Abstract

The discovery of ubiquitous low-frequency (3-5 mHz) Alfvénic waves in the solar chromosphere (with Hinode/Solar Optical Telescope) and corona (with CoMP and SDO) has provided some insight into the non-thermal energy content of the outer solar atmosphere. However, many questions remain about the t... Show moreThe discovery of ubiquitous low-frequency (3-5 mHz) Alfvénic waves in the solar chromosphere (with Hinode/Solar Optical Telescope) and corona (with CoMP and SDO) has provided some insight into the non-thermal energy content of the outer solar atmosphere. However, many questions remain about the true magnitude of the energy flux carried by these waves. Here we explore the apparent discrepancy in the resolved coronal Alfvénic wave amplitude (~0.5 km s⁻¹) measured by the Coronal Multi-channel Polarimeter (CoMP) compared to those of the Hinode and the Solar Dynamics Observatory (SDO) near the limb (~20 km s⁻¹). We use a blend of observational data and a simple forward model of Alfvénic wave propagation to resolve this discrepancy and determine the Alfvénic wave energy content of the corona. Our results indicate that enormous line-of-sight superposition within the coarse spatio-temporal sampling of CoMP hides the strong wave flux observed by Hinode and SDO and leads to the large non-thermal line broadening observed. While this scenario has been assumed in the past, our observations with CoMP of a strong correlation between the non-thermal line broadening with the low-amplitude, low-frequency Alfvénic waves observed in the corona provide the first direct evidence of a wave-related non-thermal line broadening. By reconciling the diverse measurements of Alfvénic waves, we establish large coronal non-thermal line widths as direct signatures of the hidden, or "dark," energy content in the corona and provide preliminary constraints on the energy content of the wave motions observed. Show less