lect 8 - 22-year Solar cycle Sun’s magnetic field...

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Unformatted text preview: 22-year Solar cycle: Sun’s magnetic field reverses polarity every 11 yearsSunspot group moving: the sunspots in front are called the “preceding members”All preceding members on a given hemisphere have the same polarity, and opposite to the preceding members on the other hemisphereThe magnetic-dynamo modelsuggests that many features of the solar cycle are due to changes in the Sun’s magnetic fieldThe solar magnetic changes are caused by convectionand the Sun’s differential rotationRotation of the Solar InteriorDifferential rotation persist through the convection zone.In the radiative zonethe Sun rotates as a rigidBody (27 days)Magnetic field may originate between the Radiative and convective ZoneHelioseismology: rotation rate in the Sun’s interior is determined by comparing the speeds of sound waves in the interiorSolar cycle is not alwaysregular…• Reversal of magnetic field: one pole could go earlier than the other (example, two north poles may be present!)• Sunspot cycles may- vanish for years: No sunspots were observed from 1645 to 1715, record low temperatures in Europe, and severe drought in western United States.- increase activity: during 11-12 centuries, climate was warmer than today.Then, variations in solar activity appear to affect climate on EarthThe active SunChromosphereseen through an HαfilterThe Sunseen through an UV filterThe Sun’s magnetic field also produces otherforms of solar activity • A solar flare is a brief eruption of hot, ionized gases from a sunspot group• A coronal mass ejection is a much larger eruption that involves immense amounts of gas from the coronaCoronal mass ejectionsThe Nature of the Stars...
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This note was uploaded on 02/06/2011 for the course ASTR 113 taught by Professor Geller during the Spring '08 term at George Mason.

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lect 8 - 22-year Solar cycle Sun’s magnetic field...

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