Our planet is being bombarded by high-energy particles unleashed by the strongest solar storm since 2005, scientists say.
The charged particles are mostly a concern for satellites - which they can disrupt - and astronauts.
But they can also cause communication problems for aircraft travelling near the poles.
The geomagnetic storm has been caused by a potent flare that erupted from the Sun at 0400 GMT on Monday.
The effects are likely to be felt on Earth throughout Wednesday.
A more benign effect of the outpouring of particles is the ability to see aurorae, or "Northern lights", farther south than is usually possible.
A spokesman for US space agency Nasa said that flight surgeons and solar scientists have modelled the flare's predicted effects.