Linear stability of resistive interchange modes in a cylindrical Reversed-field pinch plasma

Experimental techniques of current profile control and pellet injection have yielded RFP discharges that are free of current driven instabilities and achieve beta of 26{\%} [1]. Resistive interchange modes are expected to be the dominant instability in these plasmas. Using the NIMROD code, we calculate the linear stability of these modes in a tearing mode stable cylindrical RFP equilibrium for a range of beta. A growth rate spectrum showing the fastest growing modes is obtained. According to linear theory [2], the growth rate of interchange mode is increases with azimuthal mode number, $m$. The result also suggests that all the modes tend to localize around a particular range of rational surfaces with increasing localization for larger $m$. We also present a linear simulation including gyroviscosity to investigate the stabilizing finite Larmor Radius (FLR) effect on interchange modes. In accordance with earlier theoretical work [3] , the suppression of growth rate is observed where \textit{k$\rho $}$_{i }\sim $1. [1] M. D. Wyman et al., Phys. Plasmas 15, 010701 (2008) [2] B. Coppi, J. M. Greene, and J. L. Johnson, Nucl. Fusion 6, 101 (1966) [3] T. E. Stringer, Nucl. Fusion 15, 125 (1975)