PHYS6074: Revision 1

In which layer does temperature decrease with altitude?

• Thermosphere

• Mesosphere

• Stratosphere

• Exosphere

What is the most common atmospheric species in the homosphere, below the homopause?

What is typically the most common atmospheric species at 250 km altitude in the thermosphere?

Where would you expect the scale height to be smallest?

• Mesopause

• Upper thermosphere

• Ground level

• Stratopause

Which of these is photodissociation?

What does the optical depth quantify?

• Reduction of solar irradiance by absorption

• Intensity of an airglow emission line

• Number of molecules in a column of atmosphere

• Pressure gradient with altitude

Where is solar photon energy deposition the greatest if the Sun is directly overhead?

• Where optical depth is 1

• Exopause

• Mesopause

• Where the scale height is equal to the mean free path

Which of these is the major heat transport process in the thermosphere?

• Radiative transport

• Conduction

• Eddy diffusion

• Joule heating

Why does the thermospheric temperature increase with altitude?

• Radiative cooling is more efficient at lower altitudes

• The heat source (Sun) is above the thermosphere

• Joule heating is more efficient at higher altitudes

• Conduction is faster at lower altitudes

When and where is atmospheric drag on a spacecraft in low Earth orbit greatest?

• Solar maximum, lower altitudes

• Solar minimum, lower altitudes

• Solar maximum, higher altitudes

• Solar minimum, higher altitudes