tooltip: {
        crosshairs: [{
                        dashStyle: 'dash'
                    },{
                       dashStyle: 'dash'     
                    }]
                },
....

    $("#toggleCrossHaire").click(function(){
     if(chart.tooltip.crosshaires){
      chart.tooltip.crosshaires : [false,false];
    }eles{
      chart.tooltip.crosshaires : [true,true];
    }
    });

enable or disable and change dashStyle of Crosshairs . to solid and dash . by an external button??

this example for more explication