Will-o’-the-Wisps

[BillTre]

A possible scientific explanation of fleeting flames occasionally seen world wide above swamps and graveyards in the dark of night (commonly known as will-o’-the-wisps, ignis fatuus, dancing bones, the hovering souls of dead children, and ghost lights) has been proposed. These are fleeting flames occasionally seen above swamps and graveyards in the dark of night. They are thought to have something to do with methane gas being produced in those areas and somehow getting ignited.
The methane production from decaying organic matter is not that surprising, but the ignition source has until now not been explained.

In recent years, Richard Zare, a chemist at Stanford University, and his colleagues have studied how tiny bubbles, just nanometers to micrometers in size, can generate strong electric fields, sparking reactions. When bubbles of different sizes form at the interface between water and air, charges on their surfaces separate, with negative charges accumulating on smaller bubbles, leaving larger ones more positively charged. This creates electric fields across small distances that trigger what amounts to bursts of microlightning as the charges attempt to equalize.

The sparking can happen even when the bubbles contain air without methane.
Science research news article
PNAS article

 

[.Scott]

I read the article. ..
So we can have ignition.
For methane, the concentration in air needs to be between 5 and 15%. So, presumably it starts out near the surface at a high concentrations, then drifts upwards to where a flame is sustained.

I think we still have a few dots to connect.

 

[Baluncore]

I think we still have a few dots to connect.

True.

But it’s been unclear how this gas could catch fire.

The methane is not alone. There are many other low-flashpoint gasses produced that will spontaneously ignite when released into the presence of oxygen. It only takes one molecule to decay, for a flame-front to propagate. The dilute and distributed nature of the gasses released, explains the shape of the quiet and low-energy combustion observed.
https://en.wikipedia.org/wiki/Will-o'-the-wisp#Scientific_explanations