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Lecture

Chapter 16.docx


Department
Geophysics
Course Code
GOPH 375
Professor
All

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Chapter 16
Extraterrestrial Causes
“Space weather” changing environmental conditions in space due to varying solar activity.
Organizations like CSWFC forecast geomagnetic activity in polar cap/auroral/sub-auroral zones
Solar wind: stream of subatomic particles from the sun. Hot fringes released can’t be restrained
by gravity and are sent in all directions. Strong gusts caused by coronal holes (localized, fast
plasma) and coronal mass ejections (star-scale, clouds of plasma released in sunspots)
Figure 16.3 sunspot cycle number of sunspots. telluric currents in surface of Earth
o Telluric electrical current propagating in the Earth or through the sea
Electromagnetic induction: magnetic field variations induce electrical currents in a medium, and
induced currents generate their own magnetic field. Always currents flowing through rocks
Magnetic Storms: electric currents are produced in the ionosphere in response to solar wind
disturbances, causing geomagnetic variations. Lasts 24-48 hours, electric currents are called
telluric currents are induced on earth’s surface and conducted/affect power, telephone and
pipelines. Common near the peak and decline of the sunspot cycle
Engineering pipelines know example caused by galvanic erosion. Design your pipeline so the
current flows the other way, so your pipeline doesn’t erode. Common to impress a constant
negative voltage on pipelines to prevent corrosion from telluric currents. Reduce power on
transmission lines when a magnetic storm warning is in effect
o 1989 Hydro-Quebec Power Blackout: coronal mass ejection particles triggered a
magnetic storm through power transmission lines and hydroelectric dams.
Space weather effects on technological systems: failures caused by bombardment of charged
particles, disturbances of the ionosphere, and electromagnetic induction effects
Solar winds travel at 500 m/s in ionosphere and cause damage to circuits, satellites, radio
(communication) transmissions . GPS rarely affected because they’re at a higher frequency
Geomagnetic activity and technical problems first discovered with the telegraph
Impact Scars aka astroblemes made by collision from space debris
o Moon used to be bombarded a lot, now little activity. Maria flood basalts poured on
the moon. Impact scars still evident on the moon because it is geologically dead (no life),
o Earth is dynamic, most impact scars are hidden by tectonic/glacier movements, erosion,
buried by sediment, sea, or flood basalt
Solar system formation 4.571 Billion years ago
Extraterrestrial debris
Asteroids rocky bodies left over between mars and Jupiter. Their average impact velocity is
approx 20 km/sec. Icy masses found in between 4 inner and 4 outer planets (asteroid belt) orbit
the sun
o 3 largest: Ceres, Pallas, Vesta Asteroids can have moons
o Pull of Jupiter stops asteroids from forming a planet
o Gaps within asteroid belt align with orbit time of Jupiter. If an asteroid is knocked into
the gap, it’ll likely hit a planet
o Some asteroids are solids, some are 2+ similar sized bodies bound together by
gravitational attraction. Less energy needed to break an asteroid than to scatter its
fragments, so an asteroid could be broken but pieces would remain together in a rubble
pile
o 3 groups of asteroids have orbits that intercept that of earth/mars and thus, collide
often: Apollo, Aten, and Amor
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