PG2: Aurora

The ionosphere is approximately co-located with which region of the atmosphere?

• Mesosphere

• Thermosphere

• Troposphere

• Stratosphere

What is the major producer of the ionosphere?

• Solar UV

• Auroral particle precipitation

• Atmospheric chemistry

• Electric currents

Where are you most likely to see aurora?

• North pole

• Fairbanks, Alaska

• Stockholm, Sweden

• Tasmania, Australia

What is the typical width of an auroral arc?

• ~5 km

• ~50 km

• ~100 km

• ~1000 km

What kind of current is present above an auroral arc?

• Field-aligned current

• Pedersen current

• Ring current

• Hall current

What key feature is needed for the acceleration of auroral electrons?

• Parallel electric field

• High ionospheric electron density

• Curved magnetic field

• Fast solar wind

What energy of electron precipitation is most likely to cause ionisation in the D-region?

• 100 keV

• 20 keV

• 5 keV

• 50 eV

What two factors determine the penetration depth of precipitating electrons?

• Electron energy and atmospheric density profile

• Ionospheric electron density and magnetic field strength

• Electron energy and flux

• Solar wind speed and local time

What species produces the characteristic green light of the aurora?

Why is red 630.0 nm emission not bright at 100 km altitude?

• Quenching

• Excited state produced by low energy electrons

• O density is low

• It is clearly visible at 100 km!