Relation between growth rate of the Suydam mode and that of low mode number interchange instability

Pressure-driven interchange instability of any mode number with the same helicity has the same limiting beta value as that by the Suydam criterion in the cylindrical plasma approximation. Growth rate of the Suydam mode gives an upper boundary of that of the low mode number interchange instability. It is possible that conventional numerical calculations using finite mesh sizes give a higher beta limit by the low mode number interchange instability than the Suydam limit because they fail to find sharply localized modes with small growth rates. (author)