There is an error on page 5 of the original paper,1 in the last equation before Eq. (16), where the factor 5ηi/2 should be replaced by 2ηi+1/2, which is important since a spurious instability otherwise arises for certain values of b. Two factors of b are also missing from the last line of the equation. The corrected equation is

h(ω,l)=Γ0(b)[ 1ω*iω+ω̂diω(1+ηi)ω*iω̂diω2+b(ηiω*iωω̂di2ω+(2ηi+12)ω*iω̂diω2)b2ηiω*iω̂diω2 ]+bΓ1(b)[ ηiω*iω+ω̂di2ω(1ω*iω)(32b)ηiω*iω̂diω2 ].
1.
P.
Helander
,
J. H. E.
Proll
, and
G. G.
Plunk
,
Phys. Plasmas
20
,
122505
(
2013
).