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

  1. The Astronomical Unit is very close to 150 million kilometres.
  2. The mean solar photospheric temperature is around 6000 C.
  3. Light takes about 8 minutes to reach the Earth from the Sun.
  4. The dark centre of a sunspot is the umbra. The lighter surround is the penumbra.
  5. Coronal holes are believed to be associated with recurrent geomagnetic storms.
  6. Core neutrino emission and helioseismology are two probes of the sun's interior.
  7. The average height of a typical meteor is around 100 km.
  8. The average length of the sunspot cycle is 11 years.
  9. The "Butterfly diagram' shows the migration of sunspot group appearances from middle to low latitudes throughout the course of the sunspot cycle.
  10. Stanley Hey (UK) identified radar interference as solar radio emission in 1942.
  11. The sunspot number R=k(10g+s): g=number of spot groups, s=number of umbra.
  12. A geomagnetic storm affects HF communication, geomagnetic exploration and aurora.
  13. The F-layer is the most important ionospheric layer for communication.
  14. Magnetic disturbances are more probable around the equinox months.
  15. A PCA is a polar cap absorption.
  16. The average geomagnetic field is roughly one gauss, or 10-4 Tesla.
  17. The D-region is the ionospheric layer responsible for greatest absorption.
  18. An SID will cause a sudden phase advance of a VLF signal.
  19. The geomagnetic K-indices may have integer values from 0 to 9.
  20. Galileo was the first person in modem history to observe and study sunspots.
  21. The Maunder Minimum was the period 1645 to 1710 when very few sunspots were seen.
  22. A geomagnetic storm may occur 1 to 3 days after a large solar flare.
  23. Spacecraft charging and soft memory errors may be caused by energetic particles.
  24. The MUF is the maximum usable frequency.
  25. The solar wind is a constant outward stream of particles from the Sun.
  26. An SWF occurs only in signal propagation through the daylight side of the Earth.
  27. Ionospheric electron content changes may affect satellite navigation systems.
  28. Jupiter is the second most powerful natural radio source in the solar system.
  29. A low Earth orbit that passes near the polar regions receives most radiation.
  30. Aurorae are more intense and more widespread during large geomagnetic storms.
  31. The geosynchronous orbit is about 36,000 km above the Earth's surface.
  32. An SSC is a sudden (geomagnetic) storm commencement.
  33. Solar radio emission at 3000 MHz gives a good overall indicator of solar activity.
  34. 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.
  35. The D and E ionospheric layers disappear during night-time hours.
  36. The ionospheric D-region normally lies around 90 km.
  37. A disappearing solar filament may be followed by a geomagnetic storm.
  38. At sunspot latitudes the Sun appears to rotate about once every 27 or 28 days.
  39. Satellite drag is correlated with both the solar F10.7 and the geomagnetic Ap indices.
  40. Extreme ultraviolet radiation is the primary agent of ionisation in the F-layer.


ASAAustralian Space Academy