Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Today`s outline
Document related concepts
Transcript
Today’s outline Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Review: Inside the Sun Solar Activity and equilibrium I Magnetic fields and sunspots I Corona I Solar cycle I Solar equilibrium Tutorial on solar equilibrium Stellar Equilibrium Tutorial Solar activity Question concepts Question #1: Label location of the major structures of the sun: core, radiative zone, convection zone, photosphere and corona Question #2: Stars are powered for nearly all of their lives by nuclear fusion of hydrogen to form helium in their centers. The Sun is currently in this core hydrogen fusion stage. Question #3: For fusion to take place, particle motion, such as thermal motion, must overcome the electromagnetic repulsion between nuclei. Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Solar activity Solar Activity and equilibrium Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium I Magnetic fields and sunspots I Corona I Solar cycle I Solar equilibrium Tutorial on solar equilibrium Tutorial Solar Activity X-rays: Solar activity involves regions at the surface and in the corona Due to dynamics of solar magnetic field The local magnetic field structure is constantly changing Interacts with solar material because it is plasma – charged particles are free to move independently Sunspots: Coronal mass ejection Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Magnetic field lines Solar activity Charged particles moving in a magnetic field feel force which changes their paths Motion in same direction as field line induces no force If magnetic field is strong, charged particles ”slide” along magnetic field lines Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Magnetic field and Sunspots Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Large magnetic field ”bundles” arch out of sun’s surface Field lines above surface are observable due to hot plasma ”stuck” to the field lines, but at surface... I Magnetic fields lock gas in place at footpoints I gas cools instead of mixing with surrounding hot gas rising from convection zone I creates sunspots, areas of lower temperature on photosphere Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Question concepts Question #4: Solar activity constitutes changes in the magnetic field structure at the surface and in the corona of the Sun. Stellar Equilibrium Tutorial Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Question concepts Stellar Equilibrium Tutorial Question #5: Sunspots form at the footpoints of magnetic loops protruding from the sun’s surface. The spots are cooler than the surrounding solar surface because they are prevented from mixing by the magnetic field. Solar Flares Solar Flares I Due to sudden rearrangements of magnetic field features I Changes in magnetic field deposit lots of energy in corona I Causes eruptions of high-energy particles I Increases energetic particles observed at Earth (Aurora) I Can disrupt electronics and communication I Big problem for interplanetary human spaceflight (kills astronauts outside Earth’s magnetic field) Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Solar cycle and driving Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Solar magnetic activity driven by non-uniform rotation spin period: 25 days at equator, 34 days at poles I field strengthened by winding I overall field switches polarity about every 11 years I cycle of strength in between I sunspot number and location follow cycle Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Question concepts Stellar Equilibrium Tutorial Question #6: The stretching of magnetic fields by the non-uniform rotation of the sun drives the constant changes in magnetic field structure that manifest as solar activity. Stellar Thermal Equilibrium Most objects: Star: add energy = temperature increases add energy = temperature decreases This makes temperature-driven fusion stable! (i.e. why the sun is not a bomb) Thermal plus gravitational energy is what we call the energy in the star – coupled by hydrostatic equilibrium Adding energy to a star causes it to expand and its central temperature to decrease Somewhat analogous to orbit – higher energy orbits (larger distance) have longer perionds and also lower orbital velocity. As a star loses energy to space it becomes hotter, causing fusion. In a star like the Sun this is in thermal equilibrium (energy input = energy lost) for a long time (billions of years). Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar Equilibrium Tutorial Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Stellar equilibrium tutorial Stellar Equilibrium Tutorial I Discuss with someone sitting near you I Write in each explanation in your own words Solar activity Activity Magnetic field Sunspots Solar Flares Solar Cycle Question concepts Stellar Equilibrium Tutorial Question #7: As the thermal and gravitational energy content of a normal star increases, its central temperature decreases (due to its expansion), and vice versa. This is the opposite of everyday objects.
