Scientists observe elusive oscillations in Suns corona

A team of US astronomers have for the first time observed elusive oscillations in the Suns corona, known as Alfven waves.

Washington, Aug 31 : A team of US astronomers have for the first time observed elusive oscillations in the Sun's corona, known as Alfven waves.

Alfven waves are fast-moving perturbations that emanate outward from the Sun along magnetic field lines, transporting energy. Although they have been detected in the heliosphere outside the Sun, they have never before been viewed within the corona, which is the outer layer of the Sun's atmosphere.

Alfven waves are difficult to detect partly because, unlike other waves, they do not lead to large-intensity fluctuations in the corona. In addition, their velocity shifts are small and not easily spotted.

Scientists say the discovery could throw more light into the fundamental behaviour of solar magnetic fields, eventually leading to a fuller understanding of how the Sun affects Earth and the solar system.

"Alfven waves can provide us with a window into processes that are fundamental to the workings of the Sun and its impacts on Earth," said lead author Steve Tomczyk of the National Center for Atmospheric Research (NCAR).

"Our observations allowed us to unambiguously identify these oscillations as Alfven waves. The waves are visible all the time and they occur all over the corona, which was initially surprising to us," said coauthor Scott McIntosh of the Southwest Research Institute in Boulder.

To observe the waves, Tomczyk and his co-researchers turned to an instrument developed at NCAR over the last few years.

The coronal multichannel polarimeter, or CoMP, uses a telescope at the National Solar Observatory in Sacramento Peak, New Mexico, to gather and analyze light from the corona, which is much dimmer than the Sun itself. It tracks magnetic activity around the entire edge of the Sun and collects data with unusual speed, making a measurement as frequently as every 15 seconds.

The instrument enabled the research team to simultaneously capture intensity, velocity, and polarization images of the solar corona. Those images revealed propagating oscillations that moved in trajectories aligned with magnetic fields, and travelled as fast as nearly 2,500 miles per second.

The scientists said that tracking the speed and direction of the waves had enabled them to infer basic properties of the solar atmosphere, such as the density and direction of magnetic fields.

They said the waves could provide answers to questions that have puzzled physicists for generations, such as why the Sun's corona is hundreds of times hotter than its surface.

The research could also help scientists better predict solar storms that spew thousands of tons of magnetized matter into space, sometimes causing geomagnetic storms on Earth that disrupt sensitive telecommunications and power systems, they said.

By learning more about solar disruptions, scientists may be able to better protect astronauts from potentially dangerous levels of radiation in space. "If we want to go to the moon and Mars, people need to know what's going to happen on the Sun," said Tomczyk.

The research is being published this week in Science.

ANI