PHYS6074: Revision 2

Which ion is dominant in the F-region ionosphere?

Which of these is the main source of the ionosphere?

• Solar UV

• Auroral particle precipitation

• Cosmic rays

• Geomagnetic field

What happens to the photoionisation rate peak as the solar zenith angle increases away from vertical?

• Peak moves up in altitude and ionisation rate decreases

• Peak moves down in altitude and ionisation rate decreases

• Peak moves up in altitude and ionisation rate increases

• Peak moves down in altitude and ionisation rate increases

What are the main ions produced by photoionisation in the E-region?

What is the main loss mechanism of the E-region ionosphere?

• Dissociative recombination

• Radiative recombination

• Three-body recombination

• Photoionisation

Which ionospheric layer persists overnight?

• E-region

• D-region

• F2-region

• F1-region

What is the shape of the electron density profile in the E-region?

• Gaussian

• Maxwellian

What is ambipolar diffusion?

• Ions and electrons diffusing at the same rate

• Ions diffusing faster than electrons

• Electrons diffusing faster than ions

• Electrons and ions diffusing in opposite directions

Where does an HF radio wave transmitted straight up from the ground to the ionosphere reflect?

• Where the wave frequency equals the plasma frequency

• At the top of the ionosphere

• Where the optical depth is 1

• Where atomic O becomes the dominant species

What is a consequence of the ionospheric refractive index being complex?

• Absorption of radio waves

• Radio wave phase velocity becomes faster than group velocity

• Reflection of radio waves

• Visible auroral emission