Presentation #113.03 in the session “Solar Physics Division (SPD): Photosphere & Chromosphere, Solar Interior, and Solar Cycle”.
In this work, we present constraints on the longitudinal (compressive) and transverse (Alfvenic) wave velocity perturbations observed in the chromosphere. Better knowledge of the power in these different wave modes in different regions of the atmosphere are important inputs into models for the heating of the solar corona. By using observations at multiple viewing angles (distances from the disc center), the relative importance of these two components can be evaluated and the power in the local acoustic flux can be explored. This work is based on Doppler velocity measurements from IRIS of the ultraviolet Mg II h & k and the Mn I 280.19 nm lines. These are compared with co-temporal observations from IBIS of the H-alpha and Ca II 854.2 nm chromospheric lines in the visible. The observed phase differences between the velocity diagnostics in these different lines allows us to estimate a formation height of the Mn I 280.19 nm line and compare it with recent results from simulations. We can also measure the lowest observed frequency at which the phase differences indicate the presence of wave propagation in order to calculate the local acoustic-wave cutoff. We calculate the coherency of the signals and their phases with a cross-wavelet analysis. We further combine the IRIS observations with 1D simulations of the lower solar atmosphere from the RADYN code to estimate the wave flux inthe upper chromosphere. This study provides heating constraints for the middle and upper chromospheres and additional estimates of the transverse wave power in the chromosphere extending previous work by Molnar et al. (2021).