In his paper “Local SETI” –a reading we recommend--  astrophysicist Dr. Massimo Teodorani brings an explanation for the vast majority of the luminous phenomena seen, detected and registered in the Hessdalen valley, Norway.

The explanation that follows, has been reached thanks to years of work in the area.

Nevertheless, there are still a small percentage of lights, which do not admit such an explanation, and therefore they are the stimulus for current and future investigation. It is possible that they are due to unknown natural or artificial human causes. The last possibility would be an exogenous one. But we can not reach this as a possible explanation before we are able to discard properly the other previous two.

Meanwhile, this is the explanation given by Dr. Teodorani himself:

Very recently one more complete theory, which is able to explain most of the recorded data, has been carefully elaborated (Teodorani, 2004). Such a theory, which was originally worked out by physical chemist David Turner (2003) in order to explain the ball lightning phenomenon (Stenhoff, 1999), has demonstrated to be very suitable to explain the Hessdalen-like phenomena too. It consists of a thermo-chemical mechanism producing and maintaining light balls whose structure and radiant characteristics seem to match at least 80% of the phenomena of which measurements were carried out in Hessdalen. In a first phase .  named .Tectonic Trigger Phase. - air can be ionized by tectonic stress causing simultaneously piezoelectricity and the emission of VLF and UHF waves, so that a plasma ball can be formed from the wave-particle interaction (Zou, 1995). In the specific Hessdalen area tectonic stress can be produced by river water that penetrates into the many ground cavities present in the valley and that then freezes when temperature drops down: in such a way the ice compresses the many quartz rocks which are present in the area so that the best condition for piezoelectricity is produced. The development and maintenance of this mechanism is also assisted by the presence in the valley of a large quantity of copper, having its well-known conductive property. In a second phase (Turner, 2003) . named .Thermo-Chemical Confinement Phase. - the formed plasma can bind with water vapor and aerosols, to create a hot and sharp-edged light ball with a cool water-and-ion coat, in which electrical and thermo-chemical energy exchanges occur following the mode of a heat pump. In such a way some inward forces are able to counterbalance the external pressure and the light ball is consequently self-regulated in a sort of hydrostatic equilibrium. Surface energy re-minimization can determine both ball clustering and ball ejection effects. The typical erratic motion and kinematical characteristics can be explained by asymmetries in the layer of droplets of the light balls, which can be caused by changes in either the chemical or electrical state.  In the specific Hessdalen case, a possible spontaneous production of almost monodisperse quantum dots might come from mold spores, as the main semi-conducting elements, decomposed by the central plasma of the light ball. This could explain successfully not only the recorded LED-like spectrum but also the existence of balls of distinctly different colors. Some of the radar and infrared observed behaviors can be explained using this model as well.