[3] Especially high activity occurred between December 1981 and mid-1984, during which the lights were observed 15–20 times per week, attracting many overnight tourists.
A group of students, engineers, and journalists collaborated as "The Triangle Project" in 1997–1998 and recorded the lights in a pyramid shape that bounced up and down.
[10][11] One hypothesis put forward in 2010 suggests that the lights are formed by a cluster of macroscopic Coulomb crystals in a plasma produced by the ionization of air and dust by alpha particles during radon decay in the dusty atmosphere.
[12] Radon decay produces alpha particles (responsible by helium emissions in HL spectrum) and radioactive elements such as polonium.
In 2004, physicist Massimo Teodorani[13] showed an occurrence where a higher level of radioactivity on rocks was detected near the area where a large light ball was reported.
Computer simulations show that dust immersed in ionized gas can organize itself into double helixes like some occurrences of the Hessdalen lights; dusty plasmas may also form in this structure.
[12] In a 2011 paper, based on the dusty plasma theory of Hessdalen lights, Gerson Paiva and Carlton Taft suggested that piezoelectricity of quartz cannot explain a peculiar property assumed by the Hessdalen lights phenomenon – the presence of geometrical structures in its center.
Paiva and Taft presented a model for resolving the apparently contradictory spectrum observed in Hessdalen lights.
This sequence of events forms the typical spectrum of Hessdalen lights phenomenon when the atmosphere is clear, with no fog.
According to the model, the spatial color distribution of luminous balls commonly observed in Hessdalen lights phenomenon is produced by electrons accelerated by electric fields during rapid fracture of piezoelectric rocks under the ground.