The Sun, glowing with a surface temperature of about 5500 degrees Celsius, warms the Earth with its salutary light. Meanwhile the Sun’s hot outer layer (the corona), with its temperature of over a million degrees, ejects a wind of charged particles at a rate equivalent to about one-millionth of the moon’s mass each year. Some particles bombard the Earth, producing radio static, auroral glows, and (in extreme cases) disrupted global communications. Astronomers can only partially explain two longstanding, related questions: how is the corona heated to temperatures so much hotter than the surface? And how does the corona produce the wind? The answers to both involve turbulence in the Sun’s atmosphere, and magnetic fields.
More here Stellar winds.