Scientists shed new light on explosive solar activity?

Space storms caused by extreme sun activity have proved to be quite a hurdle to mankind since they interfere in satellite communications and damage power grids on Earth.

Updated: Jul 02, 2012, 18:07 PM IST

London: Taking a step towards understanding the origins of extreme space storms, a team of international scientists, including those from India, have identified the first images of an upward surge of the Sun`s gases into quiescent coronal loops.
Space storms caused by extreme sun activity have proved to be quite a hurdle to mankind since they interfere in satellite communications and damage power grids on Earth.

The study published today in Astrophysical Journal Letters is the first to visualise the movement of gases at one million degrees in coronal loops solar structures that are rooted at both ends and extend out from active regions of the Sun.

The Indian collaboration in the research is led by Durgesh Tripathi of the Inter-University Centre for Astronomy and Astrophysics, Pune.

Active regions are the `cradle` for explosive energy releases such as solar flares and coronal mass ejections (CMEs), the release said, while adding that the observation will help scientists understand one of the most challenging issues in astrophysics i.E. How solar structures are heated and maintained in the upper solar atmosphere.

Solar activity is cyclical, with the next maximum forecast to occur around May 2013, and severe space weather is now listed very high on the UK’s 2012 National Risk Register of Civil Emergencies.

Based on observations from the Hinode satellite (a joint Japanese, NASA, European Space Agency and UK project), the new findings provide the first evidence of plasma upflows travelling at around 20 km per second in the one million degree active region loops.

The scientists suggest that the upflow of gases is probably the result of "impulsive heating" close to the foot-point regions of the loops.

"Active regions are now occurring frequently across the Sun.

We have a really great opportunity to study them with solar spacecraft, such as Hinode and the Solar Dynamics Observatory (SDO)," said co-author Dr Helen Mason from the University of Cambridge’s Department of Applied Mathematics and Theoretical Physics.

"Probing the heating of the Sun`s active region loops can help us to better understand the physical mechanisms for more energetic events which can impinge on the Earth?s environment.

"Previous ultraviolet images of the Sun taken by NASA`s SDO have shown large loops of hot gas guided by the Sun`s magnetic field and rooted near sunspots," she said.

Despite such remarkable developments in the observations and theory of active regions over the past few decades, the question remained as to how solar plasma is heated and rises up into the loops in the first place.

Now, the new research provides the first visualisation of plasma flow by showing the movement of gases within the loop as `blueshifts` in diagnostic images using the extreme ultraviolet imaging spectrometer (EIS) on the Hinode satellite.

Spectral lines produced by the spectrometer act like `fingerprints` or the `bar code` in a supermarket, the lines identify the multitude of elements and ions within the loop and shifts in the position of the lines provide information on the motion of the plasma.

Although the Sun is composed mainly of hydrogen and helium, there are also other trace elements, such as oxygen and iron, in the hot ionised gas within the loops, the release added.

The scientists suggest that the gas movement is caused by a process of "chromospheric evaporation" in which "impulsive heating" on a small scale can result in the heating of the solar active regions but on a larger scale can lead to huge explosions, such as solar flares or coronal mass ejections.