The seeds of solar storms

NCAR scientists map the magnetism of coronal disturbance

On a shelf next to Sarah Gibson's desk lies a Slinky. This perennial children's toy is a simple thing: a single piece of narrow-gauge wire, twisted into a column of curlicues.

Some people keep Slinkies or cushioned balls or other toys on their desks as stress relievers. In Gibson's case, there's a different motive. The NCAR-s-cientist finds Slinkies a useful metaphor for the coiled magnetic fields that can spew from the Sun and wreak cosmic havoc on Earth.

Gibson is part of a close-knit group of researchers at NCAR's High Altitude Observatory (HAO) who study the solar corona. No more than a few hundred people around the world devote their careers to this vast region, which extends from a few thousand kilometers above the solar surface to a distance many times the Sun's diameter. Much hotter and much thinner than the roiling plasma below, the corona courses with magnetic and thermal energy, yet it's visible only during eclipses or with specialized instruments.

A few of NCAR's coronal specialists (clockwise from top left): Holly Gilbert, Sarah Gibson, David Foster, and Giuliana de Toma. (Photo by Carlye Calvin.)

Despite its camera-shy nature, the corona is of far more than theoretical interest. It's the launching pad for what's now called space weather. Streams of energized particles--the solar wind--blow from the corona to fill the whole solar system. As variations in the solar wind reach Earth's outer atmosphere, they can trigger geomagnetic storms.By better understanding the corona, researchers hope to advance the science of space-weather prediction as well as our overall picture of the Sun itself.

There's fresh momentum to NCAR's coronal research. A decade's worth of data from several landmark satellites and NCAR's Mauna Loa Solar Observatory have given scientists rich coronal detail from a few choice perspectives. An NCAR instrument being tested this winter may provide an entirely new map of the corona's magnetic fields (see sidebar, page 5), and a new generation of space-based sensors is on its way.

All this may not add up to the full coronal portrait that scientists crave. But it does leave room for intense debate of the geometric kind: brainstorming sessions on how a tube of magnetic flux might twist its way out of the Sun, and long stints at the desktop, spinning brightly colored animations out of strands of coronal data.

part 1 | part 2 | part 3

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