Radio AARDDVARK

Scientists are using bouncing radio waves to monitor the upper atmosphere and study ozone loss in the Arctic and Antarctic.

The upper atmosphere lies between forty and ninety kilometres above the Earth’s surface, and is traditionally hard to monitor since it is too low for satellites and too high for balloons. It is where high-speed electrons, protons, and X-rays from our solar system and beyond deposit their energy, which ultimately affects the Earth’s climate.

Radio waves with very low frequency, known as VLF waves, get trapped between the Earth and about 85 kilometres altitude, bouncing around the Earth in a giant waveguide. The upper boundary where the VLF waves reflect depends on how electron density varies with altitude. By measuring changes in VLF waves from a distant transmitter, scientists can infer the electron densities over a range of altitudes and watch how this changes over time.

The AARDDVARK network of VLF sensors, a joint UK-New Zealand venture lead by scientists at the British Antarctic Survey and Otago University, continuously measures waves from fixed frequency transmitters to detect changes in the waveguide. The changes can be caused by an influx of charged particles due to solar flares, solar eclipses, or red sprites, for example.

Recently scientists have combined AARDDVARK measurements with satellite data to study ozone loss. When high-energy particles strike the upper atmosphere at the poles they create chemicals that can destroy ozone. While these species are destroyed by sunlight, this is not present during the long polar winter. Ozone-destroying species can then drift downwards from their production altitudes to the upper stratosphere, where ozone concentrations are high, and destroy a lot of ozone.

AARDDVARK is the Antarctic-Arctic Radiation-belt (Dynamic) Deposition - VLF Atmospheric Research Konsortium. To find out more, visit the AARDDVARK website by following the link below.

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