The 40 deg arc is being shown on maps as the supposed northerly option of the flight path.
NO. the 40 degree arc is the possible position of the aircraft at the time of the "ping" to the satelite. The Aircraft could have been anywhere on that arc(In the red marked areas).
The flight path would have cut through various arcs, the 40 deg one being just one, with the hourly ping being on a different one each time.
Right. But the degree of the three other pings has not been shared(yet).