- The Naga Fireballs: Light phenomenon that occurs in late October on the Mekong River in Southeast Asia every year. Little orange fireballs rise up out of the river shooting up to about a hundred meters from the river’s surface quickly, where they later burn out and disappear. They might occur in the thousands, though some years have recorded as few as 30. They are hypothesized to be either of the two explanations which are not peer reviewed provided below.
A. Simple fireworks, shot skyward as a tourist attraction which is thought to be the best explanation with reference to Brian Dunning of Skeptoid.
In 2002, a television network called iTV sent a crew of investigative journalists to find the source of the fireballs during the festival. On the program titled Code Cracking, the team took a boat and snuck quietly up the Laotian side of the river, directly across from Phon Phisai, during the festival. They filmed Laotian soldiers firing tracer rounds into the air, and every time they did, the crowds on the Thailand side of the river reacted with their "oohs" and "aahs". The broadcast was widely perceived as an attack on a sacred belief. Lawsuits and boycotts were threatened against iTV.
B. Movement of the phosphine gas floating off the water surface. Phosphine is slightly more volatile than methane, but this explanation should require special circumstances to be consistent over time.
"The phenomenon is caused by flammable phosphine gas," deputy permanent secretary Saksit Tridech said. The ministry launched a scientific expedition on Friday to measure and observe the annual manifestation in Nong Khai province.
“Will o’ the wisp”/ignis fatuus: Phenomenon involving faint flames or a flickering, glowing fog, usually green, that sometimes appears to recede if approached. The scientific lab demonstration by Luigi Garlaschelli explains the 'will o’ the wisp' phenomenon as the decomposition of phosphorous acid generated phosphine which caused a fog formation in the flask. A faint, pale-greenish light was noted to be clearly visible when air and nitrogen stream was fed into the phosphine vapors. However, Massimo Polidoro who coinvestigated the phenomenon with Luigi Garlaschelli could not replicate the lab success in the field (cemeteries, graveyards, marshes) and more peer reviewed field and lab evidence is needed for explaining Will o’ the wisp.
Min Min lights: Referring to Professor John D. Pettigrew's explanation of the Min Min lights in the peer reviewed journal Clinical and Experimental Optometry, a natural or man-made source of light is refracted to an observer who is separated by long distance which can be hundreds of kilometres away by an inverted mirage or Fata Morgana.
An optical explanation of the Min Min light phenomenon is offered, based on a number of direct observations of the phenomenon, as well as a field demonstration, in the Channel Country of Western Queensland. This explanation is based on the inverted mirage or Fata Morgana, where light is refracted long distances over the horizon by the refractive index gradient that occurs in the layers of air during a temperature inversion. Both natural and man-made light sources can be involved, with the isolated light source making it difficult to recognise the features of the Fata Morgana that are obvious in daylight and with its unsuspected great distance contributing to the mystery of its origins.
4. Hessdalen Lights: Unexplained light ball phenomenon seen in the valley of Hessdalen, Norway is hypothesized to be caused by
A. Artifact light sources such as commercial and private aircraft operating near observation sites which are similar to known physical phenomena such as the Marfa Lights in Texas, the Min Min Light in Australia, and the Brown Mountain Lights in North Carolina when referring to Marsha Adams of the International Earthlight Alliance in her 2006 paper 'Air Navigation Artifacts near the Hessdalen Valley, Norway'.
Using simple commercially available navigation software, she identified a number of air traffic corridors, VOR navigational stations, and local airports. These included one corridor that I found particularly intriguing: a corridor 18° North from the Tolga VOR, proceeding directly up the Hessdalen valley, straight toward the Automated Measuring Station, from exactly the direction it's facing.
B. Incompletely understood combustion process in the air involving clouds of dust from the valley floor containing scandium. However, this source has reference to only one peer reviewed article and scandium found in higher densities elsewhere is not known to cause the same observable phenomenon.
C. 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. Source is peer reviewed.
D. Product of piezoelectricity generated under specific rock strains. Source is peer reviewed.
5. Chir Batti: Unexplained light phenomena viewed in the Banni grasslands, a seasonal marshy wetland and adjoining desert of the marshy salt flats of the Rann of Kutch near the India–Pakistan border in Kutch district, Gujarat State, India. There is no scientific peer reviewed exploration yet for this phenomenon and igneous gas mechanism is thought to be the process behind this without any other solid evidence.
Most ignes fatui are caused by the oxidation of phosphine (PH3), diphosphane (P2H4), and methane(CH4). These compounds, produced by organic decay, can cause photon emissions. Since phosphine and diphosphane mixtures spontaneously ignite on contact with the oxygen in air, only small quantities of it would be needed to ignite the much more abundant methane to create ephemeral fires. Furthermore, phosphine produces phosphorus pentoxide as a by-product, which forms phosphoric acid upon contact with water vapor.
Most of the above answer is mainly referenced from Skeptoid episodes present here, here, here.