Laststroms

Laststroms are a proposed class of transient atmospheric electrical discharges associated with thunderstorms. They are characterized by delayed, luminous emissions that persist longer than typical lightning strokes and by distinctive spectral and radiometric signatures. The name Laststroms reflects their appearance in the late phase of a storm and the electrical nature of the phenomenon.

Discovery and observation: Reports of late-phase luminous events emerged from high-speed photography and wide-field photometry of convective systems in the late 1990s and early 2000s. Observers describe a faint, diffuse glow or narrow, filamentary channels that appear after the main lightning activity ceases. Measurements show VLF and LF radio emissions correlated with the optical events.

Characteristics: Laststroms typically persist from a few tens of milliseconds to several seconds. They can emit across the visible spectrum with occasional strong emission lines and are sometimes accompanied by subtle acoustic or infrasound signatures. Morphology ranges from diffuse glows to slender filaments lingering near charge centers in thunderstorm anvils.

Formation theories: Proposed mechanisms include delayed dielectric breakdown in residual charge layers, sustained ionization from high-energy electrons accelerated in strong electric fields, and conductive channels formed by micro-scale networks within ice crystals and supercooled droplets.

Occurrence and significance: Most often observed in mature thunderstorm systems, particularly in intensively convective environments. Understanding Laststroms contributes to broader knowledge of atmospheric electricity and may improve detection of late-stage storm processes and electrical hazards.

See also: Ball lightning, sprites, streamer discharges, atmospheric electricity.