CHICAGO: New observations of the Sun gathered by a Japanese probe may finally explain why its outer atmosphere burns white-hot in contrast to its relatively cool surface, scientists said on Thursday.

The riddle of the star’s white-hot atmosphere, which at several million degrees kelvin is 200 to 300 times warmer than the surface, has intrigued solar physicists for more than 50 years.

The experts tended to fall into two camps, speculating that the extraordinary warmth of the outer atmosphere, or corona, was due to either miniature solar flares or atmospheric (Alfven) waves.

Several research teams had reported evidence of these Alfven waves, which could potentially heat the corona to extreme temperatures by releasing energy as they travel outward from the Sun along magnetic field lines.

The data collected by “Hinode” (“Sunrise” in Japanese), which can precisely measure small changes in the Sun’s magnetic field, changed all that.

Images taken by the probe’s Solar Optical Telescope suggest that the chromosphere, the region sandwiched between the solar surface and the corona, is riddled with Alven waves, oscillating at 10-25km per second. The energy generated by the waves is sufficient to heat the corona which is probably most familiar to the layman as the white band of light that can be seen during the fleeting darkness of a total solar eclipse.

The satellite, launched in September 2006, has provided scientists with an unprecedented peek at the structures and magnetic fields within the Sun’s high-energy plasma.

—AFP