Explosive Events
High-resolution ultraviolet (UV) spectra of the solar outer atmosphere show transient brightenings often referred to as explosive events.  These are localized regions with small spatial extent that show sudden enhancements of line intensities associated with strong non-Gaussian broadenings at temperatures between 20,000 -- 200,000 K. Several thousand of these occur on the Sun every hour.
 

Explosive events in O VI (~250,000K)
 

A sequence of Explosive events as viewed in Si IV. Although they play a role in heating the corona, they are not sufficient in number or energy to be only source.