 Sometimes these may be a simple rising column of air; more often, they are blown sideways in the wind and will break off from the source, with a new thermal forming later.Once a pilot finds a thermal, he begins to fly in a circle, trying to centre the circle on the strongest part of the thermal (the "core"), where the air is rising the fastest.Most pilots use a vario-altimeter ("vario"), which indicates climb rate with beeps and/or a visual display, to help core in on a thermal.