NASA explorer decodes interstellar magnetic field

Washington, Feb 27: What is out there at the edge of our solar system? Scientists using data from NASA's Interstellar Boundary Explorer (IBEX) have pinned down an interstellar magnetic field which lies at the very edge of the giant magnetic bubble surrounding our solar system called the heliosphere.

Immediately after its 2008 launch, IBEX spotted a curiosity in a thin slice of space: More particles streamed in through a long, skinny swath in the sky than anywhere else.

The origin of the so-called "IBEX ribbon" was unknown - but its very existence opened doors to observing what lies outside our solar system, the way drops of rain on a window tell you more about the weather outside.

The new study, published in Astrophysical Journal Letters, precisely determines the strength and direction of the magnetic field outside the heliosphere.

Such information gives us a peek into the magnetic forces that dominate the galaxy beyond, teaching us more about our home in space.

"The theory says that some solar wind protons are sent flying back towards the sun as neutral atoms after a complex series of charge exchanges, creating the IBEX ribbon," explained Eric Zirnstein, space scientist at the Southwest Research Institute in San Antonio, Texas.

"Simulations and IBEX observations pinpoint this process - which takes anywhere from three to six years on average - as the most likely origin of the IBEX ribbon," he added.

A giant bubble, known as the heliosphere, exists around the Sun and is filled with what's called solar wind, the sun's constant outflow of ionized gas, known as plasma.

When these particles reach the edges of the heliosphere, their motion becomes more complicated.

Outside the heliosphere lies the interstellar medium, with plasma that has different speed, density, and temperature than solar wind plasma, as well as neutral gases.

These materials interact at the heliosphere's edge to create a region known as the inner heliosheath.

Some solar wind protons that flow out from the sun to this boundary region will gain an electron, making them neutral and allowing them to cross the heliopause.

"Only Voyager 1 has ever made direct observations of the interstellar magnetic field, and those are close to the heliopause, where it's distorted," Zirnstein added.

"But the new analysis provides a nice determination of its strength and direction farther out," he noted.

"The new findings can be used to better understand how our space environment interacts with the interstellar environment beyond the heliopause," said Eric Christian, IBEX programme scientist.

IANS