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MT4510 Solar Theory Thomas Neukirch. Sun Facts 1 400 kg/m 3 1/4 x Earth’s density 5 500 kg/m 3 Density 2 x 10 30 kg 333 000 x Earth’s mass 6 x 10 24 kg.

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Presentation on theme: "MT4510 Solar Theory Thomas Neukirch. Sun Facts 1 400 kg/m 3 1/4 x Earth’s density 5 500 kg/m 3 Density 2 x 10 30 kg 333 000 x Earth’s mass 6 x 10 24 kg."— Presentation transcript:

1 MT4510 Solar Theory Thomas Neukirch

2 Sun Facts kg/m 3 1/4 x Earth’s density kg/m 3 Density 2 x kg x Earth’s mass 6 x kg Mass 1.41 x km x Earth’s volume 1.1 x km 3 Volume km 109 x Earth’s radius km Radius SunEarth

3 Sun Facts 4 x W 4 x light bulbs Luminosity km x Earth’s radius Distance from Earth 25 days - equator 33 days - poles ‘differential rotation’ 1 day Rotation rate Electrically charged gas core: hydrogen Solid core: iron Consistency SunEarth

4 Sun’s Nuclear Core Fusion of hydrogen in core produces gamma rays

5 Solar Interior Core Radiative Zone Convection Zone Photosphere (surface)

6 Helioseimology Used to study the interior of the Sun It is the study of resonant wave modes of oscillation of the Sun Modes of oscillation are visible manifestations of trapped standing sound waves Strongest periods ~ 5 mins Strongest periods ~ 5 mins

7 Solar Rotation Rate Relative rotation rates of material in the Sun - determined using helioseismology Red material – fastest Dark blue – slowest Interior: red moves ~ 4% faster than outer layers. Surface: red (equator) moves ~ 3,000 mph faster than blue (poles).

8 Solar Atmosphere Photosphere Chromosphere Corona

9 Observing Sun’s Atmosphere

10 Photosphere T ~ K ρ ~ th of water P ~ th of atmosphere H ~ 100 km Visible light images reveal sunspots Magnetograms reveal surface magnetic fields Field into Sun – black Field out of Sun - white

11 Chromosphere 4300 K < T < 10 6 K ρ ~ less than water P ~ not much! H ~ 2500 km Observed in many wavelengths, e.g., Ca II K (393.3 nm) H alpha (656.3 nm)

12 Corona T > 10 6 K (low corona) ρ < less than water P ~ even less! H - to Earth & beyond! Observed in EUV (T~10 6 K) Soft X-ray (T> 2x10 6 K) White light

13 Corona Coronal hole X-ray bright point Active region Coronal loops

14 Coronal Heating Problem

15 Solar Maximum Solar Minimum Solar Cycle

16 Umbra Penumbra Sunspots Magnetic field strength ~ 2-3x10 3 G Umbra – (almost) vertical field Penumbra – (more) horizontal field Number of sunspots varies over 11 year cycle

17 Magnetic field responsible for solar activity ! Sunspots = strong magnetic field Emission in all wavelengths correlates well with strong magnetic field regions Magnetic field dominates solar atmosphere (magnetic energy density >> pressure)

18 Prominences Situated in corona Cool, dense plasma confined in vertical sheets Lifetimes: days-months Size: 2x10 5 x 5x10 4 x 6x10 3 km 3 (LxHxW) ρ : kg cm -3 T: 5-10 x10 3 K

19 Solar Flares Sudden, impulsive, intense, large-scale, heating events Very energetic: from J Lifetimes: hours

20 Coronal Mass Ejections (CMEs) Very large events that eject mass from the Sun Very large events that eject mass from the Sun Energy: J Energy: J Mass: kg Mass: kg Lifetime: hours Lifetime: hours Usually related to a prominence eruption Usually related to a prominence eruption

21 Solar Wind Ions and electrons continually stream out along magnetic field lines Ions and electrons continually stream out along magnetic field lines Solar wind: Solar wind: –Strong above poles (open field) –Weak about equator (closed field)

22 Sun-Earth Connection Solar wind continually buffets Earth’s magnetic field CME’s can distort Earth’s magnetic field and cause Auroras

23 The Sun on 10 Feb 2008 EIT 304EIT 171EIT 195EIT 284 LASCO C3 LASCO C2MDI MAGMDI CONT

24 Solar Theory Course §TopicImportance 1 Maxwell’s equations and magnetic fields Outline structure of events 2 MHD equations Describe behaviour of Sun 3 Magnetic reconnection and magnetic energy Flares, CMEs, coronal heating, solar wind 4 MHD equilibria Coronal arcades and loop structures, prominences 5 MHD waves Helio/coronal-seismology, coronal heating, solar wind 6 Solar wind Sun/Earth connection

25 The Sun (Summary)


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