  A complete framework for exciting and detecting thermally-induced, stabilized
sine-Gordon breathers in ac-driven long Josephson junctions is developed. The
formation of long-time stable breathers locked to the ac source occurs for a
sufficiently high temperature. The latter emerges as a powerful control
parameter, allowing for the remarkably stable localized modes to appear.
Nonmonotonic behaviors of both the breather generation probability and the
energy spatial correlations versus the thermal noise strength are found. The
junction's resistive switching characteristics provides a clear experimental
signature of the breather.
