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Sun: General Properties

Sun: General Properties. The Sun. 0. General Properties. Spectral type G2V. Age: ~ 4.52 Gyr. Absolute visual magnitude M V = 4.83. Absolute bolometric magnitude M bol = 4.76. Initial abundances:. X = 0.73, Y = 0.25, Z = 0.02. Central temperature = 15 million 0 K.

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Sun: General Properties

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  1. Sun: General Properties www.assignmentpoint.com

  2. The Sun 0 General Properties • Spectral type G2V • Age: ~ 4.52 Gyr • Absolute visual magnitude MV = 4.83 • Absolute bolometric magnitude Mbol = 4.76 • Initial abundances: X = 0.73, Y = 0.25, Z = 0.02 • Central temperature = 15 million 0K • Effective (surface) temperature = 5770 0K www.assignmentpoint.com

  3. 0 The Sun’s Interior Structure Photosphere Energy transport via convection Flow of energy Energy transport via radiation Energy generation via nuclear fusion Temp, density and pressure decr. outward www.assignmentpoint.com

  4. 0 Interior Structure of the Sun Site of main energy production dL/dr 0.1 0.2 0.3 0.4 0.5 r/R0 www.assignmentpoint.com

  5. 0 Interior Structure of the Sun Mass composition 11H 0.8 Mass fraction 0.7 0.6 0.5 0.4 42He 0.3 0.2 0.1 32He (x100) 0.1 0.2 0.3 0.4 0.5 0.6 r/R0 www.assignmentpoint.com

  6. 0 The Sun’s Atmosphere Only visible during solar eclipses Apparent surface of the sun Heat Flow Temp. incr. inward Solar interior www.assignmentpoint.com

  7. 0 Granulation … is the visible consequence of convection www.assignmentpoint.com

  8. Sun Spots (I) 0 www.assignmentpoint.com

  9. Sun Spots (II) 0 Active Regions Visible Ultraviolet Cooler regionsof the photosphere (T ≈ 4000 K). www.assignmentpoint.com

  10. 0 Solar Activity, seen in soft X-rays www.assignmentpoint.com

  11. 0 Magnetic Fields in Sun Spots Magnetic fields on the photosphere can be measured through the Zeeman effect → Sun Spots are related to magnetic activity on the photosphere www.assignmentpoint.com

  12. 0 Sun Spots (III) Magnetic North Poles Magnetic South Poles Related to magnetic activity. Magnetic field in sun spots is about 1000 times stronger than average. www.assignmentpoint.com In sun spots, magnetic field lines emerge out of the photosphere.

  13. 0 Magnetic Loops Magnetic field lines www.assignmentpoint.com Mass ejection from the sun often follow magnetic field loops.

  14. 0 The Solar Cycle 11-year cycle Reversal of magnetic polarity After 11 years, North/South order of leading/trailing sun spots is reversed => Total solar cycle = 22 years www.assignmentpoint.com

  15. 0 The Sun’s Magnetic Cycle After 11 years, the magnetic field pattern becomes so complex that the field structure is re-arranged. → New magnetic field structure is similar to the original one, but reversed! → New 11-year cycle starts with reversed magnetic-field orientation www.assignmentpoint.com

  16. 0 The Solar Cycle (II) Maunder Butterfly Diagram Sun spot cycle starts out with spots at higher latitudes on the sun Evolve to lower latitudes (towards the equator) throughout the cycle. www.assignmentpoint.com

  17. 0 The Maunder Minimum The sun spot number also fluctuates on much longer time scales: Historical data indicate a very quiet phase of the sun, ~ 1650 – 1700: The Maunder Minimum www.assignmentpoint.com

  18. 0 Prominences Looped Prominences: gas ejected from the sun’s photosphere, flowing along magnetic loops www.assignmentpoint.com

  19. 0 Eruptive Prominences Extreme events, called coronal mass ejections (CMEs)and solar flares, can significantly influence Earth’s magnetic field structure and cause northern lights (aurora borealis). www.assignmentpoint.com (Ultraviolet images)

  20. 0 Eruptive Prominences (Ultraviolet images) www.assignmentpoint.com

  21. 0 ~ 5 minutes Solar Aurora Sound waves produced by a solar flare Coronal mass ejections www.assignmentpoint.com

  22. 0 The Chromosphere Region of sun’s atmosphere just above the photosphere. Chromospheric structures visible in Ha emission Absorption and emission lines from singly ionized metals (He II, Fe II, Si II, Cr II, Ca II) T: 4400 K → 25,000 K n: 1011 cm-3 → 107 cm-3 www.assignmentpoint.com

  23. 0 The Chromosphere (II) Spicules = filaments of hot gas, visible in Ha emission. Streams extend up to ~ 10,000 km above photosphere www.assignmentpoint.com

  24. 0 The Transition Zone Transition from moderate to high ionization h ~ 2300 – 2600 km above photosphere T ~ 25,000 → 106 K n ~ 107→ 105 cm-3 Observe selective heights in (UV) emission lines of ionized metals Ly a→ ~ 20,000 K O VI 1032 → ~ 300,000 K CIII 977 → ~ 90,000 K Mg X 625 → ~ 1,400,000 K www.assignmentpoint.com

  25. The Solar Corona 0 www.assignmentpoint.com Very hot (T ≥ 106 K), low-density (n ≤ 105 cm-3) gas

  26. 0 Active vs. Quiescent Corona Near Solar Maximum www.assignmentpoint.com Near Solar Minimum

  27. 0 Coronal Holes X-ray images of the sun reveal coronal holes. These arise at the foot points of open field lines and are the origin of the solar wind. www.assignmentpoint.com

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