Chapter 28 The Sun Section 2 Solar Activity Notes 28-2

Bell Ringer Name and briefly describe the six layers of the sun. 1. Core 2. Radiative zone 3. Convective zone 4. Photosphere 5. Chromosphere 6. Corona

Sun Facts ► The gases making up the sun are always moving  The energy produced in the core cause the gases to rise and fall in a cycle. ► Warm rises and cool falls  Different parts are moving at faster rates than other parts ► Because the sun rotates on its axis ► Gases near the equator move faster than the gases at the poles ► On average the sun’s rotational rate is 27 earth days

Sunspots ► The movement of the gases causes magnetic fields  Causes convection to slow down in the convective zone ► Less heat is transferred to the photosphere ► Areas of the photosphere near magnetic fields are much cooler than surrounding areas  3,000 °C cooler

Sunspots ► Cooler areas appear darker  These are called sunspots ► Can be more than 100,000 km in diameter  Several times the size of earth ► After close observation of the sun, astronomers have found  Sunspots start between the equator and poles of the sun

Sunspots ► After they disappear from the region between the equator and poles, new ones show up on the equator ► Sunspot cycle is an 11 year cycle  Begins when sunspots increase in number  More and more occur until the number peaks ► May be able to see 100 or more sunspots  Then the number decreases again

Prominences and Solar Flares ► Magnetic fields also cause other disturbances ► Prominences: great glowing arches of burning gases  Follow the curved lines of magnetic forces from one sunspot to another  Can last several weeks to a year

Prominences and Solar Flares ► Solar flare: most violent of all solar disturbances  Sudden outward eruption of electrically charged atomic particles  Can cover thousands of km in a few minutes  Usually don’t last up to an hour  Occur near sunspots  At the peak of the sunspot cycle, 5 to 10 solar flares can be seen a day

Prominences and Solar Flares ► Charged atomic particles from solar flares are flung into space  They increase the strength of the solar wind ► These particles bombard earth and cause disturbances in the earth’s magnetic field  Called magnetic storms  There is less than one severe storm a year ► Can interfere with radio and other types of communications on the earth

Aurora

Auroras ► Called northern and southern lights ► Caused by magnetic storms  Charged particles are funneled to the poles by the magnetosphere  Usually only seen at the poles ► Charged particles hit gas molecules in the upper atmosphere and produce green, red, blue or violet lights

Auroras ► Occur between 100 and 1000 km above the surface ► Most frequent after a peak in the sunspot cycle and after solar flares ► Can be seen in the northern US about 5 times a year ► Sometimes they are bright and strong enough to be seen at the equator  1921, South Pacific islands