Frankly I would be far more surprised to see a straight line there. For a long phone line the variations in SNRM don't look excessive, and are a long way from risking a dropped connection.
It looks like random interference (i.e. not REIN), so I guess the solar storm is one possible contender, but it could be any one of numerous other possible interference sources. I don't think there's much you can do other than watch and wait.