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tokens: repeated for 10 shots. This plot indicates that for increasing bias voltage (which is proportional to the axial magnetic field), the wavelength increases. This phenomenon is consistent with the MRTI theory, since Equation ( 5 ) shows that the increase of magnetic field causes the corresponding fastest-growing wavelength to increase. For a sufficiently large magnetic field, the wavelength is larger than the loop dimensions and the MRTI cannot occur. This is most likely the reason for the absence of the MRTI in previous solar loop simulation experiments where a much larger axial magnetic field was used (e.g., Stenson Bellan 2012 ; Wongwaitayakornkul et al. 2017 ). In Equation ( 5 ), besides B 0 , the other two parameters, ρ , g , also influence the fastest-growing wavelength. In order to remove the influence of these parameters and verify that the increasing wavelength corresponds with the MRTI theory, we introduce the parameter s = λρg . Using Equation ( 5 ), the fastest-growing mode corresponds toTo determine s , the quantities λ and g are obtained from the image measurement, while n is determined as a relative density from the light intensity that scales as n 2 . Keeping other experimental parameters the same, we set V b = 30, 40, 50, 60 V for 10 shots at each voltage to obtain s . Figure 3 (c) shows s plotted versus . The error bars are determined by the shot-to-shot variation of measured data and the line shows the best fit. From this figure, it is clear that s scales as as predicted by Equation ( 10 ). As the geometry of the experiment is more like a cylinder, the experimental results can also be used to compare with the MRTI under cylindrical geometry derived by Zhai Bellan ( 2016 ). Using the notation in Zhai Bellan ( 2016 ), the growth rate iswhere , , , and a is the radius of the cylinder. Consider a system with certain values Φ 2 and α subject to a random perturbation that contains all possible x = ka . The component x that gives the largest is defined as x *, and the fastest growth rate is defined as γ *. Figure 4 (a) shows the dependence of the fastest-growing mode on α for fixed Φ 2 = 3.77. Note that α is proportional to the axial magnetic field and x corresponds to 1/ λ . Figure 4 (a) shows that with the increase of axial magnetic field, the wavelength increases and the growth rate decreases, the same trend as predicted for the MRTI in planar geometry. Figure 4. (a) x * and γ * vs. α with Φ 2 = 3.77. (b)–(f) Comparison between the observed growth rate and the calculated growth rate from the MRTI theory under cylindrical geometry (each data point is from 10 shots and the error bar represents the spread over these shots). We assumed all of the experiments have the same parameters except for axial field with , , I = 10 4 A, , and that the observed mode is the fastest-growing mode. The only free parameter in the determination of Φ 2 is a . From the experimental results, x * can be obtained and the corresponding α and γ * can be