the sun

Question 1

What’s the solar cycle

Answer 1

11 year cycle of the number of sun spots per year. The sun spots have a leading and following magnetic field. the polarity of the leading field (emerging from the surface) is opposite to that of the following field (submerging)

The leading field polarity is opposite in the northern and southern hemispheres. this swaps every cycle so its actually a 22 year cycle

Question 2

whats the corona

Answer 2

the outer atmosphere of the sun. its can be seen during solar eclipses

Question 3

what’s solar wind

Answer 3

a stream of energized charged particles (mostly electrons and protons) it travels at 900 km/s and is 1 million kelvin

Question 4

what’s PP-1

Answer 4

the proton-proton chain one. most of the energy in the sun is produced this way.

1. two protons –> Deuterium nucleus + positron + neutrino
2. Deuterium + proton –> Helium-3 nucleus + gamma photon
3. 2 He-3 nuclei –> Helium-4 nucleus + 2 protons

step 1 takes 10^10 years.
step 2 takes 1 second
step 3 takes 10^6 years

Question 5

what’s the coulomb barrier

Answer 5

the electrostatic repulsion between protons that must be overcome for fusion to occur.

Question 6

what’s a neutrino oscillation

Answer 6

neutrinos have mass so they can change between types (electron-, muon, tau- neutrinos). this results in only seeing 1/3 what is actually emitted from the sun of a given type.

Question 7

what are the origins of planetary atmospheres

Answer 7

1. The primordial solar nebular (that formed the sun). this is where most of the gas giants atmospheres came from
2. Outgassing. Volcanoes emit large amounts of gas. this is where most of earths atmosphere comes from
3. Accretion. asteroids/comets impacting may have brought atmospheric constituents
4. Life. on Earth, photosynthesis produced lots of oxygen

Question 8

what’s the optical depth equation

Answer 8

I = I₀ e^(-T)
I: intensity
T: optical depth (tau symbol)

Question 9

what’s the albedo

Answer 9

the fraction of incident light that is reflected.

Question 10

derive the equilibrium temp

Answer 10

F = L / 4πd² (incident flux)
Fₐ = (1-w) L / 4πd² (absorbed flux, w: albedo)
Lₚ = πR² * Fₐ

πR² * (1-w)L / 4πd² = 4πR²σT⁴
rearrange for T

Question 11

equation of hydrostatic equilibrium

Answer 11

dp/dr = -Gm(r)ρ(r)/r²

Question 12

how do some gasses leak away

Answer 12

Temperature gives a Maxwell-Boltzmann distribution of the velocities of particles. there is a high-energy tail in which the particles have sufficient energy to escape. when they are gone the rest of the particles re-equilibrate so the high energy tail can leak again