2010 10 00 Journal of Atmospheric and Solar-Terrestrial Physics - Vol 72 No 16 - Paiva - Hessdalen

Magazine Overview

This document is a scientific paper published in the "Journal of Atmospheric and Solar-Terrestrial Physics", Volume 72, in 2010. The paper, titled "A hypothetical dusty plasma mechanism of Hessdalen lights", is authored by G.S. Paiva and C.A. Taft from the Centro Brasileiro de Pesquisas Físicas in Rio de Janeiro, Brazil. It explores a novel explanation for the phenomenon known as Hessdalen lights (HL).

Hessdalen Lights: An Unexplained Phenomenon

The paper begins by describing Hessdalen lights as unexplained glowing balls of light observed in Hessdalen, Norway. These lights vary in size from decimeters to 30 meters and can exhibit geometric structures, particularly at lower luminosity. They are predominantly seen at night, especially in winter, with a peak around midnight. Night vision systems reveal a strong infrared signature even when the lights are faint or invisible optically, and they often produce strong radar tracks. Additionally, HL are sometimes accompanied by short-duration pulsating spikes in HF and VLF radio ranges, occasionally showing Doppler features.

Existing theories for HL are insufficient to explain all observations. Some explanations include incompletely understood combustion processes involving dust, piezoelectricity generated by rock strain, or misperceptions of natural phenomena. The authors note that no single theory adequately accounts for the contradictory observations.

The Dusty Plasma Model for Hessdalen Lights

The paper proposes a new model where Hessdalen lights are formed by a cluster of macroscopic Coulomb crystals within a dusty plasma. A dusty plasma is defined as a plasma containing nanometer or micrometer-sized particles that behave like plasma themselves. Such plasmas are found in natural environments like comets, planetary rings, and noctilucent clouds.

The proposed mechanism involves the ionization of air and dust by alpha particles emitted during the decay of radon gas, which is prevalent in the Hessdalen area due to its geology (radon-rich soil and bedrock). Alpha particles ionize atoms in the air and dust, causing dust grains to become negatively charged by collecting electrons. Other charging mechanisms, like electron emission from alpha particle impact or secondary electron emission, also contribute. The net charge on the dust grain depends on the balance of these processes. The dust grains then emit light through electron capture, producing the observed HL spectrum.

Dust Particle Charging and Crystallization

Figure 1 illustrates the dust plasma formation process. Radon decay releases alpha particles (helium nuclei), which ionize surrounding air and dust. Dust particles, particularly those composed of minerals like thortveitite (containing scandium, silicon, and iron), can become charged. The paper highlights that while thortveitite itself doesn't luminesce under typical conditions, ionization by alpha particles can cause its constituent atoms to emit light as they transition to lower energy states or capture electrons. This process is suggested to produce the emission lines observed in HL.

The paper emphasizes Norway's high radon levels, linked to its geology and permeable sediments, facilitating radon migration and accumulation. Elements detected in HL spectra, such as nitrogen (N1 at 5281.7 Å), and trace elements like silicon, iron, and scandium, suggest dust from the valley floor, possibly thortveitite, is involved.

Calculations and Theoretical Support

The authors delve into calculations to support their dusty plasma model. They introduce the coupling parameter (Γ), which represents the ratio of potential energy to kinetic energy of charged particles in a plasma. For dust particles in HL, calculations based on estimated temperatures and electron densities (derived from solar photosphere data) yield a coupling parameter of Γ~4 × 107. This value significantly exceeds the critical coupling parameter (Γc=170-178) required for the formation of regular lattices, or Coulomb crystals, in dusty plasmas. This supports the hypothesis that dust particles in HL crystallize.

Depending on particle density, different geometric structures of Coulomb crystals can form, such as cubic, rectangular, or hexagonal lattices. The paper suggests that these structures explain the geometric shapes observed in Hessdalen lights.

Oscillation and Light Emission

The model also addresses the oscillatory behavior and light emission of HL. The paper posits that HL are formed by a cluster of "satellite" Coulomb crystals (negatively charged dust particles) surrounding a central luminous Coulomb crystal (positively charged dust particles), as depicted in Figure 2. Oscillations in laboratory dust plasmas, similar to those observed in HL, are attributed to mutual repulsion and restoring forces. The calculated oscillation frequency of approximately 5 Hz aligns well with the observed pulsating magnetic perturbations of 7 Hz associated with HL.

The strong infrared signature of HL is explained by electron capture from scandium ions (Sc-IV) within the thortveitite dust particles, with emission lines identified up to 1000 nm (infrared frequencies).

Conclusions

The paper concludes that Hessdalen lights are likely a manifestation of Coulomb crystals within a dusty plasma, originating from radon decay in the atmosphere. The alpha particles from radon decay are responsible for helium emissions and ionization, leading to the formation of these crystalline structures. The observed spectrum, including continuum with no resolved lines and exponential wings, is attributed to the blending of emission lines from various excited chemical elements and atmospheric turbulence smoothing the spectrum.

Recurring Themes and Editorial Stance

The journal "Journal of Atmospheric and Solar-Terrestrial Physics" consistently publishes research on atmospheric and space physics phenomena. This particular issue features a paper that applies plasma physics principles to an unexplained aerial phenomenon, demonstrating an interest in interdisciplinary approaches to understanding atmospheric and solar-terrestrial events. The editorial stance appears to be one that encourages rigorous scientific inquiry into anomalous phenomena, using established physical models and new theoretical frameworks to propose explanations.