Streamers in the Sun's corona during a solar eclipse. In the top image, taken in 1994 near solar min, the streamers are mostly absent from the Sun's poles. In the bottom image, taken near solar max in 1980, streamers sprout from all solar latitudes.
Click on image for full size
Images courtesy of UCAR's High Altitude Observatory and Rhodes College.

The Solar Polar Atmosphere

At certain times in the sunspot cycle, the Sun's atmosphere and the solar wind behave very differently near the Sun's poles as compared to equatorial regions on the Sun.

Scientists call the relatively "quiet" phase of each sunspot cycle "solar min". Around solar min, images of the Sun's upper atmosphere (the corona) show striking differences between the polar corona and the equatorial corona. Images taken during a solar eclipse or by a special instrument called a coronagraph show dense structures called streamers extending outward through the corona at low latitudes. However, near the Sun's poles the streamers are less prominent or absent altogether.

The solar wind, the Sun's "extended atmosphere", also displays distinct polar and equatorial regimes around each solar min. The solar wind emanating from polar regions races away from the Sun at speeds of 700 km/sec (435 miles/second) or faster. The solar wind flowing outward from equatorial regions is much slower, moving about half as quickly as the fast polar wind. The fast solar wind escapes the Sun through coronal holes which form around open magnetic field lines near the poles.

During the active phase of the solar cycle, called "solar max", the number of sunspots increases and the Sun's magnetic field becomes complex and chaotic. Eclipse photos and coronagraphs show streamers bursting forth in a haphazard fashion from all latitudes on the Sun at solar max. Likewise, the Sun's scrambled magnetic field at solar max produces many more fluctuations in solar wind speed with latitude... unlike the clear equatorial vs. polar distinction found at solar min.

Much of our knowledge of the Sun's poles and the high-latitude solar wind was gathered by the Ulysses spacecraft. Ulysses is the only mission so far to "fly over" the poles of the Sun.

Last modified June 11, 2009 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

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

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)....more

The Magnetic Field

The force of magnetism causes material to point along the direction the magnetic force points. This property implies that the force of magnetism has a direction. As shown in the diagram to the left, the...more


Sunspots are dark, planet-sized regions that appear on the "surface" of the Sun. Sunspots are "dark" because they are cooler than their surroundings. A large sunspot might have a central temperature of...more

The Sun's Magnetic Field

The Sun has a very large and very complex magnetic field. The magnetic field at an average place on the Sun is around 1 Gauss, about twice as strong as the average field on the surface of Earth (around...more

Sunspots and Magnetic Fields

Sunspots are caused by extremely strong, localized magnetic fields on the Sun. "Jet streams" of plasma that form deep within the Sun's convective zone produce powerful magnetic fields. When these loops...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