The Hessdalen lights are unexplained lights observed in a stretch of the Hessdalen valley in rural central Norway.
History and description
The Hessdalen lights are of unknown origin. They appear both by day and by night, and seem to float through and above the valley. They are usually bright white, yellow or red and can appear above and below the horizon. The duration of the phenomenon may be a few seconds to well over an hour. Sometimes the lights move with enormous speed; at other times they seem to sway slowly back and forth. On yet other occasions, they hover in mid‑air. Unusual lights have been reported in the region since at least the 1930s. Especially high activity occurred between December 1981 and mid-1984, during which the lights were being observed 15–20 times per week, attracting many overnight tourists who arrived in for a sighting., the number of observations has dwindled, with only 10 to 20 sightings made yearly.
Research
Since 1983, there has been ongoing scientific research, referred to as "Project Hessdalen", initiated by UFO-Norge and UFO-Sweden. This project was active as field investigations during 1983–1985. 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. In 1998, the Hessdalen Automatic Measurement Station was set up in the valley to register and record the appearance of lights. Later, a programme, named EMBLA, was initiated to bring together established scientists and students into researching these lights. Leading research institutions are Østfold University College and the Italian National Research Council.
Hypotheses
Despite the ongoing research, there is no convincing explanation for the phenomenon. However, there are numerous working hypotheses and even more speculations.
One possible explanation attributes the phenomenon to an incompletely understood combustion involving hydrogen, oxygen and sodium, which occurs in Hessdalen because of the large deposits of scandium there.
One recent hypothesis 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. Several physical properties including oscillation, geometric structure, and light spectrum, observed in the Hessdalen lights can be explained through a dust plasma model. Radon decay produces alpha particles and radioactive elements such as polonium. In 2004, Teodorani 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.
There have been some sightings positively identified as misperceptions of astronomical bodies, aircraft, car headlights and mirages.
Piezoelectricity
Another hypothesis explains Hessdalen lights as a product of piezoelectricity generated under specific rock strains, because many crystal rocks in Hessdalen valley include quartz grains which produce an intense charge density. In a 2011 paper, based on the dusty plasmatheory of Hessdalen lights, Gerson Paiva and Carlton Taft suggested that piezoelectricity of quartz cannot explain a peculiar property assumed by the Hessdalen lights phenomenonthe presence of geometrical structures in its center. Paiva and Taft have shown a mechanism of light ball cluster formation in Hessdalen lights by nonlinear interaction of ion-acoustic and dusty-acoustic waves with low frequency geoelectromagnetic waves in dusty plasmas. The theoretical velocity of ejected light balls is about, in good agreement with the observed velocity of some ejected light balls, estimated at. The central ball is white, while the ejected balls that are observed are always green in colour. This is ascribed to radiation pressure produced by the interaction between very low frequency electromagnetic waves and atmospheric ions through ion-acoustic waves. O ions, with green emission lines, are probably the only ones transported by these waves. Electronic bands of O ions occur in auroral spectra. The estimated temperature of Hessdalen lights is about. At this temperature, the rate coefficients of dissociative recombination will be for the oxygen ions, and for the nitrogen ions. Thus, in the Hessdalen lights plasma, the nitrogen ions will decompose more rapidly than oxygen ions. Only ionic species are transported by ion acoustic waves. Therefore, oxygen ions will dominate in the ejected green light balls in Hessdalen lights, presenting a negative band of O with electronic transition after ion-acoustic wave formation. Paiva and Taft presented a model for resolving the apparently contradictory spectrum observed in Hessdalen lights. The spectrum is nearly flat on the top with steep sides, due to the effect of optical thickness on the bremsstrahlung spectrum. At low frequenciesself-absorption modifies the spectrum to follow the Rayleigh–Jeans part of the blackbody curve. Such a spectrum is typical of dense ionized gas. Additionally, the spectrum produced in the thermal bremsstrahlung process is flat up to a cutoff frequency, νcut, and falls off exponentially at higher frequencies. 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.
