// Colours

Auroral colours are from forbidden transitions, transitions or mechanisms in spectroscopy that have minimal or close to no probability of occuring on Earth. Spectroscopy analyses light and measures emitted or absorbed wavelengths to determine the substances emitting or absorbing light. Spectral measurements of aurora were first taken in 1866-67 (by Swedish physicist Ångström), and showed that aurora produced a line spectrum – specific bands of colour – and not a continuous blend of hues. This established that, rather than reflecting light from the sun aurora shone with its own light.  Forbidden transitions have only been observed in extremely low-density gases and plasmas in outer space or the upper atmosphere. Therefore the colours did not match any known element, and the identified lines were attributed names like Aurorium and Geocoronium (see Naming).

The atoms and molecules emitting the auroral light were later (1925) recognised as oxygen, emitting greenish-yellow (the most familiar color of the aurora) or red light (only possible higher up in the ionosphere thanks to rarefied air and less collisions), and nitrogen giving off blue light. Combined with which kind of atom or molecule is hit, the amount of emitted energy determines the colour; the higher the energy the higher the frequency. Green is the most common. Red, purple, pink and blue are generally to be seen during bigger  solar storms. Another reason why we see more green aurora than red is that the eye is more sensitive to green, particularly at night when eyes are sensitive to low-intensity light only in black and white. Other gases in the atmosphere become excited and emit light, although the wavelengths may be outside of the range of human vision or else too faint to see. Hydrogen and helium, for example, emit blue and purple. Although our eyes can't see all of these colors, photographic film and digital cameras often record a broader range of hues (P for Photography?, T for Technological eye?, I for Ionosphere, Instruments…?). This is also why witnesses often report white auroras, as the auroral light might be too faint for the human eye to make out its colours.

// Communication, Commons

But as it has become later known, the colours that define the aurora are visible manifestations of much broader electromagnetic phenomena — the ionosphere, an elusive, electrically active region of the upper atmosphere composed of gases ionised by ultraviolet radiation from the Sun and filled with free electrons that bounce back the planetary radio waves from one part of the globe to another, as in the famous Macroni experiment. This bouncing not only revealed the existence of the invisible ionosphere, importantly it has become to play a critical part of modern long-distance communication — first, used in the transatlantic wireless radio broadcasting, later by hosting the telecommunication satellites (this needs to be clarified and maybe use Lisa Parks).

Unlike the science of colors driven by romantic curiosity and enlightenment, much of what we know and how we use electromagnetic spectrum (including that one used for telecommunication) as well as spaces of its propagation (such as ionosphere) has been made perceptible to us not through the scientific experimentation but through the intrinsic entanglement of science, militarization and commercialization, which has rendered the planetary electromagnetic fields as a strategic resource to be exploited and an invisible frontier to be enclosed through the expansion of capital. Here need to provide cold-war and privatization examples / commons
As a result, most of the electromagnetic spectrum useful for telecommunications is exclusively licensed, legally supervised and its use is highly sanctioned; thus although being a cosmic phenomenon (cosmic commons), its ‘improper’ utilization can be treated as theft or act of terrorism.

Looking at the historical processes of the capitalist enclosure of electromagnetic domain, historian Edward D. Mellilo highlights the curious case of double invisibility — the processes of exploiting the invisible commons are as much as invisible. In extension, not only the electromagnetic phenomena need to be rendered perceptible, equally there is a need to ‘render visible the aggressive regimes of their privatization’. Treating the process of ‘rendering visible’ as a dual task — of making visible the processes of electromagnetic phenomena and the processes of their exploitation — is a critical one because it gives a possibility to recast the commons in the electromagnetic spectrum as the possible space for fostering ‘freedoms other than exploitative agency’(Note 1).

Practically doing this, the ‘Installation guide for autonomous communication’ highlights the existence of the 2.4GHz and 5GHz bands, which remain exempt to legislative licensing and thus can be accessed and used indiscriminately (Note 2).

Last sentence

Note 1: Mellilo E.D, Spectral Frequences: Neoliberal Enclosures of the Electromagnetic Commons. Radical History Review, no. 112 (Winter 2012): 147-61.
Note 2: Dyer S. and Thanki R,

︎P ...︎B - D︎ ... N︎