare March 2023 westward wind event by combining theory, observations, and new modeling tools.
• Using a new Japanese high-altitude reanalysis (JAWARA) to improve how we study MLT dynamics.
• Demonstrating the power of the new Chinese Sanya Incoherent Scatter Radar (SYISR) to study small-scale irregularities in the ionosphere and their connection to atmospheric processes.

By joining forces across disciplines and countries, we are uncovering how Earth’s atmosphere and near-space environment are connected. These insights not only advance science but also help us better anticipate and respond to the effects of space weather on the technologies we depend on every day.

 

(Credits: Header figures are courtesy of  NASA)