For the first time, an international team of scientists, using data from a NASA suborbital rocket mission, has successfully measured a planet-wide electric field that plays a crucial role in Earth's atmosphere. This electric field, known as the ambipolar electric field, has long been theorised to drive the escape of particles from our atmosphere above the planet's poles. The recent findings not only confirm the existence of this field but also shed light on its significance in shaping Earth's ionosphere and influencing atmospheric escape. The discovery opens new avenues for understanding both our planet and others.

The Ambipolar Electric Field: A Long-Standing Mystery

The concept of the ambipolar electric field was first proposed over 60 years ago as a key factor in how particles from Earth's atmosphere escape into space. For decades, spacecraft flying over the poles detected streams of particles, termed the "polar wind," escaping our planet. However, these particles, often cold and travelling at supersonic speeds, baffled scientists. It was hypothesised that an undiscovered electric field could be propelling these particles into space, but measuring such a weak field over vast distances proved technologically challenging.

The Breakthrough with NASA's Endurance Mission

In 2016, Glyn Collinson and his team at NASA’s Goddard Space Flight Center set out to develop an instrument capable of detecting this elusive electric field. Their efforts culminated in the Endurance mission, a suborbital rocket flight designed to measure the ambipolar field from the Arctic. Named after the ship that carried explorer Ernest Shackleton, Endurance launched on 11 May 2022 from Svalbard, Norway, the only location suitable for such a mission.

Endurance soared to an altitude of 477 miles, collecting data across a 322-mile range. The results were groundbreaking: a change in electric potential of just 0.55 volts was detected, which, though seemingly minuscule, was precisely the force needed to drive the polar wind. The hydrogen ions, the most abundant particles in this outflow, were shown to be propelled by the ambipolar field with a force 10.6 times stronger than gravity, launching them into space.
The discovery of the ambipolar field has profound implications for our understanding of Earth's atmosphere. It not only helps explain the dynamics of atmospheric escape but also reveals the field's role in maintaining the density of the ionosphere at greater heights than previously thought. The field acts like a conveyor belt, lifting particles into space, and may have continuously shaped Earth's atmospheric evolution.

A New Frontier for Planetary Exploration

The significance of this finding extends beyond our planet. Scientists now believe that similar electric fields likely exist on other planets with atmospheres, such as Venus and Mars. Understanding the ambipolar field on Earth opens new possibilities for studying how these fields influence planetary atmospheres and their potential habitability.

As researchers continue to explore the ambipolar field’s impact, this discovery marks a major step forward in our quest to understand the forces shaping our world and others in the solar system. The journey of exploration and discovery continues, as we delve deeper into the mysteries of the universe, equipped with new knowledge and tools to unlock the secrets of the cosmos.