Hessdalen lights

The Hessdalen lights are unexplained nocturnal lights observed in a 7.5-mile-long (12 km) Hessdalen valley in rural central Norway.^[1]

History and description

The Hessdalen lights are of unknown origin. They appear at 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 from a few seconds to longer than an hour. Sometimes the lights move with enormous speed, and at other times, seem to slowly sway back and forth. On yet other occasions, they hover mid‑air. Some hypothesise that the light is ionised iron dust.

Unusual lights have been reported in the region since at least the 1930s.^[2] Especially high activity occurred between December 1981 and mid-1984, at which point the lights were being observed 15–20 times per week, which attracted many overnight tourists.^[3] As of 2010, the lights were observed 10–20 times per year.

Research

Since 1983, there has been ongoing scientific research often nicknamed "Project Hessdalen", initiated by UFO-Norge and UFO-Sweden. The 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.^[4][5] In 1998, the Hessdalen Automatic Measurement Station (Hessdalen AMS) was built in the valley and registers and records the appearance of lights.

Later, the EMBLA programme was initiated. It brings together established scientists and students into researching these lights. Leading research institutions are Østfold University College (Norway) 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.

• One possible explanation attributes the phenomenon to an incompletely understood combustion involving hydrogen, oxygen, and sodium,^[6] and occurs in Hessdalen because of the large deposits of scandium there.^[7]
• 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 (HL) can be explained through a dust plasma model.^[8] Radon decay produces alpha particles (responsible by helium emissions in HL spectrum) and radioactive elements such as polonium. In 2004, Teodorani^[9] 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 of occurrences of the Hessdalen lights; dusty plasmas may also form in this structure.^[10]
• Another hypothesis explains HL as a product of piezoelectricity generated under specific rock strains (Takaki and Ikeya, 1998)^[8] because many crystal rocks include quartz grains which produce an intense charge density. In a 2011 paper,^[11] based on the dusty plasma theory of HL, it is suggested that piezoelectricity of quartz cannot explain a peculiar property assumed by the HL 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 the nonlinear interaction of ion-acoustic and dusty-acoustic waves with low frequency geoelectromagnetic waves in dusty plasmas. The theoretical model shows that the velocity of ejected light balls by HL cluster is about 10,000 m s⁻¹ in a good agreement with the observed velocity of some ejected light balls, which is estimated as 20,000 m s⁻¹.^[12] Why is the ejected ball always green-colored? Ejection of small green light ball from HL is due to radiation pressure produced by the interaction between very low frequency electromagnetic waves (VLF) and atmospheric ions (present in the central white-colored ball) through ion-acoustic waves (IAW).^[13] Probably only O₂⁺ ions (electronic transition b4Σ_g^- → a4Π_u), with green emission lines, are transported by IAW. Electronic bands of O₂⁺ ions occur in auroral spectra.^[14] Electron-molecular ion dissociative recombination coefficient rates α as functions of electron temperature T_e, and cross sections σ as a function of electron energy E, have been have measured by Mehr and Biondi^[15] for N₂⁺ and O₂⁺ over the electron temperature interval 0.007–10 eV. The estimated temperature of HL is about 5,000 K.^[9] In this temperature, the rate coefficients of dissociative recombination will be respectively α(T_e)[O₂⁺] ~ 10^-8 cm³ s^-1, and α(T_e)[N₂⁺] ~ 10^-7 cm³ s^-1. Thus, the nitrogen ions will be decomposed in N₂⁺ + e^- → N + N* more rapidly than oxygen ions in the HL plasma. Only ionic species are transported by IAW. Therefore, only oxygen ions will be predominant ejected green light balls from a central white ball in HL, presenting negative band of O₂⁺ with electronic transition b4Σ_g^- → a4Π_u after an IAW formation. Paiva and Taft presented a model for resolving the apparently contradictory spectrum observed in HL phenomenon. Thus, its nearly flat spectrum on the top with steep sides is due to the effect of optical thickness on the bremsstrahlung spectrum. At low frequencies self-absorption^[16] modifies the spectrum to follow the Rayleigh–Jeans part of the blackbody curve. This spectrum is typical of dense ionized gas. Additionally, the spectrum produced in the thermal bremsstrahlung process is flat up to a cutoff frequency, ν_cut, and falls off exponentially at higher frequencies. This sequence of events forms the typical spectrum of HL phenomenon when the atmosphere is clear, with no fog. According to the model, spatial color distribution of luminous balls commonly observed in HL phenomenon are produced by electrons accelerated by electric fields during rapid fracture of piezoelectric rocks under the ground.^[17]
• There have been some sightings positively identified as misperceptions of astronomical bodies, aircraft, car headlights, and mirages.^[1]

See also

• Ball lightning
• Hessdalen AMS
• Marfa lights
• Paulding Light
• Will-o'-the-wisp

References

External links

• Homepage of Project Hessdalen
• Project Hessdalen Bulletin, 1983–1985