The Ambipolar Field: Earth’s Invisible Electric Force Launching Atmosphere

Introduction: The Discovery of the Third Field

For centuries, our understanding of the forces that shape Earth has been dominated by two invisible giants: gravity and magnetism. Gravity is the master architect, holding our feet to the ground, keeping the moon in orbit, and retaining the thick blanket of air that allows life to thrive. Magnetism is the protector, the shield that deflects the searing radiation of the solar wind and paints the sky with the aurora. These two fields have been the pillars of planetary physics, the known variables in the equation of our existence.

But for more than sixty years, scientists have suspected that a third player was hiding in the shadows—a subtle, pervasive force that, despite its weakness, was fundamentally altering the evolution of our atmosphere. It was a ghost in the data, a theoretical necessity required to explain phenomena that gravity and magnetism could not. In August 2024, the ghost was finally caught.

NASA’s Endurance rocket mission, launched from the frozen archipelago of Svalbard near the North Pole, successfully measured Earth’s Ambipolar Electric Field for the first time. This discovery changes everything. It confirms that our planet is wrapped in a planet-wide electric force field, as fundamental as gravity, that has been quietly launching our atmosphere into space for billions of years.

"It’s a whole new planetary energy field that’s never been measured before," said Glyn Collinson, principal investigator of the Endurance mission at NASA’s Goddard Space Flight Center. "It’s been sitting there under our noses for 60 years, but we finally have the technology to measure it."

This field, measured at a mere 0.55 volts, may sound insignificant—weaker than a standard watch battery. Yet, across the vast vertical expanse of the atmosphere, this tiny potential creates a "sky-hook" strong enough to toss heavy oxygen atoms into space and launch hydrogen at supersonic speeds, defying the pull of gravity. Its discovery not only solves a decades-old mystery about Earth’s "polar wind" but also forces us to rethink the habitability of every planet in the cosmos, from our neighbors Venus and Mars to the distant exoplanets orbiting alien stars.

Part I: The Mystery of the Polar Wind

To understand the magnitude of this discovery, we must look back to the dawn of the Space Age. In the late 1960s, as humanity was preparing to take its first steps on the Moon, satellites orbiting Earth began to detect something baffling.

When spacecraft flew over the Earth’s poles, they encountered a stream of particles flowing outward from the atmosphere. This was the "polar wind." While scientists expected some atmospheric loss due to intense solar heating—a process known as Jeans escape, where sunlight energizes particles enough to break free of gravity—the polar wind didn't fit the model.

The "Cold" Supersonic Paradox

The particles in the polar wind were traveling at supersonic speeds, yet they were "cold." In thermal escape, particles move fast because they are hot; their thermal energy overcomes gravitational binding. But these particles showed no signs of being heated. They were effectively surfing a wave that shouldn't exist, accelerating into the void without a clear source of energy.

If gravity were the only force acting on them, these particles should have remained trapped in the atmosphere. The heavy ions, particularly oxygen, should have sunk like stones. Instead, they were being lifted. It was as if the atmosphere had a leak, a chimney at the top of the world where the air was being siphoned off by an unknown mechanism.

The Helium Budget Crisis

At the same time, geochemists were struggling with a separate accounting problem: the "Helium Paradox." Earth’s crust constantly produces helium through the radioactive decay of heavy elements like uranium and thorium. This helium seeps into the atmosphere. Based on the production rate, and assuming only thermal escape mechanisms (Jeans escape) were at play, Earth’s atmosphere should be saturated with helium.

But it isn't. The observed amount of helium in our atmosphere is roughly 1/1000th of what calculations predicted. Something was scrubbing helium from our sky much faster than thermal evaporation could explain. The "residence time" of a helium atom was calculated to be around 2 million years, yet thermal models suggested it should stick around for billions.

In 1968, physicists Sir Ian Axford, Peter Banks, and Thomas Holzer proposed a solution that would link these mysteries. They hypothesized that an electric field must exist in the ionosphere—a layer of the upper atmosphere. They theorized that this field was "ambipolar," meaning it worked in two directions, affecting positive and negative charges differently, and was strong enough to pull ions out of the atmosphere against the force of gravity.

For decades, this remained a brilliant but unproven theory. The predicted field was so incredibly weak—spanning hundreds of miles of altitude but summing up to less than a single volt—that no instrument existed sensitive enough to detect it. It was a phantom force, mathematically necessary but observationally invisible.

Part II: The Mechanism of the Ambipolar Field

So, how does this invisible force work? The answer lies in the chaotic dance of subatomic particles at the edge of space.

At an altitude of around 150 miles (250 kilometers), in the ionosphere, the sun’s harsh ultraviolet radiation shreds atoms apart. It knocks electrons loose from their parent atoms, creating a soup of negatively charged electrons and positively charged ions (plasma).

The Great Tug-of-War

This creates a fundamental conflict.

Electrons are incredibly light and energetic. If left to their own devices, they would instantly shoot outward into space, escaping Earth’s gravity with ease.
Ions (like oxygen and hydrogen atoms missing an electron) are heavy. They feel the full weight of Earth’s gravity and want to sink back down toward the surface.

