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The Hessdalen lights are unidentified lights which have been observed in a 12-kilometre-long (7.5 mi) stretch of the Hessdalen valley in rural central Norway periodically since at least the 1930s.

The Hessdalen lights appear both by day and by night, and seem to float through and above the valley. Sometimes the lights move with enormous speed; at other times they seem to sway slowly back and forth. 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 observed 15–20 times per week, attracting many overnight tourists. Since 1983, "Project Hessdalen" initiated by UFO-Norge and UFO-Sverige have attempted to investigate the lights. 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 (Hessdalen AMS) was set up in the valley to register and record the appearance of lights.

The publication of this research led to the Norwegian press proclaiming that "The Mystery in Hessdalen is Solved". 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. Several physical properties including oscillation, geometric structure, and light spectrum, observed in the Hessdalen lights might be explained through a dust plasma model. 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. 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 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 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 10,000 m/s (33,000 ft/s), in good agreement with the observed velocity of some ejected light balls, estimated at 20,000 m/s (66,000 ft/s). 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 (VLF) and atmospheric ions (present in the central white-coloured ball) through ion-acoustic waves. The estimated temperature of Hessdalen lights is about 5,000 K (4,730 °C; 8,540 °F). Thus, in the Hessdalen lights plasma, the nitrogen ions will decompose (N+2 + e− → N + N*) more rapidly than oxygen ions. Therefore, oxygen ions will dominate in the ejected green light balls in Hessdalen lights, presenting a negative band of O+2 with electronic transition b4Σ−g → a4Πu after ion-acoustic wave formation. 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. In 2014, Jader Monari published a new Hessdalen Lights model involving a geological-like battery. Gas bubbles rise into the air and can become electrically charged producing gas luminesce and Hessdalen Lights phenomenon.

Quick Facts

• The Hessdalen lights appear both by day and by night, and seem to float through and above the valley.
• In 1998, the Hessdalen Automatic Measurement Station (Hessdalen AMS) was set up in the valley to register and record the appearance of lights.
• 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.
• Thus, in the Hessdalen lights plasma, the nitrogen ions will decompose (N+2 + e− → N + N*) more rapidly than oxygen ions.
• 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.

Source material: Wikipedia - "Hessdalen lights". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.