Umbral chromospheric fine structure and umbral flashes modelled as one: The corrugated umbra Vasco M. J. Henriques, Chris J. Nelson, Luc H. M. Rouppe van der Voort and Mihalis Mathioudakis A&A, 642 (2020) A215 Published online: 22 October 2020 DOI: 10.1051/0004-6361/202038538