On the speed and acceleration of electron beams triggering interplanetary type III radio bursts V. Krupar, E. P. Kontar, J. Soucek, O. Santolik, M. Maksimovic and O. Kruparova A&A, 580 (2015) A137 Published online: 19 August 2015 DOI: 10.1051/0004-6361/201425308