Aurora

An aurora is a luminous display in a planet’s upper atmosphere, produced when energetic charged particles excite atmospheric gases. Its colors and forms depend on the gases, particle energies, and altitude.

Solar wind: A stream of charged particles flowing outward from the Sun through the Solar System. Its particles supply much of the energy that drives auroras on Earth.
Earth's magnetic field: The magnetic field surrounding Earth, generated mainly by motion in its liquid outer core. It shapes the routes charged particles follow before they reach the upper atmosphere.
Space weather: Conditions in space, especially near Earth, shaped by solar activity and capable of affecting technology and infrastructure. Auroral intensity and location offer visible signs of changing space-weather activity.
Aurora borealis: The auroral display visible in the northern polar regions of Earth. It is the best-known terrestrial example of the phenomenon.
Auroral kilometric radiation: Intense radio emissions generated above Earth’s auroral regions, chiefly at kilometric wavelengths. Its production is linked to auroral particle acceleration and provides a remote probe of those regions.
Magnetosphere: The region around a celestial body where its magnetic field controls the motion of charged particles. Earth’s magnetic field guides many incoming particles toward auroral regions.
Ionosphere: A region of the upper atmosphere containing enough ions and free electrons to affect radio waves and electrical currents. Auroral particle impacts deposit energy in this electrically active atmospheric region.
Geomagnetic storm: A disturbance of Earth’s magnetosphere caused by energy transferred from the solar wind. Strong storms can expand auroras toward lower latitudes and intensify their displays.
Aurora australis: The auroral display visible in the southern polar regions of Earth. It is Earth’s southern counterpart to the northern aurora.
Alfvén wave: A magnetohydrodynamic wave that propagates through a plasma along magnetic-field structures. Alfvén waves can carry energy toward the atmosphere and accelerate particles that create auroras.

Linked from 42 pages