Two Indian astrophysicists with international collaborators have provided the first direct observation evidence that explains the mechanism that gives rise to jet-like eruptions of solar material everywhere observed on the surface of the Sun.
Tanmoy Samanta and Dipankar Banerjee are part of an international team of 12 members whose observations might also reveal an old puzzle why the atmosphere outside the Sun, or solar corona, is hotter than its surface.
Their study showed that the interaction of magnetic fields of opposite polarity – North and South – through a process that solar physicists call magnetic flux cancellation provides energy for eruptions called solar spicules.
Their findings, based on observations through telescopes in the US, were published in the journal Science on Friday.
An Italian astronomer Father Angelo Secchi in 1877 first documented spicules – emission of material like geysers that continuously erupted from the surface of the Sun, moving at speeds of about 100 km per second and reaching lengths of up to 9,000 km before collapsing.
Spicules collapse in 5 to 10 minutes but are everywhere – astronomers estimate that about one million spicules are in the Sun's atmosphere at any given moment.
New observations also show that spicules transfer heat to the corona which scientists say can explain the high temperature of the corona around one million degrees Celsius compared to the surface temperature of the Sun around 6,000 ° C.
"The high temperature of the corona is a long-standing mystery," said Samanta, a research scientist at the earth and space science school at Peking University, Beijing, China, and lead author of the research paper.
The temperature in the Sun's core is more than 15 million ° C but it cools to around 6,000 ° C near the surface. "We expect temperatures to drop even further in the outer atmosphere of the Sun, but far hotter," said Banerjee, a senior scientist at the Indian Institute of Astrophysics, Bangalore, and a team member.
Scientists working with collaborators in Austria, China, Germany, Hungary, the United Kingdom, and the US have proposed that the interaction of the magnetic fields they document could push hot spicules and solar material into the corona.
They rely on ultra-high resolution images of the sun's surface that allow them to investigate the interaction of the sun's magnetic field and how they affect eruptions from the surface of the Sun.
They say this can explain coronal heating although it is still unclear whether the heat transfer through the spicula by itself can be enough to explain the high temperature of the corona.