Classical novae are powered by thermonuclear runaways that occur on the white dwarf component of close binary systems .
During these violent stellar events , whose energy release is only exceeded by gamma-ray bursts and supernova explosions , about 10 ^ { -4 } -10 ^ { -5 } M _ { \sun } of material is ejected into the interstellar medium .
Because of the high peak temperatures attained during the explosion , T _ { peak } \sim ( 1 - 4 ) \times 10 ^ { 8 } K , the ejecta are enriched in nuclear-processed material relative to solar abundances , containing significant amounts of ^ { 13 } C , ^ { 15 } N , and ^ { 17 } O and traces of other isotopes .
The origin of these metal enhancements observed in the ejecta is not well-known and has puzzled theoreticians for about 40 years .
In this paper , we present new 2-D simulations of mixing at the core-envelope interface .
We show that Kelvin-Helmholtz instabilities can naturally lead to self-enrichment of the solar-like accreted envelopes with material from the outermost layers of the underlying white dwarf core , at levels that agree with observations .