(color online) Boron combustion flame images under different discharge power levels. (a) No boron, (b) 0, (c) 5 W, (d) 10 W, (e) 15 W, (f) 19 W, (g) 24 w, (h) 30 W, (i) 36 W, (j) 40 W, (k) 47 W, (l) 51 W, (m) 56 W, (n) 63 W, (o) 76 W.