Scientists have detected Earth’s ambipolar electric field for the first time

For the first time, scientists have successfully detected and measured an invisible electric field enveloping Earth. This field, known as the ambipolar field, was first theorised over 60 years ago and its discovery marks a significant advancement in our understanding of Earth’s atmospheric dynamics. Glyn Collinson, an astronomer at NASA’s Goddard Space Flight Center, and his team have achieved this breakthrough, opening new avenues for studying how such fields influence planetary atmospheres and potentially shape other celestial bodies.

Understanding the Ambipolar Field

The ambipolar field was hypothesised to exist around 250 kilometres (155 miles) above Earth’s surface, within the ionosphere—a region of the atmosphere ionised by solar and ultraviolet radiation. This field emerges because of the interaction between negatively charged electrons and positively charged ions. When ultraviolet rays ionise atmospheric atoms, they create a mix of free electrons and ions. The ambipolar field acts to balance these particles, with electrons attempting to escape into space and ions pulling back towards Earth, creating a stabilising force.

How the Field Was Detected

The field was detected by the Endurance rocket, which was launched in May 2022. The rocket ascended to an altitude of 768.03 kilometres (477.23 miles) before returning to Earth with valuable data. The mission aimed to measure the faint electric potential changes associated with the ambipolar field. Despite the field’s weak strength, only a 0.55-volt change was detected, comparable to the charge of a watch battery. This minute measurement was sufficient to confirm the presence of the ambipolar field and its effects on the polar wind.

Significance of the Discovery

The ambipolar field plays a crucial role in regulating the atmosphere’s density and composition. It helps to control the altitude at which ions escape into space, impacting the overall atmospheric structure. The detection of this field provides insight into how Earth’s atmosphere maintains charge neutrality and how particles are transported away from the planet. It also affects the polar wind—an outflow of particles from the Earth’s atmosphere observed at the poles.

Implications for Future Research

While the immediate findings are promising, this discovery is just the beginning. The ambipolar field’s broader implications are still being explored. Researchers are keen to understand how long this field has been present, how it influences atmospheric evolution, and its potential impact on life on Earth. Glyn Collinson highlights that measuring this field allows scientists to pose new questions about Earth’s atmospheric processes and planetary science more broadly.

With this breakthrough, scientists can now delve deeper into the fundamental mechanisms that govern Earth’s atmosphere and potentially apply these insights to other planets with atmospheres. The ambipolar field’s discovery represents a significant step in planetary science, paving the way for future exploration and understanding of the forces shaping our world.