Stable umbral chromospheric structures V. M. J. Henriques, E. Scullion, M. Mathioudakis, D. Kiselman, P. T. Gallagher and F. P. Keenan A&A, 574 (2015) A131 Published online: 06 February 2015 DOI: 10.1051/0004-6361/201424664