It seems that the emissions are generated by mild explosive activity still relatively deep inside the crater. So far, no images of incandescent ejecta on or outside the crater have appeared, but this might occur soon if activity increases.
According to VSI, volcanic tremor has been elevated with a tendency to increase during the past days.
However, our friends Oystein Lund Andersen sent us this photo. This one clearly shows a glow at the bottom of the crater of Bromo, indicating the presence of an incandescent source. So the activity takes a greater magnitude.
To be continued.
December 18, 2015. Bromo, Indonésia :
Source : Volcanodiscovery
Photo : Oystein Lund Andersen