TEST YOUR KNOWLEDGE - ANSWERS ABOUT THE NEAR SPACE ENVIRONMENT
These are the suggested answers to the "TEST YOUR KNOWLEDGE" quiz on the Near Space Environment
- The Astronomical Unit is very close to 150 million kilometres.
- The mean solar photospheric temperature is around 6000 °C.
- Light takes about 8 minutes to reach the Earth from the Sun.
- The dark centre of a sunspot is the umbra. The lighter surround is the penumbra.
- Coronal holes are believed to be associated with recurrent geomagnetic storms.
- Core neutrino emission and helioseismology are two probes of the sun's interior.
- The average height of a typical meteor is around 100 km.
- The average length of the sunspot cycle is 11 years.
- The "Butterfly diagram' shows the migration of sunspot group appearances from middle to low latitudes throughout the course of the sunspot cycle.
- Stanley Hey (UK) identified radar interference as solar radio emission in 1942.
- The sunspot number R=k(10g+s): g=number of spot groups, s=number of umbra.
- A geomagnetic storm affects HF communication, geomagnetic exploration and aurora.
- The F-layer is the most important ionospheric layer for communication.
- Magnetic disturbances are more probable around the equinox months.
- A PCA is a polar cap absorption.
- The average geomagnetic field is roughly one gauss, or 10-4 Tesla.
- The D-region is the ionospheric layer responsible for greatest absorption.
- An SID will cause a sudden phase advance of a VLF signal.
- The geomagnetic K-indices may have integer values from 0 to 9.
- Galileo was the first person in modem history to observe and study sunspots.
- The Maunder Minimum was the period 1645 to 1710 when very few sunspots were seen.
- A geomagnetic storm may occur 1 to 3 days after a large solar flare.
- Spacecraft charging and soft memory errors may be caused by energetic particles.
- The MUF is the maximum usable frequency.
- The solar wind is a constant outward stream of particles from the Sun.
- An SWF occurs only in signal propagation through the daylight side of the Earth.
- Ionospheric electron content changes may affect satellite navigation systems.
- Jupiter is the second most powerful natural radio source in the solar system.
- A low Earth orbit that passes near the polar regions receives most radiation.
- Aurorae are more intense and more widespread during large geomagnetic storms.
- The geosynchronous orbit is about 36,000 km above the Earth's surface.
- An SSC is a sudden (geomagnetic) storm commencement.
- Solar radio emission at 3000 MHz gives a good overall indicator of solar activity.
- A geomagnetic crochet is a small increase in the magnetic field during an extremely large flare. Massive X-ray induced D-layer ionisation is the cause.
- The D and E ionospheric layers disappear during night-time hours.
- The ionospheric D-region normally lies around 90 km.
- A disappearing solar filament may be followed by a geomagnetic storm.
- At sunspot latitudes the Sun appears to rotate about once every 27 or 28 days.
- Satellite drag is correlated with both the solar F10.7 and the geomagnetic Ap indices.
- Extreme ultraviolet radiation is the primary agent of ionisation in the F-layer.
Australian Space Academy