"Electric units, called "international," for current and resistance had been introduced by the International Electrical Congress held in Chicago in 1893, and the definitions of the international" ampere and the "international" ohm were confirmed by the International Conference of London in 1908.
Although it was already obvious on the occasion of the 8th CGPM (1933) that there was a unanimous desire to replace those "international" units by so-called "absolute" units, the official decision to abolish them was only taken by the 9th GPM (1948), which adopted for the unit of electric current, the ampere," which see.
The previous is an excerpt from WWW version of the National Institute of Standards and Technology: Physics Laboratory's International System of Units (SI).
|carbon dioxide (CO2)||0.0314 (variable)|
|methane (CH4)||0.0002 (variable)|
|nitruous oxide (N2O)||0.00005|
I. Forms without ray structure:
HA (abbr for homogeneous quiet area). These can appear near the horizon, and between the arc and the horizon a dark segment is often seen. These arcs can be narrow or broad, and are very often diffuse along the upper border but sharp along the lower one.
HB (abbr for homogeneous bands). These forms do not have the regular shape of the arcs; they are more rapidly moving phenomena. The lower border is often irregular and sharp. The breadth can vary from a very narrow band to a band which is so large that it resembles a curtain hanging down. These bands very often turn into bands with ray structure.
PA (abbr for pulsating arcs). Parts of an arc flash up and disappear regularly within a period of about 20 seconds. This form quite often stands isolated in the sky without other auroras.
DS (abbr for diffuse luminous surfaces). These either appear like a diffuse veil or glow over great parts of the heavens without distinct boundaries, often appearing after intense displays of rays and curtains, or as more isolated feeble luminous streaks which sometimes bear a striking resemblance to clouds. Sometimes large areas of the heavens can be discolored by a green, violet, or red diffuse light.
PS (abbr for pulsating surfaces). Diffuse patches appear and disappear rhythmically at the same place, retaining the same irregular shape. When the patches are lying near the magnetic zenith the contours can be more sharp, and form a sort of corona. These forms appear often in connection with flaming auroras.
G (abbr for feeble glow near the horizon resembling the dawn). Of white or redlike color, this form is often the upper part of an arc whose lower border is below the horizon.
For more information,about auroras, visit Auroras: Paintings in the Sky.