Aurora - Space Environment Center Document

Contact Information

• Space Environment Center
  325 Broadway, Boulder, CO 80303-3326
  SE-12, Phone: (303) 497-5127

The Aurora

• Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights):
  Beautiful curtains of light in the night sky, often associated with myths and legends across cultures.

• Cultural Significance:
  Myths include signs of royal birth, ghosts, or precursors to war. Eskimos believed whistling at the aurora could result in dangerous consequences.

Origins and Phenomena

• Source of Aurora:
  Originates from the Sun, 93 million miles away. Energetic particles carried by the solar wind interact with Earth's magnetosphere.

• Magnetosphere:
  A comet-shaped shield formed by Earth's magnetic field, protecting against solar wind. Energetic particles spiral down towards the polar regions, creating the auroral display.

• Auroral Features:
  Appears as arcs and rays, starting about 100 km above the Earth’s surface, extending for hundreds of kilometers. Colors mainly include green and red, occasionally blue.

Science of Aurora

• Chemical Reactions:
  Involves high-energy particles (like electrons) colliding with atmospheric gases, exciting valence electrons, which then emit light.

• Colors of the Aurora:

  • Green Light: Wavelength of 557.7 nm.
  • Red Light: Wavelength of 630.0 nm.
  • Rare occurrences may show deep red or faint blue.

Solar Influence and Geomagnetic Activity

• Solar Variability:
  Solar wind speed, density, and interplanetary magnetic field influence geomagnetic activity and auroral visibility.

• Geomagnetic Storms:
  Can lead to auroral substorms, affecting power grids, satellite communication, and navigation systems.

Measuring Geomagnetic Activity

• Magnetometers:
  Used to measure geomagnetic fields, providing data for geomagnetic activity indices.

• K-index:
  A measure of geomagnetic activity over a 3-hour period, indicating the likelihood of auroral occurrences.

Resources for Observations

• Access pictures and data from sources like the Space Environment Center and other astronomical institutions.
• Practical guides, like "How to Photograph the Northern Lights" by Floyd Damron, offer insight into capturing auroral displays.

References and Further Reading

• Books:
  "Majestic Lights" by Robert H. Eather and "Aurora Borealis" by S.-I. Akasofu provide detailed insights into auroras.

• Online Resources:
  The Space Environment Center’s webpage and the National Geophysical Data Center offer additional resources and data.

Authors

• Written by Larry Combs and Rodney Viereck, 1996.

This document provides an overview of aurora phenomena, its origins, scientific basis, and cultural significance, along with resources for further exploration and observation.