'Strongest solar magnetic field measured on Sun'

Astronomers in Japan have observed the strongest magnetic field ever directly measured on the surface of the Sun.
The researchers using the HINODE spacecraft determined that the field was generated as a result of gas outflow from one sunspot pushing against another sunspot.
"HINODE's continuous high-resolution data allowed us to analyse the sunspots in detail to investigate the distribution and time evolution of the strong magnetic field and also the surrounding environment," said Joten Okamoto from the National Astronomical Observatory of Japan (NAOJ).
"Finally, the longtime mystery of the formation mechanism of a stronger field outside an umbra than in the umbra, has been solved," Okamoto said.

Magnetism plays a critical role in various solar phenomena such as flares, mass ejections, flux ropes, and coronal heating.
Sunspots are areas of concentrated magnetic fields. A sunspot usually consists of a circular dark core (the umbra) with a vertical magnetic field and radially-elongated fine threads (the penumbra) with a horizontal field.

The penumbra harbours an outward flow of gas along the horizontal threads.
The darkness of the umbrae is generally correlated with the magnetic field strength. Hence, the strongest magnetic field in each sunspot is located in the umbra in most cases.
Okamoto and Takashi Sakurai from NAOJ were analysing data taken by the Solar Optical Telescope onboard HINODE, when they noticed the signature of strongly magnetised iron atoms in a sunspot.

Surprisingly the data indicated a magnetic field strength of 6,250 gauss. This is more than double the 3,000 gauss field found around most sunspots, researchers said.
Previously, magnetic fields this strong on the Sun had only been inferred indirectly.
More surprisingly, the strongest field was not in the dark part of the umbra, as would be expected, but was actually located at a bright region between two umbrae.