EARTH & SPACE EARTH & SPACE SCIENCESCIENCE

Chapter 29 The SunChapter 29 The Sun

29.2 Solar Activity29.2 Solar Activity

29.2 Solar Activity Objectives29.2 Solar Activity Objectives

Explain how sunspots are related to Explain how sunspots are related to powerful magnetic fields on the sun.powerful magnetic fields on the sun.

Compare prominences, solar flares, and Compare prominences, solar flares, and coronal mass ejections.coronal mass ejections.

Describe how the solar wind can cause Describe how the solar wind can cause auroras on Earth.auroras on Earth.

IntroductionIntroduction

The gases that make up the sun’s interior The gases that make up the sun’s interior and atmosphere are in constant motion.and atmosphere are in constant motion.

The sun also rotates on its axis.The sun also rotates on its axis.Places close to the equator on the sun’s Places close to the equator on the sun’s

surface take 25.3 Earth days to rotate surface take 25.3 Earth days to rotate once.once.

Places near the poles of the sun take 33 Places near the poles of the sun take 33 Earth days to rotate once.Earth days to rotate once.

SunspotsSunspots A sunspot is a dark area of the photosphere A sunspot is a dark area of the photosphere

of the sun that is cooler than the surrounding of the sun that is cooler than the surrounding areas and that has a strong magnetic field.areas and that has a strong magnetic field.

The movements of gases within the sun’s The movements of gases within the sun’s convective zone and the movements caused convective zone and the movements caused by the sun’s rotation produce magnetic fields. by the sun’s rotation produce magnetic fields.

These magnetic fields cause convection to These magnetic fields cause convection to slow in parts of the convective zone.slow in parts of the convective zone.

SunspotsSunspots

Slower convection causes a decrease in the Slower convection causes a decrease in the amount of gas that is transferring energy from amount of gas that is transferring energy from the core of the sun to these regions of the the core of the sun to these regions of the photosphere. photosphere.

Because less energy is being transferred, Because less energy is being transferred, these regions of the photosphere are these regions of the photosphere are considerably cooler than surrounding regions, considerably cooler than surrounding regions, and form areas of the sun that appear darker and form areas of the sun that appear darker than their surrounding regions.than their surrounding regions.

These, cooler, darker areas are called These, cooler, darker areas are called sunspots.sunspots.

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question17.html

http://sohowww.nascom.nasa.gov/gallery/posters.html

The Sunspot CycleThe Sunspot Cycle Observations of sunspots have shown that Observations of sunspots have shown that

the sun rotates. the sun rotates. The numbers and positions of sunspots vary The numbers and positions of sunspots vary

in a cycle that lasts about 11 years.in a cycle that lasts about 11 years. Sunspots initially appear in groups about Sunspots initially appear in groups about

midway between the sun’s equator and poles. midway between the sun’s equator and poles. The number of sunspots increases over the The number of sunspots increases over the

next few years until it reaches a peak of 100 next few years until it reaches a peak of 100 of more sunspots. of more sunspots.

After the peak, the number of sunspots begins After the peak, the number of sunspots begins to decrease until it reaches a minimum.to decrease until it reaches a minimum.

Sunspots Video LinksSunspots Video Links Powerful sun / our Solar System / 11 year Powerful sun / our Solar System / 11 year

Sunspot cycle 22 year Solar cycle / Solar cycle Sunspot cycle 22 year Solar cycle / Solar cycle 24 (3:26) - 24 (3:26) - http://youtu.be/ei7MBRaoVu4http://youtu.be/ei7MBRaoVu4

The Solar Cycle* *(Same as above link, but The Solar Cycle* *(Same as above link, but more clear) (3:26) - more clear) (3:26) - http://youtu.be/AcAoHXOrqL8http://youtu.be/AcAoHXOrqL8

NASA - Solar activity by SOHO space capsule NASA - Solar activity by SOHO space capsule (5:50) - (5:50) - http://youtu.be/Y012FYE8G3khttp://youtu.be/Y012FYE8G3k

Solar EjectionsSolar Ejections

Other solar activities are affected by the Other solar activities are affected by the sunspot cycle, such as the solar-activity sunspot cycle, such as the solar-activity cycle.cycle.

The solar-activity cycle is caused by the The solar-activity cycle is caused by the changing solar magnetic field. changing solar magnetic field.

This cycle is characterized by increases This cycle is characterized by increases and decreases in various types of solar and decreases in various types of solar activity, including solar ejections. activity, including solar ejections.

Solar ejections are events in which the sun Solar ejections are events in which the sun emits atomic particles.emits atomic particles.

