Solar outbursts can generate conditions for magnetic slingshot: Study

November 22nd, 2007 - 5:41 pm ICT by admin  

Washington, November 22 (ANI): US scientists have uncovered evidence that solar outbursts can generate conditions that could slingshot matter into the Earth’s magnetic environment at speeds higher than 1000 km/s.

The findings are based on a comparison between observations from the four satellites of the European Space Agencys (ESA) Cluster mission and global simulations of the magnetosphere.

In a recent study, scientists said the outburst is caused by a Coronal Mass Ejection (CME), a massive cloud of charged particles coming from the Sun.

When CMEs occur, about 10 thousand million tonnes of charged particles are carried into the solar system. Most CMEs travelling towards Earth are harmless, but some can affect orbiting satellites or even power grids.

The scientist fraternity has been interested in for long in carrying out research on how CMEs impact the Earth’s magnetic environment, and consequently space- based and terrestrial technologies.

When the 200 million dollar AT and T Telstar 401 satellite suddenly fell silent on 11 January 1997, cutting TV coverage to millions of viewers and was declared permanently out of service six days later, many scientists believed that it was the result of it being struck by a CME.

It is also believed that the detection of accelerated matter on the side of the magnetosphere is a sign of the occurrence of magnetic reconnection, a process by which terrestrial and solar magnetic fields interact.

However, the new study, published in the Annales Geophysicae, shows that a mechanism other than magnetic reconnection can accelerate matter.

During the passage of a CME at Earth on 25 November 2001, the four Cluster satellites skimming the border of the magnetosphere, in a region called the magnetosheath, detected plasma accelerated to speeds of 1040 km/s, while the speed of the solar wind was only 650 km/s.

According to the scientists, such an acceleration has been observed in the past with or without the presence of a CME.

Though it is usually a sign of magnetic reconnection, the studys authors say the case was different on November 25, 2001.

Combining Cluster observations from that day with global Magneto Hydro Dynamic (MHD) simulations of the magnetosphere, the authors found that solar wind conditions characteristic of most CMEs strongly accelerated plasma.

According to them, as the CME reached the Earth, solar wind magnetic field lines got stuck in the front of the magnetosphere, before sliding sideways and accelerating plasma like a ‘magnetic slingshot’.

“We have unambiguous proof that the strong plasma acceleration observed on 25 November 2001 by Cluster was not the result of magnetic reconnection, but because of conditions created by the CME”, said Dr Lavraud, lead author at Los Alamos National Laboratory, USA.

The presence of such high-speed flows has consequences on the interaction between the solar wind and the magnetosphere. It may increase wavy or viscous interactions at magnetospheric boundaries and lead to giant, spiral auroral features, as reported early this year by Lisa Rosenqvist from the Swedish Institute of Space Physics, Uppsala, Sweden.

“This result demonstrates that not only is Cluster data indispensable, but also there is great mutual benefit in comparing global MHD simulation results with Cluster measurements,” commented Philippe Escoubet, ESA’s Cluster and Double Star project scientist. (ANI)

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