170834
170902
Skywatching

Story of a solar storm

Over days, stresses had been building up in a big magnetic loop extending upward from the surface of the Sun.

The solar wind, flowing outward at hundreds of kilometres a second, was dragging it upward, stretching it. In addition, the movement of the foot points of the loop and the encroachment of other growing loops further increased the strain.

To start the story properly, we need to step back a bit. Many articles and books describe the Sun and other stars as balls of hot gas. Stars are far more complicated than that.

It's obvious, a ball of hot gas would be a fuzzy blob. Instead. we see the Sun has something like a surface, with sunspots and many other complex structures. This is all due to an additional ingredient, magnetic fields.

In our every-day lives, magnetic fields are invisible. We know they are there because they can pull themselves hard onto ferrous surfaces, like refrigerator doors, keeping shopping lists in place. However, this is because we live in a world of low temperatures.

At temperatures of thousands or millions of degrees, the atoms making up the air break up. At the temperatures we live in, atoms consist of a nucleus surrounded by a cloud of orbiting electrons.

At solar temperatures, the nuclei of the atoms cannot hang onto all their electrons and some, or even all of them wander off on their own. The gas has become ionized; it is now a plasma.

Unlike un-ionized air, plasmas conduct electricity, which means they stick to magnetic fields, and vice versa, producing something, a "magnetoplasma,” which is like rubber or elastic. You can stretch it, twist it and make things out of it, like huge magnetic loops.

When the Sun formed some 4.5 billion years ago, it collected not only a huge amount of gas and dust, the raw material we use to make stars, it also dragged in a lot of cosmic magnetic fields too.

These mix with the churning plasma inside the Sun, generate electric currents, which in turn generate even stronger magnetic fields. These sit inside the Sun like huge ropes and tangles of magnetoplasma.

Sometimes, these get dragged up to the surface and erupt into space as huge magnetic loops, loaded with plasma.

Finally, the stresses in the loop become too much. Electric currents are generated that are too much for the plasma to carry, the magnetic fields snap close to the anchor points and the loop catapults off into space at speeds of up to thousands of kilometres a second.

This is a coronal mass ejection, or more popularly, a solar storm. We see it briefly against the bright surface of the Sun, and get bursts of radio waves from the snapping of the magnetic fields.

Then, that great blob of magnetic fields and plasma, far larger than the Earth, moves into interplanetary space and vanishes. From where it launched from the solar surface, we can estimate whether it is coming in our direction.

When a coronal mass ejection slams into the Earth's magnetic field, it can produce huge magnetic storms, causing power outages, infrastructural damage, high altitude radiation hazards, and on the plus side, auroral displays.

The effect the coronal mass ejection has on us depends on the orientation of its magnetic fields when it hits the Earth's magnetic fields. One orientation produces only minor effects. The opposite orientation produces serious consequences.

However, we cannot deduce this orientation when it is shot off the Sun. Then, for most of its 36-48 hour trip to the Earth, it is invisible.

We next learn about it when it hits solar monitoring satellites lying 1.5 million kilometres sunward of the Earth. Then we learn of the magnitude of the threat, with only15 minutes warning. This last-minute warning is a problem, and is getting a lot of attention, understandably.

  • Mars is high in the southwest after dark.
  • Jupiter and Saturn lie low in the southeast just before dawn.
  • The Moon will reach Last Quarter on the 4th.

COMMENTS WELCOME

Comments are pre-moderated to ensure they meet our guidelines. Approval times will vary. Keep it civil, and stay on topic. If you see an inappropriate comment, please use the ‘flag’ feature. Comments are the opinions of the comment writer, not of Castanet. Comments remain open for one day after a story is published and are closed on weekends. Visit Castanet’s Forums to start or join a discussion about this story.



More Skywatching articles

168751
About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



170287
The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

Previous Stories



172253