The Solar Cycle for seeing the sun exhibit

The Solar Cyclefor seeing the sun exhibit

The Sun’s Magnetic Field The magnetic field on the sun is produced by the flow of electrically charged ions and electrons. The changing magnetic field of the sun governs many aspects of solar activity.

The Solar Cycle • Magnetic flux rises up to the sun's surface, causing solar activity such as sunspots and solar flares • Every 11 years, activity rises to a maximum, then falls to a minimum • The cycle is usually defined by the number of sunspots present

Solar Cycle Chart Peaks represent solar maximum when the most sunspots are present

The Solar Cycle • Solar minimum- • Time of lowest solar activity • Rare to see any sunspots on the sun • Solar maximum- • Peak in solar activity • Sunspots visible almost all of the time • Can have more than 100 sunspots and some as big a 50,000km in diameter Sun at Solar Minimum Sun at Solar Maximum

Solar Maximum More solar activity means increased sunspots Because. . .

Sunspots Flares and prominences are correlated with sunspots because broken magnetic field lines help gas escape from the sun's surface. The sun rotates faster at the equator than at the poles causing magnetic field lines to become twisted around the sun.

Sunspots • Convection serves to distort the field lines even more. • The lines become so skewed that they break through the sun’s surface, resulting in sunspots.

Solar Maximum More solar activity involves more flares too

Solar Flares On the Sun's surface are huge magnetic loops called prominences. When they touch, they short circuit each other, setting off huge explosions or solar flares.

Solar Flares • Solar flares occur on the sun’s surface. • They are found on lines dividing areas of oppositely charged magnetic fields.

Solar Maximum More solar activity also means increased coronal mass ejections

Coronal Mass Ejections Coronal mass ejections (CMEs) are huge bubbles of gas threaded with magnetic field lines, ejected from the sun over several hours.

Solar Maximum More solar activity also means changes in the sun’s magnetic field

Sun’s Magnetic Field • The sun’s magnetic field not only causes much of the solar activity during solar maximum, but also changes with the sunspot cycle. • Every 11 years the sun’s magnetic field reverses direction. Therefore the true solar cycle is 22 years. + - - +

Sun’s Magnetic Field • Because the sun rotates at different speeds the magnetic field of the sun gets twisted and warped like a rubber band. • Observations from the Ulysses spacecraft show that during reversal, the Sun's magnetic poles are located near the solar equator instead of the polar caps

Sun’s Magnetic Field Twisted magnetic field lines Magnetic poles shift to equator

Sun’s Magnetic Field • When the sun’s magnetic field reverses, the twisted field lines are gradually straightened out again, thanks to the different rotational rates of the sun’s surface.

Sun’s Magnetic Field • Coronal mass ejections also help the sun reverse its magnetic field • Blast billions of tons of electrified gas into space • Sweep away untidy magnetic fields created by sunspots • Allow a new field to form with flipped orientation

The Solar Cycle • The solar cycle and the sun’s activity have become very important to understand as solar activity can send bursts of radiation towards the Earth • Extra radiation affects satellites, astronauts in space, cell phones, television and radio signals, and other technology we use everyday • Scientists hope to someday better predict solar activity and prevent technology from being affected by it

The Solar Cycle Additional In-Depth Information:

In-Depth: Evidence of Twisting Magnetic Field Lines In its simplest form, an active region exhibits the magnetic pattern of a bar magnet hidden beneath the photosphere. Under the light of a strong spectral line, the gaseous surface shows elongated features, called fibrils, which line up with the magnetic field. Sunspots mark the positions of the poles of the magnet. Such simple active regions, however, rarely produce flares and coronal mass ejections. An explosive energy release requires free energy. The magnetic field lines have to be 'wound up' like a twisted rubber band. In energetic active regions, this phenomenon can be seen directly: the fibrils radiating from sunspots assume a spiral 'whirligig' pattern. The loops and arches in soft X-ray images of active regions, which may be the coronal equivalent of iron filings, also shows evidence of twist.

In-Depth: Twisted Magnetic Field and Sunspots Sunspot formation is governed by the sun’s magnetic field and differential rotation, combined with its gaseous nature. The magnetic field lines of the sun run from pole to pole beneath the surface. Because the sun rotates faster at the equator than at the poles (25 days versus 35 days), the field lines become twisted around the sun (fig. 4). Convection serves to distort the field lines even more, until they become so skewed that they break through the photosphere, resulting in sunspots. Sunspots appear dark because they are cooler than the photosphere around them, as the intense magnetic fields from which they arise do not allow the effective transfer of heat. *When the polarity of the sun’s magnetic field reverses during sunspot maximum, the twisted field lines are gradually straightened out again, thanks to the different rotational rates of the sun’s surface. This cycle of the twisting and untwisting of the magnetic field lines occurs within every sunspot cycle.

In-Depth: Magnetic Fields of the Sun Reversing of magnetic fields apparent by yellow and blue zones at the poles (blue and yellow mixed at equator during reversal) Blue = minus = south Yellow = plus = north

More Info on the Solar Cycle • Good information dealing with every aspect of the sun: http://science.nasa.gov/ssl/pad/solar/default.htm • News article about magnetic reversal: http://news-service.stanford.edu/news/june12/solarmagnet-612.html • News article about the solar cycle: http://www.firstscience.com/site/articles/sun.asp

The Solar Cycle for seeing the sun exhibit