In addition to the major grid built on major ticks, the PolarChart widget provides the minor grid that is built on minor ticks. The lines of the minor grid extend from the minor ticks throughout the entire chart's plot.
To specify the appearance of grid lines, use the options of the minorGrid object. Declared within the commonAxisSettings object, the minorGrid object changes the appearance of value and argument axes simultaneously. To change the appearance of the value or argument axis individually, declare the minorGrid object in the argumentAxis or valueAxis object respectively. Settings specified individually override those that are set in the commonAxisSettings object.
To make the minor grid visible, set the visible option of the minorGrid object to true. Additionally, you can change the color, opacity and width of the grid lines using the corresponding options.