Q factors of the Schumann resonances are the factors which represent the sharpness of resonances of the earth ionosphere cavity. The earth as the lower boundary of the cavity can be recognized as a perfect conductor, while the ionosphere as an upper boundary is a leaky wall which has finite conductivities.
“An inverse relation between Q factors and solar activity was found and it is concluded from this that the effective height of the upper boundary of the cavity decreases as the sun becomes active. It is suggested that the sun may have some effect in modifying the conductivity profile below 56 km of the atmosphere.”-from the ScR pdf
I believe these are indicative of the depth of the ELM energy into the earth from the local system and causing quakes.