Figure 2: Time evolution of mean charge amplitude, 
, in log-linear plots.
, in log-linear plots.From: Self-charging of identical grains in the absence of an external field
(a) χe is fixed and η is varied. (b) η is fixed and χe is varied. (c) Exponential growth rates from the slope of linear fits of log10(
) vs. time plots for an for array of parameters. Growth rates are defined as: 
, where b is a constant. Colored spots correspond to colors used in panels (a) and (b), and breathing modes are discussed in text.
