Did Space Weather Help Down a US Army Helicopter?

In truth, most everything went wrong on Takur Ghar in the pre-dawn hours of March 3, 2002. That morning, the plan was to insert a US Navy SEAL team on the summit of the 10,000 foot peak Takur Ghar to act as an observation post for operations in the valley below. Numerous delays pushed the insertion further and further toward daylight and, eventually, the SEALs were ordered to land not on the planned nearby ridge, a point of relative safety, but the peak itself. Then, everything went even more wrong.

The two helicopters carrying the SEAL team came under heavy and unanticipated fire. One was forced to crash land and the other sustained heavy losses. The SEALs on the ground found themselves in an intense battle. Two more helicopters were dispatched to the area carrying a quick-reaction rescue team. One of the two, known as Razor 1, was misdirected to land in the battle's "hot" zone. The misdirected copter was hit by an RPG and crashed. The root of the communications failure has remained something of a mystery.

What had happened is that Razor 1, a MH-47 Chinook copter, missed a critical message, delivered by satellite radio, warning the helicopter away from the peak and firefight. According to a geophysicists based at Johns Hopkins University's Applied Physics Laboratory, the reason for this communications failure may have been a perfect storm of space weather.

Specifically, the suggested cause is ionospheric "bubbles," which are regions that have an abnormally low density of electrons. These bubbles, a likely result of the coincidental peak of Solar Cycle 23, could have been enough to decrease the signal-to-noise ratio of the transmission enough to effectively block it. While official reports blamed terrain interference and poor radio performance, it's possible that these atmospheric radio bubbles could have colluded with those other factors to push a would-be communications difficulty full-on into communications failure.

A post at Nature.com explains further:

Plasma populates the upper layers of Earth's ionosphere during the day, when sunlight breaks atmospheric particles into their charged constituents. At sunset, turbulence can develop as the plasma recombines, forming buoyant regions of lower density than their surroundings. These bubbles typically form near the magnetic equator, which snakes around the planet at low latitudes. During the night, they can grow to be tens of kilometres wide and extend towards the poles for thousands of kilometres. Smaller-scale turbulence inside these writhing tubes distorts radio waves that pass through it the way heat roiling above hot tarmac sets distant images dancing.

The APL researchers' theory isn't conclusive, but data from NASA's TIMED satellite, which happened to be above Afghanistan that morning, indicates a plasma bubble about 500 kilometers above the battlefield at the time of the battle. The primary effect would have likely been small, but as the signal bounced around neighboring mountain peaks, it would have been amplified, possibly to the intensity needed to black a radio transmission. At the very least, the findings should help with future forecasting.

"The events of 4 March 2002 motivated us to develop the Mesoscale Ionospheric Simulation Testbed model," the APL team writes in Space Weather, "which can be used to improve warnings of potential UHF outages during future military operations." As we once again head into wartime, that might be a very valuable resource.