Section 5. Giant planets Flashcards
(36 cards)
What are the Gas giants?
Jupiter and Saturn
Radius and mass dominated by H + He gas
What are the ice giants?
Neptune and Uranus
Less gas, higher proportions of common ices
What is the equation of state for the giant planets?
P~Kρ2
What is the density equation for the giant planets?
ρ(r)=ρcsin(kr)/kr
Where k=sqrt(2πG/K)
What is the equation for the central density?
ρc=πM/4R3
What is the expected composition of the Gas giants?
Rocky/icy core then metallic hydrogen
Why do the Gas giants have global convection?
Bonding pattern extends into deep interior
Why do the Gas giants have strong magnetic fields?
Convection plus rotation plus conducting interior creates a magnetic dynamo
Why are the Gas giants oblate?
They rotate rapidly (< 0.5 days)
What do the magnetic fields of the Gas giants cause?
Aurorae at poles and radio emission via cyclotron/synchrotron emission by low/high energy electrons orbiting magnetic field lines
Why do the Gas giants have a very large magnetosphere?
Strong magnetic moment and lower solar wind flux
What is the equation for magnetic energy density?
uB=B2/μ0
What is the magnetic field for a dipole?
B(r)=μ0μ/2πr3
What is the K.E. density of the solar wind?
uW=1/2 ρWvW2
How do we find the radius of the magnetosphere?
Equate the magnetic energy density with the kinetic energy density of the solar wind
How does the radius of the magnetosphere scale?
Rm α (μa)1/3
How do the magnetic moments of Neptune and Uranus compare to Earth?
50 and 25 times as large due to ionised cores at extreme pressures
What is the source of internal heat for Jupiter?
Can be heat from grav pot energy left over from formation
What is the source of internal heat for Saturn (and Jupiter)?
Ongoing differentiation from He rain out, releasing grav pot energy
What is the source of internal heat for Neptune?
Ongoing differentiation of metals/rocks
What is the description of the atmosphere of Jupiter?
Bright zones via reflective clouds of ice and dark belts
What is the origin of the great red spot for Jupiter?
It is a storm at shearing boundary
What is the description of the atmosphere of Saturn?
Similar bonding pattern to Jupiter, but muted due to clouds forming deeper in the colder atmosphere
What is the description of the atmosphere of Neptune?
Colder with ice clouds deeper and bonding more muted
