Frequency rising sub-THz emission from solar flare ribbons E. P. Kontar, G. G. Motorina, N. L. S. Jeffrey, Y. T. Tsap, G. D. Fleishman and A. V. Stepanov A&A, 620 (2018) A95 Published online: 04 December 2018 DOI: 10.1051/0004-6361/201834124