The Hessdalen lights are unexplained nocturnal lights observed in 7.5-mile-long (12 km) Hessdalen valley in rural central Norway.
Contents
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. 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. Some hypothesise that the light is ionised iron dust.
Unusual lights have been reported in the region since at least the 1930s. Especially high activity occurred between December 1981 and mid-1984, in which period the lights were being observed 15–20 times per week, attracting many overnight tourists who arrived in for a sighting. As of 2010, 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 (Hessdalen AMS) was set up in the valley to register and record the appearance of lights.
Later, the EMBLA programme was initiated to bring 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 and even more speculations.
2 ions (electronic transition b4Σ−
g → a4Πu), with green emission lines, are transported by IAW. Electronic bands of O+
2 ions occur in auroral spectra. Electron-molecular ion dissociative recombination coefficient rates α as functions of electron temperature Te, and cross sections σ as a function of electron energy E, have been measured by Mehr and Biondi for N+
2 and O+
2 over the electron temperature interval 0.007–10 eV. The estimated temperature of HL is about 5,000 K. In this temperature, the rate coefficients of dissociative recombination will be respectively α(Te)[O+
2] ~ 10−8 cm3 s−1, and α(Te)[N+
2] ~ 10−7 cm3 s−1. Thus, the nitrogen ions will be decomposed in N+
2 + 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 O+
2 with electronic transition b4Σ−
g → a4Πu 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 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, νcut, 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.