The Sun Youra Taroyan

Age 4.5 ×10 9 years Mean diameter 1.392×10 6 km, 109 × Earth Mass ×10 30 kg, 333,000 × Earth Volume 1.412×10 18 km 3, 1,300,000 × Earth

Motivation 1. Understanding how the Sun affects the Earth and the near space environment (Space weather) 2. The Sun as a star 3. Natural plasma laboratory

The H-R diagram Stars fall into concentrated groups in the H-R diagram Each concentration defines a particular class Why white dwarfs or red giants?

Unlike any other star, we can observe the Sun in detail The atmosphere of the Sun viewed by the SDO spacecraft in various channels which cover temperatures from 5000K to 15MK. All of these structures are moving

Plasmas 99% of the known universe is in plasma state

Looking inside the Sun “The singing Sun” In the 1960s it was suggested that sound waves could travel around the inside of the Sun, being reflected at the surface and refracted by the changing density and temperature inside the Sun These waves can interfere to produce standing waves in the Sun, moving areas of the surface in and out – and this produces small (but measurable!) Doppler-shifts in the wavelengths of the Sun's light All modes1 mode3 modes

Solar material is hot and structured into different layers with different properties. The Sun contains a layer which acts as a dynamo, generating a strong magnetic field

Sun doesn't rotate as one mass Breakdown in rigid rotation near base of convection zone (tachocline)‏ Different variation in rotation rate with depth at different latitudes Bands of high- and low-speed flow at different latitudes and depths in the Sun These bands move over time

Galileo’s drawings of sunspots

The 11-year solar cycle

Increasing temperature Sun shows more structure (more complexity) at higher temperatures Sun isn't as simple as it looks in white-light images

Chromosphere - the "coloured sphere" Seen during total eclipse (or in H-  line)‏ Thin layer ~ 2000 km deep Temperature ~ 6000 K at base, increases with height to K Low density Glows red (Hydrogen-  emission)‏ Chromosphere is hotter than Photosphere - how? Probably heated by sound waves from photosphere

Filaments and Prominences Two names for the same thing On the disc of the Sun: Dark channels – Filaments Relatively cool, dense gas suspended above the chromosphere Off the limb of the Sun: See the loop of material against the sky Bright suspended Prominences May erupt!

Fine-scale structures above the solar limb – Hinode imager

XIX century drawings of a solar eclipse

The Solar Corona

Coronal heating problem

Coronal Loops

Solar minimum and maximum