Solar EjectionsSolar Ejections

A prominence is a loop of relatively cool, A prominence is a loop of relatively cool, incandescent gas that extends above the incandescent gas that extends above the photosphere.photosphere.

Solar ejections include prominences, solar Solar ejections include prominences, solar flares, and coronal mass ejections.flares, and coronal mass ejections.

Prominences are huge arches of glowing Prominences are huge arches of glowing gases that follow the curved lines of the gases that follow the curved lines of the magnetic force from a region of one magnetic force from a region of one magnetic force to a region of the opposite magnetic force to a region of the opposite magnetic polarity.magnetic polarity.

Solar Ejections Video LinksSolar Ejections Video Links

NASA - Magnificent Eruption in Full HD NASA - Magnificent Eruption in Full HD 1080p (2:11) - http://youtu.be/orqeYbqSiLg1080p (2:11) - http://youtu.be/orqeYbqSiLg

A prominence eruption observed by AIA A prominence eruption observed by AIA (:10) - http://youtu.be/Lmm3J0WAres(:10) - http://youtu.be/Lmm3J0WAres

Extreme Solar Flares (2:53) - Extreme Solar Flares (2:53) - http://youtu.be/nmDZhQAIeXMhttp://youtu.be/nmDZhQAIeXM

NASA SDO - Summer Solstice Coronal NASA SDO - Summer Solstice Coronal Mass Ejection (0:35) - Mass Ejection (0:35) - http://youtu.be/rqtOUqwQVFYhttp://youtu.be/rqtOUqwQVFY

Solar EjectionsSolar Ejections

A solar flare is an explosive release of energy A solar flare is an explosive release of energy that comes from the sun and that is associated that comes from the sun and that is associated with magnetic disturbances on the sun’s with magnetic disturbances on the sun’s surfacesurface

Solar flares are the most violent of all solar Solar flares are the most violent of all solar disturbances.disturbances.

Solar flares release the energy stored in the Solar flares release the energy stored in the strong magnetic fields of sunspots. This strong magnetic fields of sunspots. This release can lead to the formation of coronal release can lead to the formation of coronal loops.loops.

Solar EjectionsSolar Ejections A coronal mass ejection is a part of coronal A coronal mass ejection is a part of coronal

gas that is thrown into space from the sun.gas that is thrown into space from the sun. Some of the particles from a solar flare escape Some of the particles from a solar flare escape

into space, increasing the strength of the solar into space, increasing the strength of the solar wind.wind.

Particles also escape as coronal mass Particles also escape as coronal mass ejections. ejections.

The particles in the ejection can cause The particles in the ejection can cause disturbances to Earth’s magnetic field.disturbances to Earth’s magnetic field.

These disturbances have been known to These disturbances have been known to interfere with radio communications, satellites, interfere with radio communications, satellites, and even cause blackouts.and even cause blackouts.

http://www.nasa.gov/mission_pages/rbsp/science/rbsp-spaceweather.html

http://www.flickr.com/photos/lightsinthedark/5821379923/

Solar Prominence Captured by NASA’s Solar Dynamics Observatory

http://sec.gsfc.nasa.gov/Roadmap_graphics.htm

Coronal Mass Ejection

http://www.nasa.gov/mission_pages/sunearth/news/News041612-M1.7flare.html

AurorasAuroras

An aurora is a colored light produced by charged An aurora is a colored light produced by charged particles from the solar wind and from the particles from the solar wind and from the magnetosphere that react with and excite the magnetosphere that react with and excite the oxygen and nitrogen of Earth’s upper atmosphere; oxygen and nitrogen of Earth’s upper atmosphere; usually seen in the sky near Earth’s magnetic usually seen in the sky near Earth’s magnetic poles.poles.

Auroras are the result of the interaction between Auroras are the result of the interaction between the solar wind and Earth’s magnetosphere.the solar wind and Earth’s magnetosphere.

Auroras are usually seen close to Earth’s Auroras are usually seen close to Earth’s magnetic poles because electrically charged magnetic poles because electrically charged particles are guided toward earth’s magnetic poles particles are guided toward earth’s magnetic poles by Earth’s magnetosphere.by Earth’s magnetosphere.

http://www.geo.mtu.edu/weather/aurora/images/aurora/jan.curtis/

Auroras Video LinksAuroras Video Links

NASA | The Mystery of the Aurora (2:15) - NASA | The Mystery of the Aurora (2:15) - http://youtu.be/PaSFAbATPvkhttp://youtu.be/PaSFAbATPvk

NASA. Aurora Borealis over Canada NASA. Aurora Borealis over Canada (1:02) - http://youtu.be/knInAjlZRec(1:02) - http://youtu.be/knInAjlZRec