However, the laws of electromagnetism hate charge separation. The atmosphere "wants" to remain electrically neutral. As the light electrons try to sprint into space and the heavy ions try to sink, a tension builds between them. The negative electrons pull up, and the positive ions pull down.

This tension creates a tether—an electric field. The electrons, in their attempt to escape, are dragged back by the ions. Conversely, the ions, in their attempt to sink, are lifted up by the electrons. This is the Ambipolar Field. It is "ambipolar" because it is bidirectional, mediating the struggle between the two poles of charge.

The Conveyor Belt to Space

Glyn Collinson uses the analogy of a dog on a leash. The electron is a tiny, hyperactive dog trying to run away (into space). The ion is the sluggish owner trying to stay put (gravity). The leash is the ambipolar field. The dog pulls the owner along, lifting the heavy ions higher than they would ever go on their own.

The result is an expansion of the atmosphere. The "scale height"—a measure of how quickly the atmosphere thins out as you go up—increases dramatically. The Endurance mission found that this field inflates the ionosphere by 271%. It literally puffs up the Earth’s atmosphere, pushing heavy oxygen ions to altitudes where the solar wind can strip them away, and launching light hydrogen ions out entirely.

Part III: The Endurance Mission

Validating a 60-year-old theory required a mission of extreme precision and daring. The field strength to be measured was anticipated to be roughly 0.5 to 1 volt over a vertical distance of several hundred kilometers. To put that in perspective, detecting this voltage drop is like trying to measure the change in potential of a watch battery stretched from Philadelphia to Washington D.C.

The Rocket: Oriole III-A

NASA engineers at the Wallops Flight Facility designed the Endurance, a sounding rocket capable of a suborbital trajectory that would pierce the heart of the polar wind. The rocket chosen was a three-stage Oriole III-A solid-fueled vehicle. Unlike orbital satellites that zip around the planet horizontally, a sounding rocket flies in a parabolic arc—straight up and straight down—allowing it to take a vertical slice of data through the atmosphere.

The Location: Svalbard

The launch site had to be perfect. The mission needed to fly through the "cusp"—the funnel-shaped region near the magnetic pole where Earth’s magnetic field lines are open to space, allowing the polar wind to flow freely. The only place in the world suitable for this was the Svalbard Rocket Range in Ny-Ålesund, Norway, the northernmost settlement on Earth.

In May 2022, the team assembled in the freezing Arctic. The logistics were a nightmare. "Polar bears were the least of it," Collinson recalled. "We had war and plague." The invasion of Ukraine had heightened geopolitical tensions, and the team faced COVID-19 outbreaks during their travel. They also had to wait for the weather to clear; launching a rocket requires specific wind conditions to ensure the safety of the range.

The Instrument: The Photoelectron Spectrometer

The "secret sauce" of the mission was the Photoelectron Spectrometer (PES). Standard voltmeters couldn't simply probe the air to measure the potential. Instead, the team used a clever proxy: photoelectrons.

When sunlight hits helium atoms in the atmosphere, it knocks off electrons at very specific, known energy levels (specifically related to the Helium-II 304 Angstrom spectral line). These electrons act as "tracer bullets." As they travel through the electric field, their speed changes. By measuring the energy of these electrons at different altitudes with extreme precision, the instrument could back-calculate the strength of the electric field they had passed through.

The PES used a hemispherical electrostatic analyzer—a device that bends the path of electrons using electric fields. Only electrons of a specific energy make it through the bend to the detector. By sweeping the voltage, the instrument could build a high-resolution map of the electron energies.

The Launch: May 11, 2022

On May 11, the skies over Svalbard cleared. At 01:31 GMT, the Endurance roared off the pad. It ascended rapidly, piercing the lower atmosphere and reaching an apogee (peak altitude) of 768.03 kilometers (477 miles).

For 19 minutes, the rocket bathed in the polar wind, its instruments sipping the thin plasma of the ionosphere. It measured the electrons streaming past, recording their subtle energy shifts. Then, it fell back to Earth, splashing down in the Greenland Sea.

The data was retrieved, and the analysis began.

Part IV: The Measurement—0.55 Volts

When the numbers were crunched, the result was undeniable. The Endurance rocket had detected a change in electric potential of 0.55 volts (with an uncertainty of ±0.09 volts) between the altitudes of 250 km and 768 km.

This number—0.55 volts—is the "magic number" of the ambipolar field.

Why 0.55 Volts Matters

To a human, half a volt is nothing. You wouldn't feel it if you touched it. But to a hydrogen ion (a proton), this is a massive force.

Gravity vs. Electric Force: The gravitational binding energy of a hydrogen ion at that altitude is weak. The 0.55-volt field exerts an outward force on hydrogen ions that is 10.6 times stronger than gravity.
Supersonic Launch: This force acts like a railgun. It accelerates the hydrogen ions upward, blasting them past the speed of sound (relative to the heavy ions) and ejecting them into space to form the polar wind. This perfectly explains the "cold supersonic" mystery; the particles aren't hot (thermally random), they are driven by a directed field.

