It has been suggested that the Z-mode instability driven by energetic electrons with a loss-cone type velocity distribution is one candidate process behind the continuum and zebra pattern of solar type-IV radio bursts .
Both the temperature of background plasma ( T _ { 0 } ) and the energy of energetic electrons ( v _ { e } ) are considered to be important to the variation of the maximum growth rate ( \gamma _ { max } ) .
Here we present a detailed parameter study on the effect of T _ { 0 } and v _ { e } , within a regime of the frequency ratio ( 10 \leq \frac { \omega _ { pe } } { \Omega _ { ce } } \leq 30 ) .
In addition to \gamma _ { max } , we also analyze the effect on the corresponding wave frequency ( \omega ^ { r } _ { max } ) and propagation angle ( \theta _ { max } ) .
We find that ( 1 ) \gamma _ { max } in-general decreases with increasing v _ { e } , while its variation with T _ { 0 } is more complex depending on the exact value of v _ { e } ; ( 2 ) with increasing T _ { 0 } and v _ { e } , \omega ^ { r } _ { max } presents step-wise profiles with jumps separated by gradual or very-weak variations , and due to the warm-plasma effect on the wave dispersion relation \omega ^ { r } _ { max } can vary within the hybrid band ( the harmonic band containing the upper hybrid frequency ) and the band higher ; ( 3 ) the propagation is either perpendicular or quasi-perpendicular , and \theta _ { max } presents variations in line with those of \omega ^ { r } _ { max } , as constrained by the resonance condition .
We also examine the profiles of \gamma _ { max } with \frac { \omega _ { pe } } { \Omega _ { ce } } for different combinations of T _ { 0 } and v _ { e } to clarify some earlier calculations which show inconsistent results .