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Coronal Mass Ejections from the Sun: How do they Slow Down in Interplanetary Space ?

Image shows a very large coronal mass ejection (CME) blasting off into space on December 2, 2002 (Image Source: SOHO (ESA & NASA))

Image shows a very large coronal mass ejection (CME) blasting off into space on December 2, 2002 (Image Source: SOHO (ESA & NASA))

Sun, the big bright star that supports life on Earth, can also influence the weather in interplanetary space. Much like the ongoing travails of the Curiosity rover with a solar blast directed toward the Mars, technologies such as satellite and mobile communications whose operation depends on the immediate space environment of the Earth are vulnerable to the Sun’s dynamics.

The extended atmosphere of the Sun, referred to as the corona, fills the solar system across its various planets and satellites. The steady hot wind of the corona carries along electrically charged particles, which are carefully filtered out by the Earth’s geomagnetic field.

There are times when the Earth’s geomagnetic field cannot take the Sun’s blast as Prasad Subramanian, associate professor at IISER Pune working in the area of solar physics, explains,” The solar corona often undergoes eruptions and ejects portions of itself. These transients, called coronal mass ejections (CMEs) comprise hot, ionized plasma enclosed by magnetic fields. When Earth-directed CMEs interact with the Earth’s magnetic field, they often give rise to substantial disruptions to the geomagnetic field and electrical current systems in the Earth’s upper atmosphere. Together, these effects are called geomagnetic storms and they can affect a wide swathe of technology related human activities.”

Scientists like Subramanian are therefore interested in understanding the impact of CME-driven geomagnetic storms and the Sun-Earth connection in general.

In a recently published paper in Geophysical Research Letters, Subramanian and his collaborators from Mexico have made an important breakthrough on understanding the manner in which CMEs propagate through the interplanetary medium between the Sun and the Earth (Subramanian, Lara and Borgazzi 2012). The authors have analyzed physical processes responsible for slowing down CMEs after they leave the Sun, such as the drag force acting on fast CMEs.

“This drag prescription can be used profitably in sophisticated numerical simulations of CME propagation and thereby obtain accurate predictions of Sun-Earth travel times. This will be a vital component in a reliable warning system for geomagnetic storms,” says Subramanian describing the relevance of their findings.

This paper titled “Can solar wind viscous drag account for CME deceleration?” has been published in Geophysical Research Letters (2012:39, CiteID L19107) and authored by Prasad Subramanian (IISER Pune, India), Alejandro Lara and Andrea Borgazzi (UNAM, Mexico).

You can learn more about Dr Subramanian’s research here.

-With inputs from Prasad Subramanian

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