Magnetic field lines from a computer simulation of the solar corona show some of the complexity of the Sun's magnetic field. Colors on the Sun's surface show the strength of the magnetic field (yellow is largest).
Click on image for full size

Helmet Streamers and the Magnetic Structure of the Corona

The gas in the solar corona is at very high temperatures (typically 1-2 million kelvins in most regions) so it is almost completely in a plasma state (made up of charged particles, mostly protons and electrons). Strong magnetic fields thread through the corona. Where these magnetic lines of force are closed, the magnetic field is strong enough to trap the solar plasma and keep it from escaping. Plasma accumulates in these regions and forms the beautiful structures call helmet streamers seen during solar eclipses. Prominences are often situated beneath helmet streamers, and active regions occur beneath streamers near the equator (sometimes called active regions streamers). In some regions, the coronal magnetic field cannot confine the plasma, and the plasma expands outward, reaching supersonic velocities. Regions on the Sun with these open magnetic field lines (which stretch far out into the solar system) correspond to coronal holes and are the source of the solar wind, which accelerates outward from the Sun and fills interplanetary space. The electrons in the coronal hole plasma are typically cooler and less dense than streamers, and so they show up as dark regions in both X-rays and white light.

Scientists try to understand the Sun (and other things as well) by developing mathematical models. Frequently the equations that represent the solar plasma are so complicated a computer must be used to solve them. The magnetic field lines on the left image are from a computer simulation that solved the magnetohydrodynamic (MHD) equations, which give a good representation of many types of plasma behavior.

Last modified May 10, 2010 by Randy Russell.

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

The Solar Corona

Rising above the Sun's chromosphere , the temperature jumps sharply from a few tens of thousands of kelvins to as much as a few million kelvins in the Sun's outer atmosphere, the solar corona. Understanding...more

Kelvin Temperature Scale

The Kelvin scale is a temperature scale that is often used in astronomy and space science. You are probably more familiar with the Celsius (or Centigrade) scale, which is part of the metric system of measures,...more

The Plasma State

Plasma is known as the fourth state of matter (the first three states being solid, liquid and gas).Matter in ordinary conditions on Earth has electrons that orbit around the atomic nucleus. The electrons...more

Solar Eclipses

An eclipse of the Sun occurs when the Earth passes through the Moon's shadow. A total eclipse of the Sun takes place only during a new moon, when the Moon is directly between the Sun and the Earth and...more

Last Solar Eclipse of the Millennium on August 11

The last solar eclipse of this millennium occurred on August 11, 1999. Amateurs and professionals alike used this opportunity to witness one of the most brilliant natural phenomenon. This was a total...more

Solar Eclipses Were not Always Enjoyed

Eclipses have been monitored for centuries, but it was only recently that we understood what really occurs. Eclipses have always been fascinating to watch, but they weren't always welcome. For many years,...more

The Photosphere - the "Surface" of the Sun

Most of the energy we receive from the Sun is the visible (white) light emitted from the photosphere. The photosphere is one of the coolest regions of the Sun (6000 K), so only a small fraction (0.1%)...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA