Previously unknown mode of energy transfer from solar wind to Earth's magnetosphere found

Published: Friday, September 11, 2009, 13:26 [IST]
 

Washington, September 11 (ANI): Atmospheric scientists from the UCLA (University of California, Los Angeles) have discovered a previously unknown basic mode of energy transfer from the solar wind to the Earth's magnetosphere, a finding that could improve the safety and reliability of spacecraft that operate in the upper atmosphere.

"It's like something else is heating the atmosphere besides the sun. This discovery is like finding it got hotter when the sun went down," said Larry Lyons, UCLA professor of atmospheric and oceanic sciences and a co-author of the research.

The sun, in addition to emitting radiation, emits a stream of ionized particles called the solar wind that affects the Earth and other planets in the solar system.

The solar wind, which carries the particles from the sun's magnetic field, known as the interplanetary magnetic field, takes about three or four days to reach the Earth.

When the charged electrical particles approach the Earth, they carve out a highly magnetized region - the magnetosphere - which surrounds and protects the Earth.

This region is where communications spacecraft operate and where the energy releases in space known as substorms wreak havoc on satellites, power grids and communications systems.

The rate at which the solar wind transfers energy to the magnetosphere can vary widely, but what determines the rate of energy transfer is unclear.

"We thought it was known, but we came up with a major surprise," said Lyons, who conducted the research with Heejeong Kim, an assistant researcher in the UCLA Department of Atmospheric and Oceanic Sciences, and other colleagues.

Lyons, Kim and their colleagues analyzed radar data that measure the strength of the interaction by measuring flows in the ionosphere, the part of Earth's upper atmosphere ionized by solar radiation.

The results surprised them.

"Any space physicist, including me, would have said a year ago there could not be substorms when the interplanetary magnetic field was staying northward, but that's wrong," Lyons said.

"Generally, it's correct, but when you have a fluctuating interplanetary magnetic field, you can have substorms going off once per hour," he added.

"Heejeong used detailed statistical analysis to prove this phenomenon is real. Convection in the magnetosphere and ionosphere can be strongly driven by these fluctuations, independent of the direction of the interplanetary magnetic field," he said.

The strength of the flows depended on the strength of the fluctuations.

"So rather than the picture of the connection between the magnetic field of the sun and the Earth controlling the transfer of energy by the solar wind to the Earth's magnetosphere, something else is happening that is equally interesting," said Lyons. (ANI)

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