For heavier ions like Oxygen (O+), the effect is different but equally profound. Oxygen is 16 times heavier than hydrogen. The 0.55-volt field isn't enough to launch oxygen directly into space against gravity (it effectively reduces the weight of oxygen by about half). However, this "weight loss" puffs up the oxygen layer, lifting it to great heights where other mechanisms—like wave-particle interactions from solar storms—can grab it and strip it away.

This confirms that the ambipolar field is the "conveyor belt" that feeds the heavy atmosphere to the upper regions where it can be lost.

Part V: A Tale of Three Planets—Earth, Venus, and Mars

The discovery of Earth’s ambipolar field provides a "Rosetta Stone" for understanding the atmospheric history of our neighbors. If every planet with an atmosphere generates an ambipolar field, then this field has played a critical role in determining which planets kept their water and which ones died.

Venus: The Electric Monster

Venus is often called Earth’s twin, but it is a hellscape. It has a crushing carbon dioxide atmosphere and is bone-dry. Why did Venus lose its water?

In 2016, the ESA’s Venus Express mission measured the electric potential of Venus. It found a monster field: 10 volts.

Recall that Earth’s field is 0.55 volts. Venus’s field is nearly 20 times stronger.

This "Electric Wind" on Venus is so powerful that it can rip oxygen ions straight out of the atmosphere without needing any help from solar storms. When UV light splits water molecules (H2O) on Venus, the hydrogen escapes easily. But the 10-volt field is strong enough to drag the heavy oxygen out, too. This effectively vacuumed the water components off the planet, leaving it desiccated.

Why is Venus’s field so strong? It likely relates to the intensity of sunlight (being closer to the sun) and the density of its ionosphere, creating a more violent tug-of-war between electrons and ions.

Mars: The Stripped Wanderer

Mars is the opposite story. It is a small, cold world with a thin atmosphere. We know Mars once had oceans. Where did they go?

The MAVEN (Mars Atmosphere and Volatile EvolutioN) mission has been studying this. While Mars lacks a global magnetic field to protect it, it does have an ambipolar field. Recent models and data suggest this field plays a major role in "sputtering" away the Martian sky. Without the magnetic shield, the solar wind interacts directly with the ionosphere, and the ambipolar field helps lift the atmosphere up to be stripped away.

Earth: The Goldilocks Field

Earth’s 0.55-volt field appears to be a "Goldilocks" value.

It is strong enough to eject hydrogen (which we can spare, as we have plenty in our oceans).
It is weak enough that it doesn't strip away our oxygen directly. It lifts the oxygen, but gravity is still strong enough to keep most of it, unless a major solar storm hits.

This delicate balance may be one of the unsung reasons why Earth remains habitable. We are losing atmosphere, but at a rate slow enough that volcanic outgassing and biological processes can replenish it.

Part VI: The Universal Implications for Life

The discovery of the ambipolar field reverberates far beyond our solar system. As we point our telescopes at exoplanets orbiting distant stars, we are desperate to find a "second Earth."

Traditionally, we define the "Habitable Zone" based on temperature—the distance from a star where liquid water can exist. But the ambipolar field adds a new dimension to this definition.

The Electric Filter

If an exoplanet is in the habitable zone but possesses a "Venus-like" ambipolar field (perhaps due to being around a more active star with intense UV output), it might be stripping its own water away regardless of the temperature. The ambipolar field acts as a planetary "valve," regulating how fast an atmosphere leaks.

Space Weather and Habitability

We now know that space weather (solar flares, coronal mass ejections) doesn't just batter the magnetic shield; it interacts with the ambipolar field. When the ionosphere is heated by a solar storm, the electron pressure increases, potentially dialing up the voltage of the ambipolar field and temporarily increasing the rate of atmospheric loss.

Understanding this dynamic is crucial for assessing the long-term survival of atmospheres on planets orbiting Red Dwarf stars (M-dwarfs). These stars are notorious for violent flares. If these flares spike the ambipolar fields of orbiting planets, they could sterilize worlds that otherwise look perfect for life.

Conclusion: The New Era of Atmospheric Physics

The measurement of the ambipolar field is a triumph of persistence and engineering. It closes the book on the 1968 hypothesis and opens a new volume in planetary science.

We now acknowledge three fundamental fields shaping our planet:

Gravity: The holder.
Magnetism: The shield.
Ambipolar Electricity: The launcher.

This "third field" is a fundamental part of how Earth works. It is the breath of the planet, a constant, electric exhalation that connects our atmosphere to the vacuum of space. As Glyn Collinson put it, "It’s fundamental to the DNA of our planet."

The Endurance mission was just the beginning. Now that we know the field is there and we know how to measure it, future missions can map its structure globally. We can build instruments to measure it on Mars and eventually, perhaps, on probes sent to other star systems.

For now, we can look up at the aurora and know that hidden amidst those curtains of light is an invisible electric ladder, rung by rung, lifting the sky into the stars, shaping the past, present, and future of life on Earth.