Convection actually means movement. It's the temperatures that cause these convection currents to become stronger and produce wind. Warm air rises, and cool air will drop. They displace each other. Hot air rising rapidly will displace cool air that is dropping more slowly, and cold air will push warm air back up faster than it might move on it's own. The greater the variance of temperature at different altitudes of the stratosphere, the more prominent these air currents become. That's what causes wind.