Small-scale fluctuations of different tracers of the interstellar the medium can be used to study the nature of turbulence in astrophysical scales .
Of these , the “ continuum ” emission traces the fluctuations integrated along the line of sight whereas , the spectral line tracers give the information along different velocity channels as well .
Recently , Miville-Deschênes et al .
( 29 ) have measured the intensity fluctuation power spectrum of the continuum dust emission , and found a power law behaviour with a power law index of -2.9 \pm 0.1 for a region of our Galaxy .
Here , we study the same region using high-velocity resolution 21-cm emission from the diffuse neutral medium , and estimate the power spectrum at different spectral channels .
The measured 21-cm power spectrum also follows a power law , however , we see a significant variation in the power law index with velocity .
The value of the power-law index estimated from the integrated map for different components are quite different which is indicative of the different nature of turbulence depending on temperature , density and ionization fraction .
We also measure the power spectra after smoothing the 21 cm emission to velocity resolution ranging from 1.03 to 13.39 \leavevmode \nobreak { km \leavevmode \nobreak s ^ { -1 } } , but the power spectrum remains unchanged within the error bar .
This indicates that the observed fluctuations are dominantly due to density fluctuations , and we can only constrain the power-law index of velocity structure function of 0.0 \pm 1.1 which is consistent with the predicted Kolmogorov turbulence ( \gamma = 2 / 3 ) and also with a shock-dominated medium ( \gamma = 1.0 ) .