Observational Study of Reynolds Stresses Associated with Solar Inertial Modes

We study the m = 1 high-latitude inertial mode and its contribution to the latitudinal transport of the Sun's angular momentum. Ring-diagram helioseismology applied to 5° tiles is used to obtain the horizontal flows near the surface of the Sun. Using 10 years of data from SDO/HMI, we report on the horizontal eigenfunction and Reynolds stress $\[{Q_{θ φ }} = \langle {u'_θ }{u'_φ }\rangle \]$ for the m = 1 high-latitude inertial mode (frequency -86.3 nHz, critical latitudes ±58°). We find that Q _θφ takes significant values above the critical latitude and is positive (negative) in the northern (southern) hemisphere, implying equatorward transport of angular momentum. The Q _θφ peaks above latitude 70° with a value of 38 m²/s².