Transcript Lecture 17
Lecture 17 Outline For Rest of Semester • • • • • • • • • • • • Oct. 29th Chapter 9 (Earth) Nov 3rd and 5th Chapter 9 and Chapter 10 (Earth and Moon) Nov. 10th and 12th Chapter 11 (Mars, Venus, and Mercury) Nov. 17th and 19th Chapter 12 (Jupiter and Saturn) Nov 24th Chapter 13 (Uranus and Neptune) Nov 26th Thanksgiving Dec. 1st - Exam 3 Dec. 3rd – Chapter 14 (Pluto, and the Kuiper Belt) Dec. 8th and 10th – Chapter 7 and 8 (Comparative Planetology I and II) Tuesday December 15th (7:30 am – 10:15 am) Final Exam No Reading days are scheduled this semester Exam Period begins at 7:30 a.m. on Monday, December 14 and ends on December 21 Outline For Today • • • • Discuss Quiz Finish Atmosphere Earth’s Magnetosphere The Moon – Observations – Formation Theory Protective Shields • Atmosphere • Magnetic field Key Words • solar wind • plasma • magnetosphere • northern and southern lights • Van Allen Radiation belts The Solar Wind Ions and electrons propagating toward Earth (travel time ~ 4 days) Small magnetic field in interplanetary space The Solar Wind • A plasma is created by ionizing atoms • Besides sending out photons, the sun is the source of the solar wind – a plasma traveling at ~ 400 km/s • When the plasma gets near Earth, the charged particles are influenced by Earth’s (internal) magnetic field. • The path a particle takes is complicated – ions and electrons tend to rotate around magnetic field lines – www.spaceweathercenter.org/our_protective_shield/01/minigolf.html The Magnetosphere • Charged particles moving in same direction of magnetic field are not deflected. + Magnetic field direction The Magnetosphere • Charged particles moving perpendicular to magnetic field are deflected (tend to rotate around magnetic field lines) No magnetic field + Region of magnetic field The Magnetosphere • Electrons rotate in opposite direction around field lines. No magnetic field - Region of magnetic field The Magnetosphere • Ions and electrons moving in opposite direction = a current … and a current creates a magnetic field … No magnetic field Region of magnetic field + - Quiz yourself • http://www.spaceweathercenter.org/our_pr otective_shield/01/minigolf.html Far away from Earth, Solar wind distorts dipole magnetic field Formation of the Magnetosphere • http://meted.ucar.edu/hao/aurora/squish.htm The Magnetosphere Van Allen Radiation Belts Van Allen Radiation Belts • Ions and electrons moving bouncing along magnetic field lines • Some charged particles from the solar wind are trapped in two huge, doughnutshaped rings called the Van Allen belts Aurora • Certain solar wind conditions energize electrons and ions in magnetosphere. Some collide with atoms in Earth’s atmosphere. • Collisions of charged particles atoms in atmosphere create aurora Aurora (northern and southern lights) Review Questions • If the Earth did not have a magnetic field, do you think aurorae would be more common or less common than they are today? • What is the solar wind? • From http://www.dslreports.com/forum/remark,16822681 • Uses color saturation http://en.wikipedia.org/wiki/Saturation_(color_theory) Guiding Question How did the Moon form? Key Words • capture theory • co-creation theory • collisional ejection theory • crater • far side (of the Moon) • fission theory • impact crater • • • • mare (plural maria) moonquake synchronous rotation terminator The Moon’s rotation always keeps the same face toward the Earth due to synchronous rotation How did the moon form? • Observations • Theory The maria formed after the surrounding light-colored terrain, so they have not been exposed to meteoritic bombardment for as long and have fewer craters • Virtually all lunar craters were caused by space debris striking the surface • There is no evidence of plate tectonic activity on the Moon • Moonquakes are rare and weak The Moon has no global magnetic field but has a small core beneath a thick mantle Lunar rocks reveal a geologic history quite unlike that of Earth • The anorthositic crust exposed in the highlands was formed between 4.0 and 4.3 billion years ago • The mare basalts solidified between 3.1 and 3.8 billion years ago • The Moon’s surface has undergone very little change over the past 3 billion years Theories How did the moon form? • • • • Fission? Capture? Co-creation? Collision (collisional ejecta theory)?