Kinetic Interaction of Cold and Hot Protons With an Oblique EMIC Wave Near the Dayside Reconnecting Magnetopause Toledo Redondo, S. Porti Durán, Jorge Andrés Salinas Extremera, Alfonso STR acknowledges support from the ISSI international team Cold plasma of ionospheric origin in the Earth's magnetosphere and of the Ministry of Economy and Competitiveness (MINECO) of Spain (grant FIS2017-90102-R). Research at IRAP was supported by CNRS, CNES and the University of Toulouse. JHL and DLT acknowledge support from NASA Grant 80NSSC18K1378. RED was supported by NASA grants 80NSSC19K070 and 80NSSC19K0254. MA was supported by SNSA Grant 56/18. SKV and RCA acknowledge support from NASA Grant 80NSSC19K0270. Work performed by MMS team members is supported by NASA contract NNG04EB99C. We report observations of the ion dynamics inside an Alfvén branch wave that propagates near the reconnecting dayside magnetopause. The measured frequency, wave normal angle and polarization are consistent with the predictions of a dispersion solver. The magnetospheric plasma contains hot protons (keV), cold protons (eV), plus some heavy ions. While the cold protons follow the magnetic field fluctuations and remain frozen-in, the hot protons are at the limit of magnetization. The cold protons exchange energy back and forth, adiabatically, with the wave fields. The cold proton velocity fluctuations contribute to balance the Hall term fluctuations in Ohm's law, and the wave E field has small ellipticity and right-handed polarization. The dispersion solver indicates that increasing the cold proton density facilitates propagation and amplification of these waves at oblique angles, as for the observed wave. 2021-09-06T10:20:33Z 2021-09-06T10:20:33Z 2021-04-18 journal article Toledo-Redondo, S... [et al.] (2021). Kinetic interaction of cold and hot protons with an oblique EMIC wave near the dayside reconnecting magnetopause. Geophysical Research Letters, 48, e2021GL092376. [https://doi.org/10.1029/2021GL092376] http://hdl.handle.net/10481/70106 10.1029/2021GL092376 eng http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España Wiley-Blackwell Publishing