China and Russia have jointly conducted a controversial series of experiments to modify Earth's atmosphere with high-frequency radio waves.

From a Russian installation called the Sura Ionospheric Heating Facility near the town of Vasilsursk, east of Moscow, scientists emitted high-frequency radio waves to manipulate the ionosphere, while the China Seismo‐Electromagnetic Satellite (CSES) measured the effects on plasma disturbance from orbit.

It's not the first time research like this has been conducted, but news of the China-Russia developments – conveyed via a published paper on the experiments, and a recent article in the South China Morning Post – has ignited concerns over the potential military applications of this kind of science.

That's because the ionosphere, and the ionised gas (plasma) that inhabits it, is crucial to radio communication. By selectively disturbing the charged particles that make up this part of the upper atmosphere, scientists or even governments could theoretically boost or block long-range radio signals.

Even these preliminary experiments – conducted in June, and ostensibly designed as a test-case for future related ionosphere research – had extreme effects.

In one of the experiments, the affected area of ionosphere disturbance reportedly covered 126,000 square kilometres (49,000 square miles). In another test, ionised gas in the atmosphere increased in heat by 100 degrees Celsius (212 degrees Fahrenheit).

For their part, those involved claim the research is purely scientific, and harmless to the atmosphere.

"We are not playing God," an unidentified researcher who asked to remain nameless told the South China Morning Post.

"We are not the only country teaming up with the Russians. Other countries have done similar things."

On that score, at least, there's no dispute.

The Sura base was established by the Soviet Union in the early 1980s, but is said to have been the inspiration for an even larger atmospheric heating facility in the US called the High Frequency Active Auroral Research Program (HAARP), which was built in Alaska about a decade later.

HAARP – which is a considerably more powerful ionospheric pump facility than Sura – was initially partly funded by the US military, but is now administered by the University of Alaska Fairbanks.

The US Air Force hasn't given up on atmospheric manipulation though, and among other projects has in recent times investigated dropping plasma bombs of charged particles into the upper atmosphere to see how that affects the ionosphere.

Not to be left out, China is also reportedly building an advanced ionosphere heater in the city of Sanya, on the island province of Hainan at the south of China, which the Post suggests could manipulate the ionosphere over the entire South China Sea.

There's no proof of anything nefarious going on – although Russia has been accused by various parties of jamming GPS signals this year, and ionospheric manipulation experiments could hypothetically have been involved.

Still, we need to be careful here; as many researchers have said, this field of science has too long been plagued by conspiracy theories drummed up by a paranoid blogosphere.

That said, even some in the ionosphere manipulation research community have found the recent announcements about the June experiments a little strange.

"Such international cooperation is very rare for China," physicist and engineer Guo Lixin from China's Xidian University, who was not involved in the experiments, told the Post.

"The technology involved is too sensitive."

The findings are reported in Earth and Planetary Physics.