Direct observation of solar wind proton heating from in situ plasma measurements F. S. Mozer, O. V. Agapitov, J. C. Kasper, R. Livi, O. Romeo and I. Y. Vasko A&A, 673 (2023) L3 Published online: 27 April 2023 DOI: 10.1051/0004-6361/202346202