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Chapter 16: Problem 56

Search the World Wide Web for information about features in the solar atmosphere called sigmoids. What are they? What causes them? How might they provide a way to predict coronal mass ejections?

Short Answer

Expert verified
Sigmoids are 'S' or inverse 'S' shaped structures in the solar atmosphere, caused by the restructuring of complex magnetic fields typically above active regions. They play an important role in predicting Coronal Mass Ejections (CMEs) as their existence can indicate regions of magnetic instability where CMEs are likely to occur.

Step by step solution

01

Understanding Sigmoids

Sigmoids are specific structures observed in the solar atmosphere, typically in the corona, the outermost part of the solar atmosphere. These structures are characterized by their unique 'S' or 'inverse S' shape. They can range in length from tens to hundreds of thousands of kilometers.
02

Causes of Sigmoids

Sigmoids are particularly associated with solar phenomena known as active regions. These are areas of the Sun where the magnetic field is significantly strong and complex. The formation of the sigmoid structure results from the interplay and restructuring of such complex magnetic fields typically above active regions. Sigmoids often provide an indication of the areas where magnetic reconnection, a fundamental process in the solar atmosphere which releases stored magnetic energy, is about to or is already occurring.
03

Predicting Coronal Mass Ejections

Coronal Mass Ejections or CMEs are vast outflows of magnetic field and plasma emitted from the Sun's corona. These massive eruptions can significantly disturb the interplanetary medium and lead to geomagnetic storm creation at Earth. Sigmoids are crucial in predicting these CMEs. In many instances, these S-shaped structures are observed to erupt as CMEs, or if already present, they can provide sites where CMEs are likely to occur due to magnetic instability. The transformation of a sigmoid to an arcade of loops is often an indicator of an ongoing or already occurred CME. Therefore, monitoring sigmoids can significantly aid in predicting CME events.

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Most popular questions from this chapter

The moving images on a television set that uses a tube (as opposed to a LCD or plasma flat-screen TV) are made by a fastmoving electron beam that sweeps over the back of the screen. Explain why placing a strong magnet next to the screen distorts the picture. (Caution: Don't try this with your television! You can do permanent damage to your set.)

Describe the dangers in attempting to observe the Sun. How have astronomers learned to circumvent these observational problems?

(a) If the Sun were not in a state of hydrostatic equilibrium, would its diameter remain the same? Explain your reasoning. (b) If the Sun were not in a state of thermal equilibrium, would its luminosity remain the same? What about its surface temperature? Explain your reasoning.

Why should solar flares and coronal mass ejections be a concern for businesses that use telecommunication satellites?

What is Kelvin-Helmholtz contraction? Why is it ruled out as a source of the present-day Sun's energy?
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